Bug fix: BN_is_prime() would fail with a high probability for small

primes (negligible for larger ones).

diff --git a/crypto/bn/bn_prime.c b/crypto/bn/bn_prime.c
index e2cfef37259eaad2612b0b874ca56367d19f0bcd..f6de801263cc410974cffcc7ba313945aaef6a5c 100644 (file)
--- a/crypto/bn/bn_prime.c
+++ b/crypto/bn/bn_prime.c
@@ -204,6 +204,7 @@ int BN_is_prime_fasttest(BIGNUM *a, int checks,
                if (!BN_pseudo_rand(check,BN_num_bits(a),0,0)) goto err;
                if (BN_cmp(check, a) >= 0)
                        BN_sub(check, check, a);
                if (!BN_pseudo_rand(check,BN_num_bits(a),0,0)) goto err;
                if (BN_cmp(check, a) >= 0)
                        BN_sub(check, check, a);

+               if (BN_is_zero(check)) BN_one(check);

                j=witness(check,a,ctx,ctx2,mont);
                if (j == -1) goto err;
                if (j)
                j=witness(check,a,ctx,ctx2,mont);
                if (j == -1) goto err;
                if (j)