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crypto/{aes,cipher,rc4}: fix out of bounds write in stream ciphers

Functions XORKeyStream should panic if len(dst) < len(src), but it
write to dst before bounds checking. In asm routines and fastXORBytes,
this is an out of bounds write.

Fixes #21104

Change-Id: I354346cda8d63910f3bb619416ffd54cd0a04a0b
Reviewed-on: https://go-review.googlesource.com/52050
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Wei Congrui 2017-07-29 18:23:00 +08:00 committed by Brad Fitzpatrick
parent bef0055a0a
commit 254f8ea9ea
4 changed files with 74 additions and 2 deletions

View File

@ -64,6 +64,10 @@ func (c *aesctr) refill() {
}
func (c *aesctr) XORKeyStream(dst, src []byte) {
if len(src) > 0 {
// Assert len(dst) >= len(src)
_ = dst[len(src)-1]
}
for len(src) > 0 {
if len(c.buffer) == 0 {
c.refill()

View File

@ -19,6 +19,11 @@ func fastXORBytes(dst, a, b []byte) int {
if len(b) < n {
n = len(b)
}
if n == 0 {
return 0
}
// Assert dst has enough space
_ = dst[n-1]
w := n / wordSize
if w > 0 {
@ -48,8 +53,8 @@ func safeXORBytes(dst, a, b []byte) int {
return n
}
// xorBytes xors the bytes in a and b. The destination is assumed to have enough
// space. Returns the number of bytes xor'd.
// xorBytes xors the bytes in a and b. The destination should have enough
// space, otherwise xorBytes will panic. Returns the number of bytes xor'd.
func xorBytes(dst, a, b []byte) int {
if supportsUnaligned {
return fastXORBytes(dst, a, b)

View File

@ -0,0 +1,61 @@
// Copyright 2017 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.
package crypto
import (
"crypto/aes"
"crypto/cipher"
"crypto/rc4"
"testing"
)
func TestRC4OutOfBoundsWrite(t *testing.T) {
// This cipherText is encrypted "0123456789"
cipherText := []byte{238, 41, 187, 114, 151, 2, 107, 13, 178, 63}
cipher, err := rc4.NewCipher([]byte{0})
if err != nil {
panic(err)
}
test(t, "RC4", cipherText, cipher.XORKeyStream)
}
func TestCTROutOfBoundsWrite(t *testing.T) {
testBlock(t, "CTR", cipher.NewCTR)
}
func TestOFBOutOfBoundsWrite(t *testing.T) {
testBlock(t, "OFB", cipher.NewOFB)
}
func TestCFBEncryptOutOfBoundsWrite(t *testing.T) {
testBlock(t, "CFB Encrypt", cipher.NewCFBEncrypter)
}
func TestCFBDecryptOutOfBoundsWrite(t *testing.T) {
testBlock(t, "CFB Decrypt", cipher.NewCFBDecrypter)
}
func testBlock(t *testing.T, name string, newCipher func(cipher.Block, []byte) cipher.Stream) {
// This cipherText is encrypted "0123456789"
cipherText := []byte{86, 216, 121, 231, 219, 191, 26, 12, 176, 117}
var iv, key [16]byte
block, err := aes.NewCipher(key[:])
if err != nil {
panic(err)
}
stream := newCipher(block, iv[:])
test(t, name, cipherText, stream.XORKeyStream)
}
func test(t *testing.T, name string, cipherText []byte, xor func([]byte, []byte)) {
want := "abcdefghij"
plainText := []byte(want)
shorterLen := len(cipherText) / 2
defer func() {
err := recover()
if err == nil {
t.Errorf("%v XORKeyStream expected to panic on len(dst) < len(src), but didn't", name)
}
const plain = "0123456789"
if plainText[shorterLen] == plain[shorterLen] {
t.Errorf("%v XORKeyStream did out of bounds write, want %v, got %v", name, want, string(plainText))
}
}()
xor(plainText[:shorterLen], cipherText)
}

View File

@ -14,5 +14,7 @@ func (c *Cipher) XORKeyStream(dst, src []byte) {
if len(src) == 0 {
return
}
// Assert len(dst) >= len(src)
_ = dst[len(src)-1]
xorKeyStream(&dst[0], &src[0], len(src), &c.s, &c.i, &c.j)
}