Stephan Mueller reported to me recently a error in random number generation in
the ansi cprng. If several small requests are made that are less than the
instances block size, the remainder for loop code doesn't increment
rand_data_valid in the last iteration, meaning that the last bytes in the
rand_data buffer gets reused on the subsequent smaller-than-a-block request for
random data.
The fix is pretty easy, just re-code the for loop to make sure that
rand_data_valid gets incremented appropriately
Signed-off-by: Neil Horman nhor...@tuxdriver.com
Reported-by: Stephan Mueller stephan.muel...@atsec.com
CC: Stephan Mueller stephan.muel...@atsec.com
CC: Petr Matousek pmato...@redhat.com
CC: Herbert Xu herb...@gondor.apana.org.au
CC: David S. Miller da...@davemloft.net
---
crypto/ansi_cprng.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/crypto/ansi_cprng.c b/crypto/ansi_cprng.c
index c0bb377..666f196 100644
--- a/crypto/ansi_cprng.c
+++ b/crypto/ansi_cprng.c
@@ -230,11 +230,11 @@ remainder:
*/
if (byte_count DEFAULT_BLK_SZ) {
empty_rbuf:
- for (; ctx-rand_data_valid DEFAULT_BLK_SZ;
- ctx-rand_data_valid++) {
+ while (ctx-rand_data_valid DEFAULT_BLK_SZ) {
*ptr = ctx-rand_data[ctx-rand_data_valid];
ptr++;
byte_count--;
+ ctx-rand_data_valid++;
if (byte_count == 0)
goto done;
}
--
1.8.3.1
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