refactor: expose more functions in TreeKEM API

fstar/api/MLS.fst

@@ -257,7 +257,7 @@ let process_commit state wire_format message message_auth =
   let state = { state with confirmed_transcript_hash; interim_transcript_hash } in
   // 4. Check confirmation tag
   let? () = (
-    let confirmation_key = state.treekem_state.keyschedule_state.epoch_keys.confirmation_key in
+    let confirmation_key = (MLS.TreeKEM.API.get_epoch_keys state.treekem_state).confirmation_key in
     let? confirmation_tag_ok = MLS.TreeDEM.API.verify_confirmation_tag state.treedem_state full_message confirmation_key confirmed_transcript_hash in
     if not confirmation_tag_ok then
       error "process_commit: invalid confirmation tag"
@@ -276,8 +276,8 @@ let process_commit state wire_format message message_auth =
     my_leaf_index;
     group_context;
     encryption_secret;
-    sender_data_secret = state.treekem_state.keyschedule_state.epoch_keys.sender_data_secret;
-    membership_key = state.treekem_state.keyschedule_state.epoch_keys.membership_key;
+    sender_data_secret = (MLS.TreeKEM.API.get_epoch_keys state.treekem_state).sender_data_secret;
+    membership_key = (MLS.TreeKEM.API.get_epoch_keys state.treekem_state).membership_key;
     my_signature_key = state.sign_private_key;
     verification_keys = get_verification_keys state.treesync_state.tree;
   } in
@@ -392,8 +392,8 @@ let create e cred private_sign_key group_id =
     my_leaf_index = leaf_index;
     group_context;
     encryption_secret;
-    sender_data_secret = treekem_state.keyschedule_state.epoch_keys.sender_data_secret;
-    membership_key = treekem_state.keyschedule_state.epoch_keys.membership_key;
+    sender_data_secret = (MLS.TreeKEM.API.get_epoch_keys treekem_state).sender_data_secret;
+    membership_key = (MLS.TreeKEM.API.get_epoch_keys treekem_state).membership_key;
     my_signature_key = private_sign_key;
     verification_keys = get_verification_keys treesync_state.tree;
   } in
@@ -577,7 +577,7 @@ let generate_commit state e proposals =
   let new_group_context = { provisional_group_context with confirmed_transcript_hash } in
   let? commit_result = MLS.TreeKEM.API.finalize_create_commit pending_commit new_group_context None in
   let state = { state with pending_updatepath = (update_path, (commit_result.new_state, commit_result.encryption_secret))::state.pending_updatepath } in
-  let? auth_commit = MLS.TreeDEM.API.finish_authenticate_commit half_auth_commit commit_result.new_state.keyschedule_state.epoch_keys.confirmation_key confirmed_transcript_hash in
+  let? auth_commit = MLS.TreeDEM.API.finish_authenticate_commit half_auth_commit (MLS.TreeKEM.API.get_epoch_keys commit_result.new_state).confirmation_key confirmed_transcript_hash in
   let? reuse_guard, e = chop_entropy e 4 in
   assume(Seq.length reuse_guard == length #bytes reuse_guard);
   let? (commit_ct, new_treedem_state) = MLS.TreeDEM.API.protect_private state.treedem_state auth_commit reuse_guard in
@@ -703,7 +703,7 @@ let process_welcome_message w (sign_pk, sign_sk) lookup =
   let? group_context = compute_group_context group_id epoch tree_hash confirmed_transcript_hash in
 
   let? () = (
-    let? computed_confirmation_tag = MLS.TreeDEM.Message.Framing.compute_message_confirmation_tag treekem_state.keyschedule_state.epoch_keys.confirmation_key confirmed_transcript_hash in
+    let? computed_confirmation_tag = MLS.TreeDEM.Message.Framing.compute_message_confirmation_tag (MLS.TreeKEM.API.get_epoch_keys treekem_state).confirmation_key confirmed_transcript_hash in
     if not ((group_info.tbs.confirmation_tag <: bytes) = (computed_confirmation_tag <: bytes)) then
       error "process_welcome_message: bad confirmation_tag"
     else return ()
@@ -714,8 +714,8 @@ let process_welcome_message w (sign_pk, sign_sk) lookup =
     my_leaf_index = leaf_index;
     group_context;
     encryption_secret;
-    sender_data_secret = treekem_state.keyschedule_state.epoch_keys.sender_data_secret;
-    membership_key = treekem_state.keyschedule_state.epoch_keys.membership_key;
+    sender_data_secret = (MLS.TreeKEM.API.get_epoch_keys treekem_state).sender_data_secret;
+    membership_key = (MLS.TreeKEM.API.get_epoch_keys treekem_state).membership_key;
     my_signature_key = sign_sk;
     verification_keys = get_verification_keys treesync_state.tree;
   } in

fstar/treedem/MLS.TreeDEM.NetworkTypes.fst

@@ -109,6 +109,8 @@ type proposal_nt (bytes:Type0) {|bytes_like bytes|} =
 
 %splice [ps_proposal_nt] (gen_parser (`proposal_nt))
 
+instance parseable_serializeable_proposal_nt (bytes:Type0) {|bytes_like bytes|}: parseable_serializeable bytes (proposal_nt bytes) = mk_parseable_serializeable ps_proposal_nt
+
 /// enum {
 ///   reserved(0),
 ///   proposal(1),

fstar/treekem/code/MLS.TreeKEM.API.KeySchedule.fst

@@ -55,3 +55,11 @@ let commit #bytes #cb st opt_commit_secret opt_psk new_group_context =
     joiner_secret;
     welcome_secret;
   })
+
+val export:
+  #bytes:Type0 -> {|crypto_bytes bytes|} ->
+  treekem_keyschedule_state bytes ->
+  valid_label -> bytes -> len:nat ->
+  result (lbytes bytes len)
+let export #bytes #cb st label context len =
+  mls_exporter st.epoch_keys.exporter_secret label context len

fstar/treekem/code/MLS.TreeKEM.API.fst

@@ -186,3 +186,20 @@ let finalize_create_commit #bytes #cb #leaf_ind pending new_group_context opt_ps
     welcome_secret = additional_secrets.welcome_secret;
     joiner_secret = additional_secrets.joiner_secret;
   }
+
+(*** Getters ***)
+
+val get_epoch_keys:
+  #bytes:Type0 -> {|crypto_bytes bytes|} -> #leaf_ind:nat ->
+  treekem_state bytes leaf_ind ->
+  epoch_keys bytes
+let get_epoch_keys #bytes #cb #leaf_ind st =
+  st.keyschedule_state.epoch_keys
+
+val export:
+  #bytes:Type0 -> {|crypto_bytes bytes|} -> #leaf_ind:nat ->
+  treekem_state bytes leaf_ind ->
+  valid_label -> bytes -> len:nat ->
+  result (lbytes bytes len)
+let export #bytes #cb st label context len =
+  KS.export st.keyschedule_state label context len