Implement MSC4133 to support custom profile fields. (#17488)

Implementation of
[MSC4133](matrix-org/matrix-spec-proposals#4133)
to support custom profile fields. It is behind an experimental flag and
includes tests.


### Pull Request Checklist

<!-- Please read
https://element-hq.github.io/synapse/latest/development/contributing_guide.html
before submitting your pull request -->

* [x] Pull request is based on the develop branch
* [x] Pull request includes a [changelog
file](https://element-hq.github.io/synapse/latest/development/contributing_guide.html#changelog).
The entry should:
- Be a short description of your change which makes sense to users.
"Fixed a bug that prevented receiving messages from other servers."
instead of "Moved X method from `EventStore` to `EventWorkerStore`.".
  - Use markdown where necessary, mostly for `code blocks`.
  - End with either a period (.) or an exclamation mark (!).
  - Start with a capital letter.
- Feel free to credit yourself, by adding a sentence "Contributed by
@github_username." or "Contributed by [Your Name]." to the end of the
entry.
* [x] [Code
style](https://element-hq.github.io/synapse/latest/code_style.html) is
correct
(run the
[linters](https://element-hq.github.io/synapse/latest/development/contributing_guide.html#run-the-linters))

---------

Co-authored-by: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>

changelog.d/17488.feature

@@ -0,0 +1 @@
+Implement [MSC4133](https://github.com/matrix-org/matrix-spec-proposals/pull/4133) for custom profile fields.

synapse/api/errors.py

@@ -132,6 +132,10 @@ class Codes(str, Enum):
     # connection.
     UNKNOWN_POS = "M_UNKNOWN_POS"
 
+    # Part of MSC4133
+    PROFILE_TOO_LARGE = "M_PROFILE_TOO_LARGE"
+    KEY_TOO_LARGE = "M_KEY_TOO_LARGE"
+
 
 class CodeMessageException(RuntimeError):
     """An exception with integer code, a message string attributes and optional headers.

synapse/config/experimental.py

@@ -436,6 +436,9 @@ def read_config(self, config: JsonDict, **kwargs: Any) -> None:
                 ("experimental", "msc4108_delegation_endpoint"),
             )
 
+        # MSC4133: Custom profile fields
+        self.msc4133_enabled: bool = experimental.get("msc4133_enabled", False)
+
         # MSC4210: Remove legacy mentions
         self.msc4210_enabled: bool = experimental.get("msc4210_enabled", False)
 

synapse/handlers/profile.py

@@ -32,7 +32,7 @@
     SynapseError,
 )
 from synapse.storage.databases.main.media_repository import LocalMedia, RemoteMedia
-from synapse.types import JsonDict, Requester, UserID, create_requester
+from synapse.types import JsonDict, JsonValue, Requester, UserID, create_requester
 from synapse.util.caches.descriptors import cached
 from synapse.util.stringutils import parse_and_validate_mxc_uri
 
@@ -43,6 +43,8 @@
 
 MAX_DISPLAYNAME_LEN = 256
 MAX_AVATAR_URL_LEN = 1000
+# Field name length is specced at 255 bytes.
+MAX_CUSTOM_FIELD_LEN = 255
 
 
 class ProfileHandler:
@@ -90,7 +92,15 @@ async def get_profile(self, user_id: str, ignore_backoff: bool = True) -> JsonDi
 
         if self.hs.is_mine(target_user):
             profileinfo = await self.store.get_profileinfo(target_user)
-            if profileinfo.display_name is None and profileinfo.avatar_url is None:
+            extra_fields = {}
+            if self.hs.config.experimental.msc4133_enabled:
+                extra_fields = await self.store.get_profile_fields(target_user)
+
+            if (
+                profileinfo.display_name is None
+                and profileinfo.avatar_url is None
+                and not extra_fields
+            ):
                 raise SynapseError(404, "Profile was not found", Codes.NOT_FOUND)
 
             # Do not include display name or avatar if unset.
@@ -99,6 +109,9 @@ async def get_profile(self, user_id: str, ignore_backoff: bool = True) -> JsonDi
                 ret[ProfileFields.DISPLAYNAME] = profileinfo.display_name
             if profileinfo.avatar_url is not None:
                 ret[ProfileFields.AVATAR_URL] = profileinfo.avatar_url
+            if extra_fields:
+                ret.update(extra_fields)
+
             return ret
         else:
             try:
@@ -403,6 +416,110 @@ async def check_avatar_size_and_mime_type(self, mxc: str) -> bool:
 
         return True
 
+    async def get_profile_field(
+        self, target_user: UserID, field_name: str
+    ) -> JsonValue:
+        """
+        Fetch a user's profile from the database for local users and over federation
+        for remote users.
+
+        Args:
+            target_user: The user ID to fetch the profile for.
+            field_name: The field to fetch the profile for.
+
+        Returns:
+            The value for the profile field or None if the field does not exist.
+        """
+        if self.hs.is_mine(target_user):
+            try:
+                field_value = await self.store.get_profile_field(
+                    target_user, field_name
+                )
+            except StoreError as e:
+                if e.code == 404:
+                    raise SynapseError(404, "Profile was not found", Codes.NOT_FOUND)
+                raise
+
+            return field_value
+        else:
+            try:
+                result = await self.federation.make_query(
+                    destination=target_user.domain,
+                    query_type="profile",
+                    args={"user_id": target_user.to_string(), "field": field_name},
+                    ignore_backoff=True,
+                )
+            except RequestSendFailed as e:
+                raise SynapseError(502, "Failed to fetch profile") from e
+            except HttpResponseException as e:
+                raise e.to_synapse_error()
+
+            return result.get(field_name)
+
+    async def set_profile_field(
+        self,
+        target_user: UserID,
+        requester: Requester,
+        field_name: str,
+        new_value: JsonValue,
+        by_admin: bool = False,
+        deactivation: bool = False,
+    ) -> None:
+        """Set a new profile field for a user.
+
+        Args:
+            target_user: the user whose profile is to be changed.
+            requester: The user attempting to make this change.
+            field_name: The name of the profile field to update.
+            new_value: The new field value for this user.
+            by_admin: Whether this change was made by an administrator.
+            deactivation: Whether this change was made while deactivating the user.
+        """
+        if not self.hs.is_mine(target_user):
+            raise SynapseError(400, "User is not hosted on this homeserver")
+
+        if not by_admin and target_user != requester.user:
+            raise AuthError(403, "Cannot set another user's profile")
+
+        await self.store.set_profile_field(target_user, field_name, new_value)
+
+        # Custom fields do not propagate into the user directory *or* rooms.
+        profile = await self.store.get_profileinfo(target_user)
+        await self._third_party_rules.on_profile_update(
+            target_user.to_string(), profile, by_admin, deactivation
+        )
+
+    async def delete_profile_field(
+        self,
+        target_user: UserID,
+        requester: Requester,
+        field_name: str,
+        by_admin: bool = False,
+        deactivation: bool = False,
+    ) -> None:
+        """Delete a field from a user's profile.
+
+        Args:
+            target_user: the user whose profile is to be changed.
+            requester: The user attempting to make this change.
+            field_name: The name of the profile field to remove.
+            by_admin: Whether this change was made by an administrator.
+            deactivation: Whether this change was made while deactivating the user.
+        """
+        if not self.hs.is_mine(target_user):
+            raise SynapseError(400, "User is not hosted on this homeserver")
+
+        if not by_admin and target_user != requester.user:
+            raise AuthError(400, "Cannot set another user's profile")
+
+        await self.store.delete_profile_field(target_user, field_name)
+
+        # Custom fields do not propagate into the user directory *or* rooms.
+        profile = await self.store.get_profileinfo(target_user)
+        await self._third_party_rules.on_profile_update(
+            target_user.to_string(), profile, by_admin, deactivation
+        )
+
     async def on_profile_query(self, args: JsonDict) -> JsonDict:
         """Handles federation profile query requests."""
 
@@ -419,13 +536,24 @@ async def on_profile_query(self, args: JsonDict) -> JsonDict:
 
         just_field = args.get("field", None)
 
-        response = {}
+        response: JsonDict = {}
         try:
-            if just_field is None or just_field == "displayname":
+            if just_field is None or just_field == ProfileFields.DISPLAYNAME:
                 response["displayname"] = await self.store.get_profile_displayname(user)
 
-            if just_field is None or just_field == "avatar_url":
+            if just_field is None or just_field == ProfileFields.AVATAR_URL:
                 response["avatar_url"] = await self.store.get_profile_avatar_url(user)
+
+            if self.hs.config.experimental.msc4133_enabled:
+                if just_field is None:
+                    response.update(await self.store.get_profile_fields(user))
+                elif just_field not in (
+                    ProfileFields.DISPLAYNAME,
+                    ProfileFields.AVATAR_URL,
+                ):
+                    response[just_field] = await self.store.get_profile_field(
+                        user, just_field
+                    )
         except StoreError as e:
             if e.code == 404:
                 raise SynapseError(404, "Profile was not found", Codes.NOT_FOUND)

synapse/rest/client/capabilities.py

@@ -92,6 +92,23 @@ async def on_GET(self, request: SynapseRequest) -> Tuple[int, JsonDict]:
                 "enabled": self.config.experimental.msc3664_enabled,
             }
 
+        if self.config.experimental.msc4133_enabled:
+            response["capabilities"]["uk.tcpip.msc4133.profile_fields"] = {
+                "enabled": True,
+            }
+
+            # Ensure this is consistent with the legacy m.set_displayname and
+            # m.set_avatar_url.
+            disallowed = []
+            if not self.config.registration.enable_set_displayname:
+                disallowed.append("displayname")
+            if not self.config.registration.enable_set_avatar_url:
+                disallowed.append("avatar_url")
+            if disallowed:
+                response["capabilities"]["uk.tcpip.msc4133.profile_fields"][
+                    "disallowed"
+                ] = disallowed
+
         return HTTPStatus.OK, response