1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157

// Copyright 2021 Protocol Labs.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the "Software"),
// to deal in the Software without restriction, including without limitation
// the rights to use, copy, modify, merge, publish, distribute, sublicense,
// and/or sell copies of the Software, and to permit persons to whom the
// Software is furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.

use std::io;
use std::time::Duration;

use asynchronous_codec::{Framed, FramedParts};
use bytes::Bytes;
use futures::prelude::*;
use thiserror::Error;

use libp2p_identity::PeerId;
use libp2p_swarm::Stream;

use crate::protocol::MAX_MESSAGE_SIZE;
use crate::{proto, STOP_PROTOCOL_NAME};

#[derive(Debug, Error)]
pub enum Error {
    #[error("Remote reported resource limit exceeded.")]
    ResourceLimitExceeded,
    #[error("Remote reported permission denied.")]
    PermissionDenied,
    #[error("Remote does not support the `{STOP_PROTOCOL_NAME}` protocol")]
    Unsupported,
    #[error("IO error")]
    Io(#[source] io::Error),
    #[error("Protocol error")]
    Protocol(#[from] ProtocolViolation),
}

impl Error {
    pub(crate) fn to_status(&self) -> proto::Status {
        match self {
            Error::ResourceLimitExceeded => proto::Status::RESOURCE_LIMIT_EXCEEDED,
            Error::PermissionDenied => proto::Status::PERMISSION_DENIED,
            Error::Unsupported => proto::Status::CONNECTION_FAILED,
            Error::Io(_) => proto::Status::CONNECTION_FAILED,
            Error::Protocol(
                ProtocolViolation::UnexpectedStatus(_) | ProtocolViolation::UnexpectedTypeConnect,
            ) => proto::Status::UNEXPECTED_MESSAGE,
            Error::Protocol(_) => proto::Status::MALFORMED_MESSAGE,
        }
    }
}

/// Depicts all forms of protocol violations.
#[derive(Debug, Error)]
pub enum ProtocolViolation {
    #[error(transparent)]
    Codec(#[from] quick_protobuf_codec::Error),
    #[error("Expected 'status' field to be set.")]
    MissingStatusField,
    #[error("Unexpected message type 'connect'")]
    UnexpectedTypeConnect,
    #[error("Unexpected message status '{0:?}'")]
    UnexpectedStatus(proto::Status),
}

impl From<quick_protobuf_codec::Error> for Error {
    fn from(e: quick_protobuf_codec::Error) -> Self {
        Error::Protocol(ProtocolViolation::Codec(e))
    }
}

/// Attempts to _connect_ to a peer via the given stream.
pub(crate) async fn connect(
    io: Stream,
    src_peer_id: PeerId,
    max_duration: Duration,
    max_bytes: u64,
) -> Result<Circuit, Error> {
    let msg = proto::StopMessage {
        type_pb: proto::StopMessageType::CONNECT,
        peer: Some(proto::Peer {
            id: src_peer_id.to_bytes(),
            addrs: vec![],
        }),
        limit: Some(proto::Limit {
            duration: Some(
                max_duration
                    .as_secs()
                    .try_into()
                    .expect("`max_circuit_duration` not to exceed `u32::MAX`."),
            ),
            data: Some(max_bytes),
        }),
        status: None,
    };

    let mut substream = Framed::new(io, quick_protobuf_codec::Codec::new(MAX_MESSAGE_SIZE));

    substream.send(msg).await?;

    let proto::StopMessage {
        type_pb,
        peer: _,
        limit: _,
        status,
    } = substream
        .next()
        .await
        .ok_or(Error::Io(io::ErrorKind::UnexpectedEof.into()))??;

    match type_pb {
        proto::StopMessageType::CONNECT => {
            return Err(Error::Protocol(ProtocolViolation::UnexpectedTypeConnect))
        }
        proto::StopMessageType::STATUS => {}
    }

    match status {
        Some(proto::Status::OK) => {}
        Some(proto::Status::RESOURCE_LIMIT_EXCEEDED) => return Err(Error::ResourceLimitExceeded),
        Some(proto::Status::PERMISSION_DENIED) => return Err(Error::PermissionDenied),
        Some(s) => return Err(Error::Protocol(ProtocolViolation::UnexpectedStatus(s))),
        None => return Err(Error::Protocol(ProtocolViolation::MissingStatusField)),
    }

    let FramedParts {
        io,
        read_buffer,
        write_buffer,
        ..
    } = substream.into_parts();
    assert!(
        write_buffer.is_empty(),
        "Expect a flushed Framed to have an empty write buffer."
    );

    Ok(Circuit {
        dst_stream: io,
        dst_pending_data: read_buffer.freeze(),
    })
}

pub(crate) struct Circuit {
    pub(crate) dst_stream: Stream,
    pub(crate) dst_pending_data: Bytes,
}