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FROMLIST: crypto: testmgr - generate power-of-2 lengths more often

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Implementations of hash functions often have special cases when lengths
are a multiple of the hash function's internal block size (e.g. 64 for
SHA-256, 128 for SHA-512).  Currently, when the fuzz testing code
generates lengths, it doesn't prefer any length mod 64 over any other.
This limits the coverage of these special cases.

Therefore, this patch updates the fuzz testing code to generate
power-of-2 lengths and divide messages exactly in half a bit more often.

Reviewed-by: Sami Tolvanen <samitolvanen@google.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>

Bug: 330611177
Link: https://lore.kernel.org/r/20240621165922.77672-3-ebiggers@kernel.org
Change-Id: I76425c0136cf3beb161855cb77ec383ece1545db
Signed-off-by: Eric Biggers <ebiggers@google.com>
This commit is contained in:
Eric Biggers 2024-06-21 10:37:47 -07:00 committed by William McVicker
parent 614beb21b3
commit 17f53e8a94
1 changed files with 12 additions and 4 deletions
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16
crypto/testmgr.c
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@ -905,14 +905,20 @@ static unsigned int generate_random_length(struct rnd_state *rng,
switch (prandom_u32_below(rng, 4)) {
case 0:
return len % 64;
len %= 64;
break;
case 1:
return len % 256;
len %= 256;
break;
case 2:
return len % 1024;
len %= 1024;
break;
default:
return len;
break;
}
if (len && prandom_u32_below(rng, 4) == 0)
len = rounddown_pow_of_two(len);
return len;
}
/* Flip a random bit in the given nonempty data buffer */
@ -1008,6 +1014,8 @@ static char *generate_random_sgl_divisions(struct rnd_state *rng,
if (div == &divs[max_divs - 1] || prandom_bool(rng))
this_len = remaining;
else if (prandom_u32_below(rng, 4) == 0)
this_len = (remaining + 1) / 2;
else
this_len = prandom_u32_inclusive(rng, 1, remaining);
div->proportion_of_total = this_len;