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108 lines
2.6 KiB
Go
108 lines
2.6 KiB
Go
// Package ecc implements a generic interface for ECDH, ECDSA, and EdDSA.
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package ecc
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import (
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"crypto/subtle"
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"io"
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"github.com/ProtonMail/go-crypto/openpgp/errors"
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x448lib "github.com/cloudflare/circl/dh/x448"
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)
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type x448 struct{}
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func NewX448() *x448 {
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return &x448{}
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}
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func (c *x448) GetCurveName() string {
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return "x448"
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}
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// MarshalBytePoint encodes the public point from native format, adding the prefix.
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// See https://datatracker.ietf.org/doc/html/draft-ietf-openpgp-crypto-refresh-06#section-5.5.5.6
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func (c *x448) MarshalBytePoint(point []byte) []byte {
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return append([]byte{0x40}, point...)
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}
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// UnmarshalBytePoint decodes a point from prefixed format to native.
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// See https://datatracker.ietf.org/doc/html/draft-ietf-openpgp-crypto-refresh-06#section-5.5.5.6
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func (c *x448) UnmarshalBytePoint(point []byte) []byte {
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if len(point) != x448lib.Size+1 {
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return nil
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}
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return point[1:]
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}
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// MarshalByteSecret encoded a scalar from native format to prefixed.
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// See https://datatracker.ietf.org/doc/html/draft-ietf-openpgp-crypto-refresh-06#section-5.5.5.6.1.2
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func (c *x448) MarshalByteSecret(d []byte) []byte {
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return append([]byte{0x40}, d...)
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}
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// UnmarshalByteSecret decodes a scalar from prefixed format to native.
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// See https://datatracker.ietf.org/doc/html/draft-ietf-openpgp-crypto-refresh-06#section-5.5.5.6.1.2
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func (c *x448) UnmarshalByteSecret(d []byte) []byte {
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if len(d) != x448lib.Size+1 {
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return nil
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}
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// Store without prefix
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return d[1:]
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}
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func (c *x448) generateKeyPairBytes(rand io.Reader) (sk, pk x448lib.Key, err error) {
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if _, err = rand.Read(sk[:]); err != nil {
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return
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}
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x448lib.KeyGen(&pk, &sk)
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return
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}
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func (c *x448) GenerateECDH(rand io.Reader) (point []byte, secret []byte, err error) {
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priv, pub, err := c.generateKeyPairBytes(rand)
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if err != nil {
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return
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}
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return pub[:], priv[:], nil
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}
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func (c *x448) Encaps(rand io.Reader, point []byte) (ephemeral, sharedSecret []byte, err error) {
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var pk, ss x448lib.Key
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seed, e, err := c.generateKeyPairBytes(rand)
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if err != nil {
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return nil, nil, err
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}
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copy(pk[:], point)
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x448lib.Shared(&ss, &seed, &pk)
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return e[:], ss[:], nil
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}
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func (c *x448) Decaps(ephemeral, secret []byte) (sharedSecret []byte, err error) {
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var ss, sk, e x448lib.Key
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copy(sk[:], secret)
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copy(e[:], ephemeral)
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x448lib.Shared(&ss, &sk, &e)
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return ss[:], nil
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}
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func (c *x448) ValidateECDH(point []byte, secret []byte) error {
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var sk, pk, expectedPk x448lib.Key
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copy(pk[:], point)
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copy(sk[:], secret)
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x448lib.KeyGen(&expectedPk, &sk)
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if subtle.ConstantTimeCompare(expectedPk[:], pk[:]) == 0 {
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return errors.KeyInvalidError("ecc: invalid curve25519 public point")
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}
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return nil
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}
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