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//! Code to handle incoming cells on a circuit.
use super::streammap::{ShouldSendEnd, StreamEnt};
use crate::circuit::celltypes::{ClientCircChanMsg, CreateResponse};
use crate::circuit::unique_id::UniqId;
use crate::circuit::{
sendme, streammap, CircParameters, Create2Wrap, CreateFastWrap, CreateHandshakeWrap,
};
use crate::crypto::cell::{
ClientLayer, CryptInit, HopNum, InboundClientCrypt, InboundClientLayer, OutboundClientCrypt,
OutboundClientLayer, RelayCellBody, Tor1RelayCrypto,
};
use crate::util::err::ReactorError;
use crate::{Error, Result};
use std::collections::VecDeque;
use std::marker::PhantomData;
use std::pin::Pin;
use tor_cell::chancell::msg::{ChanMsg, Relay};
use tor_cell::relaycell::msg::{End, RelayMsg, Sendme};
use tor_cell::relaycell::{RelayCell, RelayCmd, StreamId};
use futures::channel::{mpsc, oneshot};
use futures::Sink;
use futures::Stream;
use tor_error::internal;
use std::sync::Arc;
use std::task::{Context, Poll};
use crate::channel::Channel;
use crate::circuit::path;
#[cfg(test)]
use crate::circuit::sendme::CircTag;
use crate::circuit::sendme::StreamSendWindow;
use crate::crypto::handshake::ntor::{NtorClient, NtorPublicKey};
use crate::crypto::handshake::{ClientHandshake, KeyGenerator};
use tor_cell::chancell;
use tor_cell::chancell::{ChanCell, CircId};
use tor_linkspec::{LinkSpec, OwnedChanTarget};
use tor_llcrypto::pk;
use tracing::{debug, trace, warn};
/// Initial value for outbound flow-control window on streams.
pub(super) const SEND_WINDOW_INIT: u16 = 500;
/// Initial value for inbound flow-control window on streams.
pub(super) const RECV_WINDOW_INIT: u16 = 500;
/// Size of the buffer used between the reactor and a `StreamReader`.
///
/// FIXME(eta): We pick 2× the receive window, which is very conservative (we arguably shouldn't
/// get sent more than the receive window anyway!). We might do due to things that
/// don't count towards the window though.
pub(super) const STREAM_READER_BUFFER: usize = (2 * RECV_WINDOW_INIT) as usize;
/// The type of a oneshot channel used to inform reactor users of the result of an operation.
pub(super) type ReactorResultChannel<T> = oneshot::Sender<Result<T>>;
/// A handshake type, to be used when creating circuit hops.
#[derive(Clone, Debug)]
pub(super) enum CircuitHandshake {
/// Use the CREATE_FAST handshake.
CreateFast,
/// Use the ntor handshake.
Ntor {
/// The public key of the relay.
public_key: NtorPublicKey,
/// The first hop's Ed25519 identity, which is verified against
/// the identity held in the circuit's channel.
ed_identity: pk::ed25519::Ed25519Identity,
},
}
/// A message telling the reactor to do something.
#[derive(Debug)]
pub(super) enum CtrlMsg {
/// Create the first hop of this circuit.
Create {
/// A oneshot channel on which we'll receive the creation response.
recv_created: oneshot::Receiver<CreateResponse>,
/// The handshake type to use for the first hop.
handshake: CircuitHandshake,
/// Whether the hop supports authenticated SENDME cells.
/// (And therefore, whether we should require them.)
require_sendme_auth: RequireSendmeAuth,
/// Other parameters relevant for circuit creation.
params: CircParameters,
/// Oneshot channel to notify on completion.
done: ReactorResultChannel<()>,
},
/// Extend a circuit by one hop, using the ntor handshake.
ExtendNtor {
/// The peer that we're extending to.
///
/// Used to extend our record of the circuit's path.
peer_id: OwnedChanTarget,
/// The handshake type to use for this hop.
public_key: NtorPublicKey,
/// Information about how to connect to the relay we're extending to.
linkspecs: Vec<LinkSpec>,
/// Whether the hop supports authenticated SENDME cells.
/// (And therefore, whether we should require them.)
require_sendme_auth: RequireSendmeAuth,
/// Other parameters relevant for circuit extension.
params: CircParameters,
/// Oneshot channel to notify on completion.
done: ReactorResultChannel<()>,
},
/// Begin a stream with the provided hop in this circuit.
///
/// Allocates a stream ID, and sends the provided message to that hop.
BeginStream {
/// The hop number to begin the stream with.
hop_num: HopNum,
/// The message to send.
message: RelayMsg,
/// A channel to send messages on this stream down.
///
/// This sender shouldn't ever block, because we use congestion control and only send
/// SENDME cells once we've read enough out of the other end. If it *does* block, we
/// can assume someone is trying to send us more cells than they should, and abort
/// the stream.
sender: mpsc::Sender<RelayMsg>,
/// A channel to receive messages to send on this stream from.
rx: mpsc::Receiver<RelayMsg>,
/// Oneshot channel to notify on completion, with the allocated stream ID.
done: ReactorResultChannel<StreamId>,
},
/// Send a SENDME cell (used to ask for more data to be sent) on the given stream.
SendSendme {
/// The stream ID to send a SENDME for.
stream_id: StreamId,
/// The hop number the stream is on.
hop_num: HopNum,
},
/// Shut down the reactor.
Shutdown,
/// (tests only) Add a hop to the list of hops on this circuit, with dummy cryptography.
#[cfg(test)]
AddFakeHop {
supports_flowctrl_1: bool,
fwd_lasthop: bool,
rev_lasthop: bool,
params: CircParameters,
done: ReactorResultChannel<()>,
},
/// (tests only) Get the send window and expected tags for a given hop.
#[cfg(test)]
QuerySendWindow {
hop: HopNum,
done: ReactorResultChannel<(u16, Vec<CircTag>)>,
},
/// (tests only) Send a raw relay cell with send_relay_cell().
#[cfg(test)]
SendRelayCell {
hop: HopNum,
early: bool,
cell: RelayCell,
},
}
/// Represents the reactor's view of a single hop.
pub(super) struct CircHop {
/// Map from stream IDs to streams.
///
/// We store this with the reactor instead of the circuit, since the
/// reactor needs it for every incoming cell on a stream, whereas
/// the circuit only needs it when allocating new streams.
map: streammap::StreamMap,
/// Window used to say how many cells we can receive.
recvwindow: sendme::CircRecvWindow,
/// If true, this hop is using an older link protocol and we
/// shouldn't expect good authenticated SENDMEs from it.
auth_sendme_required: RequireSendmeAuth,
/// Window used to say how many cells we can send.
sendwindow: sendme::CircSendWindow,
/// Buffer for messages we can't send to this hop yet due to congestion control.
///
/// Contains the cell to send, and a boolean equivalent to the `early` parameter
/// in `Reactor::send_relay_cell` (as in, whether to send the cell using `RELAY_EARLY`).
///
/// This shouldn't grow unboundedly: we try and pop things off it first before
/// doing things that would result in it growing (and stop before growing it
/// if popping things off it can't be done).
///
/// NOTE: Control messages could potentially add unboundedly to this, although that's
/// not likely to happen (and isn't triggereable from the network, either).
outbound: VecDeque<(bool, RelayCell)>,
}
/// Enumeration to determine whether we require circuit-level SENDME cells to be
/// authenticated.
///
/// (This is an enumeration rather than a boolean to prevent accidental sense
/// inversion.)
#[derive(Copy, Clone, Debug, Eq, PartialEq)]
pub(super) enum RequireSendmeAuth {
/// Sendme authentication is expected from this hop, and therefore is
/// required.
Yes,
/// Sendme authentication is not expected from this hop, and therefore not
/// required.
No,
}
impl RequireSendmeAuth {
/// Create an appropriate [`RequireSendmeAuth`] for a given set of relay
/// subprotocol versions.
//
// TODO(nickm): At some point in the future, once there are no 0.3.5 relays
// on the Tor network, we can safely require authenticated SENDMEs from all
// relays.
//
// At that point, if we have a relay implementation in Rust, it should look
// at the network parameter `SendmeAcceptMinVersion` when deciding whether
// to require authenticated SENDMEs.
pub(super) fn from_protocols(protocols: &tor_protover::Protocols) -> Self {
if protocols.supports_known_subver(tor_protover::ProtoKind::FlowCtrl, 1) {
// The relay supports FlowCtrl=1, and therefore will authenticate.
RequireSendmeAuth::Yes
} else {
RequireSendmeAuth::No
}
}
}
/// An indicator on what we should do when we receive a cell for a circuit.
#[derive(Copy, Clone, Debug, Eq, PartialEq)]
enum CellStatus {
/// The circuit should stay open.
Continue,
/// Perform a clean shutdown on this circuit.
CleanShutdown,
}
impl CircHop {
/// Create a new hop.
pub(super) fn new(auth_sendme_required: RequireSendmeAuth, initial_window: u16) -> Self {
CircHop {
map: streammap::StreamMap::new(),
recvwindow: sendme::CircRecvWindow::new(1000),
auth_sendme_required,
sendwindow: sendme::CircSendWindow::new(initial_window),
outbound: VecDeque::new(),
}
}
}
/// An object that's waiting for a meta cell (one not associated with a stream) in order to make
/// progress.
///
/// # Background
///
/// The `Reactor` can't have async functions that send and receive cells, because its job is to
/// send and receive cells: if one of its functions tried to do that, it would just hang forever.
///
/// To get around this problem, the reactor can send some cells, and then make one of these
/// `MetaCellHandler` objects, which will be run when the reply arrives.
pub(super) trait MetaCellHandler: Send {
/// The hop we're expecting the message to come from. This is compared against the hop
/// from which we actually receive messages, and an error is thrown if the two don't match.
fn expected_hop(&self) -> HopNum;
/// Called when the message we were waiting for arrives.
///
/// Gets a copy of the `Reactor` in order to do anything it likes there.
fn finish(&mut self, msg: RelayMsg, reactor: &mut Reactor) -> Result<()>;
}
/// An object that can extend a circuit by one hop, using the `MetaCellHandler` trait.
///
/// Yes, I know having trait bounds on structs is bad, but in this case it's necessary
/// since we want to be able to use `H::KeyType`.
struct CircuitExtender<H, L, FWD, REV>
where
H: ClientHandshake,
{
/// The peer that we're extending to.
///
/// Used to extend our record of the circuit's path.
peer_id: OwnedChanTarget,
/// Handshake state.
state: Option<H::StateType>,
/// Whether the hop supports authenticated SENDME cells.
/// (And therefore, whether we require them.)
require_sendme_auth: RequireSendmeAuth,
/// Parameters used for this extension.
params: CircParameters,
/// An identifier for logging about this reactor's circuit.
unique_id: UniqId,
/// The hop we're expecting the EXTENDED2 cell to come back from.
expected_hop: HopNum,
/// `PhantomData` used to make the other type parameters required for a circuit extension
/// part of the `struct`, instead of having them be provided during a function call.
///
/// This is done this way so we can implement `MetaCellHandler` for this type, which
/// doesn't include any generic type parameters; we need them to be part of the type
/// so we know what they are for that `impl` block.
phantom: PhantomData<(L, FWD, REV)>,
}
impl<H, L, FWD, REV> CircuitExtender<H, L, FWD, REV>
where
H: ClientHandshake,
H::KeyGen: KeyGenerator,
L: CryptInit + ClientLayer<FWD, REV>,
FWD: OutboundClientLayer + 'static + Send,
REV: InboundClientLayer + 'static + Send,
{
/// Start extending a circuit, sending the necessary EXTEND cell and returning a
/// new `CircuitExtender` to be called when the reply arrives.
///
/// The `handshake_id` is the numeric identifier for what kind of
/// handshake we're doing. The `key` is the relay's onion key that
/// goes along with the handshake, and the `linkspecs` are the
/// link specifiers to include in the EXTEND cell to tell the
/// current last hop which relay to connect to.
#[allow(clippy::too_many_arguments)]
fn begin(
cx: &mut Context<'_>,
peer_id: OwnedChanTarget,
handshake_id: u16,
key: &H::KeyType,
linkspecs: Vec<LinkSpec>,
require_sendme_auth: RequireSendmeAuth,
params: CircParameters,
reactor: &mut Reactor,
) -> Result<Self> {
let mut rng = rand::thread_rng();
let unique_id = reactor.unique_id;
use tor_cell::relaycell::msg::{Body, Extend2};
// Perform the first part of the cryptographic handshake
let (state, msg) = H::client1(&mut rng, key)?;
let n_hops = reactor.crypto_out.n_layers();
let hop = ((n_hops - 1) as u8).into();
debug!(
"{}: Extending circuit to hop {} with {:?}",
unique_id,
n_hops + 1,
linkspecs
);
let extend_msg = Extend2::new(linkspecs, handshake_id, msg);
let cell = RelayCell::new(0.into(), extend_msg.into_message());
// Send the message to the last hop...
reactor.send_relay_cell(
cx, hop, true, // use a RELAY_EARLY cell
cell,
)?;
trace!("{}: waiting for EXTENDED2 cell", unique_id);
// ... and now we wait for a response.
Ok(Self {
peer_id,
state: Some(state),
require_sendme_auth,
params,
unique_id,
expected_hop: hop,
phantom: Default::default(),
})
}
}
impl<H, L, FWD, REV> MetaCellHandler for CircuitExtender<H, L, FWD, REV>
where
H: ClientHandshake,
H::StateType: Send,
H::KeyGen: KeyGenerator,
L: CryptInit + ClientLayer<FWD, REV> + Send,
FWD: OutboundClientLayer + 'static + Send,
REV: InboundClientLayer + 'static + Send,
{
fn expected_hop(&self) -> HopNum {
self.expected_hop
}
fn finish(&mut self, msg: RelayMsg, reactor: &mut Reactor) -> Result<()> {
// Did we get the right response?
if msg.cmd() != RelayCmd::EXTENDED2 {
return Err(Error::CircProto(format!(
"wanted EXTENDED2; got {}",
msg.cmd(),
)));
}
// ???? Do we need to shutdown the circuit for the remaining error
// ???? cases in this function?
let msg = match msg {
RelayMsg::Extended2(e) => e,
_ => {
return Err(Error::from(internal!(
"Message body {:?} didn't match cmd {:?}",
msg,
msg.cmd()
)))
}
};
let relay_handshake = msg.into_body();
trace!(
"{}: Received EXTENDED2 cell; completing handshake.",
self.unique_id
);
// Now perform the second part of the handshake, and see if it
// succeeded.
let keygen = H::client2(
self.state
.take()
.expect("CircuitExtender::finish() called twice"),
relay_handshake,
)?;
let layer = L::construct(keygen)?;
debug!("{}: Handshake complete; circuit extended.", self.unique_id);
// If we get here, it succeeded. Add a new hop to the circuit.
let (layer_fwd, layer_back) = layer.split();
reactor.add_hop(
self.peer_id.clone(),
self.require_sendme_auth,
Box::new(layer_fwd),
Box::new(layer_back),
&self.params,
);
Ok(())
}
}
/// Object to handle incoming cells and background tasks on a circuit
///
/// This type is returned when you finish a circuit; you need to spawn a
/// new task that calls `run()` on it.
#[must_use = "If you don't call run() on a reactor, the circuit won't work."]
pub struct Reactor {
/// Receiver for control messages for this reactor, sent by `ClientCirc` objects.
pub(super) control: mpsc::UnboundedReceiver<CtrlMsg>,
/// Buffer for cells we can't send out the channel yet due to it being full.
///
/// We try and dequeue off this first before doing anything else, ensuring that
/// it cannot grow unboundedly (and if we start having to enqueue things on here after
/// the channel shows backpressure, we stop pulling from receivers that could send here).
///
/// NOTE: Control messages could potentially add unboundedly to this, although that's
/// not likely to happen (and isn't triggereable from the network, either).
pub(super) outbound: VecDeque<ChanCell>,
/// The channel this circuit is using to send cells through.
pub(super) channel: Channel,
/// Input stream, on which we receive ChanMsg objects from this circuit's
/// channel.
// TODO: could use a SPSC channel here instead.
pub(super) input: mpsc::Receiver<ClientCircChanMsg>,
/// The cryptographic state for this circuit for inbound cells.
/// This object is divided into multiple layers, each of which is
/// shared with one hop of the circuit.
pub(super) crypto_in: InboundClientCrypt,
/// The cryptographic state for this circuit for outbound cells.
pub(super) crypto_out: OutboundClientCrypt,
/// List of hops state objects used by the reactor
pub(super) hops: Vec<CircHop>,
/// Shared atomic for the number of hops this circuit has.
pub(super) path: Arc<path::Path>,
/// An identifier for logging about this reactor's circuit.
pub(super) unique_id: UniqId,
/// This circuit's identifier on the upstream channel.
pub(super) channel_id: CircId,
/// A handler for a meta cell, together with a result channel to notify on completion.
pub(super) meta_handler: Option<(Box<dyn MetaCellHandler>, ReactorResultChannel<()>)>,
}
impl Reactor {
/// Launch the reactor, and run until the circuit closes or we
/// encounter an error.
///
/// Once this method returns, the circuit is dead and cannot be
/// used again.
pub async fn run(mut self) -> Result<()> {
trace!("{}: Running circuit reactor", self.unique_id);
let result: Result<()> = loop {
match self.run_once().await {
Ok(()) => (),
Err(ReactorError::Shutdown) => break Ok(()),
Err(ReactorError::Err(e)) => break Err(e),
}
};
debug!("{}: Circuit reactor stopped: {:?}", self.unique_id, result);
result
}
/// Helper for run: doesn't mark the circuit closed on finish. Only
/// processes one cell or control message.
pub(super) async fn run_once(&mut self) -> std::result::Result<(), ReactorError> {
#[allow(clippy::cognitive_complexity)]
let fut = futures::future::poll_fn(|cx| -> Poll<std::result::Result<_, ReactorError>> {
let mut create_message = None;
let mut did_things = false;
// Check whether we've got a control message pending.
if let Poll::Ready(ret) = Pin::new(&mut self.control).poll_next(cx) {
match ret {
None => {
trace!("{}: reactor shutdown due to control drop", self.unique_id);
return Poll::Ready(Err(ReactorError::Shutdown));
}
Some(CtrlMsg::Shutdown) => {
trace!(
"{}: reactor shutdown due to explicit request",
self.unique_id
);
return Poll::Ready(Err(ReactorError::Shutdown));
}
// This message requires actually blocking, so we can't handle it inside
// this nonblocking poll_fn.
Some(x @ CtrlMsg::Create { .. }) => create_message = Some(x),
Some(msg) => {
self.handle_control(cx, msg)?;
did_things = true;
}
}
}
// Check whether we've got an input message pending.
if let Poll::Ready(ret) = Pin::new(&mut self.input).poll_next(cx) {
match ret {
None => {
trace!("{}: reactor shutdown due to input drop", self.unique_id);
return Poll::Ready(Err(ReactorError::Shutdown));
}
Some(cell) => {
if self.handle_cell(cx, cell)? == CellStatus::CleanShutdown {
trace!("{}: reactor shutdown due to handled cell", self.unique_id);
return Poll::Ready(Err(ReactorError::Shutdown));
}
did_things = true;
}
}
}
// Now for the tricky part. We want to grab some relay cells from all of our streams
// and forward them on to the channel, but we need to pay attention to both whether
// the channel can accept cells right now, and whether congestion control allows us
// to send them.
//
// We also have to do somewhat cursed things and call start_send inside this poll_fn,
// since we need to check whether the channel can still receive cells after each one
// that we send.
let mut streams_to_close = vec![];
let mut stream_relaycells = vec![];
// Is the channel ready to receive anything at all?
if self.channel.poll_ready(cx)? {
// (using this as a named block for early returns; not actually a loop)
#[allow(clippy::never_loop)]
'outer: loop {
// First, drain our queue of things we tried to send earlier, but couldn't.
while let Some(msg) = self.outbound.pop_front() {
trace!("{}: sending from enqueued: {:?}", self.unique_id, msg);
Pin::new(&mut self.channel).start_send(msg)?;
// `futures::Sink::start_send` dictates we need to call `poll_ready` before
// each `start_send` call.
if !self.channel.poll_ready(cx)? {
break 'outer;
}
}
// Let's look at our hops, and streams for each hop.
for i in 0..self.hops.len() {
let hop_num = HopNum::from(i as u8);
// If we can, drain our queue of things we tried to send earlier, but
// couldn't due to congestion control.
if self.hops[i].sendwindow.window() > 0 {
'hop: while let Some((early, cell)) = self.hops[i].outbound.pop_front()
{
trace!(
"{}: sending from hop-{}-enqueued: {:?}",
self.unique_id,
i,
cell
);
self.send_relay_cell(cx, hop_num, early, cell)?;
if !self.channel.poll_ready(cx)? {
break 'outer;
}
if self.hops[i].sendwindow.window() == 0 {
break 'hop;
}
}
}
let hop = &mut self.hops[i];
// Look at all of the streams on this hop.
for (id, stream) in hop.map.inner().iter_mut() {
if let StreamEnt::Open {
rx, send_window, ..
} = stream
{
// Do the stream and hop send windows allow us to obtain and
// send something?
//
// FIXME(eta): not everything counts toward congestion control!
if send_window.window() > 0 && hop.sendwindow.window() > 0 {
match Pin::new(rx).poll_next(cx) {
Poll::Ready(Some(m)) => {
stream_relaycells
.push((hop_num, RelayCell::new(*id, m)));
}
Poll::Ready(None) => {
// Stream receiver was dropped; close the stream.
// We can't close it here though due to borrowck; that
// will happen later.
streams_to_close.push((hop_num, *id));
}
Poll::Pending => {}
}
}
}
}
}
break;
}
}
// Close the streams we said we'd close.
for (hopn, id) in streams_to_close {
self.close_stream(cx, hopn, id)?;
did_things = true;
}
// Send messages we said we'd send.
for (hopn, rc) in stream_relaycells {
self.send_relay_cell(cx, hopn, false, rc)?;
did_things = true;
}
let _ = Pin::new(&mut self.channel)
.poll_flush(cx)
.map_err(|_| Error::ChannelClosed)?;
if create_message.is_some() {
Poll::Ready(Ok(create_message))
} else if did_things {
Poll::Ready(Ok(None))
} else {
Poll::Pending
}
});
let create_message = fut.await?;
if let Some(CtrlMsg::Create {
recv_created,
handshake,
require_sendme_auth,
params,
done,
}) = create_message
{
let ret = match handshake {
CircuitHandshake::CreateFast => {
self.create_firsthop_fast(recv_created, ¶ms).await
}
CircuitHandshake::Ntor {
public_key,
ed_identity,
} => {
self.create_firsthop_ntor(
recv_created,
ed_identity,
public_key,
require_sendme_auth,
¶ms,
)
.await
}
};
let _ = done.send(ret); // don't care if sender goes away
futures::future::poll_fn(|cx| -> Poll<Result<()>> {
let _ = Pin::new(&mut self.channel)
.poll_flush(cx)
.map_err(|_| Error::ChannelClosed)?;
Poll::Ready(Ok(()))
})
.await?;
}
Ok(())
}
/// Helper: create the first hop of a circuit.
///
/// This is parameterized not just on the RNG, but a wrapper object to
/// build the right kind of create cell, a handshake object to perform
/// the cryptographic cryptographic handshake, and a layer type to
/// handle relay crypto after this hop is built.
async fn create_impl<L, FWD, REV, H, W>(
&mut self,
recvcreated: oneshot::Receiver<CreateResponse>,
wrap: &W,
key: &H::KeyType,
require_sendme_auth: RequireSendmeAuth,
params: &CircParameters,
) -> Result<()>
where
L: CryptInit + ClientLayer<FWD, REV> + 'static + Send,
FWD: OutboundClientLayer + 'static + Send,
REV: InboundClientLayer + 'static + Send,
H: ClientHandshake,
W: CreateHandshakeWrap,
H::KeyGen: KeyGenerator,
{
// We don't need to shut down the circuit on failure here, since this
// function consumes the PendingClientCirc and only returns
// a ClientCirc on success.
let (state, msg) = {
// done like this because holding the RNG across an await boundary makes the future
// non-Send
let mut rng = rand::thread_rng();
H::client1(&mut rng, key)?
};
let create_cell = wrap.to_chanmsg(msg);
debug!(
"{}: Extending to hop 1 with {}",
self.unique_id,
create_cell.cmd()
);
self.send_msg(create_cell).await?;
let reply = recvcreated
.await
.map_err(|_| Error::CircProto("Circuit closed while waiting".into()))?;
let relay_handshake = wrap.decode_chanmsg(reply)?;
let keygen = H::client2(state, relay_handshake)?;
let layer = L::construct(keygen)?;
debug!("{}: Handshake complete; circuit created.", self.unique_id);
let (layer_fwd, layer_back) = layer.split();
let peer_id = self.channel.target().clone();
self.add_hop(
peer_id,
require_sendme_auth,
Box::new(layer_fwd),
Box::new(layer_back),
params,
);
Ok(())
}
/// Use the (questionable!) CREATE_FAST handshake to connect to the
/// first hop of this circuit.
///
/// There's no authentication in CREATE_FAST,
/// so we don't need to know whom we're connecting to: we're just
/// connecting to whichever relay the channel is for.
async fn create_firsthop_fast(
&mut self,
recvcreated: oneshot::Receiver<CreateResponse>,
params: &CircParameters,
) -> Result<()> {
use crate::crypto::handshake::fast::CreateFastClient;
let wrap = CreateFastWrap;
self.create_impl::<Tor1RelayCrypto, _, _, CreateFastClient, _>(
recvcreated,
&wrap,
&(),
RequireSendmeAuth::No,
params,
)
.await
}
/// Use the ntor handshake to connect to the first hop of this circuit.
///
/// Note that the provided 'target' must match the channel's target,
/// or the handshake will fail.
async fn create_firsthop_ntor(
&mut self,
recvcreated: oneshot::Receiver<CreateResponse>,
ed_identity: pk::ed25519::Ed25519Identity,
pubkey: NtorPublicKey,
require_sendme_auth: RequireSendmeAuth,
params: &CircParameters,
) -> Result<()> {
// Exit now if we have an Ed25519 or RSA identity mismatch.
// FIXME(eta): this is copypasta from Channel::check_match!
if self.channel.peer_rsa_id() != &pubkey.id {
return Err(Error::ChanMismatch(format!(
"Identity {} does not match target {}",
self.channel.peer_rsa_id(),
pubkey.id,
)));
}
if self.channel.peer_ed25519_id() != &ed_identity {
return Err(Error::ChanMismatch(format!(
"Identity {} does not match target {}",
self.channel.peer_ed25519_id(),
ed_identity
)));
}
let wrap = Create2Wrap {
handshake_type: 0x0002, // ntor
};
self.create_impl::<Tor1RelayCrypto, _, _, NtorClient, _>(
recvcreated,
&wrap,
&pubkey,
require_sendme_auth,
params,
)
.await
}
/// Add a hop to the end of this circuit.
fn add_hop(
&mut self,
peer_id: OwnedChanTarget,
require_sendme_auth: RequireSendmeAuth,
fwd: Box<dyn OutboundClientLayer + 'static + Send>,
rev: Box<dyn InboundClientLayer + 'static + Send>,
params: &CircParameters,
) {
let hop = crate::circuit::reactor::CircHop::new(
require_sendme_auth,
params.initial_send_window(),
);
self.hops.push(hop);
self.crypto_in.add_layer(rev);
self.crypto_out.add_layer(fwd);
self.path.push_hop(peer_id);
}
/// Handle a RELAY cell on this circuit with stream ID 0.
fn handle_meta_cell(&mut self, hopnum: HopNum, msg: RelayMsg) -> Result<CellStatus> {
// SENDME cells and TRUNCATED get handled internally by the circuit.
if let RelayMsg::Sendme(s) = msg {
return self.handle_sendme(hopnum, s);
}
if let RelayMsg::Truncated(t) = msg {
let reason = t.reason();
debug!(
"{}: Truncated from hop {}. Reason: {} [{}]",
self.unique_id,
hopnum,
reason.human_str(),
reason
);
return Ok(CellStatus::CleanShutdown);
}
trace!("{}: Received meta-cell {:?}", self.unique_id, msg);
// For all other command types, we'll only get them in response
// to another command, which should have registered a responder.
//
// TODO: that means that service-introduction circuits will need
// a different implementation, but that should be okay. We'll work
// something out.
if let Some((mut handler, done)) = self.meta_handler.take() {
if handler.expected_hop() == hopnum {
// Somebody was waiting for a message -- maybe this message
let ret = handler.finish(msg, self);
trace!(
"{}: meta handler completed with result: {:?}",
self.unique_id,
ret
);
let _ = done.send(ret); // don't care if sender goes away
Ok(CellStatus::Continue)
} else {
// Somebody wanted a message from a different hop! Put this
// one back.
self.meta_handler = Some((handler, done));
Err(Error::CircProto(format!(
"Unexpected {} cell from hop {} on client circuit",
msg.cmd(),
hopnum,
)))
}
} else {
// No need to call shutdown here, since this error will
// propagate to the reactor shut it down.
Err(Error::CircProto(format!(
"Unexpected {} cell on client circuit",
msg.cmd()
)))
}
}
/// Handle a RELAY_SENDME cell on this circuit with stream ID 0.
fn handle_sendme(&mut self, hopnum: HopNum, msg: Sendme) -> Result<CellStatus> {
// No need to call "shutdown" on errors in this function;
// it's called from the reactor task and errors will propagate there.
let hop = self
.hop_mut(hopnum)
.ok_or_else(|| Error::CircProto(format!("Couldn't find {} hop", hopnum)))?;
let auth: Option<[u8; 20]> = match msg.into_tag() {
Some(v) => {
if let Ok(tag) = <[u8; 20]>::try_from(v) {
Some(tag)
} else {
return Err(Error::CircProto("malformed tag on circuit sendme".into()));
}
}
None => {
if hop.auth_sendme_required == RequireSendmeAuth::Yes {
return Err(Error::CircProto("missing tag on circuit sendme".into()));
} else {
None
}
}
};
hop.sendwindow.put(auth)?;
Ok(CellStatus::Continue)
}
/// Send a message onto the circuit's channel (to be called with a `Context`)
///
/// If the channel is ready to accept messages, it will be sent immediately. If not, the message
/// will be enqueued for sending at a later iteration of the reactor loop.
///
/// # Note
///
/// Making use of the enqueuing capabilities of this function is discouraged! You should first
/// check whether the channel is ready to receive messages (`self.channel.poll_ready`), and
/// ideally use this to implement backpressure (such that you do not read from other sources
/// that would send here while you know you're unable to forward the messages on).
fn send_msg_direct(&mut self, cx: &mut Context<'_>, msg: ChanMsg) -> Result<()> {
let cell = ChanCell::new(self.channel_id, msg);
// NOTE(eta): We need to check whether the outbound queue is empty before trying to send:
// if we just checked whether the channel was ready, it'd be possible for
// cells to be sent out of order, since it could transition from not ready to
// ready during one cycle of the reactor!
// (This manifests as a protocol violation.)
if self.outbound.is_empty() && self.channel.poll_ready(cx)? {
Pin::new(&mut self.channel).start_send(cell)?;
} else {
// This has been observed to happen in code that doesn't have bugs in it, simply due
// to the way `Channel`'s `poll_ready` implementation works (it can change due to
// the actions of another thread in between callers of this function checking it,
// and this function checking it).
//
// However, if it's happening a lot more than it used to, that probably indicates
// some caller that's not checking whether the channel is full before calling
// this function.
debug!(
"{}: having to enqueue cell due to backpressure: {:?}",
self.unique_id, cell
);
self.outbound.push_back(cell);
// Ensure we absolutely get scheduled again to clear `self.outbound`.
cx.waker().wake_by_ref();
}
Ok(())
}
/// Wrapper around `send_msg_direct` that uses `futures::future::poll_fn` to get a `Context`.
async fn send_msg(&mut self, msg: ChanMsg) -> Result<()> {
// HACK(eta): technically the closure passed to `poll_fn` is a `FnMut` closure, since it
// can be polled multiple times.
// We're going to return Ready immediately since we're only using `poll_fn` to
// get a `Context`, but the compiler doesn't know that, so use an `Option`
// which we can `take()` in order to move out of it.
// (if we do get polled again this'll panic, but that shouldn't happen!)
let mut msg = Some(msg);
futures::future::poll_fn(|cx| -> Poll<Result<()>> {
self.send_msg_direct(cx, msg.take().expect("poll_fn called twice?"))?;
Poll::Ready(Ok(()))
})
.await?;
Ok(())
}
/// Encode the relay cell `cell`, encrypt it, and send it to the 'hop'th hop.
///
/// Does not check whether the cell is well-formed or reasonable.
fn send_relay_cell(
&mut self,
cx: &mut Context<'_>,
hop: HopNum,
early: bool,
cell: RelayCell,
) -> Result<()> {
let c_t_w = sendme::cell_counts_towards_windows(&cell);
let stream_id = cell.stream_id();
// Check whether the hop send window is empty, if this cell counts towards windows.
// NOTE(eta): It is imperative this happens *before* calling encrypt() below, otherwise
// we'll have cells rejected due to a protocol violation! (Cells have to be
// sent out in the order they were passed to encrypt().)
if c_t_w {
let hop_num = Into::<usize>::into(hop);
let hop = &mut self.hops[hop_num];
if hop.sendwindow.window() == 0 {
// Send window is empty! Push this cell onto the hop's outbound queue, and it'll
// get sent later.
trace!(
"{}: having to use onto hop {} queue for cell: {:?}",
self.unique_id,
hop_num,
cell
);
hop.outbound.push_back((early, cell));
return Ok(());
}
}
let mut body: RelayCellBody = cell.encode(&mut rand::thread_rng())?.into();
let tag = self.crypto_out.encrypt(&mut body, hop)?;
// NOTE(eta): Now that we've encrypted the cell, we *must* either send it or abort
// the whole circuit (e.g. by returning an error).
let msg = chancell::msg::Relay::from_raw(body.into());
let msg = if early {
ChanMsg::RelayEarly(msg)
} else {
ChanMsg::Relay(msg)
};
// If the cell counted towards our sendme window, decrement
// that window, and maybe remember the authentication tag.
if c_t_w {
let hop_num = Into::<usize>::into(hop);
let hop = &mut self.hops[hop_num];
// checked by earlier conditional, so this shouldn't fail
hop.sendwindow.take(tag)?;
if !stream_id.is_zero() {
// We need to decrement the stream-level sendme window.
// Stream data cells should only be dequeued and fed into this function if
// the window is above zero, so we don't need to worry about enqueuing things.
if let Some(window) = hop.map.get_mut(stream_id).and_then(StreamEnt::send_window) {
window.take(&())?;
} else {
warn!(
"{}: sending a relay cell for non-existent or non-open stream with ID {}!",
self.unique_id, stream_id
);
return Err(Error::CircProto(format!(
"tried to send a relay cell on non-open stream {}",
stream_id
)));
}
}
}
self.send_msg_direct(cx, msg)
}
/// Try to install a given meta-cell handler to receive any unusual cells on
/// this circuit, along with a result channel to notify on completion.
fn set_meta_handler(
&mut self,
handler: Box<dyn MetaCellHandler>,
done: ReactorResultChannel<()>,
) -> Result<()> {
if self.meta_handler.is_none() {
self.meta_handler = Some((handler, done));
Ok(())
} else {
Err(Error::from(internal!(
"Tried to install a meta-cell handler before the old one was gone."
)))
}
}
/// Handle a CtrlMsg other than Shutdown.
fn handle_control(&mut self, cx: &mut Context<'_>, msg: CtrlMsg) -> Result<()> {
trace!("{}: reactor received {:?}", self.unique_id, msg);
match msg {
// This is handled earlier, since it requires blocking.
CtrlMsg::Create { .. } => panic!("got a CtrlMsg::Create in handle_control"),
// This is handled earlier, since it requires generating a ReactorError.
CtrlMsg::Shutdown => panic!("got a CtrlMsg::Shutdown in handle_control"),
CtrlMsg::ExtendNtor {
peer_id,
public_key,
linkspecs,
require_sendme_auth,
params,
done,
} => {
match CircuitExtender::<NtorClient, Tor1RelayCrypto, _, _>::begin(
cx,
peer_id,
0x02,
&public_key,
linkspecs,
require_sendme_auth,
params,
self,
) {
Ok(e) => {
self.set_meta_handler(Box::new(e), done)?;
}
Err(e) => {
let _ = done.send(Err(e));
}
};
}
CtrlMsg::BeginStream {
hop_num,
message,
sender,
rx,
done,
} => {
let ret = self.begin_stream(cx, hop_num, message, sender, rx);
let _ = done.send(ret); // don't care if sender goes away
}
CtrlMsg::SendSendme { stream_id, hop_num } => {
let sendme = Sendme::new_empty();
let cell = RelayCell::new(stream_id, sendme.into());
self.send_relay_cell(cx, hop_num, false, cell)?;
}
#[cfg(test)]
CtrlMsg::AddFakeHop {
supports_flowctrl_1,
fwd_lasthop,
rev_lasthop,
params,
done,
} => {
use crate::circuit::test::DummyCrypto;
// This kinds of conversion is okay for testing, but just for testing.
let require_sendme_auth = if supports_flowctrl_1 {
RequireSendmeAuth::Yes
} else {
RequireSendmeAuth::No
};
let dummy_peer_id = OwnedChanTarget::new(vec![], [4; 32].into(), [5; 20].into());
let fwd = Box::new(DummyCrypto::new(fwd_lasthop));
let rev = Box::new(DummyCrypto::new(rev_lasthop));
self.add_hop(dummy_peer_id, require_sendme_auth, fwd, rev, ¶ms);
let _ = done.send(Ok(()));
}
#[cfg(test)]
CtrlMsg::QuerySendWindow { hop, done } => {
let _ = done.send(if let Some(hop) = self.hop_mut(hop) {
Ok(hop.sendwindow.window_and_expected_tags())
} else {
Err(Error::from(internal!(
"received QuerySendWindow for unknown hop {:?}",
hop
)))
});
}
#[cfg(test)]
CtrlMsg::SendRelayCell { hop, early, cell } => {
self.send_relay_cell(cx, hop, early, cell)?;
}
}
Ok(())
}
/// Start a stream. Creates an entry in the stream map with the given channels, and sends the
/// `message` to the provided hop.
fn begin_stream(
&mut self,
cx: &mut Context<'_>,
hopnum: HopNum,
message: RelayMsg,
sender: mpsc::Sender<RelayMsg>,
rx: mpsc::Receiver<RelayMsg>,
) -> Result<StreamId> {
let hop = self
.hop_mut(hopnum)
.ok_or_else(|| Error::from(internal!("No such hop {:?}", hopnum)))?;
let send_window = StreamSendWindow::new(SEND_WINDOW_INIT);
let r = hop.map.add_ent(sender, rx, send_window)?;
let cell = RelayCell::new(r, message);
self.send_relay_cell(cx, hopnum, false, cell)?;
Ok(r)
}
/// Close the stream associated with `id` because the stream was
/// dropped.
///
/// If we have not already received an END cell on this stream, send one.
fn close_stream(&mut self, cx: &mut Context<'_>, hopnum: HopNum, id: StreamId) -> Result<()> {
// Mark the stream as closing.
let hop = self.hop_mut(hopnum).ok_or_else(|| {
Error::from(internal!(
"Tried to close a stream on a hop {:?} that wasn't there?",
hopnum
))
})?;
let should_send_end = hop.map.terminate(id)?;
trace!(
"{}: Ending stream {}; should_send_end={:?}",
self.unique_id,
id,
should_send_end
);
// TODO: I am about 80% sure that we only send an END cell if
// we didn't already get an END cell. But I should double-check!
if should_send_end == ShouldSendEnd::Send {
let end_cell = RelayCell::new(id, End::new_misc().into());
self.send_relay_cell(cx, hopnum, false, end_cell)?;
}
Ok(())
}
/// Helper: process a cell on a channel. Most cells get ignored
/// or rejected; a few get delivered to circuits.
///
/// Return true if we should exit.
fn handle_cell(&mut self, cx: &mut Context<'_>, cell: ClientCircChanMsg) -> Result<CellStatus> {
trace!("{}: handling cell: {:?}", self.unique_id, cell);
use ClientCircChanMsg::*;
match cell {
Relay(r) => Ok(self.handle_relay_cell(cx, r)?),
Destroy(d) => {
let reason = d.reason();
debug!(
"{}: Received DESTROY cell. Reason: {} [{}]",
self.unique_id,
reason.human_str(),
reason
);
self.handle_destroy_cell()?;
Ok(CellStatus::CleanShutdown)
}
}
}
/// React to a Relay or RelayEarly cell.
fn handle_relay_cell(&mut self, cx: &mut Context<'_>, cell: Relay) -> Result<CellStatus> {
let mut body = cell.into_relay_body().into();
// Decrypt the cell. If it's recognized, then find the
// corresponding hop.
let (hopnum, tag) = self.crypto_in.decrypt(&mut body)?;
// Make a copy of the authentication tag. TODO: I'd rather not
// copy it, but I don't see a way around it right now.
let tag = {
let mut tag_copy = [0_u8; 20];
// TODO(nickm): This could crash if the tag length changes. We'll
// have to refactor it then.
tag_copy.copy_from_slice(tag);
tag_copy
};
// Decode the cell.
let msg = RelayCell::decode(body.into())?;
let c_t_w = sendme::cell_counts_towards_windows(&msg);
// Decrement the circuit sendme windows, and see if we need to
// send a sendme cell.
let send_circ_sendme = if c_t_w {
let hop = self
.hop_mut(hopnum)
.ok_or_else(|| Error::CircProto("Sendme from nonexistent hop".into()))?;
hop.recvwindow.take()?
} else {
false
};
// If we do need to send a circuit-level SENDME cell, do so.
if send_circ_sendme {
// This always sends a V1 (tagged) sendme cell, and thereby assumes
// that SendmeEmitMinVersion is no more than 1. If the authorities
// every increase that parameter to a higher number, this will
// become incorrect. (Higher numbers are not currently defined.)
let sendme = Sendme::new_tag(tag);
let cell = RelayCell::new(0.into(), sendme.into());
self.send_relay_cell(cx, hopnum, false, cell)?;
self.hop_mut(hopnum)
.ok_or_else(|| {
Error::from(internal!(
"Trying to send SENDME to nonexistent hop {:?}",
hopnum
))
})?
.recvwindow
.put();
}
// Break the message apart into its streamID and message.
let (streamid, msg) = msg.into_streamid_and_msg();
// If this cell wants/refuses to have a Stream ID, does it
// have/not have one?
if !msg.cmd().accepts_streamid_val(streamid) {
return Err(Error::CircProto(format!(
"Invalid stream ID {} for relay command {}",
streamid,
msg.cmd()
)));
}
// If this has a reasonable streamID value of 0, it's a meta cell,
// not meant for a particular stream.
if streamid.is_zero() {
return self.handle_meta_cell(hopnum, msg);
}
let hop = self
.hop_mut(hopnum)
.ok_or_else(|| Error::CircProto("Cell from nonexistent hop!".into()))?;
match hop.map.get_mut(streamid) {
Some(StreamEnt::Open {
sink,
send_window,
dropped,
ref mut received_connected,
..
}) => {
// The stream for this message exists, and is open.
if let RelayMsg::Sendme(_) = msg {
// We need to handle sendmes here, not in the stream's
// recv() method, or else we'd never notice them if the
// stream isn't reading.
send_window.put(Some(()))?;
return Ok(CellStatus::Continue);
}
if matches!(msg, RelayMsg::Connected(_)) {
// Remember that we've received a Connected cell, and can't get another,
// even if we become a HalfStream. (This rule is enforced separately at
// DataStreamReader.)
*received_connected = true;
}
// Remember whether this was an end cell: if so we should
// close the stream.
let is_end_cell = matches!(msg, RelayMsg::End(_));
// TODO: Add a wrapper type here to reject cells that should
// never go to a client, like BEGIN.
if let Err(e) = sink.try_send(msg) {
if e.is_full() {
// If we get here, we either have a logic bug (!), or an attacker
// is sending us more cells than we asked for via congestion control.
return Err(Error::CircProto(format!(
"Stream sink would block; received too many cells on stream ID {}",
streamid,
)));
}
if e.is_disconnected() && c_t_w {
// the other side of the stream has gone away; remember
// that we received a cell that we couldn't queue for it.
//
// Later this value will be recorded in a half-stream.
*dropped += 1;
}
}
if is_end_cell {
hop.map.end_received(streamid)?;
}
}
Some(StreamEnt::EndSent(halfstream)) => {
// We sent an end but maybe the other side hasn't heard.
if matches!(msg, RelayMsg::End(_)) {
hop.map.end_received(streamid)?;
} else {
halfstream.handle_msg(&msg)?;
}
}
_ => {
// No stream wants this message.
return Err(Error::CircProto(
"Cell received on nonexistent stream!?".into(),
));
}
}
Ok(CellStatus::Continue)
}
/// Helper: process a destroy cell.
#[allow(clippy::unnecessary_wraps)]
fn handle_destroy_cell(&mut self) -> Result<()> {
// I think there is nothing more to do here.
Ok(())
}
/// Return the hop corresponding to `hopnum`, if there is one.
fn hop_mut(&mut self, hopnum: HopNum) -> Option<&mut CircHop> {
self.hops.get_mut(Into::<usize>::into(hopnum))
}
}
impl Drop for Reactor {
fn drop(&mut self) {
let _ = self.channel.close_circuit(self.channel_id);
}
}
#[cfg(test)]
mod test {}