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use std::io;
use std::net::{SocketAddr, ToSocketAddrs};
use std::time::{Duration, SystemTime, SystemTimeError};
use clap::{arg, Parser};
use tokio::net::UdpSocket;
use tracing::{debug, error};
use crate::Destination::{Address, SockAddr};
const TTL: Duration = Duration::from_secs(300);
/// Simple program to greet a person
#[derive(Parser, Debug)]
#[command(author, version, about, long_about = None)]
struct Args {
/// The address and port to listen and accept cleartext UDP datagrams from
#[arg(short, long)]
bind: String,
/// The local endpoint to read cleartext datagrams from & write to
#[arg(short, long)]
local: String,
/// The destination to send obfuscated UDP datagrams to
#[arg(short, long)]
sendto: Option<String>,
/// The hex representation of XOR key to use
#[arg(short, long)]
key: String,
}
#[derive(Debug, Eq, PartialEq)]
enum Destination<'a> {
None,
Address(&'a String),
SockAddr(SocketAddr),
}
#[tokio::main]
async fn main() {
tracing_subscriber::fmt::init();
let args = Args::parse();
let key = hex::decode(args.key)
.expect("failed to decode key hex string");
let sock = UdpSocket::bind(&args.bind).await
.expect("failed to bind UDP endpoint");
let mut buf = [0; 65536];
let local = args.local.parse().expect("failed to parse local address");
let mut sendto = Destination::None;
let args_sendto: String;
if let Some(s) = args.sendto {
args_sendto = s;
sendto = Address(&args_sendto);
}
let mut addr_sendto: Option<SocketAddr> = None;
let mut addr_sendto_t = SystemTime::UNIX_EPOCH;
loop {
match sock.recv_from(&mut buf).await {
Ok((len, addr)) => {
debug!("recv_from OK, len {}, addr {}", len, addr);
let mut i = 0;
let n = key.len();
for j in 0..len {
buf[j] ^= key[i];
i += 1;
if i == n {
i = 0;
}
}
if sendto == Destination::None && addr != local {
// assume the packet is coming from target
// update missing sendto parameter
sendto = SockAddr(addr);
}
let sendto = match sendto {
Destination::None => Destination::None,
Address(addr) => {
let now = SystemTime::now();
if now.duration_since(addr_sendto_t)
.or::<SystemTimeError>(Ok(Duration::from_secs(0))).unwrap() > TTL {
// update
debug!("resolving address: {}", &addr);
match resolve_addr(&addr) {
Ok(addr) => {
addr_sendto = Some(addr);
addr_sendto_t = SystemTime::now();
SockAddr(addr)
}
Err(why) => {
error!("failed to resolve address {}: {}", addr, why);
Destination::None
}
}
} else {
// cache is still valid
match addr_sendto {
None => Destination::None,
Some(addr) => SockAddr(addr),
}
}
}
SockAddr(addr) => SockAddr(addr),
};
let target = match sendto {
Destination::None => None,
Address(_) => panic!("unresolved address"),
SockAddr(sendto_addr) => {
if addr == sendto_addr {
// remote -> local
Some(local)
} else {
Some(sendto_addr)
}
}
};
match target {
None => {
error!("cannot send_to: destination not determined");
continue;
}
Some(target) => {
if let Err(why) = sock.send_to(&buf[..len], target).await {
debug!("send_to failed, dest: {}, error: {}", target, why);
} else {
debug!("send_to OK, len: {}, dest: {}", len, target);
}
}
}
}
Err(why) => {
debug!("recv_from failed: {}", why);
}
}
}
}
fn resolve_addr(addr: &String) -> io::Result<SocketAddr> {
match addr.to_socket_addrs() {
Ok(mut addrs) => match addrs.next() {
None => Err(io::Error::new(io::ErrorKind::Other, "no available address")),
Some(addr) => Ok(addr),
},
Err(why) => Err(why),
}
}
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