Add support for MSC3202: sending one-time key counts and fallback key usage states to Application Services. (#11617)

Co-authored-by: Erik Johnston <erik@matrix.org>

2 files changed, 23 insertions, 6 deletions

diff --git a/synapse/config/appservice.py b/synapse/config/appservice.py

index 7fad2e0422..439bfe1526 100644
--- a/synapse/config/appservice.py
+++ b/synapse/config/appservice.py
@@ -166,6 +166,16 @@ def _load_appservice(
 
     supports_ephemeral = as_info.get("de.sorunome.msc2409.push_ephemeral", False)
 
+    # Opt-in flag for the MSC3202-specific transactional behaviour.
+    # When enabled, appservice transactions contain the following information:
+    #  - device One-Time Key counts
+    #  - device unused fallback key usage states
+    msc3202_transaction_extensions = as_info.get("org.matrix.msc3202", False)
+    if not isinstance(msc3202_transaction_extensions, bool):
+        raise ValueError(
+            "The `org.matrix.msc3202` option should be true or false if specified."
+        )
+
     return ApplicationService(
         token=as_info["as_token"],
         hostname=hostname,
@@ -174,8 +184,9 @@ def _load_appservice(
         hs_token=as_info["hs_token"],
         sender=user_id,
         id=as_info["id"],
-        supports_ephemeral=supports_ephemeral,
         protocols=protocols,
         rate_limited=rate_limited,
         ip_range_whitelist=ip_range_whitelist,
+        supports_ephemeral=supports_ephemeral,
+        msc3202_transaction_extensions=msc3202_transaction_extensions,
     )
diff --git a/synapse/config/experimental.py b/synapse/config/experimental.py

index 772eb35013..41338b39df 100644
--- a/synapse/config/experimental.py
+++ b/synapse/config/experimental.py
@@ -47,11 +47,6 @@ class ExperimentalConfig(Config):
         # MSC3030 (Jump to date API endpoint)
         self.msc3030_enabled: bool = experimental.get("msc3030_enabled", False)
 
-        # The portion of MSC3202 which is related to device masquerading.
-        self.msc3202_device_masquerading_enabled: bool = experimental.get(
-            "msc3202_device_masquerading", False
-        )
-
         # MSC2409 (this setting only relates to optionally sending to-device messages).
         # Presence, typing and read receipt EDUs are already sent to application services that
         # have opted in to receive them. If enabled, this adds to-device messages to that list.
@@ -59,6 +54,17 @@ class ExperimentalConfig(Config):
             "msc2409_to_device_messages_enabled", False
         )
 
+        # The portion of MSC3202 which is related to device masquerading.
+        self.msc3202_device_masquerading_enabled: bool = experimental.get(
+            "msc3202_device_masquerading", False
+        )
+
+        # Portion of MSC3202 related to transaction extensions:
+        # sending one-time key counts and fallback key usage to application services.
+        self.msc3202_transaction_extensions: bool = experimental.get(
+            "msc3202_transaction_extensions", False
+        )
+
         # MSC3706 (server-side support for partial state in /send_join responses)
         self.msc3706_enabled: bool = experimental.get("msc3706_enabled", False)