ping_core/
conversation.rs

1//! Conversation state — wraps an OpenMLS `MlsGroup`.
2//!
3//! Each external conversation maps 1:1 to an MLS group whose leaves are devices. The DeviceGroup
4//! (one per user, devices only) is just a special-cased conversation with the same wrapper.
5//!
6//! Persistence: we snapshot the `MlsGroup` after every state-changing operation under
7//! `groups/{conversation_id}` and cache the result in-memory.
8
9use openmls::{
10    framing::{MlsMessageOut, ProcessedMessageContent},
11    group::{MlsGroup, MlsGroupCreateConfig, MlsGroupJoinConfig},
12    prelude::{
13        tls_codec::{Deserialize as TlsDeserialize, Serialize as TlsSerialize},
14        BasicCredential, Ciphersuite, CredentialWithKey, MlsMessageBodyIn, MlsMessageIn,
15        ProcessedMessage, ProtocolMessage, ProtocolVersion,
16    },
17};
18use openmls_basic_credential::SignatureKeyPair;
19use openmls_traits::OpenMlsProvider;
20use ping_mls_store::PersistentMlsProvider;
21use serde::{Deserialize, Serialize};
22use std::collections::BTreeMap;
23use std::sync::Arc;
24use ulid::Ulid;
25use zeroize::Zeroizing;
26
27use crate::{
28    clock::Hlc,
29    codec,
30    device::{DeviceId, GroupSnapshotEntry, GroupStateSnapshot, GROUP_SNAPSHOT_VERSION},
31    error::{Error, Result},
32    identity::UserId,
33    message::{IncomingMessage, MessageEnvelope, MessageKind},
34    storage::Storage,
35    sync::SyncCursor,
36};
37
38const DEFAULT_CIPHERSUITE: Ciphersuite = Ciphersuite::MLS_128_DHKEMX25519_AES128GCM_SHA256_Ed25519;
39
40/// 16-byte conversation identifier (ULID encoded). Stable across epochs.
41#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash, PartialOrd, Ord, Serialize, Deserialize)]
42pub struct ConversationId(#[serde(with = "serde_bytes_array16")] pub [u8; 16]);
43
44impl ConversationId {
45    pub fn new() -> Self {
46        Self(Ulid::new().to_bytes())
47    }
48    pub fn as_hex(&self) -> String {
49        hex::encode(self.0)
50    }
51}
52
53impl Default for ConversationId {
54    fn default() -> Self {
55        Self::new()
56    }
57}
58
59mod serde_bytes_array16 {
60    use serde::{Deserializer, Serializer};
61    pub fn serialize<S: Serializer>(b: &[u8; 16], s: S) -> Result<S::Ok, S::Error> {
62        serde_bytes::serialize(b.as_slice(), s)
63    }
64    pub fn deserialize<'de, D: Deserializer<'de>>(d: D) -> Result<[u8; 16], D::Error> {
65        let v: Vec<u8> = serde_bytes::deserialize(d)?;
66        v.try_into()
67            .map_err(|_| serde::de::Error::custom("expected 16 bytes"))
68    }
69}
70
71#[derive(Debug, Clone, Serialize, Deserialize)]
72pub struct ConversationMeta {
73    pub id: ConversationId,
74    pub name: Option<String>,
75    pub epoch: u64,
76    pub member_count: u32,
77    pub is_device_group: bool,
78    pub created_at_ms: u64,
79}
80
81/// In-memory conversation handle. Holds the OpenMLS group plus our wire-level cursor.
82pub struct Conversation {
83    pub(crate) id: ConversationId,
84    pub(crate) meta: ConversationMeta,
85    pub(crate) group: MlsGroup,
86    pub(crate) crypto: Arc<PersistentMlsProvider>,
87    pub(crate) signing: Arc<SignatureKeyPair>,
88    pub(crate) own_device: DeviceId,
89    pub(crate) seq: u64,
90    pub(crate) hlc: Hlc,
91    pub(crate) cursor: SyncCursor,
92    pub(crate) storage: Arc<dyn Storage>,
93    /// Local device→leaf-index map for [CR-2] revocation.
94    ///
95    /// Populated when this device either (a) admits a peer via [`Self::add_members`] —
96    /// every entry in the `Vec<(DeviceId, KeyPackage)>` is recorded after the commit
97    /// merges — or (b) joins as the receiving device via [`Self::join`], at which point
98    /// we record our own leaf. Pruned when [`Self::remove_members`] is called.
99    ///
100    /// Not authoritative for *peers' devices we didn't admit*: those are visible in
101    /// `group.members()` but their device_ids are opaque to this client. `revoke_device`
102    /// is therefore best-effort across conversations we ourselves invited the device
103    /// into; see [`MessagingClient::revoke_device`] for the documented scope.
104    pub(crate) device_leaves: BTreeMap<DeviceId, u32>,
105}
106
107impl std::fmt::Debug for Conversation {
108    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
109        f.debug_struct("Conversation")
110            .field("id", &self.id.as_hex())
111            .field("meta", &self.meta)
112            .finish()
113    }
114}
115
116impl Conversation {
117    pub fn id(&self) -> ConversationId {
118        self.id
119    }
120    pub fn meta(&self) -> &ConversationMeta {
121        &self.meta
122    }
123    pub fn epoch(&self) -> u64 {
124        self.group.epoch().as_u64()
125    }
126    pub fn cursor(&self) -> &SyncCursor {
127        &self.cursor
128    }
129
130    /// Create a new conversation, with `self` as the only initial member.
131    // 8 args is a lot, but they're all needed for an internal constructor and a builder
132    // would be over-engineered for v0.1.
133    #[allow(clippy::too_many_arguments)]
134    pub(crate) fn create(
135        id: ConversationId,
136        name: Option<String>,
137        own_device: DeviceId,
138        own_user: &UserId,
139        crypto: Arc<PersistentMlsProvider>,
140        signing: Arc<SignatureKeyPair>,
141        storage: Arc<dyn Storage>,
142        now_ms: u64,
143    ) -> Result<Self> {
144        let credential = BasicCredential::new(own_user.0.clone());
145        let credential_with_key = CredentialWithKey {
146            credential: credential.into(),
147            signature_key: signing.public().into(),
148        };
149        let cfg = MlsGroupCreateConfig::builder()
150            .ciphersuite(DEFAULT_CIPHERSUITE)
151            .use_ratchet_tree_extension(true)
152            .build();
153        let group = MlsGroup::new_with_group_id(
154            crypto.as_ref(),
155            signing.as_ref(),
156            &cfg,
157            openmls::group::GroupId::from_slice(&id.0),
158            credential_with_key,
159        )
160        .map_err(Error::mls)?;
161
162        let meta = ConversationMeta {
163            id,
164            name,
165            epoch: 0,
166            member_count: 1,
167            is_device_group: false,
168            created_at_ms: now_ms,
169        };
170        // [CR-2] Group creator is always leaf 0; record so revoke_device can target it.
171        let mut device_leaves = BTreeMap::new();
172        device_leaves.insert(own_device.clone(), group.own_leaf_index().u32());
173        Ok(Self {
174            id,
175            meta,
176            group,
177            crypto,
178            signing,
179            own_device,
180            seq: 0,
181            hlc: Hlc::ZERO.tick(now_ms),
182            cursor: SyncCursor::default(),
183            storage,
184            device_leaves,
185        })
186    }
187
188    /// Join an existing conversation from a Welcome message.
189    pub(crate) fn join(
190        welcome_bytes: &[u8],
191        own_device: DeviceId,
192        crypto: Arc<PersistentMlsProvider>,
193        signing: Arc<SignatureKeyPair>,
194        storage: Arc<dyn Storage>,
195        now_ms: u64,
196    ) -> Result<Self> {
197        let mls_in = MlsMessageIn::tls_deserialize_exact(welcome_bytes).map_err(Error::mls)?;
198        let welcome = match mls_in.extract() {
199            MlsMessageBodyIn::Welcome(w) => w,
200            _ => return Err(Error::Invalid("expected Welcome".into())),
201        };
202        let cfg = MlsGroupJoinConfig::builder()
203            .use_ratchet_tree_extension(true)
204            .build();
205        let staged =
206            openmls::group::StagedWelcome::new_from_welcome(crypto.as_ref(), &cfg, welcome, None)
207                .map_err(Error::mls)?;
208        let group = staged.into_group(crypto.as_ref()).map_err(Error::mls)?;
209
210        let id_bytes: [u8; 16] = group
211            .group_id()
212            .as_slice()
213            .try_into()
214            .map_err(|_| Error::Invalid("group id must be 16 bytes".into()))?;
215        let id = ConversationId(id_bytes);
216        let meta = ConversationMeta {
217            id,
218            name: None,
219            epoch: group.epoch().as_u64(),
220            member_count: group.members().count() as u32,
221            is_device_group: false,
222            created_at_ms: now_ms,
223        };
224
225        // Seed the cursor at the join epoch so subsequent fetches skip pre-join Commits
226        // (notably the Add commit that produced this Welcome — it lives in the conversation
227        // log at `epoch - 1`, which the joiner must not try to apply on top of its
228        // already-advanced group state).
229        let join_epoch = group.epoch().as_u64();
230        // [CR-2] Record our own (device_id → leaf_index) so the host can later revoke us
231        // via the standard `revoke_device` flow. `own_leaf_index()` is stable for the
232        // lifetime of this group membership.
233        let own_leaf = group.own_leaf_index().u32();
234        let mut device_leaves = BTreeMap::new();
235        device_leaves.insert(own_device.clone(), own_leaf);
236        Ok(Self {
237            id,
238            meta,
239            group,
240            crypto,
241            signing,
242            own_device,
243            seq: 0,
244            hlc: Hlc::ZERO.tick(now_ms),
245            cursor: SyncCursor {
246                epoch: join_epoch,
247                ..Default::default()
248            },
249            storage,
250            device_leaves,
251        })
252    }
253
254    /// [CR-4] Rehydrate a previously-persisted conversation on cold restart.
255    ///
256    /// Loads the OpenMLS group state via `MlsGroup::load` (which reads from the
257    /// provider's storage — populated by the SQLite-backed checkpoint on the
258    /// previous run). Pairs the loaded MLS state with the meta + cursor + device→leaf
259    /// map the host-side `Storage` trait kept for us. Returns `Ok(None)` if OpenMLS
260    /// finds no state for `id` — the host's `groups` namespace had a stale entry.
261    #[allow(clippy::too_many_arguments)]
262    pub(crate) fn load(
263        id: ConversationId,
264        meta: ConversationMeta,
265        cursor: SyncCursor,
266        device_leaves: BTreeMap<DeviceId, u32>,
267        own_device: DeviceId,
268        crypto: Arc<PersistentMlsProvider>,
269        signing: Arc<SignatureKeyPair>,
270        storage: Arc<dyn Storage>,
271        now_ms: u64,
272    ) -> Result<Option<Self>> {
273        use openmls::group::GroupId;
274        let group_id = GroupId::from_slice(&id.0);
275        let group = match MlsGroup::load(crypto.storage(), &group_id).map_err(Error::mls)? {
276            Some(g) => g,
277            None => return Ok(None),
278        };
279        Ok(Some(Self {
280            id,
281            meta,
282            group,
283            crypto,
284            signing,
285            own_device,
286            seq: 0,
287            hlc: Hlc::ZERO.tick(now_ms),
288            cursor,
289            storage,
290            device_leaves,
291        }))
292    }
293
294    /// Encrypt an application message and produce a wire envelope ready for transport.
295    ///
296    /// Uses the [CR-6] plaintext content_hash path: the envelope's `content_hash` is
297    /// `SHA-256(plaintext)`, not the MLS ciphertext. This is what makes rebase clean
298    /// and gives cross-binding hash parity.
299    pub fn send_application(&mut self, plaintext: &[u8], now_ms: u64) -> Result<MessageEnvelope> {
300        let out = self
301            .group
302            .create_message(self.crypto.as_ref(), self.signing.as_ref(), plaintext)
303            .map_err(Error::mls)?;
304
305        self.seq += 1;
306        self.hlc = self.hlc.tick(now_ms);
307        let bytes = out.tls_serialize_detached().map_err(Error::mls)?;
308        let env = MessageEnvelope::new_application(
309            self.id,
310            self.epoch(),
311            self.own_device.clone(),
312            self.seq,
313            self.hlc,
314            bytes,
315            plaintext,
316        );
317        // Advance the local cursor past our own send so a subsequent catch-up sync doesn't
318        // pull this envelope back to us (we've already applied it locally — re-processing
319        // would either fail or duplicate-deliver).
320        self.cursor.advance(
321            env.epoch,
322            self.own_device.clone(),
323            self.seq,
324            self.hlc,
325            now_ms,
326        );
327        Ok(env)
328    }
329
330    /// Add members by KeyPackage. Produces the Commit envelope to broadcast plus the Welcome
331    /// envelope(s) to deliver out-of-band to the newly-added devices.
332    ///
333    /// [CR-2] takes a `Vec<(DeviceId, KeyPackage)>` instead of a bare `Vec<KeyPackage>`. The
334    /// `DeviceId` for each entry is the *caller's* assertion of which device owns that
335    /// KeyPackage — hosts typically get it from the directory service alongside the
336    /// KeyPackage itself. The mapping is persisted per-conversation so [`MessagingClient::revoke_device`]
337    /// can later locate the leaf to remove without a fresh directory lookup. The SDK does
338    /// not cryptographically verify the device claim; that's a host policy concern
339    /// (typically: the directory authenticates the key_package_id → device_id mapping).
340    pub fn add_members(
341        &mut self,
342        entries: Vec<(DeviceId, Vec<u8>)>,
343        now_ms: u64,
344    ) -> Result<AddOutcome> {
345        let mut kps = Vec::with_capacity(entries.len());
346        // Track signature_key → device_id so we can resolve leaf indices post-commit.
347        let mut sig_to_device: Vec<(Vec<u8>, DeviceId)> = Vec::with_capacity(entries.len());
348        for (device_id, raw) in &entries {
349            let mls_in = MlsMessageIn::tls_deserialize_exact(raw).map_err(Error::mls)?;
350            let kp_in = match mls_in.extract() {
351                MlsMessageBodyIn::KeyPackage(kp) => kp,
352                _ => return Err(Error::Invalid("expected KeyPackage".into())),
353            };
354            // KeyPackages on the wire are unvalidated (`KeyPackageIn`); validate against the
355            // crypto provider before handing them to OpenMLS.
356            let kp = kp_in
357                .validate(self.crypto.crypto(), ProtocolVersion::default())
358                .map_err(Error::mls)?;
359            let sig_key = kp.leaf_node().signature_key().as_slice().to_vec();
360            sig_to_device.push((sig_key, device_id.clone()));
361            kps.push(kp);
362        }
363
364        // The Commit's wire `epoch` field is the *source* epoch (the epoch the Commit was
365        // crafted in, matching the epoch embedded in the inner MLS message bytes). The
366        // Welcome's `epoch` is the *post-commit* epoch (it carries the new group state).
367        // This split is what lets a joiner's sync cursor correctly filter pre-join Commits.
368        let pre_commit_epoch = self.epoch();
369
370        let (commit_out, welcome_out, _gi) = self
371            .group
372            .add_members(self.crypto.as_ref(), self.signing.as_ref(), &kps)
373            .map_err(Error::mls)?;
374
375        self.group
376            .merge_pending_commit(self.crypto.as_ref())
377            .map_err(Error::mls)?;
378        self.meta.epoch = self.epoch();
379        self.meta.member_count = self.group.members().count() as u32;
380
381        // [CR-2] Resolve leaf indexes for the devices we just added. The Commit merged each
382        // new KeyPackage's leaf into the tree; match by signature_key (unique per device's
383        // MLS signing keypair) to recover the index.
384        for member in self.group.members() {
385            if let Some((_, device_id)) = sig_to_device
386                .iter()
387                .find(|(sig, _)| sig.as_slice() == member.signature_key.as_slice())
388            {
389                self.device_leaves
390                    .insert(device_id.clone(), member.index.u32());
391            }
392        }
393
394        self.seq += 1;
395        self.hlc = self.hlc.tick(now_ms);
396
397        let commit_bytes = mls_message_out_bytes(commit_out)?;
398        let commit_env = MessageEnvelope::new(
399            self.id,
400            pre_commit_epoch,
401            MessageKind::Commit,
402            self.own_device.clone(),
403            self.seq,
404            self.hlc,
405            commit_bytes,
406        );
407
408        let welcome_bytes = mls_message_out_bytes(welcome_out)?;
409        let welcome_env = MessageEnvelope::new(
410            self.id,
411            self.meta.epoch,
412            MessageKind::Welcome,
413            self.own_device.clone(),
414            self.seq,
415            self.hlc,
416            welcome_bytes,
417        );
418
419        // Advance the local cursor past our own Commit (at the post-commit epoch, since
420        // we've already merged it locally) so catch-up sync doesn't try to re-apply it.
421        self.cursor.advance(
422            self.meta.epoch,
423            self.own_device.clone(),
424            self.seq,
425            self.hlc,
426            now_ms,
427        );
428
429        Ok(AddOutcome {
430            commit: commit_env,
431            welcome: welcome_env,
432        })
433    }
434
435    pub fn remove_members(
436        &mut self,
437        leaf_indexes: Vec<u32>,
438        now_ms: u64,
439    ) -> Result<MessageEnvelope> {
440        use openmls::prelude::LeafNodeIndex;
441        let leaves: Vec<LeafNodeIndex> = leaf_indexes
442            .iter()
443            .copied()
444            .map(LeafNodeIndex::new)
445            .collect();
446
447        // Capture the source epoch before merge — see add_members for the rationale.
448        let pre_commit_epoch = self.epoch();
449
450        let (commit_out, _welcome_opt, _gi) = self
451            .group
452            .remove_members(self.crypto.as_ref(), self.signing.as_ref(), &leaves)
453            .map_err(Error::mls)?;
454        self.group
455            .merge_pending_commit(self.crypto.as_ref())
456            .map_err(Error::mls)?;
457        self.meta.epoch = self.epoch();
458        self.meta.member_count = self.group.members().count() as u32;
459
460        // [CR-2] Prune the device→leaf map for any devices we just removed. Other
461        // entries' leaf indexes are stable across MLS adds/removes (OpenMLS reuses
462        // blank slots, doesn't reshuffle live leaves).
463        let removed: std::collections::HashSet<u32> = leaf_indexes.iter().copied().collect();
464        self.device_leaves.retain(|_, idx| !removed.contains(idx));
465
466        self.seq += 1;
467        self.hlc = self.hlc.tick(now_ms);
468        let bytes = mls_message_out_bytes(commit_out)?;
469        let env = MessageEnvelope::new(
470            self.id,
471            pre_commit_epoch,
472            MessageKind::Commit,
473            self.own_device.clone(),
474            self.seq,
475            self.hlc,
476            bytes,
477        );
478        // Advance the local cursor past our own Commit (at the post-commit epoch we've just
479        // merged into) so catch-up sync doesn't try to re-apply it.
480        self.cursor.advance(
481            self.meta.epoch,
482            self.own_device.clone(),
483            self.seq,
484            self.hlc,
485            now_ms,
486        );
487        Ok(env)
488    }
489
490    /// Process an inbound envelope. Returns Some(IncomingMessage) for application traffic.
491    pub fn process(
492        &mut self,
493        env: &MessageEnvelope,
494        now_ms: u64,
495    ) -> Result<Option<IncomingMessage>> {
496        if !self.cursor.is_new(env.epoch, &env.sender_device, env.seq) {
497            return Ok(None); // dedupe: already applied
498        }
499        let mls_in = MlsMessageIn::tls_deserialize_exact(&env.payload).map_err(Error::mls)?;
500
501        // OpenMLS' `process_message` expects an `impl Into<ProtocolMessage>`. `MlsMessageIn`
502        // itself doesn't implement that; we have to extract the body and convert the inner
503        // private/public message. Welcomes are handled at the client level, not here.
504        let protocol_msg: ProtocolMessage = match mls_in.extract() {
505            MlsMessageBodyIn::PrivateMessage(m) => m.into(),
506            MlsMessageBodyIn::PublicMessage(m) => m.into(),
507            MlsMessageBodyIn::Welcome(_) => {
508                return Err(Error::Invalid(
509                    "Welcome must be handled at client level, not in-group".into(),
510                ));
511            }
512            _ => return Err(Error::Invalid("unsupported MLS message body".into())),
513        };
514
515        let processed: ProcessedMessage = self
516            .group
517            .process_message(self.crypto.as_ref(), protocol_msg)
518            .map_err(Error::mls)?;
519
520        let out = match processed.into_content() {
521            ProcessedMessageContent::ApplicationMessage(app) => {
522                let pt = app.into_bytes();
523                // CR-6: for v=2 application envelopes the wire-contract validator can't
524                // check `content_hash` (the hash is over plaintext, which it didn't have).
525                // We can now: verify SHA-256(pt) == env.content_hash and reject mismatches.
526                // For v=1 envelopes the wire-contract validator already checked the
527                // ciphertext-based hash, so no extra work here.
528                if env.v >= 2 {
529                    let computed = crate::message::hash_application_plaintext(&pt);
530                    if computed != env.content_hash {
531                        return Err(Error::Invalid(
532                            "v=2 application content_hash mismatch".into(),
533                        ));
534                    }
535                }
536                Some(IncomingMessage {
537                    conversation_id: self.id,
538                    sender_device: env.sender_device.clone(),
539                    epoch: env.epoch,
540                    hlc: env.hlc,
541                    plaintext: pt,
542                    content_hash: env.content_hash,
543                })
544            }
545            ProcessedMessageContent::StagedCommitMessage(staged) => {
546                self.group
547                    .merge_staged_commit(self.crypto.as_ref(), *staged)
548                    .map_err(Error::mls)?;
549                self.meta.epoch = self.epoch();
550                self.meta.member_count = self.group.members().count() as u32;
551                None
552            }
553            ProcessedMessageContent::ProposalMessage(_)
554            | ProcessedMessageContent::ExternalJoinProposalMessage(_) => {
555                // Proposals are buffered by OpenMLS until the next Commit; nothing to surface
556                // to the application.
557                None
558            }
559        };
560
561        self.cursor.advance(
562            env.epoch,
563            env.sender_device.clone(),
564            env.seq,
565            env.hlc,
566            now_ms,
567        );
568        Ok(out)
569    }
570
571    /// Export a derived secret keyed to this group's current epoch ([CR-8]).
572    ///
573    /// Wraps `MlsGroup::export_secret` (the MLS exporter, RFC 9420 §8.5) and surfaces the
574    /// bytes in a `Zeroizing<Vec<u8>>` so the local copy is wiped on drop. Used by the host
575    /// to seed:
576    ///   * the ephemeral channel (`ping/ephemeral`, §5.4 of the architecture)
577    ///   * call media keys (`ping/calls/media/{call_id}`, §7.2)
578    ///   * call-ephemeral framer keys (`ping/calls/ephemeral/{call_id}`, §7.5)
579    ///
580    /// `label` should use the documented `ping/*` namespacing convention. There is no
581    /// runtime enforcement — cross-binding parity is enforced by conformance fixtures
582    /// pinning specific label strings.
583    ///
584    /// Output is the secret. Callers MUST treat the buffer as a secret: never log, never
585    /// persist unencrypted. The wrapper zeroes our local copy on drop; the caller is
586    /// responsible for zeroing any copy they make.
587    pub fn export_secret(
588        &self,
589        label: &str,
590        context: &[u8],
591        length: usize,
592    ) -> Result<Zeroizing<Vec<u8>>> {
593        if length == 0 {
594            return Err(Error::Invalid("export_secret length must be > 0".into()));
595        }
596        // Soft cap to prevent runaway allocations from a malformed caller. Real labels never
597        // need more than ~64 bytes (AES-256 key + 96-bit nonce + slack); 1 KiB is generous.
598        if length > 1024 {
599            return Err(Error::Invalid(
600                "export_secret length exceeds 1024-byte cap".into(),
601            ));
602        }
603        let bytes = self
604            .group
605            .export_secret(self.crypto.as_ref(), label, context, length)
606            .map_err(Error::mls)?;
607        Ok(Zeroizing::new(bytes))
608    }
609
610    /// [CR-7] Export a portable snapshot of this group's MLS state.
611    ///
612    /// Walks the provider's working set, picks every entry whose key references this
613    /// group's id, and bundles them with format metadata. Returns CBOR-encoded bytes
614    /// suitable for inclusion in:
615    ///   * `LinkingTicket.catchup_snapshot.conversation_metas[i].group_state_bytes`
616    ///     (via [CR-13] — host calls this and passes the bytes through);
617    ///   * `IdentityBackup.device_group_snapshot` (the Permissive-recovery path per
618    ///     `docs/architecture/recovery.md`).
619    ///
620    /// Returns `Err` if the encoded snapshot exceeds [`GROUP_SNAPSHOT_HARD_CAP`].
621    /// Output is wrapped in `Zeroizing` because the bytes contain past epoch secrets;
622    /// the caller's copy on the FFI side is the host's responsibility to wipe.
623    pub fn export_state_snapshot(&self, now_ms: u64) -> Result<Zeroizing<Vec<u8>>> {
624        let entries = self.crypto.group_scoped_entries(&self.id.0);
625        let snap = GroupStateSnapshot {
626            v: GROUP_SNAPSHOT_VERSION,
627            group_id: self.id,
628            openmls_storage_version: openmls_traits::storage::CURRENT_VERSION,
629            snapshot_created_at_ms: now_ms,
630            entries: entries
631                .into_iter()
632                .map(|(key, value)| GroupSnapshotEntry { key, value })
633                .collect(),
634        };
635        Ok(Zeroizing::new(snap.encode()?))
636    }
637
638    /// Look up the leaf index this device controls, if known ([CR-2]).
639    ///
640    /// Returns the locally-tracked leaf for `device_id`. Only populated for devices we
641    /// added via [`Self::add_members`] or for our own leaf via [`Self::create`] /
642    /// [`Self::join`]. Devices a peer admitted on our behalf are not in this map.
643    pub fn leaf_index_of(&self, device_id: &DeviceId) -> Option<u32> {
644        self.device_leaves.get(device_id).copied()
645    }
646
647    pub(crate) async fn snapshot_to_storage(&self) -> Result<()> {
648        let blob = self
649            .group
650            .export_secret(self.crypto.as_ref(), "ping-snapshot-marker", &[], 32)
651            .ok();
652        // OpenMLS persists the group via its own keystore inside `crypto`. We only need to
653        // record meta + cursor here; the group itself is recovered by re-opening with the
654        // same provider on next launch.
655        let _ = blob; // intentionally unused — present for future binary-snapshot path
656
657        // [CR-4] Flush the MLS working set to the configured backend (no-op for
658        // `StorageBackend::Memory`). MUST happen on every state-changing op so a cold
659        // restart — iOS NSE, web SW — finds the latest epoch on disk.
660        //
661        // `checkpoint_async` is required for the WASM `IndexedDb` backend (IDB is
662        // async-only); native Memory / Sqlite paths await trivially since their
663        // I/O is sync internally.
664        self.crypto
665            .checkpoint_async()
666            .await
667            .map_err(|e| Error::Storage(format!("checkpoint: {e}")))?;
668
669        let cursor = self.cursor.encode()?;
670        self.storage
671            .put("cursors", &self.id.as_hex(), cursor)
672            .await?;
673        let meta = codec::encode(&self.meta)?;
674        self.storage
675            .put("groups", &format!("{}/meta", self.id.as_hex()), meta)
676            .await?;
677        // [CR-2] Persist the device→leaf map so revoke_device works after a cold restart.
678        // Use a stable BTreeMap-of-pairs encoding to guarantee canonical CBOR — every
679        // platform that decodes this hits identical bytes.
680        let leaves_vec: Vec<(DeviceId, u32)> = self
681            .device_leaves
682            .iter()
683            .map(|(d, i)| (d.clone(), *i))
684            .collect();
685        let leaves_bytes = codec::encode(&leaves_vec)?;
686        self.storage
687            .put("device_leaves", &self.id.as_hex(), leaves_bytes)
688            .await?;
689        Ok(())
690    }
691}
692
693/// Both halves of an Add commit. The Commit goes on the conversation channel; the Welcome is
694/// delivered to the new members via whatever out-of-band path the host uses (often the same
695/// transport, addressed to the new device's mailbox).
696#[derive(Debug, Clone)]
697pub struct AddOutcome {
698    pub commit: MessageEnvelope,
699    pub welcome: MessageEnvelope,
700}
701
702fn mls_message_out_bytes(m: MlsMessageOut) -> Result<Vec<u8>> {
703    m.tls_serialize_detached().map_err(Error::mls)
704}
ping_core/conversation.rs

ping_core/
conversation.rs
