Fix truncated dns-lookup return record handling

[exim.git] / src / src / dns.c

diff --git a/src/src/dns.c b/src/src/dns.c
index f19d23b4c1fda73c50a6cf8c688b3307920c6985..ad98a9d4e420003bf003f64c204bac1356b70ade 100644 (file)
--- a/src/src/dns.c
+++ b/src/src/dns.c
@@ -90,8 +90,7 @@ if (stat(CS utilname, &statbuf) >= 0)
   int infd, outfd, rc;
   uschar *argv[5];
 
-  DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) using fakens `%s'\n",
-    name, dns_text_type(type), utilname);
+  DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) using fakens\n", name, dns_text_type(type));
 
   argv[0] = utilname;
   argv[1] = config_main_directory;
@@ -113,6 +112,13 @@ if (stat(CS utilname, &statbuf) >= 0)
     asize -= rc;      /* may need to be passed on to res_search(). */
     }
 
+  /* If we ran out of output buffer before exhasting the return,
+  carry on reading and counting it. */
+
+  if (asize == 0)
+    while ((rc = read(outfd, name, sizeof(name))) > 0)
+      len += rc;
+
   if (rc < 0)
     log_write(0, LOG_MAIN|LOG_PANIC_DIE, "read from fakens failed: %s",
       strerror(errno));
@@ -1080,31 +1086,36 @@ Argument:
   dnsa       the DNS answer block
   rr         the RR
 
-Returns:     pointer to a chain of dns_address items
+Returns:     pointer to a chain of dns_address items; NULL when the dnsa was overrun
 */
 
 dns_address *
 dns_address_from_rr(dns_answer *dnsa, dns_record *rr)
 {
-dns_address *yield = NULL;
-
-dnsa = dnsa;    /* Stop picky compilers warning */
+dns_address * yield = NULL;
+uschar * dnsa_lim = dnsa->answer + dnsa->answerlen;
 
 if (rr->type == T_A)
   {
   uschar *p = US rr->data;
-  yield = store_get(sizeof(dns_address) + 20);
-  (void)sprintf(CS yield->address, "%d.%d.%d.%d", p[0], p[1], p[2], p[3]);
-  yield->next = NULL;
+  if (p + 4 <= dnsa_lim)
+    {
+    yield = store_get(sizeof(dns_address) + 20);
+    (void)sprintf(CS yield->address, "%d.%d.%d.%d", p[0], p[1], p[2], p[3]);
+    yield->next = NULL;
+    }
   }
 
 #if HAVE_IPV6
 
 else
   {
-  yield = store_get(sizeof(dns_address) + 50);
-  inet_ntop(AF_INET6, US rr->data, CS yield->address, 50);
-  yield->next = NULL;
+  if (rr->data + 16 <= dnsa_lim)
+    {
+    yield = store_get(sizeof(dns_address) + 50);
+    inet_ntop(AF_INET6, US rr->data, CS yield->address, 50);
+    yield->next = NULL;
+    }
   }
 #endif  /* HAVE_IPV6 */