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authorDaniel Borkmann <dborkman@redhat.com>2013-11-11 12:20:32 +0100
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-12-08 07:29:41 -0800
commit4dd7a52b53ab79e8990bb295a2907d47345d2fa2 (patch)
tree68e671edcbc17a2b0a5df560bd05c1f28b81c1e2 /lib
parent4bb2cc8ea8b76426dcb60b95d27d599cb426bcf9 (diff)
random32: fix off-by-one in seeding requirement
[ Upstream commit 51c37a70aaa3f95773af560e6db3073520513912 ] For properly initialising the Tausworthe generator [1], we have a strict seeding requirement, that is, s1 > 1, s2 > 7, s3 > 15. Commit 697f8d0348 ("random32: seeding improvement") introduced a __seed() function that imposes boundary checks proposed by the errata paper [2] to properly ensure above conditions. However, we're off by one, as the function is implemented as: "return (x < m) ? x + m : x;", and called with __seed(X, 1), __seed(X, 7), __seed(X, 15). Thus, an unwanted seed of 1, 7, 15 would be possible, whereas the lower boundary should actually be of at least 2, 8, 16, just as GSL does. Fix this, as otherwise an initialization with an unwanted seed could have the effect that Tausworthe's PRNG properties cannot not be ensured. Note that this PRNG is *not* used for cryptography in the kernel. [1] http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme.ps [2] http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme2.ps Joint work with Hannes Frederic Sowa. Fixes: 697f8d0348a6 ("random32: seeding improvement") Cc: Stephen Hemminger <stephen@networkplumber.org> Cc: Florian Weimer <fweimer@redhat.com> Cc: Theodore Ts'o <tytso@mit.edu> Signed-off-by: Daniel Borkmann <dborkman@redhat.com> Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org> Signed-off-by: David S. Miller <davem@davemloft.net> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'lib')
-rw-r--r--lib/random32.c14
1 files changed, 7 insertions, 7 deletions
diff --git a/lib/random32.c b/lib/random32.c
index 938bde5876ac..aa95712c1431 100644
--- a/lib/random32.c
+++ b/lib/random32.c
@@ -92,7 +92,7 @@ void srandom32(u32 entropy)
*/
for_each_possible_cpu (i) {
struct rnd_state *state = &per_cpu(net_rand_state, i);
- state->s1 = __seed(state->s1 ^ entropy, 1);
+ state->s1 = __seed(state->s1 ^ entropy, 2);
}
}
EXPORT_SYMBOL(srandom32);
@@ -109,9 +109,9 @@ static int __init random32_init(void)
struct rnd_state *state = &per_cpu(net_rand_state,i);
#define LCG(x) ((x) * 69069) /* super-duper LCG */
- state->s1 = __seed(LCG(i + jiffies), 1);
- state->s2 = __seed(LCG(state->s1), 7);
- state->s3 = __seed(LCG(state->s2), 15);
+ state->s1 = __seed(LCG(i + jiffies), 2);
+ state->s2 = __seed(LCG(state->s1), 8);
+ state->s3 = __seed(LCG(state->s2), 16);
/* "warm it up" */
prandom32(state);
@@ -138,9 +138,9 @@ static int __init random32_reseed(void)
u32 seeds[3];
get_random_bytes(&seeds, sizeof(seeds));
- state->s1 = __seed(seeds[0], 1);
- state->s2 = __seed(seeds[1], 7);
- state->s3 = __seed(seeds[2], 15);
+ state->s1 = __seed(seeds[0], 2);
+ state->s2 = __seed(seeds[1], 8);
+ state->s3 = __seed(seeds[2], 16);
/* mix it in */
prandom32(state);