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testsc: add random_advance_counter().

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In test_primegen, we loop round retrieving random data until we find
some that will permit a successful prime generation, so that we can
log only the successful attempts, and not the failures (which don't
have to be time-safe). But this itself introduces a potential mismatch
between logs, because the simplistic RNG used in testsc will have
different control flow depending on how far through a buffer of hash
data it is at the start of a given run.

random_advance_counter() gives it a fresh buffer, so calling that at
the start of a run should normalise this out. The code to do that was
already in the middle of random_read(); I've just pulled it out into a
separately callable function.

This hasn't _actually_ caused failures in test_primegen, but I'm not
sure why not. (Perhaps just luck.) But it did cause a failure in
another test of a similar nature, so before I commit _that_ test (and
the thing it's testing), I'd better fix this.
This commit is contained in:
Simon Tatham 2022-04-15 15:31:30 +01:00
parent 1500da80f1
commit 3adfb1aa5b
1 changed files with 13 additions and 8 deletions
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21
test/testsc.c
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@ -114,19 +114,23 @@ static void random_seed(const char *seedstr)
random_buf_limit = 0;
}
static void random_advance_counter(void)
{
ssh_hash_reset(random_hash);
put_asciz(random_hash, random_seedstr);
put_uint64(random_hash, random_counter);
random_counter++;
random_buf_limit = ssh_hash_alg(random_hash)->hlen;
ssh_hash_digest(random_hash, random_buf);
}
void random_read(void *vbuf, size_t size)
{
assert(random_seedstr);
uint8_t *buf = (uint8_t *)vbuf;
while (size-- > 0) {
if (random_buf_limit == 0) {
ssh_hash_reset(random_hash);
put_asciz(random_hash, random_seedstr);
put_uint64(random_hash, random_counter);
random_counter++;
random_buf_limit = ssh_hash_alg(random_hash)->hlen;
ssh_hash_digest(random_hash, random_buf);
}
if (random_buf_limit == 0)
random_advance_counter();
*buf++ = random_buf[random_buf_limit--];
}
}
@ -1514,6 +1518,7 @@ static void test_primegen(const PrimeGenerationPolicy *policy)
for (size_t i = 0; i < looplimit(2); i++) {
while (true) {
random_advance_counter();
struct random_state st = random_get_state();
PrimeCandidateSource *pcs = pcs_new(128);