1 files changed, 112 insertions, 0 deletions
diff --git a/libgo/go/crypto/cipher/ocfb.go b/libgo/go/crypto/cipher/ocfb.go
new file mode 100644
index 000000000..43cb5a531
--- /dev/null
+++ b/libgo/go/crypto/cipher/ocfb.go
@@ -0,0 +1,112 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// OpenPGP CFB Mode. http://tools.ietf.org/html/rfc4880#section-13.9
+
+package cipher
+
+type ocfbEncrypter struct {
+	b       Block
+	fre     []byte
+	outUsed int
+}
+
+// NewOCFBEncrypter returns a Stream which encrypts data with OpenPGP's cipher
+// feedback mode using the given Block, and an initial amount of ciphertext.
+// randData must be random bytes and be the same length as the Block's block
+// size.
+func NewOCFBEncrypter(block Block, randData []byte) (Stream, []byte) {
+	blockSize := block.BlockSize()
+	if len(randData) != blockSize {
+		return nil, nil
+	}
+
+	x := &ocfbEncrypter{
+		b:       block,
+		fre:     make([]byte, blockSize),
+		outUsed: 0,
+	}
+	prefix := make([]byte, blockSize+2)
+
+	block.Encrypt(x.fre, x.fre)
+	for i := 0; i < blockSize; i++ {
+		prefix[i] = randData[i] ^ x.fre[i]
+	}
+
+	block.Encrypt(x.fre, prefix[:blockSize])
+	prefix[blockSize] = x.fre[0] ^ randData[blockSize-2]
+	prefix[blockSize+1] = x.fre[1] ^ randData[blockSize-1]
+
+	block.Encrypt(x.fre, prefix[2:])
+	return x, prefix
+}
+
+func (x *ocfbEncrypter) XORKeyStream(dst, src []byte) {
+	for i := 0; i < len(src); i++ {
+		if x.outUsed == len(x.fre) {
+			x.b.Encrypt(x.fre, x.fre)
+			x.outUsed = 0
+		}
+
+		x.fre[x.outUsed] ^= src[i]
+		dst[i] = x.fre[x.outUsed]
+		x.outUsed++
+	}
+}
+
+type ocfbDecrypter struct {
+	b       Block
+	fre     []byte
+	outUsed int
+}
+
+// NewOCFBDecrypter returns a Stream which decrypts data with OpenPGP's cipher
+// feedback mode using the given Block. Prefix must be the first blockSize + 2
+// bytes of the ciphertext, where blockSize is the Block's block size. If an
+// incorrect key is detected then nil is returned.
+func NewOCFBDecrypter(block Block, prefix []byte) Stream {
+	blockSize := block.BlockSize()
+	if len(prefix) != blockSize+2 {
+		return nil
+	}
+
+	x := &ocfbDecrypter{
+		b:       block,
+		fre:     make([]byte, blockSize),
+		outUsed: 0,
+	}
+	prefixCopy := make([]byte, len(prefix))
+	copy(prefixCopy, prefix)
+
+	block.Encrypt(x.fre, x.fre)
+	for i := 0; i < blockSize; i++ {
+		prefixCopy[i] ^= x.fre[i]
+	}
+
+	block.Encrypt(x.fre, prefix[:blockSize])
+	prefixCopy[blockSize] ^= x.fre[0]
+	prefixCopy[blockSize+1] ^= x.fre[1]
+
+	if prefixCopy[blockSize-2] != prefixCopy[blockSize] ||
+		prefixCopy[blockSize-1] != prefixCopy[blockSize+1] {
+		return nil
+	}
+
+	block.Encrypt(x.fre, prefix[2:])
+	return x
+}
+
+func (x *ocfbDecrypter) XORKeyStream(dst, src []byte) {
+	for i := 0; i < len(src); i++ {
+		if x.outUsed == len(x.fre) {
+			x.b.Encrypt(x.fre, x.fre)
+			x.outUsed = 0
+		}
+
+		c := src[i]
+		dst[i] = x.fre[x.outUsed] ^ src[i]
+		x.fre[x.outUsed] = c
+		x.outUsed++
+	}
+}