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authorJarod Wilson <jarod@redhat.com>2008-11-13 22:03:20 +0800
committerHerbert Xu <herbert@gondor.apana.org.au>2008-12-25 11:01:47 +1100
commitaa1a85dbd1d3265ca36f684026fe7689b7836bed (patch)
tree02a609343c67482352f8319b952454d0c006d1b1 /crypto
parent31a61bfc6e415fbd871317cbee7b8a4158d8ac5b (diff)
downloadconfigs-aa1a85dbd1d3265ca36f684026fe7689b7836bed.tar.gz
crypto: ansi_cprng - Avoid incorrect extra call to _get_more_prng_bytes
While working with some FIPS RNGVS test vectors yesterday, I discovered a little bug in the way the ansi_cprng code works right now. For example, the following test vector (complete with expected result) from http://csrc.nist.gov/groups/STM/cavp/documents/rng/RNGVS.pdf ... Key = f3b1666d13607242ed061cabb8d46202 DT = e6b3be782a23fa62d71d4afbb0e922fc V = f0000000000000000000000000000000 R = 88dda456302423e5f69da57e7b95c73a ...when run through ansi_cprng, yields an incorrect R value of e2afe0d794120103d6e86a2b503bdfaa. If I load up ansi_cprng w/dbg=1 though, it was fairly obvious what was going wrong: ----8<---- getting 16 random bytes for context ffff810033fb2b10 Calling _get_more_prng_bytes for context ffff810033fb2b10 Input DT: 00000000: e6 b3 be 78 2a 23 fa 62 d7 1d 4a fb b0 e9 22 fc Input I: 00000000: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 Input V: 00000000: f0 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 tmp stage 0: 00000000: e6 b3 be 78 2a 23 fa 62 d7 1d 4a fb b0 e9 22 fc tmp stage 1: 00000000: f4 8e cb 25 94 3e 8c 31 d6 14 cd 8a 23 f1 3f 84 tmp stage 2: 00000000: 8c 53 6f 73 a4 1a af d4 20 89 68 f4 58 64 f8 be Returning new block for context ffff810033fb2b10 Output DT: 00000000: e7 b3 be 78 2a 23 fa 62 d7 1d 4a fb b0 e9 22 fc Output I: 00000000: 04 8e cb 25 94 3e 8c 31 d6 14 cd 8a 23 f1 3f 84 Output V: 00000000: 48 89 3b 71 bc e4 00 b6 5e 21 ba 37 8a 0a d5 70 New Random Data: 00000000: 88 dd a4 56 30 24 23 e5 f6 9d a5 7e 7b 95 c7 3a Calling _get_more_prng_bytes for context ffff810033fb2b10 Input DT: 00000000: e7 b3 be 78 2a 23 fa 62 d7 1d 4a fb b0 e9 22 fc Input I: 00000000: 04 8e cb 25 94 3e 8c 31 d6 14 cd 8a 23 f1 3f 84 Input V: 00000000: 48 89 3b 71 bc e4 00 b6 5e 21 ba 37 8a 0a d5 70 tmp stage 0: 00000000: e7 b3 be 78 2a 23 fa 62 d7 1d 4a fb b0 e9 22 fc tmp stage 1: 00000000: 80 6b 3a 8c 23 ae 8f 53 be 71 4c 16 fc 13 b2 ea tmp stage 2: 00000000: 2a 4d e1 2a 0b 58 8e e6 36 b8 9c 0a 26 22 b8 30 Returning new block for context ffff810033fb2b10 Output DT: 00000000: e8 b3 be 78 2a 23 fa 62 d7 1d 4a fb b0 e9 22 fc Output I: 00000000: c8 e2 01 fd 9f 4a 8f e5 e0 50 f6 21 76 19 67 9a Output V: 00000000: ba 98 e3 75 c0 1b 81 8d 03 d6 f8 e2 0c c6 54 4b New Random Data: 00000000: e2 af e0 d7 94 12 01 03 d6 e8 6a 2b 50 3b df aa returning 16 from get_prng_bytes in context ffff810033fb2b10 ----8<---- The expected result is there, in the first "New Random Data", but we're incorrectly making a second call to _get_more_prng_bytes, due to some checks that are slightly off, which resulted in our original bytes never being returned anywhere. One approach to fixing this would be to alter some byte_count checks in get_prng_bytes, but it would mean the last DEFAULT_BLK_SZ bytes would be copied a byte at a time, rather than in a single memcpy, so a slightly more involved, equally functional, and ultimately more efficient way of fixing this was suggested to me by Neil, which I'm submitting here. All of the RNGVS ANSI X9.31 AES128 VST test vectors I've passed through ansi_cprng are now returning the expected results with this change. Signed-off-by: Jarod Wilson <jarod@redhat.com> Acked-by: Neil Horman <nhorman@tuxdriver.com> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Diffstat (limited to 'crypto')
-rw-r--r--crypto/ansi_cprng.c17
1 files changed, 11 insertions, 6 deletions
diff --git a/crypto/ansi_cprng.c b/crypto/ansi_cprng.c
index 486aa93646f..1b3b1da1fd3 100644
--- a/crypto/ansi_cprng.c
+++ b/crypto/ansi_cprng.c
@@ -223,9 +223,10 @@ remainder:
}
/*
- * Copy up to the next whole block size
+ * Copy any data less than an entire block
*/
if (byte_count < DEFAULT_BLK_SZ) {
+empty_rbuf:
for (; ctx->rand_data_valid < DEFAULT_BLK_SZ;
ctx->rand_data_valid++) {
*ptr = ctx->rand_data[ctx->rand_data_valid];
@@ -240,18 +241,22 @@ remainder:
* Now copy whole blocks
*/
for (; byte_count >= DEFAULT_BLK_SZ; byte_count -= DEFAULT_BLK_SZ) {
- if (_get_more_prng_bytes(ctx) < 0) {
- memset(buf, 0, nbytes);
- err = -EINVAL;
- goto done;
+ if (ctx->rand_data_valid == DEFAULT_BLK_SZ) {
+ if (_get_more_prng_bytes(ctx) < 0) {
+ memset(buf, 0, nbytes);
+ err = -EINVAL;
+ goto done;
+ }
}
+ if (ctx->rand_data_valid > 0)
+ goto empty_rbuf;
memcpy(ptr, ctx->rand_data, DEFAULT_BLK_SZ);
ctx->rand_data_valid += DEFAULT_BLK_SZ;
ptr += DEFAULT_BLK_SZ;
}
/*
- * Now copy any extra partial data
+ * Now go back and get any remaining partial block
*/
if (byte_count)
goto remainder;