Support MSC3916 by adding `_matrix/client/v1/media/download` endpoint (#17365)

3 files changed, 76 insertions, 8 deletions

diff --git a/synapse/rest/__init__.py b/synapse/rest/__init__.py
index 0024ccf708..c94d454a28 100644
--- a/synapse/rest/__init__.py
+++ b/synapse/rest/__init__.py
@@ -145,6 +145,10 @@ class ClientRestResource(JsonResource):
         password_policy.register_servlets(hs, client_resource)
         knock.register_servlets(hs, client_resource)
         appservice_ping.register_servlets(hs, client_resource)
+        if hs.config.server.enable_media_repo:
+            from synapse.rest.client import media
+
+            media.register_servlets(hs, client_resource)
 
         # moving to /_synapse/admin
         if is_main_process:
diff --git a/synapse/rest/client/media.py b/synapse/rest/client/media.py
index 0c089163c1..c0ae5dd66f 100644
--- a/synapse/rest/client/media.py
+++ b/synapse/rest/client/media.py
@@ -22,6 +22,7 @@
 
 import logging
 import re
+from typing import Optional
 
 from synapse.http.server import (
     HttpServer,
@@ -194,14 +195,76 @@ class UnstableThumbnailResource(RestServlet):
             self.media_repo.mark_recently_accessed(server_name, media_id)
 
 
+class DownloadResource(RestServlet):
+    PATTERNS = [
+        re.compile(
+            "/_matrix/client/v1/media/download/(?P<server_name>[^/]*)/(?P<media_id>[^/]*)(/(?P<file_name>[^/]*))?$"
+        )
+    ]
+
+    def __init__(self, hs: "HomeServer", media_repo: "MediaRepository"):
+        super().__init__()
+        self.media_repo = media_repo
+        self._is_mine_server_name = hs.is_mine_server_name
+        self.auth = hs.get_auth()
+
+    async def on_GET(
+        self,
+        request: SynapseRequest,
+        server_name: str,
+        media_id: str,
+        file_name: Optional[str] = None,
+    ) -> None:
+        # Validate the server name, raising if invalid
+        parse_and_validate_server_name(server_name)
+
+        await self.auth.get_user_by_req(request)
+
+        set_cors_headers(request)
+        set_corp_headers(request)
+        request.setHeader(
+            b"Content-Security-Policy",
+            b"sandbox;"
+            b" default-src 'none';"
+            b" script-src 'none';"
+            b" plugin-types application/pdf;"
+            b" style-src 'unsafe-inline';"
+            b" media-src 'self';"
+            b" object-src 'self';",
+        )
+        # Limited non-standard form of CSP for IE11
+        request.setHeader(b"X-Content-Security-Policy", b"sandbox;")
+        request.setHeader(b"Referrer-Policy", b"no-referrer")
+        max_timeout_ms = parse_integer(
+            request, "timeout_ms", default=DEFAULT_MAX_TIMEOUT_MS
+        )
+        max_timeout_ms = min(max_timeout_ms, MAXIMUM_ALLOWED_MAX_TIMEOUT_MS)
+
+        if self._is_mine_server_name(server_name):
+            await self.media_repo.get_local_media(
+                request, media_id, file_name, max_timeout_ms
+            )
+        else:
+            ip_address = request.getClientAddress().host
+            await self.media_repo.get_remote_media(
+                request,
+                server_name,
+                media_id,
+                file_name,
+                max_timeout_ms,
+                ip_address,
+                True,
+            )
+
+
 def register_servlets(hs: "HomeServer", http_server: HttpServer) -> None:
-    if hs.config.experimental.msc3916_authenticated_media_enabled:
-        media_repo = hs.get_media_repository()
-        if hs.config.media.url_preview_enabled:
-            UnstablePreviewURLServlet(
-                hs, media_repo, media_repo.media_storage
-            ).register(http_server)
-        UnstableMediaConfigResource(hs).register(http_server)
-        UnstableThumbnailResource(hs, media_repo, media_repo.media_storage).register(
+    media_repo = hs.get_media_repository()
+    if hs.config.media.url_preview_enabled:
+        UnstablePreviewURLServlet(hs, media_repo, media_repo.media_storage).register(
             http_server
         )
+    UnstableMediaConfigResource(hs).register(http_server)
+    UnstableThumbnailResource(hs, media_repo, media_repo.media_storage).register(
+        http_server
+    )
+    DownloadResource(hs, media_repo).register(http_server)
diff --git a/synapse/rest/media/download_resource.py b/synapse/rest/media/download_resource.py
index 1628d58926..c32c626905 100644
--- a/synapse/rest/media/download_resource.py
+++ b/synapse/rest/media/download_resource.py
@@ -105,4 +105,5 @@ class DownloadResource(RestServlet):
                 file_name,
                 max_timeout_ms,
                 ip_address,
+                False,
             )