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// -*- coding: utf-8 -*-
//
// Copyright (C) 2024 Michael Büsch <m@bues.ch>
//
// Licensed under the Apache License version 2.0
// or the MIT license, at your option.
// SPDX-License-Identifier: Apache-2.0 OR MIT
use crate::{
client::Client,
resolver::{is_ipv4_addr, is_ipv6_addr, ResMode},
};
use anyhow::{self as ah, format_err as err, Context as _};
use letmein_conf::Config;
use letmein_proto::{Key, Message, Operation, ResourceId, UserId};
use std::{path::Path, sync::Arc, time::Duration};
/// Address types to knock.
#[derive(Copy, Clone, Debug, Default, PartialEq, Eq)]
pub enum AddrMode {
#[default]
TryBoth,
Both,
Ipv6,
Ipv4,
}
impl From<(bool, bool)> for AddrMode {
fn from(ipv4_ipv6: (bool, bool)) -> Self {
match ipv4_ipv6 {
(false, false) => AddrMode::TryBoth,
(true, true) => AddrMode::Both,
(false, true) => AddrMode::Ipv6,
(true, false) => AddrMode::Ipv4,
}
}
}
/// Knock protocol sequence - client side.
struct KnockSeq<'a> {
pub verbose: bool,
pub addr: &'a str,
pub server_port: u16,
pub control_timeout: Duration,
pub user: UserId,
pub resource: ResourceId,
pub key: &'a Key,
}
impl<'a> KnockSeq<'a> {
/// Check if the server replied with a valid message.
fn check_reply(&self, msg: &Message) -> ah::Result<()> {
if msg.user() != self.user {
eprintln!(
"Warning: The server replied with a different user identifier. \
Expected {}, but received {}.",
self.user,
msg.user(),
);
// continue processing this message.
}
if msg.resource() != self.resource {
eprintln!(
"Warning: The server replied with a different resource identifier. \
Expected {}, but received {}.",
self.resource,
msg.resource(),
);
// continue processing this message.
}
Ok(())
}
/// Run the knock protocol sequence.
pub async fn knock_sequence(&self, resolver_mode: ResMode) -> ah::Result<()> {
if self.verbose {
println!(
"Connecting to letmein server '{}:{}'.",
self.addr, self.server_port
);
}
let mut client = Client::new(
self.addr,
self.server_port,
self.control_timeout,
resolver_mode,
)
.await
.context("Client init")?;
if self.verbose {
println!("Sending 'Knock' packet.");
}
let mut knock = Message::new(Operation::Knock, self.user, self.resource);
knock.generate_auth_no_challenge(self.key);
client.send_msg(knock).await.context("Send knock")?;
if self.verbose {
println!("Receiving 'Challenge' packet.");
}
let challenge = client.recv_specific_msg(Operation::Challenge).await?;
self.check_reply(&challenge)?;
if self.verbose {
println!("Sending 'Response' packet.");
}
let mut response = Message::new(Operation::Response, self.user, self.resource);
response.generate_auth(self.key, challenge);
client.send_msg(response).await.context("Send response")?;
if self.verbose {
println!("Receiving 'ComeIn' packet.");
}
let comein = client.recv_specific_msg(Operation::ComeIn).await?;
self.check_reply(&comein)?;
if self.verbose {
println!("Knock sequence successful.");
}
Ok(())
}
}
/// Run the `knock` command.
pub async fn run_knock(
conf: Arc<Config>,
verbose: bool,
addr: &str,
addr_mode: AddrMode,
server_port: Option<u16>,
knock_port: u16,
user: Option<UserId>,
) -> ah::Result<()> {
let confpath = conf.get_path().unwrap_or(Path::new(""));
let user = user.unwrap_or_else(|| conf.default_user());
let Some(key) = conf.key(user) else {
return Err(err!("No key found in {confpath:?} for user {user}"));
};
let Some(resource) = conf.resource_id_by_port(knock_port, Some(user)) else {
return Err(err!(
"Port {knock_port} is not mapped to a resource in {confpath:?}"
));
};
let server_port = server_port.unwrap_or_else(|| conf.port());
let control_timeout = conf.control_timeout();
let seq = KnockSeq {
verbose,
addr,
server_port,
control_timeout,
user,
resource,
key,
};
match addr_mode {
AddrMode::TryBoth => {
if verbose {
println!("Trying to knock on '{addr}:{knock_port}' IPv6 and IPv4.");
}
if is_ipv4_addr(addr) {
// For a raw IPv4 address only knock IPv4.
seq.knock_sequence(ResMode::Ipv4).await?;
} else if is_ipv6_addr(addr) {
// For a raw IPv6 address only knock IPv6.
seq.knock_sequence(ResMode::Ipv6).await?;
} else {
// For host names try both.
let res6 = seq.knock_sequence(ResMode::Ipv6).await;
let res4 = seq.knock_sequence(ResMode::Ipv4).await;
if res6.is_err() && res4.is_err() {
return res6;
}
}
}
AddrMode::Both => {
if verbose {
println!("Knocking on '{addr}:{knock_port}' IPv6 and IPv4.");
}
seq.knock_sequence(ResMode::Ipv6).await?;
seq.knock_sequence(ResMode::Ipv4).await?;
}
AddrMode::Ipv6 => {
if verbose {
println!("Knocking on '{addr}:{knock_port}' IPv6.");
}
seq.knock_sequence(ResMode::Ipv6).await?;
}
AddrMode::Ipv4 => {
if verbose {
println!("Knocking on '{addr}:{knock_port}' IPv4.");
}
seq.knock_sequence(ResMode::Ipv4).await?;
}
}
Ok(())
}
// vim: ts=4 sw=4 expandtab
|
