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use spin::RwLock;
use std::collections::HashMap;
use std::net::SocketAddr;
use zerocopy::AsBytes;
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::types::*;
pub struct Device<T> {
pub sk: StaticSecret, // static secret key
pub pk: PublicKey, // static public key
macs: macs::Validator, // validator for the mac fields
pk_map: HashMap<[u8; 32], Peer<T>>, // public key -> peer state
id_map: RwLock<HashMap<u32, [u8; 32]>>, // receiver ids -> public key
}
/* 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<T> Device<T>
where
T: Copy,
{
/// Initialize a new handshake state machine
///
/// # Arguments
///
/// * `sk` - x25519 scalar representing the local private key
pub fn new(sk: StaticSecret) -> Device<T> {
let pk = PublicKey::from(&sk);
Device {
pk,
sk,
macs: macs::Validator::new(pk),
pk_map: HashMap::new(),
id_map: RwLock::new(HashMap::new()),
}
}
/// 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, identifier: T) -> Result<(), ConfigError> {
// check that the pk is not added twice
if let Some(_) = self.pk_map.get(pk.as_bytes()) {
return Err(ConfigError::new("Duplicate public key"));
};
// check that the pk is not that of the device
if *self.pk.as_bytes() == *pk.as_bytes() {
return Err(ConfigError::new(
"Public key corresponds to secret key of interface",
));
}
// map : pk -> new index
self.pk_map.insert(
*pk.as_bytes(),
Peer::new(identifier, pk, self.sk.diffie_hellman(&pk)),
);
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: Option<Psk>) -> Result<(), ConfigError> {
match self.pk_map.get_mut(pk.as_bytes()) {
Some(mut peer) => {
peer.psk = match psk {
Some(v) => v,
None => [0u8; 32],
};
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.pk_map.get(pk.as_bytes()) {
None => Err(HandshakeError::UnknownPublicKey),
Some(peer) => {
let sender = self.allocate(rng, peer);
let mut msg = Initiation::default();
noise::create_initiation(rng, self, peer, sender, &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<R: RngCore + CryptoRng>(
&self,
rng: &mut R,
msg: &[u8], // message buffer
src: Option<&SocketAddr>, // optional source address, set when "under load"
) -> Result<Output<T>, HandshakeError> {
match msg.get(0) {
Some(&TYPE_INITIATION) => {
// parse message
let msg = Initiation::parse(msg)?;
// check mac1 field
self.macs.check_mac1(msg.noise.as_bytes(), &msg.macs)?;
// check mac2 field
if let Some(src) = src {
if !self.macs.check_mac2(msg.noise.as_bytes(), src, &msg.macs) {
let mut reply = Default::default();
self.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));
}
}
// consume the initiation
let (peer, st) = noise::consume_initiation(self, &msg.noise)?;
// allocate new index for response
let sender = 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, sender, st, &mut resp.noise).map_err(
|e| {
self.release(sender);
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.identifier),
Some(resp.as_bytes().to_owned()),
Some(keys),
))
}
Some(&TYPE_RESPONSE) => {
let msg = Response::parse(msg)?;
// check mac1 field
self.macs.check_mac1(msg.noise.as_bytes(), &msg.macs)?;
// check mac2 field
if let Some(src) = src {
if !self.macs.check_mac2(msg.noise.as_bytes(), src, &msg.macs) {
let mut reply = Default::default();
self.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));
}
}
// consume inner playload
noise::consume_response(self, &msg.noise)
}
Some(&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<T>, 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<T>, 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<T>) -> 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;
}
}
}
}
#[cfg(test)]
mod tests {
use super::super::messages::*;
use super::*;
use hex;
use rand::rngs::OsRng;
#[test]
fn handshake() {
// generate new keypairs
let mut rng = OsRng::new().unwrap();
let sk1 = StaticSecret::new(&mut rng);
let pk1 = PublicKey::from(&sk1);
let sk2 = StaticSecret::new(&mut rng);
let pk2 = PublicKey::from(&sk2);
// pick random psk
let mut psk = [0u8; 32];
rng.fill_bytes(&mut psk[..]);
// intialize devices on both ends
let mut dev1 = Device::new(sk1);
let mut dev2 = Device::new(sk2);
dev1.add(pk2, 1337).unwrap();
dev2.add(pk1, 2600).unwrap();
dev1.set_psk(pk2, Some(psk)).unwrap();
dev2.set_psk(pk1, Some(psk)).unwrap();
// do a few handshakes
for i in 0..10 {
println!("handshake : {}", i);
// create initiation
let msg1 = dev1.begin(&mut rng, &pk2).unwrap();
println!("msg1 = {} : {} bytes", hex::encode(&msg1[..]), msg1.len());
println!("msg1 = {:?}", Initiation::parse(&msg1[..]).unwrap());
// process initiation and create response
let (_, msg2, ks_r) = dev2.process(&mut rng, &msg1, None).unwrap();
let ks_r = ks_r.unwrap();
let msg2 = msg2.unwrap();
println!("msg2 = {} : {} bytes", hex::encode(&msg2[..]), msg2.len());
println!("msg2 = {:?}", Response::parse(&msg2[..]).unwrap());
assert!(!ks_r.confirmed, "Responders key-pair is confirmed");
// process response and obtain confirmed key-pair
let (_, msg3, ks_i) = dev1.process(&mut rng, &msg2, None).unwrap();
let ks_i = ks_i.unwrap();
assert!(msg3.is_none(), "Returned message after response");
assert!(ks_i.confirmed, "Initiators key-pair is not confirmed");
assert_eq!(ks_i.send, ks_r.recv, "KeyI.send != KeyR.recv");
assert_eq!(ks_i.recv, ks_r.send, "KeyI.recv != KeyR.send");
dev1.release(ks_i.send.id);
dev2.release(ks_r.send.id);
}
assert_eq!(dev1.get_psk(pk2).unwrap(), psk);
assert_eq!(dev2.get_psk(pk1).unwrap(), psk);
dev1.remove(pk2).unwrap();
dev2.remove(pk1).unwrap();
}
}
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