crypto/cipher: fix OCFB

I messed up when reading the OCFB spec.

TBR=rsc

R=rsc
CC=golang-dev
https://golang.org/cl/3739042

diff --git a/src/pkg/crypto/cipher/ocfb.go b/src/pkg/crypto/cipher/ocfb.go
index 08565dc5f85c1076ebf4dbd55c199be2f103877d..43cb5a53108334277eb63ccddabf31efb109a02b 100644 (file)
--- a/src/pkg/crypto/cipher/ocfb.go
+++ b/src/pkg/crypto/cipher/ocfb.go
@@ -6,7 +6,7 @@
 
 package cipher
 
-type ocfb struct {
+type ocfbEncrypter struct {
        b       Block
        fre     []byte
        outUsed int
@@ -22,7 +22,7 @@ func NewOCFBEncrypter(block Block, randData []byte) (Stream, []byte) {
                return nil, nil
        }
 
-       x := &ocfb{
+       x := &ocfbEncrypter{
                b:       block,
                fre:     make([]byte, blockSize),
                outUsed: 0,
@@ -42,6 +42,25 @@ func NewOCFBEncrypter(block Block, randData []byte) (Stream, []byte) {
        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
@@ -52,7 +71,7 @@ func NewOCFBDecrypter(block Block, prefix []byte) Stream {
                return nil
        }
 
-       x := &ocfb{
+       x := &ocfbDecrypter{
                b:       block,
                fre:     make([]byte, blockSize),
                outUsed: 0,
@@ -78,14 +97,16 @@ func NewOCFBDecrypter(block Block, prefix []byte) Stream {
        return x
 }
 
-func (x *ocfb) XORKeyStream(dst, src []byte) {
+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++
        }
 }