Closes #5 and #6

- removed spurious check in decrypt() against blocksize
- added additional tests for small sized blocks and inputs smaller than
  the blocksize.
- updated README to capture dependencies (protobuf tools)

sign/encrypt.go

@@ -260,7 +260,7 @@ func (e *Encryptor) start(wr io.Writer) error {
 }
 
 // encrypt exactly _one_ block of data
-// The nonce for the block is: sha256(salt || chunkLen || block#)
+// The nonce is constructed from the salt, block# and block-size.
 // This protects the output stream from re-ordering attacks and length
 // modification attacks. The encoded length & block number is used as
 // additional data in the AEAD construction.
@@ -473,7 +473,6 @@ func (d *Decryptor) Decrypt(wr io.Writer) error {
 			return nil
 		}
 	}
-	return nil
 }
 
 // Decrypt exactly one chunk of data
@@ -490,7 +489,6 @@ func (d *Decryptor) decrypt(i uint32) ([]byte, bool, error) {
 
 	m := binary.BigEndian.Uint32(b[:4])
 	eof := (m & _EOF) > 0
-
 	m &= (_EOF - 1)
 
 	// Sanity check - in case of corrupt header
@@ -504,9 +502,6 @@ func (d *Decryptor) decrypt(i uint32) ([]byte, bool, error) {
 		}
 		return p, eof, nil
 
-	case m < ovh:
-		return nil, false, fmt.Errorf("decrypt: chunksize is too small (%d)", m)
-
 	default:
 	}
 

sign/encrypt_test.go

@@ -76,6 +76,57 @@ func TestEncryptSimple(t *testing.T) {
 	assert(byteEq(b, buf), "decrypt content mismatch")
 }
 
+// one sender, one receiver - small blocks
+func TestEncryptSmallSizes(t *testing.T) {
+	assert := newAsserter(t)
+
+	receiver, err := NewKeypair()
+	assert(err == nil, "receiver keypair gen failed: %s", err)
+
+	var blkSize int = 8
+	var size int = (blkSize * 4)
+
+	// cleartext
+	bigbuf := make([]byte, size)
+	for i := 0; i < len(bigbuf); i++ {
+		bigbuf[i] = byte(i & 0xff)
+	}
+
+	// encrypt progressively larger bufs
+	for i := 1; i < len(bigbuf); i++ {
+		buf := bigbuf[:i]
+
+		ee, err := NewEncryptor(nil, uint64(blkSize))
+		assert(err == nil, "encryptor-%d create fail: %s", i, err)
+
+		err = ee.AddRecipient(&receiver.Pub)
+		assert(err == nil, "encryptor-%d: can't add recipient: %s", i, err)
+
+		rd := bytes.NewBuffer(buf)
+		wr := Buffer{}
+
+		err = ee.Encrypt(rd, &wr)
+		assert(err == nil, "encrypt-%d fail: %s", i, err)
+
+		rd = bytes.NewBuffer(wr.Bytes())
+
+		dd, err := NewDecryptor(rd)
+		assert(err == nil, "decryptor-%d create fail: %s", i, err)
+
+		err = dd.SetPrivateKey(&receiver.Sec, nil)
+		assert(err == nil, "decryptor-%d can't add SK: %s", i, err)
+
+		wr = Buffer{}
+		err = dd.Decrypt(&wr)
+		assert(err == nil, "decrypt-%d fail: %s", i, err)
+
+		b := wr.Bytes()
+		assert(len(b) == len(buf), "decrypt-%d length mismatch: exp %d, saw %d", i, len(buf), len(b))
+
+		assert(byteEq(b, buf), "decrypt-%d content mismatch", i)
+	}
+}
+
 // test corrupted header or corrupted input
 func TestEncryptCorrupted(t *testing.T) {
 	assert := newAsserter(t)
@@ -313,6 +364,93 @@ func TestStreamIO(t *testing.T) {
 
 }
 
+// Test stream write and read with small sizes
+func TestSmallSizeStreamIO(t *testing.T) {
+	assert := newAsserter(t)
+
+	receiver, err := NewKeypair()
+	assert(err == nil, "receiver keypair gen failed: %s", err)
+
+	var blkSize int = 8
+	var size int = blkSize * 10
+
+	// cleartext
+	bigbuf := make([]byte, size)
+	for i := 0; i < len(bigbuf); i++ {
+		bigbuf[i] = byte(i & 0xff)
+	}
+
+	for i := 1; i < len(bigbuf); i++ {
+		buf := bigbuf[:i]
+		t.Logf("small-size-stream: size %d, chunksize %d\n", i, blkSize)
+
+		ee, err := NewEncryptor(nil, uint64(blkSize))
+		assert(err == nil, "encryptor create fail: %s", err)
+
+		err = ee.AddRecipient(&receiver.Pub)
+		assert(err == nil, "can't add recipient: %s", err)
+
+		wr := Buffer{}
+		wio, err := ee.NewStreamWriter(&wr)
+		assert(err == nil, "can't start stream writer: %s", err)
+
+		// chunksize for writing to stream
+		csize := blkSize - 1
+		rbuf := buf
+		for len(rbuf) > 0 {
+			m := csize
+			if len(rbuf) < m {
+				m = len(rbuf)
+			}
+
+			n, err := wio.Write(rbuf[:m])
+			assert(err == nil, "stream write failed: %s", err)
+			assert(n == m, "stream write mismatch: exp %d, saw %d", m, n)
+
+			rbuf = rbuf[m:]
+		}
+		err = wio.Close()
+		assert(err == nil, "stream close failed: %s", err)
+
+		_, err = wio.Write(buf[:csize])
+		assert(err != nil, "stream write accepted I/O after close: %s", err)
+
+		rd := bytes.NewBuffer(wr.Bytes())
+
+		dd, err := NewDecryptor(rd)
+		assert(err == nil, "decryptor create fail: %s", err)
+
+		err = dd.SetPrivateKey(&receiver.Sec, nil)
+		assert(err == nil, "decryptor can't add SK: %s", err)
+
+		rio, err := dd.NewStreamReader()
+		assert(err == nil, "stream reader failed: %s", err)
+
+		rbuf = make([]byte, csize)
+		wr = Buffer{}
+		n := 0
+		for {
+			m, err := rio.Read(rbuf)
+			assert(err == nil || err == io.EOF, "streamread fail: %s", err)
+
+			if m > 0 {
+				wr.Write(rbuf[:m])
+				n += m
+			}
+			if err == io.EOF || m == 0 {
+				break
+			}
+		}
+
+		b := wr.Bytes()
+		assert(n == len(b), "streamread: bad buflen; exp %d, saw %d", n, len(b))
+		assert(n == len(buf), "streamread: decrypt len mismatch; exp %d, saw %d", len(buf), n)
+
+		assert(byteEq(b, buf), "decrypt content mismatch")
+	}
+
+}
+
 func randint() int {
 	var b [4]byte
 

sign/ssh.go

@@ -57,8 +57,8 @@ func parseSSHPrivateKey(data []byte, getpw func() ([]byte, error)) (*PrivateKey,
 }
 
 func parseSSHPublicKey(in []byte) (*PublicKey, error) {
-	splitter := regexp.MustCompile("[ \\t]+");
-	v := splitter.Split(string(in), -1);
+	splitter := regexp.MustCompile("[ \\t]+")
+	v := splitter.Split(string(in), -1)
 	if len(v) != 3 {
 		return nil, ErrBadPublicKey
 	}

sign/stream.go

@@ -29,6 +29,8 @@ type encWriter struct {
 	err error
 }
 
+var _ io.WriteCloser = &encWriter{}
+
 // NewStreamWriter begins stream encryption to an underlying destination writer 'wr'.
 // It returns an io.WriteCloser.
 func (e *Encryptor) NewStreamWriter(wr io.WriteCloser) (io.WriteCloser, error) {
@@ -108,6 +110,8 @@ type encReader struct {
 	blk    uint32
 }
 
+var _ io.Reader = &encReader{}
+
 // NewStreamReader returns an io.Reader to read from the decrypted stream
 func (d *Decryptor) NewStreamReader() (io.Reader, error) {
 	if d.key == nil {