core_crypto/mls/conversation/
welcome.rs

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
use std::borrow::BorrowMut;

use crate::context::CentralContext;
use crate::{
    e2e_identity::init_certificates::NewCrlDistributionPoint,
    group_store::GroupStore,
    mls::credential::crl::{extract_crl_uris_from_group, get_new_crl_distribution_points},
    prelude::{
        ConversationId, CryptoError, CryptoResult, MlsConversation, MlsConversationConfiguration,
        MlsCustomConfiguration, MlsError,
    },
};
use core_crypto_keystore::{connection::FetchFromDatabase, entities::PersistedMlsPendingGroup};
use mls_crypto_provider::MlsCryptoProvider;
use openmls::prelude::{MlsGroup, MlsMessageIn, MlsMessageInBody, Welcome};
use openmls_traits::OpenMlsCryptoProvider;
use tls_codec::Deserialize;

/// Contains everything client needs to know after decrypting an (encrypted) Welcome message
#[derive(Debug)]
pub struct WelcomeBundle {
    /// MLS Group Id
    pub id: ConversationId,
    /// New CRL distribution points that appeared by the introduction of a new credential
    pub crl_new_distribution_points: NewCrlDistributionPoint,
}

impl CentralContext {
    /// Create a conversation from a TLS serialized MLS Welcome message. The `MlsConversationConfiguration` used in this function will be the default implementation.
    ///
    /// # Arguments
    /// * `welcome` - a TLS serialized welcome message
    /// * `configuration` - configuration of the MLS conversation fetched from the Delivery Service
    ///
    /// # Return type
    /// This function will return the conversation/group id
    ///
    /// # Errors
    /// see [CentralContext::process_welcome_message]
    #[cfg_attr(test, crate::dispotent)]
    pub async fn process_raw_welcome_message(
        &self,
        welcome: Vec<u8>,
        custom_cfg: MlsCustomConfiguration,
    ) -> CryptoResult<WelcomeBundle> {
        let mut cursor = std::io::Cursor::new(welcome);
        let welcome = MlsMessageIn::tls_deserialize(&mut cursor).map_err(MlsError::from)?;
        self.process_welcome_message(welcome, custom_cfg).await
    }

    /// Create a conversation from a received MLS Welcome message
    ///
    /// # Arguments
    /// * `welcome` - a `Welcome` message received as a result of a commit adding new members to a group
    /// * `configuration` - configuration of the group/conversation
    ///
    /// # Return type
    /// This function will return the conversation/group id
    ///
    /// # Errors
    /// Errors can be originating from the KeyStore of from OpenMls:
    /// * if no [openmls::key_packages::KeyPackage] can be read from the KeyStore
    /// * if the message can't be decrypted
    #[cfg_attr(test, crate::dispotent)]
    pub async fn process_welcome_message(
        &self,
        welcome: MlsMessageIn,
        custom_cfg: MlsCustomConfiguration,
    ) -> CryptoResult<WelcomeBundle> {
        let welcome = match welcome.extract() {
            MlsMessageInBody::Welcome(welcome) => welcome,
            _ => return Err(CryptoError::ConsumerError),
        };
        let cs = welcome.ciphersuite().into();
        let configuration = MlsConversationConfiguration {
            ciphersuite: cs,
            custom: custom_cfg,
            ..Default::default()
        };
        let mls_provider = self.mls_provider().await?;
        let mut mls_groups = self.mls_groups().await?;
        let conversation =
            MlsConversation::from_welcome_message(welcome, configuration, &mls_provider, mls_groups.borrow_mut())
                .await?;

        // We wait for the group to be created then we iterate through all members
        let crl_new_distribution_points =
            get_new_crl_distribution_points(&mls_provider, extract_crl_uris_from_group(&conversation.group)?).await?;

        let id = conversation.id.clone();
        mls_groups.insert(id.clone(), conversation);

        Ok(WelcomeBundle {
            id,
            crl_new_distribution_points,
        })
    }
}

impl MlsConversation {
    // ? Do we need to provide the ratchet_tree to the MlsGroup? Does everything crumble down if we can't actually get it?
    /// Create the MLS conversation from an MLS Welcome message
    ///
    /// # Arguments
    /// * `welcome` - welcome message to create the group from
    /// * `config` - group configuration
    /// * `backend` - the KeyStore to persist the group
    ///
    /// # Errors
    /// Errors can happen from OpenMls or from the KeyStore
    async fn from_welcome_message(
        welcome: Welcome,
        configuration: MlsConversationConfiguration,
        backend: &MlsCryptoProvider,
        mls_groups: &mut GroupStore<MlsConversation>,
    ) -> CryptoResult<Self> {
        let mls_group_config = configuration.as_openmls_default_configuration()?;

        let group = MlsGroup::new_from_welcome(backend, &mls_group_config, welcome, None).await;

        let group = match group {
            Err(openmls::prelude::WelcomeError::NoMatchingKeyPackage)
            | Err(openmls::prelude::WelcomeError::NoMatchingEncryptionKey) => return Err(CryptoError::OrphanWelcome),
            _ => group.map_err(MlsError::from)?,
        };

        let id = ConversationId::from(group.group_id().as_slice());
        let existing_conversation = mls_groups.get_fetch(&id[..], &backend.keystore(), None).await;
        let conversation_exists = existing_conversation.ok().flatten().is_some();

        let pending_group = backend.key_store().find::<PersistedMlsPendingGroup>(&id[..]).await;
        let pending_group_exists = pending_group.ok().flatten().is_some();

        if conversation_exists || pending_group_exists {
            return Err(CryptoError::ConversationAlreadyExists(id));
        }

        Self::from_mls_group(group, configuration, backend).await
    }
}

#[cfg(test)]
mod tests {
    use wasm_bindgen_test::*;

    use crate::{prelude::MlsConversationCreationMessage, test_utils::*};

    use super::*;

    wasm_bindgen_test_configure!(run_in_browser);

    #[apply(all_cred_cipher)]
    #[wasm_bindgen_test]
    async fn joining_from_welcome_should_prune_local_key_material(case: TestCase) {
        run_test_with_client_ids(case.clone(), ["alice", "bob"], move |[alice_central, bob_central]| {
            Box::pin(async move {
                let id = conversation_id();
                // has to be before the original key_package count because it creates one
                let bob = bob_central.rand_key_package(&case).await;
                // Keep track of the whatever amount was initially generated
                let prev_count = bob_central.context.count_entities().await;

                // Create a conversation from alice, where she invites bob
                alice_central
                    .context
                    .new_conversation(&id, case.credential_type, case.cfg.clone())
                    .await
                    .unwrap();

                let MlsConversationCreationMessage { welcome, .. } = alice_central
                    .context
                    .add_members_to_conversation(&id, vec![bob])
                    .await
                    .unwrap();

                // Bob accepts the welcome message, and as such, it should prune the used keypackage from the store
                bob_central
                    .context
                    .process_welcome_message(welcome.into(), case.custom_cfg())
                    .await
                    .unwrap();

                // Ensure we're left with 1 less keypackage bundle in the store, because it was consumed with the OpenMLS Welcome message
                let next_count = bob_central.context.count_entities().await;
                assert_eq!(next_count.key_package, prev_count.key_package - 1);
                assert_eq!(next_count.hpke_private_key, prev_count.hpke_private_key - 1);
                assert_eq!(next_count.encryption_keypair, prev_count.encryption_keypair - 1);
            })
        })
        .await;
    }

    #[apply(all_cred_cipher)]
    #[wasm_bindgen_test]
    async fn process_welcome_should_fail_when_already_exists(case: TestCase) {
        run_test_with_client_ids(case.clone(), ["alice", "bob"], move |[alice_central, bob_central]| {
            Box::pin(async move {
                let id = conversation_id();
                alice_central
                    .context
                    .new_conversation(&id, case.credential_type, case.cfg.clone())
                    .await
                    .unwrap();
                let bob = bob_central.rand_key_package(&case).await;
                let welcome = alice_central
                    .context
                    .add_members_to_conversation(&id, vec![bob])
                    .await
                    .unwrap()
                    .welcome;

                // Meanwhile Bob creates a conversation with the exact same id as the one he's trying to join
                bob_central
                    .context
                    .new_conversation(&id, case.credential_type, case.cfg.clone())
                    .await
                    .unwrap();
                let join_welcome = bob_central
                    .context
                    .process_welcome_message(welcome.into(), case.custom_cfg())
                    .await;
                assert!(matches!(join_welcome.unwrap_err(), CryptoError::ConversationAlreadyExists(i) if i == id));
            })
        })
        .await;
    }
}