Bump mls-rs to the germ-integration pin, and keep APP_DATA_UPDATE pathless

.changeset/cyan-donkeys-shave.md

@@ -0,0 +1,29 @@
+---
+"@germ-network/two-mls-pq": patch
+---
+
+Bump mls-rs to the `germ-integration` pin, and keep `APP_DATA_UPDATE` pathless
+
+The fork's `main` was resynced with upstream `awslabs/mls-rs`, and the Germ changes were
+recomposed on top of it as `germ-integration`. The pin moves from `ec69dc25` to
+`c6ede1ce`, picking up the crypto providers, a recovered cryptokit build fix, the Safe
+Extensions exporter tree, and attachment CEK derivation.
+
+The resync requires one behavioural fix. Upstream added
+`MlsRules::custom_proposal_requires_update_path` with a default of `true`, so
+`APP_DATA_UPDATE` — an attestation that changes no group membership — began forcing an
+updatePath. On the PQ half that put an ML-KEM updatePath on a commit that must stay
+pathless: the bind commit grew past a whole ML-KEM-768 ciphertext. `TwoMlsRules` now
+overrides the hook to `false`, restoring the behaviour `apq` was written against. Where a
+path _is_ wanted — the FULL commit discharging an owed bind on the classical half —
+`commit_options` still pins it explicitly, which is where that decision belongs.
+
+Also drops `serde` — both the `mls-rs` feature and the unused `[workspace.dependencies]`
+entry. Nothing in the workspace consumes either: no `.rs` file references serde and no
+member crate declares it. mls-rs's serde derives are `cfg_attr`-attached, so they never
+participate in `MlsEncode`/`MlsDecode`; removing the feature cannot move a byte of the
+stored format. Archiving goes through the crate's own `MlsEncode`/`MlsDecode` wire
+structs, which are untouched.
+
+No wire, FFI, or error-variant change. Group state written by the previous pin still
+loads.

rust/Cargo.toml

@@ -36,22 +36,20 @@ strip = "symbols"
 mls-rs = { version = "0.55", features = [
   "psk",
   "private_message",
-  "serde",
   "safe_extensions",
 ] }
-mls-rs-core = { version = "0.27", git = "https://github.com/germ-network/mls-rs", rev = "ec69dc251db66ae6eb117079564814998bb55dec" }
-mls-rs-crypto-awslc = { version = "0.25", git = "https://github.com/germ-network/mls-rs", rev = "ec69dc251db66ae6eb117079564814998bb55dec", features = [
+mls-rs-core = { version = "0.27", git = "https://github.com/germ-network/mls-rs", rev = "b43703fbf1244140fe9e5e43e41c373e34191758" }
+mls-rs-crypto-awslc = { version = "0.25", git = "https://github.com/germ-network/mls-rs", rev = "b43703fbf1244140fe9e5e43e41c373e34191758", features = [
   "post-quantum",
 ] }
-mls-rs-crypto-cryptokit = { version = "0.11", git = "https://github.com/germ-network/mls-rs", rev = "ec69dc251db66ae6eb117079564814998bb55dec", features = [
+mls-rs-crypto-cryptokit = { version = "0.11", git = "https://github.com/germ-network/mls-rs", rev = "b43703fbf1244140fe9e5e43e41c373e34191758", features = [
   "post-quantum",
 ] }
-mls-rs-crypto-traits = { version = "0.22", git = "https://github.com/germ-network/mls-rs", rev = "ec69dc251db66ae6eb117079564814998bb55dec" }
-serde = { version = "1", features = ["derive"] }
+mls-rs-crypto-traits = { version = "0.22", git = "https://github.com/germ-network/mls-rs", rev = "b43703fbf1244140fe9e5e43e41c373e34191758" }
 sha2 = "0.10"
 thiserror = "1"
 uniffi = "0.31"
 zeroize = { version = "1", features = ["derive"] }
 
 [patch.crates-io]
-mls-rs = { git = "https://github.com/germ-network/mls-rs", rev = "ec69dc251db66ae6eb117079564814998bb55dec" }
+mls-rs = { git = "https://github.com/germ-network/mls-rs", rev = "b43703fbf1244140fe9e5e43e41c373e34191758" }

rust/apq/src/rules.rs

@@ -18,7 +18,7 @@
 
 use mls_rs::{
     error::IntoAnyError,
-    group::{GroupContext, Roster, Sender},
+    group::{proposal::ProposalType, GroupContext, Roster, Sender},
     mls_rules::{CommitDirection, CommitOptions, CommitSource, EncryptionOptions, ProposalBundle},
     MlsRules,
 };
@@ -74,6 +74,29 @@ pub struct TwoMlsRules;
 impl MlsRules for TwoMlsRules {
     type Error = RuleError;
 
+    /// `APP_DATA_UPDATE` never forces an updatePath.
+    ///
+    /// It carries an attestation only — it does not change group membership — so RFC 9420
+    /// §12.4 leaves the path at the committer's discretion. The PQ half depends on that:
+    /// a bind commit must stay pathless, or it carries an ML-KEM updatePath and grows past
+    /// a whole ML-KEM-768 ciphertext (`test_bind_pq_commit_is_pathless`).
+    ///
+    /// Where a path IS wanted on the classical half — the FULL commit discharging an owed
+    /// bind — [`Self::commit_options`] pins it explicitly. That is the one place this
+    /// decision belongs.
+    ///
+    /// mls-rs added this hook in awslabs/mls-rs#364 with a default of `true`, which would
+    /// silently put a path on every custom proposal. Overriding it restores the behaviour
+    /// this crate was written against; it is not a new policy.
+    fn custom_proposal_requires_update_path(&self, custom_proposal_type: ProposalType) -> bool {
+        debug_assert_eq!(
+            custom_proposal_type, APP_DATA_UPDATE,
+            "filter_proposals rejects every other custom proposal type"
+        );
+        let _ = custom_proposal_type;
+        false
+    }
+
     fn filter_proposals(
         &self,
         _direction: CommitDirection,