vendor: update the entire golang.org/x/crypto dependency

vendor/golang.org/x/crypto/openpgp/keys.go

@@ -325,16 +325,14 @@ func ReadEntity(packets *packet.Reader) (*Entity, error) {
 		if e.PrivateKey, ok = p.(*packet.PrivateKey); !ok {
 			packets.Unread(p)
 			return nil, errors.StructuralError("first packet was not a public/private key")
-		} else {
-			e.PrimaryKey = &e.PrivateKey.PublicKey
 		}
+		e.PrimaryKey = &e.PrivateKey.PublicKey
 	}
 
 	if !e.PrimaryKey.PubKeyAlgo.CanSign() {
 		return nil, errors.StructuralError("primary key cannot be used for signatures")
 	}
 
-	var current *Identity
 	var revocations []*packet.Signature
 EachPacket:
 	for {
@@ -347,32 +345,8 @@ EachPacket:
 
 		switch pkt := p.(type) {
 		case *packet.UserId:
-			current = new(Identity)
-			current.Name = pkt.Id
-			current.UserId = pkt
-			e.Identities[pkt.Id] = current
-
-			for {
-				p, err = packets.Next()
-				if err == io.EOF {
-					return nil, io.ErrUnexpectedEOF
-				} else if err != nil {
-					return nil, err
-				}
-
-				sig, ok := p.(*packet.Signature)
-				if !ok {
-					return nil, errors.StructuralError("user ID packet not followed by self-signature")
-				}
-
-				if (sig.SigType == packet.SigTypePositiveCert || sig.SigType == packet.SigTypeGenericCert) && sig.IssuerKeyId != nil && *sig.IssuerKeyId == e.PrimaryKey.KeyId {
-					if err = e.PrimaryKey.VerifyUserIdSignature(pkt.Id, e.PrimaryKey, sig); err != nil {
-						return nil, errors.StructuralError("user ID self-signature invalid: " + err.Error())
-					}
-					current.SelfSignature = sig
-					break
-				}
-				current.Signatures = append(current.Signatures, sig)
+			if err := addUserID(e, packets, pkt); err != nil {
+				return nil, err
 			}
 		case *packet.Signature:
 			if pkt.SigType == packet.SigTypeKeyRevocation {
@@ -381,11 +355,9 @@ EachPacket:
 				// TODO: RFC4880 5.2.1 permits signatures
 				// directly on keys (eg. to bind additional
 				// revocation keys).
-			} else if current == nil {
-				return nil, errors.StructuralError("signature packet found before user id packet")
-			} else {
-				current.Signatures = append(current.Signatures, pkt)
 			}
+			// Else, ignoring the signature as it does not follow anything
+			// we would know to attach it to.
 		case *packet.PrivateKey:
 			if pkt.IsSubkey == false {
 				packets.Unread(p)
@@ -426,33 +398,105 @@ EachPacket:
 	return e, nil
 }
 
+func addUserID(e *Entity, packets *packet.Reader, pkt *packet.UserId) error {
+	// Make a new Identity object, that we might wind up throwing away.
+	// We'll only add it if we get a valid self-signature over this
+	// userID.
+	identity := new(Identity)
+	identity.Name = pkt.Id
+	identity.UserId = pkt
+
+	for {
+		p, err := packets.Next()
+		if err == io.EOF {
+			break
+		} else if err != nil {
+			return err
+		}
+
+		sig, ok := p.(*packet.Signature)
+		if !ok {
+			packets.Unread(p)
+			break
+		}
+
+		if (sig.SigType == packet.SigTypePositiveCert || sig.SigType == packet.SigTypeGenericCert) && sig.IssuerKeyId != nil && *sig.IssuerKeyId == e.PrimaryKey.KeyId {
+			if err = e.PrimaryKey.VerifyUserIdSignature(pkt.Id, e.PrimaryKey, sig); err != nil {
+				return errors.StructuralError("user ID self-signature invalid: " + err.Error())
+			}
+			identity.SelfSignature = sig
+			e.Identities[pkt.Id] = identity
+		} else {
+			identity.Signatures = append(identity.Signatures, sig)
+		}
+	}
+
+	return nil
+}
+
 func addSubkey(e *Entity, packets *packet.Reader, pub *packet.PublicKey, priv *packet.PrivateKey) error {
 	var subKey Subkey
 	subKey.PublicKey = pub
 	subKey.PrivateKey = priv
-	p, err := packets.Next()
-	if err == io.EOF {
-		return io.ErrUnexpectedEOF
+
+	for {
+		p, err := packets.Next()
+		if err == io.EOF {
+			break
+		} else if err != nil {
+			return errors.StructuralError("subkey signature invalid: " + err.Error())
+		}
+
+		sig, ok := p.(*packet.Signature)
+		if !ok {
+			packets.Unread(p)
+			break
+		}
+
+		if sig.SigType != packet.SigTypeSubkeyBinding && sig.SigType != packet.SigTypeSubkeyRevocation {
+			return errors.StructuralError("subkey signature with wrong type")
+		}
+
+		if err := e.PrimaryKey.VerifyKeySignature(subKey.PublicKey, sig); err != nil {
+			return errors.StructuralError("subkey signature invalid: " + err.Error())
+		}
+
+		switch sig.SigType {
+		case packet.SigTypeSubkeyRevocation:
+			subKey.Sig = sig
+		case packet.SigTypeSubkeyBinding:
+
+			if shouldReplaceSubkeySig(subKey.Sig, sig) {
+				subKey.Sig = sig
+			}
+		}
 	}
-	if err != nil {
-		return errors.StructuralError("subkey signature invalid: " + err.Error())
-	}
-	var ok bool
-	subKey.Sig, ok = p.(*packet.Signature)
-	if !ok {
+
+	if subKey.Sig == nil {
 		return errors.StructuralError("subkey packet not followed by signature")
 	}
-	if subKey.Sig.SigType != packet.SigTypeSubkeyBinding && subKey.Sig.SigType != packet.SigTypeSubkeyRevocation {
-		return errors.StructuralError("subkey signature with wrong type")
-	}
-	err = e.PrimaryKey.VerifyKeySignature(subKey.PublicKey, subKey.Sig)
-	if err != nil {
-		return errors.StructuralError("subkey signature invalid: " + err.Error())
-	}
+
 	e.Subkeys = append(e.Subkeys, subKey)
+
 	return nil
 }
 
+func shouldReplaceSubkeySig(existingSig, potentialNewSig *packet.Signature) bool {
+	if potentialNewSig == nil {
+		return false
+	}
+
+	if existingSig == nil {
+		return true
+	}
+
+	if existingSig.SigType == packet.SigTypeSubkeyRevocation {
+		return false // never override a revocation signature
+	}
+
+	return potentialNewSig.CreationTime.After(existingSig.CreationTime)
+}
+
 const defaultRSAKeyBits = 2048
 
 // NewEntity returns an Entity that contains a fresh RSA/RSA keypair with a
@@ -487,7 +531,7 @@ func NewEntity(name, comment, email string, config *packet.Config) (*Entity, err
 	}
 	isPrimaryId := true
 	e.Identities[uid.Id] = &Identity{
-		Name:   uid.Name,
+		Name:   uid.Id,
 		UserId: uid,
 		SelfSignature: &packet.Signature{
 			CreationTime: currentTime,
@@ -501,6 +545,10 @@ func NewEntity(name, comment, email string, config *packet.Config) (*Entity, err
 			IssuerKeyId:  &e.PrimaryKey.KeyId,
 		},
 	}
+	err = e.Identities[uid.Id].SelfSignature.SignUserId(uid.Id, e.PrimaryKey, e.PrivateKey, config)
+	if err != nil {
+		return nil, err
+	}
 
 	// If the user passes in a DefaultHash via packet.Config,
 	// set the PreferredHash for the SelfSignature.
@@ -508,6 +556,11 @@ func NewEntity(name, comment, email string, config *packet.Config) (*Entity, err
 		e.Identities[uid.Id].SelfSignature.PreferredHash = []uint8{hashToHashId(config.DefaultHash)}
 	}
 
+	// Likewise for DefaultCipher.
+	if config != nil && config.DefaultCipher != 0 {
+		e.Identities[uid.Id].SelfSignature.PreferredSymmetric = []uint8{uint8(config.DefaultCipher)}
+	}
+
 	e.Subkeys = make([]Subkey, 1)
 	e.Subkeys[0] = Subkey{
 		PublicKey:  packet.NewRSAPublicKey(currentTime, &encryptingPriv.PublicKey),
@@ -525,13 +578,16 @@ func NewEntity(name, comment, email string, config *packet.Config) (*Entity, err
 	}
 	e.Subkeys[0].PublicKey.IsSubkey = true
 	e.Subkeys[0].PrivateKey.IsSubkey = true
-
+	err = e.Subkeys[0].Sig.SignKey(e.Subkeys[0].PublicKey, e.PrivateKey, config)
+	if err != nil {
+		return nil, err
+	}
 	return e, nil
 }
 
-// SerializePrivate serializes an Entity, including private key material, to
-// the given Writer. For now, it must only be used on an Entity returned from
-// NewEntity.
+// SerializePrivate serializes an Entity, including private key material, but
+// excluding signatures from other entities, to the given Writer.
+// Identities and subkeys are re-signed in case they changed since NewEntry.
 // If config is nil, sensible defaults will be used.
 func (e *Entity) SerializePrivate(w io.Writer, config *packet.Config) (err error) {
 	err = e.PrivateKey.Serialize(w)
@@ -569,8 +625,8 @@ func (e *Entity) SerializePrivate(w io.Writer, config *packet.Config) (err error
 	return nil
 }
 
-// Serialize writes the public part of the given Entity to w. (No private
-// key material will be output).
+// Serialize writes the public part of the given Entity to w, including
+// signatures from other entities. No private key material will be output.
 func (e *Entity) Serialize(w io.Writer) error {
 	err := e.PrimaryKey.Serialize(w)
 	if err != nil {

vendor/golang.org/x/crypto/openpgp/packet/encrypted_key.go

@@ -42,12 +42,18 @@ func (e *EncryptedKey) parse(r io.Reader) (err error) {
 	switch e.Algo {
 	case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly:
 		e.encryptedMPI1.bytes, e.encryptedMPI1.bitLength, err = readMPI(r)
+		if err != nil {
+			return
+		}
 	case PubKeyAlgoElGamal:
 		e.encryptedMPI1.bytes, e.encryptedMPI1.bitLength, err = readMPI(r)
 		if err != nil {
 			return
 		}
 		e.encryptedMPI2.bytes, e.encryptedMPI2.bitLength, err = readMPI(r)
+		if err != nil {
+			return
+		}
 	}
 	_, err = consumeAll(r)
 	return
@@ -72,7 +78,8 @@ func (e *EncryptedKey) Decrypt(priv *PrivateKey, config *Config) error {
 	// padding oracle attacks.
 	switch priv.PubKeyAlgo {
 	case PubKeyAlgoRSA, PubKeyAlgoRSAEncryptOnly:
-		b, err = rsa.DecryptPKCS1v15(config.Random(), priv.PrivateKey.(*rsa.PrivateKey), e.encryptedMPI1.bytes)
+		k := priv.PrivateKey.(*rsa.PrivateKey)
+		b, err = rsa.DecryptPKCS1v15(config.Random(), k, padToKeySize(&k.PublicKey, e.encryptedMPI1.bytes))
 	case PubKeyAlgoElGamal:
 		c1 := new(big.Int).SetBytes(e.encryptedMPI1.bytes)
 		c2 := new(big.Int).SetBytes(e.encryptedMPI2.bytes)

vendor/golang.org/x/crypto/openpgp/packet/packet.go

@@ -11,10 +11,12 @@ import (
 	"crypto/aes"
 	"crypto/cipher"
 	"crypto/des"
-	"golang.org/x/crypto/cast5"
-	"golang.org/x/crypto/openpgp/errors"
+	"crypto/rsa"
 	"io"
 	"math/big"
+
+	"golang.org/x/crypto/cast5"
+	"golang.org/x/crypto/openpgp/errors"
 )
 
 // readFull is the same as io.ReadFull except that reading zero bytes returns
@@ -402,14 +404,16 @@ const (
 type PublicKeyAlgorithm uint8
 
 const (
-	PubKeyAlgoRSA            PublicKeyAlgorithm = 1
-	PubKeyAlgoRSAEncryptOnly PublicKeyAlgorithm = 2
-	PubKeyAlgoRSASignOnly    PublicKeyAlgorithm = 3
-	PubKeyAlgoElGamal        PublicKeyAlgorithm = 16
-	PubKeyAlgoDSA            PublicKeyAlgorithm = 17
+	PubKeyAlgoRSA     PublicKeyAlgorithm = 1
+	PubKeyAlgoElGamal PublicKeyAlgorithm = 16
+	PubKeyAlgoDSA     PublicKeyAlgorithm = 17
 	// RFC 6637, Section 5.
 	PubKeyAlgoECDH  PublicKeyAlgorithm = 18
 	PubKeyAlgoECDSA PublicKeyAlgorithm = 19
+
+	// 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
@@ -500,19 +504,17 @@ func readMPI(r io.Reader) (mpi []byte, bitLength uint16, err error) {
 	numBytes := (int(bitLength) + 7) / 8
 	mpi = make([]byte, numBytes)
 	_, err = readFull(r, mpi)
-	return
-}
-
-// mpiLength returns the length of the given *big.Int when serialized as an
-// MPI.
-func mpiLength(n *big.Int) (mpiLengthInBytes int) {
-	mpiLengthInBytes = 2 /* MPI length */
-	mpiLengthInBytes += (n.BitLen() + 7) / 8
+	// According to RFC 4880 3.2. we should check that the MPI has no leading
+	// zeroes (at least when not an encrypted MPI?), but this implementation
+	// does generate leading zeroes, so we keep accepting them.
 	return
 }
 
 // writeMPI serializes a big integer to w.
 func writeMPI(w io.Writer, bitLength uint16, mpiBytes []byte) (err error) {
+	// Note that we can produce leading zeroes, in violation of RFC 4880 3.2.
+	// Implementations seem to be tolerant of them, and stripping them would
+	// make it complex to guarantee matching re-serialization.
 	_, err = w.Write([]byte{byte(bitLength >> 8), byte(bitLength)})
 	if err == nil {
 		_, err = w.Write(mpiBytes)
@@ -525,6 +527,18 @@ func writeBig(w io.Writer, i *big.Int) error {
 	return writeMPI(w, uint16(i.BitLen()), i.Bytes())
 }
 
+// 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.

vendor/golang.org/x/crypto/openpgp/packet/private_key.go

@@ -64,14 +64,19 @@ func NewECDSAPrivateKey(currentTime time.Time, priv *ecdsa.PrivateKey) *PrivateK
 	return pk
 }
 
-// NewSignerPrivateKey creates a sign-only PrivateKey from a crypto.Signer that
+// NewSignerPrivateKey creates a PrivateKey from a crypto.Signer that
 // implements RSA or ECDSA.
 func NewSignerPrivateKey(currentTime 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(currentTime, pubkey)
 	case rsa.PublicKey:
 		pk.PublicKey = *NewRSAPublicKey(currentTime, &pubkey)
-		pk.PubKeyAlgo = PubKeyAlgoRSASignOnly
+	case *ecdsa.PublicKey:
+		pk.PublicKey = *NewECDSAPublicKey(currentTime, pubkey)
 	case ecdsa.PublicKey:
 		pk.PublicKey = *NewECDSAPublicKey(currentTime, &pubkey)
 	default:

vendor/golang.org/x/crypto/openpgp/packet/public_key.go

@@ -244,7 +244,12 @@ func NewECDSAPublicKey(creationTime time.Time, pub *ecdsa.PublicKey) *PublicKey
 	}
 
 	pk.ec.p.bytes = elliptic.Marshal(pub.Curve, pub.X, pub.Y)
-	pk.ec.p.bitLength = uint16(8 * len(pk.ec.p.bytes))
+
+	// The bit length is 3 (for the 0x04 specifying an uncompressed key)
+	// plus two field elements (for x and y), which are rounded up to the
+	// nearest byte. See https://tools.ietf.org/html/rfc6637#section-6
+	fieldBytes := (pub.Curve.Params().BitSize + 7) & ^7
+	pk.ec.p.bitLength = uint16(3 + fieldBytes + fieldBytes)
 
 	pk.setFingerPrintAndKeyId()
 	return pk
@@ -515,7 +520,7 @@ func (pk *PublicKey) VerifySignature(signed hash.Hash, sig *Signature) (err erro
 	switch pk.PubKeyAlgo {
 	case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly:
 		rsaPublicKey, _ := pk.PublicKey.(*rsa.PublicKey)
-		err = rsa.VerifyPKCS1v15(rsaPublicKey, sig.Hash, hashBytes, sig.RSASignature.bytes)
+		err = rsa.VerifyPKCS1v15(rsaPublicKey, sig.Hash, hashBytes, padToKeySize(rsaPublicKey, sig.RSASignature.bytes))
 		if err != nil {
 			return errors.SignatureError("RSA verification failure")
 		}
@@ -566,7 +571,7 @@ func (pk *PublicKey) VerifySignatureV3(signed hash.Hash, sig *SignatureV3) (err
 	switch pk.PubKeyAlgo {
 	case PubKeyAlgoRSA, PubKeyAlgoRSASignOnly:
 		rsaPublicKey := pk.PublicKey.(*rsa.PublicKey)
-		if err = rsa.VerifyPKCS1v15(rsaPublicKey, sig.Hash, hashBytes, sig.RSASignature.bytes); err != nil {
+		if err = rsa.VerifyPKCS1v15(rsaPublicKey, sig.Hash, hashBytes, padToKeySize(rsaPublicKey, sig.RSASignature.bytes)); err != nil {
 			return errors.SignatureError("RSA verification failure")
 		}
 		return

vendor/golang.org/x/crypto/openpgp/packet/signature.go

@@ -542,7 +542,7 @@ func (sig *Signature) Sign(h hash.Hash, priv *PrivateKey, config *Config) (err e
 			r, s, err = ecdsa.Sign(config.Random(), pk, digest)
 		} else {
 			var b []byte
-			b, err = priv.PrivateKey.(crypto.Signer).Sign(config.Random(), digest, nil)
+			b, err = priv.PrivateKey.(crypto.Signer).Sign(config.Random(), digest, sig.Hash)
 			if err == nil {
 				r, s, err = unwrapECDSASig(b)
 			}

vendor/golang.org/x/crypto/openpgp/packet/userattribute.go

@@ -80,7 +80,7 @@ func (uat *UserAttribute) Serialize(w io.Writer) (err error) {
 
 // ImageData returns zero or more byte slices, each containing
 // JPEG File Interchange Format (JFIF), for each photo in the
-// the user attribute packet.
+// user attribute packet.
 func (uat *UserAttribute) ImageData() (imageData [][]byte) {
 	for _, sp := range uat.Contents {
 		if sp.SubType == UserAttrImageSubpacket && len(sp.Contents) > 16 {

vendor/golang.org/x/crypto/openpgp/write.go

@@ -164,12 +164,12 @@ func hashToHashId(h crypto.Hash) uint8 {
 	return v
 }
 
-// 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) {
+// writeAndSign writes the data as a payload package 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 writeAndSign(payload io.WriteCloser, candidateHashes []uint8, 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())
@@ -185,6 +185,83 @@ func Encrypt(ciphertext io.Writer, to []*Entity, signed *Entity, hints *FileHint
 		}
 	}
 
+	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.)")
+	}
+
+	if signer != nil {
+		ops := &packet.OnePassSignature{
+			SigType:    packet.SigTypeBinary,
+			Hash:       hash,
+			PubKeyAlgo: signer.PubKeyAlgo,
+			KeyId:      signer.KeyId,
+			IsLast:     true,
+		}
+		if err := ops.Serialize(payload); err != nil {
+			return nil, err
+		}
+	}
+
+	if hints == nil {
+		hints = &FileHints{}
+	}
+
+	w := payload
+	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{w}
+
+	}
+	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{payload, literalData, hash, hash.New(), signer, config}, nil
+	}
+	return literalData, nil
+}
+
+// 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) {
+	if len(to) == 0 {
+		return nil, errors.InvalidArgumentError("no encryption recipient provided")
+	}
+
 	// These are the possible ciphers that we'll use for the message.
 	candidateCiphers := []uint8{
 		uint8(packet.CipherAES128),
@@ -194,6 +271,7 @@ func Encrypt(ciphertext io.Writer, to []*Entity, signed *Entity, hints *FileHint
 	// These are the possible hash functions that we'll use for the signature.
 	candidateHashes := []uint8{
 		hashToHashId(crypto.SHA256),
+		hashToHashId(crypto.SHA384),
 		hashToHashId(crypto.SHA512),
 		hashToHashId(crypto.SHA1),
 		hashToHashId(crypto.RIPEMD160),
@@ -241,33 +319,6 @@ func Encrypt(ciphertext io.Writer, to []*Entity, signed *Entity, hints *FileHint
 		}
 	}
 
-	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
@@ -279,49 +330,38 @@ func Encrypt(ciphertext io.Writer, to []*Entity, signed *Entity, hints *FileHint
 		}
 	}
 
-	encryptedData, err := packet.SerializeSymmetricallyEncrypted(ciphertext, cipher, symKey, config)
+	payload, 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
-		}
+	return writeAndSign(payload, candidateHashes, signed, hints, config)
+}
+
+// Sign signs a message. The resulting WriteCloser must be closed after the
+// contents of the file have been written.  hints contains optional information
+// that aids the recipients in processing the message.
+// If config is nil, sensible defaults will be used.
+func Sign(output io.Writer, signed *Entity, hints *FileHints, config *packet.Config) (input io.WriteCloser, err error) {
+	if signed == nil {
+		return nil, errors.InvalidArgumentError("no signer provided")
 	}
 
-	if hints == nil {
-		hints = &FileHints{}
+	// These are the possible hash functions that we'll use for the signature.
+	candidateHashes := []uint8{
+		hashToHashId(crypto.SHA256),
+		hashToHashId(crypto.SHA384),
+		hashToHashId(crypto.SHA512),
+		hashToHashId(crypto.SHA1),
+		hashToHashId(crypto.RIPEMD160),
 	}
-
-	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}
-
+	defaultHashes := candidateHashes[len(candidateHashes)-1:]
+	preferredHashes := signed.primaryIdentity().SelfSignature.PreferredHash
+	if len(preferredHashes) == 0 {
+		preferredHashes = defaultHashes
 	}
-	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
+	candidateHashes = intersectPreferences(candidateHashes, preferredHashes)
+	return writeAndSign(noOpCloser{output}, candidateHashes, signed, hints, config)
 }
 
 // signatureWriter hashes the contents of a message while passing it along to