I copied some of the commit text here from BoringSSL, but it's wrong for LibreSSL it seems.
BN_ULLONG is not defined on all 64-bit systems as far as I can tell. So, this fix is more widely applicable than Win64 for LibreSSL. Any comments? - Brent > On Jun 30, 2016, at 8:40 AM, Brent Cook <bust...@gmail.com> wrote: > > On systems where we do not have BN_ULLONG (notably Win64), BN_mod_word() > can return incorrect results if the supplied modulus is too big. > > Note now that BN_mod_word may fail, like BN_div_word. Handle this > properly and document in the man page. > > Thanks to Brian Smith for pointing out these fixes from BoringSSL: > > https://boringssl.googlesource.com/boringssl/+/67cb49d045f04973ddba0f92fe8a8ad483c7da89 > https://boringssl.googlesource.com/boringssl/+/44bedc348d9491e63c7ed1438db100a4b8a830be > > diff --git a/src/lib/libcrypto/man/BN_add_word.3 > b/src/lib/libcrypto/man/BN_add_word.3 > index eb5874a..66fdc0a 100644 > --- a/src/lib/libcrypto/man/BN_add_word.3 > +++ b/src/lib/libcrypto/man/BN_add_word.3 > @@ -75,7 +75,8 @@ returns the remainder of > .Fa a > divided by > .Fa w > -.Pq Li a%w . > +.Pq Li a%w > +or (BN_ULONG)-1 on error. > .Pp > For > .Fn BN_div_word > diff --git a/src/lib/libssl/src/crypto/bn/bn_prime.c > b/src/lib/libssl/src/crypto/bn/bn_prime.c > index 09af6a1..1dd0153 100644 > --- a/src/lib/libssl/src/crypto/bn/bn_prime.c > +++ b/src/lib/libssl/src/crypto/bn/bn_prime.c > @@ -277,9 +277,13 @@ BN_is_prime_fasttest_ex(const BIGNUM *a, int checks, > BN_CTX *ctx_passed, > /* a is even => a is prime if and only if a == 2 */ > return BN_is_word(a, 2); > if (do_trial_division) { > - for (i = 1; i < NUMPRIMES; i++) > - if (BN_mod_word(a, primes[i]) == 0) > + for (i = 1; i < NUMPRIMES; i++) { > + BN_ULONG mod = BN_mod_word(a, primes[i]); > + if (mod == (BN_ULONG)-1) > + goto err; > + if (mod == 0) > return 0; > + } > if (!BN_GENCB_call(cb, 1, -1)) > goto err; > } > @@ -398,8 +402,12 @@ again: > if (!BN_rand(rnd, bits, 1, 1)) > return (0); > /* we now have a random number 'rand' to test. */ > - for (i = 1; i < NUMPRIMES; i++) > - mods[i] = (prime_t)BN_mod_word(rnd, (BN_ULONG)primes[i]); > + for (i = 1; i < NUMPRIMES; i++) { > + BN_ULONG mod = BN_mod_word(rnd, (BN_ULONG)primes[i]); > + if (mod == (BN_ULONG)-1) > + return (0); > + mods[i] = (prime_t)mod; > + } > maxdelta = BN_MASK2 - primes[NUMPRIMES - 1]; > delta = 0; > loop: > @@ -452,7 +460,10 @@ probable_prime_dh(BIGNUM *rnd, int bits, const BIGNUM > *add, const BIGNUM *rem, > loop: > for (i = 1; i < NUMPRIMES; i++) { > /* check that rnd is a prime */ > - if (BN_mod_word(rnd, (BN_ULONG)primes[i]) <= 1) { > + BN_LONG 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)) > goto err; > goto loop; > @@ -514,8 +525,11 @@ loop: > /* check that p and q are prime */ > /* check that for p and q > * gcd(p-1,primes) == 1 (except for 2) */ > - if ((BN_mod_word(p, (BN_ULONG)primes[i]) == 0) || > - (BN_mod_word(q, (BN_ULONG)primes[i]) == 0)) { > + BN_ULONG pmod = BN_mod_word(p, (BN_ULONG)primes[i]); > + 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)) > goto err; > if (!BN_add(q, q, qadd)) > diff --git a/src/lib/libssl/src/crypto/bn/bn_word.c > b/src/lib/libssl/src/crypto/bn/bn_word.c > index 897b06d..acc7032 100644 > --- a/src/lib/libssl/src/crypto/bn/bn_word.c > +++ b/src/lib/libssl/src/crypto/bn/bn_word.c > @@ -73,6 +73,20 @@ BN_mod_word(const BIGNUM *a, BN_ULONG w) > if (w == 0) > return (BN_ULONG) - 1; > > +#ifndef BN_ULLONG > + /* If |w| is too long and we don't have |BN_ULLONG| then we need to > fall back > + * to using |BN_div_word|. */ > + if (w > ((BN_ULONG)1 << BN_BITS4)) { > + BIGNUM *tmp = BN_dup(a); > + if (tmp == NULL) { > + return (BN_ULONG)-1; > + } > + ret = BN_div_word(tmp, w); > + BN_free(tmp); > + return ret; > + } > +#endif > + > bn_check_top(a); > w &= BN_MASK2; > for (i = a->top - 1; i >= 0; i--) { > diff --git a/src/lib/libssl/src/crypto/dh/dh_check.c > b/src/lib/libssl/src/crypto/dh/dh_check.c > index ad827dd..c34511d 100644 > --- a/src/lib/libssl/src/crypto/dh/dh_check.c > +++ b/src/lib/libssl/src/crypto/dh/dh_check.c > @@ -89,10 +89,14 @@ DH_check(const DH *dh, int *ret) > > if (BN_is_word(dh->g, DH_GENERATOR_2)) { > l = BN_mod_word(dh->p, 24); > + if (l == (BN_ULONG)-1) > + goto err; > if (l != 11) > *ret |= DH_NOT_SUITABLE_GENERATOR; > } else if (BN_is_word(dh->g, DH_GENERATOR_5)) { > l = BN_mod_word(dh->p, 10); > + if (l == (BN_ULONG)-1) > + goto err; > if (l != 3 && l != 7) > *ret |= DH_NOT_SUITABLE_GENERATOR; > } else > diff --git a/src/regress/lib/libcrypto/bn/general/bntest.c > b/src/regress/lib/libcrypto/bn/general/bntest.c > index c6bd788..1d54177 100644 > --- a/src/regress/lib/libcrypto/bn/general/bntest.c > +++ b/src/regress/lib/libcrypto/bn/general/bntest.c > @@ -514,7 +514,7 @@ int > test_div_word(BIO *bp) > { > BIGNUM a, b; > - BN_ULONG r, s; > + BN_ULONG r, rmod, s; > int i; > int rc = 1; > > @@ -523,14 +523,34 @@ test_div_word(BIO *bp) > > for (i = 0; i < num0; i++) { > do { > - BN_bntest_rand(&a, 512, -1, 0); > - BN_bntest_rand(&b, BN_BITS2, -1, 0); > + if (!BN_bntest_rand(&a, 512, -1, 0) || > + !BN_bntest_rand(&b, BN_BITS2, -1, 0)) { > + rc = 0; > + break; > + } > s = b.d[0]; > } while (!s); > > - BN_copy(&b, &a); > + if (!BN_copy(&b, &a)) { > + rc = 0; > + break; > + } > + > + s = b.d[0]; > + rmod = BN_mod_word(&b, s); > r = BN_div_word(&b, s); > > + if (r == (BN_ULONG)-1 || rmod == (BN_ULONG)-1) { > + rc = 0; > + break; > + } > + > + if (rmod != r) { > + fprintf(stderr, "Mod (word) test failed!\n"); > + rc = 0; > + break; > + } > + > if (bp != NULL) { > if (!results) { > BN_print(bp, &a);
