//! Handler for CREATE* cells.

use crate::FlowCtrlParameters;

use crate::ccparams::{

    Algorithm, AlgorithmDiscriminants, CongestionControlParams, CongestionWindowParams,

    FixedWindowParams, RoundTripEstimatorParams, VegasParams,

};

use crate::channel::Channel;

use crate::circuit::CircuitRxSender;

use crate::circuit::UniqId;

use crate::circuit::celltypes::{CreateRequest, CreateResponse};

use crate::circuit::circhop::{HopNegotiationType, HopSettings};

use crate::client::circuit::CircParameters;

use crate::client::circuit::padding::PaddingController;

use crate::crypto::binding::CircuitBinding;

use crate::crypto::cell::CryptInit as _;

use crate::crypto::cell::{InboundRelayLayer, OutboundRelayLayer, RelayLayer, tor1};

use crate::crypto::handshake::RelayHandshakeError;

use crate::crypto::handshake::ServerHandshake as _;

use crate::crypto::handshake::fast::CreateFastServer;

use crate::crypto::handshake::ntor::{NtorSecretKey, NtorServer};

use crate::memquota::SpecificAccount as _;

use crate::memquota::{ChannelAccount, CircuitAccount};

use crate::relay::channel_provider::ChannelProvider;

use crate::relay::reactor::Reactor;

use crate::relay::{IncomingStreamRequestFilter, RelayCirc};

use smallvec::SmallVec;

use std::sync::{Arc, RwLock, Weak};

use tor_cell::chancell::ChanMsg as _;

use tor_cell::chancell::CircId;

use tor_cell::chancell::msg::{

    CreateFast, Created2, CreatedFast, Destroy, DestroyReason, HandshakeType,

};

use tor_cell::relaycell::RelayCmd;

use tor_error::{Bug, ErrorKind, HasKind, debug_report, internal, into_internal};

use tor_linkspec::OwnedChanTarget;

use tor_llcrypto::cipher::aes::Aes128Ctr;

use tor_llcrypto::d::Sha1;

use tor_llcrypto::pk::ed25519::Ed25519Identity;

use tor_llcrypto::pk::rsa::RsaIdentity;

use tor_memquota::mq_queue::ChannelSpec as _;

use tor_memquota::mq_queue::MpscSpec;

use tor_relay_crypto::pk::{RelayNtorKeypair, RelayNtorKeys};

use tor_rtcompat::SpawnExt as _;

use tor_rtcompat::{DynTimeProvider, Runtime};

use tracing::warn;

/// Everything needed to handle CREATE* messages on channels.

#[derive(derive_more::Debug)]

pub struct CreateRequestHandler {

    /// Something that can launch channels. Typically the `ChanMgr`.

    chan_provider: Weak<dyn ChannelProvider<BuildSpec = OwnedChanTarget> + Send + Sync>,

    /// Circuit-related network parameters.

    circ_net_params: RwLock<CircNetParameters>,

    /// The circuit extension keys.

    #[debug(skip)]

    ntor_keys: RwLock<RelayNtorKeys>,

    /// An [`IncomingStreamRequestFilter`] factory for checking whether the user wants

    /// this request, or wants to reject it immediately.

    ///

    /// Used for obtaining a current [`IncomingStreamRequestFilter`]

    /// for building a circuit reactor.

    //

    // TODO(relay): it's likely this will end up changing quite a bit once we start

    // figuring out exactly how the config/reconfigure() logic and IncomingStreamRequestFilter

    // should function for relays.

    #[debug(skip)]

    incoming_filter_factory: Box<dyn IncomingStreamRequestFilterFactory + Send + Sync>,

    /// The allowed incoming stream commands.

    ///

    /// Used for rejecting BEGIN and RESOLVE if we are not configured to be an exit.

    ///

    // TODO(relay): we might use this for rejecting BEGIN_DIR too,

    // if we decide to allow relays to opt out of being dir mirrors.

    // See https://gitlab.torproject.org/tpo/core/arti/-/merge_requests/4107/diffs#note_3426447

    allowed_stream_cmds: SmallVec<[RelayCmd; 3]>,

}

impl CreateRequestHandler {

    /// Build a new [`CreateRequestHandler`].

    /// Update the circuit parameters from a network consensus.

    /// Update the handler with a new set of circuit extension keys.

    ///

    /// This is called periodically by the relay key rotation task.

    /// Handle a CREATE* cell.

    ///

    /// This intentionally does not return a [`crate::Error`] so that we don't accidentally shut

    /// down the channel reactor when we really should be returning a DESTROY. Shutting down a

    /// channel may cause us to leak information about paths of circuits travelling through this

    /// relay. This is especially important here since we're handling data that is controllable from

    /// the other end of the circuit.

    #[allow(clippy::too_many_arguments)]

        );

                // TODO(relay): The log messages throughout could be very noisy, so should have rate limiting.

                // `tor-spec/tearing-down-circuits.md`:

                //

                // > Implementations SHOULD always use the NONE reason to avoid side channels: [...]

            }

        }

    /// See [`Self::handle_create`].

    #[allow(clippy::too_many_arguments)]

        // Perform the handshake crypto and build the response.

                }

            },

        };

        // We use a large mpsc queue here since a circuit should never block the channel,

        // and we hope that memquota will help us if an attacker intentionally fills this buffer.

        // We use `10_000_000` since `usize::MAX` causes `futures::channel::mpsc` to panic.

        // TODO(relay): We should switch to an unbounded queue, but the circuit reactor is expecting

        // a bounded queue.

        // TODO(relay): Do we really want a client padding machine here?

        // Upgrade the channel provider, which in practice is the `ChanMgr` so this should not fail.

        };

        // Create an IncomingStreamRequestFilter for this circuit.

        // This will get applied to every stream request (BEGIN, BEGIN_DIR, RESOLVE)

        // arriving on the circuit.

        //

        // Note: once built, a circuit reactor's IncomingStreamRequestFilter cannot be changed

        // (it's fixed for the entire duration of the circuit).

        // Build the relay circuit reactor.

        )

        // TODO(relay): send the incoming_streams stream to the handler in arti-relay

        // Start the reactor in a task.

                }

            }

    /// The handshake code for a CREATE_FAST request.

        // TODO(relay): We might want to offload this to a CPU worker in the future.

            // The CREATE_FAST handshake doesn't accept or return extensions,

            // so this `AuxDataReply` is a no-op.

            // The CREATE_FAST handshake doesn't use any keys.

        // TODO(relay): I don't think that this is the right way to do this. It works for

        // CREATE_FAST, but we might want to rethink it for CREATE2.

    /// The handshake code for a CREATE2 ntor (non-v3) request.

        // TODO(relay): We might want to offload this to a CPU worker in the future.

            // The ntor (non-v3) handshake doesn't accept or return extensions,

            // so this `AuxDataReply` is a no-op.

        // TODO(relay): I don't think that this is the right way to do this. It works for

        // ntor, but won't work well for ntor-v3.

    /// The handshake code for a CREATE2 ntor-v3 request.

    /// Helper to get the ntor keypairs after some transformation `map`.

    ///

    /// The `map` transformation must be fast since it blocks a read lock.

    /// The returned keys are sorted with the most recent key first.

    ///

    /// It would be nice if this just returned an iterator,

    /// but the read lock prevents this.

}

/// Helper function to split a `RelayLayer` into forward and backward type-erased trait objects.

{

/// An error that occurred while handling a CREATE* request.

#[derive(Debug, thiserror::Error)]

enum HandleCreateError {

    /// Circuit relay handshake failed.

    #[error("Circuit relay handshake failed")]

    Handshake(#[from] RelayHandshakeError),

    /// The requested handshake type is unsupported.

    #[error("Unsupported handshake type {0}")]

    Create2HandshakeType(HandshakeType),

    /// A memquota error.

    #[error("Memquota error")]

    Memquota(#[from] tor_memquota::Error),

    /// Error when spawning a task.

    #[error("Runtime task spawn error")]

    Spawn(#[from] futures::task::SpawnError),

    /// An internal error.

    ///

    /// Note that other variants (such as `Handshake` containing a [`RelayHandshakeError`])

    /// may themselves contain internal errors.

    #[error("Internal error")]

    Internal(#[from] tor_error::Bug),

}

impl HasKind for HandleCreateError {

        }

}

/// The components of a completed CREATE* handshake.

struct CompletedHandshakeComponents {

    /// The message to send in response.

    response: CreateResponse,

    /// The negotiated hop settings.

    hop_settings: HopSettings,

    /// Outbound onion crypto.

    crypto_out: Box<dyn OutboundRelayLayer + Send>,

    /// Inbound onion crypto.

    crypto_in: Box<dyn InboundRelayLayer + Send>,

}

/// A collection of objects built for a new relay circuit.

pub(crate) struct RelayCircComponents {

    /// The relay circuit handle.

    pub(crate) circ: Arc<RelayCirc>,

    /// Used to send data from the channel to the circuit reactor.

    pub(crate) sender: CircuitRxSender,

    /// The circuit's padding controller.

    pub(crate) padding_ctrl: PaddingController,

}

/// Congestion control network parameters.

#[derive(Debug, Clone)]

#[allow(clippy::exhaustive_structs)]

pub struct CongestionControlNetParams {

    /// Fixed-window algorithm parameters.

    pub fixed_window: FixedWindowParams,

    /// Vegas algorithm parameters for exit circuits.

    // NOTE: In this module we are handling CREATE* cells,

    // which only happens for non-hs circuits.

    // So we don't need to store the vegas hs parameters here.

    pub vegas_exit: VegasParams,

    /// Congestion window parameters.

    pub cwnd: CongestionWindowParams,

    /// RTT calculation parameters.

    pub rtt: RoundTripEstimatorParams,

    /// Flow control parameters to use for all streams on this circuit.

    pub flow_ctrl: FlowCtrlParameters,

}

impl CongestionControlNetParams {

    #[cfg(test)]

    // These have been copied from C-tor.

}

/// Network consensus parameters for handling incoming circuits.

///

/// Unlike `CircParameters`,

/// this is unopinionated and contains all relevant consensus parameters,

/// which is needed when handling an incoming CREATE* request where the

/// circuit origin chooses the type/settings

/// (for example congestion control type) of the circuit.

#[derive(Debug, Clone)]

#[allow(clippy::exhaustive_structs)]

pub struct CircNetParameters {

    /// Whether we should include ed25519 identities when we send EXTEND2 cells.

    pub extend_by_ed25519_id: bool,

    /// Congestion control network parameters.

    pub cc: CongestionControlNetParams,

}

impl CircNetParameters {

    /// Convert the [`CircNetParameters`] into a [`CircParameters`].

    ///

    /// We expect the circuit creation handshake to know what congestion control algorithm was

    /// negotiated, and provide that as `algorithm`.

    //

    // We disable `unused` warnings at the root of tor-proto,

    // but it's nice to have here so we re-enable it.

    #[warn(unused)]

        // Unpack everything to make sure that we aren't missing anything

        // (otherwise clippy would warn).

        let Self {

            cc:

                CongestionControlNetParams {

                },

        };

        // TODO(arti#2442): The builder pattern here seems like a footgun.

}

/// An [`IncomingStreamRequestFilter`] factory for building [`IncomingStreamRequestFilter`]s.

///

/// Each time a new circuit is opened, the [`CreateRequestHandler`] calls

/// [`IncomingStreamRequestFilterFactory::current_filter`] to build

/// an [`IncomingStreamRequestFilter`] for the circuit.

pub trait IncomingStreamRequestFilterFactory {

    /// Return the [`IncomingStreamRequestFilter`] to apply to the incoming stream requests

    /// arriving on a circuit.

    fn current_filter(&self) -> Box<dyn IncomingStreamRequestFilter>;

}

impl<F> IncomingStreamRequestFilterFactory for F

where

    F: Fn() -> Box<dyn IncomingStreamRequestFilter>,

{

}