constification

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

diff --git a/src/src/dns.c b/src/src/dns.c
index b2a9c7ba4813d60c214c89a2c5369340301a013d..79eb9360e0b1a11120dbffdf2ac43e48be8ae487 100644 (file)
--- a/src/src/dns.c
+++ b/src/src/dns.c
@@ -1,10 +1,8 @@
-/* $Cambridge: exim/src/src/dns.c,v 1.12 2005/10/04 08:54:33 ph10 Exp $ */
-

 /*************************************************
 *     Exim - an Internet mail transport agent    *
 *************************************************/
 
 /*************************************************
 *     Exim - an Internet mail transport agent    *
 *************************************************/
 

-/* Copyright (c) University of Cambridge 1995 - 2005 */
+/* Copyright (c) University of Cambridge 1995 - 2014 */

 /* See the file NOTICE for conditions of use and distribution. */
 
 /* Functions for interfacing with the DNS. */
 /* See the file NOTICE for conditions of use and distribution. */
 
 /* Functions for interfacing with the DNS. */


@@ -48,7 +46,7 @@ Returns:      length of returned data, or -1 on error (h_errno set)
 */
 
 static int
 */
 
 static int

-fakens_search(uschar *domain, int type, uschar *answerptr, int size)
+fakens_search(const uschar *domain, int type, uschar *answerptr, int size)

 {
 int len = Ustrlen(domain);
 int asize = size;                  /* Locally modified */
 {
 int len = Ustrlen(domain);
 int asize = size;                  /* Locally modified */


@@ -161,25 +159,85 @@ the first time we have been here, and set the resolver options.
 Arguments:
   qualify_single    TRUE to set the RES_DEFNAMES option
   search_parents    TRUE to set the RES_DNSRCH option
 Arguments:
   qualify_single    TRUE to set the RES_DEFNAMES option
   search_parents    TRUE to set the RES_DNSRCH option

+  use_dnssec        TRUE to set the RES_USE_DNSSEC option

 
 Returns:            nothing
 */
 
 void
 
 Returns:            nothing
 */
 
 void

-dns_init(BOOL qualify_single, BOOL search_parents)
+dns_init(BOOL qualify_single, BOOL search_parents, BOOL use_dnssec)

 {
 {

-if ((_res.options & RES_INIT) == 0)
+res_state resp = os_get_dns_resolver_res();
+
+if ((resp->options & RES_INIT) == 0)

   {
   {

-  DEBUG(D_resolver) _res.options |= RES_DEBUG;     /* For Cygwin */
+  DEBUG(D_resolver) resp->options |= RES_DEBUG;     /* For Cygwin */
+  os_put_dns_resolver_res(resp);

   res_init();
   res_init();

-  DEBUG(D_resolver) _res.options |= RES_DEBUG;
+  DEBUG(D_resolver) resp->options |= RES_DEBUG;
+  os_put_dns_resolver_res(resp);

   }
 
   }
 

-_res.options &= ~(RES_DNSRCH | RES_DEFNAMES);
-_res.options |= (qualify_single? RES_DEFNAMES : 0) |
+resp->options &= ~(RES_DNSRCH | RES_DEFNAMES);
+resp->options |= (qualify_single? RES_DEFNAMES : 0) |

                 (search_parents? RES_DNSRCH : 0);
                 (search_parents? RES_DNSRCH : 0);

-if (dns_retrans > 0) _res.retrans = dns_retrans;
-if (dns_retry > 0) _res.retry = dns_retry;
+if (dns_retrans > 0) resp->retrans = dns_retrans;
+if (dns_retry > 0) resp->retry = dns_retry;
+
+#ifdef RES_USE_EDNS0
+if (dns_use_edns0 >= 0)
+  {
+  if (dns_use_edns0)
+    resp->options |= RES_USE_EDNS0;
+  else
+    resp->options &= ~RES_USE_EDNS0;
+  DEBUG(D_resolver)
+    debug_printf("Coerced resolver EDNS0 support %s.\n",
+        dns_use_edns0 ? "on" : "off");
+  }
+#else
+if (dns_use_edns0 >= 0)
+  DEBUG(D_resolver)
+    debug_printf("Unable to %sset EDNS0 without resolver support.\n",
+        dns_use_edns0 ? "" : "un");
+#endif
+
+#ifndef DISABLE_DNSSEC
+# ifdef RES_USE_DNSSEC
+#  ifndef RES_USE_EDNS0
+#   error Have RES_USE_DNSSEC but not RES_USE_EDNS0?  Something hinky ...
+#  endif
+if (use_dnssec)
+  resp->options |= RES_USE_DNSSEC;
+if (dns_dnssec_ok >= 0)
+  {
+  if (dns_use_edns0 == 0 && dns_dnssec_ok != 0)
+    {
+    DEBUG(D_resolver)
+      debug_printf("CONFLICT: dns_use_edns0 forced false, dns_dnssec_ok forced true, ignoring latter!\n");
+    }
+  else
+    {
+    if (dns_dnssec_ok)
+      resp->options |= RES_USE_DNSSEC;
+    else
+      resp->options &= ~RES_USE_DNSSEC;
+    DEBUG(D_resolver) debug_printf("Coerced resolver DNSSEC support %s.\n",
+        dns_dnssec_ok ? "on" : "off");
+    }
+  }
+# else
+if (dns_dnssec_ok >= 0)
+  DEBUG(D_resolver)
+    debug_printf("Unable to %sset DNSSEC without resolver support.\n",
+        dns_dnssec_ok ? "" : "un");
+if (use_dnssec)
+  DEBUG(D_resolver)
+    debug_printf("Unable to set DNSSEC without resolver support.\n");
+# endif
+#endif /* DISABLE_DNSSEC */
+
+os_put_dns_resolver_res(resp);

 }
 
 
 }
 
 


@@ -199,9 +257,9 @@ Returns:     nothing
 */
 
 void
 */
 
 void

-dns_build_reverse(uschar *string, uschar *buffer)
+dns_build_reverse(const uschar *string, uschar *buffer)

 {
 {

-uschar *p = string + Ustrlen(string);
+const uschar *p = string + Ustrlen(string);

 uschar *pp = buffer;
 
 /* Handle IPv4 address */
 uschar *pp = buffer;
 
 /* Handle IPv4 address */


@@ -213,7 +271,7 @@ if (Ustrchr(string, ':') == NULL)
   int i;
   for (i = 0; i < 4; i++)
     {
   int i;
   for (i = 0; i < 4; i++)
     {

-    uschar *ppp = p;
+    const uschar *ppp = p;

     while (ppp > string && ppp[-1] != '.') ppp--;
     Ustrncpy(pp, ppp, p - ppp);
     pp += p - ppp;
     while (ppp > string && ppp[-1] != '.') ppp--;
     Ustrncpy(pp, ppp, p - ppp);
     pp += p - ppp;


@@ -372,6 +430,41 @@ return &(dnss->srr);
 
 
 
 
 
 

+/*************************************************
+*    Return whether AD bit set in DNS result     *
+*************************************************/
+
+/* We do not perform DNSSEC work ourselves; if the administrator has installed
+a verifying resolver which sets AD as appropriate, though, we'll use that.
+(AD = Authentic Data)
+
+Argument:   pointer to dns answer block
+Returns:    bool indicating presence of AD bit
+*/
+
+BOOL
+dns_is_secure(const dns_answer * dnsa)
+{
+#ifdef DISABLE_DNSSEC
+DEBUG(D_dns)
+  debug_printf("DNSSEC support disabled at build-time; dns_is_secure() false\n");
+return FALSE;
+#else
+HEADER *h = (HEADER *)dnsa->answer;
+return h->ad ? TRUE : FALSE;
+#endif
+}
+
+static void
+dns_set_insecure(dns_answer * dnsa)
+{
+HEADER * h = (HEADER *)dnsa->answer;
+h->ad = 0;
+}
+
+
+
+

 /*************************************************
 *            Turn DNS type into text             *
 *************************************************/
 /*************************************************
 *            Turn DNS type into text             *
 *************************************************/


@@ -393,11 +486,13 @@ switch(t)
   case T_AAAA:  return US"AAAA";
   case T_A6:    return US"A6";
   case T_TXT:   return US"TXT";
   case T_AAAA:  return US"AAAA";
   case T_A6:    return US"A6";
   case T_TXT:   return US"TXT";

+  case T_SPF:   return US"SPF";

   case T_PTR:   return US"PTR";
   case T_SOA:   return US"SOA";
   case T_SRV:   return US"SRV";
   case T_NS:    return US"NS";
   case T_CNAME: return US"CNAME";
   case T_PTR:   return US"PTR";
   case T_SOA:   return US"SOA";
   case T_SRV:   return US"SRV";
   case T_NS:    return US"NS";
   case T_CNAME: return US"CNAME";

+  case T_TLSA:  return US"TLSA";

   default:      return US"?";
   }
 }
   default:      return US"?";
   }
 }


@@ -422,11 +517,12 @@ Returns:     the return code
 */
 
 static int
 */
 
 static int

-dns_return(uschar *name, int type, int rc)
+dns_return(const uschar * name, int type, int rc)

 {
 {

+res_state resp = os_get_dns_resolver_res();

 tree_node *node = store_get_perm(sizeof(tree_node) + 290);
 sprintf(CS node->name, "%.255s-%s-%lx", name, dns_text_type(type),
 tree_node *node = store_get_perm(sizeof(tree_node) + 290);
 sprintf(CS node->name, "%.255s-%s-%lx", name, dns_text_type(type),

-  _res.options);
+  resp->options);

 node->data.val = rc;
 (void)tree_insertnode(&tree_dns_fails, node);
 return rc;
 node->data.val = rc;
 (void)tree_insertnode(&tree_dns_fails, node);
 return rc;


@@ -453,18 +549,20 @@ Arguments:
 Returns:    DNS_SUCCEED   successful lookup
             DNS_NOMATCH   name not found (NXDOMAIN)
                           or name contains illegal characters (if checking)
 Returns:    DNS_SUCCEED   successful lookup
             DNS_NOMATCH   name not found (NXDOMAIN)
                           or name contains illegal characters (if checking)

+                          or name is an IP address (for IP address lookup)

             DNS_NODATA    domain exists, but no data for this type (NODATA)
             DNS_AGAIN     soft failure, try again later
             DNS_FAIL      DNS failure
 */
 
 int
             DNS_NODATA    domain exists, but no data for this type (NODATA)
             DNS_AGAIN     soft failure, try again later
             DNS_FAIL      DNS failure
 */
 
 int

-dns_basic_lookup(dns_answer *dnsa, uschar *name, int type)
+dns_basic_lookup(dns_answer *dnsa, const uschar *name, int type)

 {
 {

-int rc = -1;

 #ifndef STAND_ALONE
 #ifndef STAND_ALONE

-uschar *save;
+int rc = -1;
+const uschar *save_domain;

 #endif
 #endif

+res_state resp = os_get_dns_resolver_res();

 
 tree_node *previous;
 uschar node_name[290];
 
 tree_node *previous;
 uschar node_name[290];


@@ -475,7 +573,7 @@ have many addresses in the same domain. We rely on the resolver and name server
 caching for successful lookups. */
 
 sprintf(CS node_name, "%.255s-%s-%lx", name, dns_text_type(type),
 caching for successful lookups. */
 
 sprintf(CS node_name, "%.255s-%s-%lx", name, dns_text_type(type),

-  _res.options);
+  resp->options);

 previous = tree_search(tree_dns_fails, node_name);
 if (previous != NULL)
   {
 previous = tree_search(tree_dns_fails, node_name);
 if (previous != NULL)
   {


@@ -504,25 +602,23 @@ For SRV records, we omit the initial _smtp._tcp. components at the start. */
 
 #ifndef STAND_ALONE   /* Omit this for stand-alone tests */
 
 
 #ifndef STAND_ALONE   /* Omit this for stand-alone tests */
 

-if (check_dns_names_pattern[0] != 0 && type != T_PTR)
+if (check_dns_names_pattern[0] != 0 && type != T_PTR && type != T_TXT)

   {
   {

-  uschar *checkname = name;
+  const uschar *checkname = name;

   int ovector[3*(EXPAND_MAXN+1)];
 
   int ovector[3*(EXPAND_MAXN+1)];
 

-  if (regex_check_dns_names == NULL)
-    regex_check_dns_names =
-      regex_must_compile(check_dns_names_pattern, FALSE, TRUE);
+  dns_pattern_init();

 
   /* For an SRV lookup, skip over the first two components (the service and
   protocol names, which both start with an underscore). */
 
 
   /* For an SRV lookup, skip over the first two components (the service and
   protocol names, which both start with an underscore). */
 

-  if (type == T_SRV)
+  if (type == T_SRV || type == T_TLSA)

     {
     while (*checkname++ != '.');
     while (*checkname++ != '.');
     }
 
     {
     while (*checkname++ != '.');
     while (*checkname++ != '.');
     }
 

-  if (pcre_exec(regex_check_dns_names, NULL, CS checkname, Ustrlen(checkname),
+  if (pcre_exec(regex_check_dns_names, NULL, CCS checkname, Ustrlen(checkname),

       0, PCRE_EOPT, ovector, sizeof(ovector)/sizeof(int)) < 0)
     {
     DEBUG(D_dns)
       0, PCRE_EOPT, ovector, sizeof(ovector)/sizeof(int)) < 0)
     {
     DEBUG(D_dns)


@@ -539,16 +635,34 @@ if (check_dns_names_pattern[0] != 0 && type != T_PTR)
 number of bytes the message would need, so we need to check for this case. The
 effect is to truncate overlong data.
 
 number of bytes the message would need, so we need to check for this case. The
 effect is to truncate overlong data.
 

-If we are running in the test harness, instead of calling the normal resolver
+On some systems, res_search() will recognize "A-for-A" queries and return
+the IP address instead of returning -1 with h_error=HOST_NOT_FOUND. Some
+nameservers are also believed to do this. It is, of course, contrary to the
+specification of the DNS, so we lock it out. */
+
+if ((
+    #ifdef SUPPORT_A6
+    type == T_A6 ||
+    #endif
+    type == T_A || type == T_AAAA) &&
+    string_is_ip_address(name, NULL) != 0)
+  return DNS_NOMATCH;
+
+/* If we are running in the test harness, instead of calling the normal resolver

 (res_search), we call fakens_search(), which recognizes certain special
 domains, and interfaces to a fake nameserver for certain special zones. */
 
 if (running_in_test_harness)
   dnsa->answerlen = fakens_search(name, type, dnsa->answer, MAXPACKET);
 else
 (res_search), we call fakens_search(), which recognizes certain special
 domains, and interfaces to a fake nameserver for certain special zones. */
 
 if (running_in_test_harness)
   dnsa->answerlen = fakens_search(name, type, dnsa->answer, MAXPACKET);
 else

-  dnsa->answerlen = res_search(CS name, C_IN, type, dnsa->answer, MAXPACKET);
+  dnsa->answerlen = res_search(CCS name, C_IN, type, dnsa->answer, MAXPACKET);

 
 

-if (dnsa->answerlen > MAXPACKET) dnsa->answerlen = MAXPACKET;
+if (dnsa->answerlen > MAXPACKET)
+  {
+  DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) resulted in overlong packet (size %d), truncating to %d.\n",
+    name, dns_text_type(type), dnsa->answerlen, MAXPACKET);
+  dnsa->answerlen = MAXPACKET;
+  }

 
 if (dnsa->answerlen < 0) switch (h_errno)
   {
 
 if (dnsa->answerlen < 0) switch (h_errno)
   {


@@ -562,12 +676,12 @@ if (dnsa->answerlen < 0) switch (h_errno)
     name, dns_text_type(type));
 
   /* Cut this out for various test programs */
     name, dns_text_type(type));
 
   /* Cut this out for various test programs */

-  #ifndef STAND_ALONE
-  save = deliver_domain;
-  deliver_domain = name;  /* set $domain */
-  rc = match_isinlist(name, &dns_again_means_nonexist, 0, NULL, NULL,
+#ifndef STAND_ALONE
+  save_domain = deliver_domain;
+  deliver_domain = string_copy(name);  /* set $domain */
+  rc = match_isinlist(name, (const uschar **)&dns_again_means_nonexist, 0, NULL, NULL,

     MCL_DOMAIN, TRUE, NULL);
     MCL_DOMAIN, TRUE, NULL);

-  deliver_domain = save;
+  deliver_domain = save_domain;

   if (rc != OK)
     {
     DEBUG(D_dns) debug_printf("returning DNS_AGAIN\n");
   if (rc != OK)
     {
     DEBUG(D_dns) debug_printf("returning DNS_AGAIN\n");


@@ -577,9 +691,9 @@ if (dnsa->answerlen < 0) switch (h_errno)
     "DNS_NOMATCH\n", name);
   return dns_return(name, type, DNS_NOMATCH);
 
     "DNS_NOMATCH\n", name);
   return dns_return(name, type, DNS_NOMATCH);
 

-  #else   /* For stand-alone tests */
+#else   /* For stand-alone tests */

   return dns_return(name, type, DNS_AGAIN);
   return dns_return(name, type, DNS_AGAIN);

-  #endif
+#endif

 
   case NO_RECOVERY:
   DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave NO_RECOVERY\n"
 
   case NO_RECOVERY:
   DEBUG(D_dns) debug_printf("DNS lookup of %s (%s) gave NO_RECOVERY\n"


@@ -640,10 +754,12 @@ Returns:                DNS_SUCCEED   successful lookup
 */
 
 int
 */
 
 int

-dns_lookup(dns_answer *dnsa, uschar *name, int type, uschar **fully_qualified_name)
+dns_lookup(dns_answer *dnsa, const uschar *name, int type,
+  const uschar **fully_qualified_name)

 {
 int i;
 {
 int i;

-uschar *orig_name = name;
+const uschar *orig_name = name;
+BOOL secure_so_far = TRUE;

 
 /* Loop to follow CNAME chains so far, but no further... */
 
 
 /* Loop to follow CNAME chains so far, but no further... */
 


@@ -677,12 +793,10 @@ for (i = 0; i < 10; i++)
     else if (rr->type == T_CNAME) cname_rr = *rr;
     }
 
     else if (rr->type == T_CNAME) cname_rr = *rr;
     }
 

-  /* If a CNAME was found, take the fully qualified name from it; otherwise
-  from the first data record, if present. For testing, there is a magic name
-  that gets its casing adjusted, because my resolver doesn't seem to pass back
-  upper case letters in domain names. */
+  /* For the first time round this loop, if a CNAME was found, take the fully
+  qualified name from it; otherwise from the first data record, if present. */

 
 

-  if (fully_qualified_name != NULL)
+  if (i == 0 && fully_qualified_name != NULL)

     {
     if (cname_rr.data != NULL)
       {
     {
     if (cname_rr.data != NULL)
       {


@@ -692,21 +806,20 @@ for (i = 0; i < 10; i++)
       }
     else if (type_rr.data != NULL)
       {
       }
     else if (type_rr.data != NULL)
       {

-      if (running_in_test_harness &&
-          Ustrcmp(type_rr.name, "uppercase.test.ex") == 0)
-        *fully_qualified_name = US"UpperCase.test.ex";
-      else
-        {
-        if (Ustrcmp(type_rr.name, *fully_qualified_name) != 0 &&
-            type_rr.name[0] != '*')
-          *fully_qualified_name = string_copy_dnsdomain(type_rr.name);
-        }
+      if (Ustrcmp(type_rr.name, *fully_qualified_name) != 0 &&
+          type_rr.name[0] != '*')
+        *fully_qualified_name = string_copy_dnsdomain(type_rr.name);

       }
     }
 
   /* If any data records of the correct type were found, we are done. */
 
       }
     }
 
   /* If any data records of the correct type were found, we are done. */
 

-  if (type_rr.data != NULL) return DNS_SUCCEED;
+  if (type_rr.data != NULL)
+    {
+    if (!secure_so_far)        /* mark insecure if any element of CNAME chain was */
+      dns_set_insecure(dnsa);
+    return DNS_SUCCEED;
+    }

 
   /* If there are no data records, we need to re-scan the DNS using the
   domain given in the CNAME record, which should exist (otherwise we should
 
   /* If there are no data records, we need to re-scan the DNS using the
   domain given in the CNAME record, which should exist (otherwise we should


@@ -715,9 +828,14 @@ for (i = 0; i < 10; i++)
 
   if (cname_rr.data == NULL) return DNS_FAIL;
   datalen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen,
 
   if (cname_rr.data == NULL) return DNS_FAIL;
   datalen = dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen,

-    cname_rr.data, (DN_EXPAND_ARG4_TYPE)data, 256);
+    cname_rr.data, (DN_EXPAND_ARG4_TYPE)data, sizeof(data));

   if (datalen < 0) return DNS_FAIL;
   name = data;
   if (datalen < 0) return DNS_FAIL;
   name = data;

+
+  if (!dns_is_secure(dnsa))
+    secure_so_far = FALSE;
+
+  DEBUG(D_dns) debug_printf("CNAME found: change to %s\n", name);

   }       /* Loop back to do another lookup */
 
 /*Control reaches here after 10 times round the CNAME loop. Something isn't
   }       /* Loop back to do another lookup */
 
 /*Control reaches here after 10 times round the CNAME loop. Something isn't


@@ -755,8 +873,8 @@ Returns:                DNS_SUCCEED   successful lookup
 */
 
 int
 */
 
 int

-dns_special_lookup(dns_answer *dnsa, uschar *name, int type,
-  uschar **fully_qualified_name)
+dns_special_lookup(dns_answer *dnsa, const uschar *name, int type,
+  const uschar **fully_qualified_name)

 {
 if (type >= 0) return dns_lookup(dnsa, name, type, fully_qualified_name);
 
 {
 if (type >= 0) return dns_lookup(dnsa, name, type, fully_qualified_name);
 


@@ -769,7 +887,7 @@ root servers. */
 
 if (type == T_ZNS)
   {
 
 if (type == T_ZNS)
   {

-  uschar *d = name;
+  const uschar *d = name;

   while (d != 0)
     {
     int rc = dns_lookup(dnsa, d, T_NS, fully_qualified_name);
   while (d != 0)
     {
     int rc = dns_lookup(dnsa, d, T_NS, fully_qualified_name);


@@ -802,7 +920,7 @@ if (type == T_CSA)
   rc = dns_lookup(dnsa, srvname, T_SRV, NULL);
   if (rc == DNS_SUCCEED || rc == DNS_AGAIN)
     {
   rc = dns_lookup(dnsa, srvname, T_SRV, NULL);
   if (rc == DNS_SUCCEED || rc == DNS_AGAIN)
     {

-    if (rc == DNS_SUCCEED) *fully_qualified_name = name;
+    if (rc == DNS_SUCCEED) *fully_qualified_name = string_copy(name);

     return rc;
     }
 
     return rc;
     }
 


@@ -910,7 +1028,7 @@ if (type == T_CSA)
       /* Extract the numerical SRV fields (p is incremented) */
       p = rr->data;
       GETSHORT(priority, p);
       /* Extract the numerical SRV fields (p is incremented) */
       p = rr->data;
       GETSHORT(priority, p);

-      GETSHORT(weight, p);
+      GETSHORT(weight, p);     weight = weight; /* compiler quietening */

       GETSHORT(port, p);
 
       /* Check the CSA version number */
       GETSHORT(port, p);
 
       /* Check the CSA version number */


@@ -1152,4 +1270,16 @@ else
 return yield;
 }
 
 return yield;
 }
 

+
+
+void
+dns_pattern_init(void)
+{
+if (check_dns_names_pattern[0] != 0 && !regex_check_dns_names)
+  regex_check_dns_names =
+    regex_must_compile(check_dns_names_pattern, FALSE, TRUE);
+}
+
+/* vi: aw ai sw=2
+*/

 /* End of dns.c */
 /* End of dns.c */