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path: root/src/pkg/crypto/cipher/ofb.go
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Diffstat (limited to 'src/pkg/crypto/cipher/ofb.go')
-rw-r--r--src/pkg/crypto/cipher/ofb.go42
1 files changed, 32 insertions, 10 deletions
diff --git a/src/pkg/crypto/cipher/ofb.go b/src/pkg/crypto/cipher/ofb.go
index 85e5f02b0..e86ebcb23 100644
--- a/src/pkg/crypto/cipher/ofb.go
+++ b/src/pkg/crypto/cipher/ofb.go
@@ -8,6 +8,7 @@ package cipher
type ofb struct {
b Block
+ cipher []byte
out []byte
outUsed int
}
@@ -20,25 +21,46 @@ func NewOFB(b Block, iv []byte) Stream {
if len(iv) != blockSize {
return nil
}
-
+ bufSize := streamBufferSize
+ if bufSize < blockSize {
+ bufSize = blockSize
+ }
x := &ofb{
b: b,
- out: make([]byte, blockSize),
+ cipher: make([]byte, blockSize),
+ out: make([]byte, 0, bufSize),
outUsed: 0,
}
- b.Encrypt(x.out, iv)
+ copy(x.cipher, iv)
return x
}
+func (x *ofb) refill() {
+ bs := x.b.BlockSize()
+ remain := len(x.out) - x.outUsed
+ if remain > x.outUsed {
+ return
+ }
+ copy(x.out, x.out[x.outUsed:])
+ x.out = x.out[:cap(x.out)]
+ for remain < len(x.out)-bs {
+ x.b.Encrypt(x.cipher, x.cipher)
+ copy(x.out[remain:], x.cipher)
+ remain += bs
+ }
+ x.out = x.out[:remain]
+ x.outUsed = 0
+}
+
func (x *ofb) XORKeyStream(dst, src []byte) {
- for i, s := range src {
- if x.outUsed == len(x.out) {
- x.b.Encrypt(x.out, x.out)
- x.outUsed = 0
+ for len(src) > 0 {
+ if x.outUsed >= len(x.out)-x.b.BlockSize() {
+ x.refill()
}
-
- dst[i] = s ^ x.out[x.outUsed]
- x.outUsed++
+ n := xorBytes(dst, src, x.out[x.outUsed:])
+ dst = dst[n:]
+ src = src[n:]
+ x.outUsed += n
}
}