add reverse lookup check

diff --git a/src/ngircd/resolve.c b/src/ngircd/resolve.c
index d261fd0a5873c2c7242b01d190d6bddc7dde7428..5529f168f9aca38cad5eb06a89d3eb429e28a2cf 100644 (file)
--- a/src/ngircd/resolve.c
+++ b/src/ngircd/resolve.c
@@ -14,7 +14,7 @@
 
 #include "portab.h"
 
-static char UNUSED id[] = "$Id: resolve.c,v 1.13 2005/07/07 18:39:08 fw Exp $";
+static char UNUSED id[] = "$Id: resolve.c,v 1.14 2005/07/24 21:42:00 fw Exp $";
 
 #include "imp.h"
 #include <assert.h>
@@ -185,8 +185,10 @@ Do_ResolveAddr( struct sockaddr_in *Addr, int w_fd )
         * pipe to parent. */
 
        char hostname[HOST_LEN];
+       char ipstr[HOST_LEN];
        struct hostent *h;
        size_t len;
+       struct in_addr *addr;
 #ifdef IDENTAUTH
        char *res;
 #endif
@@ -194,15 +196,30 @@ Do_ResolveAddr( struct sockaddr_in *Addr, int w_fd )
        /* Resolve IP address */
        Log_Resolver( LOG_DEBUG, "Now resolving %s ...", inet_ntoa( Addr->sin_addr ));
        h = gethostbyaddr( (char *)&Addr->sin_addr, sizeof( Addr->sin_addr ), AF_INET );
-       if( h ) strlcpy( hostname, h->h_name, sizeof( hostname ));
-       else
-       {
+       if (!h) {
 #ifdef h_errno
                Log_Resolver( LOG_WARNING, "Can't resolve address \"%s\": %s!", inet_ntoa( Addr->sin_addr ), Get_Error( h_errno ));
 #else
                Log_Resolver( LOG_WARNING, "Can't resolve address \"%s\"!", inet_ntoa( Addr->sin_addr ));
 #endif 
                strlcpy( hostname, inet_ntoa( Addr->sin_addr ), sizeof( hostname ));
+       } else {
+               strlcpy( hostname, h->h_name, sizeof( hostname ));
+
+               h = gethostbyname( hostname );
+               if ( h ) {
+                       if (memcmp(h->h_addr, &Addr->sin_addr, sizeof (struct in_addr))) {
+                               addr = (struct in_addr*) h->h_addr;
+                               strlcpy(ipstr, inet_ntoa(*addr), sizeof ipstr); 
+                               Log(LOG_WARNING,"Possible forgery: %s resolved to %s (which is at ip %s!)",
+                                                               inet_ntoa( Addr->sin_addr), hostname, ipstr);
+                               strlcpy( hostname, inet_ntoa( Addr->sin_addr ), sizeof( hostname ));
+                       }
+               } else {
+                       Log(LOG_WARNING, "Possible forgery: %s resolved to %s (which has no ip address)",
+                                               inet_ntoa( Addr->sin_addr ), hostname);
+                               strlcpy( hostname, inet_ntoa( Addr->sin_addr ), sizeof( hostname ));
+               }
        }
        Log_Resolver( LOG_DEBUG, "Ok, translated %s to \"%s\".", inet_ntoa( Addr->sin_addr ), hostname );