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openpgp: support creating signatures compatible with 'gpg --sign'.

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This is neither a '--clearsign' nor a '--detach-sign' which are already
supported.  Verification of these signatures is already supported by
ReadMessage.

The code shares a lot with standard encrypt/sign, so mostly a
refactoring of 'Encrypt' to allow use of the code path without
actually doing a signing.

Change-Id: I5bb7487134ffcf1189ed74e28dbbbe1c01b356d1
GitHub-Last-Rev: 01162222600a4a2a230a444387b33883faf596ec
GitHub-Pull-Request: golang/crypto#50
Reviewed-on: https://go-review.googlesource.com/116017
Reviewed-by: Filippo Valsorda <filippo@golang.org>
This commit is contained in:
Wilfried Teiken
2018-07-18 16:05:20 +00:00
committed by Filippo Valsorda
parent a49355c7e3
commit a214413485
2 changed files with 195 additions and 68 deletions
Download Patch File Download Diff File Expand all files Collapse all files
openpgp/write.go
+106 -68
View File
@@ -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),
@@ -241,33 +318,6 @@ 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 +329,37 @@ 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.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
openpgp/write_test.go
+89
View File
@@ -271,3 +271,92 @@ func TestEncryption(t *testing.T) {
}
}
}
var testSigningTests = []struct {
keyRingHex string
}{
{
testKeys1And2PrivateHex,
},
{
dsaElGamalTestKeysHex,
},
}
func TestSigning(t *testing.T) {
for i, test := range testSigningTests {
kring, _ := ReadKeyRing(readerFromHex(test.keyRingHex))
passphrase := []byte("passphrase")
for _, entity := range kring {
if entity.PrivateKey != nil && entity.PrivateKey.Encrypted {
err := entity.PrivateKey.Decrypt(passphrase)
if err != nil {
t.Errorf("#%d: failed to decrypt key", i)
}
}
for _, subkey := range entity.Subkeys {
if subkey.PrivateKey != nil && subkey.PrivateKey.Encrypted {
err := subkey.PrivateKey.Decrypt(passphrase)
if err != nil {
t.Errorf("#%d: failed to decrypt subkey", i)
}
}
}
}
signed := kring[0]
buf := new(bytes.Buffer)
w, err := Sign(buf, signed, nil /* no hints */, nil)
if err != nil {
t.Errorf("#%d: error in Sign: %s", i, err)
continue
}
const message = "testing"
_, err = w.Write([]byte(message))
if err != nil {
t.Errorf("#%d: error writing plaintext: %s", i, err)
continue
}
err = w.Close()
if err != nil {
t.Errorf("#%d: error closing WriteCloser: %s", i, err)
continue
}
md, err := ReadMessage(buf, kring, nil /* no prompt */, nil)
if err != nil {
t.Errorf("#%d: error reading message: %s", i, err)
continue
}
testTime, _ := time.Parse("2006-01-02", "2013-07-01")
signKey, _ := kring[0].signingKey(testTime)
expectedKeyId := signKey.PublicKey.KeyId
if md.SignedByKeyId != expectedKeyId {
t.Errorf("#%d: message signed by wrong key id, got: %v, want: %v", i, *md.SignedBy, expectedKeyId)
}
if md.SignedBy == nil {
t.Errorf("#%d: failed to find the signing Entity", i)
}
plaintext, err := ioutil.ReadAll(md.UnverifiedBody)
if err != nil {
t.Errorf("#%d: error reading contents: %v", i, err)
continue
}
if string(plaintext) != message {
t.Errorf("#%d: got: %q, want: %q", i, plaintext, message)
}
if md.SignatureError != nil {
t.Errorf("#%d: signature error: %q", i, md.SignatureError)
}
if md.Signature == nil {
t.Error("signature missing")
}
}
}