If BN_div_word() fails (by returning (BN_ULONG)-1) or if the division

fails to reduce the input in the expected space then fail out instead
of overflowing the allocated buffer.

combines openssl commits 28a89639da50b1caed4ff3015508f23173bf3e49 and
3612ff6fcec0e3d1f2a598135fe12177c0419582

ok doug@ beck@

1 files changed, 8 insertions, 4 deletions

diff --git a/src/lib/libcrypto/bn/bn_print.c b/src/lib/libcrypto/bn/bn_print.c
index 2c1681a2c0..f526065592 100644
--- a/src/lib/libcrypto/bn/bn_print.c
+++ b/src/lib/libcrypto/bn/bn_print.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: bn_print.c,v 1.29 2016/03/02 06:16:11 doug Exp $ */
+/* $OpenBSD: bn_print.c,v 1.30 2016/10/17 03:30:14 guenther Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -109,7 +109,7 @@ err:
 char *
 BN_bn2dec(const BIGNUM *a)
 {
-        int i = 0, num, ok = 0;
+        int i = 0, num, bn_data_num, ok = 0;
         char *buf = NULL;
         char *p;
         BIGNUM *t = NULL;
@@ -136,7 +136,8 @@ BN_bn2dec(const BIGNUM *a)
          */
         i = BN_num_bits(a) * 3;
         num = (i / 10 + i / 1000 + 1) + 1;
-        bn_data = reallocarray(NULL, num / BN_DEC_NUM + 1, sizeof(BN_ULONG));
+        bn_data_num = num / BN_DEC_NUM + 1;
+        bn_data = reallocarray(NULL, bn_data_num, sizeof(BN_ULONG));
         buf = malloc(num + 3);
         if ((buf == NULL) || (bn_data == NULL)) {
                 BNerr(BN_F_BN_BN2DEC, ERR_R_MALLOC_FAILURE);
@@ -151,9 +152,12 @@ BN_bn2dec(const BIGNUM *a)
         if (BN_is_negative(t))
                 *p++ = '-';
 
-        i = 0;
         while (!BN_is_zero(t)) {
+                if (lp - bn_data >= bn_data_num)
+                        goto err;
                 *lp = BN_div_word(t, BN_DEC_CONV);
+                if (*lp == (BN_ULONG)-1)
+                        goto err;
                 lp++;
         }
         lp--;