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|
use spin::RwLock;
use std::collections::HashMap;
use std::net::SocketAddr;
use std::sync::Mutex;
use zerocopy::AsBytes;
use byteorder::{ByteOrder, LittleEndian};
use rand::prelude::*;
use x25519_dalek::PublicKey;
use x25519_dalek::StaticSecret;
use super::macs;
use super::messages::{CookieReply, Initiation, Response};
use super::messages::{TYPE_COOKIE_REPLY, TYPE_INITIATION, TYPE_RESPONSE};
use super::noise;
use super::peer::Peer;
use super::ratelimiter::RateLimiter;
use super::types::*;
const MAX_PEER_PER_DEVICE: usize = 1 << 20;
pub struct KeyState {
pub sk: StaticSecret, // static secret key
pub pk: PublicKey, // static public key
macs: macs::Validator, // validator for the mac fields
}
pub struct Device {
keyst: Option<KeyState>, // secret/public key
pk_map: HashMap<[u8; 32], Peer>, // public key -> peer state
id_map: RwLock<HashMap<u32, [u8; 32]>>, // receiver ids -> public key
limiter: Mutex<RateLimiter>,
}
/* A mutable reference to the device needs to be held during configuration.
* Wrapping the device in a RwLock enables peer config after "configuration time"
*/
impl Device {
/// Initialize a new handshake state machine
pub fn new() -> Device {
Device {
keyst: None,
pk_map: HashMap::new(),
id_map: RwLock::new(HashMap::new()),
limiter: Mutex::new(RateLimiter::new()),
}
}
fn update_ss(&self, peer: &mut Peer) -> Option<PublicKey> {
if let Some(key) = self.keyst.as_ref() {
if *peer.pk.as_bytes() == *key.pk.as_bytes() {
return Some(peer.pk);
}
peer.ss = *key.sk.diffie_hellman(&peer.pk).as_bytes();
} else {
peer.ss = [0u8; 32];
};
None
}
/// Update the secret key of the device
///
/// # Arguments
///
/// * `sk` - x25519 scalar representing the local private key
pub fn set_sk(&mut self, sk: Option<StaticSecret>) -> Option<PublicKey> {
// update secret and public key
self.keyst = sk.map(|sk| {
let pk = PublicKey::from(&sk);
let macs = macs::Validator::new(pk);
KeyState { pk, sk, macs }
});
// recalculate / erase the shared secrets for every peer
let mut ids = vec![];
let mut same = None;
for mut peer in self.pk_map.values_mut() {
// clear any existing handshake state
peer.reset_state().map(|id| ids.push(id));
// update precomputed shared secret
if let Some(key) = self.keyst.as_ref() {
peer.ss = *key.sk.diffie_hellman(&peer.pk).as_bytes();
if *peer.pk.as_bytes() == *key.pk.as_bytes() {
same = Some(peer.pk)
}
} else {
peer.ss = [0u8; 32];
};
}
// release ids from aborted handshakes
for id in ids {
self.release(id)
}
// if we found a peer matching the device public key, remove it.
same.map(|pk| {
self.pk_map.remove(pk.as_bytes());
pk
})
}
/// Return the secret key of the device
///
/// # Returns
///
/// A secret key (x25519 scalar)
pub fn get_sk(&self) -> Option<&StaticSecret> {
self.keyst.as_ref().map(|key| &key.sk)
}
/// Add a new public key to the state machine
/// To remove public keys, you must create a new machine instance
///
/// # Arguments
///
/// * `pk` - The public key to add
/// * `identifier` - Associated identifier which can be used to distinguish the peers
pub fn add(&mut self, pk: PublicKey) -> Result<(), ConfigError> {
// ensure less than 2^20 peers
if self.pk_map.len() > MAX_PEER_PER_DEVICE {
return Err(ConfigError::new("Too many peers for device"));
}
// create peer and precompute static secret
let mut peer = Peer::new(
pk,
self.keyst
.as_ref()
.map(|key| *key.sk.diffie_hellman(&pk).as_bytes())
.unwrap_or([0u8; 32]),
);
// add peer to device
match self.update_ss(&mut peer) {
Some(_) => Err(ConfigError::new("Public key of peer matches the device")),
None => {
self.pk_map.insert(*pk.as_bytes(), peer);
Ok(())
}
}
}
/// Remove a peer by public key
/// To remove public keys, you must create a new machine instance
///
/// # Arguments
///
/// * `pk` - The public key of the peer to remove
///
/// # Returns
///
/// The call might fail if the public key is not found
pub fn remove(&mut self, pk: PublicKey) -> Result<(), ConfigError> {
// take write-lock on receive id table
let mut id_map = self.id_map.write();
// remove the peer
self.pk_map
.remove(pk.as_bytes())
.ok_or(ConfigError::new("Public key not in device"))?;
// pruge the id map (linear scan)
id_map.retain(|_, v| v != pk.as_bytes());
Ok(())
}
/// Add a psk to the peer
///
/// # Arguments
///
/// * `pk` - The public key of the peer
/// * `psk` - The psk to set / unset
///
/// # Returns
///
/// The call might fail if the public key is not found
pub fn set_psk(&mut self, pk: PublicKey, psk: Psk) -> Result<(), ConfigError> {
match self.pk_map.get_mut(pk.as_bytes()) {
Some(mut peer) => {
peer.psk = psk;
Ok(())
}
_ => Err(ConfigError::new("No such public key")),
}
}
/// Return the psk for the peer
///
/// # Arguments
///
/// * `pk` - The public key of the peer
///
/// # Returns
///
/// A 32 byte array holding the PSK
///
/// The call might fail if the public key is not found
pub fn get_psk(&self, pk: &PublicKey) -> Result<Psk, ConfigError> {
match self.pk_map.get(pk.as_bytes()) {
Some(peer) => Ok(peer.psk),
_ => Err(ConfigError::new("No such public key")),
}
}
/// Release an id back to the pool
///
/// # Arguments
///
/// * `id` - The (sender) id to release
pub fn release(&self, id: u32) {
let mut m = self.id_map.write();
debug_assert!(m.contains_key(&id), "Releasing id not allocated");
m.remove(&id);
}
/// Begin a new handshake
///
/// # Arguments
///
/// * `pk` - Public key of peer to initiate handshake for
pub fn begin<R: RngCore + CryptoRng>(
&self,
rng: &mut R,
pk: &PublicKey,
) -> Result<Vec<u8>, HandshakeError> {
match (self.keyst.as_ref(), self.pk_map.get(pk.as_bytes())) {
(_, None) => Err(HandshakeError::UnknownPublicKey),
(None, _) => Err(HandshakeError::UnknownPublicKey),
(Some(keyst), Some(peer)) => {
let local = self.allocate(rng, peer);
let mut msg = Initiation::default();
// create noise part of initation
noise::create_initiation(rng, keyst, peer, local, &mut msg.noise)?;
// add macs to initation
peer.macs
.lock()
.generate(msg.noise.as_bytes(), &mut msg.macs);
Ok(msg.as_bytes().to_owned())
}
}
}
/// Process a handshake message.
///
/// # Arguments
///
/// * `msg` - Byte slice containing the message (untrusted input)
pub fn process<'a, R: RngCore + CryptoRng, S>(
&self,
rng: &mut R, // rng instance to sample randomness from
msg: &[u8], // message buffer
src: Option<&'a S>, // optional source endpoint, set when "under load"
) -> Result<Output, HandshakeError>
where
&'a S: Into<&'a SocketAddr>,
{
// ensure type read in-range
if msg.len() < 4 {
return Err(HandshakeError::InvalidMessageFormat);
}
// obtain reference to key state
// if no key is configured return a noop.
let keyst = match self.keyst.as_ref() {
Some(key) => key,
None => {
return Ok((None, None, None));
}
};
// de-multiplex the message type field
match LittleEndian::read_u32(msg) {
TYPE_INITIATION => {
// parse message
let msg = Initiation::parse(msg)?;
// check mac1 field
keyst.macs.check_mac1(msg.noise.as_bytes(), &msg.macs)?;
// address validation & DoS mitigation
if let Some(src) = src {
// obtain ref to socket addr
let src = src.into();
// check mac2 field
if !keyst.macs.check_mac2(msg.noise.as_bytes(), src, &msg.macs) {
let mut reply = Default::default();
keyst.macs.create_cookie_reply(
rng,
msg.noise.f_sender.get(),
src,
&msg.macs,
&mut reply,
);
return Ok((None, Some(reply.as_bytes().to_owned()), None));
}
// check ratelimiter
if !self.limiter.lock().unwrap().allow(&src.ip()) {
return Err(HandshakeError::RateLimited);
}
}
// consume the initiation
let (peer, st) = noise::consume_initiation(self, keyst, &msg.noise)?;
// allocate new index for response
let local = self.allocate(rng, peer);
// prepare memory for response, TODO: take slice for zero allocation
let mut resp = Response::default();
// create response (release id on error)
let keys =
noise::create_response(rng, peer, local, st, &mut resp.noise).map_err(|e| {
self.release(local);
e
})?;
// add macs to response
peer.macs
.lock()
.generate(resp.noise.as_bytes(), &mut resp.macs);
// return unconfirmed keypair and the response as vector
Ok((Some(peer.pk), Some(resp.as_bytes().to_owned()), Some(keys)))
}
TYPE_RESPONSE => {
let msg = Response::parse(msg)?;
// check mac1 field
keyst.macs.check_mac1(msg.noise.as_bytes(), &msg.macs)?;
// address validation & DoS mitigation
if let Some(src) = src {
// obtain ref to socket addr
let src = src.into();
// check mac2 field
if !keyst.macs.check_mac2(msg.noise.as_bytes(), src, &msg.macs) {
let mut reply = Default::default();
keyst.macs.create_cookie_reply(
rng,
msg.noise.f_sender.get(),
src,
&msg.macs,
&mut reply,
);
return Ok((None, Some(reply.as_bytes().to_owned()), None));
}
// check ratelimiter
if !self.limiter.lock().unwrap().allow(&src.ip()) {
return Err(HandshakeError::RateLimited);
}
}
// consume inner playload
noise::consume_response(self, keyst, &msg.noise)
}
TYPE_COOKIE_REPLY => {
let msg = CookieReply::parse(msg)?;
// lookup peer
let peer = self.lookup_id(msg.f_receiver.get())?;
// validate cookie reply
peer.macs.lock().process(&msg)?;
// this prompts no new message and
// DOES NOT cryptographically verify the peer
Ok((None, None, None))
}
_ => Err(HandshakeError::InvalidMessageFormat),
}
}
// Internal function
//
// Return the peer associated with the public key
pub(crate) fn lookup_pk(&self, pk: &PublicKey) -> Result<&Peer, HandshakeError> {
self.pk_map
.get(pk.as_bytes())
.ok_or(HandshakeError::UnknownPublicKey)
}
// Internal function
//
// Return the peer currently associated with the receiver identifier
pub(crate) fn lookup_id(&self, id: u32) -> Result<&Peer, HandshakeError> {
let im = self.id_map.read();
let pk = im.get(&id).ok_or(HandshakeError::UnknownReceiverId)?;
match self.pk_map.get(pk) {
Some(peer) => Ok(peer),
_ => unreachable!(), // if the id-lookup succeeded, the peer should exist
}
}
// Internal function
//
// Allocated a new receiver identifier for the peer
fn allocate<R: RngCore + CryptoRng>(&self, rng: &mut R, peer: &Peer) -> u32 {
loop {
let id = rng.gen();
// check membership with read lock
if self.id_map.read().contains_key(&id) {
continue;
}
// take write lock and add index
let mut m = self.id_map.write();
if !m.contains_key(&id) {
m.insert(id, *peer.pk.as_bytes());
return id;
}
}
}
}
|