1 files changed, 27 insertions, 17 deletions

diff --git a/canohost.c b/canohost.c
index 417d95c18..533f2c24a 100644
--- a/canohost.c
+++ b/canohost.c
@@ -12,7 +12,7 @@
  */
 
 #include "includes.h"
-RCSID("$OpenBSD: canohost.c,v 1.36 2003/04/08 20:21:28 itojun Exp $");
+RCSID("$OpenBSD: canohost.c,v 1.37 2003/06/02 09:17:34 markus Exp $");
 
 #include "packet.h"
 #include "xmalloc.h"
@@ -27,7 +27,7 @@ static void check_ip_options(int, char *);
  */
 
 static char *
-get_remote_hostname(int socket, int verify_reverse_mapping)
+get_remote_hostname(int socket, int use_dns)
 {
         struct sockaddr_storage from;
         int i;
@@ -72,6 +72,9 @@ get_remote_hostname(int socket, int verify_reverse_mapping)
             NULL, 0, NI_NUMERICHOST) != 0)
                 fatal("get_remote_hostname: getnameinfo NI_NUMERICHOST failed");
 
+        if (!use_dns)
+                return xstrdup(ntop);
+
         if (from.ss_family == AF_INET)
                 check_ip_options(socket, ntop);
 
@@ -80,14 +83,24 @@ get_remote_hostname(int socket, int verify_reverse_mapping)
         if (getnameinfo((struct sockaddr *)&from, fromlen, name, sizeof(name),
             NULL, 0, NI_NAMEREQD) != 0) {
                 /* Host name not found.  Use ip address. */
-#if 0
-                logit("Could not reverse map address %.100s.", ntop);
-#endif
                 return xstrdup(ntop);
         }
 
-        /* Got host name. */
-        name[sizeof(name) - 1] = '\0';
+        /*
+         * if reverse lookup result looks like a numeric hostname,
+         * someone is trying to trick us by PTR record like following:
+         *      1.1.1.10.in-addr.arpa.  IN PTR  2.3.4.5
+         */
+        memset(&hints, 0, sizeof(hints));
+        hints.ai_socktype = SOCK_DGRAM; /*dummy*/
+        hints.ai_flags = AI_NUMERICHOST;
+        if (getaddrinfo(name, "0", &hints, &ai) == 0) {
+                logit("Nasty PTR record \"%s\" is set up for %s, ignoring",
+                    name, ntop);
+                freeaddrinfo(ai);
+                return xstrdup(ntop);
+        }
+
         /*
          * Convert it to all lowercase (which is expected by the rest
          * of this software).
@@ -95,9 +108,6 @@ get_remote_hostname(int socket, int verify_reverse_mapping)
         for (i = 0; name[i]; i++)
                 if (isupper(name[i]))
                         name[i] = tolower(name[i]);
-
-        if (!verify_reverse_mapping)
-                return xstrdup(name);
         /*
          * Map it back to an IP address and check that the given
          * address actually is an address of this host.  This is
@@ -180,14 +190,14 @@ check_ip_options(int socket, char *ipaddr)
  */
 
 const char *
-get_canonical_hostname(int verify_reverse_mapping)
+get_canonical_hostname(int use_dns)
 {
         static char *canonical_host_name = NULL;
-        static int verify_reverse_mapping_done = 0;
+        static int use_dns_done = 0;
 
         /* Check if we have previously retrieved name with same option. */
         if (canonical_host_name != NULL) {
-                if (verify_reverse_mapping_done != verify_reverse_mapping)
+                if (use_dns_done != use_dns)
                         xfree(canonical_host_name);
                 else
                         return canonical_host_name;
@@ -196,11 +206,11 @@ get_canonical_hostname(int verify_reverse_mapping)
         /* Get the real hostname if socket; otherwise return UNKNOWN. */
         if (packet_connection_is_on_socket())
                 canonical_host_name = get_remote_hostname(
-                    packet_get_connection_in(), verify_reverse_mapping);
+                    packet_get_connection_in(), use_dns);
         else
                 canonical_host_name = xstrdup("UNKNOWN");
 
-        verify_reverse_mapping_done = verify_reverse_mapping;
+        use_dns_done = use_dns;
         return canonical_host_name;
 }
 
@@ -294,11 +304,11 @@ get_remote_ipaddr(void)
 }
 
 const char *
-get_remote_name_or_ip(u_int utmp_len, int verify_reverse_mapping)
+get_remote_name_or_ip(u_int utmp_len, int use_dns)
 {
         static const char *remote = "";
         if (utmp_len > 0)
-                remote = get_canonical_hostname(verify_reverse_mapping);
+                remote = get_canonical_hostname(use_dns);
         if (utmp_len == 0 || strlen(remote) > utmp_len)
                 remote = get_remote_ipaddr();
         return remote;