Fix CVE-2017-10790:

https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-10790

Patch copied from upstream source repository:

https://git.savannah.nongnu.org/cgit/libtasn1.git/commit/?id=d8d805e1f2e6799bb2dff4871a8598dc83088a39

From d8d805e1f2e6799bb2dff4871a8598dc83088a39 Mon Sep 17 00:00:00 2001
From: Nikos Mavrogiannopoulos <nmav@redhat.com>
Date: Thu, 22 Jun 2017 16:31:37 +0200
Subject: [PATCH] _asn1_check_identifier: safer access to values read

Signed-off-by: Nikos Mavrogiannopoulos <nmav@redhat.com>
---
 lib/parser_aux.c | 17 ++++++++++++-----
 1 file changed, 12 insertions(+), 5 deletions(-)

diff --git a/lib/parser_aux.c b/lib/parser_aux.c
index 976ab38..786ea64 100644
--- a/lib/parser_aux.c
+++ b/lib/parser_aux.c
@@ -955,7 +955,7 @@ _asn1_check_identifier (asn1_node node)
 	  if (p2 == NULL)
 	    {
 	      if (p->value)
-		_asn1_strcpy (_asn1_identifierMissing, p->value);
+		_asn1_str_cpy (_asn1_identifierMissing, sizeof(_asn1_identifierMissing), (char*)p->value);
 	      else
 		_asn1_strcpy (_asn1_identifierMissing, "(null)");
 	      return ASN1_IDENTIFIER_NOT_FOUND;
@@ -968,9 +968,15 @@ _asn1_check_identifier (asn1_node node)
 	  if (p2 && (type_field (p2->type) == ASN1_ETYPE_DEFAULT))
 	    {
 	      _asn1_str_cpy (name2, sizeof (name2), node->name);
-	      _asn1_str_cat (name2, sizeof (name2), ".");
-	      _asn1_str_cat (name2, sizeof (name2), (char *) p2->value);
-	      _asn1_strcpy (_asn1_identifierMissing, p2->value);
+	      if (p2->value)
+	        {
+	          _asn1_str_cat (name2, sizeof (name2), ".");
+	          _asn1_str_cat (name2, sizeof (name2), (char *) p2->value);
+	          _asn1_str_cpy (_asn1_identifierMissing, sizeof(_asn1_identifierMissing), (char*)p2->value);
+	        }
+	      else
+		_asn1_strcpy (_asn1_identifierMissing, "(null)");
+
 	      p2 = asn1_find_node (node, name2);
 	      if (!p2 || (type_field (p2->type) != ASN1_ETYPE_OBJECT_ID) ||
 		  !(p2->type & CONST_ASSIGN))
@@ -990,7 +996,8 @@ _asn1_check_identifier (asn1_node node)
 		  _asn1_str_cpy (name2, sizeof (name2), node->name);
 		  _asn1_str_cat (name2, sizeof (name2), ".");
 		  _asn1_str_cat (name2, sizeof (name2), (char *) p2->value);
-		  _asn1_strcpy (_asn1_identifierMissing, p2->value);
+		  _asn1_str_cpy (_asn1_identifierMissing, sizeof(_asn1_identifierMissing), (char*)p2->value);
+
 		  p2 = asn1_find_node (node, name2);
 		  if (!p2 || (type_field (p2->type) != ASN1_ETYPE_OBJECT_ID)
 		      || !(p2->type & CONST_ASSIGN))
-- 
2.13.3

