7 files changed, 374 insertions, 9 deletions

diff --git a/src/pkg/crypto/openpgp/packet/literal.go b/src/pkg/crypto/openpgp/packet/literal.go
index 04f50e53e..9411572d7 100644
--- a/src/pkg/crypto/openpgp/packet/literal.go
+++ b/src/pkg/crypto/openpgp/packet/literal.go
@@ -51,3 +51,40 @@ func (l *LiteralData) parse(r io.Reader) (err os.Error) {
 	l.Body = r
 	return
 }
+
+// SerializeLiteral serializes a literal data packet to w and returns a
+// WriteCloser to which the data itself can be written and which MUST be closed
+// on completion. The fileName is truncated to 255 bytes.
+func SerializeLiteral(w io.WriteCloser, isBinary bool, fileName string, time uint32) (plaintext io.WriteCloser, err os.Error) {
+	var buf [4]byte
+	buf[0] = 't'
+	if isBinary {
+		buf[0] = 'b'
+	}
+	if len(fileName) > 255 {
+		fileName = fileName[:255]
+	}
+	buf[1] = byte(len(fileName))
+
+	inner, err := serializeStreamHeader(w, packetTypeLiteralData)
+	if err != nil {
+		return
+	}
+
+	_, err = inner.Write(buf[:2])
+	if err != nil {
+		return
+	}
+	_, err = inner.Write([]byte(fileName))
+	if err != nil {
+		return
+	}
+	binary.BigEndian.PutUint32(buf[:], time)
+	_, err = inner.Write(buf[:])
+	if err != nil {
+		return
+	}
+
+	plaintext = inner
+	return
+}
diff --git a/src/pkg/crypto/openpgp/packet/packet.go b/src/pkg/crypto/openpgp/packet/packet.go
index e583670fb..640a5b76f 100644
--- a/src/pkg/crypto/openpgp/packet/packet.go
+++ b/src/pkg/crypto/openpgp/packet/packet.go
@@ -92,6 +92,46 @@ func (r *partialLengthReader) Read(p []byte) (n int, err os.Error) {
 	return
 }
 
+// partialLengthWriter writes a stream of data using OpenPGP partial lengths.
+// See RFC 4880, section 4.2.2.4.
+type partialLengthWriter struct {
+	w          io.WriteCloser
+	lengthByte [1]byte
+}
+
+func (w *partialLengthWriter) Write(p []byte) (n int, err os.Error) {
+	for len(p) > 0 {
+		for power := uint(14); power < 32; power-- {
+			l := 1 << power
+			if len(p) >= l {
+				w.lengthByte[0] = 224 + uint8(power)
+				_, err = w.w.Write(w.lengthByte[:])
+				if err != nil {
+					return
+				}
+				var m int
+				m, err = w.w.Write(p[:l])
+				n += m
+				if err != nil {
+					return
+				}
+				p = p[l:]
+				break
+			}
+		}
+	}
+	return
+}
+
+func (w *partialLengthWriter) Close() os.Error {
+	w.lengthByte[0] = 0
+	_, err := w.w.Write(w.lengthByte[:])
+	if err != nil {
+		return err
+	}
+	return w.w.Close()
+}
+
 // A spanReader is an io.LimitReader, but it returns ErrUnexpectedEOF if the
 // underlying Reader returns EOF before the limit has been reached.
 type spanReader struct {
@@ -195,6 +235,20 @@ func serializeHeader(w io.Writer, ptype packetType, length int) (err os.Error) {
 	return
 }
 
+// serializeStreamHeader writes an OpenPGP packet header to w where the
+// length of the packet is unknown. It returns a io.WriteCloser which can be
+// used to write the contents of the packet. See RFC 4880, section 4.2.
+func serializeStreamHeader(w io.WriteCloser, ptype packetType) (out io.WriteCloser, err os.Error) {
+	var buf [1]byte
+	buf[0] = 0x80 | 0x40 | byte(ptype)
+	_, err = w.Write(buf[:])
+	if err != nil {
+		return
+	}
+	out = &partialLengthWriter{w: w}
+	return
+}
+
 // Packet represents an OpenPGP packet. Users are expected to try casting
 // instances of this interface to specific packet types.
 type Packet interface {
@@ -327,10 +381,10 @@ const (
 type CipherFunction uint8
 
 const (
-	CipherCAST5  = 3
-	CipherAES128 = 7
-	CipherAES192 = 8
-	CipherAES256 = 9
+	CipherCAST5  CipherFunction = 3
+	CipherAES128 CipherFunction = 7
+	CipherAES192 CipherFunction = 8
+	CipherAES256 CipherFunction = 9
 )
 
 // keySize returns the key size, in bytes, of cipher.
diff --git a/src/pkg/crypto/openpgp/packet/packet_test.go b/src/pkg/crypto/openpgp/packet/packet_test.go
index 1a4692cd4..23d9978ae 100644
--- a/src/pkg/crypto/openpgp/packet/packet_test.go
+++ b/src/pkg/crypto/openpgp/packet/packet_test.go
@@ -210,3 +210,47 @@ func TestSerializeHeader(t *testing.T) {
 		}
 	}
 }
+
+func TestPartialLengths(t *testing.T) {
+	buf := bytes.NewBuffer(nil)
+	w := new(partialLengthWriter)
+	w.w = noOpCloser{buf}
+
+	const maxChunkSize = 64
+
+	var b [maxChunkSize]byte
+	var n uint8
+	for l := 1; l <= maxChunkSize; l++ {
+		for i := 0; i < l; i++ {
+			b[i] = n
+			n++
+		}
+		m, err := w.Write(b[:l])
+		if m != l {
+			t.Errorf("short write got: %d want: %d", m, l)
+		}
+		if err != nil {
+			t.Errorf("error from write: %s", err)
+		}
+	}
+	w.Close()
+
+	want := (maxChunkSize * (maxChunkSize + 1)) / 2
+	copyBuf := bytes.NewBuffer(nil)
+	r := &partialLengthReader{buf, 0, true}
+	m, err := io.Copy(copyBuf, r)
+	if m != int64(want) {
+		t.Errorf("short copy got: %d want: %d", m, want)
+	}
+	if err != nil {
+		t.Errorf("error from copy: %s", err)
+	}
+
+	copyBytes := copyBuf.Bytes()
+	for i := 0; i < want; i++ {
+		if copyBytes[i] != uint8(i) {
+			t.Errorf("bad pattern in copy at %d", i)
+			break
+		}
+	}
+}
diff --git a/src/pkg/crypto/openpgp/packet/symmetric_key_encrypted.go b/src/pkg/crypto/openpgp/packet/symmetric_key_encrypted.go
index d9010f88a..25d264acf 100644
--- a/src/pkg/crypto/openpgp/packet/symmetric_key_encrypted.go
+++ b/src/pkg/crypto/openpgp/packet/symmetric_key_encrypted.go
@@ -5,6 +5,7 @@
 package packet
 
 import (
+	"bytes"
 	"crypto/cipher"
 	"crypto/openpgp/error"
 	"crypto/openpgp/s2k"
@@ -27,6 +28,8 @@ type SymmetricKeyEncrypted struct {
 	encryptedKey []byte
 }
 
+const symmetricKeyEncryptedVersion = 4
+
 func (ske *SymmetricKeyEncrypted) parse(r io.Reader) (err os.Error) {
 	// RFC 4880, section 5.3.
 	var buf [2]byte
@@ -34,7 +37,7 @@ func (ske *SymmetricKeyEncrypted) parse(r io.Reader) (err os.Error) {
 	if err != nil {
 		return
 	}
-	if buf[0] != 4 {
+	if buf[0] != symmetricKeyEncryptedVersion {
 		return error.UnsupportedError("SymmetricKeyEncrypted version")
 	}
 	ske.CipherFunc = CipherFunction(buf[1])
@@ -100,3 +103,60 @@ func (ske *SymmetricKeyEncrypted) Decrypt(passphrase []byte) os.Error {
 	ske.Encrypted = false
 	return nil
 }
+
+// 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
+}
diff --git a/src/pkg/crypto/openpgp/packet/symmetric_key_encrypted_test.go b/src/pkg/crypto/openpgp/packet/symmetric_key_encrypted_test.go
index 717c8ffa6..823ec400d 100644
--- a/src/pkg/crypto/openpgp/packet/symmetric_key_encrypted_test.go
+++ b/src/pkg/crypto/openpgp/packet/symmetric_key_encrypted_test.go
@@ -6,6 +6,7 @@ package packet
 
 import (
 	"bytes"
+	"crypto/rand"
 	"encoding/hex"
 	"io/ioutil"
 	"os"
@@ -60,3 +61,41 @@ func TestSymmetricKeyEncrypted(t *testing.T) {
 
 const symmetricallyEncryptedHex = "8c0d04030302371a0b38d884f02060c91cf97c9973b8e58e028e9501708ccfe618fb92afef7fa2d80ddadd93cf"
 const symmetricallyEncryptedContentsHex = "cb1062004d14c4df636f6e74656e74732e0a"
+
+func TestSerializeSymmetricKeyEncrypted(t *testing.T) {
+	buf := bytes.NewBuffer(nil)
+	passphrase := []byte("testing")
+	cipherFunc := CipherAES128
+
+	key, err := SerializeSymmetricKeyEncrypted(buf, rand.Reader, passphrase, cipherFunc)
+	if err != nil {
+		t.Errorf("failed to serialize: %s", err)
+		return
+	}
+
+	p, err := Read(buf)
+	if err != nil {
+		t.Errorf("failed to reparse: %s", err)
+		return
+	}
+	ske, ok := p.(*SymmetricKeyEncrypted)
+	if !ok {
+		t.Errorf("parsed a different packet type: %#v", p)
+		return
+	}
+
+	if !ske.Encrypted {
+		t.Errorf("SKE not encrypted but should be")
+	}
+	if ske.CipherFunc != cipherFunc {
+		t.Errorf("SKE cipher function is %d (expected %d)", ske.CipherFunc, cipherFunc)
+	}
+	err = ske.Decrypt(passphrase)
+	if err != nil {
+		t.Errorf("failed to decrypt reparsed SKE: %s", err)
+		return
+	}
+	if !bytes.Equal(key, ske.Key) {
+		t.Errorf("keys don't match after Decrpyt: %x (original) vs %x (parsed)", key, ske.Key)
+	}
+}
diff --git a/src/pkg/crypto/openpgp/packet/symmetrically_encrypted.go b/src/pkg/crypto/openpgp/packet/symmetrically_encrypted.go
index fc19ffe80..236c36774 100644
--- a/src/pkg/crypto/openpgp/packet/symmetrically_encrypted.go
+++ b/src/pkg/crypto/openpgp/packet/symmetrically_encrypted.go
@@ -7,6 +7,7 @@ package packet
 import (
 	"crypto/cipher"
 	"crypto/openpgp/error"
+	"crypto/rand"
 	"crypto/sha1"
 	"crypto/subtle"
 	"hash"
@@ -24,6 +25,8 @@ type SymmetricallyEncrypted struct {
 	prefix   []byte
 }
 
+const symmetricallyEncryptedVersion = 1
+
 func (se *SymmetricallyEncrypted) parse(r io.Reader) os.Error {
 	if se.MDC {
 		// See RFC 4880, section 5.13.
@@ -32,7 +35,7 @@ func (se *SymmetricallyEncrypted) parse(r io.Reader) os.Error {
 		if err != nil {
 			return err
 		}
-		if buf[0] != 1 {
+		if buf[0] != symmetricallyEncryptedVersion {
 			return error.UnsupportedError("unknown SymmetricallyEncrypted version")
 		}
 	}
@@ -174,6 +177,9 @@ func (ser *seMDCReader) Read(buf []byte) (n int, err os.Error) {
 	return
 }
 
+// This is a new-format packet tag byte for a type 19 (MDC) packet.
+const mdcPacketTagByte = byte(0x80) | 0x40 | 19
+
 func (ser *seMDCReader) Close() os.Error {
 	if ser.error {
 		return error.SignatureError("error during reading")
@@ -191,16 +197,95 @@ func (ser *seMDCReader) Close() os.Error {
 		}
 	}
 
-	// This is a new-format packet tag byte for a type 19 (MDC) packet.
-	const mdcPacketTagByte = byte(0x80) | 0x40 | 19
 	if ser.trailer[0] != mdcPacketTagByte || ser.trailer[1] != sha1.Size {
 		return error.SignatureError("MDC packet not found")
 	}
 	ser.h.Write(ser.trailer[:2])
 
 	final := ser.h.Sum()
-	if subtle.ConstantTimeCompare(final, ser.trailer[2:]) == 1 {
+	if subtle.ConstantTimeCompare(final, ser.trailer[2:]) != 1 {
 		return error.SignatureError("hash mismatch")
 	}
 	return nil
 }
+
+// An seMDCWriter writes through to an io.WriteCloser while maintains a running
+// hash of the data written. On close, it emits an MDC packet containing the
+// running hash.
+type seMDCWriter struct {
+	w io.WriteCloser
+	h hash.Hash
+}
+
+func (w *seMDCWriter) Write(buf []byte) (n int, err os.Error) {
+	w.h.Write(buf)
+	return w.w.Write(buf)
+}
+
+func (w *seMDCWriter) Close() (err os.Error) {
+	var buf [mdcTrailerSize]byte
+
+	buf[0] = mdcPacketTagByte
+	buf[1] = sha1.Size
+	w.h.Write(buf[:2])
+	digest := w.h.Sum()
+	copy(buf[2:], digest)
+
+	_, err = w.w.Write(buf[:])
+	if err != nil {
+		return
+	}
+	return w.w.Close()
+}
+
+// noOpCloser is like an ioutil.NopCloser, but for an io.Writer.
+type noOpCloser struct {
+	w io.Writer
+}
+
+func (c noOpCloser) Write(data []byte) (n int, err os.Error) {
+	return c.w.Write(data)
+}
+
+func (c noOpCloser) Close() os.Error {
+	return nil
+}
+
+// SerializeSymmetricallyEncrypted serializes a symmetrically encrypted packet
+// to w and returns a WriteCloser to which the to-be-encrypted packets can be
+// written.
+func SerializeSymmetricallyEncrypted(w io.Writer, c CipherFunction, key []byte) (contents io.WriteCloser, err os.Error) {
+	if c.keySize() != len(key) {
+		return nil, error.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 = rand.Reader.Read(iv)
+	if err != nil {
+		return
+	}
+	s, prefix := cipher.NewOCFBEncrypter(block, iv, cipher.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
+}
diff --git a/src/pkg/crypto/openpgp/packet/symmetrically_encrypted_test.go b/src/pkg/crypto/openpgp/packet/symmetrically_encrypted_test.go
index 5543b2029..ba5606e6c 100644
--- a/src/pkg/crypto/openpgp/packet/symmetrically_encrypted_test.go
+++ b/src/pkg/crypto/openpgp/packet/symmetrically_encrypted_test.go
@@ -9,6 +9,7 @@ import (
 	"crypto/openpgp/error"
 	"crypto/sha1"
 	"encoding/hex"
+	"io"
 	"io/ioutil"
 	"os"
 	"testing"
@@ -76,3 +77,48 @@ func testMDCReader(t *testing.T) {
 }
 
 const mdcPlaintextHex = "a302789c3b2d93c4e0eb9aba22283539b3203335af44a134afb800c849cb4c4de10200aff40b45d31432c80cb384299a0655966d6939dfdeed1dddf980"
+
+func TestSerialize(t *testing.T) {
+	buf := bytes.NewBuffer(nil)
+	c := CipherAES128
+	key := make([]byte, c.keySize())
+
+	w, err := SerializeSymmetricallyEncrypted(buf, c, key)
+	if err != nil {
+		t.Errorf("error from SerializeSymmetricallyEncrypted: %s", err)
+		return
+	}
+
+	contents := []byte("hello world\n")
+
+	w.Write(contents)
+	w.Close()
+
+	p, err := Read(buf)
+	if err != nil {
+		t.Errorf("error from Read: %s", err)
+		return
+	}
+
+	se, ok := p.(*SymmetricallyEncrypted)
+	if !ok {
+		t.Errorf("didn't read a *SymmetricallyEncrypted")
+		return
+	}
+
+	r, err := se.Decrypt(c, key)
+	if err != nil {
+		t.Errorf("error from Decrypt: %s", err)
+		return
+	}
+
+	contentsCopy := bytes.NewBuffer(nil)
+	_, err = io.Copy(contentsCopy, r)
+	if err != nil {
+		t.Errorf("error from io.Copy: %s", err)
+		return
+	}
+	if !bytes.Equal(contentsCopy.Bytes(), contents) {
+		t.Errorf("contents not equal got: %x want: %x", contentsCopy.Bytes(), contents)
+	}
+}