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crypto: ofb - fix handling partial blocks and make thread-safe

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Fix multiple bugs in the OFB implementation:

1. It stored the per-request state 'cnt' in the tfm context, which can be
   used by multiple threads concurrently (e.g. via AF_ALG).
2. It didn't support messages not a multiple of the block cipher size,
   despite being a stream cipher.
3. It didn't set cra_blocksize to 1 to indicate it is a stream cipher.

To fix these, set the 'chunksize' property to the cipher block size to
guarantee that when walking through the scatterlist, a partial block can
only occur at the end.  Then change the implementation to XOR a block at
a time at first, then XOR the partial block at the end if needed.  This
is the same way CTR and CFB are implemented.  As a bonus, this also
improves performance in most cases over the current approach.

Fixes: e497c51896 ("crypto: ofb - add output feedback mode")
Cc: <stable@vger.kernel.org> # v4.20+
Cc: Gilad Ben-Yossef <gilad@benyossef.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Gilad Ben-Yossef <gilad@benyossef.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Eric Biggers
2019-01-03 20:16:12 -08:00
committed by Herbert Xu
parent 6c2e322b36
commit b3e3e2db7d
2 changed files with 64 additions and 57 deletions
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28
crypto/testmgr.h
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@@ -16681,8 +16681,7 @@ static const struct cipher_testvec aes_ctr_rfc3686_tv_template[] = {
};
static const struct cipher_testvec aes_ofb_tv_template[] = {
/* From NIST Special Publication 800-38A, Appendix F.5 */
{
{ /* From NIST Special Publication 800-38A, Appendix F.5 */
.key = "\x2b\x7e\x15\x16\x28\xae\xd2\xa6"
"\xab\xf7\x15\x88\x09\xcf\x4f\x3c",
.klen = 16,
@@ -16705,6 +16704,31 @@ static const struct cipher_testvec aes_ofb_tv_template[] = {
"\x30\x4c\x65\x28\xf6\x59\xc7\x78"
"\x66\xa5\x10\xd9\xc1\xd6\xae\x5e",
.len = 64,
.also_non_np = 1,
.np = 2,
.tap = { 31, 33 },
}, { /* > 16 bytes, not a multiple of 16 bytes */
.key = "\x2b\x7e\x15\x16\x28\xae\xd2\xa6"
"\xab\xf7\x15\x88\x09\xcf\x4f\x3c",
.klen = 16,
.iv = "\x00\x01\x02\x03\x04\x05\x06\x07"
"\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f",
.ptext = "\x6b\xc1\xbe\xe2\x2e\x40\x9f\x96"
"\xe9\x3d\x7e\x11\x73\x93\x17\x2a"
"\xae",
.ctext = "\x3b\x3f\xd9\x2e\xb7\x2d\xad\x20"
"\x33\x34\x49\xf8\xe8\x3c\xfb\x4a"
"\x77",
.len = 17,
}, { /* < 16 bytes */
.key = "\x2b\x7e\x15\x16\x28\xae\xd2\xa6"
"\xab\xf7\x15\x88\x09\xcf\x4f\x3c",
.klen = 16,
.iv = "\x00\x01\x02\x03\x04\x05\x06\x07"
"\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f",
.ptext = "\x6b\xc1\xbe\xe2\x2e\x40\x9f",
.ctext = "\x3b\x3f\xd9\x2e\xb7\x2d\xad",
.len = 7,
}
};