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Handle BN_mod_word failures.

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As of 67cb49d045 and the corresponding upstream
change, BN_mod_word may fail, like BN_div_word. Handle this properly and
document in bn.h. Thanks to Brian Smith for pointing this out.

Change-Id: I6d4f32dc37bcabf70847c9a8b417d55d31b3a380
Reviewed-on: https://boringssl-review.googlesource.com/8491
Reviewed-by: Adam Langley <agl@google.com>
This commit is contained in:
David Benjamin 2016-06-23 16:05:02 -04:00 committed by Adam Langley
parent 53409ee3d7
commit 44bedc348d
4 changed files with 29 additions and 7 deletions
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2
crypto/bn/bn_test.cc
View File

@ -852,7 +852,7 @@ static bool test_div_word(FILE *fp) {
BN_ULONG s = b->d[0]; BN_ULONG s = b->d[0];
BN_ULONG rmod = BN_mod_word(b.get(), s); BN_ULONG rmod = BN_mod_word(b.get(), s);
BN_ULONG r = BN_div_word(b.get(), s); BN_ULONG r = BN_div_word(b.get(), s);
if (r == (BN_ULONG)-1) { if (r == (BN_ULONG)-1 || rmod == (BN_ULONG)-1) {
return false; return false;
} }

26
crypto/bn/prime.c
View File

@ -496,7 +496,11 @@ int BN_is_prime_fasttest_ex(const BIGNUM *a, int checks, BN_CTX *ctx_passed,
if (do_trial_division) { if (do_trial_division) {
for (i = 1; i < NUMPRIMES; i++) { for (i = 1; i < NUMPRIMES; i++) {
if (BN_mod_word(a, primes[i]) == 0) { BN_ULONG mod = BN_mod_word(a, primes[i]);
if (mod == (BN_ULONG)-1) {
goto err;
}
if (mod == 0) {
return 0; return 0;
} }
} }
@ -653,7 +657,11 @@ again:
/* we now have a random number 'rnd' to test. */ /* we now have a random number 'rnd' to test. */
for (i = 1; i < NUMPRIMES; i++) { for (i = 1; i < NUMPRIMES; i++) {
mods[i] = (uint16_t)BN_mod_word(rnd, (BN_ULONG)primes[i]); BN_ULONG mod = BN_mod_word(rnd, (BN_ULONG)primes[i]);
if (mod == (BN_ULONG)-1) {
return 0;
}
mods[i] = (uint16_t)mod;
} }
/* If bits is so small that it fits into a single word then we /* If bits is so small that it fits into a single word then we
* additionally don't want to exceed that many bits. */ * additionally don't want to exceed that many bits. */
@ -753,7 +761,11 @@ static int probable_prime_dh(BIGNUM *rnd, int bits, const BIGNUM *add,
loop: loop:
for (i = 1; i < NUMPRIMES; i++) { for (i = 1; i < NUMPRIMES; i++) {
/* check that rnd is a prime */ /* check that rnd is a prime */
if (BN_mod_word(rnd, (BN_ULONG)primes[i]) <= 1) { BN_ULONG mod = BN_mod_word(rnd, (BN_ULONG)primes[i]);
if (mod == (BN_ULONG)-1) {
goto err;
}
if (mod <= 1) {
if (!BN_add(rnd, rnd, add)) { if (!BN_add(rnd, rnd, add)) {
goto err; goto err;
} }
@ -825,8 +837,12 @@ loop:
/* check that p and q are prime */ /* check that p and q are prime */
/* check that for p and q /* check that for p and q
* gcd(p-1,primes) == 1 (except for 2) */ * gcd(p-1,primes) == 1 (except for 2) */
if ((BN_mod_word(p, (BN_ULONG)primes[i]) == 0) || BN_ULONG pmod = BN_mod_word(p, (BN_ULONG)primes[i]);
(BN_mod_word(q, (BN_ULONG)primes[i]) == 0)) { BN_ULONG qmod = BN_mod_word(q, (BN_ULONG)primes[i]);
if (pmod == (BN_ULONG)-1 || qmod == (BN_ULONG)-1) {
goto err;
}
if (pmod == 0 || qmod == 0) {
if (!BN_add(p, p, padd)) { if (!BN_add(p, p, padd)) {
goto err; goto err;
} }

6
crypto/dh/check.c
View File

@ -173,11 +173,17 @@ int DH_check(const DH *dh, int *ret) {
} }
} else if (BN_is_word(dh->g, DH_GENERATOR_2)) { } else if (BN_is_word(dh->g, DH_GENERATOR_2)) {
l = BN_mod_word(dh->p, 24); l = BN_mod_word(dh->p, 24);
if (l == (BN_ULONG)-1) {
goto err;
}
if (l != 11) { if (l != 11) {
*ret |= DH_CHECK_NOT_SUITABLE_GENERATOR; *ret |= DH_CHECK_NOT_SUITABLE_GENERATOR;
} }
} else if (BN_is_word(dh->g, DH_GENERATOR_5)) { } else if (BN_is_word(dh->g, DH_GENERATOR_5)) {
l = BN_mod_word(dh->p, 10); l = BN_mod_word(dh->p, 10);
if (l == (BN_ULONG)-1) {
goto err;
}
if (l != 3 && l != 7) { if (l != 3 && l != 7) {
*ret |= DH_CHECK_NOT_SUITABLE_GENERATOR; *ret |= DH_CHECK_NOT_SUITABLE_GENERATOR;
} }

2
include/openssl/bn.h
View File

@ -502,7 +502,7 @@ OPENSSL_EXPORT int BN_mask_bits(BIGNUM *a, int n);
/* Modulo arithmetic. */ /* Modulo arithmetic. */
/* BN_mod_word returns |a| mod |w|. */ /* BN_mod_word returns |a| mod |w| or (BN_ULONG)-1 on error. */
OPENSSL_EXPORT BN_ULONG BN_mod_word(const BIGNUM *a, BN_ULONG w); OPENSSL_EXPORT BN_ULONG BN_mod_word(const BIGNUM *a, BN_ULONG w);
/* BN_mod is a helper macro that calls |BN_div| and discards the quotient. */ /* BN_mod is a helper macro that calls |BN_div| and discards the quotient. */