user/sven/linux.git/lib/random32.c, branch v4.4.151

random32: add prandom_init_once helper for own rngs

2015-10-08T12:26:38Z

Add a prandom_init_once() facility that works on the rnd_state, so that users that are keeping their own state independent from prandom_u32() can initialize their taus113 per cpu states. The motivation here is similar to net_get_random_once(): initialize the state as late as possible in the hope that enough entropy has been collected for the seeding. prandom_init_once() makes use of the recently introduced prandom_seed_full_state() helper and is generic enough so that it could also be used on fast-paths due to the DO_ONCE(). Signed-off-by: Daniel Borkmann Acked-by: Hannes Frederic Sowa Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller

random32: add prandom_seed_full_state helper

2015-10-08T12:26:37Z

Factor out the full reseed handling code that populates the state through get_random_bytes() and runs prandom_warmup(). The resulting prandom_seed_full_state() will be used later on in more than the current __prandom_reseed() user. Fix also two minor whitespace issues along the way. Signed-off-by: Daniel Borkmann Acked-by: Hannes Frederic Sowa Acked-by: Alexei Starovoitov Signed-off-by: David S. Miller

random32: improvements to prandom_bytes

2014-08-25T01:36:01Z

This patch addresses a couple of minor items, mostly addesssing prandom_bytes(): 1) prandom_bytes{,_state}() should use size_t for length arguments, 2) We can use put_unaligned() when filling the array instead of open coding it [ perhaps some archs will further benefit from their own arch specific implementation when GCC cannot make up for it ], 3) Fix a typo, 4) Better use unsigned int as type for getting the arch seed, 5) Make use of prandom_u32_max() for timer slack. Regarding the change to put_unaligned(), callers of prandom_bytes() which internally invoke prandom_bytes_state(), don't bother as they expect the array to be filled randomly and don't have any control of the internal state what-so-ever (that's also why we have periodic reseeding there, etc), so they really don't care. Now for the direct callers of prandom_bytes_state(), which are solely located in test cases for MTD devices, that is, drivers/mtd/tests/{oobtest.c,pagetest.c,subpagetest.c}: These tests basically fill a test write-vector through prandom_bytes_state() with an a-priori defined seed each time and write that to a MTD device. Later on, they set up a read-vector and read back that blocks from the device. So in the verification phase, the write-vector is being re-setup [ so same seed and prandom_bytes_state() called ], and then memcmp()'ed against the read-vector to check if the data is the same. Akinobu, Lothar and I also tested this patch and it runs through the 3 relevant MTD test cases w/o any errors on the nandsim device (simulator for MTD devs) for x86_64, ppc64, ARM (i.MX28, i.MX53 and i.MX6): # modprobe nandsim first_id_byte=0x20 second_id_byte=0xac \ third_id_byte=0x00 fourth_id_byte=0x15 # modprobe mtd_oobtest dev=0 # modprobe mtd_pagetest dev=0 # modprobe mtd_subpagetest dev=0 We also don't have any users depending directly on a particular result of the PRNG (except the PRNG self-test itself), and that's just fine as it e.g. allowed us easily to do things like upgrading from taus88 to taus113. Signed-off-by: Daniel Borkmann Tested-by: Akinobu Mita Tested-by: Lothar Waßmann Cc: Hannes Frederic Sowa Signed-off-by: David S. Miller

random32: mix in entropy from core to late initcall

2014-07-30T20:55:27Z

Currently, we have a 3-stage seeding process in prandom(): Phase 1 is from the early actual initialization of prandom() subsystem which happens during core_initcall() and remains most likely until the beginning of late_initcall() phase. Here, the system might not have enough entropy available for seeding with strong randomness from the random driver. That means, we currently have a 32bit weak LCG() seeding the PRNG status register 1 and mixing that successively into the other 3 registers just to get it up and running. Phase 2 starts with late_initcall() phase resp. when the random driver has initialized its non-blocking pool with enough entropy. At that time, we throw away *all* inner state from its 4 registers and do a full reseed with strong randomness. Phase 3 starts right after that and does a periodic reseed with random slack of status register 1 by a strong random source again. A problem in phase 1 is that during bootup data structures can be initialized, e.g. on module load time, and thus access a weakly seeded prandom and are never changed for the rest of their live-time, thus carrying along the results from a week seed. Lets make sure that current but also future users access a possibly better early seeded prandom. This patch therefore improves phase 1 by trying to make it more 'unpredictable' through mixing in seed from a possible hardware source. Now, the mix-in xors inner state with the outcome of either of the two functions arch_get_random_{,seed}_int(), preferably arch_get_random_seed_int() as it likely represents a non-deterministic random bit generator in hw rather than a cryptographically secure PRNG in hw. However, not all might have the first one, so we use the PRNG as a fallback if available. As we xor the seed into the current state, the worst case would be that a hardware source could be unverifiable compromised or backdoored. In that case nevertheless it would be as good as our original early seeding function prandom_seed_very_weak() since we mix through xor which is entropy preserving. Joint work with Daniel Borkmann. Signed-off-by: Daniel Borkmann Signed-off-by: Hannes Frederic Sowa Signed-off-by: David S. Miller

lib/random32.c: minor cleanups and kdoc fix

2014-04-03T23:21:11Z

These are just some very minor and misc cleanups in the PRNG. In prandom_u32() we store the result in an unsigned long which is unnecessary as it should be u32 instead that we get from prandom_u32_state(). prandom_bytes_state()'s comment is in kdoc format, so change it into such as it's done everywhere else. Also, use the normal comment style for the header comment. Last but not least for readability, add some newlines. Signed-off-by: Daniel Borkmann Cc: Joe Perches Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

random32: avoid attempt to late reseed if in the middle of seeding

2014-03-28T20:04:19Z

Commit 4af712e8df ("random32: add prandom_reseed_late() and call when nonblocking pool becomes initialized") has added a late reseed stage that happens as soon as the nonblocking pool is marked as initialized. This fails in the case that the nonblocking pool gets initialized during __prandom_reseed()'s call to get_random_bytes(). In that case we'd double back into __prandom_reseed() in an attempt to do a late reseed - deadlocking on 'lock' early on in the boot process. Instead, just avoid even waiting to do a reseed if a reseed is already occuring. Fixes: 4af712e8df99 ("random32: add prandom_reseed_late() and call when nonblocking pool becomes initialized") Signed-off-by: Sasha Levin Acked-by: Hannes Frederic Sowa Signed-off-by: Daniel Borkmann Signed-off-by: David S. Miller

random32: use msecs_to_jiffies for reseed timer

2013-11-14T21:06:02Z

Use msecs_to_jiffies, for these calculations as different HZ considerations are taken into account for conversion of the timer shot, and also it makes the code more readable. Signed-off-by: Daniel Borkmann Signed-off-by: Hannes Frederic Sowa Signed-off-by: David S. Miller

random32: add __init prefix to prandom_start_seed_timer

2013-11-14T21:06:02Z

We only call that in functions annotated with __init, so add __init prefix in prandom_start_seed_timer() as well, so that the kernel can make use of this hint and we can possibly free up resources after it's usage. And since it's an internal function rename it to __prandom_start_seed_timer(). Signed-off-by: Daniel Borkmann Signed-off-by: Hannes Frederic Sowa Signed-off-by: David S. Miller

random32: add test cases for taus113 implementation

2013-11-11T19:32:15Z

We generated a battery of 100 test cases from GSL taus113 implemention and compare the results from a particular seed and a particular iteration with our implementation in the kernel. We have verified on 32 and 64 bit machines that our taus113 kernel implementation gives same results as GSL taus113 implementation: [ 0.147370] prandom: seed boundary self test passed [ 0.148078] prandom: 100 self tests passed This is a Kconfig option that is disabled on default, just like the crc32 init selftests in order to not unnecessary slow down boot process. We also refactored out prandom_seed_very_weak() as it's now used in multiple places in order to reduce redundant code. GSL code we used for generating test cases: int i, j; srand(time(NULL)); for (i = 0; i < 100; ++i) { int iteration = 500 + (rand() % 500); gsl_rng_default_seed = rand() + 1; gsl_rng *r = gsl_rng_alloc(gsl_rng_taus113); printf("\t{ %lu, ", gsl_rng_default_seed); for (j = 0; j < iteration - 1; ++j) gsl_rng_get(r); printf("%u, %lu },\n", iteration, gsl_rng_get(r)); gsl_rng_free(r); } Joint work with Hannes Frederic Sowa. Cc: Florian Weimer Cc: Theodore Ts'o Signed-off-by: Daniel Borkmann Signed-off-by: Hannes Frederic Sowa Signed-off-by: David S. Miller

random32: upgrade taus88 generator to taus113 from errata paper

2013-11-11T19:32:15Z

Since we use prandom*() functions quite often in networking code i.e. in UDP port selection, netfilter code, etc, upgrade the PRNG from Pierre L'Ecuyer's original paper "Maximally Equidistributed Combined Tausworthe Generators", Mathematics of Computation, 65, 213 (1996), 203--213 to the version published in his errata paper [1]. The Tausworthe generator is a maximally-equidistributed generator, that is fast and has good statistical properties [1]. The version presented there upgrades the 3 state LFSR to a 4 state LFSR with increased periodicity from about 2^88 to 2^113. The algorithm is presented in [1] by the very same author who also designed the original algorithm in [2]. Also, by increasing the state, we make it a bit harder for attackers to "guess" the PRNGs internal state. See also discussion in [3]. Now, as we use this sort of weak initialization discussed in [3] only between core_initcall() until late_initcall() time [*] for prandom32*() users, namely in prandom_init(), it is less relevant from late_initcall() onwards as we overwrite seeds through prandom_reseed() anyways with a seed source of higher entropy, that is, get_random_bytes(). In other words, a exhaustive keysearch of 96 bit would be needed. Now, with the help of this patch, this state-search increases further to 128 bit. Initialization needs to make sure that s1 > 1, s2 > 7, s3 > 15, s4 > 127. taus88 and taus113 algorithm is also part of GSL. I added a test case in the next patch to verify internal behaviour of this patch with GSL and ran tests with the dieharder 3.31.1 RNG test suite: $ dieharder -g 052 -a -m 10 -s 1 -S 4137730333 #taus88 $ dieharder -g 054 -a -m 10 -s 1 -S 4137730333 #taus113 With this seed configuration, in order to compare both, we get the following differences: algorithm taus88 taus113 rands/second [**] 1.61e+08 1.37e+08 sts_serial(4, 1st run) WEAK PASSED sts_serial(9, 2nd run) WEAK PASSED rgb_lagged_sum(31) WEAK PASSED We took out diehard_sums test as according to the authors it is considered broken and unusable [4]. Despite that and the slight decrease in performance (which is acceptable), taus113 here passes all 113 tests (only rgb_minimum_distance_5 in WEAK, the rest PASSED). In general, taus/taus113 is considered "very good" by the authors of dieharder [5]. The papers [1][2] states a single warm-up step is sufficient by running quicktaus once on each state to ensure proper initialization of ~s_{0}: Our selection of (s) according to Table 1 of [1] row 1 holds the condition L - k <= r - s, that is, (32 32 32 32) - (31 29 28 25) <= (25 27 15 22) - (18 2 7 13) with r = k - q and q = (6 2 13 3) as also stated by the paper. So according to [2] we are safe with one round of quicktaus for initialization. However we decided to include the warm-up phase of the PRNG as done in GSL in every case as a safety net. We also use the warm up phase to make the output of the RNG easier to verify by the GSL output. In prandom_init(), we also mix random_get_entropy() into it, just like drivers/char/random.c does it, jiffies ^ random_get_entropy(). random-get_entropy() is get_cycles(). xor is entropy preserving so it is fine if it is not implemented by some architectures. Note, this PRNG is *not* used for cryptography in the kernel, but rather as a fast PRNG for various randomizations i.e. in the networking code, or elsewhere for debugging purposes, for example. [*]: In order to generate some "sort of pseduo-randomness", since get_random_bytes() is not yet available for us, we use jiffies and initialize states s1 - s3 with a simple linear congruential generator (LCG), that is x <- x * 69069; and derive s2, s3, from the 32bit initialization from s1. So the above quote from [3] accounts only for the time from core to late initcall, not afterwards. [**] Single threaded run on MacBook Air w/ Intel Core i5-3317U [1] http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme2.ps [2] http://www.iro.umontreal.ca/~lecuyer/myftp/papers/tausme.ps [3] http://thread.gmane.org/gmane.comp.encryption.general/12103/ [4] http://code.google.com/p/dieharder/source/browse/trunk/libdieharder/diehard_sums.c?spec=svn490&r=490#20 [5] http://www.phy.duke.edu/~rgb/General/dieharder.php Joint work with Hannes Frederic Sowa. Cc: Florian Weimer Cc: Theodore Ts'o Signed-off-by: Daniel Borkmann Signed-off-by: Hannes Frederic Sowa Signed-off-by: David S. Miller