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//! IPT Establisher
//!
//! Responsible for maintaining and establishing one introduction point.
//!
//! TODO (#1235): move docs from `hssvc-ipt-algorithm.md`
//!
//! See the docs for
//! [`IptManager::idempotently_progress_things_now`](crate::ipt_mgr::IptManager::idempotently_progress_things_now)
//! for details of our algorithm.
use crate::internal_prelude::*;
use tor_cell::relaycell::{
hs::est_intro::{self, EstablishIntroDetails},
msg::IntroEstablished,
};
/// Handle onto the task which is establishing and maintaining one IPT
pub(crate) struct IptEstablisher {
/// A oneshot sender which, when dropped, notifies the running task that it's time to shut
/// down.
_terminate_tx: oneshot::Sender<Void>,
/// Mutable state shared with the Establisher, Reactor, and MsgHandler.
state: Arc<Mutex<EstablisherState>>,
}
/// When the `IptEstablisher` is dropped it is torn down
///
/// Synchronously
///
/// * No rendezvous requests will be accepted
/// that arrived after `Drop::drop` returns.
///
/// Asynchronously
///
/// * Circuits constructed for this IPT are torn down
/// * The `rend_reqs` sink is closed (dropped)
/// * `IptStatusStatus::Faulty` will be indicated
impl Drop for IptEstablisher {
fn drop(&mut self) {
// Make sure no more requests are accepted once this returns.
//
// (Note that if we didn't care about the "no more rendezvous
// requests will be accepted" requirement, we could do away with this
// code and the corresponding check for `RequestDisposition::Shutdown` in
// `IptMsgHandler::handle_msg`.)
self.state.lock().expect("poisoned lock").accepting_requests = RequestDisposition::Shutdown;
// Tell the reactor to shut down... by doing nothing.
//
// (When terminate_tx is dropped, it will send an error to the
// corresponding terminate_rx.)
}
}
/// An error from trying to work with an IptEstablisher.
#[derive(Clone, Debug, thiserror::Error)]
pub(crate) enum IptEstablisherError {
/// We encountered a faulty IPT.
#[error("{0}")]
Ipt(#[from] IptError),
/// The network directory provider is shutting down without giving us the
/// netdir we asked for.
#[error("{0}")]
NetdirProviderShutdown(#[from] NetdirProviderShutdown),
/// We encountered an error while building a circuit to an intro point.
#[error("Unable to build circuit to introduction point")]
BuildCircuit(#[source] tor_circmgr::Error),
/// We encountered an error while building and signing our establish_intro
/// message.
#[error("Unable to construct signed ESTABLISH_INTRO message")]
CreateEstablishIntro(#[source] tor_cell::Error),
/// We encountered a timeout after building the circuit.
#[error("Timeout during ESTABLISH_INTRO handshake.")]
EstablishTimeout,
/// We encountered an error while sending our establish_intro
/// message.
#[error("Unable to send an ESTABLISH_INTRO message")]
SendEstablishIntro(#[source] tor_proto::Error),
/// We did not receive an INTRO_ESTABLISHED message like we wanted; instead, the
/// circuit was closed.
#[error("Circuit closed during INTRO_ESTABLISHED handshake")]
ClosedWithoutAck,
/// We encountered a programming error.
#[error("Internal error")]
Bug(#[from] tor_error::Bug),
}
/// An error caused by a faulty IPT.
#[derive(Clone, Debug, thiserror::Error)]
#[non_exhaustive]
pub enum IptError {
/// When we tried to establish this introduction point, we found that the
/// netdir didn't list it.
///
/// This introduction point is not strictly "faulty", but unlisted in the directory means we
/// can't use the introduction point.
#[error("Introduction point not listed in network directory")]
IntroPointNotListed,
/// We received an invalid INTRO_ESTABLISHED message.
///
/// This is definitely the introduction point's fault: it sent us
/// an authenticated message, but the contents of that message were
/// definitely wrong.
#[error("Got an invalid INTRO_ESTABLISHED message")]
// Eventually, once we expect intro_established extensions, we will make
// sure that they are well-formed.
#[allow(dead_code)]
BadEstablished,
/// We received a message that not a valid part of the introduction-point
/// protocol.
#[error("Invalid message: {0}")]
BadMessage(String),
/// This introduction point has gone too long without a success.
#[error("introduction point has gone too long without a success")]
Timeout,
}
impl tor_error::HasKind for IptEstablisherError {
fn kind(&self) -> tor_error::ErrorKind {
use tor_error::ErrorKind as EK;
use IptEstablisherError as E;
match self {
E::Ipt(e) => e.kind(),
E::NetdirProviderShutdown(e) => e.kind(),
E::BuildCircuit(e) => e.kind(),
E::EstablishTimeout => EK::TorNetworkTimeout,
E::SendEstablishIntro(e) => e.kind(),
E::ClosedWithoutAck => EK::CircuitCollapse,
E::CreateEstablishIntro(_) => EK::Internal,
E::Bug(e) => e.kind(),
}
}
}
impl tor_error::HasKind for IptError {
fn kind(&self) -> tor_error::ErrorKind {
use tor_error::ErrorKind as EK;
use IptError as E;
match self {
E::IntroPointNotListed => EK::TorDirectoryError, // TODO (#1255) Not correct kind.
E::BadEstablished => EK::RemoteProtocolViolation,
E::BadMessage(_) => EK::RemoteProtocolViolation,
E::Timeout => EK::RemoteProtocolViolation, // TODO: this is not necessarily correct
}
}
}
impl IptEstablisherError {
/// Return the underlying [`IptError`] if this error appears to be the introduction point's fault.
///
/// This corresponds to [`IptStatusStatus::Faulty`]`: when we return `Some`,
/// it means that we should try another relay as an introduction point,
/// though we don't necessarily need to give up on this one.
///
/// Note that the intro point may be to blame even if we return `None`;
/// we only return `true` when we are certain that the intro point is
/// unlisted, unusable, or misbehaving.
fn ipt_failure(&self) -> Option<&IptError> {
use IptEstablisherError as IE;
match self {
// If we don't have a netdir, then no intro point is better than any other.
IE::NetdirProviderShutdown(_) => None,
IE::Ipt(e) => Some(e),
// This _might_ be the introduction point's fault, but it might not.
// We can't be certain.
IE::BuildCircuit(_) => None,
IE::EstablishTimeout => None,
IE::ClosedWithoutAck => None,
// These are, most likely, not the introduction point's fault,
// though they might or might not be survivable.
IE::CreateEstablishIntro(_) => None,
IE::SendEstablishIntro(_) => None,
IE::Bug(_) => None,
}
}
}
/// Parameters for an introduction point
///
/// Consumed by `IptEstablisher::new`.
/// Primarily serves as a convenient way to bundle the many arguments required.
///
/// Does not include:
/// * The runtime (which would force this struct to have a type parameter)
/// * The circuit builder (leaving this out makes it possible to use this
/// struct during mock execution, where we don't call `IptEstablisher::new`).
#[derive(Educe)]
#[educe(Debug)]
pub(crate) struct IptParameters {
/// A receiver that we can use to tell us about updates in our configuration.
///
/// Configuration changes may tell us to change our introduction points or build new
/// circuits to them.
//
// TODO (#1209):
//
// We want to make a new introduction circuit if our dos parameters change,
// which means that we should possibly be watching for changes in our
// configuration. Right now, though, we only copy out the configuration
// on startup.
#[educe(Debug(ignore))]
pub(crate) config_rx: watch::Receiver<Arc<OnionServiceConfig>>,
/// A `NetDirProvider` that we'll use to find changes in the network
/// parameters, and to look up information about routers.
#[educe(Debug(ignore))]
pub(crate) netdir_provider: Arc<dyn NetDirProvider>,
/// A shared sender that we'll use to report incoming INTRODUCE2 requests
/// for rendezvous circuits.
#[educe(Debug(ignore))]
pub(crate) introduce_tx: mpsc::Sender<RendRequest>,
/// Opaque local ID for this introduction point.
///
/// This ID does not change within the lifetime of an [`IptEstablisher`].
/// See [`IptLocalId`] for information about what changes would require a
/// new ID (and hence a new `IptEstablisher`).
pub(crate) lid: IptLocalId,
/// Persistent log for INTRODUCE2 requests.
///
/// We use this to record the requests that we see, and to prevent replays.
#[educe(Debug(ignore))]
pub(crate) replay_log: ReplayLog,
/// A set of identifiers for the Relay that we intend to use as the
/// introduction point.
///
/// We use this to identify the relay within a `NetDir`, and to make sure
/// we're connecting to the right introduction point.
pub(crate) target: RelayIds,
/// Keypair used to authenticate and identify ourselves to this introduction
/// point.
///
/// Later, we publish the public component of this keypair in our HsDesc,
/// and clients use it to tell the introduction point which introduction circuit
/// should receive their requests.
///
/// This is the `K_hs_ipt_sid` keypair.
pub(crate) k_sid: Arc<HsIntroPtSessionIdKeypair>,
/// Whether this `IptEstablisher` should begin by accepting requests, or
/// wait to be told that requests are okay.
pub(crate) accepting_requests: RequestDisposition,
/// Keypair used to decrypt INTRODUCE2 requests from clients.
///
/// This is the `K_hss_ntor` keypair, used with the "HS_NTOR" handshake to
/// form a shared key set of keys with the client, and decrypt information
/// about the client's chosen rendezvous point and extensions.
pub(crate) k_ntor: Arc<HsSvcNtorKeypair>,
}
impl IptEstablisher {
/// Try to set up, and maintain, an IPT at `target`.
///
/// Rendezvous requests will be rejected or accepted
/// depending on the value of `accepting_requests`
/// (which must be `Advertised` or `NotAdvertised`).
///
/// Also returns a stream of events that is produced whenever we have a
/// change in the IptStatus for this intro point. Note that this stream is
/// potentially lossy.
///
/// The returned `watch::Receiver` will yield `Faulty` if the IPT
/// establisher is shut down (or crashes).
///
/// When the resulting `IptEstablisher` is dropped, it will cancel all tasks
/// and close all circuits used to establish this introduction point.
pub(crate) fn launch<R: Runtime>(
runtime: &R,
params: IptParameters,
pool: Arc<HsCircPool<R>>,
keymgr: &Arc<KeyMgr>,
) -> Result<(Self, postage::watch::Receiver<IptStatus>), FatalError> {
// This exhaustive deconstruction ensures that we don't
// accidentally forget to handle any of our inputs.
let IptParameters {
config_rx,
netdir_provider,
introduce_tx,
lid,
target,
k_sid,
k_ntor,
accepting_requests,
replay_log,
} = params;
let config = Arc::clone(&config_rx.borrow());
let nickname = config.nickname().clone();
if matches!(accepting_requests, RequestDisposition::Shutdown) {
return Err(bad_api_usage!(
"Tried to create a IptEstablisher that that was already shutting down?"
)
.into());
}
let state = Arc::new(Mutex::new(EstablisherState { accepting_requests }));
let request_context = Arc::new(RendRequestContext {
nickname: nickname.clone(),
keymgr: Arc::clone(keymgr),
kp_hss_ntor: Arc::clone(&k_ntor),
kp_hs_ipt_sid: k_sid.as_ref().as_ref().verifying_key().into(),
filter: config.filter_settings(),
netdir_provider: netdir_provider.clone(),
circ_pool: pool.clone(),
});
let reactor = Reactor {
runtime: runtime.clone(),
nickname,
pool,
netdir_provider,
lid,
target,
k_sid,
introduce_tx,
extensions: EstIntroExtensionSet {
// Updates to this are handled by the IPT manager: when it changes,
// this IPT will be replaced with one with the correct parameters.
dos_params: config.dos_extension()?,
},
state: state.clone(),
request_context,
replay_log: Arc::new(replay_log.into()),
};
let (status_tx, status_rx) = postage::watch::channel_with(IptStatus::new());
let (terminate_tx, mut terminate_rx) = oneshot::channel::<Void>();
let status_tx = DropNotifyWatchSender::new(status_tx);
// Spawn a task to keep the intro established. The task will shut down
// when terminate_tx is dropped.
runtime
.spawn(async move {
futures::select_biased!(
terminated = terminate_rx => {
// Only Err is possible, but the compiler can't tell that.
let oneshot::Canceled = terminated.void_unwrap_err();
}
outcome = reactor.keep_intro_established(status_tx).fuse() => {
warn_report!(outcome.void_unwrap_err(), "Error from intro-point establisher task");
}
);
})
.map_err(|e| FatalError::Spawn {
spawning: "introduction point establisher",
cause: Arc::new(e),
})?;
let establisher = IptEstablisher {
_terminate_tx: terminate_tx,
state,
};
Ok((establisher, status_rx))
}
/// Begin accepting requests from this introduction point.
///
/// If any introduction requests are sent before we have called this method,
/// they are treated as an error and our connection to this introduction
/// point is closed.
pub(crate) fn start_accepting(&self) {
self.state.lock().expect("poisoned lock").accepting_requests =
RequestDisposition::Advertised;
}
}
/// The current status of an introduction point, as defined in
/// `hssvc-ipt-algorithms.md`.
///
/// TODO (#1235) Make that file unneeded.
#[derive(Clone, Debug)]
pub(crate) enum IptStatusStatus {
/// We are (re)establishing our connection to the IPT
///
/// But we don't think there's anything wrong with it.
///
/// The IPT manager should *not* arrange to include this in descriptors.
Establishing,
/// The IPT is established and ready to accept rendezvous requests
///
/// Also contains information about the introduction point
/// necessary for making descriptors,
/// including information from the netdir about the relay
///
/// The IPT manager *should* arrange to include this in descriptors.
Good(GoodIptDetails),
/// We don't have the IPT and it looks like it was the IPT's fault
///
/// This should be used whenever trying another IPT relay is likely to work better;
/// regardless of whether attempts to establish *this* IPT can continue.
///
/// The IPT manager should *not* arrange to include this in descriptors.
/// If this persists, the IPT manager should replace this IPT
/// with a new IPT at a different relay.
Faulty(Option<IptError>),
}
/// Details of a good introduction point
///
/// This struct contains similar information to
/// [`tor_linkspec::verbatim::VerbatimLinkSpecCircTarget`].
/// However, that insists that the contained `T` is a [`CircTarget`],
/// which `<NtorPublicKey>` isn't.
/// And, we don't use this as a circuit target (at least, not here -
/// the client will do so, as a result of us publishing the information).
///
/// See <https://gitlab.torproject.org/tpo/core/arti/-/merge_requests/1559#note_2937974>
#[derive(Clone, Debug, Eq, PartialEq)]
pub(crate) struct GoodIptDetails {
/// The link specifiers to be used in the descriptor
///
/// As obtained and converted from the netdir.
pub(crate) link_specifiers: LinkSpecs,
/// The introduction point relay's ntor key (from the netdir)
pub(crate) ipt_kp_ntor: NtorPublicKey,
}
impl GoodIptDetails {
/// Try to copy out the relevant parts of a CircTarget into a GoodIptDetails.
fn try_from_circ_target(relay: &impl CircTarget) -> Result<Self, IptEstablisherError> {
Ok(Self {
link_specifiers: relay
.linkspecs()
.map_err(into_internal!("Unable to encode relay link specifiers"))?,
ipt_kp_ntor: *relay.ntor_onion_key(),
})
}
}
/// `Err(IptWantsToRetire)` indicates that the IPT Establisher wants to retire this IPT
///
/// This happens when the IPT has had (too) many rendezvous requests.
///
/// This must *not* be used for *errors*, because it will cause the IPT manager to
/// *immediately* start to replace the IPT, regardless of rate limits etc.
#[derive(Clone, Debug, Eq, PartialEq)]
pub(crate) struct IptWantsToRetire;
/// State shared between the IptEstablisher and the Reactor.
struct EstablisherState {
/// True if we are accepting requests right now.
accepting_requests: RequestDisposition,
}
/// Current state of an introduction point; determines what we want to do with
/// any incoming messages.
#[derive(Copy, Clone, Debug)]
pub(crate) enum RequestDisposition {
/// We are not yet advertised: the message handler should complain if it
/// gets any requests and shut down.
NotAdvertised,
/// We are advertised: the message handler should pass along any requests
Advertised,
/// We are shutting down cleanly: the message handler should exit but not complain.
Shutdown,
}
/// The current status of an introduction point.
#[derive(Clone, Debug)]
pub(crate) struct IptStatus {
/// The current state of this introduction point as defined by
/// `hssvc-ipt-algorithms.md`.
///
/// TODO (#1235): Make that file unneeded.
pub(crate) status: IptStatusStatus,
/// The current status of whether this introduction point circuit wants to be
/// retired based on having processed too many requests.
pub(crate) wants_to_retire: Result<(), IptWantsToRetire>,
/// If Some, a time after which all attempts have been unsuccessful.
pub(crate) failing_since: Option<Instant>,
}
/// We declare an introduction point to be faulty if all of the attempts to
/// reach it fail, over this much time.
///
/// TODO: This value is more or less arbitrary; we may want to tune it in the
/// future.
const FAULTY_IPT_THRESHOLD: Duration = Duration::from_secs(15 * 60);
impl IptStatus {
/// Record that we have successfully connected to an introduction point.
fn note_open(&mut self, ipt_details: GoodIptDetails) {
self.status = IptStatusStatus::Good(ipt_details);
self.failing_since = None;
}
/// Record that we are trying to connect to an introduction point.
fn note_attempt(&mut self) {
use IptStatusStatus::*;
self.status = match &self.status {
Establishing | Good(..) => Establishing,
Faulty(e) => Faulty(e.clone()), // We don't change status if we think we're broken.
}
}
/// Record that an error has occurred.
fn note_error(&mut self, err: &IptEstablisherError, now: Instant) {
use IptStatusStatus::*;
let failing_since = *self.failing_since.get_or_insert(now);
#[allow(clippy::if_same_then_else)]
if let Some(ipt_err) = err.ipt_failure() {
// This error always indicates a faulty introduction point.
self.status = Faulty(Some(ipt_err.clone()));
} else if now.saturating_duration_since(failing_since) >= FAULTY_IPT_THRESHOLD {
// This introduction point has gone too long without a success.
self.status = Faulty(Some(IptError::Timeout));
}
}
/// Return an `IptStatus` representing an establisher that has not yet taken
/// any action.
fn new() -> Self {
Self {
status: IptStatusStatus::Establishing,
wants_to_retire: Ok(()),
failing_since: None,
}
}
/// Produce an `IptStatus` representing a shut down or crashed establisher
fn new_terminated() -> Self {
IptStatus {
status: IptStatusStatus::Faulty(None),
// If we're broken, we simply tell the manager that that is the case.
// It will decide for itself whether it wants to replace us.
wants_to_retire: Ok(()),
failing_since: None,
}
}
}
impl Default for IptStatus {
fn default() -> Self {
Self::new()
}
}
impl tor_async_utils::DropNotifyEofSignallable for IptStatus {
fn eof() -> IptStatus {
IptStatus::new_terminated()
}
}
tor_cell::restricted_msg! {
/// An acceptable message to receive from an introduction point.
enum IptMsg : RelayMsg {
IntroEstablished,
Introduce2,
}
}
/// A set of extensions to send with our `ESTABLISH_INTRO` message.
///
/// NOTE: we eventually might want to support unrecognized extensions. But
/// that's potentially troublesome, since the set of extensions we sent might
/// have an affect on how we validate the reply.
#[derive(Clone, Debug)]
pub(crate) struct EstIntroExtensionSet {
/// Parameters related to rate-limiting to prevent denial-of-service
/// attacks.
dos_params: Option<est_intro::DosParams>,
}
/// Implementation structure for the task that implements an IptEstablisher.
struct Reactor<R: Runtime> {
/// A copy of our runtime, used for timeouts and sleeping.
runtime: R,
/// The nickname of the onion service we're running. Used when logging.
nickname: HsNickname,
/// A pool used to create circuits to the introduction point.
pool: Arc<HsCircPool<R>>,
/// A provider used to select the other relays in the circuit.
netdir_provider: Arc<dyn NetDirProvider>,
/// Identifier for the intro point.
lid: IptLocalId,
/// The target introduction point.
target: RelayIds,
/// The keypair to use when establishing the introduction point.
///
/// Knowledge of this private key prevents anybody else from impersonating
/// us to the introduction point.
k_sid: Arc<HsIntroPtSessionIdKeypair>,
/// The extensions to use when establishing the introduction point.
///
/// TODO (#1209): This should be able to change over time as we re-establish
/// the intro point.
extensions: EstIntroExtensionSet,
/// The stream that will receive INTRODUCE2 messages.
introduce_tx: mpsc::Sender<RendRequest>,
/// Mutable state shared with the Establisher, Reactor, and MsgHandler.
state: Arc<Mutex<EstablisherState>>,
/// Context information that we'll need to answer rendezvous requests.
request_context: Arc<RendRequestContext>,
/// Introduction request replay log
///
/// Shared between multiple IPT circuit control message handlers -
/// [`IptMsgHandler`] contains the lock guard.
///
/// Has to be an async mutex since it's locked for a long time,
/// so we mustn't block the async executor thread on it.
replay_log: Arc<futures::lock::Mutex<ReplayLog>>,
}
/// An open session with a single introduction point.
//
// TODO: I've used Ipt and IntroPt in this module; maybe we shouldn't.
pub(crate) struct IntroPtSession {
/// The circuit to the introduction point, on which we're receiving
/// Introduce2 messages.
intro_circ: Arc<ClientCirc>,
}
impl<R: Runtime> Reactor<R> {
/// Run forever, keeping an introduction point established.
#[allow(clippy::blocks_in_conditions)]
async fn keep_intro_established(
&self,
mut status_tx: DropNotifyWatchSender<IptStatus>,
) -> Result<Void, IptEstablisherError> {
let mut retry_delay = tor_basic_utils::retry::RetryDelay::from_msec(1000);
loop {
status_tx.borrow_mut().note_attempt();
match self.establish_intro_once().await {
Ok((session, good_ipt_details)) => {
// TODO (#1239): we need to monitor the netdir for changes to this relay
// Eg,
// - if it becomes unlisted, we should declare the IPT faulty
// (until it perhaps reappears)
//
// TODO SPEC Continuing to use an unlisted relay is dangerous
// It might be malicious. We should withdraw our IPT then,
// and hope that clients find another, working, IPT.
//
// - if it changes its ntor key or link specs,
// we need to update the GoodIptDetails in our status report,
// so that the updated info can make its way to the descriptor
//
// Possibly some this could/should be done by the IPT Manager instead,
// but Diziet thinks it is probably cleanest to do it here.
status_tx.borrow_mut().note_open(good_ipt_details);
debug!(
"{}: Successfully established introduction point with {}",
&self.nickname,
self.target.display_relay_ids().redacted()
);
// Now that we've succeeded, we can stop backing off for our
// next attempt.
retry_delay.reset();
// Wait for the session to be closed.
session.wait_for_close().await;
}
Err(e @ IptEstablisherError::Ipt(IptError::IntroPointNotListed)) => {
// The network directory didn't include this relay. Wait
// until it does.
//
// Note that this `note_error` will necessarily mark the
// ipt as Faulty. That's important, since we may be about to
// wait indefinitely when we call wait_for_netdir_to_list.
status_tx.borrow_mut().note_error(&e, self.runtime.now());
wait_for_netdir_to_list(self.netdir_provider.as_ref(), &self.target).await?;
}
Err(e) => {
status_tx.borrow_mut().note_error(&e, self.runtime.now());
debug_report!(
e,
"{}: Problem establishing introduction point with {}",
&self.nickname,
self.target.display_relay_ids().redacted()
);
let retry_after = retry_delay.next_delay(&mut rand::thread_rng());
self.runtime.sleep(retry_after).await;
}
}
}
}
/// Try, once, to make a circuit to a single relay and establish an introduction
/// point there.
///
/// Does not retry. Does not time out except via `HsCircPool`.
async fn establish_intro_once(
&self,
) -> Result<(IntroPtSession, GoodIptDetails), IptEstablisherError> {
let (protovers, circuit, ipt_details) = {
let netdir = wait_for_netdir(
self.netdir_provider.as_ref(),
tor_netdir::Timeliness::Timely,
)
.await?;
let circ_target = netdir
.by_ids(&self.target)
.ok_or(IptError::IntroPointNotListed)?;
let ipt_details = GoodIptDetails::try_from_circ_target(&circ_target)?;
let kind = tor_circmgr::hspool::HsCircKind::SvcIntro;
let protovers = circ_target.protovers().clone();
let circuit = self
.pool
.get_or_launch_specific(netdir.as_ref(), kind, circ_target)
.await
.map_err(IptEstablisherError::BuildCircuit)?;
// note that netdir is dropped here, to avoid holding on to it any
// longer than necessary.
(protovers, circuit, ipt_details)
};
let intro_pt_hop = circuit
.last_hop_num()
.map_err(into_internal!("Somehow built a circuit with no hops!?"))?;
let establish_intro = {
let ipt_sid_id = (*self.k_sid).as_ref().verifying_key().into();
let mut details = EstablishIntroDetails::new(ipt_sid_id);
if let Some(dos_params) = &self.extensions.dos_params {
// We only send the Dos extension when the relay is known to
// support HsIntro=5.
if protovers.supports_known_subver(tor_protover::ProtoKind::HSIntro, 5) {
details.set_extension_dos(dos_params.clone());
}
}
let circuit_binding_key = circuit
.binding_key(intro_pt_hop)
.ok_or(internal!("No binding key for introduction point!?"))?;
let body: Vec<u8> = details
.sign_and_encode((*self.k_sid).as_ref(), circuit_binding_key.hs_mac())
.map_err(IptEstablisherError::CreateEstablishIntro)?;
// TODO: This is ugly, but it is the sensible way to munge the above
// body into a format that AnyRelayMsgOuter will accept without doing a
// redundant parse step.
//
// One alternative would be allowing start_conversation to take an `impl
// RelayMsg` rather than an AnyRelayMsg.
//
// Or possibly, when we feel like it, we could rename one or more of
// these "Unrecognized"s to Unparsed or Uninterpreted. If we do that, however, we'll
// potentially face breaking changes up and down our crate stack.
AnyRelayMsg::Unrecognized(tor_cell::relaycell::msg::Unrecognized::new(
tor_cell::relaycell::RelayCmd::ESTABLISH_INTRO,
body,
))
};
let (established_tx, established_rx) = oneshot::channel();
// In theory there ought to be only one IptMsgHandler in existence at any one time,
// for any one IptLocalId (ie for any one ReplayLog). However, the teardown
// arrangements are (i) complicated (so might have bugs) and (ii) asynchronous
// (so we need to synchronise). Therefore:
//
// Make sure we don't start writing to the replay log until any previous
// IptMsgHandler has been torn down. (Using an async mutex means we
// don't risk blocking the whole executor even if we have teardown bugs.)
let replay_log = self.replay_log.clone().lock_owned().await;
let handler = IptMsgHandler {
established_tx: Some(established_tx),
introduce_tx: self.introduce_tx.clone(),
state: self.state.clone(),
lid: self.lid,
request_context: self.request_context.clone(),
replay_log,
};
let _conversation = circuit
.start_conversation(Some(establish_intro), handler, intro_pt_hop)
.await
.map_err(IptEstablisherError::SendEstablishIntro)?;
// At this point, we have `await`ed for the Conversation to exist, so we know
// that the message was sent. We have to wait for any actual `established`
// message, though.
let ack_timeout = self
.pool
.estimate_timeout(&tor_circmgr::timeouts::Action::RoundTrip {
length: circuit.n_hops(),
});
let _established: IntroEstablished = self
.runtime
.timeout(ack_timeout, established_rx)
.await
.map_err(|_| IptEstablisherError::EstablishTimeout)?
.map_err(|_| IptEstablisherError::ClosedWithoutAck)??;
// This session will be owned by keep_intro_established(), and dropped
// when the circuit closes, or when the keep_intro_established() future
// is dropped.
let session = IntroPtSession {
intro_circ: circuit,
};
Ok((session, ipt_details))
}
}
impl IntroPtSession {
/// Wait for this introduction point session to be closed.
fn wait_for_close(&self) -> impl Future<Output = ()> {
self.intro_circ.wait_for_close()
}
}
/// MsgHandler type to implement a conversation with an introduction point.
///
/// This, like all MsgHandlers, is installed at the circuit's reactor, and used
/// to handle otherwise unrecognized message types.
struct IptMsgHandler {
/// A oneshot sender used to report our IntroEstablished message.
///
/// If this is None, then we already sent an IntroEstablished and we shouldn't
/// send any more.
established_tx: Option<oneshot::Sender<Result<IntroEstablished, IptEstablisherError>>>,
/// A channel used to report Introduce2 messages.
introduce_tx: mpsc::Sender<RendRequest>,
/// Keys that we'll need to answer the introduction requests.
request_context: Arc<RendRequestContext>,
/// Mutable state shared with the Establisher, Reactor, and MsgHandler.
state: Arc<Mutex<EstablisherState>>,
/// Unique identifier for the introduction point (including the current
/// keys). Used to tag requests.
lid: IptLocalId,
/// A replay log used to detect replayed introduction requests.
replay_log: futures::lock::OwnedMutexGuard<ReplayLog>,
}
impl tor_proto::circuit::MsgHandler for IptMsgHandler {
fn handle_msg(
&mut self,
_conversation: ConversationInHandler<'_, '_, '_>,
any_msg: AnyRelayMsg,
) -> tor_proto::Result<MetaCellDisposition> {
let msg: IptMsg = any_msg.try_into().map_err(|m: AnyRelayMsg| {
if let Some(tx) = self.established_tx.take() {
let _ = tx.send(Err(IptError::BadMessage(format!(
"Invalid message type {}",
m.cmd()
))
.into()));
}
// TODO: It's not completely clear whether CircProto is the right
// type for use in this function (here and elsewhere);
// possibly, we should add a different tor_proto::Error type
// for protocol violations at a higher level than the circuit
// protocol.
//
// For now, however, this error type is fine: it will cause the
// circuit to be shut down, which is what we want.
tor_proto::Error::CircProto(format!(
"Invalid message type {} on introduction circuit",
m.cmd()
))
})?;
if match msg {
IptMsg::IntroEstablished(established) => match self.established_tx.take() {
Some(tx) => {
// TODO: Once we want to enforce any properties on the
// intro_established message (like checking for correct
// extensions) we should do it here.
let established = Ok(established);
tx.send(established).map_err(|_| ())
}
None => {
return Err(tor_proto::Error::CircProto(
"Received a redundant INTRO_ESTABLISHED".into(),
));
}
},
IptMsg::Introduce2(introduce2) => {
if let Some(tx) = self.established_tx.take() {
let _ = tx.send(Err(IptError::BadMessage(
"INTRODUCE2 message without INTRO_ESTABLISHED.".to_string(),
)
.into()));
return Err(tor_proto::Error::CircProto(
"Received an INTRODUCE2 message before INTRO_ESTABLISHED".into(),
));
}
let disp = self.state.lock().expect("poisoned lock").accepting_requests;
match disp {
RequestDisposition::NotAdvertised => {
return Err(tor_proto::Error::CircProto(
"Received an INTRODUCE2 message before we were accepting requests!"
.into(),
))
}
RequestDisposition::Shutdown => return Ok(MetaCellDisposition::CloseCirc),
RequestDisposition::Advertised => {}
}
match self.replay_log.check_for_replay(&introduce2) {
Ok(()) => {}
Err(ReplayError::AlreadySeen) => {
// This is probably a replay, but maybe an accident. We
// just drop the request.
// TODO (#1233): Log that this has occurred, with a rate
// limit. Possibly, we should allow it to fail once or
// twice per circuit before we log, since we expect
// a nonzero false-positive rate.
//
// Note that we should NOT close the circuit in this
// case: the repeated message could come from a hostile
// introduction point trying to do traffic analysis, but
// it could also come from a user trying to make it look
// like the intro point is doing traffic analysis.
return Ok(MetaCellDisposition::Consumed);
}
Err(ReplayError::Log(_)) => {
// Uh-oh! We failed to write the data persistently!
//
// TODO (#1226): We need to decide what to do here. Right
// now we close the circuit, which is wrong.
return Ok(MetaCellDisposition::CloseCirc);
}
}
let request = RendRequest::new(self.lid, introduce2, self.request_context.clone());
let send_outcome = self.introduce_tx.try_send(request);
// We only want to report full-stream problems as errors here.
// Disconnected streams are expected.
let report_outcome = match &send_outcome {
Err(e) if e.is_full() => Err(StreamWasFull {}),
_ => Ok(()),
};
// TODO: someday we might want to start tracking this by
// introduction or service point separately, though we would
// expect their failures to be correlated.
log_ratelim!("sending rendezvous request to handler task"; report_outcome);
match send_outcome {
Ok(()) => Ok(()),
Err(e) => {
if e.is_disconnected() {
// The receiver is disconnected, meaning that
// messages from this intro point are no longer
// wanted. Close the circuit.
Err(())
} else {
// The receiver is full; we have no real option but
// to drop the request like C-tor does when the
// backlog is too large.
//
// See discussion at
// https://gitlab.torproject.org/tpo/core/arti/-/merge_requests/1465#note_2928349
Ok(())
}
}
}
}
} == Err(())
{
// If the above return an error, we failed to send. That means that
// we need to close the circuit, since nobody is listening on the
// other end of the tx.
return Ok(MetaCellDisposition::CloseCirc);
}
Ok(MetaCellDisposition::Consumed)
}
}
/// We failed to send a rendezvous request onto the handler test that should
/// have handled it, because it was not handling requests fast enough.
///
/// (This is a separate type so that we can have it implement Clone.)
#[derive(Clone, Debug, thiserror::Error)]
#[error("Could not send request; stream was full.")]
struct StreamWasFull {}