From 6d31920246a9fc80be4f16acd27c0bbe8d7b8494 Mon Sep 17 00:00:00 2001 From: Hannes Frederic Sowa Date: Mon, 11 Nov 2013 12:20:33 +0100 Subject: 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 Cc: Theodore Ts'o Signed-off-by: Hannes Frederic Sowa Signed-off-by: Daniel Borkmann Signed-off-by: David S. Miller --- lib/random32.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) 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); -- cgit v1.2.3