Check the return from BN_sub() in BN_X931_generate_Xpq().

Reviewed-by: Tim Hudson <tjh@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/7088)

(cherry picked from commit 6bcfcf16bf6aef4f9ec267d8b86ae1bffd8deab9)

diff --git a/crypto/bn/bn_x931p.c b/crypto/bn/bn_x931p.c
index f444af3feabd91802e4c797803a2c12ee13bf1ae..116620a1384424306e3dda1e29c34e9c8c514b23 100644 (file)
--- a/crypto/bn/bn_x931p.c
+++ b/crypto/bn/bn_x931p.c
@@ -223,8 +223,10 @@ int BN_X931_generate_Xpq(BIGNUM *Xp, BIGNUM *Xq, int nbits, BN_CTX *ctx)
     for (i = 0; i < 1000; i++) {
         if (!BN_rand(Xq, nbits, 1, 0))
             goto err;
+
         /* Check that |Xp - Xq| > 2^(nbits - 100) */
-        BN_sub(t, Xp, Xq);
+        if (!BN_sub(t, Xp, Xq))
+            goto err;
         if (BN_num_bits(t) > (nbits - 100))
             break;
     }