From a2144134853fc9a27a7b1e3eb4f19f1a76df13c9 Mon Sep 17 00:00:00 2001 From: Wilfried Teiken Date: Wed, 18 Jul 2018 05:57:37 +0000 Subject: [PATCH] openpgp: support creating signatures compatible with 'gpg --sign'. 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 --- openpgp/write.go | 174 +++++++++++++++++++++++++----------------- openpgp/write_test.go | 89 +++++++++++++++++++++ 2 files changed, 195 insertions(+), 68 deletions(-) diff --git a/openpgp/write.go b/openpgp/write.go index 65a304c..d6dede7 100644 --- a/openpgp/write.go +++ b/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), @@ -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 diff --git a/openpgp/write_test.go b/openpgp/write_test.go index f2d50a0..cbc8f4d 100644 --- a/openpgp/write_test.go +++ b/openpgp/write_test.go @@ -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") + } + } +}