ctf_md5_bot.rs

extern crate crypto;
extern crate rand;

use std::thread;
use std::io::{Read,Write,BufRead,BufReader,BufWriter};
use std::net::{TcpListener, TcpStream};

use rand::Rng;
use crypto::md5::Md5;
use crypto::digest::Digest;

static charset: &'static str = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
static flag: &'static str = "CTF{I_4M_N0T_A_P4Nd4_tH0ugH}";

fn random_string() -> (String,String) {
    let mut sh = Md5::new();
    let size = rand::thread_rng().gen_range(32,64);
    let mut output: Vec<char>= Vec::new();

    for i in 0..size {
        let rnd_index = rand::thread_rng().gen_range(0,charset.len());
        output.push(charset.chars().nth(rnd_index).unwrap());
    }
    
    let result: String = output.into_iter().collect();
    sh.input_str(&result);

    (result,sh.result_str())
}

fn handle_client(mut stream: TcpStream){
    let mut answer = String::new();
    let mut counter = 10000;
    
    let mut input = BufReader::new(&stream);
    let mut output = BufWriter::new(&stream);

    loop {
        let (sample,target) = random_string();
        
        write!(output,"{}\n",sample);
        output.flush();

        input.read_line(&mut answer).unwrap();

        answer = answer.replace("\n","");
        
        if answer == target {
            counter -= 1;
            if counter == 0 {
                write!(output,"{}\n",flag);
                return
            }
        }else{
            return
        }

        answer = String::new();
    }
}

fn main() {
    println!("Starting server on port -> 22222");
    
    let server_socket = TcpListener::bind("127.0.0.1:22222").unwrap();

    for stream in server_socket.incoming() {
        match stream {
            Ok(stream) => {
                thread::spawn(move || {
                handle_client(stream);
                });
            },
            Err(e) => {}
        }
    }


}