MoinQ: attachment:helodnscheck.c of qmail/spp/badhelo/sagredo

   1 /*
   2 * Copyright (C) 2007 Jason Frisvold <friz@godshell.com>
   3 * Original Copyright (C) 2003-2004 Perolo Silantico <per.sil@gmx.it>
   4 *
   5 * This program is free software; you can redistribute it and/or
   6 * modify it under the terms of the GNU General Public License
   7 * as published by the Free Software Foundation; either
   8 * version 2 of the License, or (at your option) any later
   9 * version.
  10 *
  11 * This program is distributed in the hope that it will be useful,
  12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 * GNU General Public License for more details.
  15 *
  16 * You should have received a copy of the GNU General Public License
  17 * along with this program; if not, write to the Free Software Foundation,
  18 * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  19 ***
  20 * 1/16 Modified original version to check helo/ehlo instead of mail from
  21 ***
  22 *
  23 * $Id$
  24 *
  25 */
  26 
  27 #include <netinet/in.h>
  28 #include <arpa/nameser.h>
  29 #include <resolv.h>
  30 #include <string.h>
  31 #include <stdlib.h>
  32 #include <errno.h>
  33 #include <netdb.h>
  34 
  35 void block_permanent(const char* message) {
  36   printf("E553 sorry, %s (#5.7.1)\n", message);
  37   fprintf(stderr, "helo-dns-check: blocked with: %s\n", message);  
  38 }
  39 
  40 
  41 void block_temporary(const char* message) {
  42   printf("E451 %s (#4.3.0)\n", message);
  43   fprintf(stderr, "helo-dns-check: temporary failure: %s\n", message);  
  44 }
  45 
  46 int main(void) {
  47  unsigned char dns_answer[1023];
  48  char *helo_domain = getenv("SMTPHELOHOST");
  49  char *no_helo_check = getenv("NOHELODNSCHECK");
  50 
  51   if (no_helo_check) {
  52      return 0;
  53   }
  54 
  55   if (!helo_domain) {
  56     block_permanent("no HELO/EHLO hostname has been sent.");
  57     return 0;
  58   }
  59 
  60   /* init DNS library */
  61   res_init();
  62 
  63   /* check A record of host */ 
  64   if (res_query(helo_domain, C_IN, T_A, dns_answer, sizeof(dns_answer)) <= 0)
  65   {
  66     if ((errno == ECONNREFUSED) || (errno == TRY_AGAIN))
  67       block_temporary("DNS temporary failure.");
  68     else
  69       block_permanent("invalid host name in HELO/EHLO command.");
  70   }
  71 
  72   return 0;
  73 }