DANE: ignore undersized TLSA records

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

diff --git a/src/src/dns.c b/src/src/dns.c
index 48924dc41344168d930e0d8f82a6b91ec2079b6d..297b8b88da7f253be56807459cb5d9e38c4c14e2 100644 (file)
--- a/src/src/dns.c
+++ b/src/src/dns.c
@@ -2,7 +2,7 @@
 *     Exim - an Internet mail transport agent    *
 *************************************************/
 
-/* Copyright (c) University of Cambridge 1995 - 2017 */
+/* Copyright (c) University of Cambridge 1995 - 2018 */
 /* See the file NOTICE for conditions of use and distribution. */
 
 /* Functions for interfacing with the DNS. */
@@ -674,10 +674,10 @@ if ((previous = tree_search(tree_dns_fails, node_name)))
   {
   DEBUG(D_dns) debug_printf("DNS lookup of %.255s-%s: using cached value %s\n",
     name, dns_text_type(type),
-      (previous->data.val == DNS_NOMATCH)? "DNS_NOMATCH" :
-      (previous->data.val == DNS_NODATA)? "DNS_NODATA" :
-      (previous->data.val == DNS_AGAIN)? "DNS_AGAIN" :
-      (previous->data.val == DNS_FAIL)? "DNS_FAIL" : "??");
+      previous->data.val == DNS_NOMATCH ? "DNS_NOMATCH" :
+      previous->data.val == DNS_NODATA ? "DNS_NODATA" :
+      previous->data.val == DNS_AGAIN ? "DNS_AGAIN" :
+      previous->data.val == DNS_FAIL ? "DNS_FAIL" : "??");
   return previous->data.val;
   }
 
@@ -693,7 +693,7 @@ if ((previous = tree_search(tree_dns_fails, node_name)))
     DEBUG(D_dns)
       debug_printf("DNS name '%s' utf8 conversion to alabel failed: %s\n", name,
         errstr);
-    host_find_failed_syntax = TRUE;
+    f.host_find_failed_syntax = TRUE;
     return DNS_NOMATCH;
     }
   name = alabel;
@@ -738,7 +738,7 @@ if (check_dns_names_pattern[0] != 0 && type != T_PTR && type != T_TXT)
     DEBUG(D_dns)
       debug_printf("DNS name syntax check failed: %s (%s)\n", name,
         dns_text_type(type));
-    host_find_failed_syntax = TRUE;
+    f.host_find_failed_syntax = TRUE;
     return DNS_NOMATCH;
     }
   }
@@ -761,7 +761,7 @@ if ((type == T_A || type == T_AAAA) && string_is_ip_address(name, NULL) != 0)
 (res_search), we call fakens_search(), which recognizes certain special
 domains, and interfaces to a fake nameserver for certain special zones. */
 
-dnsa->answerlen = running_in_test_harness
+dnsa->answerlen = f.running_in_test_harness
   ? fakens_search(name, type, dnsa->answer, sizeof(dnsa->answer))
   : res_search(CCS name, C_IN, type, dnsa->answer, sizeof(dnsa->answer));
 
@@ -836,6 +836,8 @@ return DNS_SUCCEED;
 /* Look up the given domain name, using the given type. Follow CNAMEs if
 necessary, but only so many times. There aren't supposed to be CNAME chains in
 the DNS, but you are supposed to cope with them if you find them.
+By default, follow one CNAME since a resolver has been seen, faced with
+an MX request and a CNAME (to an A) but no MX present, returning the CNAME.
 
 The assumption is made that if the resolver gives back records of the
 requested type *and* a CNAME, we don't need to make another call to look up
@@ -871,14 +873,19 @@ int i;
 const uschar *orig_name = name;
 BOOL secure_so_far = TRUE;
 
-/* Loop to follow CNAME chains so far, but no further... */
+/* By default, assume the resolver follows CNAME chains (and returns NODATA for
+an unterminated one). If it also does that for a CNAME loop, fine; if it returns
+a CNAME (maybe the last?) whine about it.  However, retain the coding for dumb
+resolvers hiding behind a config variable. Loop to follow CNAME chains so far,
+but no further...  The testsuite tests the latter case, mostly assuming that the
+former will work. */
 
-for (i = 0; i < 10; i++)
+for (i = 0; i <= dns_cname_loops; i++)
   {
   uschar * data;
   dns_record *rr, cname_rr, type_rr;
   dns_scan dnss;
-  int datalen, rc;
+  int rc;
 
   /* DNS lookup failures get passed straight back. */
 
@@ -940,8 +947,8 @@ for (i = 0; i < 10; i++)
     return DNS_FAIL;
 
   data = store_get(256);
-  if ((datalen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen,
-    cname_rr.data, (DN_EXPAND_ARG4_TYPE)data, 256)) < 0)
+  if (dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen,
+      cname_rr.data, (DN_EXPAND_ARG4_TYPE)data, 256) < 0)
     return DNS_FAIL;
   name = data;