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Merge #516: improvements to random seed in src/tests.c 

be40c4d Fixup for C90 mixed declarations. (Gregory Maxwell)
8b3841c fix bug in fread() failure check (Don Viszneki)
cddef0c tests: add warning message when /dev/urandom fails (Don Viszneki)

Pull request description:

  I've made two small changes to `src/tests.c` circa random seed generation.

  Added a warning when `/dev/urandom` fails, mostly to defend against the case that someone should use the code verbatim, but also to enhance its illustrative power.

  Also I fixed a bug with how the return value of `fread()` was being evaluated. In fact, `/dev/urandom` was never being applied before as the check on the return value of `fread()` always failed!

Tree-SHA512: 239dbe8316220c2f0e5b370bf9a18f78196e96cc4a7edea58cf2521b2c9cbc8da065be96aa859f90324d57e388d30f7670ce6bc1cca52e5162e5ca66b1a55b34
This commit is contained in:
Gregory Maxwell 2019-02-21 11:42:08 +00:00
parent 870a977644 be40c4d0b5
commit 20c5869df2
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1 changed files with 2 additions and 1 deletions
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src/tests.c
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@ -4994,8 +4994,9 @@ int main(int argc, char **argv) {
}
} else {
FILE *frand = fopen("/dev/urandom", "r");
if ((frand == NULL) || fread(&seed16, sizeof(seed16), 1, frand) != sizeof(seed16)) {
if ((frand == NULL) || fread(&seed16, 1, sizeof(seed16), frand) != sizeof(seed16)) {
uint64_t t = time(NULL) * (uint64_t)1337;
fprintf(stderr, "WARNING: could not read 16 bytes from /dev/urandom; falling back to insecure PRNG\n");
seed16[0] ^= t;
seed16[1] ^= t >> 8;
seed16[2] ^= t >> 16;