Add flags to /versions about whether new rooms are encrypted by default. (#8343)

changelog.d/8343.feature

+Add flags to the `/versions` endpoint that includes whether new rooms default to using E2EE.

synapse/rest/client/versions.py

@@ -19,6 +19,7 @@
 import logging
 import re
 
+from synapse.api.constants import RoomCreationPreset
 from synapse.http.servlet import RestServlet
 
 logger = logging.getLogger(__name__)
@@ -31,6 +32,20 @@ class VersionsRestServlet(RestServlet):
         super(VersionsRestServlet, self).__init__()
         self.config = hs.config
 
+        # Calculate these once since they shouldn't change after start-up.
+        self.e2ee_forced_public = (
+            RoomCreationPreset.PUBLIC_CHAT
+            in self.config.encryption_enabled_by_default_for_room_presets
+        )
+        self.e2ee_forced_private = (
+            RoomCreationPreset.PRIVATE_CHAT
+            in self.config.encryption_enabled_by_default_for_room_presets
+        )
+        self.e2ee_forced_trusted_private = (
+            RoomCreationPreset.TRUSTED_PRIVATE_CHAT
+            in self.config.encryption_enabled_by_default_for_room_presets
+        )
+
     def on_GET(self, request):
         return (
             200,
@@ -62,6 +77,10 @@ class VersionsRestServlet(RestServlet):
                     "org.matrix.msc2432": True,
                     # Implements additional endpoints as described in MSC2666
                     "uk.half-shot.msc2666": True,
+                    # Whether new rooms will be set to encrypted or not (based on presets).
+                    "io.element.e2ee_forced.public": self.e2ee_forced_public,
+                    "io.element.e2ee_forced.private": self.e2ee_forced_private,
+                    "io.element.e2ee_forced.trusted_private": self.e2ee_forced_trusted_private,
                 },
             },
         )