commit 44bedc348d9491e63c7ed1438db100a4b8a830be
author David Benjamin <davidben@google.com> Thu Jun 23 16:05:02 2016 -0400
committer Adam Langley <agl@google.com> Thu Jun 23 21:25:18 2016 +0000
tree c80c3342b9c8d7234dfcabc264cdfa0aa18a5f70
parent 53409ee3d7595ed37da472bc73b010cd2c8a5ffd

Handle BN_mod_word failures.

As of 67cb49d045f04973ddba0f92fe8a8ad483c7da89 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>

crypto/dh/check.c

diff --git a/crypto/dh/check.c b/crypto/dh/check.c
index fbe58a5..ed1508f 100644
--- a/crypto/dh/check.c
+++ b/crypto/dh/check.c
@@ -173,11 +173,17 @@
     }
   } else 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_CHECK_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_CHECK_NOT_SUITABLE_GENERATOR;
     }