chore: modernize CI and update Go toolchain

- Bump Go from 1.19 to 1.26 and update all dependencies
- Rewrite CI workflow with matrix strategy (Linux, macOS, Windows)
- Update GitHub Actions to current versions (checkout@v4, setup-go@v5)
- Update CodeQL actions from v1 to v3
- Fix cross-platform bug in mock/path.go (path.Join -> filepath.Join)
- Clean up dependabot config (weekly schedule, remove stale ignore)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

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

@@ -6,9 +6,22 @@
 package errors // import "github.com/ProtonMail/go-crypto/openpgp/errors"
 
 import (
+	"fmt"
 	"strconv"
 )
 
+var (
+	// ErrDecryptSessionKeyParsing is a generic error message for parsing errors in decrypted data
+	// to reduce the risk of oracle attacks.
+	ErrDecryptSessionKeyParsing = DecryptWithSessionKeyError("parsing error")
+	// ErrAEADTagVerification is returned if one of the tag verifications in SEIPDv2 fails
+	ErrAEADTagVerification error = DecryptWithSessionKeyError("AEAD tag verification failed")
+	// ErrMDCHashMismatch
+	ErrMDCHashMismatch error = SignatureError("MDC hash mismatch")
+	// ErrMDCMissing
+	ErrMDCMissing error = SignatureError("MDC packet not found")
+)
+
 // A StructuralError is returned when OpenPGP data is found to be syntactically
 // invalid.
 type StructuralError string
@@ -17,6 +30,34 @@ func (s StructuralError) Error() string {
 	return "openpgp: invalid data: " + string(s)
 }
 
+// A DecryptWithSessionKeyError is returned when a failure occurs when reading from symmetrically decrypted data or
+// an authentication tag verification fails.
+// Such an error indicates that the supplied session key is likely wrong or the data got corrupted.
+type DecryptWithSessionKeyError string
+
+func (s DecryptWithSessionKeyError) Error() string {
+	return "openpgp: decryption with session key failed: " + string(s)
+}
+
+// HandleSensitiveParsingError handles parsing errors when reading data from potentially decrypted data.
+// The function makes parsing errors generic to reduce the risk of oracle attacks in SEIPDv1.
+func HandleSensitiveParsingError(err error, decrypted bool) error {
+	if !decrypted {
+		// Data was not encrypted so we return the inner error.
+		return err
+	}
+	// The data is read from a stream that decrypts using a session key;
+	// therefore, we need to handle parsing errors appropriately.
+	// This is essential to mitigate the risk of oracle attacks.
+	if decError, ok := err.(*DecryptWithSessionKeyError); ok {
+		return decError
+	}
+	if decError, ok := err.(DecryptWithSessionKeyError); ok {
+		return decError
+	}
+	return ErrDecryptSessionKeyParsing
+}
+
 // UnsupportedError indicates that, although the OpenPGP data is valid, it
 // makes use of currently unimplemented features.
 type UnsupportedError string
@@ -41,9 +82,6 @@ func (b SignatureError) Error() string {
 	return "openpgp: invalid signature: " + string(b)
 }
 
-var ErrMDCHashMismatch error = SignatureError("MDC hash mismatch")
-var ErrMDCMissing error = SignatureError("MDC packet not found")
-
 type signatureExpiredError int
 
 func (se signatureExpiredError) Error() string {
@@ -58,6 +96,14 @@ func (ke keyExpiredError) Error() string {
 	return "openpgp: key expired"
 }
 
+var ErrSignatureOlderThanKey error = signatureOlderThanKeyError(0)
+
+type signatureOlderThanKeyError int
+
+func (ske signatureOlderThanKeyError) Error() string {
+	return "openpgp: signature is older than the key"
+}
+
 var ErrKeyExpired error = keyExpiredError(0)
 
 type keyIncorrectError int
@@ -92,12 +138,24 @@ func (keyRevokedError) Error() string {
 
 var ErrKeyRevoked error = keyRevokedError(0)
 
+type WeakAlgorithmError string
+
+func (e WeakAlgorithmError) Error() string {
+	return "openpgp: weak algorithms are rejected: " + string(e)
+}
+
 type UnknownPacketTypeError uint8
 
 func (upte UnknownPacketTypeError) Error() string {
 	return "openpgp: unknown packet type: " + strconv.Itoa(int(upte))
 }
 
+type CriticalUnknownPacketTypeError uint8
+
+func (upte CriticalUnknownPacketTypeError) Error() string {
+	return "openpgp: unknown critical packet type: " + strconv.Itoa(int(upte))
+}
+
 // AEADError indicates that there is a problem when initializing or using a
 // AEAD instance, configuration struct, nonces or index values.
 type AEADError string
@@ -114,3 +172,39 @@ type ErrDummyPrivateKey string
 func (dke ErrDummyPrivateKey) Error() string {
 	return "openpgp: s2k GNU dummy key: " + string(dke)
 }
+
+// ErrMalformedMessage results when the packet sequence is incorrect
+type ErrMalformedMessage string
+
+func (dke ErrMalformedMessage) Error() string {
+	return "openpgp: malformed message " + string(dke)
+}
+
+type messageTooLargeError int
+
+func (e messageTooLargeError) Error() string {
+	return "openpgp: decompressed message size exceeds provided limit"
+}
+
+// ErrMessageTooLarge is returned if the read data from
+// a compressed packet exceeds the provided limit.
+var ErrMessageTooLarge error = messageTooLargeError(0)
+
+// ErrEncryptionKeySelection is returned if encryption key selection fails (v2 API).
+type ErrEncryptionKeySelection struct {
+	PrimaryKeyId      string
+	PrimaryKeyErr     error
+	EncSelectionKeyId *string
+	EncSelectionErr   error
+}
+
+func (eks ErrEncryptionKeySelection) Error() string {
+	prefix := fmt.Sprintf("openpgp: key selection for primary key %s:", eks.PrimaryKeyId)
+	if eks.PrimaryKeyErr != nil {
+		return fmt.Sprintf("%s invalid primary key: %s", prefix, eks.PrimaryKeyErr)
+	}
+	if eks.EncSelectionKeyId != nil {
+		return fmt.Sprintf("%s invalid encryption key %s: %s", prefix, *eks.EncSelectionKeyId, eks.EncSelectionErr)
+	}
+	return fmt.Sprintf("%s no encryption key: %s", prefix, eks.EncSelectionErr)
+}