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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-16 19:23:18 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-16 19:23:18 +0000
commit43a123c1ae6613b3efeed291fa552ecd909d3acf (patch)
treefd92518b7024bc74031f78a1cf9e454b65e73665 /src/crypto/cipher/ofb.go
parentInitial commit. (diff)
downloadgolang-1.20-43a123c1ae6613b3efeed291fa552ecd909d3acf.tar.xz
golang-1.20-43a123c1ae6613b3efeed291fa552ecd909d3acf.zip
Adding upstream version 1.20.14.upstream/1.20.14upstream
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'src/crypto/cipher/ofb.go')
-rw-r--r--src/crypto/cipher/ofb.go77
1 files changed, 77 insertions, 0 deletions
diff --git a/src/crypto/cipher/ofb.go b/src/crypto/cipher/ofb.go
new file mode 100644
index 0000000..1195fdd
--- /dev/null
+++ b/src/crypto/cipher/ofb.go
@@ -0,0 +1,77 @@
+// Copyright 2011 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.
+
+// OFB (Output Feedback) Mode.
+
+package cipher
+
+import (
+ "crypto/internal/alias"
+ "crypto/subtle"
+)
+
+type ofb struct {
+ b Block
+ cipher []byte
+ out []byte
+ outUsed int
+}
+
+// NewOFB returns a Stream that encrypts or decrypts using the block cipher b
+// in output feedback mode. The initialization vector iv's length must be equal
+// to b's block size.
+func NewOFB(b Block, iv []byte) Stream {
+ blockSize := b.BlockSize()
+ if len(iv) != blockSize {
+ panic("cipher.NewOFB: IV length must equal block size")
+ }
+ bufSize := streamBufferSize
+ if bufSize < blockSize {
+ bufSize = blockSize
+ }
+ x := &ofb{
+ b: b,
+ cipher: make([]byte, blockSize),
+ out: make([]byte, 0, bufSize),
+ outUsed: 0,
+ }
+
+ 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) {
+ if len(dst) < len(src) {
+ panic("crypto/cipher: output smaller than input")
+ }
+ if alias.InexactOverlap(dst[:len(src)], src) {
+ panic("crypto/cipher: invalid buffer overlap")
+ }
+ for len(src) > 0 {
+ if x.outUsed >= len(x.out)-x.b.BlockSize() {
+ x.refill()
+ }
+ n := subtle.XORBytes(dst, src, x.out[x.outUsed:])
+ dst = dst[n:]
+ src = src[n:]
+ x.outUsed += n
+ }
+}