Listing 1: telnet_plugin.c

/* telnet_plugin.c 
   David Endler

Used to log the telnet/rlogin port for incoming connections */

#include    <signal.h>
#include    <sys/types.h>
#include    <sys/resource.h>
#include    <sys/param.h>
#include     <sys/fcntl.h>
#include    <sys/termios.h>
#include    <netinet/in.h>
#include    <arpa/inet.h>
#include    <stdio.h>
#include    <varargs.h>
#include    <signal.h>
#include    <netdb.h>
#include    <syslog.h>
#include    <errno.h>
#include    <string.h>
#include    <stdlib.h>
extern int    errno;

/* globals */

/*ARGSUSED*/
main(argc, argv)
int    argc;
char    **argv;        /* argv1 is the service name */
{
    int            i;
    char         tbuf[1500];
    char         username[1500];
    char*         password;
    int         char_val=-1;
    int        non_white_space_flag=0;    
    int        index=0;
    sigset_t    mask;
    struct         sigaction signal_vector;

    openlog(“telnet_plugin”, LOG_PID | LOG_ODELAY, LOG_DAEMON);

/* SIGNAL HANDLING */

    if (sigemptyset (&mask) == -1) {
    perror (“sigemptyset FAILED”);
    exit (1);
    }
    if ((sigaddset (&mask, SIGINT) == -1) ||
          (sigaddset (&mask, SIGQUIT) == -1) ||
              (sigaddset (&mask, SIGTSTP) == -1)) {
      perror (“sigaddset FAILED”);
      exit (1);
      }
    if (sighold (SIGINT) == -1) {
    perror (“sigaction FAILED FOR SIGINT”);
    exit (1);
    }
    if (sighold (SIGQUIT) == -1) {
    perror (“sigaction FAILED FOR SIGQUIT”);
    exit (1);
    }
    if (sighold (SIGTSTP) == -1) {
    perror (“sigaction FAILED FOR SIGTSTP”);
    exit (1);
    }

fprintf(stderr,” UNIX(r) System V Release 4.0 (honeypot)”);


/*
     * We assume we're invoked by inetd, so the socket that the 
     * connection is on, is open on descriptors 0, 1 and 2.
     *
     * First get the Internet address of the client process.
     * This is required for all the authentication we perform.
     */

    for (i=0;i<5;i++) {
do {
    non_white_space_flag = 0;
    index = 0;    
    char_val=-1;

    fprintf(stderr,”login: “);
    while (char_val != 10) { 
        char_val = getc(stdin); 
        if ((char_val != 32) && (char_val != 10))
            {non_white_space_flag=1;}    
        if (char_val != 10) {username[index++] = (char)char_val;}
    }
    username[index]='\0';
}
while (non_white_space_flag == 0);


    fprintf(stderr,”Password: “);
    password = getpass(“”);
    sleep(4);
    fprintf(stderr,”Login incorrect”);
    syslog(LOG_ALERT, “Someone tried to access telnet port with \

           username:%s and password:%s”,username, password);
    fprintf(stderr,”\n”);

        }
    }