_asn1_ltostr: ensure that input value will always be printed

That is, use an unsigned type to store the output of the negation
(in case the input is negative).

This addresses the issue found in PKCS#7 decoding:
https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=388

Signed-off-by: Nikos Mavrogiannopoulos <nmav@redhat.com>

1 files changed, 11 insertions, 7 deletions

diff --git a/lib/parser_aux.c b/lib/parser_aux.c
index cfd76e0..7313eeb 100644
--- a/lib/parser_aux.c
+++ b/lib/parser_aux.c
@@ -551,29 +551,33 @@ _asn1_delete_list_and_nodes (void)
 char *
 _asn1_ltostr (int64_t v, char str[LTOSTR_MAX_SIZE])
 {
-  int64_t d, r;
+  uint64_t d, r;
   char temp[LTOSTR_MAX_SIZE];
   int count, k, start;
+  uint64_t val;
 
   if (v < 0)
     {
       str[0] = '-';
       start = 1;
-      v = -v;
+      val = -v;
     }
   else
-    start = 0;
+    {
+      val = v;
+      start = 0;
+    }
 
   count = 0;
   do
     {
-      d = v / 10;
-      r = v - d * 10;
+      d = val / 10;
+      r = val - d * 10;
       temp[start + count] = '0' + (char) r;
       count++;
-      v = d;
+      val = d;
     }
-  while (v && ((start+count) < LTOSTR_MAX_SIZE-1));
+  while (val && ((start+count) < LTOSTR_MAX_SIZE-1));
 
   for (k = 0; k < count; k++)
     str[k + start] = temp[start + count - k - 1];