ssh: rename methods in packetCipher interface

The new name readCipherPacket/writeCipherPacket disambiguates method
calls from packetConn.{read,write}Packet, which has a different
signature, and is called in different layers of the stack.

Change-Id: I02ca83e28f74f0a347a1cde665efdfb78f3f51bb
Reviewed-on: https://go-review.googlesource.com/c/crypto/+/171657
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

ssh/cipher.go

@@ -149,8 +149,8 @@ type streamPacketCipher struct {
 	macResult   []byte
 }
 
-// readPacket reads and decrypt a single packet from the reader argument.
-func (s *streamPacketCipher) readPacket(seqNum uint32, r io.Reader) ([]byte, error) {
+// readCipherPacket reads and decrypt a single packet from the reader argument.
+func (s *streamPacketCipher) readCipherPacket(seqNum uint32, r io.Reader) ([]byte, error) {
 	if _, err := io.ReadFull(r, s.prefix[:]); err != nil {
 		return nil, err
 	}
@@ -221,8 +221,8 @@ func (s *streamPacketCipher) readPacket(seqNum uint32, r io.Reader) ([]byte, err
 	return s.packetData[:length-paddingLength-1], nil
 }
 
-// writePacket encrypts and sends a packet of data to the writer argument
-func (s *streamPacketCipher) writePacket(seqNum uint32, w io.Writer, rand io.Reader, packet []byte) error {
+// writeCipherPacket encrypts and sends a packet of data to the writer argument
+func (s *streamPacketCipher) writeCipherPacket(seqNum uint32, w io.Writer, rand io.Reader, packet []byte) error {
 	if len(packet) > maxPacket {
 		return errors.New("ssh: packet too large")
 	}
@@ -327,7 +327,7 @@ func newGCMCipher(key, iv, unusedMacKey []byte, unusedAlgs directionAlgorithms)
 
 const gcmTagSize = 16
 
-func (c *gcmCipher) writePacket(seqNum uint32, w io.Writer, rand io.Reader, packet []byte) error {
+func (c *gcmCipher) writeCipherPacket(seqNum uint32, w io.Writer, rand io.Reader, packet []byte) error {
 	// Pad out to multiple of 16 bytes. This is different from the
 	// stream cipher because that encrypts the length too.
 	padding := byte(packetSizeMultiple - (1+len(packet))%packetSizeMultiple)
@@ -370,7 +370,7 @@ func (c *gcmCipher) incIV() {
 	}
 }
 
-func (c *gcmCipher) readPacket(seqNum uint32, r io.Reader) ([]byte, error) {
+func (c *gcmCipher) readCipherPacket(seqNum uint32, r io.Reader) ([]byte, error) {
 	if _, err := io.ReadFull(r, c.prefix[:]); err != nil {
 		return nil, err
 	}
@@ -486,8 +486,8 @@ type cbcError string
 
 func (e cbcError) Error() string { return string(e) }
 
-func (c *cbcCipher) readPacket(seqNum uint32, r io.Reader) ([]byte, error) {
-	p, err := c.readPacketLeaky(seqNum, r)
+func (c *cbcCipher) readCipherPacket(seqNum uint32, r io.Reader) ([]byte, error) {
+	p, err := c.readCipherPacketLeaky(seqNum, r)
 	if err != nil {
 		if _, ok := err.(cbcError); ok {
 			// Verification error: read a fixed amount of
@@ -500,7 +500,7 @@ func (c *cbcCipher) readPacket(seqNum uint32, r io.Reader) ([]byte, error) {
 	return p, err
 }
 
-func (c *cbcCipher) readPacketLeaky(seqNum uint32, r io.Reader) ([]byte, error) {
+func (c *cbcCipher) readCipherPacketLeaky(seqNum uint32, r io.Reader) ([]byte, error) {
 	blockSize := c.decrypter.BlockSize()
 
 	// Read the header, which will include some of the subsequent data in the
@@ -576,7 +576,7 @@ func (c *cbcCipher) readPacketLeaky(seqNum uint32, r io.Reader) ([]byte, error)
 	return c.packetData[prefixLen:paddingStart], nil
 }
 
-func (c *cbcCipher) writePacket(seqNum uint32, w io.Writer, rand io.Reader, packet []byte) error {
+func (c *cbcCipher) writeCipherPacket(seqNum uint32, w io.Writer, rand io.Reader, packet []byte) error {
 	effectiveBlockSize := maxUInt32(cbcMinPacketSizeMultiple, c.encrypter.BlockSize())
 
 	// Length of encrypted portion of the packet (header, payload, padding).
@@ -665,7 +665,7 @@ func newChaCha20Cipher(key, unusedIV, unusedMACKey []byte, unusedAlgs directionA
 	return c, nil
 }
 
-func (c *chacha20Poly1305Cipher) readPacket(seqNum uint32, r io.Reader) ([]byte, error) {
+func (c *chacha20Poly1305Cipher) readCipherPacket(seqNum uint32, r io.Reader) ([]byte, error) {
 	nonce := [3]uint32{0, 0, bits.ReverseBytes32(seqNum)}
 	s := chacha20.New(c.contentKey, nonce)
 	var polyKey [32]byte
@@ -723,7 +723,7 @@ func (c *chacha20Poly1305Cipher) readPacket(seqNum uint32, r io.Reader) ([]byte,
 	return plain, nil
 }
 
-func (c *chacha20Poly1305Cipher) writePacket(seqNum uint32, w io.Writer, rand io.Reader, payload []byte) error {
+func (c *chacha20Poly1305Cipher) writeCipherPacket(seqNum uint32, w io.Writer, rand io.Reader, payload []byte) error {
 	nonce := [3]uint32{0, 0, bits.ReverseBytes32(seqNum)}
 	s := chacha20.New(c.contentKey, nonce)
 	var polyKey [32]byte

ssh/cipher_test.go

@@ -56,13 +56,13 @@ func testPacketCipher(t *testing.T, cipher, mac string) {
 	want := "bla bla"
 	input := []byte(want)
 	buf := &bytes.Buffer{}
-	if err := client.writePacket(0, buf, rand.Reader, input); err != nil {
-		t.Fatalf("writePacket(%q, %q): %v", cipher, mac, err)
+	if err := client.writeCipherPacket(0, buf, rand.Reader, input); err != nil {
+		t.Fatalf("writeCipherPacket(%q, %q): %v", cipher, mac, err)
 	}
 
-	packet, err := server.readPacket(0, buf)
+	packet, err := server.readCipherPacket(0, buf)
 	if err != nil {
-		t.Fatalf("readPacket(%q, %q): %v", cipher, mac, err)
+		t.Fatalf("readCipherPacket(%q, %q): %v", cipher, mac, err)
 	}
 
 	if string(packet) != want {
@@ -85,8 +85,8 @@ func TestCBCOracleCounterMeasure(t *testing.T) {
 	want := "bla bla"
 	input := []byte(want)
 	buf := &bytes.Buffer{}
-	if err := client.writePacket(0, buf, rand.Reader, input); err != nil {
-		t.Errorf("writePacket: %v", err)
+	if err := client.writeCipherPacket(0, buf, rand.Reader, input); err != nil {
+		t.Errorf("writeCipherPacket: %v", err)
 	}
 
 	packetSize := buf.Len()
@@ -106,9 +106,9 @@ func TestCBCOracleCounterMeasure(t *testing.T) {
 		fresh.Bytes()[i] ^= 0x01
 
 		before := fresh.Len()
-		_, err = server.readPacket(0, fresh)
+		_, err = server.readCipherPacket(0, fresh)
 		if err == nil {
-			t.Errorf("corrupt byte %d: readPacket succeeded ", i)
+			t.Errorf("corrupt byte %d: readCipherPacket succeeded ", i)
 			continue
 		}
 		if _, ok := err.(cbcError); !ok {

ssh/transport.go

@@ -53,14 +53,14 @@ type transport struct {
 // packetCipher represents a combination of SSH encryption/MAC
 // protocol.  A single instance should be used for one direction only.
 type packetCipher interface {
-	// writePacket encrypts the packet and writes it to w. The
+	// writeCipherPacket encrypts the packet and writes it to w. The
 	// contents of the packet are generally scrambled.
-	writePacket(seqnum uint32, w io.Writer, rand io.Reader, packet []byte) error
+	writeCipherPacket(seqnum uint32, w io.Writer, rand io.Reader, packet []byte) error
 
-	// readPacket reads and decrypts a packet of data. The
+	// readCipherPacket reads and decrypts a packet of data. The
 	// returned packet may be overwritten by future calls of
 	// readPacket.
-	readPacket(seqnum uint32, r io.Reader) ([]byte, error)
+	readCipherPacket(seqnum uint32, r io.Reader) ([]byte, error)
 }
 
 // connectionState represents one side (read or write) of the
@@ -127,7 +127,7 @@ func (t *transport) readPacket() (p []byte, err error) {
 }
 
 func (s *connectionState) readPacket(r *bufio.Reader) ([]byte, error) {
-	packet, err := s.packetCipher.readPacket(s.seqNum, r)
+	packet, err := s.packetCipher.readCipherPacket(s.seqNum, r)
 	s.seqNum++
 	if err == nil && len(packet) == 0 {
 		err = errors.New("ssh: zero length packet")
@@ -175,7 +175,7 @@ func (t *transport) writePacket(packet []byte) error {
 func (s *connectionState) writePacket(w *bufio.Writer, rand io.Reader, packet []byte) error {
 	changeKeys := len(packet) > 0 && packet[0] == msgNewKeys
 
-	err := s.packetCipher.writePacket(s.seqNum, w, rand, packet)
+	err := s.packetCipher.writeCipherPacket(s.seqNum, w, rand, packet)
 	if err != nil {
 		return err
 	}