Implementation of server_remove proposal

mls-rs-core/Cargo.toml

@@ -23,6 +23,7 @@ serde = ["dep:serde", "zeroize/serde", "hex/serde", "dep:serde_bytes"]
 last_resort_key_package_ext = []
 post-quantum = []
 self_remove_proposal = []
+gsma_rcs_e2ee_feature = []
 
 [dependencies]
 mls-rs-codec = { version = "0.6", path = "../mls-rs-codec", default-features = false}

mls-rs-core/src/group/proposal_type.rs

@@ -58,6 +58,8 @@ impl ProposalType {
     pub const GROUP_CONTEXT_EXTENSIONS: ProposalType = ProposalType(7);
     #[cfg(feature = "self_remove_proposal")]
     pub const SELF_REMOVE: ProposalType = ProposalType(0xF003);
+    #[cfg(feature = "gsma_rcs_e2ee_feature")]
+    pub const SERVER_REMOVE: ProposalType = ProposalType(0xF004);
 
     /// Default proposal types defined
     /// in [RFC 9420](https://www.rfc-editor.org/rfc/rfc9420.html#name-leaf-node-contents)

mls-rs/Cargo.toml

@@ -36,6 +36,7 @@ x509 = ["mls-rs-core/x509", "dep:mls-rs-identity-x509"]
 rfc_compliant = ["private_message", "custom_proposal", "out_of_order", "psk", "x509", "prior_epoch", "by_ref_proposal", "mls-rs-core/rfc_compliant"]
 last_resort_key_package_ext = ["mls-rs-core/last_resort_key_package_ext"]
 self_remove_proposal = ["mls-rs-core/self_remove_proposal"]
+gsma_rcs_e2ee_feature = ["mls-rs-core/gsma_rcs_e2ee_feature"]
 
 std = ["mls-rs-core/std", "mls-rs-codec/std", "mls-rs-identity-x509?/std", "hex/std", "futures/std", "itertools/use_std", "safer-ffi-gen?/std", "zeroize/std", "dep:debug_tree", "dep:thiserror", "serde?/std"]
 

mls-rs/src/external_client/group.rs

@@ -43,6 +43,8 @@ use crate::{
     feature = "self_remove_proposal"
 ))]
 use crate::group::proposal::SelfRemoveProposal;
+#[cfg(feature = "gsma_rcs_e2ee_feature")]
+use crate::group::proposal::ServerRemoveProposal;
 
 #[cfg(feature = "by_ref_proposal")]
 use crate::{
@@ -699,6 +701,15 @@ where
         None
     }
 
+    #[cfg(feature = "gsma_rcs_e2ee_feature")]
+    #[cfg_attr(feature = "ffi", safer_ffi_gen::safer_ffi_gen_ignore)]
+    fn server_removal_proposal(
+        &self,
+        _provisional_state: &ProvisionalState,
+    ) -> Option<ProposalInfo<ServerRemoveProposal>> {
+        None
+    }
+
     #[cfg(feature = "private_message")]
     fn min_epoch_available(&self) -> Option<u64> {
         self.config

mls-rs/src/group/commit.rs

@@ -225,6 +225,15 @@ where
         Ok(self)
     }
 
+    /// Insert a [`ServerRemoveProposal`](crate::group::proposal::RemoveProposal) into
+    /// the current commit that is being built.
+    #[cfg(feature = "gsma_rcs_e2ee_feature")]
+    pub fn server_remove_member(mut self, index: u32) -> Result<Self, MlsError> {
+        let proposal = self.group.server_remove_proposal(index)?;
+        self.proposals.push(proposal);
+        Ok(self)
+    }
+
     /// Insert a
     /// [`GroupContextExtensions`](crate::group::proposal::Proposal::GroupContextExtensions)
     /// into the current commit that is being built.

mls-rs/src/group/external_commit.rs

@@ -18,6 +18,9 @@ use crate::{
     Group, MlsMessage,
 };
 
+#[cfg(feature = "gsma_rcs_e2ee_feature")]
+use crate::group::proposal::ServerRemoveProposal;
+
 #[cfg(any(feature = "secret_tree_access", feature = "private_message"))]
 use crate::group::secret_tree::SecretTree;
 
@@ -52,6 +55,8 @@ pub struct ExternalCommitBuilder<C: ClientConfig> {
     config: C,
     tree_data: Option<ExportedTree<'static>>,
     to_remove: Option<u32>,
+    #[cfg(feature = "gsma_rcs_e2ee_feature")]
+    to_server_remove: Vec<u32>,
     #[cfg(feature = "psk")]
     external_psks: Vec<ExternalPskId>,
     authenticated_data: Vec<u8>,
@@ -70,6 +75,8 @@ impl<C: ClientConfig> ExternalCommitBuilder<C> {
         Self {
             tree_data: None,
             to_remove: None,
+            #[cfg(feature = "gsma_rcs_e2ee_feature")]
+            to_server_remove: Vec::new(),
             authenticated_data: Vec::new(),
             signer,
             signing_identity,
@@ -104,6 +111,21 @@ impl<C: ClientConfig> ExternalCommitBuilder<C> {
         }
     }
 
+    #[cfg(feature = "gsma_rcs_e2ee_feature")]
+    #[must_use]
+    /// Propose the server-removal of a client as part of the external commit.
+    pub fn with_server_removal(self, to_remove: u32) -> Self {
+        Self {
+            to_server_remove: self
+                .to_server_remove
+                .iter()
+                .chain([&to_remove])
+                .cloned()
+                .collect(),
+            ..self
+        }
+    }
+
     #[must_use]
     /// Add plaintext authenticated data to the resulting commit message.
     pub fn with_authenticated_data(self, data: Vec<u8>) -> Self {
@@ -265,6 +287,13 @@ impl<C: ClientConfig> ExternalCommitBuilder<C> {
             }));
         }
 
+        #[cfg(feature = "gsma_rcs_e2ee_feature")]
+        for index_to_remove in self.to_server_remove {
+            proposals.push(Proposal::ServerRemove(ServerRemoveProposal {
+                to_remove: LeafIndex(index_to_remove),
+            }));
+        }
+
         let (commit_output, pending_commit) = group
             .commit_internal(
                 proposals,

mls-rs/src/group/message_processor.rs

@@ -8,6 +8,8 @@
     feature = "self_remove_proposal"
 ))]
 use super::SelfRemoveProposal;
+#[cfg(feature = "gsma_rcs_e2ee_feature")]
+use super::ServerRemoveProposal;
 use super::{
     commit_sender,
     confirmation_tag::ConfirmationTag,
@@ -91,6 +93,9 @@ pub(crate) fn path_update_required(proposals: &ProposalBundle) -> bool {
     ))]
     let res = res || !proposals.self_removes.is_empty();
 
+    #[cfg(feature = "gsma_rcs_e2ee_feature")]
+    let res = res || !proposals.server_removes.is_empty();
+
     res || proposals.length() == 0
         || proposals.group_context_extensions_proposal().is_some()
         || !proposals.remove_proposals().is_empty()
@@ -727,6 +732,9 @@ pub(crate) trait MessageProcessor: Send + Sync {
         ))]
         let self_removed_by_self = self.self_removal_proposal(&provisional_state);
 
+        #[cfg(feature = "gsma_rcs_e2ee_feature")]
+        let self_removed_by_server = self.server_removal_proposal(&provisional_state);
+
         let is_self_removed = self_removed.is_some();
         #[cfg(all(
             feature = "by_ref_proposal",
@@ -735,6 +743,9 @@ pub(crate) trait MessageProcessor: Send + Sync {
         ))]
         let is_self_removed = is_self_removed || self_removed_by_self.is_some();
 
+        #[cfg(feature = "gsma_rcs_e2ee_feature")]
+        let is_self_removed = is_self_removed || self_removed_by_server.is_some();
+
         let update_path = match commit.path {
             Some(update_path) => Some(
                 validate_update_path(
@@ -783,6 +794,17 @@ pub(crate) trait MessageProcessor: Send + Sync {
             commit_effect
         };
 
+        #[cfg(feature = "gsma_rcs_e2ee_feature")]
+        let commit_effect = if let Some(server_remove_proposal) = self_removed_by_server {
+            let new_epoch = NewEpoch::new(self.group_state().clone(), &provisional_state);
+            CommitEffect::Removed {
+                remover: server_remove_proposal.sender,
+                new_epoch: Box::new(new_epoch),
+            }
+        } else {
+            commit_effect
+        };
+
         let new_secrets = match update_path {
             Some(update_path) if !is_self_removed => {
                 self.apply_update_path(sender, &update_path, &mut provisional_state)
@@ -851,6 +873,13 @@ pub(crate) trait MessageProcessor: Send + Sync {
         provisional_state: &ProvisionalState,
     ) -> Option<ProposalInfo<SelfRemoveProposal>>;
 
+    #[cfg(feature = "gsma_rcs_e2ee_feature")]
+    #[cfg_attr(feature = "ffi", safer_ffi_gen::safer_ffi_gen_ignore)]
+    fn server_removal_proposal(
+        &self,
+        provisional_state: &ProvisionalState,
+    ) -> Option<ProposalInfo<ServerRemoveProposal>>;
+
     #[cfg(feature = "private_message")]
     fn min_epoch_available(&self) -> Option<u64>;