// 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 os.Error) {
pk.n.bytes, pk.n.bitLength, err = readMPI(r)
if err != nil {
return
}
pk.e.bytes, pk.e.bitLength, err = readMPI(r)
if err != nil {
return
}
if len(pk.e.bytes) > 3 {
err = error.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
}
func (pk *PublicKey) parse(r io.Reader) (err os.Error) {
// RFC 4880, section 5.5.2
var buf [6]byte
_, err = readFull(r, buf[:])
if err != nil {
return
}
if buf[0] != 4 {
return error.UnsupportedError("public key version")
}
pk.CreationTime = uint32(buf[1])<<24 | uint32(buf[2])<<16 | uint32(buf[3])<<8 | uint32(buf[4])
pk.PubKeyAlgo = PublicKeyAlgorithm(buf[5])
switch pk.PubKeyAlgo {
case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoRSASignOnly:
err = pk.parseRSA(r)
case PubKeyAlgoDSA:
err = pk.parseDSA(r)
default:
err = error.UnsupportedError("public key type")
}
if err != nil {
return
}
// RFC 4880, section 12.2
fingerPrint := sha1.New()
pk.SerializeSignaturePrefix(fingerPrint)
pk.Serialize(fingerPrint)
copy(pk.Fingerprint[:], fingerPrint.Sum())
pk.KeyId = binary.BigEndian.Uint64(pk.Fingerprint[12:20])
return
}
func (pk *PublicKey) parse(r io.Reader) (err os.Error) {
// RFC 4880, section 5.5.2
var buf [6]byte
_, err = readFull(r, buf[:])
if err != nil {
return
}
if buf[0] != 4 {
return error.UnsupportedError("public key version")
}
pk.CreationTime = uint32(buf[1])<<24 | uint32(buf[2])<<16 | uint32(buf[3])<<8 | uint32(buf[4])
pk.PubKeyAlgo = PublicKeyAlgorithm(buf[5])
switch pk.PubKeyAlgo {
case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoRSASignOnly:
err = pk.parseRSA(r)
case PubKeyAlgoDSA:
err = pk.parseDSA(r)
default:
err = error.UnsupportedError("public key type: " + strconv.Itoa(int(pk.PubKeyAlgo)))
}
if err != nil {
return
}
pk.setFingerPrintAndKeyId()
return
}
func (pk *PrivateKey) parse(r io.Reader) (err os.Error) {
err = (&pk.PublicKey).parse(r)
if err != nil {
return
}
var buf [1]byte
_, err = readFull(r, buf[:])
if err != nil {
return
}
s2kType := buf[0]
switch s2kType {
case 0:
pk.s2k = nil
pk.Encrypted = false
case 254, 255:
_, err = readFull(r, buf[:])
if err != nil {
return
}
pk.cipher = CipherFunction(buf[0])
pk.Encrypted = true
pk.s2k, err = s2k.Parse(r)
if err != nil {
return
}
if s2kType == 254 {
pk.sha1Checksum = true
}
default:
return error.UnsupportedError("deprecated s2k function in private key")
}
if pk.Encrypted {
blockSize := pk.cipher.blockSize()
if blockSize == 0 {
return error.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
}
}
pk.encryptedData, err = ioutil.ReadAll(r)
if err != nil {
return
}
if !pk.Encrypted {
return pk.parsePrivateKey(pk.encryptedData)
}
return
}
// hashForSignature returns a pair of hashes that can be used to verify a
// signature. The signature may specify that the contents of the signed message
// should be preprocessed (i.e. to normalise line endings). Thus this function
// returns two hashes. The second should be used to hash the message itself and
// performs any needed preprocessing.
func hashForSignature(hashId crypto.Hash, sigType packet.SignatureType) (hash.Hash, hash.Hash, os.Error) {
h := hashId.New()
if h == nil {
return nil, nil, error.UnsupportedError("hash not availible: " + strconv.Itoa(int(hashId)))
}
switch sigType {
case packet.SigTypeBinary:
return h, h, nil
case packet.SigTypeText:
return h, NewCanonicalTextHash(h), nil
}
return nil, nil, error.UnsupportedError("unsupported signature type: " + strconv.Itoa(int(sigType)))
}
// 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.
func (sig *Signature) Sign(h hash.Hash, priv *PrivateKey) (err os.Error) {
sig.outSubpackets = sig.buildSubpackets()
digest, err := sig.signPrepareHash(h)
if err != nil {
return
}
switch priv.PubKeyAlgo {
case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly:
sig.RSASignature.bytes, err = rsa.SignPKCS1v15(rand.Reader, priv.PrivateKey.(*rsa.PrivateKey), sig.Hash, digest)
sig.RSASignature.bitLength = uint16(8 * len(sig.RSASignature.bytes))
case PubKeyAlgoDSA:
r, s, err := dsa.Sign(rand.Reader, priv.PrivateKey.(*dsa.PrivateKey), digest)
if err == nil {
sig.DSASigR.bytes = r.Bytes()
sig.DSASigR.bitLength = uint16(8 * len(sig.DSASigR.bytes))
sig.DSASigS.bytes = s.Bytes()
sig.DSASigS.bitLength = uint16(8 * len(sig.DSASigS.bytes))
}
default:
err = error.UnsupportedError("public key algorithm: " + strconv.Itoa(int(sig.PubKeyAlgo)))
}
return
}
// Decrypt attempts to decrypt an encrypted session key. If it returns nil,
// ske.Key will contain the session key.
func (ske *SymmetricKeyEncrypted) Decrypt(passphrase []byte) os.Error {
if !ske.Encrypted {
return nil
}
key := make([]byte, ske.CipherFunc.KeySize())
ske.s2k(key, passphrase)
if len(ske.encryptedKey) == 0 {
ske.Key = key
} else {
// the IV is all zeros
iv := make([]byte, ske.CipherFunc.blockSize())
c := cipher.NewCFBDecrypter(ske.CipherFunc.new(key), iv)
c.XORKeyStream(ske.encryptedKey, ske.encryptedKey)
ske.CipherFunc = CipherFunction(ske.encryptedKey[0])
if ske.CipherFunc.blockSize() == 0 {
return error.UnsupportedError("unknown cipher: " + strconv.Itoa(int(ske.CipherFunc)))
}
ske.CipherFunc = CipherFunction(ske.encryptedKey[0])
ske.Key = ske.encryptedKey[1:]
if len(ske.Key)%ske.CipherFunc.blockSize() != 0 {
ske.Key = nil
return error.StructuralError("length of decrypted key not a multiple of block size")
}
}
ske.Encrypted = false
return nil
}
// Parse reads a binary specification for a string-to-key transformation from r
// and returns a function which performs that transform.
func Parse(r io.Reader) (f func(out, in []byte), err os.Error) {
var buf [9]byte
_, err = io.ReadFull(r, buf[:2])
if err != nil {
return
}
hash, ok := HashIdToHash(buf[1])
if !ok {
return nil, error.UnsupportedError("hash for S2K function: " + strconv.Itoa(int(buf[1])))
}
h := hash.New()
if h == nil {
return nil, error.UnsupportedError("hash not available: " + strconv.Itoa(int(hash)))
}
switch buf[0] {
case 1:
f := func(out, in []byte) {
Simple(out, h, in)
}
return f, nil
case 2:
_, err := io.ReadFull(r, buf[:8])
if err != nil {
return
}
f := func(out, in []byte) {
Salted(out, h, in, buf[:8])
}
return f, nil
case 3:
_, err := io.ReadFull(r, buf[:9])
if err != nil {
return
}
count := (16 + int(buf[8]&15)) << (uint32(buf[8]>>4) + 6)
f := func(out, in []byte) {
Iterated(out, h, in, buf[:8], count)
}
return f, nil
}
return nil, error.UnsupportedError("S2K function")
}
// readSignedMessage reads a possibly signed message if mdin is non-zero then
// that structure is updated and returned. Otherwise a fresh MessageDetails is
// used.
func readSignedMessage(packets *packet.Reader, mdin *MessageDetails, keyring KeyRing) (md *MessageDetails, err os.Error) {
if mdin == nil {
mdin = new(MessageDetails)
}
md = mdin
var p packet.Packet
var h hash.Hash
var wrappedHash hash.Hash
FindLiteralData:
for {
p, err = packets.Next()
if err != nil {
return nil, err
}
switch p := p.(type) {
case *packet.Compressed:
packets.Push(p.Body)
case *packet.OnePassSignature:
if !p.IsLast {
return nil, error.UnsupportedError("nested signatures")
}
h, wrappedHash, err = hashForSignature(p.Hash, p.SigType)
if err != nil {
md = nil
return
}
md.IsSigned = true
md.SignedByKeyId = p.KeyId
keys := keyring.KeysById(p.KeyId)
for i, key := range keys {
if key.SelfSignature.FlagsValid && !key.SelfSignature.FlagSign {
continue
}
md.SignedBy = &keys[i]
break
}
case *packet.LiteralData:
md.LiteralData = p
break FindLiteralData
}
}
if md.SignedBy != nil {
md.UnverifiedBody = &signatureCheckReader{packets, h, wrappedHash, md}
} else if md.decrypted != nil {
md.UnverifiedBody = checkReader{md}
} else {
md.UnverifiedBody = md.LiteralData.Body
}
return md, nil
}
// Parse reads a binary specification for a string-to-key transformation from r
// and returns a function which performs that transform.
func Parse(r io.Reader) (f func(out, in []byte), err os.Error) {
var buf [9]byte
_, err = io.ReadFull(r, buf[:2])
if err != nil {
return
}
h := hashFuncFromType(buf[1])
if h == nil {
return nil, error.UnsupportedError("hash for S2K function")
}
switch buf[0] {
case 1:
f := func(out, in []byte) {
Simple(out, h, in)
}
return f, nil
case 2:
_, err := io.ReadFull(r, buf[:8])
if err != nil {
return
}
f := func(out, in []byte) {
Salted(out, h, in, buf[:8])
}
return f, nil
case 3:
_, err := io.ReadFull(r, buf[:9])
if err != nil {
return
}
count := (16 + int(buf[8]&15)) << (uint32(buf[8]>>4) + 6)
f := func(out, in []byte) {
Iterated(out, h, in, buf[:8], count)
}
return f, nil
}
return nil, error.UnsupportedError("S2K function")
}
func (ske *SymmetricKeyEncrypted) parse(r io.Reader) (err os.Error) {
// RFC 4880, section 5.3.
var buf [2]byte
_, err = readFull(r, buf[:])
if err != nil {
return
}
if buf[0] != symmetricKeyEncryptedVersion {
return error.UnsupportedError("SymmetricKeyEncrypted version")
}
ske.CipherFunc = CipherFunction(buf[1])
if ske.CipherFunc.KeySize() == 0 {
return error.UnsupportedError("unknown cipher: " + strconv.Itoa(int(buf[1])))
}
ske.s2k, err = s2k.Parse(r)
if err != nil {
return
}
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 = nil
if n != 0 {
if n == maxSessionKeySizeInBytes {
return error.UnsupportedError("oversized encrypted session key")
}
ske.encryptedKey = encryptedKey[:n]
}
ske.Encrypted = true
return
}
// 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.
func SerializeSymmetricKeyEncrypted(w io.Writer, rand io.Reader, passphrase []byte, cipherFunc CipherFunction) (key []byte, err os.Error) {
keySize := cipherFunc.KeySize()
if keySize == 0 {
return nil, error.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, rand, passphrase)
if err != nil {
return
}
s2kBytes := s2kBuf.Bytes()
packetLength := 2 /* header */ + len(s2kBytes) + 1 /* cipher type */ + keySize
err = serializeHeader(w, packetTypeSymmetricKeyEncrypted, packetLength)
if err != nil {
return
}
var buf [2]byte
buf[0] = symmetricKeyEncryptedVersion
buf[1] = byte(cipherFunc)
_, err = w.Write(buf[:])
if err != nil {
return
}
_, err = w.Write(s2kBytes)
if err != nil {
return
}
sessionKey := make([]byte, keySize)
_, err = io.ReadFull(rand, sessionKey)
if err != nil {
return
}
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
}
key = sessionKey
return
}
// 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 *PublicKey, sig *Signature) (h hash.Hash, err os.Error) {
h = sig.Hash.New()
if h == nil {
return nil, error.UnsupportedError("hash function")
}
// RFC 4880, section 5.2.4
pk.SerializeSignaturePrefix(h)
pk.serializeWithoutHeaders(h)
signed.SerializeSignaturePrefix(h)
signed.serializeWithoutHeaders(h)
return
}
// VerifyKeySignature returns nil iff sig is a valid signature, make by this
// public key, of the public key in signed.
func (pk *PublicKey) VerifyKeySignature(signed *PublicKey, sig *Signature) (err os.Error) {
h := sig.Hash.New()
if h == nil {
return error.UnsupportedError("hash function")
}
// RFC 4880, section 5.2.4
pk.SerializeSignaturePrefix(h)
pk.Serialize(h)
signed.SerializeSignaturePrefix(h)
signed.Serialize(h)
return pk.VerifySignature(h, sig)
}
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 = error_.UnsupportedError("one-pass-signature packet version " + strconv.Itoa(int(buf[0])))
}
var ok bool
ops.Hash, ok = s2k.HashIdToHash(buf[2])
if !ok {
return error_.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
}
func (se *SymmetricallyEncrypted) parse(r io.Reader) os.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 error.UnsupportedError("unknown SymmetricallyEncrypted version")
}
}
se.contents = r
return nil
}
// 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.
func (sig *Signature) Sign(h hash.Hash, priv *PrivateKey) (err os.Error) {
digest, err := sig.signPrepareHash(h)
if err != nil {
return
}
switch priv.PubKeyAlgo {
case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly:
sig.RSASignature, err = rsa.SignPKCS1v15(rand.Reader, priv.PrivateKey.(*rsa.PrivateKey), sig.Hash, digest)
case PubKeyAlgoDSA:
sig.DSASigR, sig.DSASigS, err = dsa.Sign(rand.Reader, priv.PrivateKey.(*dsa.PrivateKey), digest)
default:
err = error.UnsupportedError("public key algorithm: " + strconv.Itoa(int(sig.PubKeyAlgo)))
}
return
}
func (e *EncryptedKey) parse(r io.Reader) (err os.Error) {
var buf [10]byte
_, err = readFull(r, buf[:])
if err != nil {
return
}
if buf[0] != 3 {
return error.UnsupportedError("unknown EncryptedKey version " + strconv.Itoa(int(buf[0])))
}
e.KeyId = binary.BigEndian.Uint64(buf[1:9])
e.Algo = PublicKeyAlgorithm(buf[9])
if e.Algo == PubKeyAlgoRSA || e.Algo == PubKeyAlgoRSAEncryptOnly {
e.Encrypted, _, err = readMPI(r)
}
_, err = consumeAll(r)
return
}
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)
default:
err = error_.UnsupportedError("unknown compression algorithm: " + strconv.Itoa(int(buf[0])))
}
return err
}
// Decrypt returns a ReadCloser, from which the decrypted contents of the
// packet can be read. An incorrect key can, with high probability, be detected
// immediately and this will result in a KeyIncorrect error being returned.
func (se *SymmetricallyEncrypted) Decrypt(c CipherFunction, key []byte) (io.ReadCloser, os.Error) {
keySize := c.KeySize()
if keySize == 0 {
return nil, error.UnsupportedError("unknown cipher: " + strconv.Itoa(int(c)))
}
if len(key) != keySize {
return nil, error.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, error.InvalidArgumentError("can't try ciphers with different block lengths")
}
ocfbResync := cipher.OCFBResync
if se.MDC {
// MDC packets use a different form of OCFB mode.
ocfbResync = cipher.OCFBNoResync
}
s := cipher.NewOCFBDecrypter(c.new(key), se.prefix, ocfbResync)
if s == nil {
return nil, error.KeyIncorrectError
}
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
}
// 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, sig *Signature) (h hash.Hash, err os.Error) {
h = sig.Hash.New()
if h == nil {
return nil, error.UnsupportedError("hash function")
}
// 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
}
// 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 error_.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
}
// VerifyUserIdSignature returns nil iff sig is a valid signature, make by this
// public key, of the given user id.
func (pk *PublicKey) VerifyUserIdSignature(id string, sig *Signature) (err os.Error) {
h := sig.Hash.New()
if h == nil {
return error.UnsupportedError("hash function")
}
// RFC 4880, section 5.2.4
pk.SerializeSignaturePrefix(h)
pk.Serialize(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 pk.VerifySignature(h, sig)
}
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 error_.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, _, err = readMPI(r)
case PubKeyAlgoElGamal:
e.encryptedMPI1, _, err = readMPI(r)
if err != nil {
return
}
e.encryptedMPI2, _, err = readMPI(r)
}
_, err = consumeAll(r)
return
}
// SerializeEncryptedKey serializes an encrypted key packet to w that contains
// key, encrypted to pub.
func SerializeEncryptedKey(w io.Writer, rand io.Reader, pub *PublicKey, cipherFunc CipherFunction, key []byte) 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, rand, buf, pub.PublicKey.(*rsa.PublicKey), keyBlock)
case PubKeyAlgoElGamal:
return serializeEncryptedKeyElGamal(w, rand, buf, pub.PublicKey.(*elgamal.PublicKey), keyBlock)
case PubKeyAlgoDSA, PubKeyAlgoRSASignOnly:
return error_.InvalidArgumentError("cannot encrypt to public key of type " + strconv.Itoa(int(pub.PubKeyAlgo)))
}
return error_.UnsupportedError("encrypting a key to public key of type " + strconv.Itoa(int(pub.PubKeyAlgo)))
}
func (sig *Signature) parse(r io.Reader) (err os.Error) {
// RFC 4880, section 5.2.3
var buf [5]byte
_, err = readFull(r, buf[:1])
if err != nil {
return
}
if buf[0] != 4 {
err = error.UnsupportedError("signature packet version " + strconv.Itoa(int(buf[0])))
return
}
_, 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:
default:
err = error.UnsupportedError("public key algorithm " + strconv.Itoa(int(sig.PubKeyAlgo)))
return
}
var ok bool
sig.Hash, ok = s2k.HashIdToHash(buf[2])
if !ok {
return error.UnsupportedError("hash function " + strconv.Itoa(int(buf[2])))
}
hashedSubpacketsLength := int(buf[3])<<8 | int(buf[4])
l := 6 + hashedSubpacketsLength
sig.HashSuffix = make([]byte, l+6)
sig.HashSuffix[0] = 4
copy(sig.HashSuffix[1:], buf[:5])
hashedSubpackets := sig.HashSuffix[6:l]
_, err = readFull(r, hashedSubpackets)
if err != nil {
return
}
// See RFC 4880, section 5.2.4
trailer := sig.HashSuffix[l:]
trailer[0] = 4
trailer[1] = 0xff
trailer[2] = uint8(l >> 24)
trailer[3] = uint8(l >> 16)
trailer[4] = uint8(l >> 8)
trailer[5] = uint8(l)
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.bytes, sig.RSASignature.bitLength, err = readMPI(r)
case PubKeyAlgoDSA:
sig.DSASigR.bytes, sig.DSASigR.bitLength, err = readMPI(r)
if err == nil {
sig.DSASigS.bytes, sig.DSASigS.bitLength, err = readMPI(r)
}
default:
panic("unreachable")
}
return
}
// parseSignatureSubpacket parses a single subpacket. len(subpacket) is >= 1.
func parseSignatureSubpacket(sig *Signature, subpacket []byte, isHashed bool) (rest []byte, err os.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 = error.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 = error.StructuralError("signature creation time in non-hashed area")
return
}
if len(subpacket) != 4 {
err = error.StructuralError("signature creation time not four bytes")
return
}
sig.CreationTime = binary.BigEndian.Uint32(subpacket)
case signatureExpirationSubpacket:
// Signature expiration time, section 5.2.3.10
if !isHashed {
return
}
if len(subpacket) != 4 {
err = error.StructuralError("expiration subpacket with bad length")
return
}
sig.SigLifetimeSecs = new(uint32)
*sig.SigLifetimeSecs = binary.BigEndian.Uint32(subpacket)
case keyExpirySubpacket:
// Key expiration time, section 5.2.3.6
if !isHashed {
return
}
if len(subpacket) != 4 {
err = error.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:
// Issuer, section 5.2.3.5
if len(subpacket) != 8 {
err = error.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 = error.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 = error.StructuralError("empty key flags subpacket")
return
}
sig.FlagsValid = true
if subpacket[0]&1 != 0 {
sig.FlagCertify = true
}
if subpacket[0]&2 != 0 {
sig.FlagSign = true
}
if subpacket[0]&4 != 0 {
sig.FlagEncryptCommunications = true
}
if subpacket[0]&8 != 0 {
sig.FlagEncryptStorage = true
}
default:
if isCritical {
err = error.UnsupportedError("unknown critical signature subpacket type " + strconv.Itoa(int(packetType)))
return
}
}
return
Truncated:
err = error.StructuralError("signature subpacket truncated")
return
}
