Update Dependencies (#390)

Co-authored-by: Norwin Roosen <git@nroo.de>
Co-authored-by: Norwin <git@nroo.de>
Reviewed-on: https://gitea.com/gitea/tea/pulls/390
Reviewed-by: 6543 <6543@obermui.de>
Reviewed-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: Norwin <noerw@noreply.gitea.io>
Co-committed-by: Norwin <noerw@noreply.gitea.io>

vendor/github.com/ProtonMail/go-crypto/openpgp/packet/aead_config.go

@@ -0,0 +1,56 @@
+// Copyright (C) 2019 ProtonTech AG
+
+package packet
+
+import "math/bits"
+
+// AEADConfig collects a number of AEAD parameters along with sensible defaults.
+// A nil AEADConfig is valid and results in all default values.
+type AEADConfig struct {
+	// The AEAD mode of operation.
+	DefaultMode AEADMode
+	// Amount of octets in each chunk of data
+	ChunkSize uint64
+}
+
+// Mode returns the AEAD mode of operation.
+func (conf *AEADConfig) Mode() AEADMode {
+	if conf == nil || conf.DefaultMode == 0 {
+		return AEADModeEAX
+	}
+	mode := conf.DefaultMode
+	if mode != AEADModeEAX && mode != AEADModeOCB &&
+		mode != AEADModeExperimentalGCM {
+		panic("AEAD mode unsupported")
+	}
+	return mode
+}
+
+// ChunkSizeByte returns the byte indicating the chunk size. The effective
+// chunk size is computed with the formula uint64(1) << (chunkSizeByte + 6)
+func (conf *AEADConfig) ChunkSizeByte() byte {
+	if conf == nil || conf.ChunkSize == 0 {
+		return 12 // 1 << (12 + 6) == 262144 bytes
+	}
+
+	chunkSize := conf.ChunkSize
+	exponent := bits.Len64(chunkSize) - 1
+	switch {
+	case exponent < 6:
+		exponent = 6
+	case exponent > 27:
+		exponent = 27
+	}
+
+	return byte(exponent - 6)
+}
+
+// decodeAEADChunkSize returns the effective chunk size. In 32-bit systems, the
+// maximum returned value is 1 << 30.
+func decodeAEADChunkSize(c byte) int {
+	size := uint64(1 << (c + 6))
+	if size != uint64(int(size)) {
+		return 1 << 30
+	}
+	return int(size)
+}

vendor/github.com/ProtonMail/go-crypto/openpgp/packet/aead_encrypted.go

@@ -0,0 +1,364 @@
+// Copyright (C) 2019 ProtonTech AG
+
+package packet
+
+import (
+	"bytes"
+	"crypto/cipher"
+	"crypto/rand"
+	"encoding/binary"
+	"io"
+
+	"github.com/ProtonMail/go-crypto/openpgp/errors"
+	"github.com/ProtonMail/go-crypto/openpgp/internal/algorithm"
+)
+
+// AEADEncrypted represents an AEAD Encrypted Packet (tag 20, RFC4880bis-5.16).
+type AEADEncrypted struct {
+	cipher        CipherFunction
+	mode          AEADMode
+	chunkSizeByte byte
+	Contents      io.Reader // Encrypted chunks and tags
+	initialNonce  []byte    // Referred to as IV in RFC4880-bis
+}
+
+// Only currently defined version
+const aeadEncryptedVersion = 1
+
+// An AEAD opener/sealer, its configuration, and data for en/decryption.
+type aeadCrypter struct {
+	aead           cipher.AEAD
+	chunkSize      int
+	initialNonce   []byte
+	associatedData []byte       // Chunk-independent associated data
+	chunkIndex     []byte       // Chunk counter
+	bytesProcessed int          // Amount of plaintext bytes encrypted/decrypted
+	buffer         bytes.Buffer // Buffered bytes accross chunks
+}
+
+// aeadEncrypter encrypts and writes bytes. It encrypts when necessary according
+// to the AEAD block size, and buffers the extra encrypted bytes for next write.
+type aeadEncrypter struct {
+	aeadCrypter                // Embedded plaintext sealer
+	writer      io.WriteCloser // 'writer' is a partialLengthWriter
+}
+
+// aeadDecrypter reads and decrypts bytes. It buffers extra decrypted bytes when
+// necessary, similar to aeadEncrypter.
+type aeadDecrypter struct {
+	aeadCrypter           // Embedded ciphertext opener
+	reader      io.Reader // 'reader' is a partialLengthReader
+	peekedBytes []byte    // Used to detect last chunk
+	eof         bool
+}
+
+func (ae *AEADEncrypted) parse(buf io.Reader) error {
+	headerData := make([]byte, 4)
+	if n, err := io.ReadFull(buf, headerData); n < 4 {
+		return errors.AEADError("could not read aead header:" + err.Error())
+	}
+	// Read initial nonce
+	mode := AEADMode(headerData[2])
+	nonceLen := mode.NonceLength()
+	if nonceLen == 0 {
+		return errors.AEADError("unknown mode")
+	}
+	initialNonce := make([]byte, nonceLen)
+	if n, err := io.ReadFull(buf, initialNonce); n < nonceLen {
+		return errors.AEADError("could not read aead nonce:" + err.Error())
+	}
+	ae.Contents = buf
+	ae.initialNonce = initialNonce
+	c := headerData[1]
+	if _, ok := algorithm.CipherById[c]; !ok {
+		return errors.UnsupportedError("unknown cipher: " + string(c))
+	}
+	ae.cipher = CipherFunction(c)
+	ae.mode = mode
+	ae.chunkSizeByte = byte(headerData[3])
+	return nil
+}
+
+// Decrypt returns a io.ReadCloser from which decrypted bytes can be read, or
+// an error.
+func (ae *AEADEncrypted) Decrypt(ciph CipherFunction, key []byte) (io.ReadCloser, error) {
+	return ae.decrypt(key)
+}
+
+// decrypt prepares an aeadCrypter and returns a ReadCloser from which
+// decrypted bytes can be read (see aeadDecrypter.Read()).
+func (ae *AEADEncrypted) decrypt(key []byte) (io.ReadCloser, error) {
+	blockCipher := ae.cipher.new(key)
+	aead := ae.mode.new(blockCipher)
+	// Carry the first tagLen bytes
+	tagLen := ae.mode.TagLength()
+	peekedBytes := make([]byte, tagLen)
+	n, err := io.ReadFull(ae.Contents, peekedBytes)
+	if n < tagLen || (err != nil && err != io.EOF) {
+		return nil, errors.AEADError("Not enough data to decrypt:" + err.Error())
+	}
+	chunkSize := decodeAEADChunkSize(ae.chunkSizeByte)
+	return &aeadDecrypter{
+		aeadCrypter: aeadCrypter{
+			aead:           aead,
+			chunkSize:      chunkSize,
+			initialNonce:   ae.initialNonce,
+			associatedData: ae.associatedData(),
+			chunkIndex:     make([]byte, 8),
+		},
+		reader:      ae.Contents,
+		peekedBytes: peekedBytes}, nil
+}
+
+// Read decrypts bytes and reads them into dst. It decrypts when necessary and
+// buffers extra decrypted bytes. It returns the number of bytes copied into dst
+// and an error.
+func (ar *aeadDecrypter) Read(dst []byte) (n int, err error) {
+	// Return buffered plaintext bytes from previous calls
+	if ar.buffer.Len() > 0 {
+		return ar.buffer.Read(dst)
+	}
+
+	// Return EOF if we've previously validated the final tag
+	if ar.eof {
+		return 0, io.EOF
+	}
+
+	// Read a chunk
+	tagLen := ar.aead.Overhead()
+	cipherChunkBuf := new(bytes.Buffer)
+	_, errRead := io.CopyN(cipherChunkBuf, ar.reader, int64(ar.chunkSize + tagLen))
+	cipherChunk := cipherChunkBuf.Bytes()
+	if errRead != nil && errRead != io.EOF {
+		return 0, errRead
+	}
+	decrypted, errChunk := ar.openChunk(cipherChunk)
+	if errChunk != nil {
+		return 0, errChunk
+	}
+
+	// Return decrypted bytes, buffering if necessary
+	if len(dst) < len(decrypted) {
+		n = copy(dst, decrypted[:len(dst)])
+		ar.buffer.Write(decrypted[len(dst):])
+	} else {
+		n = copy(dst, decrypted)
+	}
+
+	// Check final authentication tag
+	if errRead == io.EOF {
+		errChunk := ar.validateFinalTag(ar.peekedBytes)
+		if errChunk != nil {
+			return n, errChunk
+		}
+		ar.eof = true // Mark EOF for when we've returned all buffered data
+	}
+	return
+}
+
+// Close is noOp. The final authentication tag of the stream was already
+// checked in the last Read call. In the future, this function could be used to
+// wipe the reader and peeked, decrypted bytes, if necessary.
+func (ar *aeadDecrypter) Close() (err error) {
+	return nil
+}
+
+// SerializeAEADEncrypted initializes the aeadCrypter and returns a writer.
+// This writer encrypts and writes bytes (see aeadEncrypter.Write()).
+func SerializeAEADEncrypted(w io.Writer, key []byte, cipher CipherFunction, mode AEADMode, config *Config) (io.WriteCloser, error) {
+	writeCloser := noOpCloser{w}
+	writer, err := serializeStreamHeader(writeCloser, packetTypeAEADEncrypted)
+	if err != nil {
+		return nil, err
+	}
+
+	// Data for en/decryption: tag, version, cipher, aead mode, chunk size
+	aeadConf := config.AEAD()
+	prefix := []byte{
+		0xD4,
+		aeadEncryptedVersion,
+		byte(config.Cipher()),
+		byte(aeadConf.Mode()),
+		aeadConf.ChunkSizeByte(),
+	}
+	n, err := writer.Write(prefix[1:])
+	if err != nil || n < 4 {
+		return nil, errors.AEADError("could not write AEAD headers")
+	}
+	// Sample nonce
+	nonceLen := aeadConf.Mode().NonceLength()
+	nonce := make([]byte, nonceLen)
+	n, err = rand.Read(nonce)
+	if err != nil {
+		panic("Could not sample random nonce")
+	}
+	_, err = writer.Write(nonce)
+	if err != nil {
+		return nil, err
+	}
+	blockCipher := CipherFunction(config.Cipher()).new(key)
+	alg := AEADMode(aeadConf.Mode()).new(blockCipher)
+
+	chunkSize := decodeAEADChunkSize(aeadConf.ChunkSizeByte())
+	return &aeadEncrypter{
+		aeadCrypter: aeadCrypter{
+			aead:           alg,
+			chunkSize:      chunkSize,
+			associatedData: prefix,
+			chunkIndex:     make([]byte, 8),
+			initialNonce:   nonce,
+		},
+		writer: writer}, nil
+}
+
+// Write encrypts and writes bytes. It encrypts when necessary and buffers extra
+// plaintext bytes for next call. When the stream is finished, Close() MUST be
+// called to append the final tag.
+func (aw *aeadEncrypter) Write(plaintextBytes []byte) (n int, err error) {
+	// Append plaintextBytes to existing buffered bytes
+	n, err = aw.buffer.Write(plaintextBytes)
+	if err != nil {
+		return n, err
+	}
+	// Encrypt and write chunks
+	for aw.buffer.Len() >= aw.chunkSize {
+		plainChunk := aw.buffer.Next(aw.chunkSize)
+		encryptedChunk, err := aw.sealChunk(plainChunk)
+		if err != nil {
+			return n, err
+		}
+		_, err = aw.writer.Write(encryptedChunk)
+		if err != nil {
+			return n, err
+		}
+	}
+	return
+}
+
+// Close encrypts and writes the remaining buffered plaintext if any, appends
+// the final authentication tag, and closes the embedded writer. This function
+// MUST be called at the end of a stream.
+func (aw *aeadEncrypter) Close() (err error) {
+	// Encrypt and write a chunk if there's buffered data left, or if we haven't
+	// written any chunks yet.
+	if aw.buffer.Len() > 0 || aw.bytesProcessed == 0 {
+		plainChunk := aw.buffer.Bytes()
+		lastEncryptedChunk, err := aw.sealChunk(plainChunk)
+		if err != nil {
+			return err
+		}
+		_, err = aw.writer.Write(lastEncryptedChunk)
+		if err != nil {
+			return err
+		}
+	}
+	// Compute final tag (associated data: packet tag, version, cipher, aead,
+	// chunk size, index, total number of encrypted octets).
+	adata := append(aw.associatedData[:], aw.chunkIndex[:]...)
+	adata = append(adata, make([]byte, 8)...)
+	binary.BigEndian.PutUint64(adata[13:], uint64(aw.bytesProcessed))
+	nonce := aw.computeNextNonce()
+	finalTag := aw.aead.Seal(nil, nonce, nil, adata)
+	_, err = aw.writer.Write(finalTag)
+	if err != nil {
+		return err
+	}
+	return aw.writer.Close()
+}
+
+// sealChunk Encrypts and authenticates the given chunk.
+func (aw *aeadEncrypter) sealChunk(data []byte) ([]byte, error) {
+	if len(data) > aw.chunkSize {
+		return nil, errors.AEADError("chunk exceeds maximum length")
+	}
+	if aw.associatedData == nil {
+		return nil, errors.AEADError("can't seal without headers")
+	}
+	adata := append(aw.associatedData, aw.chunkIndex...)
+	nonce := aw.computeNextNonce()
+	encrypted := aw.aead.Seal(nil, nonce, data, adata)
+	aw.bytesProcessed += len(data)
+	if err := aw.aeadCrypter.incrementIndex(); err != nil {
+		return nil, err
+	}
+	return encrypted, nil
+}
+
+// openChunk decrypts and checks integrity of an encrypted chunk, returning
+// the underlying plaintext and an error. It access peeked bytes from next
+// chunk, to identify the last chunk and decrypt/validate accordingly.
+func (ar *aeadDecrypter) openChunk(data []byte) ([]byte, error) {
+	tagLen := ar.aead.Overhead()
+	// Restore carried bytes from last call
+	chunkExtra := append(ar.peekedBytes, data...)
+	// 'chunk' contains encrypted bytes, followed by an authentication tag.
+	chunk := chunkExtra[:len(chunkExtra)-tagLen]
+	ar.peekedBytes = chunkExtra[len(chunkExtra)-tagLen:]
+	adata := append(ar.associatedData, ar.chunkIndex...)
+	nonce := ar.computeNextNonce()
+	plainChunk, err := ar.aead.Open(nil, nonce, chunk, adata)
+	if err != nil {
+		return nil, err
+	}
+	ar.bytesProcessed += len(plainChunk)
+	if err = ar.aeadCrypter.incrementIndex(); err != nil {
+		return nil, err
+	}
+	return plainChunk, nil
+}
+
+// Checks the summary tag. It takes into account the total decrypted bytes into
+// the associated data. It returns an error, or nil if the tag is valid.
+func (ar *aeadDecrypter) validateFinalTag(tag []byte) error {
+	// Associated: tag, version, cipher, aead, chunk size, index, and octets
+	amountBytes := make([]byte, 8)
+	binary.BigEndian.PutUint64(amountBytes, uint64(ar.bytesProcessed))
+	adata := append(ar.associatedData, ar.chunkIndex...)
+	adata = append(adata, amountBytes...)
+	nonce := ar.computeNextNonce()
+	_, err := ar.aead.Open(nil, nonce, tag, adata)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+// Associated data for chunks: tag, version, cipher, mode, chunk size byte
+func (ae *AEADEncrypted) associatedData() []byte {
+	return []byte{
+		0xD4,
+		aeadEncryptedVersion,
+		byte(ae.cipher),
+		byte(ae.mode),
+		ae.chunkSizeByte}
+}
+
+// computeNonce takes the incremental index and computes an eXclusive OR with
+// the least significant 8 bytes of the receivers' initial nonce (see sec.
+// 5.16.1 and 5.16.2). It returns the resulting nonce.
+func (wo *aeadCrypter) computeNextNonce() (nonce []byte) {
+	nonce = make([]byte, len(wo.initialNonce))
+	copy(nonce, wo.initialNonce)
+	offset := len(wo.initialNonce) - 8
+	for i := 0; i < 8; i++ {
+		nonce[i+offset] ^= wo.chunkIndex[i]
+	}
+	return
+}
+
+// incrementIndex perfoms an integer increment by 1 of the integer represented by the
+// slice, modifying it accordingly.
+func (wo *aeadCrypter) incrementIndex() error {
+	index := wo.chunkIndex
+	if len(index) == 0 {
+		return errors.AEADError("Index has length 0")
+	}
+	for i := len(index) - 1; i >= 0; i-- {
+		if index[i] < 255 {
+			index[i]++
+			return nil
+		}
+		index[i] = 0
+	}
+	return errors.AEADError("cannot further increment index")
+}

vendor/github.com/ProtonMail/go-crypto/openpgp/packet/compressed.go

@@ -0,0 +1,123 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"compress/bzip2"
+	"compress/flate"
+	"compress/zlib"
+	"github.com/ProtonMail/go-crypto/openpgp/errors"
+	"io"
+	"strconv"
+)
+
+// Compressed represents a compressed OpenPGP packet. The decompressed contents
+// will contain more OpenPGP packets. See RFC 4880, section 5.6.
+type Compressed struct {
+	Body io.Reader
+}
+
+const (
+	NoCompression      = flate.NoCompression
+	BestSpeed          = flate.BestSpeed
+	BestCompression    = flate.BestCompression
+	DefaultCompression = flate.DefaultCompression
+)
+
+// CompressionConfig contains compressor configuration settings.
+type CompressionConfig struct {
+	// Level is the compression level to use. It must be set to
+	// between -1 and 9, with -1 causing the compressor to use the
+	// default compression level, 0 causing the compressor to use
+	// no compression and 1 to 9 representing increasing (better,
+	// slower) compression levels. If Level is less than -1 or
+	// more then 9, a non-nil error will be returned during
+	// encryption. See the constants above for convenient common
+	// settings for Level.
+	Level int
+}
+
+func (c *Compressed) parse(r io.Reader) error {
+	var buf [1]byte
+	_, err := readFull(r, buf[:])
+	if err != nil {
+		return err
+	}
+
+	switch buf[0] {
+	case 1:
+		c.Body = flate.NewReader(r)
+	case 2:
+		c.Body, err = zlib.NewReader(r)
+	case 3:
+		c.Body = bzip2.NewReader(r)
+	default:
+		err = errors.UnsupportedError("unknown compression algorithm: " + strconv.Itoa(int(buf[0])))
+	}
+
+	return err
+}
+
+// compressedWriterCloser represents the serialized compression stream
+// header and the compressor. Its Close() method ensures that both the
+// compressor and serialized stream header are closed. Its Write()
+// method writes to the compressor.
+type compressedWriteCloser struct {
+	sh io.Closer      // Stream Header
+	c  io.WriteCloser // Compressor
+}
+
+func (cwc compressedWriteCloser) Write(p []byte) (int, error) {
+	return cwc.c.Write(p)
+}
+
+func (cwc compressedWriteCloser) Close() (err error) {
+	err = cwc.c.Close()
+	if err != nil {
+		return err
+	}
+
+	return cwc.sh.Close()
+}
+
+// SerializeCompressed serializes a compressed data packet to w and
+// returns a WriteCloser to which the literal data packets themselves
+// can be written and which MUST be closed on completion. If cc is
+// nil, sensible defaults will be used to configure the compression
+// algorithm.
+func SerializeCompressed(w io.WriteCloser, algo CompressionAlgo, cc *CompressionConfig) (literaldata io.WriteCloser, err error) {
+	compressed, err := serializeStreamHeader(w, packetTypeCompressed)
+	if err != nil {
+		return
+	}
+
+	_, err = compressed.Write([]byte{uint8(algo)})
+	if err != nil {
+		return
+	}
+
+	level := DefaultCompression
+	if cc != nil {
+		level = cc.Level
+	}
+
+	var compressor io.WriteCloser
+	switch algo {
+	case CompressionZIP:
+		compressor, err = flate.NewWriter(compressed, level)
+	case CompressionZLIB:
+		compressor, err = zlib.NewWriterLevel(compressed, level)
+	default:
+		s := strconv.Itoa(int(algo))
+		err = errors.UnsupportedError("Unsupported compression algorithm: " + s)
+	}
+	if err != nil {
+		return
+	}
+
+	literaldata = compressedWriteCloser{compressed, compressor}
+
+	return
+}

vendor/github.com/ProtonMail/go-crypto/openpgp/packet/config.go

@@ -0,0 +1,167 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"crypto"
+	"crypto/rand"
+	"io"
+	"math/big"
+	"time"
+)
+
+// Config collects a number of parameters along with sensible defaults.
+// A nil *Config is valid and results in all default values.
+type Config struct {
+	// Rand provides the source of entropy.
+	// If nil, the crypto/rand Reader is used.
+	Rand io.Reader
+	// DefaultHash is the default hash function to be used.
+	// If zero, SHA-256 is used.
+	DefaultHash crypto.Hash
+	// DefaultCipher is the cipher to be used.
+	// If zero, AES-128 is used.
+	DefaultCipher CipherFunction
+	// Time returns the current time as the number of seconds since the
+	// epoch. If Time is nil, time.Now is used.
+	Time func() time.Time
+	// DefaultCompressionAlgo is the compression algorithm to be
+	// applied to the plaintext before encryption. If zero, no
+	// compression is done.
+	DefaultCompressionAlgo CompressionAlgo
+	// CompressionConfig configures the compression settings.
+	CompressionConfig *CompressionConfig
+	// S2KCount is only used for symmetric encryption. It
+	// determines the strength of the passphrase stretching when
+	// the said passphrase is hashed to produce a key. S2KCount
+	// should be between 1024 and 65011712, inclusive. If Config
+	// is nil or S2KCount is 0, the value 65536 used. Not all
+	// values in the above range can be represented. S2KCount will
+	// be rounded up to the next representable value if it cannot
+	// be encoded exactly. When set, it is strongly encrouraged to
+	// use a value that is at least 65536. See RFC 4880 Section
+	// 3.7.1.3.
+	S2KCount int
+	// RSABits is the number of bits in new RSA keys made with NewEntity.
+	// If zero, then 2048 bit keys are created.
+	RSABits int
+	// The public key algorithm to use - will always create a signing primary
+	// key and encryption subkey.
+	Algorithm PublicKeyAlgorithm
+	// Some known primes that are optionally prepopulated by the caller
+	RSAPrimes []*big.Int
+	// AEADConfig configures the use of the new AEAD Encrypted Data Packet,
+	// defined in the draft of the next version of the OpenPGP specification.
+	// If a non-nil AEADConfig is passed, usage of this packet is enabled. By
+	// default, it is disabled. See the documentation of AEADConfig for more
+	// configuration options related to AEAD.
+	// **Note: using this option may break compatibility with other OpenPGP
+	// implementations, as well as future versions of this library.**
+	AEADConfig *AEADConfig
+	// V5Keys configures version 5 key generation. If false, this package still
+	// supports version 5 keys, but produces version 4 keys.
+	V5Keys bool
+	// "The validity period of the key.  This is the number of seconds after
+	// the key creation time that the key expires.  If this is not present
+	// or has a value of zero, the key never expires.  This is found only on
+	// a self-signature.""
+	// https://tools.ietf.org/html/rfc4880#section-5.2.3.6
+	KeyLifetimeSecs uint32
+	// "The validity period of the signature.  This is the number of seconds
+	// after the signature creation time that the signature expires.  If
+	// this is not present or has a value of zero, it never expires."
+	// https://tools.ietf.org/html/rfc4880#section-5.2.3.10
+	SigLifetimeSecs uint32
+	// SigningKeyId is used to specify the signing key to use (by Key ID).
+	// By default, the signing key is selected automatically, preferring
+	// signing subkeys if available.
+	SigningKeyId uint64
+}
+
+func (c *Config) Random() io.Reader {
+	if c == nil || c.Rand == nil {
+		return rand.Reader
+	}
+	return c.Rand
+}
+
+func (c *Config) Hash() crypto.Hash {
+	if c == nil || uint(c.DefaultHash) == 0 {
+		return crypto.SHA256
+	}
+	return c.DefaultHash
+}
+
+func (c *Config) Cipher() CipherFunction {
+	if c == nil || uint8(c.DefaultCipher) == 0 {
+		return CipherAES128
+	}
+	return c.DefaultCipher
+}
+
+func (c *Config) Now() time.Time {
+	if c == nil || c.Time == nil {
+		return time.Now()
+	}
+	return c.Time()
+}
+
+// KeyLifetime returns the validity period of the key.
+func (c *Config) KeyLifetime() uint32 {
+	if c == nil {
+		return 0
+	}
+	return c.KeyLifetimeSecs
+}
+
+// SigLifetime returns the validity period of the signature.
+func (c *Config) SigLifetime() uint32 {
+	if c == nil {
+		return 0
+	}
+	return c.SigLifetimeSecs
+}
+
+func (c *Config) Compression() CompressionAlgo {
+	if c == nil {
+		return CompressionNone
+	}
+	return c.DefaultCompressionAlgo
+}
+
+func (c *Config) PasswordHashIterations() int {
+	if c == nil || c.S2KCount == 0 {
+		return 0
+	}
+	return c.S2KCount
+}
+
+func (c *Config) RSAModulusBits() int {
+	if c == nil || c.RSABits == 0 {
+		return 2048
+	}
+	return c.RSABits
+}
+
+func (c *Config) PublicKeyAlgorithm() PublicKeyAlgorithm {
+	if c == nil || c.Algorithm == 0 {
+		return PubKeyAlgoRSA
+	}
+	return c.Algorithm
+}
+
+func (c *Config) AEAD() *AEADConfig {
+	if c == nil {
+		return nil
+	}
+	return c.AEADConfig
+}
+
+func (c *Config) SigningKey() uint64 {
+	if c == nil {
+		return 0
+	}
+	return c.SigningKeyId
+}

vendor/github.com/ProtonMail/go-crypto/openpgp/packet/encrypted_key.go

@@ -0,0 +1,282 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"crypto"
+	"crypto/rsa"
+	"encoding/binary"
+	"io"
+	"math/big"
+	"strconv"
+
+	"github.com/ProtonMail/go-crypto/openpgp/ecdh"
+	"github.com/ProtonMail/go-crypto/openpgp/elgamal"
+	"github.com/ProtonMail/go-crypto/openpgp/errors"
+	"github.com/ProtonMail/go-crypto/openpgp/internal/encoding"
+)
+
+const encryptedKeyVersion = 3
+
+// EncryptedKey represents a public-key encrypted session key. See RFC 4880,
+// section 5.1.
+type EncryptedKey struct {
+	KeyId      uint64
+	Algo       PublicKeyAlgorithm
+	CipherFunc CipherFunction // only valid after a successful Decrypt
+	Key        []byte         // only valid after a successful Decrypt
+
+	encryptedMPI1, encryptedMPI2 encoding.Field
+}
+
+func (e *EncryptedKey) parse(r io.Reader) (err error) {
+	var buf [10]byte
+	_, err = readFull(r, buf[:])
+	if err != nil {
+		return
+	}
+	if buf[0] != encryptedKeyVersion {
+		return errors.UnsupportedError("unknown EncryptedKey version " + strconv.Itoa(int(buf[0])))
+	}
+	e.KeyId = binary.BigEndian.Uint64(buf[1:9])
+	e.Algo = PublicKeyAlgorithm(buf[9])
+	switch e.Algo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly:
+		e.encryptedMPI1 = new(encoding.MPI)
+		if _, err = e.encryptedMPI1.ReadFrom(r); err != nil {
+			return
+		}
+	case PubKeyAlgoElGamal:
+		e.encryptedMPI1 = new(encoding.MPI)
+		if _, err = e.encryptedMPI1.ReadFrom(r); err != nil {
+			return
+		}
+
+		e.encryptedMPI2 = new(encoding.MPI)
+		if _, err = e.encryptedMPI2.ReadFrom(r); err != nil {
+			return
+		}
+	case PubKeyAlgoECDH:
+		e.encryptedMPI1 = new(encoding.MPI)
+		if _, err = e.encryptedMPI1.ReadFrom(r); err != nil {
+			return
+		}
+
+		e.encryptedMPI2 = new(encoding.OID)
+		if _, err = e.encryptedMPI2.ReadFrom(r); err != nil {
+			return
+		}
+	}
+	_, err = consumeAll(r)
+	return
+}
+
+func checksumKeyMaterial(key []byte) uint16 {
+	var checksum uint16
+	for _, v := range key {
+		checksum += uint16(v)
+	}
+	return checksum
+}
+
+// Decrypt decrypts an encrypted session key with the given private key. The
+// private key must have been decrypted first.
+// If config is nil, sensible defaults will be used.
+func (e *EncryptedKey) Decrypt(priv *PrivateKey, config *Config) error {
+	if e.KeyId != 0 && e.KeyId != priv.KeyId {
+		return errors.InvalidArgumentError("cannot decrypt encrypted session key for key id " + strconv.FormatUint(e.KeyId, 16) + " with private key id " + strconv.FormatUint(priv.KeyId, 16))
+	}
+	if e.Algo != priv.PubKeyAlgo {
+		return errors.InvalidArgumentError("cannot decrypt encrypted session key of type " + strconv.Itoa(int(e.Algo)) + " with private key of type " + strconv.Itoa(int(priv.PubKeyAlgo)))
+	}
+	if priv.Dummy() {
+		return errors.ErrDummyPrivateKey("dummy key found")
+	}
+
+	var err error
+	var b []byte
+
+	// TODO(agl): use session key decryption routines here to avoid
+	// padding oracle attacks.
+	switch priv.PubKeyAlgo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly:
+		// Supports both *rsa.PrivateKey and crypto.Decrypter
+		k := priv.PrivateKey.(crypto.Decrypter)
+		b, err = k.Decrypt(config.Random(), padToKeySize(k.Public().(*rsa.PublicKey), e.encryptedMPI1.Bytes()), nil)
+	case PubKeyAlgoElGamal:
+		c1 := new(big.Int).SetBytes(e.encryptedMPI1.Bytes())
+		c2 := new(big.Int).SetBytes(e.encryptedMPI2.Bytes())
+		b, err = elgamal.Decrypt(priv.PrivateKey.(*elgamal.PrivateKey), c1, c2)
+	case PubKeyAlgoECDH:
+		vsG := e.encryptedMPI1.Bytes()
+		m := e.encryptedMPI2.Bytes()
+		oid := priv.PublicKey.oid.EncodedBytes()
+		b, err = ecdh.Decrypt(priv.PrivateKey.(*ecdh.PrivateKey), vsG, m, oid, priv.PublicKey.Fingerprint[:])
+	default:
+		err = errors.InvalidArgumentError("cannot decrypt encrypted session key with private key of type " + strconv.Itoa(int(priv.PubKeyAlgo)))
+	}
+
+	if err != nil {
+		return err
+	}
+
+	e.CipherFunc = CipherFunction(b[0])
+	e.Key = b[1 : len(b)-2]
+	expectedChecksum := uint16(b[len(b)-2])<<8 | uint16(b[len(b)-1])
+	checksum := checksumKeyMaterial(e.Key)
+	if checksum != expectedChecksum {
+		return errors.StructuralError("EncryptedKey checksum incorrect")
+	}
+
+	return nil
+}
+
+// Serialize writes the encrypted key packet, e, to w.
+func (e *EncryptedKey) Serialize(w io.Writer) error {
+	var mpiLen int
+	switch e.Algo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly:
+		mpiLen = int(e.encryptedMPI1.EncodedLength())
+	case PubKeyAlgoElGamal:
+		mpiLen = int(e.encryptedMPI1.EncodedLength()) + int(e.encryptedMPI2.EncodedLength())
+	case PubKeyAlgoECDH:
+		mpiLen = int(e.encryptedMPI1.EncodedLength()) + int(e.encryptedMPI2.EncodedLength())
+	default:
+		return errors.InvalidArgumentError("don't know how to serialize encrypted key type " + strconv.Itoa(int(e.Algo)))
+	}
+
+	err := serializeHeader(w, packetTypeEncryptedKey, 1 /* version */ +8 /* key id */ +1 /* algo */ +mpiLen)
+	if err != nil {
+		return err
+	}
+
+	w.Write([]byte{encryptedKeyVersion})
+	binary.Write(w, binary.BigEndian, e.KeyId)
+	w.Write([]byte{byte(e.Algo)})
+
+	switch e.Algo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly:
+		_, err := w.Write(e.encryptedMPI1.EncodedBytes())
+		return err
+	case PubKeyAlgoElGamal:
+		if _, err := w.Write(e.encryptedMPI1.EncodedBytes()); err != nil {
+			return err
+		}
+		_, err := w.Write(e.encryptedMPI2.EncodedBytes())
+		return err
+	case PubKeyAlgoECDH:
+		if _, err := w.Write(e.encryptedMPI1.EncodedBytes()); err != nil {
+			return err
+		}
+		_, err := w.Write(e.encryptedMPI2.EncodedBytes())
+		return err
+	default:
+		panic("internal error")
+	}
+}
+
+// SerializeEncryptedKey serializes an encrypted key packet to w that contains
+// key, encrypted to pub.
+// If config is nil, sensible defaults will be used.
+func SerializeEncryptedKey(w io.Writer, pub *PublicKey, cipherFunc CipherFunction, key []byte, config *Config) error {
+	var buf [10]byte
+	buf[0] = encryptedKeyVersion
+	binary.BigEndian.PutUint64(buf[1:9], pub.KeyId)
+	buf[9] = byte(pub.PubKeyAlgo)
+
+	keyBlock := make([]byte, 1 /* cipher type */ +len(key)+2 /* checksum */)
+	keyBlock[0] = byte(cipherFunc)
+	copy(keyBlock[1:], key)
+	checksum := checksumKeyMaterial(key)
+	keyBlock[1+len(key)] = byte(checksum >> 8)
+	keyBlock[1+len(key)+1] = byte(checksum)
+
+	switch pub.PubKeyAlgo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly:
+		return serializeEncryptedKeyRSA(w, config.Random(), buf, pub.PublicKey.(*rsa.PublicKey), keyBlock)
+	case PubKeyAlgoElGamal:
+		return serializeEncryptedKeyElGamal(w, config.Random(), buf, pub.PublicKey.(*elgamal.PublicKey), keyBlock)
+	case PubKeyAlgoECDH:
+		return serializeEncryptedKeyECDH(w, config.Random(), buf, pub.PublicKey.(*ecdh.PublicKey), keyBlock, pub.oid, pub.Fingerprint)
+	case PubKeyAlgoDSA, PubKeyAlgoRSASignOnly:
+		return errors.InvalidArgumentError("cannot encrypt to public key of type " + strconv.Itoa(int(pub.PubKeyAlgo)))
+	}
+
+	return errors.UnsupportedError("encrypting a key to public key of type " + strconv.Itoa(int(pub.PubKeyAlgo)))
+}
+
+func serializeEncryptedKeyRSA(w io.Writer, rand io.Reader, header [10]byte, pub *rsa.PublicKey, keyBlock []byte) error {
+	cipherText, err := rsa.EncryptPKCS1v15(rand, pub, keyBlock)
+	if err != nil {
+		return errors.InvalidArgumentError("RSA encryption failed: " + err.Error())
+	}
+
+	cipherMPI := encoding.NewMPI(cipherText)
+	packetLen := 10 /* header length */ + int(cipherMPI.EncodedLength())
+
+	err = serializeHeader(w, packetTypeEncryptedKey, packetLen)
+	if err != nil {
+		return err
+	}
+	_, err = w.Write(header[:])
+	if err != nil {
+		return err
+	}
+	_, err = w.Write(cipherMPI.EncodedBytes())
+	return err
+}
+
+func serializeEncryptedKeyElGamal(w io.Writer, rand io.Reader, header [10]byte, pub *elgamal.PublicKey, keyBlock []byte) error {
+	c1, c2, err := elgamal.Encrypt(rand, pub, keyBlock)
+	if err != nil {
+		return errors.InvalidArgumentError("ElGamal encryption failed: " + err.Error())
+	}
+
+	packetLen := 10 /* header length */
+	packetLen += 2 /* mpi size */ + (c1.BitLen()+7)/8
+	packetLen += 2 /* mpi size */ + (c2.BitLen()+7)/8
+
+	err = serializeHeader(w, packetTypeEncryptedKey, packetLen)
+	if err != nil {
+		return err
+	}
+	_, err = w.Write(header[:])
+	if err != nil {
+		return err
+	}
+	if _, err = w.Write(new(encoding.MPI).SetBig(c1).EncodedBytes()); err != nil {
+		return err
+	}
+	_, err = w.Write(new(encoding.MPI).SetBig(c2).EncodedBytes())
+	return err
+}
+
+func serializeEncryptedKeyECDH(w io.Writer, rand io.Reader, header [10]byte, pub *ecdh.PublicKey, keyBlock []byte, oid encoding.Field, fingerprint []byte) error {
+	vsG, c, err := ecdh.Encrypt(rand, pub, keyBlock, oid.EncodedBytes(), fingerprint)
+	if err != nil {
+		return errors.InvalidArgumentError("ECDH encryption failed: " + err.Error())
+	}
+
+	g := encoding.NewMPI(vsG)
+	m := encoding.NewOID(c)
+
+	packetLen := 10 /* header length */
+	packetLen += int(g.EncodedLength()) + int(m.EncodedLength())
+
+	err = serializeHeader(w, packetTypeEncryptedKey, packetLen)
+	if err != nil {
+		return err
+	}
+
+	_, err = w.Write(header[:])
+	if err != nil {
+		return err
+	}
+	if _, err = w.Write(g.EncodedBytes()); err != nil {
+		return err
+	}
+	_, err = w.Write(m.EncodedBytes())
+	return err
+}

vendor/github.com/ProtonMail/go-crypto/openpgp/packet/literal.go

@@ -0,0 +1,91 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"encoding/binary"
+	"io"
+)
+
+// LiteralData represents an encrypted file. See RFC 4880, section 5.9.
+type LiteralData struct {
+	Format   uint8
+	IsBinary bool
+	FileName string
+	Time     uint32 // Unix epoch time. Either creation time or modification time. 0 means undefined.
+	Body     io.Reader
+}
+
+// ForEyesOnly returns whether the contents of the LiteralData have been marked
+// as especially sensitive.
+func (l *LiteralData) ForEyesOnly() bool {
+	return l.FileName == "_CONSOLE"
+}
+
+func (l *LiteralData) parse(r io.Reader) (err error) {
+	var buf [256]byte
+
+	_, err = readFull(r, buf[:2])
+	if err != nil {
+		return
+	}
+
+	l.Format = buf[0]
+	l.IsBinary = l.Format == 'b'
+	fileNameLen := int(buf[1])
+
+	_, err = readFull(r, buf[:fileNameLen])
+	if err != nil {
+		return
+	}
+
+	l.FileName = string(buf[:fileNameLen])
+
+	_, err = readFull(r, buf[:4])
+	if err != nil {
+		return
+	}
+
+	l.Time = binary.BigEndian.Uint32(buf[:4])
+	l.Body = r
+	return
+}
+
+// SerializeLiteral serializes a literal data packet to w and returns a
+// WriteCloser to which the data itself can be written and which MUST be closed
+// on completion. The fileName is truncated to 255 bytes.
+func SerializeLiteral(w io.WriteCloser, isBinary bool, fileName string, time uint32) (plaintext io.WriteCloser, err error) {
+	var buf [4]byte
+	buf[0] = 't'
+	if isBinary {
+		buf[0] = 'b'
+	}
+	if len(fileName) > 255 {
+		fileName = fileName[:255]
+	}
+	buf[1] = byte(len(fileName))
+
+	inner, err := serializeStreamHeader(w, packetTypeLiteralData)
+	if err != nil {
+		return
+	}
+
+	_, err = inner.Write(buf[:2])
+	if err != nil {
+		return
+	}
+	_, err = inner.Write([]byte(fileName))
+	if err != nil {
+		return
+	}
+	binary.BigEndian.PutUint32(buf[:], time)
+	_, err = inner.Write(buf[:])
+	if err != nil {
+		return
+	}
+
+	plaintext = inner
+	return
+}

vendor/github.com/ProtonMail/go-crypto/openpgp/packet/ocfb.go

@@ -0,0 +1,137 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// OpenPGP CFB Mode. http://tools.ietf.org/html/rfc4880#section-13.9
+
+package packet
+
+import (
+	"crypto/cipher"
+)
+
+type ocfbEncrypter struct {
+	b       cipher.Block
+	fre     []byte
+	outUsed int
+}
+
+// An OCFBResyncOption determines if the "resynchronization step" of OCFB is
+// performed.
+type OCFBResyncOption bool
+
+const (
+	OCFBResync   OCFBResyncOption = true
+	OCFBNoResync OCFBResyncOption = false
+)
+
+// NewOCFBEncrypter returns a cipher.Stream which encrypts data with OpenPGP's
+// cipher feedback mode using the given cipher.Block, and an initial amount of
+// ciphertext.  randData must be random bytes and be the same length as the
+// cipher.Block's block size. Resync determines if the "resynchronization step"
+// from RFC 4880, 13.9 step 7 is performed. Different parts of OpenPGP vary on
+// this point.
+func NewOCFBEncrypter(block cipher.Block, randData []byte, resync OCFBResyncOption) (cipher.Stream, []byte) {
+	blockSize := block.BlockSize()
+	if len(randData) != blockSize {
+		return nil, nil
+	}
+
+	x := &ocfbEncrypter{
+		b:       block,
+		fre:     make([]byte, blockSize),
+		outUsed: 0,
+	}
+	prefix := make([]byte, blockSize+2)
+
+	block.Encrypt(x.fre, x.fre)
+	for i := 0; i < blockSize; i++ {
+		prefix[i] = randData[i] ^ x.fre[i]
+	}
+
+	block.Encrypt(x.fre, prefix[:blockSize])
+	prefix[blockSize] = x.fre[0] ^ randData[blockSize-2]
+	prefix[blockSize+1] = x.fre[1] ^ randData[blockSize-1]
+
+	if resync {
+		block.Encrypt(x.fre, prefix[2:])
+	} else {
+		x.fre[0] = prefix[blockSize]
+		x.fre[1] = prefix[blockSize+1]
+		x.outUsed = 2
+	}
+	return x, prefix
+}
+
+func (x *ocfbEncrypter) XORKeyStream(dst, src []byte) {
+	for i := 0; i < len(src); i++ {
+		if x.outUsed == len(x.fre) {
+			x.b.Encrypt(x.fre, x.fre)
+			x.outUsed = 0
+		}
+
+		x.fre[x.outUsed] ^= src[i]
+		dst[i] = x.fre[x.outUsed]
+		x.outUsed++
+	}
+}
+
+type ocfbDecrypter struct {
+	b       cipher.Block
+	fre     []byte
+	outUsed int
+}
+
+// NewOCFBDecrypter returns a cipher.Stream which decrypts data with OpenPGP's
+// cipher feedback mode using the given cipher.Block. Prefix must be the first
+// blockSize + 2 bytes of the ciphertext, where blockSize is the cipher.Block's
+// block size. On successful exit, blockSize+2 bytes of decrypted data are written into
+// prefix. Resync determines if the "resynchronization step" from RFC 4880,
+// 13.9 step 7 is performed. Different parts of OpenPGP vary on this point.
+func NewOCFBDecrypter(block cipher.Block, prefix []byte, resync OCFBResyncOption) cipher.Stream {
+	blockSize := block.BlockSize()
+	if len(prefix) != blockSize+2 {
+		return nil
+	}
+
+	x := &ocfbDecrypter{
+		b:       block,
+		fre:     make([]byte, blockSize),
+		outUsed: 0,
+	}
+	prefixCopy := make([]byte, len(prefix))
+	copy(prefixCopy, prefix)
+
+	block.Encrypt(x.fre, x.fre)
+	for i := 0; i < blockSize; i++ {
+		prefixCopy[i] ^= x.fre[i]
+	}
+
+	block.Encrypt(x.fre, prefix[:blockSize])
+	prefixCopy[blockSize] ^= x.fre[0]
+	prefixCopy[blockSize+1] ^= x.fre[1]
+
+	if resync {
+		block.Encrypt(x.fre, prefix[2:])
+	} else {
+		x.fre[0] = prefix[blockSize]
+		x.fre[1] = prefix[blockSize+1]
+		x.outUsed = 2
+	}
+	copy(prefix, prefixCopy)
+	return x
+}
+
+func (x *ocfbDecrypter) XORKeyStream(dst, src []byte) {
+	for i := 0; i < len(src); i++ {
+		if x.outUsed == len(x.fre) {
+			x.b.Encrypt(x.fre, x.fre)
+			x.outUsed = 0
+		}
+
+		c := src[i]
+		dst[i] = x.fre[x.outUsed] ^ src[i]
+		x.fre[x.outUsed] = c
+		x.outUsed++
+	}
+}

vendor/github.com/ProtonMail/go-crypto/openpgp/packet/one_pass_signature.go

@@ -0,0 +1,73 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"crypto"
+	"encoding/binary"
+	"github.com/ProtonMail/go-crypto/openpgp/errors"
+	"github.com/ProtonMail/go-crypto/openpgp/s2k"
+	"io"
+	"strconv"
+)
+
+// OnePassSignature represents a one-pass signature packet. See RFC 4880,
+// section 5.4.
+type OnePassSignature struct {
+	SigType    SignatureType
+	Hash       crypto.Hash
+	PubKeyAlgo PublicKeyAlgorithm
+	KeyId      uint64
+	IsLast     bool
+}
+
+const onePassSignatureVersion = 3
+
+func (ops *OnePassSignature) parse(r io.Reader) (err error) {
+	var buf [13]byte
+
+	_, err = readFull(r, buf[:])
+	if err != nil {
+		return
+	}
+	if buf[0] != onePassSignatureVersion {
+		err = errors.UnsupportedError("one-pass-signature packet version " + strconv.Itoa(int(buf[0])))
+	}
+
+	var ok bool
+	ops.Hash, ok = s2k.HashIdToHash(buf[2])
+	if !ok {
+		return errors.UnsupportedError("hash function: " + strconv.Itoa(int(buf[2])))
+	}
+
+	ops.SigType = SignatureType(buf[1])
+	ops.PubKeyAlgo = PublicKeyAlgorithm(buf[3])
+	ops.KeyId = binary.BigEndian.Uint64(buf[4:12])
+	ops.IsLast = buf[12] != 0
+	return
+}
+
+// Serialize marshals the given OnePassSignature to w.
+func (ops *OnePassSignature) Serialize(w io.Writer) error {
+	var buf [13]byte
+	buf[0] = onePassSignatureVersion
+	buf[1] = uint8(ops.SigType)
+	var ok bool
+	buf[2], ok = s2k.HashToHashId(ops.Hash)
+	if !ok {
+		return errors.UnsupportedError("hash type: " + strconv.Itoa(int(ops.Hash)))
+	}
+	buf[3] = uint8(ops.PubKeyAlgo)
+	binary.BigEndian.PutUint64(buf[4:12], ops.KeyId)
+	if ops.IsLast {
+		buf[12] = 1
+	}
+
+	if err := serializeHeader(w, packetTypeOnePassSignature, len(buf)); err != nil {
+		return err
+	}
+	_, err := w.Write(buf[:])
+	return err
+}

vendor/github.com/ProtonMail/go-crypto/openpgp/packet/opaque.go

@@ -0,0 +1,162 @@
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"bytes"
+	"io"
+	"io/ioutil"
+
+	"github.com/ProtonMail/go-crypto/openpgp/errors"
+)
+
+// OpaquePacket represents an OpenPGP packet as raw, unparsed data. This is
+// useful for splitting and storing the original packet contents separately,
+// handling unsupported packet types or accessing parts of the packet not yet
+// implemented by this package.
+type OpaquePacket struct {
+	// Packet type
+	Tag uint8
+	// Reason why the packet was parsed opaquely
+	Reason error
+	// Binary contents of the packet data
+	Contents []byte
+}
+
+func (op *OpaquePacket) parse(r io.Reader) (err error) {
+	op.Contents, err = ioutil.ReadAll(r)
+	return
+}
+
+// Serialize marshals the packet to a writer in its original form, including
+// the packet header.
+func (op *OpaquePacket) Serialize(w io.Writer) (err error) {
+	err = serializeHeader(w, packetType(op.Tag), len(op.Contents))
+	if err == nil {
+		_, err = w.Write(op.Contents)
+	}
+	return
+}
+
+// Parse attempts to parse the opaque contents into a structure supported by
+// this package. If the packet is not known then the result will be another
+// OpaquePacket.
+func (op *OpaquePacket) Parse() (p Packet, err error) {
+	hdr := bytes.NewBuffer(nil)
+	err = serializeHeader(hdr, packetType(op.Tag), len(op.Contents))
+	if err != nil {
+		op.Reason = err
+		return op, err
+	}
+	p, err = Read(io.MultiReader(hdr, bytes.NewBuffer(op.Contents)))
+	if err != nil {
+		op.Reason = err
+		p = op
+	}
+	return
+}
+
+// OpaqueReader reads OpaquePackets from an io.Reader.
+type OpaqueReader struct {
+	r io.Reader
+}
+
+func NewOpaqueReader(r io.Reader) *OpaqueReader {
+	return &OpaqueReader{r: r}
+}
+
+// Read the next OpaquePacket.
+func (or *OpaqueReader) Next() (op *OpaquePacket, err error) {
+	tag, _, contents, err := readHeader(or.r)
+	if err != nil {
+		return
+	}
+	op = &OpaquePacket{Tag: uint8(tag), Reason: err}
+	err = op.parse(contents)
+	if err != nil {
+		consumeAll(contents)
+	}
+	return
+}
+
+// OpaqueSubpacket represents an unparsed OpenPGP subpacket,
+// as found in signature and user attribute packets.
+type OpaqueSubpacket struct {
+	SubType  uint8
+	Contents []byte
+}
+
+// OpaqueSubpackets extracts opaque, unparsed OpenPGP subpackets from
+// their byte representation.
+func OpaqueSubpackets(contents []byte) (result []*OpaqueSubpacket, err error) {
+	var (
+		subHeaderLen int
+		subPacket    *OpaqueSubpacket
+	)
+	for len(contents) > 0 {
+		subHeaderLen, subPacket, err = nextSubpacket(contents)
+		if err != nil {
+			break
+		}
+		result = append(result, subPacket)
+		contents = contents[subHeaderLen+len(subPacket.Contents):]
+	}
+	return
+}
+
+func nextSubpacket(contents []byte) (subHeaderLen int, subPacket *OpaqueSubpacket, err error) {
+	// RFC 4880, section 5.2.3.1
+	var subLen uint32
+	if len(contents) < 1 {
+		goto Truncated
+	}
+	subPacket = &OpaqueSubpacket{}
+	switch {
+	case contents[0] < 192:
+		subHeaderLen = 2 // 1 length byte, 1 subtype byte
+		if len(contents) < subHeaderLen {
+			goto Truncated
+		}
+		subLen = uint32(contents[0])
+		contents = contents[1:]
+	case contents[0] < 255:
+		subHeaderLen = 3 // 2 length bytes, 1 subtype
+		if len(contents) < subHeaderLen {
+			goto Truncated
+		}
+		subLen = uint32(contents[0]-192)<<8 + uint32(contents[1]) + 192
+		contents = contents[2:]
+	default:
+		subHeaderLen = 6 // 5 length bytes, 1 subtype
+		if len(contents) < subHeaderLen {
+			goto Truncated
+		}
+		subLen = uint32(contents[1])<<24 |
+			uint32(contents[2])<<16 |
+			uint32(contents[3])<<8 |
+			uint32(contents[4])
+		contents = contents[5:]
+	}
+	if subLen > uint32(len(contents)) || subLen == 0 {
+		goto Truncated
+	}
+	subPacket.SubType = contents[0]
+	subPacket.Contents = contents[1:subLen]
+	return
+Truncated:
+	err = errors.StructuralError("subpacket truncated")
+	return
+}
+
+func (osp *OpaqueSubpacket) Serialize(w io.Writer) (err error) {
+	buf := make([]byte, 6)
+	n := serializeSubpacketLength(buf, len(osp.Contents)+1)
+	buf[n] = osp.SubType
+	if _, err = w.Write(buf[:n+1]); err != nil {
+		return
+	}
+	_, err = w.Write(osp.Contents)
+	return
+}

vendor/github.com/ProtonMail/go-crypto/openpgp/packet/packet.go

@@ -0,0 +1,522 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Package packet implements parsing and serialization of OpenPGP packets, as
+// specified in RFC 4880.
+package packet // import "github.com/ProtonMail/go-crypto/openpgp/packet"
+
+import (
+	"bytes"
+	"crypto/cipher"
+	"crypto/rsa"
+	"io"
+
+	"github.com/ProtonMail/go-crypto/openpgp/errors"
+	"github.com/ProtonMail/go-crypto/openpgp/internal/algorithm"
+)
+
+// readFull is the same as io.ReadFull except that reading zero bytes returns
+// ErrUnexpectedEOF rather than EOF.
+func readFull(r io.Reader, buf []byte) (n int, err error) {
+	n, err = io.ReadFull(r, buf)
+	if err == io.EOF {
+		err = io.ErrUnexpectedEOF
+	}
+	return
+}
+
+// readLength reads an OpenPGP length from r. See RFC 4880, section 4.2.2.
+func readLength(r io.Reader) (length int64, isPartial bool, err error) {
+	var buf [4]byte
+	_, err = readFull(r, buf[:1])
+	if err != nil {
+		return
+	}
+	switch {
+	case buf[0] < 192:
+		length = int64(buf[0])
+	case buf[0] < 224:
+		length = int64(buf[0]-192) << 8
+		_, err = readFull(r, buf[0:1])
+		if err != nil {
+			return
+		}
+		length += int64(buf[0]) + 192
+	case buf[0] < 255:
+		length = int64(1) << (buf[0] & 0x1f)
+		isPartial = true
+	default:
+		_, err = readFull(r, buf[0:4])
+		if err != nil {
+			return
+		}
+		length = int64(buf[0])<<24 |
+			int64(buf[1])<<16 |
+			int64(buf[2])<<8 |
+			int64(buf[3])
+	}
+	return
+}
+
+// partialLengthReader wraps an io.Reader and handles OpenPGP partial lengths.
+// The continuation lengths are parsed and removed from the stream and EOF is
+// returned at the end of the packet. See RFC 4880, section 4.2.2.4.
+type partialLengthReader struct {
+	r         io.Reader
+	remaining int64
+	isPartial bool
+}
+
+func (r *partialLengthReader) Read(p []byte) (n int, err error) {
+	for r.remaining == 0 {
+		if !r.isPartial {
+			return 0, io.EOF
+		}
+		r.remaining, r.isPartial, err = readLength(r.r)
+		if err != nil {
+			return 0, err
+		}
+	}
+
+	toRead := int64(len(p))
+	if toRead > r.remaining {
+		toRead = r.remaining
+	}
+
+	n, err = r.r.Read(p[:int(toRead)])
+	r.remaining -= int64(n)
+	if n < int(toRead) && err == io.EOF {
+		err = io.ErrUnexpectedEOF
+	}
+	return
+}
+
+// partialLengthWriter writes a stream of data using OpenPGP partial lengths.
+// See RFC 4880, section 4.2.2.4.
+type partialLengthWriter struct {
+	w          io.WriteCloser
+	buf        bytes.Buffer
+	lengthByte [1]byte
+}
+
+func (w *partialLengthWriter) Write(p []byte) (n int, err error) {
+	bufLen := w.buf.Len()
+	if bufLen > 512 {
+		for power := uint(30); ; power-- {
+			l := 1 << power
+			if bufLen >= l {
+				w.lengthByte[0] = 224 + uint8(power)
+				_, err = w.w.Write(w.lengthByte[:])
+				if err != nil {
+					return
+				}
+				var m int
+				m, err = w.w.Write(w.buf.Next(l))
+				if err != nil {
+					return
+				}
+				if m != l {
+					return 0, io.ErrShortWrite
+				}
+				break
+			}
+		}
+	}
+	return w.buf.Write(p)
+}
+
+func (w *partialLengthWriter) Close() (err error) {
+	len := w.buf.Len()
+	err = serializeLength(w.w, len)
+	if err != nil {
+		return err
+	}
+	_, err = w.buf.WriteTo(w.w)
+	if err != nil {
+		return err
+	}
+	return w.w.Close()
+}
+
+// A spanReader is an io.LimitReader, but it returns ErrUnexpectedEOF if the
+// underlying Reader returns EOF before the limit has been reached.
+type spanReader struct {
+	r io.Reader
+	n int64
+}
+
+func (l *spanReader) Read(p []byte) (n int, err error) {
+	if l.n <= 0 {
+		return 0, io.EOF
+	}
+	if int64(len(p)) > l.n {
+		p = p[0:l.n]
+	}
+	n, err = l.r.Read(p)
+	l.n -= int64(n)
+	if l.n > 0 && err == io.EOF {
+		err = io.ErrUnexpectedEOF
+	}
+	return
+}
+
+// readHeader parses a packet header and returns an io.Reader which will return
+// the contents of the packet. See RFC 4880, section 4.2.
+func readHeader(r io.Reader) (tag packetType, length int64, contents io.Reader, err error) {
+	var buf [4]byte
+	_, err = io.ReadFull(r, buf[:1])
+	if err != nil {
+		return
+	}
+	if buf[0]&0x80 == 0 {
+		err = errors.StructuralError("tag byte does not have MSB set")
+		return
+	}
+	if buf[0]&0x40 == 0 {
+		// Old format packet
+		tag = packetType((buf[0] & 0x3f) >> 2)
+		lengthType := buf[0] & 3
+		if lengthType == 3 {
+			length = -1
+			contents = r
+			return
+		}
+		lengthBytes := 1 << lengthType
+		_, err = readFull(r, buf[0:lengthBytes])
+		if err != nil {
+			return
+		}
+		for i := 0; i < lengthBytes; i++ {
+			length <<= 8
+			length |= int64(buf[i])
+		}
+		contents = &spanReader{r, length}
+		return
+	}
+
+	// New format packet
+	tag = packetType(buf[0] & 0x3f)
+	length, isPartial, err := readLength(r)
+	if err != nil {
+		return
+	}
+	if isPartial {
+		contents = &partialLengthReader{
+			remaining: length,
+			isPartial: true,
+			r:         r,
+		}
+		length = -1
+	} else {
+		contents = &spanReader{r, length}
+	}
+	return
+}
+
+// serializeHeader writes an OpenPGP packet header to w. See RFC 4880, section
+// 4.2.
+func serializeHeader(w io.Writer, ptype packetType, length int) (err error) {
+	err = serializeType(w, ptype)
+	if err != nil {
+		return
+	}
+	return serializeLength(w, length)
+}
+
+// serializeType writes an OpenPGP packet type to w. See RFC 4880, section
+// 4.2.
+func serializeType(w io.Writer, ptype packetType) (err error) {
+	var buf [1]byte
+	buf[0] = 0x80 | 0x40 | byte(ptype)
+	_, err = w.Write(buf[:])
+	return
+}
+
+// serializeLength writes an OpenPGP packet length to w. See RFC 4880, section
+// 4.2.2.
+func serializeLength(w io.Writer, length int) (err error) {
+	var buf [5]byte
+	var n int
+
+	if length < 192 {
+		buf[0] = byte(length)
+		n = 1
+	} else if length < 8384 {
+		length -= 192
+		buf[0] = 192 + byte(length>>8)
+		buf[1] = byte(length)
+		n = 2
+	} else {
+		buf[0] = 255
+		buf[1] = byte(length >> 24)
+		buf[2] = byte(length >> 16)
+		buf[3] = byte(length >> 8)
+		buf[4] = byte(length)
+		n = 5
+	}
+
+	_, err = w.Write(buf[:n])
+	return
+}
+
+// serializeStreamHeader writes an OpenPGP packet header to w where the
+// length of the packet is unknown. It returns a io.WriteCloser which can be
+// used to write the contents of the packet. See RFC 4880, section 4.2.
+func serializeStreamHeader(w io.WriteCloser, ptype packetType) (out io.WriteCloser, err error) {
+	err = serializeType(w, ptype)
+	if err != nil {
+		return
+	}
+	out = &partialLengthWriter{w: w}
+	return
+}
+
+// Packet represents an OpenPGP packet. Users are expected to try casting
+// instances of this interface to specific packet types.
+type Packet interface {
+	parse(io.Reader) error
+}
+
+// consumeAll reads from the given Reader until error, returning the number of
+// bytes read.
+func consumeAll(r io.Reader) (n int64, err error) {
+	var m int
+	var buf [1024]byte
+
+	for {
+		m, err = r.Read(buf[:])
+		n += int64(m)
+		if err == io.EOF {
+			err = nil
+			return
+		}
+		if err != nil {
+			return
+		}
+	}
+}
+
+// packetType represents the numeric ids of the different OpenPGP packet types. See
+// http://www.iana.org/assignments/pgp-parameters/pgp-parameters.xhtml#pgp-parameters-2
+type packetType uint8
+
+const (
+	packetTypeEncryptedKey              packetType = 1
+	packetTypeSignature                 packetType = 2
+	packetTypeSymmetricKeyEncrypted     packetType = 3
+	packetTypeOnePassSignature          packetType = 4
+	packetTypePrivateKey                packetType = 5
+	packetTypePublicKey                 packetType = 6
+	packetTypePrivateSubkey             packetType = 7
+	packetTypeCompressed                packetType = 8
+	packetTypeSymmetricallyEncrypted    packetType = 9
+	packetTypeLiteralData               packetType = 11
+	packetTypeUserId                    packetType = 13
+	packetTypePublicSubkey              packetType = 14
+	packetTypeUserAttribute             packetType = 17
+	packetTypeSymmetricallyEncryptedMDC packetType = 18
+	packetTypeAEADEncrypted             packetType = 20
+)
+
+// EncryptedDataPacket holds encrypted data. It is currently implemented by
+// SymmetricallyEncrypted and AEADEncrypted.
+type EncryptedDataPacket interface {
+	Decrypt(CipherFunction, []byte) (io.ReadCloser, error)
+}
+
+// Read reads a single OpenPGP packet from the given io.Reader. If there is an
+// error parsing a packet, the whole packet is consumed from the input.
+func Read(r io.Reader) (p Packet, err error) {
+	tag, _, contents, err := readHeader(r)
+	if err != nil {
+		return
+	}
+
+	switch tag {
+	case packetTypeEncryptedKey:
+		p = new(EncryptedKey)
+	case packetTypeSignature:
+		p = new(Signature)
+	case packetTypeSymmetricKeyEncrypted:
+		p = new(SymmetricKeyEncrypted)
+	case packetTypeOnePassSignature:
+		p = new(OnePassSignature)
+	case packetTypePrivateKey, packetTypePrivateSubkey:
+		pk := new(PrivateKey)
+		if tag == packetTypePrivateSubkey {
+			pk.IsSubkey = true
+		}
+		p = pk
+	case packetTypePublicKey, packetTypePublicSubkey:
+		isSubkey := tag == packetTypePublicSubkey
+		p = &PublicKey{IsSubkey: isSubkey}
+	case packetTypeCompressed:
+		p = new(Compressed)
+	case packetTypeSymmetricallyEncrypted:
+		err = errors.UnsupportedError("Symmetrically encrypted packets without MDC are not supported")
+	case packetTypeLiteralData:
+		p = new(LiteralData)
+	case packetTypeUserId:
+		p = new(UserId)
+	case packetTypeUserAttribute:
+		p = new(UserAttribute)
+	case packetTypeSymmetricallyEncryptedMDC:
+		se := new(SymmetricallyEncrypted)
+		se.MDC = true
+		p = se
+	case packetTypeAEADEncrypted:
+		p = new(AEADEncrypted)
+	default:
+		err = errors.UnknownPacketTypeError(tag)
+	}
+	if p != nil {
+		err = p.parse(contents)
+	}
+	if err != nil {
+		consumeAll(contents)
+	}
+	return
+}
+
+// SignatureType represents the different semantic meanings of an OpenPGP
+// signature. See RFC 4880, section 5.2.1.
+type SignatureType uint8
+
+const (
+	SigTypeBinary            SignatureType = 0x00
+	SigTypeText                            = 0x01
+	SigTypeGenericCert                     = 0x10
+	SigTypePersonaCert                     = 0x11
+	SigTypeCasualCert                      = 0x12
+	SigTypePositiveCert                    = 0x13
+	SigTypeSubkeyBinding                   = 0x18
+	SigTypePrimaryKeyBinding               = 0x19
+	SigTypeDirectSignature                 = 0x1F
+	SigTypeKeyRevocation                   = 0x20
+	SigTypeSubkeyRevocation                = 0x28
+)
+
+// PublicKeyAlgorithm represents the different public key system specified for
+// OpenPGP. See
+// http://www.iana.org/assignments/pgp-parameters/pgp-parameters.xhtml#pgp-parameters-12
+type PublicKeyAlgorithm uint8
+
+const (
+	PubKeyAlgoRSA     PublicKeyAlgorithm = 1
+	PubKeyAlgoElGamal PublicKeyAlgorithm = 16
+	PubKeyAlgoDSA     PublicKeyAlgorithm = 17
+	// RFC 6637, Section 5.
+	PubKeyAlgoECDH  PublicKeyAlgorithm = 18
+	PubKeyAlgoECDSA PublicKeyAlgorithm = 19
+	// https://www.ietf.org/archive/id/draft-koch-eddsa-for-openpgp-04.txt
+	PubKeyAlgoEdDSA PublicKeyAlgorithm = 22
+
+	// Deprecated in RFC 4880, Section 13.5. Use key flags instead.
+	PubKeyAlgoRSAEncryptOnly PublicKeyAlgorithm = 2
+	PubKeyAlgoRSASignOnly    PublicKeyAlgorithm = 3
+)
+
+// CanEncrypt returns true if it's possible to encrypt a message to a public
+// key of the given type.
+func (pka PublicKeyAlgorithm) CanEncrypt() bool {
+	switch pka {
+	case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoElGamal, PubKeyAlgoECDH:
+		return true
+	}
+	return false
+}
+
+// CanSign returns true if it's possible for a public key of the given type to
+// sign a message.
+func (pka PublicKeyAlgorithm) CanSign() bool {
+	switch pka {
+	case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly, PubKeyAlgoDSA, PubKeyAlgoECDSA, PubKeyAlgoEdDSA:
+		return true
+	}
+	return false
+}
+
+// CipherFunction represents the different block ciphers specified for OpenPGP. See
+// http://www.iana.org/assignments/pgp-parameters/pgp-parameters.xhtml#pgp-parameters-13
+type CipherFunction algorithm.CipherFunction
+
+const (
+	Cipher3DES   CipherFunction = 2
+	CipherCAST5  CipherFunction = 3
+	CipherAES128 CipherFunction = 7
+	CipherAES192 CipherFunction = 8
+	CipherAES256 CipherFunction = 9
+)
+
+// KeySize returns the key size, in bytes, of cipher.
+func (cipher CipherFunction) KeySize() int {
+	return algorithm.CipherFunction(cipher).KeySize()
+}
+
+// blockSize returns the block size, in bytes, of cipher.
+func (cipher CipherFunction) blockSize() int {
+	return algorithm.CipherFunction(cipher).BlockSize()
+}
+
+// new returns a fresh instance of the given cipher.
+func (cipher CipherFunction) new(key []byte) (block cipher.Block) {
+	return algorithm.CipherFunction(cipher).New(key)
+}
+
+// padToKeySize left-pads a MPI with zeroes to match the length of the
+// specified RSA public.
+func padToKeySize(pub *rsa.PublicKey, b []byte) []byte {
+	k := (pub.N.BitLen() + 7) / 8
+	if len(b) >= k {
+		return b
+	}
+	bb := make([]byte, k)
+	copy(bb[len(bb)-len(b):], b)
+	return bb
+}
+
+// CompressionAlgo Represents the different compression algorithms
+// supported by OpenPGP (except for BZIP2, which is not currently
+// supported). See Section 9.3 of RFC 4880.
+type CompressionAlgo uint8
+
+const (
+	CompressionNone CompressionAlgo = 0
+	CompressionZIP  CompressionAlgo = 1
+	CompressionZLIB CompressionAlgo = 2
+)
+
+// AEADMode represents the different Authenticated Encryption with Associated
+// Data specified for OpenPGP.
+type AEADMode algorithm.AEADMode
+
+const (
+	AEADModeEAX             AEADMode = 1
+	AEADModeOCB             AEADMode = 2
+	AEADModeExperimentalGCM AEADMode = 100
+)
+
+func (mode AEADMode) NonceLength() int {
+	return algorithm.AEADMode(mode).NonceLength()
+}
+
+func (mode AEADMode) TagLength() int {
+	return algorithm.AEADMode(mode).TagLength()
+}
+
+// new returns a fresh instance of the given mode.
+func (mode AEADMode) new(block cipher.Block) cipher.AEAD {
+	return algorithm.AEADMode(mode).New(block)
+}
+
+// ReasonForRevocation represents a revocation reason code as per RFC4880
+// section 5.2.3.23.
+type ReasonForRevocation uint8
+
+const (
+	NoReason       ReasonForRevocation = 0
+	KeySuperseded  ReasonForRevocation = 1
+	KeyCompromised ReasonForRevocation = 2
+	KeyRetired     ReasonForRevocation = 3
+)

vendor/github.com/ProtonMail/go-crypto/openpgp/packet/private_key.go

@@ -0,0 +1,780 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"bytes"
+	"crypto"
+	"crypto/cipher"
+	"crypto/dsa"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rand"
+	"crypto/rsa"
+	"crypto/sha1"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"math/big"
+	"strconv"
+	"time"
+
+	"github.com/ProtonMail/go-crypto/openpgp/internal/ecc"
+	"golang.org/x/crypto/curve25519"
+
+	"github.com/ProtonMail/go-crypto/openpgp/ecdh"
+	"github.com/ProtonMail/go-crypto/openpgp/elgamal"
+	"github.com/ProtonMail/go-crypto/openpgp/errors"
+	"github.com/ProtonMail/go-crypto/openpgp/internal/encoding"
+	"github.com/ProtonMail/go-crypto/openpgp/s2k"
+	"golang.org/x/crypto/ed25519"
+)
+
+// PrivateKey represents a possibly encrypted private key. See RFC 4880,
+// section 5.5.3.
+type PrivateKey struct {
+	PublicKey
+	Encrypted     bool // if true then the private key is unavailable until Decrypt has been called.
+	encryptedData []byte
+	cipher        CipherFunction
+	s2k           func(out, in []byte)
+	// An *{rsa|dsa|elgamal|ecdh|ecdsa|ed25519}.PrivateKey or
+	// crypto.Signer/crypto.Decrypter (Decryptor RSA only).
+	PrivateKey   interface{}
+	sha1Checksum bool
+	iv           []byte
+
+	// Type of encryption of the S2K packet
+	// Allowed values are 0 (Not encrypted), 254 (SHA1), or
+	// 255 (2-byte checksum)
+	s2kType S2KType
+	// Full parameters of the S2K packet
+	s2kParams *s2k.Params
+}
+
+//S2KType s2k packet type
+type S2KType uint8
+
+const (
+	// S2KNON unencrypt
+	S2KNON S2KType = 0
+	// S2KSHA1 sha1 sum check
+	S2KSHA1 S2KType = 254
+	// S2KCHECKSUM sum check
+	S2KCHECKSUM S2KType = 255
+)
+
+func NewRSAPrivateKey(creationTime time.Time, priv *rsa.PrivateKey) *PrivateKey {
+	pk := new(PrivateKey)
+	pk.PublicKey = *NewRSAPublicKey(creationTime, &priv.PublicKey)
+	pk.PrivateKey = priv
+	return pk
+}
+
+func NewDSAPrivateKey(creationTime time.Time, priv *dsa.PrivateKey) *PrivateKey {
+	pk := new(PrivateKey)
+	pk.PublicKey = *NewDSAPublicKey(creationTime, &priv.PublicKey)
+	pk.PrivateKey = priv
+	return pk
+}
+
+func NewElGamalPrivateKey(creationTime time.Time, priv *elgamal.PrivateKey) *PrivateKey {
+	pk := new(PrivateKey)
+	pk.PublicKey = *NewElGamalPublicKey(creationTime, &priv.PublicKey)
+	pk.PrivateKey = priv
+	return pk
+}
+
+func NewECDSAPrivateKey(creationTime time.Time, priv *ecdsa.PrivateKey) *PrivateKey {
+	pk := new(PrivateKey)
+	pk.PublicKey = *NewECDSAPublicKey(creationTime, &priv.PublicKey)
+	pk.PrivateKey = priv
+	return pk
+}
+
+func NewEdDSAPrivateKey(creationTime time.Time, priv *ed25519.PrivateKey) *PrivateKey {
+	pk := new(PrivateKey)
+	pub := priv.Public().(ed25519.PublicKey)
+	pk.PublicKey = *NewEdDSAPublicKey(creationTime, &pub)
+	pk.PrivateKey = priv
+	return pk
+}
+
+func NewECDHPrivateKey(creationTime time.Time, priv *ecdh.PrivateKey) *PrivateKey {
+	pk := new(PrivateKey)
+	pk.PublicKey = *NewECDHPublicKey(creationTime, &priv.PublicKey)
+	pk.PrivateKey = priv
+	return pk
+}
+
+// NewSignerPrivateKey creates a PrivateKey from a crypto.Signer that
+// implements RSA, ECDSA or EdDSA.
+func NewSignerPrivateKey(creationTime time.Time, signer crypto.Signer) *PrivateKey {
+	pk := new(PrivateKey)
+	// In general, the public Keys should be used as pointers. We still
+	// type-switch on the values, for backwards-compatibility.
+	switch pubkey := signer.Public().(type) {
+	case *rsa.PublicKey:
+		pk.PublicKey = *NewRSAPublicKey(creationTime, pubkey)
+	case rsa.PublicKey:
+		pk.PublicKey = *NewRSAPublicKey(creationTime, &pubkey)
+	case *ecdsa.PublicKey:
+		pk.PublicKey = *NewECDSAPublicKey(creationTime, pubkey)
+	case ecdsa.PublicKey:
+		pk.PublicKey = *NewECDSAPublicKey(creationTime, &pubkey)
+	case *ed25519.PublicKey:
+		pk.PublicKey = *NewEdDSAPublicKey(creationTime, pubkey)
+	case ed25519.PublicKey:
+		pk.PublicKey = *NewEdDSAPublicKey(creationTime, &pubkey)
+	default:
+		panic("openpgp: unknown crypto.Signer type in NewSignerPrivateKey")
+	}
+	pk.PrivateKey = signer
+	return pk
+}
+
+// NewDecrypterPrivateKey creates a PrivateKey from a *{rsa|elgamal|ecdh}.PrivateKey.
+func NewDecrypterPrivateKey(creationTime time.Time, decrypter interface{}) *PrivateKey {
+	pk := new(PrivateKey)
+	switch priv := decrypter.(type) {
+	case *rsa.PrivateKey:
+		pk.PublicKey = *NewRSAPublicKey(creationTime, &priv.PublicKey)
+	case *elgamal.PrivateKey:
+		pk.PublicKey = *NewElGamalPublicKey(creationTime, &priv.PublicKey)
+	case *ecdh.PrivateKey:
+		pk.PublicKey = *NewECDHPublicKey(creationTime, &priv.PublicKey)
+	default:
+		panic("openpgp: unknown decrypter type in NewDecrypterPrivateKey")
+	}
+	pk.PrivateKey = decrypter
+	return pk
+}
+
+func (pk *PrivateKey) parse(r io.Reader) (err error) {
+	err = (&pk.PublicKey).parse(r)
+	if err != nil {
+		return
+	}
+	v5 := pk.PublicKey.Version == 5
+
+	var buf [1]byte
+	_, err = readFull(r, buf[:])
+	if err != nil {
+		return
+	}
+	pk.s2kType = S2KType(buf[0])
+	var optCount [1]byte
+	if v5 {
+		if _, err = readFull(r, optCount[:]); err != nil {
+			return
+		}
+	}
+
+	switch pk.s2kType {
+	case S2KNON:
+		pk.s2k = nil
+		pk.Encrypted = false
+	case S2KSHA1, S2KCHECKSUM:
+		if v5 && pk.s2kType == S2KCHECKSUM {
+			return errors.StructuralError("wrong s2k identifier for version 5")
+		}
+		_, err = readFull(r, buf[:])
+		if err != nil {
+			return
+		}
+		pk.cipher = CipherFunction(buf[0])
+		pk.s2kParams, err = s2k.ParseIntoParams(r)
+		if err != nil {
+			return
+		}
+		if pk.s2kParams.Dummy() {
+			return
+		}
+		pk.s2k, err = pk.s2kParams.Function()
+		if err != nil {
+			return
+		}
+		pk.Encrypted = true
+		if pk.s2kType == S2KSHA1 {
+			pk.sha1Checksum = true
+		}
+	default:
+		return errors.UnsupportedError("deprecated s2k function in private key")
+	}
+
+	if pk.Encrypted {
+		blockSize := pk.cipher.blockSize()
+		if blockSize == 0 {
+			return errors.UnsupportedError("unsupported cipher in private key: " + strconv.Itoa(int(pk.cipher)))
+		}
+		pk.iv = make([]byte, blockSize)
+		_, err = readFull(r, pk.iv)
+		if err != nil {
+			return
+		}
+	}
+
+	var privateKeyData []byte
+	if v5 {
+		var n [4]byte /* secret material four octet count */
+		_, err = readFull(r, n[:])
+		if err != nil {
+			return
+		}
+		count := uint32(uint32(n[0])<<24 | uint32(n[1])<<16 | uint32(n[2])<<8 | uint32(n[3]))
+		if !pk.Encrypted {
+			count = count + 2 /* two octet checksum */
+		}
+		privateKeyData = make([]byte, count)
+		_, err = readFull(r, privateKeyData)
+		if err != nil {
+			return
+		}
+	} else {
+		privateKeyData, err = ioutil.ReadAll(r)
+		if err != nil {
+			return
+		}
+	}
+	if !pk.Encrypted {
+		return pk.parsePrivateKey(privateKeyData)
+	}
+
+	pk.encryptedData = privateKeyData
+	return
+}
+
+// Dummy returns true if the private key is a dummy key. This is a GNU extension.
+func (pk *PrivateKey) Dummy() bool {
+	return pk.s2kParams.Dummy()
+}
+
+func mod64kHash(d []byte) uint16 {
+	var h uint16
+	for _, b := range d {
+		h += uint16(b)
+	}
+	return h
+}
+
+func (pk *PrivateKey) Serialize(w io.Writer) (err error) {
+	contents := bytes.NewBuffer(nil)
+	err = pk.PublicKey.serializeWithoutHeaders(contents)
+	if err != nil {
+		return
+	}
+	if _, err = contents.Write([]byte{uint8(pk.s2kType)}); err != nil {
+		return
+	}
+
+	optional := bytes.NewBuffer(nil)
+	if pk.Encrypted || pk.Dummy() {
+		optional.Write([]byte{uint8(pk.cipher)})
+		if err := pk.s2kParams.Serialize(optional); err != nil {
+			return err
+		}
+		if pk.Encrypted {
+			optional.Write(pk.iv)
+		}
+	}
+	if pk.Version == 5 {
+		contents.Write([]byte{uint8(optional.Len())})
+	}
+	io.Copy(contents, optional)
+
+	if !pk.Dummy() {
+		l := 0
+		var priv []byte
+		if !pk.Encrypted {
+			buf := bytes.NewBuffer(nil)
+			err = pk.serializePrivateKey(buf)
+			if err != nil {
+				return err
+			}
+			l = buf.Len()
+			if pk.sha1Checksum {
+				h := sha1.New()
+				h.Write(buf.Bytes())
+				buf.Write(h.Sum(nil))
+			} else {
+				checksum := mod64kHash(buf.Bytes())
+				buf.Write([]byte{byte(checksum >> 8), byte(checksum)})
+			}
+			priv = buf.Bytes()
+		} else {
+			priv, l = pk.encryptedData, len(pk.encryptedData)
+		}
+
+		if pk.Version == 5 {
+			contents.Write([]byte{byte(l >> 24), byte(l >> 16), byte(l >> 8), byte(l)})
+		}
+		contents.Write(priv)
+	}
+
+	ptype := packetTypePrivateKey
+	if pk.IsSubkey {
+		ptype = packetTypePrivateSubkey
+	}
+	err = serializeHeader(w, ptype, contents.Len())
+	if err != nil {
+		return
+	}
+	_, err = io.Copy(w, contents)
+	if err != nil {
+		return
+	}
+	return
+}
+
+func serializeRSAPrivateKey(w io.Writer, priv *rsa.PrivateKey) error {
+	if _, err := w.Write(new(encoding.MPI).SetBig(priv.D).EncodedBytes()); err != nil {
+		return err
+	}
+	if _, err := w.Write(new(encoding.MPI).SetBig(priv.Primes[1]).EncodedBytes()); err != nil {
+		return err
+	}
+	if _, err := w.Write(new(encoding.MPI).SetBig(priv.Primes[0]).EncodedBytes()); err != nil {
+		return err
+	}
+	_, err := w.Write(new(encoding.MPI).SetBig(priv.Precomputed.Qinv).EncodedBytes())
+	return err
+}
+
+func serializeDSAPrivateKey(w io.Writer, priv *dsa.PrivateKey) error {
+	_, err := w.Write(new(encoding.MPI).SetBig(priv.X).EncodedBytes())
+	return err
+}
+
+func serializeElGamalPrivateKey(w io.Writer, priv *elgamal.PrivateKey) error {
+	_, err := w.Write(new(encoding.MPI).SetBig(priv.X).EncodedBytes())
+	return err
+}
+
+func serializeECDSAPrivateKey(w io.Writer, priv *ecdsa.PrivateKey) error {
+	_, err := w.Write(new(encoding.MPI).SetBig(priv.D).EncodedBytes())
+	return err
+}
+
+func serializeEdDSAPrivateKey(w io.Writer, priv *ed25519.PrivateKey) error {
+	keySize := ed25519.PrivateKeySize - ed25519.PublicKeySize
+	_, err := w.Write(encoding.NewMPI((*priv)[:keySize]).EncodedBytes())
+	return err
+}
+
+func serializeECDHPrivateKey(w io.Writer, priv *ecdh.PrivateKey) error {
+	_, err := w.Write(encoding.NewMPI(priv.D).EncodedBytes())
+	return err
+}
+
+// Decrypt decrypts an encrypted private key using a passphrase.
+func (pk *PrivateKey) Decrypt(passphrase []byte) error {
+	if pk.Dummy() {
+		return errors.ErrDummyPrivateKey("dummy key found")
+	}
+	if !pk.Encrypted {
+		return nil
+	}
+
+	key := make([]byte, pk.cipher.KeySize())
+	pk.s2k(key, passphrase)
+	block := pk.cipher.new(key)
+	cfb := cipher.NewCFBDecrypter(block, pk.iv)
+
+	data := make([]byte, len(pk.encryptedData))
+	cfb.XORKeyStream(data, pk.encryptedData)
+
+	if pk.sha1Checksum {
+		if len(data) < sha1.Size {
+			return errors.StructuralError("truncated private key data")
+		}
+		h := sha1.New()
+		h.Write(data[:len(data)-sha1.Size])
+		sum := h.Sum(nil)
+		if !bytes.Equal(sum, data[len(data)-sha1.Size:]) {
+			return errors.StructuralError("private key checksum failure")
+		}
+		data = data[:len(data)-sha1.Size]
+	} else {
+		if len(data) < 2 {
+			return errors.StructuralError("truncated private key data")
+		}
+		var sum uint16
+		for i := 0; i < len(data)-2; i++ {
+			sum += uint16(data[i])
+		}
+		if data[len(data)-2] != uint8(sum>>8) ||
+			data[len(data)-1] != uint8(sum) {
+			return errors.StructuralError("private key checksum failure")
+		}
+		data = data[:len(data)-2]
+	}
+
+	err := pk.parsePrivateKey(data)
+	if _, ok := err.(errors.KeyInvalidError); ok {
+		return errors.KeyInvalidError("invalid key parameters")
+	}
+	if err != nil {
+		return err
+	}
+
+	// Mark key as unencrypted
+	pk.s2kType = S2KNON
+	pk.s2k = nil
+	pk.Encrypted = false
+	pk.encryptedData = nil
+
+	return nil
+}
+
+// Encrypt encrypts an unencrypted private key using a passphrase.
+func (pk *PrivateKey) Encrypt(passphrase []byte) error {
+	priv := bytes.NewBuffer(nil)
+	err := pk.serializePrivateKey(priv)
+	if err != nil {
+		return err
+	}
+
+	//Default config of private key encryption
+	pk.cipher = CipherAES256
+	s2kConfig := &s2k.Config{
+		S2KMode:  3, //Iterated
+		S2KCount: 65536,
+		Hash:     crypto.SHA256,
+	}
+
+	pk.s2kParams, err = s2k.Generate(rand.Reader, s2kConfig)
+	if err != nil {
+		return err
+	}
+	privateKeyBytes := priv.Bytes()
+	key := make([]byte, pk.cipher.KeySize())
+
+	pk.sha1Checksum = true
+	pk.s2k, err = pk.s2kParams.Function()
+	if err != nil {
+		return err
+	}
+	pk.s2k(key, passphrase)
+	block := pk.cipher.new(key)
+	pk.iv = make([]byte, pk.cipher.blockSize())
+	_, err = rand.Read(pk.iv)
+	if err != nil {
+		return err
+	}
+	cfb := cipher.NewCFBEncrypter(block, pk.iv)
+
+	if pk.sha1Checksum {
+		pk.s2kType = S2KSHA1
+		h := sha1.New()
+		h.Write(privateKeyBytes)
+		sum := h.Sum(nil)
+		privateKeyBytes = append(privateKeyBytes, sum...)
+	} else {
+		pk.s2kType = S2KCHECKSUM
+		var sum uint16
+		for _, b := range privateKeyBytes {
+			sum += uint16(b)
+		}
+		priv.Write([]byte{uint8(sum >> 8), uint8(sum)})
+	}
+
+	pk.encryptedData = make([]byte, len(privateKeyBytes))
+	cfb.XORKeyStream(pk.encryptedData, privateKeyBytes)
+	pk.Encrypted = true
+	pk.PrivateKey = nil
+	return err
+}
+
+func (pk *PrivateKey) serializePrivateKey(w io.Writer) (err error) {
+	switch priv := pk.PrivateKey.(type) {
+	case *rsa.PrivateKey:
+		err = serializeRSAPrivateKey(w, priv)
+	case *dsa.PrivateKey:
+		err = serializeDSAPrivateKey(w, priv)
+	case *elgamal.PrivateKey:
+		err = serializeElGamalPrivateKey(w, priv)
+	case *ecdsa.PrivateKey:
+		err = serializeECDSAPrivateKey(w, priv)
+	case *ed25519.PrivateKey:
+		err = serializeEdDSAPrivateKey(w, priv)
+	case *ecdh.PrivateKey:
+		err = serializeECDHPrivateKey(w, priv)
+	default:
+		err = errors.InvalidArgumentError("unknown private key type")
+	}
+	return
+}
+
+func (pk *PrivateKey) parsePrivateKey(data []byte) (err error) {
+	switch pk.PublicKey.PubKeyAlgo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly, PubKeyAlgoRSAEncryptOnly:
+		return pk.parseRSAPrivateKey(data)
+	case PubKeyAlgoDSA:
+		return pk.parseDSAPrivateKey(data)
+	case PubKeyAlgoElGamal:
+		return pk.parseElGamalPrivateKey(data)
+	case PubKeyAlgoECDSA:
+		return pk.parseECDSAPrivateKey(data)
+	case PubKeyAlgoECDH:
+		return pk.parseECDHPrivateKey(data)
+	case PubKeyAlgoEdDSA:
+		return pk.parseEdDSAPrivateKey(data)
+	}
+	panic("impossible")
+}
+
+func (pk *PrivateKey) parseRSAPrivateKey(data []byte) (err error) {
+	rsaPub := pk.PublicKey.PublicKey.(*rsa.PublicKey)
+	rsaPriv := new(rsa.PrivateKey)
+	rsaPriv.PublicKey = *rsaPub
+
+	buf := bytes.NewBuffer(data)
+	d := new(encoding.MPI)
+	if _, err := d.ReadFrom(buf); err != nil {
+		return err
+	}
+
+	p := new(encoding.MPI)
+	if _, err := p.ReadFrom(buf); err != nil {
+		return err
+	}
+
+	q := new(encoding.MPI)
+	if _, err := q.ReadFrom(buf); err != nil {
+		return err
+	}
+
+	rsaPriv.D = new(big.Int).SetBytes(d.Bytes())
+	rsaPriv.Primes = make([]*big.Int, 2)
+	rsaPriv.Primes[0] = new(big.Int).SetBytes(p.Bytes())
+	rsaPriv.Primes[1] = new(big.Int).SetBytes(q.Bytes())
+	if err := rsaPriv.Validate(); err != nil {
+		return errors.KeyInvalidError(err.Error())
+	}
+	rsaPriv.Precompute()
+	pk.PrivateKey = rsaPriv
+
+	return nil
+}
+
+func (pk *PrivateKey) parseDSAPrivateKey(data []byte) (err error) {
+	dsaPub := pk.PublicKey.PublicKey.(*dsa.PublicKey)
+	dsaPriv := new(dsa.PrivateKey)
+	dsaPriv.PublicKey = *dsaPub
+
+	buf := bytes.NewBuffer(data)
+	x := new(encoding.MPI)
+	if _, err := x.ReadFrom(buf); err != nil {
+		return err
+	}
+
+	dsaPriv.X = new(big.Int).SetBytes(x.Bytes())
+	if err := validateDSAParameters(dsaPriv); err != nil {
+		return err
+	}
+	pk.PrivateKey = dsaPriv
+
+	return nil
+}
+
+func (pk *PrivateKey) parseElGamalPrivateKey(data []byte) (err error) {
+	pub := pk.PublicKey.PublicKey.(*elgamal.PublicKey)
+	priv := new(elgamal.PrivateKey)
+	priv.PublicKey = *pub
+
+	buf := bytes.NewBuffer(data)
+	x := new(encoding.MPI)
+	if _, err := x.ReadFrom(buf); err != nil {
+		return err
+	}
+
+	priv.X = new(big.Int).SetBytes(x.Bytes())
+	if err := validateElGamalParameters(priv); err != nil {
+		return err
+	}
+	pk.PrivateKey = priv
+
+	return nil
+}
+
+func (pk *PrivateKey) parseECDSAPrivateKey(data []byte) (err error) {
+	ecdsaPub := pk.PublicKey.PublicKey.(*ecdsa.PublicKey)
+	ecdsaPriv := new(ecdsa.PrivateKey)
+	ecdsaPriv.PublicKey = *ecdsaPub
+
+	buf := bytes.NewBuffer(data)
+	d := new(encoding.MPI)
+	if _, err := d.ReadFrom(buf); err != nil {
+		return err
+	}
+
+	ecdsaPriv.D = new(big.Int).SetBytes(d.Bytes())
+	if err := validateECDSAParameters(ecdsaPriv); err != nil {
+		return err
+	}
+	pk.PrivateKey = ecdsaPriv
+
+	return nil
+}
+
+func (pk *PrivateKey) parseECDHPrivateKey(data []byte) (err error) {
+	ecdhPub := pk.PublicKey.PublicKey.(*ecdh.PublicKey)
+	ecdhPriv := new(ecdh.PrivateKey)
+	ecdhPriv.PublicKey = *ecdhPub
+
+	buf := bytes.NewBuffer(data)
+	d := new(encoding.MPI)
+	if _, err := d.ReadFrom(buf); err != nil {
+		return err
+	}
+
+	ecdhPriv.D = d.Bytes()
+	if err := validateECDHParameters(ecdhPriv); err != nil {
+		return err
+	}
+	pk.PrivateKey = ecdhPriv
+
+	return nil
+}
+
+func (pk *PrivateKey) parseEdDSAPrivateKey(data []byte) (err error) {
+	eddsaPub := pk.PublicKey.PublicKey.(*ed25519.PublicKey)
+	eddsaPriv := make(ed25519.PrivateKey, ed25519.PrivateKeySize)
+
+	buf := bytes.NewBuffer(data)
+	d := new(encoding.MPI)
+	if _, err := d.ReadFrom(buf); err != nil {
+		return err
+	}
+
+	priv := d.Bytes()
+	copy(eddsaPriv[32-len(priv):32], priv)
+	copy(eddsaPriv[32:], (*eddsaPub)[:])
+	if err := validateEdDSAParameters(&eddsaPriv); err != nil {
+		return err
+	}
+	pk.PrivateKey = &eddsaPriv
+
+	return nil
+}
+
+func validateECDSAParameters(priv *ecdsa.PrivateKey) error {
+	return validateCommonECC(priv.Curve, priv.D.Bytes(), priv.X, priv.Y)
+}
+
+func validateECDHParameters(priv *ecdh.PrivateKey) error {
+	if priv.CurveType != ecc.Curve25519 {
+		return validateCommonECC(priv.Curve, priv.D, priv.X, priv.Y)
+	}
+	// Handle Curve25519
+	Q := priv.X.Bytes()[1:]
+	var d [32]byte
+	// Copy reversed d
+	l := len(priv.D)
+	for i := 0; i < l; i++ {
+		d[i] = priv.D[l-i-1]
+	}
+	var expectedQ [32]byte
+	curve25519.ScalarBaseMult(&expectedQ, &d)
+	if !bytes.Equal(Q, expectedQ[:]) {
+		return errors.KeyInvalidError("ECDH curve25519: invalid point")
+	}
+	return nil
+}
+
+func validateCommonECC(curve elliptic.Curve, d []byte, X, Y *big.Int) error {
+	// the public point should not be at infinity (0,0)
+	zero := new(big.Int)
+	if X.Cmp(zero) == 0 && Y.Cmp(zero) == 0 {
+		return errors.KeyInvalidError(fmt.Sprintf("ecc (%s): infinity point", curve.Params().Name))
+	}
+	// re-derive the public point Q' = (X,Y) = dG
+	// to compare to declared Q in public key
+	expectedX, expectedY := curve.ScalarBaseMult(d)
+	if X.Cmp(expectedX) != 0 || Y.Cmp(expectedY) != 0 {
+		return errors.KeyInvalidError(fmt.Sprintf("ecc (%s): invalid point", curve.Params().Name))
+	}
+	return nil
+}
+
+func validateEdDSAParameters(priv *ed25519.PrivateKey) error {
+	// In EdDSA, the serialized public point is stored as part of private key (together with the seed),
+	// hence we can re-derive the key from the seed
+	seed := priv.Seed()
+	expectedPriv := ed25519.NewKeyFromSeed(seed)
+	if !bytes.Equal(*priv, expectedPriv) {
+		return errors.KeyInvalidError("eddsa: invalid point")
+	}
+	return nil
+}
+
+func validateDSAParameters(priv *dsa.PrivateKey) error {
+	p := priv.P // group prime
+	q := priv.Q // subgroup order
+	g := priv.G // g has order q mod p
+	x := priv.X // secret
+	y := priv.Y // y == g**x mod p
+	one := big.NewInt(1)
+	// expect g, y >= 2 and g < p
+	if g.Cmp(one) <= 0 || y.Cmp(one) <= 0 || g.Cmp(p) > 0 {
+		return errors.KeyInvalidError("dsa: invalid group")
+	}
+	// expect p > q
+	if p.Cmp(q) <= 0 {
+		return errors.KeyInvalidError("dsa: invalid group prime")
+	}
+	// q should be large enough and divide p-1
+	pSub1 := new(big.Int).Sub(p, one)
+	if q.BitLen() < 150 || new(big.Int).Mod(pSub1, q).Cmp(big.NewInt(0)) != 0 {
+		return errors.KeyInvalidError("dsa: invalid order")
+	}
+	// confirm that g has order q mod p
+	if !q.ProbablyPrime(32) || new(big.Int).Exp(g, q, p).Cmp(one) != 0 {
+		return errors.KeyInvalidError("dsa: invalid order")
+	}
+	// check y
+	if new(big.Int).Exp(g, x, p).Cmp(y) != 0 {
+		return errors.KeyInvalidError("dsa: mismatching values")
+	}
+
+	return nil
+}
+
+func validateElGamalParameters(priv *elgamal.PrivateKey) error {
+	p := priv.P // group prime
+	g := priv.G // g has order p-1 mod p
+	x := priv.X // secret
+	y := priv.Y // y == g**x mod p
+	one := big.NewInt(1)
+	// Expect g, y >= 2 and g < p
+	if g.Cmp(one) <= 0 || y.Cmp(one) <= 0 || g.Cmp(p) > 0 {
+		return errors.KeyInvalidError("elgamal: invalid group")
+	}
+	if p.BitLen() < 1024 {
+		return errors.KeyInvalidError("elgamal: group order too small")
+	}
+	pSub1 := new(big.Int).Sub(p, one)
+	if new(big.Int).Exp(g, pSub1, p).Cmp(one) != 0 {
+		return errors.KeyInvalidError("elgamal: invalid group")
+	}
+	// Since p-1 is not prime, g might have a smaller order that divides p-1.
+	// We cannot confirm the exact order of g, but we make sure it is not too small.
+	gExpI := new(big.Int).Set(g)
+	i := 1
+	threshold := 2 << 17 // we want order > threshold
+	for i < threshold {
+		i++ // we check every order to make sure key validation is not easily bypassed by guessing y'
+		gExpI.Mod(new(big.Int).Mul(gExpI, g), p)
+		if gExpI.Cmp(one) == 0 {
+			return errors.KeyInvalidError("elgamal: order too small")
+		}
+	}
+	// Check y
+	if new(big.Int).Exp(g, x, p).Cmp(y) != 0 {
+		return errors.KeyInvalidError("elgamal: mismatching values")
+	}
+
+	return nil
+}

vendor/github.com/ProtonMail/go-crypto/openpgp/packet/private_key_test_data.go

@@ -0,0 +1,12 @@
+package packet
+
+// Generated with `gpg --export-secret-keys "Test Key 2"`
+const privKeyRSAHex = "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"
+
+// Generated by `gpg --export-secret-keys` followed by a manual extraction of
+// the ElGamal subkey from the packets.
+const privKeyElGamalHex = "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"
+
+// pkcs1PrivKeyHex is a PKCS#1, RSA private key.
+// Generated by `openssl genrsa 1024 | openssl rsa -outform DER  | xxd -p`
+const pkcs1PrivKeyHex = "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"

vendor/github.com/ProtonMail/go-crypto/openpgp/packet/public_key.go

@@ -0,0 +1,825 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"crypto"
+	"crypto/dsa"
+	"crypto/ecdsa"
+	"crypto/elliptic"
+	"crypto/rsa"
+	"crypto/sha1"
+	"crypto/sha256"
+	_ "crypto/sha512"
+	"encoding/binary"
+	"fmt"
+	"hash"
+	"io"
+	"math/big"
+	"strconv"
+	"time"
+
+	"github.com/ProtonMail/go-crypto/openpgp/ecdh"
+	"github.com/ProtonMail/go-crypto/openpgp/elgamal"
+	"github.com/ProtonMail/go-crypto/openpgp/errors"
+	"github.com/ProtonMail/go-crypto/openpgp/internal/algorithm"
+	"github.com/ProtonMail/go-crypto/openpgp/internal/ecc"
+	"github.com/ProtonMail/go-crypto/openpgp/internal/encoding"
+	"golang.org/x/crypto/ed25519"
+)
+
+type kdfHashFunction byte
+type kdfAlgorithm byte
+
+// PublicKey represents an OpenPGP public key. See RFC 4880, section 5.5.2.
+type PublicKey struct {
+	Version      int
+	CreationTime time.Time
+	PubKeyAlgo   PublicKeyAlgorithm
+	PublicKey    interface{} // *rsa.PublicKey, *dsa.PublicKey, *ecdsa.PublicKey or *eddsa.PublicKey
+	Fingerprint  []byte
+	KeyId        uint64
+	IsSubkey     bool
+
+	// RFC 4880 fields
+	n, e, p, q, g, y encoding.Field
+
+	// RFC 6637 fields
+	// oid contains the OID byte sequence identifying the elliptic curve used
+	oid encoding.Field
+
+	// kdf stores key derivation function parameters
+	// used for ECDH encryption. See RFC 6637, Section 9.
+	kdf encoding.Field
+}
+
+// UpgradeToV5 updates the version of the key to v5, and updates all necessary
+// fields.
+func (pk *PublicKey) UpgradeToV5() {
+	pk.Version = 5
+	pk.setFingerprintAndKeyId()
+}
+
+// signingKey provides a convenient abstraction over signature verification
+// for v3 and v4 public keys.
+type signingKey interface {
+	SerializeForHash(io.Writer) error
+	SerializeSignaturePrefix(io.Writer)
+	serializeWithoutHeaders(io.Writer) error
+}
+
+// NewRSAPublicKey returns a PublicKey that wraps the given rsa.PublicKey.
+func NewRSAPublicKey(creationTime time.Time, pub *rsa.PublicKey) *PublicKey {
+	pk := &PublicKey{
+		Version:      4,
+		CreationTime: creationTime,
+		PubKeyAlgo:   PubKeyAlgoRSA,
+		PublicKey:    pub,
+		n:            new(encoding.MPI).SetBig(pub.N),
+		e:            new(encoding.MPI).SetBig(big.NewInt(int64(pub.E))),
+	}
+
+	pk.setFingerprintAndKeyId()
+	return pk
+}
+
+// NewDSAPublicKey returns a PublicKey that wraps the given dsa.PublicKey.
+func NewDSAPublicKey(creationTime time.Time, pub *dsa.PublicKey) *PublicKey {
+	pk := &PublicKey{
+		Version:      4,
+		CreationTime: creationTime,
+		PubKeyAlgo:   PubKeyAlgoDSA,
+		PublicKey:    pub,
+		p:            new(encoding.MPI).SetBig(pub.P),
+		q:            new(encoding.MPI).SetBig(pub.Q),
+		g:            new(encoding.MPI).SetBig(pub.G),
+		y:            new(encoding.MPI).SetBig(pub.Y),
+	}
+
+	pk.setFingerprintAndKeyId()
+	return pk
+}
+
+// NewElGamalPublicKey returns a PublicKey that wraps the given elgamal.PublicKey.
+func NewElGamalPublicKey(creationTime time.Time, pub *elgamal.PublicKey) *PublicKey {
+	pk := &PublicKey{
+		Version:      4,
+		CreationTime: creationTime,
+		PubKeyAlgo:   PubKeyAlgoElGamal,
+		PublicKey:    pub,
+		p:            new(encoding.MPI).SetBig(pub.P),
+		g:            new(encoding.MPI).SetBig(pub.G),
+		y:            new(encoding.MPI).SetBig(pub.Y),
+	}
+
+	pk.setFingerprintAndKeyId()
+	return pk
+}
+
+func NewECDSAPublicKey(creationTime time.Time, pub *ecdsa.PublicKey) *PublicKey {
+	pk := &PublicKey{
+		Version:      4,
+		CreationTime: creationTime,
+		PubKeyAlgo:   PubKeyAlgoECDSA,
+		PublicKey:    pub,
+		p:            encoding.NewMPI(elliptic.Marshal(pub.Curve, pub.X, pub.Y)),
+	}
+
+	curveInfo := ecc.FindByCurve(pub.Curve)
+	if curveInfo == nil {
+		panic("unknown elliptic curve")
+	}
+	pk.oid = curveInfo.Oid
+	pk.setFingerprintAndKeyId()
+	return pk
+}
+
+func NewECDHPublicKey(creationTime time.Time, pub *ecdh.PublicKey) *PublicKey {
+	var pk *PublicKey
+	var curveInfo *ecc.CurveInfo
+	var kdf = encoding.NewOID([]byte{0x1, pub.Hash.Id(), pub.Cipher.Id()})
+	if pub.CurveType == ecc.Curve25519 {
+		pk = &PublicKey{
+			Version:      4,
+			CreationTime: creationTime,
+			PubKeyAlgo:   PubKeyAlgoECDH,
+			PublicKey:    pub,
+			p:            encoding.NewMPI(pub.X.Bytes()),
+			kdf:          kdf,
+		}
+		curveInfo = ecc.FindByName("Curve25519")
+	} else {
+		pk = &PublicKey{
+			Version:      4,
+			CreationTime: creationTime,
+			PubKeyAlgo:   PubKeyAlgoECDH,
+			PublicKey:    pub,
+			p:            encoding.NewMPI(elliptic.Marshal(pub.Curve, pub.X, pub.Y)),
+			kdf:          kdf,
+		}
+		curveInfo = ecc.FindByCurve(pub.Curve)
+	}
+	if curveInfo == nil {
+		panic("unknown elliptic curve")
+	}
+	pk.oid = curveInfo.Oid
+	pk.setFingerprintAndKeyId()
+	return pk
+}
+
+func NewEdDSAPublicKey(creationTime time.Time, pub *ed25519.PublicKey) *PublicKey {
+	curveInfo := ecc.FindByName("Ed25519")
+	pk := &PublicKey{
+		Version:      4,
+		CreationTime: creationTime,
+		PubKeyAlgo:   PubKeyAlgoEdDSA,
+		PublicKey:    pub,
+		oid:          curveInfo.Oid,
+		// Native point format, see draft-koch-eddsa-for-openpgp-04, Appendix B
+		p: encoding.NewMPI(append([]byte{0x40}, *pub...)),
+	}
+
+	pk.setFingerprintAndKeyId()
+	return pk
+}
+
+func (pk *PublicKey) parse(r io.Reader) (err error) {
+	// RFC 4880, section 5.5.2
+	var buf [6]byte
+	_, err = readFull(r, buf[:])
+	if err != nil {
+		return
+	}
+	if buf[0] != 4 && buf[0] != 5 {
+		return errors.UnsupportedError("public key version " + strconv.Itoa(int(buf[0])))
+	}
+
+	pk.Version = int(buf[0])
+	if pk.Version == 5 {
+		var n [4]byte
+		_, err = readFull(r, n[:])
+		if err != nil {
+			return
+		}
+	}
+	pk.CreationTime = time.Unix(int64(uint32(buf[1])<<24|uint32(buf[2])<<16|uint32(buf[3])<<8|uint32(buf[4])), 0)
+	pk.PubKeyAlgo = PublicKeyAlgorithm(buf[5])
+	switch pk.PubKeyAlgo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoRSASignOnly:
+		err = pk.parseRSA(r)
+	case PubKeyAlgoDSA:
+		err = pk.parseDSA(r)
+	case PubKeyAlgoElGamal:
+		err = pk.parseElGamal(r)
+	case PubKeyAlgoECDSA:
+		err = pk.parseECDSA(r)
+	case PubKeyAlgoECDH:
+		err = pk.parseECDH(r)
+	case PubKeyAlgoEdDSA:
+		err = pk.parseEdDSA(r)
+	default:
+		err = errors.UnsupportedError("public key type: " + strconv.Itoa(int(pk.PubKeyAlgo)))
+	}
+	if err != nil {
+		return
+	}
+
+	pk.setFingerprintAndKeyId()
+	return
+}
+
+func (pk *PublicKey) setFingerprintAndKeyId() {
+	// RFC 4880, section 12.2
+	if pk.Version == 5 {
+		fingerprint := sha256.New()
+		pk.SerializeForHash(fingerprint)
+		pk.Fingerprint = make([]byte, 32)
+		copy(pk.Fingerprint, fingerprint.Sum(nil))
+		pk.KeyId = binary.BigEndian.Uint64(pk.Fingerprint[:8])
+	} else {
+		fingerprint := sha1.New()
+		pk.SerializeForHash(fingerprint)
+		pk.Fingerprint = make([]byte, 20)
+		copy(pk.Fingerprint, fingerprint.Sum(nil))
+		pk.KeyId = binary.BigEndian.Uint64(pk.Fingerprint[12:20])
+	}
+}
+
+// parseRSA parses RSA public key material from the given Reader. See RFC 4880,
+// section 5.5.2.
+func (pk *PublicKey) parseRSA(r io.Reader) (err error) {
+	pk.n = new(encoding.MPI)
+	if _, err = pk.n.ReadFrom(r); err != nil {
+		return
+	}
+	pk.e = new(encoding.MPI)
+	if _, err = pk.e.ReadFrom(r); err != nil {
+		return
+	}
+
+	if len(pk.e.Bytes()) > 3 {
+		err = errors.UnsupportedError("large public exponent")
+		return
+	}
+	rsa := &rsa.PublicKey{
+		N: new(big.Int).SetBytes(pk.n.Bytes()),
+		E: 0,
+	}
+	for i := 0; i < len(pk.e.Bytes()); i++ {
+		rsa.E <<= 8
+		rsa.E |= int(pk.e.Bytes()[i])
+	}
+	pk.PublicKey = rsa
+	return
+}
+
+// parseDSA parses DSA public key material from the given Reader. See RFC 4880,
+// section 5.5.2.
+func (pk *PublicKey) parseDSA(r io.Reader) (err error) {
+	pk.p = new(encoding.MPI)
+	if _, err = pk.p.ReadFrom(r); err != nil {
+		return
+	}
+	pk.q = new(encoding.MPI)
+	if _, err = pk.q.ReadFrom(r); err != nil {
+		return
+	}
+	pk.g = new(encoding.MPI)
+	if _, err = pk.g.ReadFrom(r); err != nil {
+		return
+	}
+	pk.y = new(encoding.MPI)
+	if _, err = pk.y.ReadFrom(r); err != nil {
+		return
+	}
+
+	dsa := new(dsa.PublicKey)
+	dsa.P = new(big.Int).SetBytes(pk.p.Bytes())
+	dsa.Q = new(big.Int).SetBytes(pk.q.Bytes())
+	dsa.G = new(big.Int).SetBytes(pk.g.Bytes())
+	dsa.Y = new(big.Int).SetBytes(pk.y.Bytes())
+	pk.PublicKey = dsa
+	return
+}
+
+// parseElGamal parses ElGamal public key material from the given Reader. See
+// RFC 4880, section 5.5.2.
+func (pk *PublicKey) parseElGamal(r io.Reader) (err error) {
+	pk.p = new(encoding.MPI)
+	if _, err = pk.p.ReadFrom(r); err != nil {
+		return
+	}
+	pk.g = new(encoding.MPI)
+	if _, err = pk.g.ReadFrom(r); err != nil {
+		return
+	}
+	pk.y = new(encoding.MPI)
+	if _, err = pk.y.ReadFrom(r); err != nil {
+		return
+	}
+
+	elgamal := new(elgamal.PublicKey)
+	elgamal.P = new(big.Int).SetBytes(pk.p.Bytes())
+	elgamal.G = new(big.Int).SetBytes(pk.g.Bytes())
+	elgamal.Y = new(big.Int).SetBytes(pk.y.Bytes())
+	pk.PublicKey = elgamal
+	return
+}
+
+// parseECDSA parses ECDSA public key material from the given Reader. See
+// RFC 6637, Section 9.
+func (pk *PublicKey) parseECDSA(r io.Reader) (err error) {
+	pk.oid = new(encoding.OID)
+	if _, err = pk.oid.ReadFrom(r); err != nil {
+		return
+	}
+	pk.p = new(encoding.MPI)
+	if _, err = pk.p.ReadFrom(r); err != nil {
+		return
+	}
+
+	var c elliptic.Curve
+	curveInfo := ecc.FindByOid(pk.oid)
+	if curveInfo == nil || curveInfo.SigAlgorithm != ecc.ECDSA {
+		return errors.UnsupportedError(fmt.Sprintf("unsupported oid: %x", pk.oid))
+	}
+	c = curveInfo.Curve
+	x, y := elliptic.Unmarshal(c, pk.p.Bytes())
+	if x == nil {
+		return errors.UnsupportedError("failed to parse EC point")
+	}
+	pk.PublicKey = &ecdsa.PublicKey{Curve: c, X: x, Y: y}
+	return
+}
+
+// parseECDH parses ECDH public key material from the given Reader. See
+// RFC 6637, Section 9.
+func (pk *PublicKey) parseECDH(r io.Reader) (err error) {
+	pk.oid = new(encoding.OID)
+	if _, err = pk.oid.ReadFrom(r); err != nil {
+		return
+	}
+	pk.p = new(encoding.MPI)
+	if _, err = pk.p.ReadFrom(r); err != nil {
+		return
+	}
+	pk.kdf = new(encoding.OID)
+	if _, err = pk.kdf.ReadFrom(r); err != nil {
+		return
+	}
+
+	curveInfo := ecc.FindByOid(pk.oid)
+	if curveInfo == nil {
+		return errors.UnsupportedError(fmt.Sprintf("unsupported oid: %x", pk.oid))
+	}
+
+	c := curveInfo.Curve
+	cType := curveInfo.CurveType
+
+	var x, y *big.Int
+	if cType == ecc.Curve25519 {
+		x = new(big.Int)
+		x.SetBytes(pk.p.Bytes())
+	} else {
+		x, y = elliptic.Unmarshal(c, pk.p.Bytes())
+	}
+	if x == nil {
+		return errors.UnsupportedError("failed to parse EC point")
+	}
+
+	if kdfLen := len(pk.kdf.Bytes()); kdfLen < 3 {
+		return errors.UnsupportedError("unsupported ECDH KDF length: " + strconv.Itoa(kdfLen))
+	}
+	if reserved := pk.kdf.Bytes()[0]; reserved != 0x01 {
+		return errors.UnsupportedError("unsupported KDF reserved field: " + strconv.Itoa(int(reserved)))
+	}
+	kdfHash, ok := algorithm.HashById[pk.kdf.Bytes()[1]]
+	if !ok {
+		return errors.UnsupportedError("unsupported ECDH KDF hash: " + strconv.Itoa(int(pk.kdf.Bytes()[1])))
+	}
+	kdfCipher, ok := algorithm.CipherById[pk.kdf.Bytes()[2]]
+	if !ok {
+		return errors.UnsupportedError("unsupported ECDH KDF cipher: " + strconv.Itoa(int(pk.kdf.Bytes()[2])))
+	}
+
+	pk.PublicKey = &ecdh.PublicKey{
+		CurveType: cType,
+		Curve:     c,
+		X:         x,
+		Y:         y,
+		KDF: ecdh.KDF{
+			Hash:   kdfHash,
+			Cipher: kdfCipher,
+		},
+	}
+	return
+}
+
+func (pk *PublicKey) parseEdDSA(r io.Reader) (err error) {
+	pk.oid = new(encoding.OID)
+	if _, err = pk.oid.ReadFrom(r); err != nil {
+		return
+	}
+	curveInfo := ecc.FindByOid(pk.oid)
+	if curveInfo == nil || curveInfo.SigAlgorithm != ecc.EdDSA {
+		return errors.UnsupportedError(fmt.Sprintf("unsupported oid: %x", pk.oid))
+	}
+	pk.p = new(encoding.MPI)
+	if _, err = pk.p.ReadFrom(r); err != nil {
+		return
+	}
+
+	eddsa := make(ed25519.PublicKey, ed25519.PublicKeySize)
+	switch flag := pk.p.Bytes()[0]; flag {
+	case 0x04:
+		// TODO: see _grcy_ecc_eddsa_ensure_compact in grcypt
+		return errors.UnsupportedError("unsupported EdDSA compression: " + strconv.Itoa(int(flag)))
+	case 0x40:
+		copy(eddsa[:], pk.p.Bytes()[1:])
+	default:
+		return errors.UnsupportedError("unsupported EdDSA compression: " + strconv.Itoa(int(flag)))
+	}
+
+	pk.PublicKey = &eddsa
+	return
+}
+
+// SerializeForHash serializes the PublicKey to w with the special packet
+// header format needed for hashing.
+func (pk *PublicKey) SerializeForHash(w io.Writer) error {
+	pk.SerializeSignaturePrefix(w)
+	return pk.serializeWithoutHeaders(w)
+}
+
+// SerializeSignaturePrefix writes the prefix for this public key to the given Writer.
+// The prefix is used when calculating a signature over this public key. See
+// RFC 4880, section 5.2.4.
+func (pk *PublicKey) SerializeSignaturePrefix(w io.Writer) {
+	var pLength = pk.algorithmSpecificByteCount()
+	if pk.Version == 5 {
+		pLength += 10 // version, timestamp (4), algorithm, key octet count (4).
+		w.Write([]byte{
+			0x9A,
+			byte(pLength >> 24),
+			byte(pLength >> 16),
+			byte(pLength >> 8),
+			byte(pLength),
+		})
+		return
+	}
+	pLength += 6
+	w.Write([]byte{0x99, byte(pLength >> 8), byte(pLength)})
+}
+
+func (pk *PublicKey) Serialize(w io.Writer) (err error) {
+	length := 6 // 6 byte header
+	length += pk.algorithmSpecificByteCount()
+	if pk.Version == 5 {
+		length += 4 // octet key count
+	}
+	packetType := packetTypePublicKey
+	if pk.IsSubkey {
+		packetType = packetTypePublicSubkey
+	}
+	err = serializeHeader(w, packetType, length)
+	if err != nil {
+		return
+	}
+	return pk.serializeWithoutHeaders(w)
+}
+
+func (pk *PublicKey) algorithmSpecificByteCount() int {
+	length := 0
+	switch pk.PubKeyAlgo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoRSASignOnly:
+		length += int(pk.n.EncodedLength())
+		length += int(pk.e.EncodedLength())
+	case PubKeyAlgoDSA:
+		length += int(pk.p.EncodedLength())
+		length += int(pk.q.EncodedLength())
+		length += int(pk.g.EncodedLength())
+		length += int(pk.y.EncodedLength())
+	case PubKeyAlgoElGamal:
+		length += int(pk.p.EncodedLength())
+		length += int(pk.g.EncodedLength())
+		length += int(pk.y.EncodedLength())
+	case PubKeyAlgoECDSA:
+		length += int(pk.oid.EncodedLength())
+		length += int(pk.p.EncodedLength())
+	case PubKeyAlgoECDH:
+		length += int(pk.oid.EncodedLength())
+		length += int(pk.p.EncodedLength())
+		length += int(pk.kdf.EncodedLength())
+	case PubKeyAlgoEdDSA:
+		length += int(pk.oid.EncodedLength())
+		length += int(pk.p.EncodedLength())
+	default:
+		panic("unknown public key algorithm")
+	}
+	return length
+}
+
+// serializeWithoutHeaders marshals the PublicKey to w in the form of an
+// OpenPGP public key packet, not including the packet header.
+func (pk *PublicKey) serializeWithoutHeaders(w io.Writer) (err error) {
+	t := uint32(pk.CreationTime.Unix())
+	if _, err = w.Write([]byte{
+		byte(pk.Version),
+		byte(t >> 24), byte(t >> 16), byte(t >> 8), byte(t),
+		byte(pk.PubKeyAlgo),
+	}); err != nil {
+		return
+	}
+
+	if pk.Version == 5 {
+		n := pk.algorithmSpecificByteCount()
+		if _, err = w.Write([]byte{
+			byte(n >> 24), byte(n >> 16), byte(n >> 8), byte(n),
+		}); err != nil {
+			return
+		}
+	}
+
+	switch pk.PubKeyAlgo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoRSASignOnly:
+		if _, err = w.Write(pk.n.EncodedBytes()); err != nil {
+			return
+		}
+		_, err = w.Write(pk.e.EncodedBytes())
+		return
+	case PubKeyAlgoDSA:
+		if _, err = w.Write(pk.p.EncodedBytes()); err != nil {
+			return
+		}
+		if _, err = w.Write(pk.q.EncodedBytes()); err != nil {
+			return
+		}
+		if _, err = w.Write(pk.g.EncodedBytes()); err != nil {
+			return
+		}
+		_, err = w.Write(pk.y.EncodedBytes())
+		return
+	case PubKeyAlgoElGamal:
+		if _, err = w.Write(pk.p.EncodedBytes()); err != nil {
+			return
+		}
+		if _, err = w.Write(pk.g.EncodedBytes()); err != nil {
+			return
+		}
+		_, err = w.Write(pk.y.EncodedBytes())
+		return
+	case PubKeyAlgoECDSA:
+		if _, err = w.Write(pk.oid.EncodedBytes()); err != nil {
+			return
+		}
+		_, err = w.Write(pk.p.EncodedBytes())
+		return
+	case PubKeyAlgoECDH:
+		if _, err = w.Write(pk.oid.EncodedBytes()); err != nil {
+			return
+		}
+		if _, err = w.Write(pk.p.EncodedBytes()); err != nil {
+			return
+		}
+		_, err = w.Write(pk.kdf.EncodedBytes())
+		return
+	case PubKeyAlgoEdDSA:
+		if _, err = w.Write(pk.oid.EncodedBytes()); err != nil {
+			return
+		}
+		_, err = w.Write(pk.p.EncodedBytes())
+		return
+	}
+	return errors.InvalidArgumentError("bad public-key algorithm")
+}
+
+// CanSign returns true iff this public key can generate signatures
+func (pk *PublicKey) CanSign() bool {
+	return pk.PubKeyAlgo != PubKeyAlgoRSAEncryptOnly && pk.PubKeyAlgo != PubKeyAlgoElGamal && pk.PubKeyAlgo != PubKeyAlgoECDH
+}
+
+// VerifySignature returns nil iff sig is a valid signature, made by this
+// public key, of the data hashed into signed. signed is mutated by this call.
+func (pk *PublicKey) VerifySignature(signed hash.Hash, sig *Signature) (err error) {
+	if !pk.CanSign() {
+		return errors.InvalidArgumentError("public key cannot generate signatures")
+	}
+	if sig.Version == 5 && (sig.SigType == 0x00 || sig.SigType == 0x01) {
+		sig.AddMetadataToHashSuffix()
+	}
+	signed.Write(sig.HashSuffix)
+	hashBytes := signed.Sum(nil)
+	if hashBytes[0] != sig.HashTag[0] || hashBytes[1] != sig.HashTag[1] {
+		return errors.SignatureError("hash tag doesn't match")
+	}
+
+	if pk.PubKeyAlgo != sig.PubKeyAlgo {
+		return errors.InvalidArgumentError("public key and signature use different algorithms")
+	}
+
+	switch pk.PubKeyAlgo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly:
+		rsaPublicKey, _ := pk.PublicKey.(*rsa.PublicKey)
+		err = rsa.VerifyPKCS1v15(rsaPublicKey, sig.Hash, hashBytes, padToKeySize(rsaPublicKey, sig.RSASignature.Bytes()))
+		if err != nil {
+			return errors.SignatureError("RSA verification failure")
+		}
+		return nil
+	case PubKeyAlgoDSA:
+		dsaPublicKey, _ := pk.PublicKey.(*dsa.PublicKey)
+		// Need to truncate hashBytes to match FIPS 186-3 section 4.6.
+		subgroupSize := (dsaPublicKey.Q.BitLen() + 7) / 8
+		if len(hashBytes) > subgroupSize {
+			hashBytes = hashBytes[:subgroupSize]
+		}
+		if !dsa.Verify(dsaPublicKey, hashBytes, new(big.Int).SetBytes(sig.DSASigR.Bytes()), new(big.Int).SetBytes(sig.DSASigS.Bytes())) {
+			return errors.SignatureError("DSA verification failure")
+		}
+		return nil
+	case PubKeyAlgoECDSA:
+		ecdsaPublicKey := pk.PublicKey.(*ecdsa.PublicKey)
+		if !ecdsa.Verify(ecdsaPublicKey, hashBytes, new(big.Int).SetBytes(sig.ECDSASigR.Bytes()), new(big.Int).SetBytes(sig.ECDSASigS.Bytes())) {
+			return errors.SignatureError("ECDSA verification failure")
+		}
+		return nil
+	case PubKeyAlgoEdDSA:
+		eddsaPublicKey := pk.PublicKey.(*ed25519.PublicKey)
+
+		sigR := sig.EdDSASigR.Bytes()
+		sigS := sig.EdDSASigS.Bytes()
+
+		eddsaSig := make([]byte, ed25519.SignatureSize)
+		copy(eddsaSig[32-len(sigR):32], sigR)
+		copy(eddsaSig[64-len(sigS):], sigS)
+
+		if !ed25519.Verify(*eddsaPublicKey, hashBytes, eddsaSig) {
+			return errors.SignatureError("EdDSA verification failure")
+		}
+		return nil
+	default:
+		return errors.SignatureError("Unsupported public key algorithm used in signature")
+	}
+}
+
+// keySignatureHash returns a Hash of the message that needs to be signed for
+// pk to assert a subkey relationship to signed.
+func keySignatureHash(pk, signed signingKey, hashFunc crypto.Hash) (h hash.Hash, err error) {
+	if !hashFunc.Available() {
+		return nil, errors.UnsupportedError("hash function")
+	}
+	h = hashFunc.New()
+
+	// RFC 4880, section 5.2.4
+	err = pk.SerializeForHash(h)
+	if err != nil {
+		return nil, err
+	}
+
+	err = signed.SerializeForHash(h)
+	return
+}
+
+// VerifyKeySignature returns nil iff sig is a valid signature, made by this
+// public key, of signed.
+func (pk *PublicKey) VerifyKeySignature(signed *PublicKey, sig *Signature) error {
+	h, err := keySignatureHash(pk, signed, sig.Hash)
+	if err != nil {
+		return err
+	}
+	if err = pk.VerifySignature(h, sig); err != nil {
+		return err
+	}
+
+	if sig.FlagSign {
+		// Signing subkeys must be cross-signed. See
+		// https://www.gnupg.org/faq/subkey-cross-certify.html.
+		if sig.EmbeddedSignature == nil {
+			return errors.StructuralError("signing subkey is missing cross-signature")
+		}
+		// Verify the cross-signature. This is calculated over the same
+		// data as the main signature, so we cannot just recursively
+		// call signed.VerifyKeySignature(...)
+		if h, err = keySignatureHash(pk, signed, sig.EmbeddedSignature.Hash); err != nil {
+			return errors.StructuralError("error while hashing for cross-signature: " + err.Error())
+		}
+		if err := signed.VerifySignature(h, sig.EmbeddedSignature); err != nil {
+			return errors.StructuralError("error while verifying cross-signature: " + err.Error())
+		}
+	}
+
+	return nil
+}
+
+func keyRevocationHash(pk signingKey, hashFunc crypto.Hash) (h hash.Hash, err error) {
+	if !hashFunc.Available() {
+		return nil, errors.UnsupportedError("hash function")
+	}
+	h = hashFunc.New()
+
+	// RFC 4880, section 5.2.4
+	err = pk.SerializeForHash(h)
+
+	return
+}
+
+// VerifyRevocationSignature returns nil iff sig is a valid signature, made by this
+// public key.
+func (pk *PublicKey) VerifyRevocationSignature(sig *Signature) (err error) {
+	h, err := keyRevocationHash(pk, sig.Hash)
+	if err != nil {
+		return err
+	}
+	return pk.VerifySignature(h, sig)
+}
+
+// VerifySubkeyRevocationSignature returns nil iff sig is a valid subkey revocation signature,
+// made by the passed in signingKey.
+func (pk *PublicKey) VerifySubkeyRevocationSignature(sig *Signature, signingKey *PublicKey) (err error) {
+	h, err := keyRevocationHash(pk, sig.Hash)
+	if err != nil {
+		return err
+	}
+	return signingKey.VerifySignature(h, sig)
+}
+
+// userIdSignatureHash returns a Hash of the message that needs to be signed
+// to assert that pk is a valid key for id.
+func userIdSignatureHash(id string, pk *PublicKey, hashFunc crypto.Hash) (h hash.Hash, err error) {
+	if !hashFunc.Available() {
+		return nil, errors.UnsupportedError("hash function")
+	}
+	h = hashFunc.New()
+
+	// RFC 4880, section 5.2.4
+	pk.SerializeSignaturePrefix(h)
+	pk.serializeWithoutHeaders(h)
+
+	var buf [5]byte
+	buf[0] = 0xb4
+	buf[1] = byte(len(id) >> 24)
+	buf[2] = byte(len(id) >> 16)
+	buf[3] = byte(len(id) >> 8)
+	buf[4] = byte(len(id))
+	h.Write(buf[:])
+	h.Write([]byte(id))
+
+	return
+}
+
+// VerifyUserIdSignature returns nil iff sig is a valid signature, made by this
+// public key, that id is the identity of pub.
+func (pk *PublicKey) VerifyUserIdSignature(id string, pub *PublicKey, sig *Signature) (err error) {
+	h, err := userIdSignatureHash(id, pub, sig.Hash)
+	if err != nil {
+		return err
+	}
+	return pk.VerifySignature(h, sig)
+}
+
+// KeyIdString returns the public key's fingerprint in capital hex
+// (e.g. "6C7EE1B8621CC013").
+func (pk *PublicKey) KeyIdString() string {
+	return fmt.Sprintf("%X", pk.Fingerprint[12:20])
+}
+
+// KeyIdShortString returns the short form of public key's fingerprint
+// in capital hex, as shown by gpg --list-keys (e.g. "621CC013").
+func (pk *PublicKey) KeyIdShortString() string {
+	return fmt.Sprintf("%X", pk.Fingerprint[16:20])
+}
+
+// BitLength returns the bit length for the given public key.
+func (pk *PublicKey) BitLength() (bitLength uint16, err error) {
+	switch pk.PubKeyAlgo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoRSASignOnly:
+		bitLength = pk.n.BitLength()
+	case PubKeyAlgoDSA:
+		bitLength = pk.p.BitLength()
+	case PubKeyAlgoElGamal:
+		bitLength = pk.p.BitLength()
+	case PubKeyAlgoECDSA:
+		bitLength = pk.p.BitLength()
+	case PubKeyAlgoECDH:
+		bitLength = pk.p.BitLength()
+	case PubKeyAlgoEdDSA:
+		bitLength = pk.p.BitLength()
+	default:
+		err = errors.InvalidArgumentError("bad public-key algorithm")
+	}
+	return
+}
+
+// KeyExpired returns whether sig is a self-signature of a key that has
+// expired or is created in the future.
+func (pk *PublicKey) KeyExpired(sig *Signature, currentTime time.Time) bool {
+	if pk.CreationTime.After(currentTime) {
+		return true
+	}
+	if sig.KeyLifetimeSecs == nil || *sig.KeyLifetimeSecs == 0 {
+		return false
+	}
+	expiry := pk.CreationTime.Add(time.Duration(*sig.KeyLifetimeSecs) * time.Second)
+	return currentTime.After(expiry)
+}

vendor/github.com/ProtonMail/go-crypto/openpgp/packet/public_key_test_data.go

@@ -0,0 +1,24 @@
+package packet
+
+const rsaFingerprintHex = "5fb74b1d03b1e3cb31bc2f8aa34d7e18c20c31bb"
+
+const rsaPkDataHex = "988d044d3c5c10010400b1d13382944bd5aba23a4312968b5095d14f947f600eb478e14a6fcb16b0e0cac764884909c020bc495cfcc39a935387c661507bdb236a0612fb582cac3af9b29cc2c8c70090616c41b662f4da4c1201e195472eb7f4ae1ccbcbf9940fe21d985e379a5563dde5b9a23d35f1cfaa5790da3b79db26f23695107bfaca8e7b5bcd0011010001"
+
+const dsaFingerprintHex = "eece4c094db002103714c63c8e8fbe54062f19ed"
+
+const dsaPkDataHex = "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"
+
+const ecdsaFingerprintHex = "9892270b38b8980b05c8d56d43fe956c542ca00b"
+
+const ecdsaPkDataHex = "9893045071c29413052b8104002304230401f4867769cedfa52c325018896245443968e52e51d0c2df8d939949cb5b330f2921711fbee1c9b9dddb95d15cb0255e99badeddda7cc23d9ddcaacbc290969b9f24019375d61c2e4e3b36953a28d8b2bc95f78c3f1d592fb24499be348656a7b17e3963187b4361afe497bc5f9f81213f04069f8e1fb9e6a6290ae295ca1a92b894396cb4"
+
+const ecdhFingerprintHex = "722354df2475a42164d1d49faa8b938f9a201946"
+
+const ecdhPkDataHex = "b90073044d53059212052b810400220303042faa84024a20b6735c4897efa5bfb41bf85b7eefeab5ca0cb9ffc8ea04a46acb25534a577694f9e25340a4ab5223a9dd1eda530c8aa2e6718db10d7e672558c7736fe09369ea5739a2a3554bf16d41faa50562f11c6d39bbd5dffb6b9a9ec91803010909"
+
+const eddsaFingerprintHex = "b2d5e5ec0e6deca6bc8eeeb00907e75e1dd99ad8"
+
+const eddsaPkDataHex = "98330456e2132b16092b06010401da470f01010740bbda39266affa511a8c2d02edf690fb784b0499c4406185811a163539ef11dc1b41d74657374696e67203c74657374696e674074657374696e672e636f6d3e8879041316080021050256e2132b021b03050b09080702061508090a0b020416020301021e01021780000a09100907e75e1dd99ad86d0c00fe39d2008359352782bc9b61ac382584cd8eff3f57a18c2287e3afeeb05d1f04ba00fe2d0bc1ddf3ff8adb9afa3e7d9287244b4ec567f3db4d60b74a9b5465ed528203"
+
+// Source: https://sites.google.com/site/brainhub/pgpecckeys#TOC-ECC-NIST-P-384-key
+const ecc384PubHex = `99006f044d53059213052b81040022030304f6b8c5aced5b84ef9f4a209db2e4a9dfb70d28cb8c10ecd57674a9fa5a67389942b62d5e51367df4c7bfd3f8e500feecf07ed265a621a8ebbbe53e947ec78c677eba143bd1533c2b350e1c29f82313e1e1108eba063be1e64b10e6950e799c2db42465635f6473615f64685f333834203c6f70656e70677040627261696e6875622e6f72673e8900cb04101309005305024d530592301480000000002000077072656665727265642d656d61696c2d656e636f64696e67407067702e636f6d7067706d696d65040b090807021901051b03000000021602051e010000000415090a08000a0910098033880f54719fca2b0180aa37350968bd5f115afd8ce7bc7b103822152dbff06d0afcda835329510905b98cb469ba208faab87c7412b799e7b633017f58364ea480e8a1a3f253a0c5f22c446e8be9a9fce6210136ee30811abbd49139de28b5bdf8dc36d06ae748579e9ff503b90073044d53059212052b810400220303042faa84024a20b6735c4897efa5bfb41bf85b7eefeab5ca0cb9ffc8ea04a46acb25534a577694f9e25340a4ab5223a9dd1eda530c8aa2e6718db10d7e672558c7736fe09369ea5739a2a3554bf16d41faa50562f11c6d39bbd5dffb6b9a9ec9180301090989008404181309000c05024d530592051b0c000000000a0910098033880f54719f80970180eee7a6d8fcee41ee4f9289df17f9bcf9d955dca25c583b94336f3a2b2d4986dc5cf417b8d2dc86f741a9e1a6d236c0e3017d1c76575458a0cfb93ae8a2b274fcc65ceecd7a91eec83656ba13219969f06945b48c56bd04152c3a0553c5f2f4bd1267`

vendor/github.com/ProtonMail/go-crypto/openpgp/packet/reader.go

@@ -0,0 +1,78 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"io"
+
+	"github.com/ProtonMail/go-crypto/openpgp/errors"
+)
+
+// Reader reads packets from an io.Reader and allows packets to be 'unread' so
+// that they result from the next call to Next.
+type Reader struct {
+	q       []Packet
+	readers []io.Reader
+}
+
+// New io.Readers are pushed when a compressed or encrypted packet is processed
+// and recursively treated as a new source of packets. However, a carefully
+// crafted packet can trigger an infinite recursive sequence of packets. See
+// http://mumble.net/~campbell/misc/pgp-quine
+// https://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2013-4402
+// This constant limits the number of recursive packets that may be pushed.
+const maxReaders = 32
+
+// Next returns the most recently unread Packet, or reads another packet from
+// the top-most io.Reader. Unknown packet types are skipped.
+func (r *Reader) Next() (p Packet, err error) {
+	if len(r.q) > 0 {
+		p = r.q[len(r.q)-1]
+		r.q = r.q[:len(r.q)-1]
+		return
+	}
+
+	for len(r.readers) > 0 {
+		p, err = Read(r.readers[len(r.readers)-1])
+		if err == nil {
+			return
+		}
+		if err == io.EOF {
+			r.readers = r.readers[:len(r.readers)-1]
+			continue
+		}
+		// TODO: Add strict mode that rejects unknown packets, instead of ignoring them.
+		if _, ok := err.(errors.UnknownPacketTypeError); !ok {
+			return nil, err
+		}
+	}
+
+	return nil, io.EOF
+}
+
+// Push causes the Reader to start reading from a new io.Reader. When an EOF
+// error is seen from the new io.Reader, it is popped and the Reader continues
+// to read from the next most recent io.Reader. Push returns a StructuralError
+// if pushing the reader would exceed the maximum recursion level, otherwise it
+// returns nil.
+func (r *Reader) Push(reader io.Reader) (err error) {
+	if len(r.readers) >= maxReaders {
+		return errors.StructuralError("too many layers of packets")
+	}
+	r.readers = append(r.readers, reader)
+	return nil
+}
+
+// Unread causes the given Packet to be returned from the next call to Next.
+func (r *Reader) Unread(p Packet) {
+	r.q = append(r.q, p)
+}
+
+func NewReader(r io.Reader) *Reader {
+	return &Reader{
+		q:       nil,
+		readers: []io.Reader{r},
+	}
+}

vendor/github.com/ProtonMail/go-crypto/openpgp/packet/signature.go

@@ -0,0 +1,983 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"bytes"
+	"crypto"
+	"crypto/dsa"
+	"crypto/ecdsa"
+	"encoding/asn1"
+	"encoding/binary"
+	"hash"
+	"io"
+	"math/big"
+	"strconv"
+	"time"
+
+	"github.com/ProtonMail/go-crypto/openpgp/errors"
+	"github.com/ProtonMail/go-crypto/openpgp/internal/encoding"
+	"github.com/ProtonMail/go-crypto/openpgp/s2k"
+)
+
+const (
+	// See RFC 4880, section 5.2.3.21 for details.
+	KeyFlagCertify = 1 << iota
+	KeyFlagSign
+	KeyFlagEncryptCommunications
+	KeyFlagEncryptStorage
+)
+
+// Signature represents a signature. See RFC 4880, section 5.2.
+type Signature struct {
+	Version    int
+	SigType    SignatureType
+	PubKeyAlgo PublicKeyAlgorithm
+	Hash       crypto.Hash
+
+	// HashSuffix is extra data that is hashed in after the signed data.
+	HashSuffix []byte
+	// HashTag contains the first two bytes of the hash for fast rejection
+	// of bad signed data.
+	HashTag [2]byte
+
+	// Metadata includes format, filename and time, and is protected by v5
+	// signatures of type 0x00 or 0x01. This metadata is included into the hash
+	// computation; if nil, six 0x00 bytes are used instead. See section 5.2.4.
+	Metadata *LiteralData
+
+	CreationTime time.Time
+
+	RSASignature         encoding.Field
+	DSASigR, DSASigS     encoding.Field
+	ECDSASigR, ECDSASigS encoding.Field
+	EdDSASigR, EdDSASigS encoding.Field
+
+	// rawSubpackets contains the unparsed subpackets, in order.
+	rawSubpackets []outputSubpacket
+
+	// The following are optional so are nil when not included in the
+	// signature.
+
+	SigLifetimeSecs, KeyLifetimeSecs                        *uint32
+	PreferredSymmetric, PreferredHash, PreferredCompression []uint8
+	PreferredAEAD                                           []uint8
+	IssuerKeyId                                             *uint64
+	IssuerFingerprint                                       []byte
+	IsPrimaryId                                             *bool
+
+	// PolicyURI can be set to the URI of a document that describes the
+	// policy under which the signature was issued. See RFC 4880, section
+	// 5.2.3.20 for details.
+	PolicyURI string
+
+	// FlagsValid is set if any flags were given. See RFC 4880, section
+	// 5.2.3.21 for details.
+	FlagsValid                                                           bool
+	FlagCertify, FlagSign, FlagEncryptCommunications, FlagEncryptStorage bool
+
+	// RevocationReason is set if this signature has been revoked.
+	// See RFC 4880, section 5.2.3.23 for details.
+	RevocationReason     *uint8
+	RevocationReasonText string
+
+	// In a self-signature, these flags are set there is a features subpacket
+	// indicating that the issuer implementation supports these features
+	// (section 5.2.5.25).
+	MDC, AEAD, V5Keys bool
+
+	// EmbeddedSignature, if non-nil, is a signature of the parent key, by
+	// this key. This prevents an attacker from claiming another's signing
+	// subkey as their own.
+	EmbeddedSignature *Signature
+
+	outSubpackets []outputSubpacket
+}
+
+func (sig *Signature) parse(r io.Reader) (err error) {
+	// RFC 4880, section 5.2.3
+	var buf [5]byte
+	_, err = readFull(r, buf[:1])
+	if err != nil {
+		return
+	}
+	if buf[0] != 4 && buf[0] != 5 {
+		err = errors.UnsupportedError("signature packet version " + strconv.Itoa(int(buf[0])))
+		return
+	}
+	sig.Version = int(buf[0])
+	_, err = readFull(r, buf[:5])
+	if err != nil {
+		return
+	}
+	sig.SigType = SignatureType(buf[0])
+	sig.PubKeyAlgo = PublicKeyAlgorithm(buf[1])
+	switch sig.PubKeyAlgo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly, PubKeyAlgoDSA, PubKeyAlgoECDSA, PubKeyAlgoEdDSA:
+	default:
+		err = errors.UnsupportedError("public key algorithm " + strconv.Itoa(int(sig.PubKeyAlgo)))
+		return
+	}
+
+	var ok bool
+	sig.Hash, ok = s2k.HashIdToHash(buf[2])
+	if !ok {
+		return errors.UnsupportedError("hash function " + strconv.Itoa(int(buf[2])))
+	}
+
+	hashedSubpacketsLength := int(buf[3])<<8 | int(buf[4])
+	hashedSubpackets := make([]byte, hashedSubpacketsLength)
+	_, err = readFull(r, hashedSubpackets)
+	if err != nil {
+		return
+	}
+	sig.buildHashSuffix(hashedSubpackets)
+	err = parseSignatureSubpackets(sig, hashedSubpackets, true)
+	if err != nil {
+		return
+	}
+
+	_, err = readFull(r, buf[:2])
+	if err != nil {
+		return
+	}
+	unhashedSubpacketsLength := int(buf[0])<<8 | int(buf[1])
+	unhashedSubpackets := make([]byte, unhashedSubpacketsLength)
+	_, err = readFull(r, unhashedSubpackets)
+	if err != nil {
+		return
+	}
+	err = parseSignatureSubpackets(sig, unhashedSubpackets, false)
+	if err != nil {
+		return
+	}
+
+	_, err = readFull(r, sig.HashTag[:2])
+	if err != nil {
+		return
+	}
+
+	switch sig.PubKeyAlgo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly:
+		sig.RSASignature = new(encoding.MPI)
+		_, err = sig.RSASignature.ReadFrom(r)
+	case PubKeyAlgoDSA:
+		sig.DSASigR = new(encoding.MPI)
+		if _, err = sig.DSASigR.ReadFrom(r); err != nil {
+			return
+		}
+
+		sig.DSASigS = new(encoding.MPI)
+		_, err = sig.DSASigS.ReadFrom(r)
+	case PubKeyAlgoECDSA:
+		sig.ECDSASigR = new(encoding.MPI)
+		if _, err = sig.ECDSASigR.ReadFrom(r); err != nil {
+			return
+		}
+
+		sig.ECDSASigS = new(encoding.MPI)
+		_, err = sig.ECDSASigS.ReadFrom(r)
+	case PubKeyAlgoEdDSA:
+		sig.EdDSASigR = new(encoding.MPI)
+		if _, err = sig.EdDSASigR.ReadFrom(r); err != nil {
+			return
+		}
+
+		sig.EdDSASigS = new(encoding.MPI)
+		if _, err = sig.EdDSASigS.ReadFrom(r); err != nil {
+			return
+		}
+	default:
+		panic("unreachable")
+	}
+	return
+}
+
+// parseSignatureSubpackets parses subpackets of the main signature packet. See
+// RFC 4880, section 5.2.3.1.
+func parseSignatureSubpackets(sig *Signature, subpackets []byte, isHashed bool) (err error) {
+	for len(subpackets) > 0 {
+		subpackets, err = parseSignatureSubpacket(sig, subpackets, isHashed)
+		if err != nil {
+			return
+		}
+	}
+
+	if sig.CreationTime.IsZero() {
+		err = errors.StructuralError("no creation time in signature")
+	}
+
+	return
+}
+
+type signatureSubpacketType uint8
+
+const (
+	creationTimeSubpacket        signatureSubpacketType = 2
+	signatureExpirationSubpacket signatureSubpacketType = 3
+	keyExpirationSubpacket       signatureSubpacketType = 9
+	prefSymmetricAlgosSubpacket  signatureSubpacketType = 11
+	issuerSubpacket              signatureSubpacketType = 16
+	prefHashAlgosSubpacket       signatureSubpacketType = 21
+	prefCompressionSubpacket     signatureSubpacketType = 22
+	primaryUserIdSubpacket       signatureSubpacketType = 25
+	policyUriSubpacket           signatureSubpacketType = 26
+	keyFlagsSubpacket            signatureSubpacketType = 27
+	reasonForRevocationSubpacket signatureSubpacketType = 29
+	featuresSubpacket            signatureSubpacketType = 30
+	embeddedSignatureSubpacket   signatureSubpacketType = 32
+	issuerFingerprintSubpacket   signatureSubpacketType = 33
+	prefAeadAlgosSubpacket       signatureSubpacketType = 34
+)
+
+// parseSignatureSubpacket parses a single subpacket. len(subpacket) is >= 1.
+func parseSignatureSubpacket(sig *Signature, subpacket []byte, isHashed bool) (rest []byte, err error) {
+	// RFC 4880, section 5.2.3.1
+	var (
+		length     uint32
+		packetType signatureSubpacketType
+		isCritical bool
+	)
+	switch {
+	case subpacket[0] < 192:
+		length = uint32(subpacket[0])
+		subpacket = subpacket[1:]
+	case subpacket[0] < 255:
+		if len(subpacket) < 2 {
+			goto Truncated
+		}
+		length = uint32(subpacket[0]-192)<<8 + uint32(subpacket[1]) + 192
+		subpacket = subpacket[2:]
+	default:
+		if len(subpacket) < 5 {
+			goto Truncated
+		}
+		length = uint32(subpacket[1])<<24 |
+			uint32(subpacket[2])<<16 |
+			uint32(subpacket[3])<<8 |
+			uint32(subpacket[4])
+		subpacket = subpacket[5:]
+	}
+	if length > uint32(len(subpacket)) {
+		goto Truncated
+	}
+	rest = subpacket[length:]
+	subpacket = subpacket[:length]
+	if len(subpacket) == 0 {
+		err = errors.StructuralError("zero length signature subpacket")
+		return
+	}
+	packetType = signatureSubpacketType(subpacket[0] & 0x7f)
+	isCritical = subpacket[0]&0x80 == 0x80
+	subpacket = subpacket[1:]
+	sig.rawSubpackets = append(sig.rawSubpackets, outputSubpacket{isHashed, packetType, isCritical, subpacket})
+	switch packetType {
+	case creationTimeSubpacket:
+		if !isHashed {
+			err = errors.StructuralError("signature creation time in non-hashed area")
+			return
+		}
+		if len(subpacket) != 4 {
+			err = errors.StructuralError("signature creation time not four bytes")
+			return
+		}
+		t := binary.BigEndian.Uint32(subpacket)
+		sig.CreationTime = time.Unix(int64(t), 0)
+	case signatureExpirationSubpacket:
+		// Signature expiration time, section 5.2.3.10
+		if !isHashed {
+			return
+		}
+		if len(subpacket) != 4 {
+			err = errors.StructuralError("expiration subpacket with bad length")
+			return
+		}
+		sig.SigLifetimeSecs = new(uint32)
+		*sig.SigLifetimeSecs = binary.BigEndian.Uint32(subpacket)
+	case keyExpirationSubpacket:
+		// Key expiration time, section 5.2.3.6
+		if !isHashed {
+			return
+		}
+		if len(subpacket) != 4 {
+			err = errors.StructuralError("key expiration subpacket with bad length")
+			return
+		}
+		sig.KeyLifetimeSecs = new(uint32)
+		*sig.KeyLifetimeSecs = binary.BigEndian.Uint32(subpacket)
+	case prefSymmetricAlgosSubpacket:
+		// Preferred symmetric algorithms, section 5.2.3.7
+		if !isHashed {
+			return
+		}
+		sig.PreferredSymmetric = make([]byte, len(subpacket))
+		copy(sig.PreferredSymmetric, subpacket)
+	case issuerSubpacket:
+		if sig.Version > 4 {
+			err = errors.StructuralError("issuer subpacket found in v5 key")
+		}
+		// Issuer, section 5.2.3.5
+		if len(subpacket) != 8 {
+			err = errors.StructuralError("issuer subpacket with bad length")
+			return
+		}
+		sig.IssuerKeyId = new(uint64)
+		*sig.IssuerKeyId = binary.BigEndian.Uint64(subpacket)
+	case prefHashAlgosSubpacket:
+		// Preferred hash algorithms, section 5.2.3.8
+		if !isHashed {
+			return
+		}
+		sig.PreferredHash = make([]byte, len(subpacket))
+		copy(sig.PreferredHash, subpacket)
+	case prefCompressionSubpacket:
+		// Preferred compression algorithms, section 5.2.3.9
+		if !isHashed {
+			return
+		}
+		sig.PreferredCompression = make([]byte, len(subpacket))
+		copy(sig.PreferredCompression, subpacket)
+	case primaryUserIdSubpacket:
+		// Primary User ID, section 5.2.3.19
+		if !isHashed {
+			return
+		}
+		if len(subpacket) != 1 {
+			err = errors.StructuralError("primary user id subpacket with bad length")
+			return
+		}
+		sig.IsPrimaryId = new(bool)
+		if subpacket[0] > 0 {
+			*sig.IsPrimaryId = true
+		}
+	case keyFlagsSubpacket:
+		// Key flags, section 5.2.3.21
+		if !isHashed {
+			return
+		}
+		if len(subpacket) == 0 {
+			err = errors.StructuralError("empty key flags subpacket")
+			return
+		}
+		sig.FlagsValid = true
+		if subpacket[0]&KeyFlagCertify != 0 {
+			sig.FlagCertify = true
+		}
+		if subpacket[0]&KeyFlagSign != 0 {
+			sig.FlagSign = true
+		}
+		if subpacket[0]&KeyFlagEncryptCommunications != 0 {
+			sig.FlagEncryptCommunications = true
+		}
+		if subpacket[0]&KeyFlagEncryptStorage != 0 {
+			sig.FlagEncryptStorage = true
+		}
+	case reasonForRevocationSubpacket:
+		// Reason For Revocation, section 5.2.3.23
+		if !isHashed {
+			return
+		}
+		if len(subpacket) == 0 {
+			err = errors.StructuralError("empty revocation reason subpacket")
+			return
+		}
+		sig.RevocationReason = new(uint8)
+		*sig.RevocationReason = subpacket[0]
+		sig.RevocationReasonText = string(subpacket[1:])
+	case featuresSubpacket:
+		// Features subpacket, section 5.2.3.24 specifies a very general
+		// mechanism for OpenPGP implementations to signal support for new
+		// features.
+		if !isHashed {
+			return
+		}
+		if len(subpacket) > 0 {
+			if subpacket[0]&0x01 != 0 {
+				sig.MDC = true
+			}
+			if subpacket[0]&0x02 != 0 {
+				sig.AEAD = true
+			}
+			if subpacket[0]&0x04 != 0 {
+				sig.V5Keys = true
+			}
+		}
+	case embeddedSignatureSubpacket:
+		// Only usage is in signatures that cross-certify
+		// signing subkeys. section 5.2.3.26 describes the
+		// format, with its usage described in section 11.1
+		if sig.EmbeddedSignature != nil {
+			err = errors.StructuralError("Cannot have multiple embedded signatures")
+			return
+		}
+		sig.EmbeddedSignature = new(Signature)
+		// Embedded signatures are required to be v4 signatures see
+		// section 12.1. However, we only parse v4 signatures in this
+		// file anyway.
+		if err := sig.EmbeddedSignature.parse(bytes.NewBuffer(subpacket)); err != nil {
+			return nil, err
+		}
+		if sigType := sig.EmbeddedSignature.SigType; sigType != SigTypePrimaryKeyBinding {
+			return nil, errors.StructuralError("cross-signature has unexpected type " + strconv.Itoa(int(sigType)))
+		}
+	case policyUriSubpacket:
+		// Policy URI, section 5.2.3.20
+		if !isHashed {
+			return
+		}
+		sig.PolicyURI = string(subpacket)
+	case issuerFingerprintSubpacket:
+		v, l := subpacket[0], len(subpacket[1:])
+		if v == 5 && l != 32 || v != 5 && l != 20 {
+			return nil, errors.StructuralError("bad fingerprint length")
+		}
+		sig.IssuerFingerprint = make([]byte, l)
+		copy(sig.IssuerFingerprint, subpacket[1:])
+		sig.IssuerKeyId = new(uint64)
+		if v == 5 {
+			*sig.IssuerKeyId = binary.BigEndian.Uint64(subpacket[1:9])
+		} else {
+			*sig.IssuerKeyId = binary.BigEndian.Uint64(subpacket[13:21])
+		}
+	case prefAeadAlgosSubpacket:
+		// Preferred symmetric algorithms, section 5.2.3.8
+		if !isHashed {
+			return
+		}
+		sig.PreferredAEAD = make([]byte, len(subpacket))
+		copy(sig.PreferredAEAD, subpacket)
+	default:
+		if isCritical {
+			err = errors.UnsupportedError("unknown critical signature subpacket type " + strconv.Itoa(int(packetType)))
+			return
+		}
+	}
+	return
+
+Truncated:
+	err = errors.StructuralError("signature subpacket truncated")
+	return
+}
+
+// subpacketLengthLength returns the length, in bytes, of an encoded length value.
+func subpacketLengthLength(length int) int {
+	if length < 192 {
+		return 1
+	}
+	if length < 16320 {
+		return 2
+	}
+	return 5
+}
+
+func (sig *Signature) CheckKeyIdOrFingerprint(pk *PublicKey) bool {
+	if sig.IssuerFingerprint != nil && len(sig.IssuerFingerprint) >= 20 {
+		return bytes.Equal(sig.IssuerFingerprint, pk.Fingerprint)
+	}
+	return sig.IssuerKeyId != nil && *sig.IssuerKeyId == pk.KeyId
+}
+
+// serializeSubpacketLength marshals the given length into to.
+func serializeSubpacketLength(to []byte, length int) int {
+	// RFC 4880, Section 4.2.2.
+	if length < 192 {
+		to[0] = byte(length)
+		return 1
+	}
+	if length < 16320 {
+		length -= 192
+		to[0] = byte((length >> 8) + 192)
+		to[1] = byte(length)
+		return 2
+	}
+	to[0] = 255
+	to[1] = byte(length >> 24)
+	to[2] = byte(length >> 16)
+	to[3] = byte(length >> 8)
+	to[4] = byte(length)
+	return 5
+}
+
+// subpacketsLength returns the serialized length, in bytes, of the given
+// subpackets.
+func subpacketsLength(subpackets []outputSubpacket, hashed bool) (length int) {
+	for _, subpacket := range subpackets {
+		if subpacket.hashed == hashed {
+			length += subpacketLengthLength(len(subpacket.contents) + 1)
+			length += 1 // type byte
+			length += len(subpacket.contents)
+		}
+	}
+	return
+}
+
+// serializeSubpackets marshals the given subpackets into to.
+func serializeSubpackets(to []byte, subpackets []outputSubpacket, hashed bool) {
+	for _, subpacket := range subpackets {
+		if subpacket.hashed == hashed {
+			n := serializeSubpacketLength(to, len(subpacket.contents)+1)
+			to[n] = byte(subpacket.subpacketType)
+			if subpacket.isCritical {
+				to[n] |= 0x80
+			}
+			to = to[1+n:]
+			n = copy(to, subpacket.contents)
+			to = to[n:]
+		}
+	}
+	return
+}
+
+// SigExpired returns whether sig is a signature that has expired or is created
+// in the future.
+func (sig *Signature) SigExpired(currentTime time.Time) bool {
+	if sig.CreationTime.After(currentTime) {
+		return true
+	}
+	if sig.SigLifetimeSecs == nil || *sig.SigLifetimeSecs == 0 {
+		return false
+	}
+	expiry := sig.CreationTime.Add(time.Duration(*sig.SigLifetimeSecs) * time.Second)
+	return currentTime.After(expiry)
+}
+
+// buildHashSuffix constructs the HashSuffix member of sig in preparation for signing.
+func (sig *Signature) buildHashSuffix(hashedSubpackets []byte) (err error) {
+	hash, ok := s2k.HashToHashId(sig.Hash)
+	if !ok {
+		sig.HashSuffix = nil
+		return errors.InvalidArgumentError("hash cannot be represented in OpenPGP: " + strconv.Itoa(int(sig.Hash)))
+	}
+
+	hashedFields := bytes.NewBuffer([]byte{
+		uint8(sig.Version),
+		uint8(sig.SigType),
+		uint8(sig.PubKeyAlgo),
+		uint8(hash),
+		uint8(len(hashedSubpackets) >> 8),
+		uint8(len(hashedSubpackets)),
+	})
+	hashedFields.Write(hashedSubpackets)
+
+	var l uint64 = uint64(6 + len(hashedSubpackets))
+	if sig.Version == 5 {
+		hashedFields.Write([]byte{0x05, 0xff})
+		hashedFields.Write([]byte{
+			uint8(l >> 56), uint8(l >> 48), uint8(l >> 40), uint8(l >> 32),
+			uint8(l >> 24), uint8(l >> 16), uint8(l >> 8), uint8(l),
+		})
+	} else {
+		hashedFields.Write([]byte{0x04, 0xff})
+		hashedFields.Write([]byte{
+			uint8(l >> 24), uint8(l >> 16), uint8(l >> 8), uint8(l),
+		})
+	}
+	sig.HashSuffix = make([]byte, hashedFields.Len())
+	copy(sig.HashSuffix, hashedFields.Bytes())
+	return
+}
+
+func (sig *Signature) signPrepareHash(h hash.Hash) (digest []byte, err error) {
+	hashedSubpacketsLen := subpacketsLength(sig.outSubpackets, true)
+	hashedSubpackets := make([]byte, hashedSubpacketsLen)
+	serializeSubpackets(hashedSubpackets, sig.outSubpackets, true)
+	err = sig.buildHashSuffix(hashedSubpackets)
+	if err != nil {
+		return
+	}
+	if sig.Version == 5 && (sig.SigType == 0x00 || sig.SigType == 0x01) {
+		sig.AddMetadataToHashSuffix()
+	}
+
+	h.Write(sig.HashSuffix)
+	digest = h.Sum(nil)
+	copy(sig.HashTag[:], digest)
+	return
+}
+
+// Sign signs a message with a private key. The hash, h, must contain
+// the hash of the message to be signed and will be mutated by this function.
+// On success, the signature is stored in sig. Call Serialize to write it out.
+// If config is nil, sensible defaults will be used.
+func (sig *Signature) Sign(h hash.Hash, priv *PrivateKey, config *Config) (err error) {
+	if priv.Dummy() {
+		return errors.ErrDummyPrivateKey("dummy key found")
+	}
+	sig.Version = priv.PublicKey.Version
+	sig.IssuerFingerprint = priv.PublicKey.Fingerprint
+	sig.outSubpackets, err = sig.buildSubpackets(priv.PublicKey)
+	if err != nil {
+		return err
+	}
+	digest, err := sig.signPrepareHash(h)
+	if err != nil {
+		return
+	}
+	switch priv.PubKeyAlgo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly:
+		// supports both *rsa.PrivateKey and crypto.Signer
+		sigdata, err := priv.PrivateKey.(crypto.Signer).Sign(config.Random(), digest, sig.Hash)
+		if err == nil {
+			sig.RSASignature = encoding.NewMPI(sigdata)
+		}
+	case PubKeyAlgoDSA:
+		dsaPriv := priv.PrivateKey.(*dsa.PrivateKey)
+
+		// Need to truncate hashBytes to match FIPS 186-3 section 4.6.
+		subgroupSize := (dsaPriv.Q.BitLen() + 7) / 8
+		if len(digest) > subgroupSize {
+			digest = digest[:subgroupSize]
+		}
+		r, s, err := dsa.Sign(config.Random(), dsaPriv, digest)
+		if err == nil {
+			sig.DSASigR = new(encoding.MPI).SetBig(r)
+			sig.DSASigS = new(encoding.MPI).SetBig(s)
+		}
+	case PubKeyAlgoECDSA:
+		var r, s *big.Int
+		if pk, ok := priv.PrivateKey.(*ecdsa.PrivateKey); ok {
+			// direct support, avoid asn1 wrapping/unwrapping
+			r, s, err = ecdsa.Sign(config.Random(), pk, digest)
+		} else {
+			var b []byte
+			b, err = priv.PrivateKey.(crypto.Signer).Sign(config.Random(), digest, sig.Hash)
+			if err == nil {
+				r, s, err = unwrapECDSASig(b)
+			}
+		}
+		if err == nil {
+			sig.ECDSASigR = new(encoding.MPI).SetBig(r)
+			sig.ECDSASigS = new(encoding.MPI).SetBig(s)
+		}
+	case PubKeyAlgoEdDSA:
+		sigdata, err := priv.PrivateKey.(crypto.Signer).Sign(config.Random(), digest, crypto.Hash(0))
+		if err == nil {
+			sig.EdDSASigR = encoding.NewMPI(sigdata[:32])
+			sig.EdDSASigS = encoding.NewMPI(sigdata[32:])
+		}
+	default:
+		err = errors.UnsupportedError("public key algorithm: " + strconv.Itoa(int(sig.PubKeyAlgo)))
+	}
+
+	return
+}
+
+// unwrapECDSASig parses the two integer components of an ASN.1-encoded ECDSA
+// signature.
+func unwrapECDSASig(b []byte) (r, s *big.Int, err error) {
+	var ecsdaSig struct {
+		R, S *big.Int
+	}
+	_, err = asn1.Unmarshal(b, &ecsdaSig)
+	if err != nil {
+		return
+	}
+	return ecsdaSig.R, ecsdaSig.S, nil
+}
+
+// SignUserId computes a signature from priv, asserting that pub is a valid
+// key for the identity id.  On success, the signature is stored in sig. Call
+// Serialize to write it out.
+// If config is nil, sensible defaults will be used.
+func (sig *Signature) SignUserId(id string, pub *PublicKey, priv *PrivateKey, config *Config) error {
+	if priv.Dummy() {
+		return errors.ErrDummyPrivateKey("dummy key found")
+	}
+	h, err := userIdSignatureHash(id, pub, sig.Hash)
+	if err != nil {
+		return err
+	}
+	return sig.Sign(h, priv, config)
+}
+
+// CrossSignKey computes a signature from signingKey on pub hashed using hashKey. On success,
+// the signature is stored in sig. Call Serialize to write it out.
+// If config is nil, sensible defaults will be used.
+func (sig *Signature) CrossSignKey(pub *PublicKey, hashKey *PublicKey, signingKey *PrivateKey,
+	config *Config) error {
+	h, err := keySignatureHash(hashKey, pub, sig.Hash)
+	if err != nil {
+		return err
+	}
+	return sig.Sign(h, signingKey, config)
+}
+
+// SignKey computes a signature from priv, asserting that pub is a subkey. On
+// success, the signature is stored in sig. Call Serialize to write it out.
+// If config is nil, sensible defaults will be used.
+func (sig *Signature) SignKey(pub *PublicKey, priv *PrivateKey, config *Config) error {
+	if priv.Dummy() {
+		return errors.ErrDummyPrivateKey("dummy key found")
+	}
+	h, err := keySignatureHash(&priv.PublicKey, pub, sig.Hash)
+	if err != nil {
+		return err
+	}
+	return sig.Sign(h, priv, config)
+}
+
+// RevokeKey computes a revocation signature of pub using priv. On success, the signature is
+// stored in sig. Call Serialize to write it out.
+// If config is nil, sensible defaults will be used.
+func (sig *Signature) RevokeKey(pub *PublicKey, priv *PrivateKey, config *Config) error {
+	h, err := keyRevocationHash(pub, sig.Hash)
+	if err != nil {
+		return err
+	}
+	return sig.Sign(h, priv, config)
+}
+
+// Serialize marshals sig to w. Sign, SignUserId or SignKey must have been
+// called first.
+func (sig *Signature) Serialize(w io.Writer) (err error) {
+	if len(sig.outSubpackets) == 0 {
+		sig.outSubpackets = sig.rawSubpackets
+	}
+	if sig.RSASignature == nil && sig.DSASigR == nil && sig.ECDSASigR == nil && sig.EdDSASigR == nil {
+		return errors.InvalidArgumentError("Signature: need to call Sign, SignUserId or SignKey before Serialize")
+	}
+
+	sigLength := 0
+	switch sig.PubKeyAlgo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly:
+		sigLength = int(sig.RSASignature.EncodedLength())
+	case PubKeyAlgoDSA:
+		sigLength = int(sig.DSASigR.EncodedLength())
+		sigLength += int(sig.DSASigS.EncodedLength())
+	case PubKeyAlgoECDSA:
+		sigLength = int(sig.ECDSASigR.EncodedLength())
+		sigLength += int(sig.ECDSASigS.EncodedLength())
+	case PubKeyAlgoEdDSA:
+		sigLength = int(sig.EdDSASigR.EncodedLength())
+		sigLength += int(sig.EdDSASigS.EncodedLength())
+	default:
+		panic("impossible")
+	}
+
+	unhashedSubpacketsLen := subpacketsLength(sig.outSubpackets, false)
+	length := len(sig.HashSuffix) - 6 /* trailer not included */ +
+		2 /* length of unhashed subpackets */ + unhashedSubpacketsLen +
+		2 /* hash tag */ + sigLength
+	if sig.Version == 5 {
+		length -= 4 // eight-octet instead of four-octet big endian
+	}
+	err = serializeHeader(w, packetTypeSignature, length)
+	if err != nil {
+		return
+	}
+	err = sig.serializeBody(w)
+	if err != nil {
+		return err
+	}
+	return
+}
+
+func (sig *Signature) serializeBody(w io.Writer) (err error) {
+	hashedSubpacketsLen := uint16(uint16(sig.HashSuffix[4])<<8) | uint16(sig.HashSuffix[5])
+	fields := sig.HashSuffix[:6+hashedSubpacketsLen]
+	_, err = w.Write(fields)
+	if err != nil {
+		return
+	}
+
+	unhashedSubpacketsLen := subpacketsLength(sig.outSubpackets, false)
+	unhashedSubpackets := make([]byte, 2+unhashedSubpacketsLen)
+	unhashedSubpackets[0] = byte(unhashedSubpacketsLen >> 8)
+	unhashedSubpackets[1] = byte(unhashedSubpacketsLen)
+	serializeSubpackets(unhashedSubpackets[2:], sig.outSubpackets, false)
+
+	_, err = w.Write(unhashedSubpackets)
+	if err != nil {
+		return
+	}
+	_, err = w.Write(sig.HashTag[:])
+	if err != nil {
+		return
+	}
+
+	switch sig.PubKeyAlgo {
+	case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly:
+		_, err = w.Write(sig.RSASignature.EncodedBytes())
+	case PubKeyAlgoDSA:
+		if _, err = w.Write(sig.DSASigR.EncodedBytes()); err != nil {
+			return
+		}
+		_, err = w.Write(sig.DSASigS.EncodedBytes())
+	case PubKeyAlgoECDSA:
+		if _, err = w.Write(sig.ECDSASigR.EncodedBytes()); err != nil {
+			return
+		}
+		_, err = w.Write(sig.ECDSASigS.EncodedBytes())
+	case PubKeyAlgoEdDSA:
+		if _, err = w.Write(sig.EdDSASigR.EncodedBytes()); err != nil {
+			return
+		}
+		_, err = w.Write(sig.EdDSASigS.EncodedBytes())
+	default:
+		panic("impossible")
+	}
+	return
+}
+
+// outputSubpacket represents a subpacket to be marshaled.
+type outputSubpacket struct {
+	hashed        bool // true if this subpacket is in the hashed area.
+	subpacketType signatureSubpacketType
+	isCritical    bool
+	contents      []byte
+}
+
+func (sig *Signature) buildSubpackets(issuer PublicKey) (subpackets []outputSubpacket, err error) {
+	creationTime := make([]byte, 4)
+	binary.BigEndian.PutUint32(creationTime, uint32(sig.CreationTime.Unix()))
+	subpackets = append(subpackets, outputSubpacket{true, creationTimeSubpacket, false, creationTime})
+
+	if sig.IssuerKeyId != nil && sig.Version == 4 {
+		keyId := make([]byte, 8)
+		binary.BigEndian.PutUint64(keyId, *sig.IssuerKeyId)
+		subpackets = append(subpackets, outputSubpacket{true, issuerSubpacket, true, keyId})
+	}
+	if sig.IssuerFingerprint != nil {
+		contents := append([]uint8{uint8(issuer.Version)}, sig.IssuerFingerprint...)
+		subpackets = append(subpackets, outputSubpacket{true, issuerFingerprintSubpacket, true, contents})
+	}
+	if sig.SigLifetimeSecs != nil && *sig.SigLifetimeSecs != 0 {
+		sigLifetime := make([]byte, 4)
+		binary.BigEndian.PutUint32(sigLifetime, *sig.SigLifetimeSecs)
+		subpackets = append(subpackets, outputSubpacket{true, signatureExpirationSubpacket, true, sigLifetime})
+	}
+
+	// Key flags may only appear in self-signatures or certification signatures.
+
+	if sig.FlagsValid {
+		var flags byte
+		if sig.FlagCertify {
+			flags |= KeyFlagCertify
+		}
+		if sig.FlagSign {
+			flags |= KeyFlagSign
+		}
+		if sig.FlagEncryptCommunications {
+			flags |= KeyFlagEncryptCommunications
+		}
+		if sig.FlagEncryptStorage {
+			flags |= KeyFlagEncryptStorage
+		}
+		subpackets = append(subpackets, outputSubpacket{true, keyFlagsSubpacket, false, []byte{flags}})
+	}
+
+	// The following subpackets may only appear in self-signatures.
+
+	var features = byte(0x00)
+	if sig.MDC {
+		features |= 0x01
+	}
+	if sig.AEAD {
+		features |= 0x02
+	}
+	if sig.V5Keys {
+		features |= 0x04
+	}
+
+	if features != 0x00 {
+		subpackets = append(subpackets, outputSubpacket{true, featuresSubpacket, false, []byte{features}})
+	}
+
+	if sig.KeyLifetimeSecs != nil && *sig.KeyLifetimeSecs != 0 {
+		keyLifetime := make([]byte, 4)
+		binary.BigEndian.PutUint32(keyLifetime, *sig.KeyLifetimeSecs)
+		subpackets = append(subpackets, outputSubpacket{true, keyExpirationSubpacket, true, keyLifetime})
+	}
+
+	if sig.IsPrimaryId != nil && *sig.IsPrimaryId {
+		subpackets = append(subpackets, outputSubpacket{true, primaryUserIdSubpacket, false, []byte{1}})
+	}
+
+	if len(sig.PreferredSymmetric) > 0 {
+		subpackets = append(subpackets, outputSubpacket{true, prefSymmetricAlgosSubpacket, false, sig.PreferredSymmetric})
+	}
+
+	if len(sig.PreferredHash) > 0 {
+		subpackets = append(subpackets, outputSubpacket{true, prefHashAlgosSubpacket, false, sig.PreferredHash})
+	}
+
+	if len(sig.PreferredCompression) > 0 {
+		subpackets = append(subpackets, outputSubpacket{true, prefCompressionSubpacket, false, sig.PreferredCompression})
+	}
+
+	if len(sig.PolicyURI) > 0 {
+		subpackets = append(subpackets, outputSubpacket{true, policyUriSubpacket, false, []uint8(sig.PolicyURI)})
+	}
+
+	if len(sig.PreferredAEAD) > 0 {
+		subpackets = append(subpackets, outputSubpacket{true, prefAeadAlgosSubpacket, false, sig.PreferredAEAD})
+	}
+
+	// Revocation reason appears only in revocation signatures and is serialized as per section 5.2.3.23.
+	if sig.RevocationReason != nil {
+		subpackets = append(subpackets, outputSubpacket{true, reasonForRevocationSubpacket, true,
+			append([]uint8{*sig.RevocationReason}, []uint8(sig.RevocationReasonText)...)})
+	}
+
+	// EmbeddedSignature appears only in subkeys capable of signing and is serialized as per section 5.2.3.26.
+	if sig.EmbeddedSignature != nil {
+		var buf bytes.Buffer
+		err = sig.EmbeddedSignature.serializeBody(&buf)
+		if err != nil {
+			return
+		}
+		subpackets = append(subpackets, outputSubpacket{true, embeddedSignatureSubpacket, true, buf.Bytes()})
+	}
+
+	return
+}
+
+// AddMetadataToHashSuffix modifies the current hash suffix to include metadata
+// (format, filename, and time). Version 5 keys protect this data including it
+// in the hash computation. See section 5.2.4.
+func (sig *Signature) AddMetadataToHashSuffix() {
+	if sig == nil || sig.Version != 5 {
+		return
+	}
+	if sig.SigType != 0x00 && sig.SigType != 0x01 {
+		return
+	}
+	lit := sig.Metadata
+	if lit == nil {
+		// This will translate into six 0x00 bytes.
+		lit = &LiteralData{}
+	}
+
+	// Extract the current byte count
+	n := sig.HashSuffix[len(sig.HashSuffix)-8:]
+	l := uint64(
+		uint64(n[0])<<56 | uint64(n[1])<<48 | uint64(n[2])<<40 | uint64(n[3])<<32 |
+		uint64(n[4])<<24 | uint64(n[5])<<16 | uint64(n[6])<<8  | uint64(n[7]))
+
+	suffix := bytes.NewBuffer(nil)
+	suffix.Write(sig.HashSuffix[:l])
+
+	// Add the metadata
+	var buf [4]byte
+	buf[0] = lit.Format
+	fileName := lit.FileName
+	if len(lit.FileName) > 255 {
+		fileName = fileName[:255]
+	}
+	buf[1] = byte(len(fileName))
+	suffix.Write(buf[:2])
+	suffix.Write([]byte(lit.FileName))
+	binary.BigEndian.PutUint32(buf[:], lit.Time)
+	suffix.Write(buf[:])
+
+	// Update the counter and restore trailing bytes
+	l = uint64(suffix.Len())
+	suffix.Write([]byte{0x05, 0xff})
+	suffix.Write([]byte{
+		uint8(l >> 56), uint8(l >> 48), uint8(l >> 40), uint8(l >> 32),
+		uint8(l >> 24), uint8(l >> 16), uint8(l >> 8), uint8(l),
+	})
+	sig.HashSuffix = suffix.Bytes()
+}

vendor/github.com/ProtonMail/go-crypto/openpgp/packet/symmetric_key_encrypted.go

@@ -0,0 +1,267 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"bytes"
+	"crypto/cipher"
+	"io"
+	"strconv"
+
+	"github.com/ProtonMail/go-crypto/openpgp/errors"
+	"github.com/ProtonMail/go-crypto/openpgp/s2k"
+)
+
+// This is the largest session key that we'll support. Since no 512-bit cipher
+// has even been seriously used, this is comfortably large.
+const maxSessionKeySizeInBytes = 64
+
+// SymmetricKeyEncrypted represents a passphrase protected session key. See RFC
+// 4880, section 5.3.
+type SymmetricKeyEncrypted struct {
+	Version      int
+	CipherFunc   CipherFunction
+	Mode         AEADMode
+	s2k          func(out, in []byte)
+	aeadNonce    []byte
+	encryptedKey []byte
+}
+
+func (ske *SymmetricKeyEncrypted) parse(r io.Reader) error {
+	// RFC 4880, section 5.3.
+	var buf [2]byte
+	if _, err := readFull(r, buf[:]); err != nil {
+		return err
+	}
+	ske.Version = int(buf[0])
+	if ske.Version != 4 && ske.Version != 5 {
+		return errors.UnsupportedError("unknown SymmetricKeyEncrypted version")
+	}
+	ske.CipherFunc = CipherFunction(buf[1])
+	if ske.CipherFunc.KeySize() == 0 {
+		return errors.UnsupportedError("unknown cipher: " + strconv.Itoa(int(buf[1])))
+	}
+
+	if ske.Version == 5 {
+		mode := make([]byte, 1)
+		if _, err := r.Read(mode); err != nil {
+			return errors.StructuralError("cannot read AEAD octect from packet")
+		}
+		ske.Mode = AEADMode(mode[0])
+	}
+
+	var err error
+	if ske.s2k, err = s2k.Parse(r); err != nil {
+		if _, ok := err.(errors.ErrDummyPrivateKey); ok {
+			return errors.UnsupportedError("missing key GNU extension in session key")
+		}
+		return err
+	}
+
+	if ske.Version == 5 {
+		// AEAD nonce
+		nonce := make([]byte, ske.Mode.NonceLength())
+		_, err := readFull(r, nonce)
+		if err != nil && err != io.ErrUnexpectedEOF {
+			return err
+		}
+		ske.aeadNonce = nonce
+	}
+
+	encryptedKey := make([]byte, maxSessionKeySizeInBytes)
+	// The session key may follow. We just have to try and read to find
+	// out. If it exists then we limit it to maxSessionKeySizeInBytes.
+	n, err := readFull(r, encryptedKey)
+	if err != nil && err != io.ErrUnexpectedEOF {
+		return err
+	}
+
+	if n != 0 {
+		if n == maxSessionKeySizeInBytes {
+			return errors.UnsupportedError("oversized encrypted session key")
+		}
+		ske.encryptedKey = encryptedKey[:n]
+	}
+	return nil
+}
+
+// Decrypt attempts to decrypt an encrypted session key and returns the key and
+// the cipher to use when decrypting a subsequent Symmetrically Encrypted Data
+// packet.
+func (ske *SymmetricKeyEncrypted) Decrypt(passphrase []byte) ([]byte, CipherFunction, error) {
+	key := make([]byte, ske.CipherFunc.KeySize())
+	ske.s2k(key, passphrase)
+	if len(ske.encryptedKey) == 0 {
+		return key, ske.CipherFunc, nil
+	}
+	switch ske.Version {
+	case 4:
+		plaintextKey, cipherFunc, err := ske.decryptV4(key)
+		return plaintextKey, cipherFunc, err
+	case 5:
+		plaintextKey, err := ske.decryptV5(key)
+		return plaintextKey, CipherFunction(0), err
+	}
+	err := errors.UnsupportedError("unknown SymmetricKeyEncrypted version")
+	return nil, CipherFunction(0), err
+}
+
+func (ske *SymmetricKeyEncrypted) decryptV4(key []byte) ([]byte, CipherFunction, error) {
+	// the IV is all zeros
+	iv := make([]byte, ske.CipherFunc.blockSize())
+	c := cipher.NewCFBDecrypter(ske.CipherFunc.new(key), iv)
+	plaintextKey := make([]byte, len(ske.encryptedKey))
+	c.XORKeyStream(plaintextKey, ske.encryptedKey)
+	cipherFunc := CipherFunction(plaintextKey[0])
+	if cipherFunc.blockSize() == 0 {
+		return nil, ske.CipherFunc, errors.UnsupportedError(
+			"unknown cipher: " + strconv.Itoa(int(cipherFunc)))
+	}
+	plaintextKey = plaintextKey[1:]
+	if len(plaintextKey) != cipherFunc.KeySize() {
+		return nil, cipherFunc, errors.StructuralError(
+			"length of decrypted key not equal to cipher keysize")
+	}
+	return plaintextKey, cipherFunc, nil
+}
+
+func (ske *SymmetricKeyEncrypted) decryptV5(key []byte) ([]byte, error) {
+	blockCipher := CipherFunction(ske.CipherFunc).new(key)
+	aead := ske.Mode.new(blockCipher)
+
+	adata := []byte{0xc3, byte(5), byte(ske.CipherFunc), byte(ske.Mode)}
+	plaintextKey, err := aead.Open(nil, ske.aeadNonce, ske.encryptedKey, adata)
+	if err != nil {
+		return nil, err
+	}
+	return plaintextKey, nil
+}
+
+// SerializeSymmetricKeyEncrypted serializes a symmetric key packet to w.
+// The packet contains a random session key, encrypted by a key derived from
+// the given passphrase. The session key is returned and must be passed to
+// SerializeSymmetricallyEncrypted or SerializeAEADEncrypted, depending on
+// whether config.AEADConfig != nil.
+// If config is nil, sensible defaults will be used.
+func SerializeSymmetricKeyEncrypted(w io.Writer, passphrase []byte, config *Config) (key []byte, err error) {
+	cipherFunc := config.Cipher()
+	keySize := cipherFunc.KeySize()
+	if keySize == 0 {
+		return nil, errors.UnsupportedError("unknown cipher: " + strconv.Itoa(int(cipherFunc)))
+	}
+
+	sessionKey := make([]byte, keySize)
+	_, err = io.ReadFull(config.Random(), sessionKey)
+	if err != nil {
+		return
+	}
+
+	err = SerializeSymmetricKeyEncryptedReuseKey(w, sessionKey, passphrase, config)
+	if err != nil {
+		return
+	}
+
+	key = sessionKey
+	return
+}
+
+// SerializeSymmetricKeyEncryptedReuseKey serializes a symmetric key packet to w.
+// The packet contains the given session key, encrypted by a key derived from
+// the given passphrase. The session key must be passed to
+// SerializeSymmetricallyEncrypted or SerializeAEADEncrypted, depending on
+// whether config.AEADConfig != nil.
+// If config is nil, sensible defaults will be used.
+func SerializeSymmetricKeyEncryptedReuseKey(w io.Writer, sessionKey []byte, passphrase []byte, config *Config) (err error) {
+	var version int
+	if config.AEAD() != nil {
+		version = 5
+	} else {
+		version = 4
+	}
+	cipherFunc := config.Cipher()
+	keySize := cipherFunc.KeySize()
+	if keySize == 0 {
+		return errors.UnsupportedError("unknown cipher: " + strconv.Itoa(int(cipherFunc)))
+	}
+
+	s2kBuf := new(bytes.Buffer)
+	keyEncryptingKey := make([]byte, keySize)
+	// s2k.Serialize salts and stretches the passphrase, and writes the
+	// resulting key to keyEncryptingKey and the s2k descriptor to s2kBuf.
+	err = s2k.Serialize(s2kBuf, keyEncryptingKey, config.Random(), passphrase, &s2k.Config{Hash: config.Hash(), S2KCount: config.PasswordHashIterations()})
+	if err != nil {
+		return
+	}
+	s2kBytes := s2kBuf.Bytes()
+
+	var packetLength int
+	switch version {
+	case 4:
+		packetLength = 2 /* header */ + len(s2kBytes) + 1 /* cipher type */ + keySize
+	case 5:
+		nonceLen := config.AEAD().Mode().NonceLength()
+		tagLen := config.AEAD().Mode().TagLength()
+		packetLength = 3 + len(s2kBytes) + nonceLen + keySize + tagLen
+	}
+	err = serializeHeader(w, packetTypeSymmetricKeyEncrypted, packetLength)
+	if err != nil {
+		return
+	}
+
+	buf := make([]byte, 2)
+	// Symmetric Key Encrypted Version
+	buf[0] = byte(version)
+	// Cipher function
+	buf[1] = byte(cipherFunc)
+
+	if version == 5 {
+		// AEAD mode
+		buf = append(buf, byte(config.AEAD().Mode()))
+	}
+	_, err = w.Write(buf)
+	if err != nil {
+		return
+	}
+	_, err = w.Write(s2kBytes)
+	if err != nil {
+		return
+	}
+
+	switch version {
+	case 4:
+		iv := make([]byte, cipherFunc.blockSize())
+		c := cipher.NewCFBEncrypter(cipherFunc.new(keyEncryptingKey), iv)
+		encryptedCipherAndKey := make([]byte, keySize+1)
+		c.XORKeyStream(encryptedCipherAndKey, buf[1:])
+		c.XORKeyStream(encryptedCipherAndKey[1:], sessionKey)
+		_, err = w.Write(encryptedCipherAndKey)
+		if err != nil {
+			return
+		}
+	case 5:
+		blockCipher := cipherFunc.new(keyEncryptingKey)
+		mode := config.AEAD().Mode()
+		aead := mode.new(blockCipher)
+		// Sample nonce using random reader
+		nonce := make([]byte, config.AEAD().Mode().NonceLength())
+		_, err = io.ReadFull(config.Random(), nonce)
+		if err != nil {
+			return
+		}
+		// Seal and write (encryptedData includes auth. tag)
+		adata := []byte{0xc3, byte(5), byte(cipherFunc), byte(mode)}
+		encryptedData := aead.Seal(nil, nonce, sessionKey, adata)
+		_, err = w.Write(nonce)
+		if err != nil {
+			return
+		}
+		_, err = w.Write(encryptedData)
+		if err != nil {
+			return
+		}
+	}
+
+	return
+}

vendor/github.com/ProtonMail/go-crypto/openpgp/packet/symmetrically_encrypted.go

@@ -0,0 +1,290 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"crypto/cipher"
+	"crypto/sha1"
+	"crypto/subtle"
+	"hash"
+	"io"
+	"strconv"
+
+	"github.com/ProtonMail/go-crypto/openpgp/errors"
+)
+
+// SymmetricallyEncrypted represents a symmetrically encrypted byte string. The
+// encrypted Contents will consist of more OpenPGP packets. See RFC 4880,
+// sections 5.7 and 5.13.
+type SymmetricallyEncrypted struct {
+	MDC      bool // true iff this is a type 18 packet and thus has an embedded MAC.
+	Contents io.Reader
+	prefix   []byte
+}
+
+const symmetricallyEncryptedVersion = 1
+
+func (se *SymmetricallyEncrypted) parse(r io.Reader) error {
+	if se.MDC {
+		// See RFC 4880, section 5.13.
+		var buf [1]byte
+		_, err := readFull(r, buf[:])
+		if err != nil {
+			return err
+		}
+		if buf[0] != symmetricallyEncryptedVersion {
+			return errors.UnsupportedError("unknown SymmetricallyEncrypted version")
+		}
+	}
+	se.Contents = r
+	return nil
+}
+
+// Decrypt returns a ReadCloser, from which the decrypted Contents of the
+// packet can be read. An incorrect key will only be detected after trying
+// to decrypt the entire data.
+func (se *SymmetricallyEncrypted) Decrypt(c CipherFunction, key []byte) (io.ReadCloser, error) {
+	keySize := c.KeySize()
+	if keySize == 0 {
+		return nil, errors.UnsupportedError("unknown cipher: " + strconv.Itoa(int(c)))
+	}
+	if len(key) != keySize {
+		return nil, errors.InvalidArgumentError("SymmetricallyEncrypted: incorrect key length")
+	}
+
+	if se.prefix == nil {
+		se.prefix = make([]byte, c.blockSize()+2)
+		_, err := readFull(se.Contents, se.prefix)
+		if err != nil {
+			return nil, err
+		}
+	} else if len(se.prefix) != c.blockSize()+2 {
+		return nil, errors.InvalidArgumentError("can't try ciphers with different block lengths")
+	}
+
+	ocfbResync := OCFBResync
+	if se.MDC {
+		// MDC packets use a different form of OCFB mode.
+		ocfbResync = OCFBNoResync
+	}
+
+	s := NewOCFBDecrypter(c.new(key), se.prefix, ocfbResync)
+
+	plaintext := cipher.StreamReader{S: s, R: se.Contents}
+
+	if se.MDC {
+		// MDC packets have an embedded hash that we need to check.
+		h := sha1.New()
+		h.Write(se.prefix)
+		return &seMDCReader{in: plaintext, h: h}, nil
+	}
+
+	// Otherwise, we just need to wrap plaintext so that it's a valid ReadCloser.
+	return seReader{plaintext}, nil
+}
+
+// seReader wraps an io.Reader with a no-op Close method.
+type seReader struct {
+	in io.Reader
+}
+
+func (ser seReader) Read(buf []byte) (int, error) {
+	return ser.in.Read(buf)
+}
+
+func (ser seReader) Close() error {
+	return nil
+}
+
+const mdcTrailerSize = 1 /* tag byte */ + 1 /* length byte */ + sha1.Size
+
+// An seMDCReader wraps an io.Reader, maintains a running hash and keeps hold
+// of the most recent 22 bytes (mdcTrailerSize). Upon EOF, those bytes form an
+// MDC packet containing a hash of the previous Contents which is checked
+// against the running hash. See RFC 4880, section 5.13.
+type seMDCReader struct {
+	in          io.Reader
+	h           hash.Hash
+	trailer     [mdcTrailerSize]byte
+	scratch     [mdcTrailerSize]byte
+	trailerUsed int
+	error       bool
+	eof         bool
+}
+
+func (ser *seMDCReader) Read(buf []byte) (n int, err error) {
+	if ser.error {
+		err = io.ErrUnexpectedEOF
+		return
+	}
+	if ser.eof {
+		err = io.EOF
+		return
+	}
+
+	// If we haven't yet filled the trailer buffer then we must do that
+	// first.
+	for ser.trailerUsed < mdcTrailerSize {
+		n, err = ser.in.Read(ser.trailer[ser.trailerUsed:])
+		ser.trailerUsed += n
+		if err == io.EOF {
+			if ser.trailerUsed != mdcTrailerSize {
+				n = 0
+				err = io.ErrUnexpectedEOF
+				ser.error = true
+				return
+			}
+			ser.eof = true
+			n = 0
+			return
+		}
+
+		if err != nil {
+			n = 0
+			return
+		}
+	}
+
+	// If it's a short read then we read into a temporary buffer and shift
+	// the data into the caller's buffer.
+	if len(buf) <= mdcTrailerSize {
+		n, err = readFull(ser.in, ser.scratch[:len(buf)])
+		copy(buf, ser.trailer[:n])
+		ser.h.Write(buf[:n])
+		copy(ser.trailer[:], ser.trailer[n:])
+		copy(ser.trailer[mdcTrailerSize-n:], ser.scratch[:])
+		if n < len(buf) {
+			ser.eof = true
+			err = io.EOF
+		}
+		return
+	}
+
+	n, err = ser.in.Read(buf[mdcTrailerSize:])
+	copy(buf, ser.trailer[:])
+	ser.h.Write(buf[:n])
+	copy(ser.trailer[:], buf[n:])
+
+	if err == io.EOF {
+		ser.eof = true
+	}
+	return
+}
+
+// This is a new-format packet tag byte for a type 19 (MDC) packet.
+const mdcPacketTagByte = byte(0x80) | 0x40 | 19
+
+func (ser *seMDCReader) Close() error {
+	if ser.error {
+		return errors.ErrMDCMissing
+	}
+
+	for !ser.eof {
+		// We haven't seen EOF so we need to read to the end
+		var buf [1024]byte
+		_, err := ser.Read(buf[:])
+		if err == io.EOF {
+			break
+		}
+		if err != nil {
+			return errors.ErrMDCMissing
+		}
+	}
+
+	ser.h.Write(ser.trailer[:2])
+
+	final := ser.h.Sum(nil)
+	if subtle.ConstantTimeCompare(final, ser.trailer[2:]) != 1 {
+		return errors.ErrMDCHashMismatch
+	}
+	// The hash already includes the MDC header, but we still check its value
+	// to confirm encryption correctness
+	if ser.trailer[0] != mdcPacketTagByte || ser.trailer[1] != sha1.Size {
+		return errors.ErrMDCMissing
+	}
+	return nil
+}
+
+// An seMDCWriter writes through to an io.WriteCloser while maintains a running
+// hash of the data written. On close, it emits an MDC packet containing the
+// running hash.
+type seMDCWriter struct {
+	w io.WriteCloser
+	h hash.Hash
+}
+
+func (w *seMDCWriter) Write(buf []byte) (n int, err error) {
+	w.h.Write(buf)
+	return w.w.Write(buf)
+}
+
+func (w *seMDCWriter) Close() (err error) {
+	var buf [mdcTrailerSize]byte
+
+	buf[0] = mdcPacketTagByte
+	buf[1] = sha1.Size
+	w.h.Write(buf[:2])
+	digest := w.h.Sum(nil)
+	copy(buf[2:], digest)
+
+	_, err = w.w.Write(buf[:])
+	if err != nil {
+		return
+	}
+	return w.w.Close()
+}
+
+// noOpCloser is like an ioutil.NopCloser, but for an io.Writer.
+type noOpCloser struct {
+	w io.Writer
+}
+
+func (c noOpCloser) Write(data []byte) (n int, err error) {
+	return c.w.Write(data)
+}
+
+func (c noOpCloser) Close() error {
+	return nil
+}
+
+// SerializeSymmetricallyEncrypted serializes a symmetrically encrypted packet
+// to w and returns a WriteCloser to which the to-be-encrypted packets can be
+// written.
+// If config is nil, sensible defaults will be used.
+func SerializeSymmetricallyEncrypted(w io.Writer, c CipherFunction, key []byte, config *Config) (Contents io.WriteCloser, err error) {
+	if c.KeySize() != len(key) {
+		return nil, errors.InvalidArgumentError("SymmetricallyEncrypted.Serialize: bad key length")
+	}
+	writeCloser := noOpCloser{w}
+	ciphertext, err := serializeStreamHeader(writeCloser, packetTypeSymmetricallyEncryptedMDC)
+	if err != nil {
+		return
+	}
+
+	_, err = ciphertext.Write([]byte{symmetricallyEncryptedVersion})
+	if err != nil {
+		return
+	}
+
+	block := c.new(key)
+	blockSize := block.BlockSize()
+	iv := make([]byte, blockSize)
+	_, err = config.Random().Read(iv)
+	if err != nil {
+		return
+	}
+	s, prefix := NewOCFBEncrypter(block, iv, OCFBNoResync)
+	_, err = ciphertext.Write(prefix)
+	if err != nil {
+		return
+	}
+	plaintext := cipher.StreamWriter{S: s, W: ciphertext}
+
+	h := sha1.New()
+	h.Write(iv)
+	h.Write(iv[blockSize-2:])
+	Contents = &seMDCWriter{w: plaintext, h: h}
+	return
+}

vendor/github.com/ProtonMail/go-crypto/openpgp/packet/userattribute.go

@@ -0,0 +1,94 @@
+// Copyright 2013 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"bytes"
+	"image"
+	"image/jpeg"
+	"io"
+	"io/ioutil"
+)
+
+const UserAttrImageSubpacket = 1
+
+// UserAttribute is capable of storing other types of data about a user
+// beyond name, email and a text comment. In practice, user attributes are typically used
+// to store a signed thumbnail photo JPEG image of the user.
+// See RFC 4880, section 5.12.
+type UserAttribute struct {
+	Contents []*OpaqueSubpacket
+}
+
+// NewUserAttributePhoto creates a user attribute packet
+// containing the given images.
+func NewUserAttributePhoto(photos ...image.Image) (uat *UserAttribute, err error) {
+	uat = new(UserAttribute)
+	for _, photo := range photos {
+		var buf bytes.Buffer
+		// RFC 4880, Section 5.12.1.
+		data := []byte{
+			0x10, 0x00, // Little-endian image header length (16 bytes)
+			0x01,       // Image header version 1
+			0x01,       // JPEG
+			0, 0, 0, 0, // 12 reserved octets, must be all zero.
+			0, 0, 0, 0,
+			0, 0, 0, 0}
+		if _, err = buf.Write(data); err != nil {
+			return
+		}
+		if err = jpeg.Encode(&buf, photo, nil); err != nil {
+			return
+		}
+		uat.Contents = append(uat.Contents, &OpaqueSubpacket{
+			SubType:  UserAttrImageSubpacket,
+			Contents: buf.Bytes()})
+	}
+	return
+}
+
+// NewUserAttribute creates a new user attribute packet containing the given subpackets.
+func NewUserAttribute(contents ...*OpaqueSubpacket) *UserAttribute {
+	return &UserAttribute{Contents: contents}
+}
+
+func (uat *UserAttribute) parse(r io.Reader) (err error) {
+	// RFC 4880, section 5.13
+	b, err := ioutil.ReadAll(r)
+	if err != nil {
+		return
+	}
+	uat.Contents, err = OpaqueSubpackets(b)
+	return
+}
+
+// Serialize marshals the user attribute to w in the form of an OpenPGP packet, including
+// header.
+func (uat *UserAttribute) Serialize(w io.Writer) (err error) {
+	var buf bytes.Buffer
+	for _, sp := range uat.Contents {
+		err = sp.Serialize(&buf)
+		if err != nil {
+			return err
+		}
+	}
+	if err = serializeHeader(w, packetTypeUserAttribute, buf.Len()); err != nil {
+		return err
+	}
+	_, err = w.Write(buf.Bytes())
+	return
+}
+
+// ImageData returns zero or more byte slices, each containing
+// JPEG File Interchange Format (JFIF), for each photo in the
+// user attribute packet.
+func (uat *UserAttribute) ImageData() (imageData [][]byte) {
+	for _, sp := range uat.Contents {
+		if sp.SubType == UserAttrImageSubpacket && len(sp.Contents) > 16 {
+			imageData = append(imageData, sp.Contents[16:])
+		}
+	}
+	return
+}

vendor/github.com/ProtonMail/go-crypto/openpgp/packet/userid.go

@@ -0,0 +1,160 @@
+// Copyright 2011 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package packet
+
+import (
+	"io"
+	"io/ioutil"
+	"strings"
+)
+
+// UserId contains text that is intended to represent the name and email
+// address of the key holder. See RFC 4880, section 5.11. By convention, this
+// takes the form "Full Name (Comment) <email@example.com>"
+type UserId struct {
+	Id string // By convention, this takes the form "Full Name (Comment) <email@example.com>" which is split out in the fields below.
+
+	Name, Comment, Email string
+}
+
+func hasInvalidCharacters(s string) bool {
+	for _, c := range s {
+		switch c {
+		case '(', ')', '<', '>', 0:
+			return true
+		}
+	}
+	return false
+}
+
+// NewUserId returns a UserId or nil if any of the arguments contain invalid
+// characters. The invalid characters are '\x00', '(', ')', '<' and '>'
+func NewUserId(name, comment, email string) *UserId {
+	// RFC 4880 doesn't deal with the structure of userid strings; the
+	// name, comment and email form is just a convention. However, there's
+	// no convention about escaping the metacharacters and GPG just refuses
+	// to create user ids where, say, the name contains a '('. We mirror
+	// this behaviour.
+
+	if hasInvalidCharacters(name) || hasInvalidCharacters(comment) || hasInvalidCharacters(email) {
+		return nil
+	}
+
+	uid := new(UserId)
+	uid.Name, uid.Comment, uid.Email = name, comment, email
+	uid.Id = name
+	if len(comment) > 0 {
+		if len(uid.Id) > 0 {
+			uid.Id += " "
+		}
+		uid.Id += "("
+		uid.Id += comment
+		uid.Id += ")"
+	}
+	if len(email) > 0 {
+		if len(uid.Id) > 0 {
+			uid.Id += " "
+		}
+		uid.Id += "<"
+		uid.Id += email
+		uid.Id += ">"
+	}
+	return uid
+}
+
+func (uid *UserId) parse(r io.Reader) (err error) {
+	// RFC 4880, section 5.11
+	b, err := ioutil.ReadAll(r)
+	if err != nil {
+		return
+	}
+	uid.Id = string(b)
+	uid.Name, uid.Comment, uid.Email = parseUserId(uid.Id)
+	return
+}
+
+// Serialize marshals uid to w in the form of an OpenPGP packet, including
+// header.
+func (uid *UserId) Serialize(w io.Writer) error {
+	err := serializeHeader(w, packetTypeUserId, len(uid.Id))
+	if err != nil {
+		return err
+	}
+	_, err = w.Write([]byte(uid.Id))
+	return err
+}
+
+// parseUserId extracts the name, comment and email from a user id string that
+// is formatted as "Full Name (Comment) <email@example.com>".
+func parseUserId(id string) (name, comment, email string) {
+	var n, c, e struct {
+		start, end int
+	}
+	var state int
+
+	for offset, rune := range id {
+		switch state {
+		case 0:
+			// Entering name
+			n.start = offset
+			state = 1
+			fallthrough
+		case 1:
+			// In name
+			if rune == '(' {
+				state = 2
+				n.end = offset
+			} else if rune == '<' {
+				state = 5
+				n.end = offset
+			}
+		case 2:
+			// Entering comment
+			c.start = offset
+			state = 3
+			fallthrough
+		case 3:
+			// In comment
+			if rune == ')' {
+				state = 4
+				c.end = offset
+			}
+		case 4:
+			// Between comment and email
+			if rune == '<' {
+				state = 5
+			}
+		case 5:
+			// Entering email
+			e.start = offset
+			state = 6
+			fallthrough
+		case 6:
+			// In email
+			if rune == '>' {
+				state = 7
+				e.end = offset
+			}
+		default:
+			// After email
+		}
+	}
+	switch state {
+	case 1:
+		// ended in the name
+		n.end = len(id)
+	case 3:
+		// ended in comment
+		c.end = len(id)
+	case 6:
+		// ended in email
+		e.end = len(id)
+	}
+
+	name = strings.TrimSpace(id[n.start:n.end])
+	comment = strings.TrimSpace(id[c.start:c.end])
+	email = strings.TrimSpace(id[e.start:e.end])
+	return
+}