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  1. /*
  2.  * Copyright (C) 2004 Pawel Foremski <pjf@asn.pl>
  3.  *
  4.  * This program is free software; you can redistribute it and/or 
  5.  * modify it under the terms of the GNU General Public License 
  6.  * as published by the Free Software Foundation; either 
  7.  * version 2 of the License, or (at your option) any later 
  8.  * version.
  9.  *
  10.  * This program is distributed in the hope that it will be useful,
  11.  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12.  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13.  * GNU General Public License for more details.
  14.  *
  15.  * You should have received a copy of the GNU General Public License
  16.  * along with this program; if not, write to the Free Software Foundation,
  17.  * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  18.  *
  19.  ***
  20.  *
  21.  * Implements tarpitting
  22.  *
  23.  * Compile with: gcc -O2 -s -o tarpit ./tarpit.c
  24.  * Set in tcprules: TARPITCOUNT=n,TARPITDELAY={n, NORMAL, MEDIUM, HARD}
  25.  *
  26.  */
  27.  
  28. #include <stdlib.h>
  29. #include <stdio.h>
  30. #include <unistd.h>
  31.  
  32. #ifndef MIN
  33. #define MIN(X, Y) ((X) < (Y) ? (X) : (Y))
  34. #endif
  35.  
  36. int main()
  37. {
  38.   char *tcount, *tdelay, *rcount, *sender, *tmax, *rok;
  39.   int tc, rc;
  40.   /* some servers have a smtp command timeout of 60 seconds so let's be on
  41.    * the safe side and make a default tarpit maximum of 50 seconds
  42.    */
  43.   int max_err = 50, max_ok = 10;
  44.   int max;
  45.  
  46.   if (!(tcount = getenv("TARPITCOUNT")) ||
  47.       !(tdelay = getenv("TARPITDELAY"))) return 0;
  48.  
  49.   if (!(rcount = getenv("SMTPRCPTCOUNT")))
  50.     { fprintf(stderr, "tarpit: error: can't get number of envelope recipients\n"); return 0; }
  51.  
  52.   if ((tmax = getenv("TARPITMAXDELAY")))
  53.     max_err = atoi(tmax);
  54.   if ((tmax = getenv("TARPITMAXDELAYOK")))
  55.     max_ok = atoi(tmax);
  56.   max = ((rok = getenv("SMTPRCPTHOSTSOK")) && *rok == '1') ? max_ok : max_err;
  57.  
  58.   tc = atoi(tcount); rc = atoi(rcount);
  59.   if (rc < tc) return 0; /* under limit */
  60.  
  61.   if (!(sender = getenv("SMTPMAILFROM")) || !*sender) sender = "unknown";
  62.  
  63.   if (rc == tc)
  64.     fprintf(stderr, "tarpit: started tarpitting mail from <%s>\n", sender);
  65.  
  66.   switch (*tdelay) {
  67.     case 'N': /* NORMAL */
  68.         sleep(MIN((rc - tc + 1) * 2, max));
  69.         break;
  70.     case 'M': /* MEDIUM */
  71.         sleep(MIN((rc - tc + 1) * 5, max));
  72.         break;
  73.     case 'H': /* HARD */
  74.         sleep(MIN((rc - tc + 1) * (rc - tc + 1), max));
  75.         break;
  76.     default:
  77.         sleep(MIN(atoi(tdelay), max));
  78.         break;
  79.   }
  80.  
  81.   return 0;
  82. }
  83.