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>
(cherry picked from commit a0eed48d37a4b7beea0c966caf09ad46f4a92a44)

diff --git a/crypto/asn1/a_int.c b/crypto/asn1/a_int.c
index 70c2b8e62c43565fd9dee4578dd62a3501121416..7e26704a5479ca4770b6b9836d5dd75c13203708 100644 (file)
--- 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)
     else {
         ret = a->length;
         i = a->data[0];
+        if (ret == 1 && i == 0)
+            neg = 0;
         if (!neg && (i > 127)) {
             pad = 1;
             pb = 0;
@@ -162,7 +164,7 @@ 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--;
@@ -419,7 +421,7 @@ 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;