func detachSign(w io.Writer, signer *Entity, message io.Reader, sigType packet.SignatureType, config *packet.Config) (err error) {
if signer.PrivateKey == nil {
return errors.InvalidArgumentError("signing key doesn't have a private key")
}
if signer.PrivateKey.Encrypted {
return errors.InvalidArgumentError("signing key is encrypted")
}
sig := new(packet.Signature)
sig.SigType = sigType
sig.PubKeyAlgo = signer.PrivateKey.PubKeyAlgo
sig.Hash = config.Hash()
sig.CreationTime = config.Now()
sig.IssuerKeyId = &signer.PrivateKey.KeyId
h, wrappedHash, err := hashForSignature(sig.Hash, sig.SigType)
if err != nil {
return
}
io.Copy(wrappedHash, message)
err = sig.Sign(h, signer.PrivateKey, config)
if err != nil {
return
}
return sig.Serialize(w)
}
// VerifySignatureV3 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 *PublicKeyV3) VerifySignatureV3(signed hash.Hash, sig *SignatureV3) (err error) {
if !pk.CanSign() {
return errors.InvalidArgumentError("public key cannot generate signatures")
}
suffix := make([]byte, 5)
suffix[0] = byte(sig.SigType)
binary.BigEndian.PutUint32(suffix[1:], uint32(sig.CreationTime.Unix()))
signed.Write(suffix)
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:
if err = rsa.VerifyPKCS1v15(pk.PublicKey, sig.Hash, hashBytes, sig.RSASignature.bytes); err != nil {
return errors.SignatureError("RSA verification failure")
}
return
default:
// V3 public keys only support RSA.
panic("shouldn't happen")
}
panic("unreachable")
}
// SignIdentity adds a signature to e, from signer, attesting that identity is
// associated with e. The provided identity must already be an element of
// e.Identities and the private key of signer must have been decrypted if
// necessary.
// If config is nil, sensible defaults will be used.
func (e *Entity) SignIdentity(identity string, signer *Entity, config *packet.Config) error {
if signer.PrivateKey == nil {
return errors.InvalidArgumentError("signing Entity must have a private key")
}
if signer.PrivateKey.Encrypted {
return errors.InvalidArgumentError("signing Entity's private key must be decrypted")
}
ident, ok := e.Identities[identity]
if !ok {
return errors.InvalidArgumentError("given identity string not found in Entity")
}
sig := &packet.Signature{
SigType: packet.SigTypeGenericCert,
PubKeyAlgo: signer.PrivateKey.PubKeyAlgo,
Hash: config.Hash(),
CreationTime: config.Now(),
IssuerKeyId: &signer.PrivateKey.KeyId,
}
if err := sig.SignKey(e.PrimaryKey, signer.PrivateKey, config); err != nil {
return err
}
ident.Signatures = append(ident.Signatures, sig)
return nil
}
// ReadArmoredKeyRing reads one or more public/private keys from an armor keyring file.
func ReadArmoredKeyRing(r io.Reader) (EntityList, error) {
block, err := armor.Decode(r)
if err == io.EOF {
return nil, errors.InvalidArgumentError("no armored data found")
}
if err != nil {
return nil, err
}
if block.Type != PublicKeyType && block.Type != PrivateKeyType {
return nil, errors.InvalidArgumentError("expected public or private key block, got: " + block.Type)
}
return ReadKeyRing(block.Body)
}
// serializeWithoutHeaders marshals the PublicKey to w in the form of an
// OpenPGP public key packet, not including the packet header.
func (pk *PublicKeyV3) serializeWithoutHeaders(w io.Writer) (err error) {
var buf [8]byte
// Version 3
buf[0] = 3
// Creation time
t := uint32(pk.CreationTime.Unix())
buf[1] = byte(t >> 24)
buf[2] = byte(t >> 16)
buf[3] = byte(t >> 8)
buf[4] = byte(t)
// Days to expire
buf[5] = byte(pk.DaysToExpire >> 8)
buf[6] = byte(pk.DaysToExpire)
// Public key algorithm
buf[7] = byte(pk.PubKeyAlgo)
if _, err = w.Write(buf[:]); err != nil {
return
}
switch pk.PubKeyAlgo {
case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoRSASignOnly:
return writeMPIs(w, pk.n, pk.e)
}
return errors.InvalidArgumentError("bad public-key algorithm")
}
// 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 {
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:
b, err = rsa.DecryptPKCS1v15(config.Random(), priv.PrivateKey.(*rsa.PrivateKey), e.encryptedMPI1)
case PubKeyAlgoElGamal:
c1 := new(big.Int).SetBytes(e.encryptedMPI1)
c2 := new(big.Int).SetBytes(e.encryptedMPI2)
b, err = elgamal.Decrypt(priv.PrivateKey.(*elgamal.PrivateKey), c1, c2)
default:
err = errors.InvalidArgumentError("cannot decrypted 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
}
// 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
}
// 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) {
var buf [6]byte
buf[0] = 4
t := uint32(pk.CreationTime.Unix())
buf[1] = byte(t >> 24)
buf[2] = byte(t >> 16)
buf[3] = byte(t >> 8)
buf[4] = byte(t)
buf[5] = byte(pk.PubKeyAlgo)
_, err = w.Write(buf[:])
if err != nil {
return
}
switch pk.PubKeyAlgo {
case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoRSASignOnly:
return writeMPIs(w, pk.n, pk.e)
case PubKeyAlgoDSA:
return writeMPIs(w, pk.p, pk.q, pk.g, pk.y)
case PubKeyAlgoElGamal:
return writeMPIs(w, pk.p, pk.g, pk.y)
}
return errors.InvalidArgumentError("bad public-key algorithm")
}
// buildHashSuffix constructs the HashSuffix member of sig in preparation for signing.
func (sig *Signature) buildHashSuffix() (err error) {
hashedSubpacketsLen := subpacketsLength(sig.outSubpackets, true)
var ok bool
l := 6 + hashedSubpacketsLen
sig.HashSuffix = make([]byte, l+6)
sig.HashSuffix[0] = 4
sig.HashSuffix[1] = uint8(sig.SigType)
sig.HashSuffix[2] = uint8(sig.PubKeyAlgo)
sig.HashSuffix[3], ok = s2k.HashToHashId(sig.Hash)
if !ok {
sig.HashSuffix = nil
return errors.InvalidArgumentError("hash cannot be represented in OpenPGP: " + strconv.Itoa(int(sig.Hash)))
}
sig.HashSuffix[4] = byte(hashedSubpacketsLen >> 8)
sig.HashSuffix[5] = byte(hashedSubpacketsLen)
serializeSubpackets(sig.HashSuffix[6:l], sig.outSubpackets, true)
trailer := sig.HashSuffix[l:]
trailer[0] = 4
trailer[1] = 0xff
trailer[2] = byte(l >> 24)
trailer[3] = byte(l >> 16)
trailer[4] = byte(l >> 8)
trailer[5] = byte(l)
return
}
// 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")
}
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, 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
default:
return errors.SignatureError("Unsupported public key algorithm used in signature")
}
panic("unreachable")
}
// NewEntity returns an Entity that contains a fresh RSA/RSA keypair with a
// single identity composed of the given full name, comment and email, any of
// which may be empty but must not contain any of "()<>\x00".
// If config is nil, sensible defaults will be used.
func NewEntity(name, comment, email string, config *packet.Config) (*Entity, error) {
currentTime := config.Now()
uid := packet.NewUserId(name, comment, email)
if uid == nil {
return nil, errors.InvalidArgumentError("user id field contained invalid characters")
}
signingPriv, err := rsa.GenerateKey(config.Random(), defaultRSAKeyBits)
if err != nil {
return nil, err
}
encryptingPriv, err := rsa.GenerateKey(config.Random(), defaultRSAKeyBits)
if err != nil {
return nil, err
}
e := &Entity{
PrimaryKey: packet.NewRSAPublicKey(currentTime, &signingPriv.PublicKey),
PrivateKey: packet.NewRSAPrivateKey(currentTime, signingPriv),
Identities: make(map[string]*Identity),
}
isPrimaryId := true
e.Identities[uid.Id] = &Identity{
Name: uid.Name,
UserId: uid,
SelfSignature: &packet.Signature{
CreationTime: currentTime,
SigType: packet.SigTypePositiveCert,
PubKeyAlgo: packet.PubKeyAlgoRSA,
Hash: config.Hash(),
IsPrimaryId: &isPrimaryId,
FlagsValid: true,
FlagSign: true,
FlagCertify: true,
IssuerKeyId: &e.PrimaryKey.KeyId,
},
}
e.Subkeys = make([]Subkey, 1)
e.Subkeys[0] = Subkey{
PublicKey: packet.NewRSAPublicKey(currentTime, &encryptingPriv.PublicKey),
PrivateKey: packet.NewRSAPrivateKey(currentTime, encryptingPriv),
Sig: &packet.Signature{
CreationTime: currentTime,
SigType: packet.SigTypeSubkeyBinding,
PubKeyAlgo: packet.PubKeyAlgoRSA,
Hash: config.Hash(),
FlagsValid: true,
FlagEncryptStorage: true,
FlagEncryptCommunications: true,
IssuerKeyId: &e.PrimaryKey.KeyId,
},
}
e.Subkeys[0].PublicKey.IsSubkey = true
e.Subkeys[0].PrivateKey.IsSubkey = true
return e, nil
}
// BitLength returns the bit length for the given public key.
func (pk *PublicKeyV3) BitLength() (bitLength uint16, err error) {
switch pk.PubKeyAlgo {
case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly, PubKeyAlgoRSASignOnly:
bitLength = pk.n.bitLength
default:
err = errors.InvalidArgumentError("bad public-key algorithm")
}
return
}
// Serialize marshals sig to w. SignRSA or SignDSA 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.bytes == nil && sig.DSASigR.bytes == nil {
return errors.InvalidArgumentError("Signature: need to call SignRSA or SignDSA before Serialize")
}
sigLength := 0
switch sig.PubKeyAlgo {
case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly:
sigLength = 2 + len(sig.RSASignature.bytes)
case PubKeyAlgoDSA:
sigLength = 2 + len(sig.DSASigR.bytes)
sigLength += 2 + len(sig.DSASigS.bytes)
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
err = serializeHeader(w, packetTypeSignature, length)
if err != nil {
return
}
_, err = w.Write(sig.HashSuffix[:len(sig.HashSuffix)-6])
if err != nil {
return
}
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 = writeMPIs(w, sig.RSASignature)
case PubKeyAlgoDSA:
err = writeMPIs(w, sig.DSASigR, sig.DSASigS)
default:
panic("impossible")
}
return
}
// 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, 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)
if s == nil {
return nil, errors.ErrKeyIncorrect
}
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
}
// VerifySignatureV3 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) VerifySignatureV3(signed hash.Hash, sig *SignatureV3) (err error) {
if !pk.CanSign() {
return errors.InvalidArgumentError("public key cannot generate signatures")
}
suffix := make([]byte, 5)
suffix[0] = byte(sig.SigType)
binary.BigEndian.PutUint32(suffix[1:], uint32(sig.CreationTime.Unix()))
signed.Write(suffix)
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)
if err = rsa.VerifyPKCS1v15(rsaPublicKey, sig.Hash, hashBytes, sig.RSASignature.bytes); err != nil {
return errors.SignatureError("RSA verification failure")
}
return
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
default:
panic("shouldn't happen")
}
panic("unreachable")
}
// readArmored reads an armored block with the given type.
func readArmored(r io.Reader, expectedType string) (body io.Reader, err error) {
block, err := armor.Decode(r)
if err != nil {
return
}
if block.Type != expectedType {
return nil, errors.InvalidArgumentError("expected '" + expectedType + "', got: " + block.Type)
}
return block.Body, nil
}
// Encode returns a WriteCloser which will clear-sign a message with privateKey
// and write it to w. If config is nil, sensible defaults are used.
func Encode(w io.Writer, privateKey *packet.PrivateKey, config *packet.Config) (plaintext io.WriteCloser, err error) {
if privateKey.Encrypted {
return nil, errors.InvalidArgumentError("signing key is encrypted")
}
hashType := config.Hash()
name := nameOfHash(hashType)
if len(name) == 0 {
return nil, errors.UnsupportedError("unknown hash type: " + strconv.Itoa(int(hashType)))
}
h := hashType.New()
if h == nil {
return nil, errors.UnsupportedError("unsupported hash type: " + strconv.Itoa(int(hashType)))
}
buffered := bufio.NewWriter(w)
// start has a \n at the beginning that we don't want here.
if _, err = buffered.Write(start[1:]); err != nil {
return
}
if err = buffered.WriteByte(lf); err != nil {
return
}
if _, err = buffered.WriteString("Hash: "); err != nil {
return
}
if _, err = buffered.WriteString(name); err != nil {
return
}
if err = buffered.WriteByte(lf); err != nil {
return
}
if err = buffered.WriteByte(lf); err != nil {
return
}
plaintext = &dashEscaper{
buffered: buffered,
h: h,
hashType: hashType,
atBeginningOfLine: true,
isFirstLine: true,
byteBuf: make([]byte, 1),
privateKey: privateKey,
config: config,
}
return
}
func (pk *PrivateKey) Serialize(w io.Writer) (err error) {
// TODO(agl): support encrypted private keys
buf := bytes.NewBuffer(nil)
err = pk.PublicKey.serializeWithoutHeaders(buf)
if err != nil {
return
}
buf.WriteByte(0 /* no encryption */ )
privateKeyBuf := bytes.NewBuffer(nil)
switch priv := pk.PrivateKey.(type) {
case *rsa.PrivateKey:
err = serializeRSAPrivateKey(privateKeyBuf, priv)
case *dsa.PrivateKey:
err = serializeDSAPrivateKey(privateKeyBuf, priv)
default:
err = errors.InvalidArgumentError("unknown private key type")
}
if err != nil {
return
}
ptype := packetTypePrivateKey
contents := buf.Bytes()
privateKeyBytes := privateKeyBuf.Bytes()
if pk.IsSubkey {
ptype = packetTypePrivateSubkey
}
err = serializeHeader(w, ptype, len(contents)+len(privateKeyBytes)+2)
if err != nil {
return
}
_, err = w.Write(contents)
if err != nil {
return
}
_, err = w.Write(privateKeyBytes)
if err != nil {
return
}
checksum := mod64kHash(privateKeyBytes)
var checksumBytes [2]byte
checksumBytes[0] = byte(checksum >> 8)
checksumBytes[1] = byte(checksum)
_, err = w.Write(checksumBytes[:])
return
}
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())
}
packetLen := 10 /* header length */ + 2 /* mpi size */ + len(cipherText)
err = serializeHeader(w, packetTypeEncryptedKey, packetLen)
if err != nil {
return err
}
_, err = w.Write(header[:])
if err != nil {
return err
}
return writeMPI(w, 8*uint16(len(cipherText)), cipherText)
}
// Serialize marshals sig to w. Sign, SignUserId or SignKey must have been
// called first.
func (sig *SignatureV3) Serialize(w io.Writer) (err error) {
buf := make([]byte, 8)
// Write the sig type and creation time
buf[0] = byte(sig.SigType)
binary.BigEndian.PutUint32(buf[1:5], uint32(sig.CreationTime.Unix()))
if _, err = w.Write(buf[:5]); err != nil {
return
}
// Write the issuer long key ID
binary.BigEndian.PutUint64(buf[:8], sig.IssuerKeyId)
if _, err = w.Write(buf[:8]); err != nil {
return
}
// Write public key algorithm, hash ID, and hash value
buf[0] = byte(sig.PubKeyAlgo)
hashId, ok := s2k.HashToHashId(sig.Hash)
if !ok {
return errors.UnsupportedError(fmt.Sprintf("hash function %v", sig.Hash))
}
buf[1] = hashId
copy(buf[2:4], sig.HashTag[:])
if _, err = w.Write(buf[:4]); err != nil {
return
}
if sig.RSASignature.bytes == nil && sig.DSASigR.bytes == nil {
return errors.InvalidArgumentError("Signature: need to call Sign, SignUserId or SignKey before Serialize")
}
switch sig.PubKeyAlgo {
case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly:
err = writeMPIs(w, sig.RSASignature)
case PubKeyAlgoDSA:
err = writeMPIs(w, sig.DSASigR, sig.DSASigS)
default:
panic("impossible")
}
return
}
// 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 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 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
}
err = writeBig(w, c1)
if err != nil {
return err
}
return writeBig(w, c2)
}
// Encrypt encrypts a message to a number of recipients and, optionally, signs
// it. hints contains optional information, that is also encrypted, that aids
// the recipients in processing the message. The resulting WriteCloser must
// be closed after the contents of the file have been written.
// If config is nil, sensible defaults will be used.
func Encrypt(ciphertext io.Writer, to []*Entity, signed *Entity, hints *FileHints, config *packet.Config) (plaintext io.WriteCloser, err error) {
var signer *packet.PrivateKey
if signed != nil {
signKey, ok := signed.signingKey(config.Now())
if !ok {
return nil, errors.InvalidArgumentError("no valid signing keys")
}
signer = signKey.PrivateKey
if signer.Encrypted {
return nil, errors.InvalidArgumentError("signing key must be decrypted")
}
}
// These are the possible ciphers that we'll use for the message.
candidateCiphers := []uint8{
uint8(packet.CipherAES128),
uint8(packet.CipherAES256),
uint8(packet.CipherCAST5),
}
// These are the possible hash functions that we'll use for the signature.
candidateHashes := []uint8{
hashToHashId(crypto.SHA256),
hashToHashId(crypto.SHA512),
hashToHashId(crypto.SHA1),
hashToHashId(crypto.RIPEMD160),
}
// In the event that a recipient doesn't specify any supported ciphers
// or hash functions, these are the ones that we assume that every
// implementation supports.
defaultCiphers := candidateCiphers[len(candidateCiphers)-1:]
defaultHashes := candidateHashes[len(candidateHashes)-1:]
encryptKeys := make([]Key, len(to))
for i := range to {
var ok bool
encryptKeys[i], ok = to[i].encryptionKey(config.Now())
if !ok {
return nil, errors.InvalidArgumentError("cannot encrypt a message to key id " + strconv.FormatUint(to[i].PrimaryKey.KeyId, 16) + " because it has no encryption keys")
}
sig := to[i].primaryIdentity().SelfSignature
preferredSymmetric := sig.PreferredSymmetric
if len(preferredSymmetric) == 0 {
preferredSymmetric = defaultCiphers
}
preferredHashes := sig.PreferredHash
if len(preferredHashes) == 0 {
preferredHashes = defaultHashes
}
candidateCiphers = intersectPreferences(candidateCiphers, preferredSymmetric)
candidateHashes = intersectPreferences(candidateHashes, preferredHashes)
}
if len(candidateCiphers) == 0 || len(candidateHashes) == 0 {
return nil, errors.InvalidArgumentError("cannot encrypt because recipient set shares no common algorithms")
}
cipher := packet.CipherFunction(candidateCiphers[0])
// If the cipher specifed by config is a candidate, we'll use that.
configuredCipher := config.Cipher()
for _, c := range candidateCiphers {
cipherFunc := packet.CipherFunction(c)
if cipherFunc == configuredCipher {
cipher = cipherFunc
break
}
}
var hash crypto.Hash
for _, hashId := range candidateHashes {
if h, ok := s2k.HashIdToHash(hashId); ok && h.Available() {
hash = h
break
}
}
// If the hash specified by config is a candidate, we'll use that.
if configuredHash := config.Hash(); configuredHash.Available() {
for _, hashId := range candidateHashes {
if h, ok := s2k.HashIdToHash(hashId); ok && h == configuredHash {
hash = h
break
}
}
}
if hash == 0 {
hashId := candidateHashes[0]
name, ok := s2k.HashIdToString(hashId)
if !ok {
name = "#" + strconv.Itoa(int(hashId))
}
return nil, errors.InvalidArgumentError("cannot encrypt because no candidate hash functions are compiled in. (Wanted " + name + " in this case.)")
}
symKey := make([]byte, cipher.KeySize())
if _, err := io.ReadFull(config.Random(), symKey); err != nil {
return nil, err
}
for _, key := range encryptKeys {
if err := packet.SerializeEncryptedKey(ciphertext, key.PublicKey, cipher, symKey, config); err != nil {
return nil, err
}
}
encryptedData, err := packet.SerializeSymmetricallyEncrypted(ciphertext, cipher, symKey, config)
if err != nil {
return
}
if signer != nil {
ops := &packet.OnePassSignature{
SigType: packet.SigTypeBinary,
Hash: hash,
PubKeyAlgo: signer.PubKeyAlgo,
KeyId: signer.KeyId,
IsLast: true,
}
if err := ops.Serialize(encryptedData); err != nil {
return nil, err
}
}
if hints == nil {
hints = &FileHints{}
}
w := encryptedData
if signer != nil {
// If we need to write a signature packet after the literal
// data then we need to stop literalData from closing
// encryptedData.
w = noOpCloser{encryptedData}
}
var epochSeconds uint32
if !hints.ModTime.IsZero() {
epochSeconds = uint32(hints.ModTime.Unix())
}
literalData, err := packet.SerializeLiteral(w, hints.IsBinary, hints.FileName, epochSeconds)
if err != nil {
return nil, err
}
if signer != nil {
return signatureWriter{encryptedData, literalData, hash, hash.New(), signer, config}, nil
}
return literalData, nil
}