Harden dnsdb against crafted DNS responses. Bug 3033

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

diff --git a/src/src/dns.c b/src/src/dns.c
index 63856ead3a662596d1860617305aa0d189c1f4a0..8dc3695a118782926b1ec994997f2dfc420a5acb 100644 (file)
--- a/src/src/dns.c
+++ b/src/src/dns.c
@@ -2,8 +2,8 @@
 *     Exim - an Internet mail transport agent    *
 *************************************************/
 
+/* Copyright (c) The Exim Maintainers 2020 - 2022 */
 /* Copyright (c) University of Cambridge 1995 - 2018 */
-/* Copyright (c) The Exim Maintainers 2020 */
 /* See the file NOTICE for conditions of use and distribution. */
 
 /* Functions for interfacing with the DNS. */
@@ -258,7 +258,7 @@ else
   {
   int v6[4];
 
-  g = string_get_tainted(32, is_tainted(string));
+  g = string_get_tainted(32, string);
   (void)host_aton(string, v6);
 
   /* The original specification for IPv6 reverse lookup was to invert each
@@ -304,7 +304,7 @@ Return: TRUE for a bad result
 static BOOL
 dnss_inc_aptr(const dns_answer * dnsa, dns_scan * dnss, unsigned delta)
 {
-return (dnss->aptr += delta) >= dnsa->answer + dnsa->answerlen;
+return (dnss->aptr += delta) > dnsa->answer + dnsa->answerlen;
 }
 
 /*************************************************
@@ -388,7 +388,7 @@ if (reset != RESET_NEXT)
       TRACE trace = "A-hdr";
       if (dnss_inc_aptr(dnsa, dnss, namelen+8)) goto null_return;
       GETSHORT(dnss->srr.size, dnss->aptr); /* size of data portion */
-      /* skip over it */
+      /* skip over it, checking for a bogus size */
       TRACE trace = "A-skip";
       if (dnss_inc_aptr(dnsa, dnss, dnss->srr.size)) goto null_return;
       }
@@ -428,10 +428,9 @@ GETLONG(dnss->srr.ttl, dnss->aptr);                /* TTL */
 GETSHORT(dnss->srr.size, dnss->aptr);          /* Size of data portion */
 dnss->srr.data = dnss->aptr;                   /* The record's data follows */
 
-/* Unchecked increment ok here since no further access on this iteration;
-will be checked on next at "R-name". */
-
-dnss->aptr += dnss->srr.size;                  /* Advance to next RR */
+/* skip over it, checking for a bogus size */
+if (dnss_inc_aptr(dnsa, dnss, dnss->srr.size))
+  goto null_return;
 
 /* Return a pointer to the dns_record structure within the dns_answer. This is
 for convenience so that the scans can use nice-looking for loops. */
@@ -637,7 +636,7 @@ if ((previous = tree_search(tree_dns_fails, node_name)))
   e = previous->data.ptr;
 else
   {
-  e = store_get_perm(DNS_FAILNODE_SIZE, is_tainted(name));
+  e = store_get_perm(DNS_FAILNODE_SIZE, name);
   new = (void *)(e+1);
   dns_fail_tag(new->name, name, type);
   new->data.ptr = e;
@@ -1065,7 +1064,7 @@ for (int i = 0; i <= dns_cname_loops; i++)
     return DNS_FAIL;
 
   /* DNS data comes from the outside, hence tainted */
-  data = store_get(256, TRUE);
+  data = store_get(256, GET_TAINTED);
   if (dn_expand(dnsa->answer, dnsa->answer + dnsa->answerlen,
       cname_rr.data, (DN_EXPAND_ARG4_TYPE)data, 256) < 0)
     return DNS_FAIL;
@@ -1148,7 +1147,7 @@ switch (type)
   case T_CSA:
     {
     uschar *srvname, *namesuff, *tld;
-    int priority, weight, port;
+    int priority, dummy_weight, port;
     int limit, rc, i;
     BOOL ipv6;
     dns_record *rr;
@@ -1237,7 +1236,7 @@ switch (type)
 
        /* Extract the numerical SRV fields (p is incremented) */
        GETSHORT(priority, p);
-       GETSHORT(weight, p);
+       GETSHORT(dummy_weight, p);
        GETSHORT(port, p);
 
        /* Check the CSA version number */
@@ -1293,7 +1292,7 @@ if (rr->type == T_A)
   if (p + 4 <= dnsa_lim)
     {
     /* the IP is not regarded as tainted */
-    yield = store_get(sizeof(dns_address) + 20, FALSE);
+    yield = store_get(sizeof(dns_address) + 20, GET_UNTAINTED);
     (void)sprintf(CS yield->address, "%d.%d.%d.%d", p[0], p[1], p[2], p[3]);
     yield->next = NULL;
     }
@@ -1307,7 +1306,7 @@ else
     {
     struct in6_addr in6;
     for (int i = 0; i < 16; i++) in6.s6_addr[i] = rr->data[i];
-    yield = store_get(sizeof(dns_address) + 50, FALSE);
+    yield = store_get(sizeof(dns_address) + 50, GET_UNTAINTED);
     inet_ntop(AF_INET6, &in6, CS yield->address, 50);
     yield->next = NULL;
     }