ares_parse_naptr_reply: check sufficient data

Check that there is enough data for the required elements
of an NAPTR record (2 int16, 3 bytes for string lengths)
before processing a record.

Bug: https://c-ares.haxx.se/adv_20170620.html
Link: https://c-ares.haxx.se/CVE-2017-1000381.patch
Change-Id: I16056280817af5cd7a62ddc366280c73391cbc6a
Signed-off-by: Nishant Chaprana <n.chaprana@samsung.com>

diff --git a/ares_parse_naptr_reply.c b/ares_parse_naptr_reply.c
index 0e37b02..6216ca7 100644 (file)
--- a/ares_parse_naptr_reply.c
+++ b/ares_parse_naptr_reply.c
@@ -110,6 +110,12 @@ ares_parse_naptr_reply (const unsigned char *abuf, int alen,
           status = ARES_EBADRESP;
           break;
         }
+      /* RR must contain at least 7 bytes = 2 x int16 + 3 x name */
+      if (rr_len < 7)
+        {
+          status = ARES_EBADRESP;
+          break;
+        }
 
       /* Check if we are really looking at a NAPTR record */
       if (rr_class == C_IN && rr_type == T_NAPTR)
@@ -192,4 +198,3 @@ ares_parse_naptr_reply (const unsigned char *abuf, int alen,
 
   return ARES_SUCCESS;
 }
-