Add blockcipherrwc

wrappers/blockcipherrwc.go

@@ -0,0 +1,84 @@
+package wrappers
+
+import (
+	"bytes"
+	"crypto/aes"
+	"crypto/cipher"
+	"io"
+
+	"github.com/juju/errors"
+)
+
+type BlockCipherReadWriteCloser struct {
+	buf *bytes.Buffer
+
+	conn      io.ReadWriteCloser
+	encryptor cipher.BlockMode
+	decryptor cipher.BlockMode
+}
+
+func (c *BlockCipherReadWriteCloser) Read(p []byte) (int, error) {
+	if c.buf.Len() > 0 {
+		return c.flush(p)
+	}
+
+	for c.buf.Len() == 0 || c.buf.Len()%aes.BlockSize != 0 {
+		n, err := c.conn.Read(p)
+		if err != nil {
+			return 0, errors.Annotate(err, "Cannot read from socket")
+		}
+		c.buf.Write(p[:n])
+	}
+
+	return c.flush(p)
+}
+
+func (c *BlockCipherReadWriteCloser) Write(p []byte) (int, error) {
+	if len(p)%aes.BlockSize > 0 {
+		return 0, errors.Errorf("Incorrect block size %d", len(p))
+	}
+
+	buf := getBuffer()
+	defer putBuffer(buf)
+	buf.Grow(len(p))
+	buf.Write(p)
+
+	encrypted := buf.Bytes()
+	c.encryptor.CryptBlocks(encrypted, p)
+
+	return c.conn.Write(encrypted)
+}
+
+func (c *BlockCipherReadWriteCloser) Close() error {
+	defer putBuffer(c.buf)
+	return c.conn.Close()
+}
+
+func (c *BlockCipherReadWriteCloser) flush(p []byte) (int, error) {
+	sizeToRead := len(p)
+	if c.buf.Len() < sizeToRead {
+		sizeToRead = c.buf.Len()
+	}
+	sizeToRead = aes.BlockSize * (sizeToRead / aes.BlockSize)
+
+	c.decryptor.CryptBlocks(p, c.buf.Bytes()[:sizeToRead])
+	if sizeToRead == c.buf.Len() {
+		c.buf.Reset()
+	} else {
+		leftover := c.buf.Bytes()[sizeToRead:]
+		putBuffer(c.buf)
+		c.buf = getBuffer()
+		c.buf.Write(leftover)
+	}
+
+	return sizeToRead, nil
+}
+
+func NewBlockCipherRWC(conn io.ReadWriteCloser, encryptor, decryptor cipher.BlockMode) io.ReadWriteCloser {
+	return &BlockCipherReadWriteCloser{
+		buf:       getBuffer(),
+		conn:      conn,
+		encryptor: encryptor,
+		decryptor: decryptor,
+	}
+}