core_crypto/mls/conversation/
commit_delay.rs1use log::{debug, trace};
2use openmls::prelude::LeafNodeIndex;
3
4use super::MlsConversation;
5use crate::MlsError;
6
7const DELAY_RAMP_UP_MULTIPLIER: f32 = 120.0;
9const DELAY_RAMP_UP_SUB: u64 = 106;
10const DELAY_POS_LINEAR_INCR: u64 = 15;
11const DELAY_POS_LINEAR_RANGE: std::ops::RangeInclusive<u64> = 1..=3;
12
13impl MlsConversation {
14 pub fn compute_next_commit_delay(&self) -> Option<u64> {
20 use openmls::messages::proposals::Proposal;
21
22 if self.group.pending_proposals().count() > 0 {
23 let removed_index = self
24 .group
25 .pending_proposals()
26 .filter_map(|proposal| {
27 if let Proposal::Remove(remove_proposal) = proposal.proposal() {
28 Some(remove_proposal.removed())
29 } else {
30 None
31 }
32 })
33 .collect::<Vec<LeafNodeIndex>>();
34
35 let self_index = self.group.own_leaf_index();
36 debug!(removed_index:? = removed_index, self_index:? = self_index; "Indexes");
37 let is_self_removed = removed_index.iter().any(|&i| i == self_index);
39
40 if is_self_removed {
42 debug!("Self removed from group, no delay needed");
43 return None;
44 }
45
46 let epoch = self.group.epoch().as_u64();
47 let mut own_index = self.group.own_leaf_index().u32() as u64;
48
49 let left_tree_diff = self
51 .group
52 .members()
53 .take(own_index as usize)
54 .try_fold(0u32, |mut acc, kp| {
55 if removed_index.contains(&kp.index) {
56 acc += 1;
57 }
58
59 Result::<_, MlsError>::Ok(acc)
60 })
61 .unwrap_or_default();
62
63 let nb_members = (self.group.members().count() as u64).saturating_sub(removed_index.len() as u64);
65 own_index = own_index.saturating_sub(left_tree_diff as u64);
67
68 Some(Self::calculate_delay(own_index, epoch, nb_members))
69 } else {
70 trace!("No pending proposals, no delay needed");
71 None
72 }
73 }
74
75 fn calculate_delay(self_index: u64, epoch: u64, nb_members: u64) -> u64 {
76 let position = if nb_members > 0 {
77 ((epoch % nb_members) + (self_index % nb_members)) % nb_members + 1
78 } else {
79 1
80 };
81
82 if DELAY_POS_LINEAR_RANGE.contains(&position) {
83 position.saturating_sub(1) * DELAY_POS_LINEAR_INCR
84 } else {
85 (((position as f32).ln() * DELAY_RAMP_UP_MULTIPLIER) as u64).saturating_sub(DELAY_RAMP_UP_SUB)
86 }
87 }
88}
89
90#[cfg(test)]
91mod tests {
92 use super::*;
93 use crate::test_utils::*;
94 use tls_codec::Serialize as _;
95 use wasm_bindgen_test::*;
96
97 wasm_bindgen_test_configure!(run_in_browser);
98
99 #[test]
100 #[wasm_bindgen_test]
101 fn calculate_delay_single() {
102 let (self_index, epoch, nb_members) = (0, 0, 1);
103 let delay = MlsConversation::calculate_delay(self_index, epoch, nb_members);
104 assert_eq!(delay, 0);
105 }
106
107 #[test]
108 #[wasm_bindgen_test]
109 fn calculate_delay_max() {
110 let (self_index, epoch, nb_members) = (u64::MAX, u64::MAX, u64::MAX);
111 let delay = MlsConversation::calculate_delay(self_index, epoch, nb_members);
112 assert_eq!(delay, 0);
113 }
114
115 #[test]
116 #[wasm_bindgen_test]
117 fn calculate_delay_min() {
118 let (self_index, epoch, nb_members) = (u64::MIN, u64::MIN, u64::MAX);
119 let delay = MlsConversation::calculate_delay(self_index, epoch, nb_members);
120 assert_eq!(delay, 0);
121 }
122
123 #[test]
124 #[wasm_bindgen_test]
125 fn calculate_delay_zero_members() {
126 let (self_index, epoch, nb_members) = (0, 0, u64::MIN);
127 let delay = MlsConversation::calculate_delay(self_index, epoch, nb_members);
128 assert_eq!(delay, 0);
129 }
130
131 #[test]
132 #[wasm_bindgen_test]
133 fn calculate_delay_min_max() {
134 let (self_index, epoch, nb_members) = (u64::MIN, u64::MAX, u64::MAX);
135 let delay = MlsConversation::calculate_delay(self_index, epoch, nb_members);
136 assert_eq!(delay, 0);
137 }
138
139 #[test]
140 #[wasm_bindgen_test]
141 fn calculate_delay_n() {
142 let epoch = 1;
143 let nb_members = 10;
144
145 let indexes_delays = [
146 (0, 15),
147 (1, 30),
148 (2, 60),
149 (3, 87),
150 (4, 109),
151 (5, 127),
152 (6, 143),
153 (7, 157),
154 (8, 170),
155 (9, 0),
156 (10, 15),
158 ];
159
160 for (self_index, expected_delay) in indexes_delays {
161 let delay = MlsConversation::calculate_delay(self_index, epoch, nb_members);
162 assert_eq!(delay, expected_delay);
163 }
164 }
165
166 #[apply(all_cred_cipher)]
167 #[wasm_bindgen_test]
168 async fn calculate_delay_creator_removed(case: TestContext) {
169 let [alice_central, bob_central, charlie_central] = case.sessions().await;
170 Box::pin(async move {
171 let id = conversation_id();
172
173 alice_central
174 .transaction
175 .new_conversation(&id, case.credential_type, case.cfg.clone())
176 .await
177 .unwrap();
178
179 let bob = bob_central.rand_key_package(&case).await;
180 alice_central
181 .transaction
182 .conversation(&id)
183 .await
184 .unwrap()
185 .add_members(vec![bob])
186 .await
187 .unwrap();
188 let bob_welcome = alice_central.mls_transport().await.latest_welcome_message().await;
189 assert_eq!(alice_central.get_conversation_unchecked(&id).await.members().len(), 2);
190
191 bob_central
192 .transaction
193 .process_welcome_message(bob_welcome.clone().into(), case.custom_cfg())
194 .await
195 .unwrap();
196
197 let charlie = charlie_central.rand_key_package(&case).await;
198 alice_central
199 .transaction
200 .conversation(&id)
201 .await
202 .unwrap()
203 .add_members(vec![charlie])
204 .await
205 .unwrap();
206 let charlie_welcome_bundle = alice_central.mls_transport().await.latest_commit_bundle().await;
207 assert_eq!(alice_central.get_conversation_unchecked(&id).await.members().len(), 3);
208
209 let _ = bob_central
210 .transaction
211 .conversation(&id)
212 .await
213 .unwrap()
214 .decrypt_message(&charlie_welcome_bundle.commit.tls_serialize_detached().unwrap())
215 .await
216 .unwrap();
217
218 charlie_central
219 .transaction
220 .process_welcome_message(charlie_welcome_bundle.welcome.unwrap().into(), case.custom_cfg())
221 .await
222 .unwrap();
223
224 assert_eq!(
225 bob_central.get_conversation_unchecked(&id).await.id(),
226 alice_central.get_conversation_unchecked(&id).await.id()
227 );
228 assert_eq!(
229 charlie_central.get_conversation_unchecked(&id).await.id(),
230 alice_central.get_conversation_unchecked(&id).await.id()
231 );
232
233 let proposal_bundle = alice_central
234 .transaction
235 .new_remove_proposal(&id, alice_central.get_client_id().await)
236 .await
237 .unwrap();
238
239 let bob_hypothetical_position = 0;
240 let charlie_hypothetical_position = 1;
241
242 let bob_decrypted_message = bob_central
243 .transaction
244 .conversation(&id)
245 .await
246 .unwrap()
247 .decrypt_message(&proposal_bundle.proposal.tls_serialize_detached().unwrap())
248 .await
249 .unwrap();
250
251 assert_eq!(
252 bob_decrypted_message.delay,
253 Some(DELAY_POS_LINEAR_INCR * bob_hypothetical_position)
254 );
255
256 let charlie_decrypted_message = charlie_central
257 .transaction
258 .conversation(&id)
259 .await
260 .unwrap()
261 .decrypt_message(&proposal_bundle.proposal.tls_serialize_detached().unwrap())
262 .await
263 .unwrap();
264
265 assert_eq!(
266 charlie_decrypted_message.delay,
267 Some(DELAY_POS_LINEAR_INCR * charlie_hypothetical_position)
268 );
269 })
270 .await;
271 }
272}