BN does support negative-zero -- BN_print() sets the standard here.

BN_bn2hex() had a 1-byte overflow when creating "-0\0".  Reported to
me a while back by unknown person -- did not have enough experience
to push this through then.
advice from jsing, ok miod

2 files changed, 6 insertions, 6 deletions

diff --git a/src/lib/libcrypto/bn/bn_print.c b/src/lib/libcrypto/bn/bn_print.c
index 4920705a5b..6b9f82caaf 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 1.23 2014/07/12 16:03:36 miod Exp $ */
+/* $OpenBSD: bn_print.c,v 1.24 2015/09/13 15:59:29 deraadt Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -77,13 +77,13 @@ BN_bn2hex(const BIGNUM *a)
         char *buf;
         char *p;
 
-        buf = malloc(a->top * BN_BYTES * 2 + 2);
+        buf = malloc(BN_is_negative(a) + a->top * BN_BYTES * 2 + 2);
         if (buf == NULL) {
                 BNerr(BN_F_BN_BN2HEX, ERR_R_MALLOC_FAILURE);
                 goto err;
         }
         p = buf;
-        if (a->neg)
+        if (BN_is_negative(a))
                 *(p++) = '-';
         if (BN_is_zero(a))
                 *(p++) = '0';
diff --git a/src/lib/libssl/src/crypto/bn/bn_print.c b/src/lib/libssl/src/crypto/bn/bn_print.c
index 4920705a5b..6b9f82caaf 100644
--- a/src/lib/libssl/src/crypto/bn/bn_print.c
+++ b/src/lib/libssl/src/crypto/bn/bn_print.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: bn_print.c,v 1.23 2014/07/12 16:03:36 miod Exp $ */
+/* $OpenBSD: bn_print.c,v 1.24 2015/09/13 15:59:29 deraadt Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -77,13 +77,13 @@ BN_bn2hex(const BIGNUM *a)
         char *buf;
         char *p;
 
-        buf = malloc(a->top * BN_BYTES * 2 + 2);
+        buf = malloc(BN_is_negative(a) + a->top * BN_BYTES * 2 + 2);
         if (buf == NULL) {
                 BNerr(BN_F_BN_BN2HEX, ERR_R_MALLOC_FAILURE);
                 goto err;
         }
         p = buf;
-        if (a->neg)
+        if (BN_is_negative(a))
                 *(p++) = '-';
         if (BN_is_zero(a))
                 *(p++) = '0';