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| author | Hannes Frederic Sowa <hannes@stressinduktion.org> | 2013-11-11 15:20:33 +0400 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2013-11-11 23:32:14 +0400 |
| commit | 6d31920246a9fc80be4f16acd27c0bbe8d7b8494 (patch) | |
| tree | 59cf494b43a77fd528c77364c2376e65975a128a /lib/random32.c | |
| parent | 51c37a70aaa3f95773af560e6db3073520513912 (diff) | |
| download | linux-6d31920246a9fc80be4f16acd27c0bbe8d7b8494.tar.xz | |
random32: add periodic reseeding
The current Tausworthe PRNG is never reseeded with truly random data after
the first attempt in late_initcall. As this PRNG is used for some critical
random data as e.g. UDP port randomization we should try better and reseed
the PRNG once in a while with truly random data from get_random_bytes().
When we reseed with prandom_seed we now make also sure to throw the first
output away. This suffices the reseeding procedure.
The delay calculation is based on a proposal from Eric Dumazet.
Joint work with Daniel Borkmann.
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'lib/random32.c')
| -rw-r--r-- | lib/random32.c | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/lib/random32.c b/lib/random32.c index 01e8890d1089..12215df701e8 100644 --- a/lib/random32.c +++ b/lib/random32.c @@ -142,6 +142,7 @@ void prandom_seed(u32 entropy) for_each_possible_cpu (i) { struct rnd_state *state = &per_cpu(net_rand_state, i); state->s1 = __seed(state->s1 ^ entropy, 2); + prandom_u32_state(state); } } EXPORT_SYMBOL(prandom_seed); @@ -174,6 +175,27 @@ static int __init prandom_init(void) } core_initcall(prandom_init); +static void __prandom_timer(unsigned long dontcare); +static DEFINE_TIMER(seed_timer, __prandom_timer, 0, 0); + +static void __prandom_timer(unsigned long dontcare) +{ + u32 entropy; + + get_random_bytes(&entropy, sizeof(entropy)); + prandom_seed(entropy); + /* reseed every ~60 seconds, in [40 .. 80) interval with slack */ + seed_timer.expires = jiffies + (40 * HZ + (prandom_u32() % (40 * HZ))); + add_timer(&seed_timer); +} + +static void prandom_start_seed_timer(void) +{ + set_timer_slack(&seed_timer, HZ); + seed_timer.expires = jiffies + 40 * HZ; + add_timer(&seed_timer); +} + /* * Generate better values after random number generator * is fully initialized. @@ -194,6 +216,7 @@ static int __init prandom_reseed(void) /* mix it in */ prandom_u32_state(state); } + prandom_start_seed_timer(); return 0; } late_initcall(prandom_reseed); |