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crypto: michael_mic - fix broken misalignment handling 

The Michael MIC driver uses the cra_alignmask to ensure that pointers
presented to its update and finup/final methods are 32-bit aligned.
However, due to the way the shash API works, this is no guarantee that
the 32-bit reads occurring in the update method are also aligned, as the
size of the buffer presented to update may be of uneven length. For
instance, an update() of 3 bytes followed by a misaligned update() of 4
or more bytes will result in a misaligned access using an accessor that
is not suitable for this.

On most architectures, this does not matter, and so setting the
cra_alignmask is pointless. On architectures where this does matter,
setting the cra_alignmask does not actually solve the problem.

So let's get rid of the cra_alignmask, and use unaligned accessors
instead, where appropriate.

Cc: <stable@vger.kernel.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Ard Biesheuvel 2021-02-01 19:02:29 +01:00 committed by Herbert Xu
parent e145f5565d
commit e1b2d980f0
1 changed files with 12 additions and 19 deletions
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31
crypto/michael_mic.c
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@ -7,7 +7,7 @@
* Copyright (c) 2004 Jouni Malinen <j@w1.fi>
*/
#include <crypto/internal/hash.h>
#include <asm/byteorder.h>
#include <asm/unaligned.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/string.h>
@ -19,7 +19,7 @@ struct michael_mic_ctx {
};
struct michael_mic_desc_ctx {
u8 pending[4];
__le32 pending;
size_t pending_len;
u32 l, r;
@ -60,13 +60,12 @@ static int michael_update(struct shash_desc *desc, const u8 *data,
unsigned int len)
{
struct michael_mic_desc_ctx *mctx = shash_desc_ctx(desc);
const __le32 *src;
if (mctx->pending_len) {
int flen = 4 - mctx->pending_len;
if (flen > len)
flen = len;
memcpy(&mctx->pending[mctx->pending_len], data, flen);
memcpy((u8 *)&mctx->pending + mctx->pending_len, data, flen);
mctx->pending_len += flen;
data += flen;
len -= flen;
@ -74,23 +73,21 @@ static int michael_update(struct shash_desc *desc, const u8 *data,
if (mctx->pending_len < 4)
return 0;
src = (const __le32 *)mctx->pending;
mctx->l ^= le32_to_cpup(src);
mctx->l ^= le32_to_cpu(mctx->pending);
michael_block(mctx->l, mctx->r);
mctx->pending_len = 0;
}
src = (const __le32 *)data;
while (len >= 4) {
mctx->l ^= le32_to_cpup(src++);
mctx->l ^= get_unaligned_le32(data);
michael_block(mctx->l, mctx->r);
data += 4;
len -= 4;
}
if (len > 0) {
mctx->pending_len = len;
memcpy(mctx->pending, src, len);
memcpy(&mctx->pending, data, len);
}
return 0;
@ -100,8 +97,7 @@ static int michael_update(struct shash_desc *desc, const u8 *data,
static int michael_final(struct shash_desc *desc, u8 *out)
{
struct michael_mic_desc_ctx *mctx = shash_desc_ctx(desc);
u8 *data = mctx->pending;
__le32 *dst = (__le32 *)out;
u8 *data = (u8 *)&mctx->pending;
/* Last block and padding (0x5a, 4..7 x 0) */
switch (mctx->pending_len) {
@ -123,8 +119,8 @@ static int michael_final(struct shash_desc *desc, u8 *out)
/* l ^= 0; */
michael_block(mctx->l, mctx->r);
dst[0] = cpu_to_le32(mctx->l);
dst[1] = cpu_to_le32(mctx->r);
put_unaligned_le32(mctx->l, out);
put_unaligned_le32(mctx->r, out + 4);
return 0;
}
@ -135,13 +131,11 @@ static int michael_setkey(struct crypto_shash *tfm, const u8 *key,
{
struct michael_mic_ctx *mctx = crypto_shash_ctx(tfm);
const __le32 *data = (const __le32 *)key;
if (keylen != 8)
return -EINVAL;
mctx->l = le32_to_cpu(data[0]);
mctx->r = le32_to_cpu(data[1]);
mctx->l = get_unaligned_le32(key);
mctx->r = get_unaligned_le32(key + 4);
return 0;
}
@ -156,7 +150,6 @@ static struct shash_alg alg = {
.cra_name = "michael_mic",
.cra_driver_name = "michael_mic-generic",
.cra_blocksize = 8,
.cra_alignmask = 3,
.cra_ctxsize = sizeof(struct michael_mic_ctx),
.cra_module = THIS_MODULE,
}