make BN_is_prime() realise that 2 is, in fact, a prime number.

from OpenSSL CVS; ok otto@ deraadt@

2 files changed, 6 insertions, 2 deletions

diff --git a/src/lib/libcrypto/bn/bn_prime.c b/src/lib/libcrypto/bn/bn_prime.c
index e072d9255c..f422172f16 100644
--- a/src/lib/libcrypto/bn/bn_prime.c
+++ b/src/lib/libcrypto/bn/bn_prime.c
@@ -234,7 +234,9 @@ int BN_is_prime_fasttest(const BIGNUM *a, int checks,
 
         /* first look for small factors */
         if (!BN_is_odd(a))
-                return 0;
+                /* 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++)
diff --git a/src/lib/libssl/src/crypto/bn/bn_prime.c b/src/lib/libssl/src/crypto/bn/bn_prime.c
index e072d9255c..f422172f16 100644
--- a/src/lib/libssl/src/crypto/bn/bn_prime.c
+++ b/src/lib/libssl/src/crypto/bn/bn_prime.c
@@ -234,7 +234,9 @@ int BN_is_prime_fasttest(const BIGNUM *a, int checks,
 
         /* first look for small factors */
         if (!BN_is_odd(a))
-                return 0;
+                /* 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++)