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crypto/cipher: fix CTR infinite loop with large block sizes
Additionally, add a test for CTR mode to cover a range of block sizes. Fixes golang#12975 Change-Id: I458aac1616228747e62f92f823768d55e874877a Reviewed-on: https://go-review.googlesource.com/16050 Reviewed-by: Adam Langley <[email protected]>
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// Copyright 2015 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. | ||
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package cipher_test | ||
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import ( | ||
"bytes" | ||
"crypto/cipher" | ||
"testing" | ||
) | ||
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type noopBlock int | ||
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func (b noopBlock) BlockSize() int { return int(b) } | ||
func (noopBlock) Encrypt(dst, src []byte) { copy(dst, src) } | ||
func (noopBlock) Decrypt(dst, src []byte) { copy(dst, src) } | ||
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func inc(b []byte) { | ||
for i := len(b) - 1; i >= 0; i++ { | ||
b[i]++ | ||
if b[i] != 0 { | ||
break | ||
} | ||
} | ||
} | ||
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func xor(a, b []byte) { | ||
for i := range a { | ||
a[i] ^= b[i] | ||
} | ||
} | ||
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func TestCTR(t *testing.T) { | ||
for size := 64; size <= 1024; size *= 2 { | ||
iv := make([]byte, size) | ||
ctr := cipher.NewCTR(noopBlock(size), iv) | ||
src := make([]byte, 1024) | ||
for i := range src { | ||
src[i] = 0xff | ||
} | ||
want := make([]byte, 1024) | ||
copy(want, src) | ||
counter := make([]byte, size) | ||
for i := 1; i < len(want)/size; i++ { | ||
inc(counter) | ||
xor(want[i*size:(i+1)*size], counter) | ||
} | ||
dst := make([]byte, 1024) | ||
ctr.XORKeyStream(dst, src) | ||
if !bytes.Equal(dst, want) { | ||
t.Errorf("for size %d\nhave %x\nwant %x", size, dst, want) | ||
} | ||
} | ||
} |