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
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
// Copyright 2020 The Matrix.org Foundation C.I.C.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

mod machine;

use std::{
    collections::{BTreeMap, BTreeSet},
    sync::{Arc, RwLock as StdRwLock},
};

pub(crate) use machine::GossipMachine;
use ruma::{
    events::{
        room_key_request::{Action, ToDeviceRoomKeyRequestEventContent},
        secret::request::{
            RequestAction, SecretName, ToDeviceSecretRequestEvent as SecretRequestEvent,
            ToDeviceSecretRequestEventContent as SecretRequestEventContent,
        },
        AnyToDeviceEventContent, ToDeviceEventType,
    },
    serde::Raw,
    to_device::DeviceIdOrAllDevices,
    DeviceId, OwnedDeviceId, OwnedTransactionId, OwnedUserId, TransactionId, UserId,
};
use serde::{Deserialize, Serialize};

use crate::{
    requests::{OutgoingRequest, ToDeviceRequest},
    types::events::{
        olm_v1::DecryptedSecretSendEvent,
        room_key_request::{RoomKeyRequestContent, RoomKeyRequestEvent, SupportedKeyInfo},
    },
    Device,
};

/// Struct containing a `m.secret.send` event and its acompanying info.
///
/// This struct is created only iff the following three things are true:
///
/// 1. We requested the secret.
/// 2. The secret was received over an encrypted channel.
/// 3. The secret it was received from one ouf our own verified devices.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct GossippedSecret {
    /// The name of the secret.
    pub secret_name: SecretName,
    /// The [`GossipRequest`] that has requested the secret.
    pub gossip_request: GossipRequest,
    /// The `m.secret.send` event containing the actual secret.
    pub event: DecryptedSecretSendEvent,
}

/// An error describing why a key share request won't be honored.
#[cfg(feature = "automatic-room-key-forwarding")]
#[derive(Debug, Clone, thiserror::Error, PartialEq, Eq)]
pub enum KeyForwardDecision {
    /// The key request is from a device that we don't own, we're only sharing
    /// sessions that we know the requesting device already was supposed to get.
    #[error("can't find an active outbound group session")]
    MissingOutboundSession,
    /// The key request is from a device that we don't own and the device wasn't
    /// meant to receive the session in the original key share.
    #[error("outbound session wasn't shared with the requesting device")]
    OutboundSessionNotShared,
    /// The key request is from a device we own, yet we don't trust it.
    #[error("requesting device isn't trusted")]
    UntrustedDevice,
    /// The outbound session was shared with the device, but the device either
    /// accidentally or maliciously changed their curve25519 sender key.
    #[error("the device has changed their curve25519 sender key")]
    ChangedSenderKey,
}

/// A struct describing an outgoing key request.
#[derive(Debug, Clone, Serialize, Deserialize)]
pub struct GossipRequest {
    /// The user we requested the secret from
    pub request_recipient: OwnedUserId,
    /// The unique id of the secret request.
    pub request_id: OwnedTransactionId,
    /// The info of the requested secret.
    pub info: SecretInfo,
    /// Has the request been sent out.
    pub sent_out: bool,
}

/// An enum over the various secret request types we can have.
#[derive(Debug, Clone, Serialize, Deserialize, PartialEq, Eq)]
pub enum SecretInfo {
    /// Info for the `m.room_key_request` variant
    KeyRequest(SupportedKeyInfo),
    /// Info for the `m.secret.request` variant
    SecretRequest(SecretName),
}

impl SecretInfo {
    /// Serialize `SecretInfo` into `String` for usage as database keys and
    /// comparison.
    pub fn as_key(&self) -> String {
        match &self {
            SecretInfo::KeyRequest(info) => {
                format!("keyRequest:{}:{}:{}", info.room_id(), info.session_id(), info.algorithm())
            }
            SecretInfo::SecretRequest(sname) => format!("secretName:{sname}"),
        }
    }
}

impl<T> From<T> for SecretInfo
where
    T: Into<SupportedKeyInfo>,
{
    fn from(v: T) -> Self {
        Self::KeyRequest(v.into())
    }
}

impl From<SecretName> for SecretInfo {
    fn from(i: SecretName) -> Self {
        Self::SecretRequest(i)
    }
}

impl GossipRequest {
    /// Create an ougoing secret request for the given secret.
    pub(crate) fn from_secret_name(own_user_id: OwnedUserId, secret_name: SecretName) -> Self {
        Self {
            request_recipient: own_user_id,
            request_id: TransactionId::new(),
            info: secret_name.into(),
            sent_out: false,
        }
    }

    fn request_type(&self) -> &str {
        match &self.info {
            SecretInfo::KeyRequest(_) => "m.room_key_request",
            SecretInfo::SecretRequest(s) => s.as_ref(),
        }
    }

    fn to_request(&self, own_device_id: &DeviceId) -> OutgoingRequest {
        let request = match &self.info {
            SecretInfo::KeyRequest(r) => {
                let content = RoomKeyRequestContent::new_request(
                    r.clone().into(),
                    own_device_id.to_owned(),
                    self.request_id.to_owned(),
                );
                let content = Raw::new(&content)
                    .expect("We can always serialize a room key request info")
                    .cast();

                ToDeviceRequest::with_id_raw(
                    &self.request_recipient,
                    DeviceIdOrAllDevices::AllDevices,
                    content,
                    ToDeviceEventType::RoomKeyRequest,
                    self.request_id.clone(),
                )
            }
            SecretInfo::SecretRequest(s) => {
                let content =
                    AnyToDeviceEventContent::SecretRequest(SecretRequestEventContent::new(
                        RequestAction::Request(s.clone()),
                        own_device_id.to_owned(),
                        self.request_id.clone(),
                    ));

                ToDeviceRequest::with_id(
                    &self.request_recipient,
                    DeviceIdOrAllDevices::AllDevices,
                    &content,
                    self.request_id.clone(),
                )
            }
        };

        OutgoingRequest { request_id: request.txn_id.clone(), request: Arc::new(request.into()) }
    }

    fn to_cancellation(&self, own_device_id: &DeviceId) -> OutgoingRequest {
        let content = match self.info {
            SecretInfo::KeyRequest(_) => {
                AnyToDeviceEventContent::RoomKeyRequest(ToDeviceRoomKeyRequestEventContent::new(
                    Action::CancelRequest,
                    None,
                    own_device_id.to_owned(),
                    self.request_id.clone(),
                ))
            }
            SecretInfo::SecretRequest(_) => {
                AnyToDeviceEventContent::SecretRequest(SecretRequestEventContent::new(
                    RequestAction::RequestCancellation,
                    own_device_id.to_owned(),
                    self.request_id.clone(),
                ))
            }
        };

        let request = ToDeviceRequest::with_id(
            &self.request_recipient,
            DeviceIdOrAllDevices::AllDevices,
            &content,
            TransactionId::new(),
        );

        OutgoingRequest { request_id: request.txn_id.clone(), request: Arc::new(request.into()) }
    }
}

impl PartialEq for GossipRequest {
    fn eq(&self, other: &Self) -> bool {
        let is_info_equal = match (&self.info, &other.info) {
            (SecretInfo::KeyRequest(first), SecretInfo::KeyRequest(second)) => first == second,
            (SecretInfo::SecretRequest(first), SecretInfo::SecretRequest(second)) => {
                first == second
            }
            (SecretInfo::KeyRequest(_), SecretInfo::SecretRequest(_))
            | (SecretInfo::SecretRequest(_), SecretInfo::KeyRequest(_)) => false,
        };

        self.request_id == other.request_id && is_info_equal
    }
}

#[derive(Debug)]
enum RequestEvent {
    KeyShare(RoomKeyRequestEvent),
    Secret(SecretRequestEvent),
}

impl From<SecretRequestEvent> for RequestEvent {
    fn from(e: SecretRequestEvent) -> Self {
        Self::Secret(e)
    }
}

impl From<RoomKeyRequestEvent> for RequestEvent {
    fn from(e: RoomKeyRequestEvent) -> Self {
        Self::KeyShare(e)
    }
}

impl RequestEvent {
    fn to_request_info(&self) -> RequestInfo {
        RequestInfo::new(
            self.sender().to_owned(),
            self.requesting_device_id().into(),
            self.request_id().to_owned(),
        )
    }

    fn sender(&self) -> &UserId {
        match self {
            RequestEvent::KeyShare(e) => &e.sender,
            RequestEvent::Secret(e) => &e.sender,
        }
    }

    fn requesting_device_id(&self) -> &DeviceId {
        match self {
            RequestEvent::KeyShare(e) => &e.content.requesting_device_id,
            RequestEvent::Secret(e) => &e.content.requesting_device_id,
        }
    }

    fn request_id(&self) -> &TransactionId {
        match self {
            RequestEvent::KeyShare(e) => &e.content.request_id,
            RequestEvent::Secret(e) => &e.content.request_id,
        }
    }
}

#[derive(Debug, Clone, PartialEq, Eq, PartialOrd, Ord, Hash)]
struct RequestInfo {
    sender: OwnedUserId,
    requesting_device_id: OwnedDeviceId,
    request_id: OwnedTransactionId,
}

impl RequestInfo {
    fn new(
        sender: OwnedUserId,
        requesting_device_id: OwnedDeviceId,
        request_id: OwnedTransactionId,
    ) -> Self {
        Self { sender, requesting_device_id, request_id }
    }
}

/// A queue where we store room key requests that we want to serve but the
/// device that requested the key doesn't share an Olm session with us.
#[derive(Clone, Debug, Default)]
struct WaitQueue {
    inner: Arc<StdRwLock<WaitQueueInner>>,
}

#[derive(Debug, Default)]
struct WaitQueueInner {
    requests_waiting_for_session: BTreeMap<RequestInfo, RequestEvent>,
    requests_ids_waiting: BTreeMap<(OwnedUserId, OwnedDeviceId), BTreeSet<OwnedTransactionId>>,
}

impl WaitQueue {
    fn new() -> Self {
        Self::default()
    }

    #[cfg(all(test, feature = "automatic-room-key-forwarding"))]
    fn is_empty(&self) -> bool {
        let read_guard = self.inner.read().unwrap();
        read_guard.requests_ids_waiting.is_empty()
            && read_guard.requests_waiting_for_session.is_empty()
    }

    fn insert(&self, device: &Device, event: RequestEvent) {
        let request_id = event.request_id().to_owned();
        let requests_waiting_key = RequestInfo::new(
            device.user_id().to_owned(),
            device.device_id().into(),
            request_id.clone(),
        );
        let ids_waiting_key = (device.user_id().to_owned(), device.device_id().into());

        let mut write_guard = self.inner.write().unwrap();
        write_guard.requests_waiting_for_session.insert(requests_waiting_key, event);
        write_guard.requests_ids_waiting.entry(ids_waiting_key).or_default().insert(request_id);
    }

    fn remove(&self, user_id: &UserId, device_id: &DeviceId) -> Vec<(RequestInfo, RequestEvent)> {
        let mut write_guard = self.inner.write().unwrap();
        write_guard
            .requests_ids_waiting
            .remove(&(user_id.to_owned(), device_id.into()))
            .map(|request_ids| {
                request_ids
                    .iter()
                    .filter_map(|id| {
                        let key =
                            RequestInfo::new(user_id.to_owned(), device_id.into(), id.to_owned());
                        write_guard.requests_waiting_for_session.remove_entry(&key)
                    })
                    .collect()
            })
            .unwrap_or_default()
    }
}