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//! A MLS group can be merged (aka committed) when it has a pending commit. The latter is a commit
//! we created which is still waiting to be "committed". By doing so, we will apply all the
//! modifications present in the commit to the ratchet tree and also persist the new group in the
//! keystore. Like this, even if the application crashes we will be able to restore.
//!
//! This table summarizes when a MLS group can be merged:
//!
//! | can be merged ? | 0 pend. Commit | 1 pend. Commit |
//! |-------------------|----------------|----------------|
//! | 0 pend. Proposal | ❌ | ✅ |
//! | 1+ pend. Proposal | ❌ | ✅ |
//!
use core_crypto_keystore::entities::{MlsEncryptionKeyPair, MlsPendingMessage};
use openmls::prelude::MlsGroupStateError;
use openmls_traits::OpenMlsCryptoProvider;
use mls_crypto_provider::MlsCryptoProvider;
use crate::context::CentralContext;
use crate::{
mls::{ConversationId, MlsConversation},
prelude::{decrypt::MlsBufferedConversationDecryptMessage, MlsProposalRef},
CryptoError, CryptoResult, MlsError,
};
/// Abstraction over a MLS group capable of merging a commit
impl MlsConversation {
/// see [CentralContext::commit_accepted]
#[cfg_attr(test, crate::durable)]
pub async fn commit_accepted(&mut self, backend: &MlsCryptoProvider) -> CryptoResult<()> {
// openmls stores here all the encryption keypairs used for update proposals..
let previous_own_leaf_nodes = self.group.own_leaf_nodes.clone();
self.group.merge_pending_commit(backend).await.map_err(MlsError::from)?;
self.persist_group_when_changed(&backend.keystore(), false).await?;
// ..so if there's any, we clear them after the commit is merged
for oln in &previous_own_leaf_nodes {
let ek = oln.encryption_key().as_slice();
let _ = backend.key_store().remove::<MlsEncryptionKeyPair, _>(ek).await;
}
Ok(())
}
/// see [CentralContext::clear_pending_proposal]
#[cfg_attr(test, crate::durable)]
pub async fn clear_pending_proposal(
&mut self,
proposal_ref: MlsProposalRef,
backend: &MlsCryptoProvider,
) -> CryptoResult<()> {
self.group
.remove_pending_proposal(backend.key_store(), &proposal_ref)
.await
.map_err(|e| match e {
MlsGroupStateError::PendingProposalNotFound => CryptoError::PendingProposalNotFound(proposal_ref),
_ => CryptoError::from(MlsError::from(e)),
})?;
self.persist_group_when_changed(&backend.keystore(), true).await?;
Ok(())
}
/// see [CentralContext::clear_pending_commit]
#[cfg_attr(test, crate::durable)]
pub async fn clear_pending_commit(&mut self, backend: &MlsCryptoProvider) -> CryptoResult<()> {
if self.group.pending_commit().is_some() {
self.group.clear_pending_commit();
self.persist_group_when_changed(&backend.keystore(), true).await?;
Ok(())
} else {
Err(CryptoError::PendingCommitNotFound)
}
}
}
/// A MLS group is a distributed object scattered across many parties. We use a Delivery Service
/// to orchestrate those parties. So when we create a commit, a mutable operation, it has to be
/// validated by the Delivery Service. But it might occur that another group member did the
/// exact same thing at the same time. So if we arrive second in this race, we must "rollback" the commit
/// we created and accept ("merge") the other one.
/// A client would
/// * Create a commit
/// * Send the commit to the Delivery Service
/// * When Delivery Service responds
/// * 200 OK --> use [CentralContext::commit_accepted] to merge the commit
/// * 409 CONFLICT --> do nothing. [CentralContext::decrypt_message] will restore the proposals not committed
/// * 5xx --> retry
impl CentralContext {
/// The commit we created has been accepted by the Delivery Service. Hence it is guaranteed
/// to be used for the new epoch.
/// We can now safely "merge" it (effectively apply the commit to the group) and update it
/// in the keystore. The previous can be discarded to respect Forward Secrecy.
pub async fn commit_accepted(
&self,
id: &ConversationId,
) -> CryptoResult<Option<Vec<MlsBufferedConversationDecryptMessage>>> {
let conv = self.get_conversation(id).await?;
let mut conv = conv.write().await;
conv.commit_accepted(&self.mls_provider().await?).await?;
let pending_messages = self.restore_pending_messages(&mut conv, false).await?;
if pending_messages.is_some() {
self.keystore().await?.remove::<MlsPendingMessage, _>(id).await?;
}
Ok(pending_messages)
}
/// Allows to remove a pending (uncommitted) proposal. Use this when backend rejects the proposal
/// you just sent e.g. if permissions have changed meanwhile.
///
/// **CAUTION**: only use this when you had an explicit response from the Delivery Service
/// e.g. 403 or 409. Do not use otherwise e.g. 5xx responses, timeout etc..
///
/// # Arguments
/// * `conversation_id` - the group/conversation id
/// * `proposal_ref` - unique proposal identifier which is present in [crate::prelude::MlsProposalBundle]
/// and returned from all operation creating a proposal
///
/// # Errors
/// When the conversation is not found or the proposal reference does not identify a proposal
/// in the local pending proposal store
pub async fn clear_pending_proposal(
&self,
conversation_id: &ConversationId,
proposal_ref: MlsProposalRef,
) -> CryptoResult<()> {
self.get_conversation(conversation_id)
.await?
.write()
.await
.clear_pending_proposal(proposal_ref, &self.mls_provider().await?)
.await
}
/// Allows to remove a pending commit. Use this when backend rejects the commit
/// you just sent e.g. if permissions have changed meanwhile.
///
/// **CAUTION**: only use this when you had an explicit response from the Delivery Service
/// e.g. 403. Do not use otherwise e.g. 5xx responses, timeout etc..
/// **DO NOT** use when Delivery Service responds 409, pending state will be renewed
/// in [CentralContext::decrypt_message]
///
/// # Arguments
/// * `conversation_id` - the group/conversation id
///
/// # Errors
/// When the conversation is not found or there is no pending commit
#[cfg_attr(test, crate::idempotent)]
pub async fn clear_pending_commit(&self, conversation_id: &ConversationId) -> CryptoResult<()> {
self.get_conversation(conversation_id)
.await?
.write()
.await
.clear_pending_commit(&self.mls_provider().await?)
.await
}
}
#[cfg(test)]
mod tests {
use openmls::prelude::Proposal;
use wasm_bindgen_test::*;
use crate::test_utils::*;
use super::*;
wasm_bindgen_test_configure!(run_in_browser);
mod commit_accepted {
use super::*;
#[apply(all_cred_cipher)]
#[wasm_bindgen_test]
async fn should_apply_pending_commit(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();
alice_central.invite_all(&case, &id, [&bob_central]).await.unwrap();
assert_eq!(alice_central.get_conversation_unchecked(&id).await.members().len(), 2);
alice_central
.context
.remove_members_from_conversation(&id, &[bob_central.get_client_id().await])
.await
.unwrap();
assert_eq!(alice_central.get_conversation_unchecked(&id).await.members().len(), 2);
alice_central.context.commit_accepted(&id).await.unwrap();
assert_eq!(alice_central.get_conversation_unchecked(&id).await.members().len(), 1);
})
})
.await
}
#[apply(all_cred_cipher)]
#[wasm_bindgen_test]
async fn should_clear_pending_commit_and_proposals(case: TestCase) {
run_test_with_client_ids(
case.clone(),
["alice", "bob"],
move |[mut 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();
alice_central.context.new_update_proposal(&id).await.unwrap();
let bob = bob_central.rand_key_package(&case).await;
alice_central
.context
.add_members_to_conversation(&id, vec![bob])
.await
.unwrap();
assert!(!alice_central.pending_proposals(&id).await.is_empty());
assert!(alice_central.pending_commit(&id).await.is_some());
alice_central.context.commit_accepted(&id).await.unwrap();
assert!(alice_central.pending_commit(&id).await.is_none());
assert!(alice_central.pending_proposals(&id).await.is_empty());
})
},
)
.await
}
#[apply(all_cred_cipher)]
#[wasm_bindgen_test]
async fn should_clean_associated_key_material(case: TestCase) {
run_test_with_client_ids(case.clone(), ["alice"], move |[alice_central]| {
Box::pin(async move {
let id = conversation_id();
alice_central
.context
.new_conversation(&id, case.credential_type, case.cfg.clone())
.await
.unwrap();
let initial_count = alice_central.context.count_entities().await;
alice_central.context.new_update_proposal(&id).await.unwrap();
let post_proposal_count = alice_central.context.count_entities().await;
assert_eq!(
post_proposal_count.encryption_keypair,
initial_count.encryption_keypair + 1
);
alice_central.context.commit_pending_proposals(&id).await.unwrap();
alice_central.context.commit_accepted(&id).await.unwrap();
let final_count = alice_central.context.count_entities().await;
assert_eq!(initial_count, final_count);
})
})
.await
}
}
mod clear_pending_proposal {
use super::*;
#[apply(all_cred_cipher)]
#[wasm_bindgen_test]
pub async fn should_remove_proposal(case: TestCase) {
run_test_with_client_ids(
case.clone(),
["alice", "bob", "charlie"],
move |[mut alice_central, bob_central, charlie_central]| {
Box::pin(async move {
let id = conversation_id();
alice_central
.context
.new_conversation(&id, case.credential_type, case.cfg.clone())
.await
.unwrap();
alice_central.invite_all(&case, &id, [&bob_central]).await.unwrap();
assert!(alice_central.pending_proposals(&id).await.is_empty());
let charlie_kp = charlie_central.get_one_key_package(&case).await;
let add_ref = alice_central
.context
.new_add_proposal(&id, charlie_kp)
.await
.unwrap()
.proposal_ref;
let remove_ref = alice_central
.context
.new_remove_proposal(&id, bob_central.get_client_id().await)
.await
.unwrap()
.proposal_ref;
let update_ref = alice_central
.context
.new_update_proposal(&id)
.await
.unwrap()
.proposal_ref;
assert_eq!(alice_central.pending_proposals(&id).await.len(), 3);
alice_central
.context
.clear_pending_proposal(&id, add_ref)
.await
.unwrap();
assert_eq!(alice_central.pending_proposals(&id).await.len(), 2);
assert!(!alice_central
.pending_proposals(&id)
.await
.into_iter()
.any(|p| matches!(p.proposal(), Proposal::Add(_))));
alice_central
.context
.clear_pending_proposal(&id, remove_ref)
.await
.unwrap();
assert_eq!(alice_central.pending_proposals(&id).await.len(), 1);
assert!(!alice_central
.pending_proposals(&id)
.await
.into_iter()
.any(|p| matches!(p.proposal(), Proposal::Remove(_))));
alice_central
.context
.clear_pending_proposal(&id, update_ref)
.await
.unwrap();
assert!(alice_central.pending_proposals(&id).await.is_empty());
assert!(!alice_central
.pending_proposals(&id)
.await
.into_iter()
.any(|p| matches!(p.proposal(), Proposal::Update(_))));
})
},
)
.await
}
#[apply(all_cred_cipher)]
#[wasm_bindgen_test]
pub async fn should_fail_when_conversation_not_found(case: TestCase) {
run_test_with_client_ids(case.clone(), ["alice"], move |[alice_central]| {
Box::pin(async move {
let id = conversation_id();
let simple_ref = MlsProposalRef::from(vec![0; case.ciphersuite().hash_length()]);
let clear = alice_central.context.clear_pending_proposal(&id, simple_ref).await;
assert!(matches!(clear.unwrap_err(), CryptoError::ConversationNotFound(conv_id) if conv_id == id))
})
})
.await
}
#[apply(all_cred_cipher)]
#[wasm_bindgen_test]
pub async fn should_fail_when_proposal_ref_not_found(case: TestCase) {
run_test_with_client_ids(case.clone(), ["alice"], move |[mut alice_central]| {
Box::pin(async move {
let id = conversation_id();
alice_central
.context.new_conversation(&id, case.credential_type, case.cfg.clone())
.await
.unwrap();
assert!(alice_central.pending_proposals(&id).await.is_empty());
let any_ref = MlsProposalRef::from(vec![0; case.ciphersuite().hash_length()]);
let clear = alice_central.context.clear_pending_proposal(&id, any_ref.clone()).await;
assert!(matches!(clear.unwrap_err(), CryptoError::PendingProposalNotFound(prop_ref) if prop_ref == any_ref))
})
})
.await
}
#[apply(all_cred_cipher)]
#[wasm_bindgen_test]
pub async fn should_clean_associated_key_material(case: TestCase) {
run_test_with_client_ids(case.clone(), ["alice"], move |[mut cc]| {
Box::pin(async move {
let id = conversation_id();
cc.context
.new_conversation(&id, case.credential_type, case.cfg.clone())
.await
.unwrap();
assert!(cc.pending_proposals(&id).await.is_empty());
let init = cc.context.count_entities().await;
let proposal_ref = cc.context.new_update_proposal(&id).await.unwrap().proposal_ref;
assert_eq!(cc.pending_proposals(&id).await.len(), 1);
cc.context.clear_pending_proposal(&id, proposal_ref).await.unwrap();
assert!(cc.pending_proposals(&id).await.is_empty());
// This whole flow should be idempotent.
// Here we verify that we are indeed deleting the `EncryptionKeyPair` created
// for the Update proposal
let after_clear_proposal = cc.context.count_entities().await;
assert_eq!(init, after_clear_proposal);
})
})
.await
}
}
mod clear_pending_commit {
use super::*;
#[apply(all_cred_cipher)]
#[wasm_bindgen_test]
pub async fn should_remove_commit(case: TestCase) {
run_test_with_client_ids(case.clone(), ["alice"], move |[alice_central]| {
Box::pin(async move {
let id = conversation_id();
alice_central
.context
.new_conversation(&id, case.credential_type, case.cfg.clone())
.await
.unwrap();
assert!(alice_central.pending_commit(&id).await.is_none());
alice_central.context.update_keying_material(&id).await.unwrap();
assert!(alice_central.pending_commit(&id).await.is_some());
alice_central.context.clear_pending_commit(&id).await.unwrap();
assert!(alice_central.pending_commit(&id).await.is_none());
})
})
.await
}
#[apply(all_cred_cipher)]
#[wasm_bindgen_test]
pub async fn should_fail_when_conversation_not_found(case: TestCase) {
run_test_with_client_ids(case.clone(), ["alice"], move |[alice_central]| {
Box::pin(async move {
let id = conversation_id();
let clear = alice_central.context.clear_pending_commit(&id).await;
assert!(matches!(clear.unwrap_err(), CryptoError::ConversationNotFound(conv_id) if conv_id == id))
})
})
.await
}
#[apply(all_cred_cipher)]
#[wasm_bindgen_test]
pub async fn should_fail_when_pending_commit_absent(case: TestCase) {
run_test_with_client_ids(case.clone(), ["alice"], move |[alice_central]| {
Box::pin(async move {
let id = conversation_id();
alice_central
.context
.new_conversation(&id, case.credential_type, case.cfg.clone())
.await
.unwrap();
assert!(alice_central.pending_commit(&id).await.is_none());
let clear = alice_central.context.clear_pending_commit(&id).await;
assert!(matches!(clear.unwrap_err(), CryptoError::PendingCommitNotFound))
})
})
.await
}
#[apply(all_cred_cipher)]
#[wasm_bindgen_test]
pub async fn should_clean_associated_key_material(case: TestCase) {
run_test_with_client_ids(case.clone(), ["alice"], move |[cc]| {
Box::pin(async move {
let id = conversation_id();
cc.context
.new_conversation(&id, case.credential_type, case.cfg.clone())
.await
.unwrap();
assert!(cc.pending_commit(&id).await.is_none());
let init = cc.context.count_entities().await;
cc.context.update_keying_material(&id).await.unwrap();
assert!(cc.pending_commit(&id).await.is_some());
cc.context.clear_pending_commit(&id).await.unwrap();
assert!(cc.pending_commit(&id).await.is_none());
// This whole flow should be idempotent.
// Here we verify that we are indeed deleting the `EncryptionKeyPair` created
// for the Update commit
let after_clear_commit = cc.context.count_entities().await;
assert_eq!(init, after_clear_commit);
})
})
.await
}
}
}