From: "Dr. Stephen Henson" <steve@openssl.org>
Date: Thu, 16 Apr 2015 16:43:09 +0100
Subject: [PATCH] Fix encoding bug in i2c_ASN1_INTEGER

Fix bug where i2c_ASN1_INTEGER mishandles zero if it is marked as
negative.

Thanks to Huzaifa Sidhpurwala <huzaifas@redhat.com> and
Hanno Böck <hanno@hboeck.de> for reporting this issue.

Reviewed-by: Rich Salz <rsalz@openssl.org>

---
 crypto/asn1/a_int.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/crypto/asn1/a_int.c b/crypto/asn1/a_int.c
index ad0d250..6574260 100644
--- a/crypto/asn1/a_int.c
+++ b/crypto/asn1/a_int.c
@@ -124,6 +124,8 @@ int i2c_ASN1_INTEGER(ASN1_INTEGER *a, unsigned char **pp)
 		{
 		ret=a->length;
 		i=a->data[0];
+		if (ret == 1 && i == 0)
+			neg = 0;
 		if (!neg && (i > 127)) {
 			pad=1;
 			pb=0;
@@ -157,7 +159,7 @@ int i2c_ASN1_INTEGER(ASN1_INTEGER *a, unsigned char **pp)
 		p += a->length - 1;
 		i = a->length;
 		/* Copy zeros to destination as long as source is zero */
-		while(!*n) {
+		while(!*n && i > 1) {
 			*(p--) = 0;
 			n--;
 			i--;
@@ -415,7 +417,7 @@ ASN1_INTEGER *BN_to_ASN1_INTEGER(const BIGNUM *bn, ASN1_INTEGER *ai)
 		ASN1err(ASN1_F_BN_TO_ASN1_INTEGER,ERR_R_NESTED_ASN1_ERROR);
 		goto err;
 		}
-	if (BN_is_negative(bn))
+	if (BN_is_negative(bn) && !BN_is_zero(bn))
 		ret->type = V_ASN1_NEG_INTEGER;
 	else ret->type=V_ASN1_INTEGER;
 	j=BN_num_bits(bn);
-- 
2.8.0.rc3.226.g39d4020