3 files changed, 23 insertions, 2 deletions
diff --git a/synapse/http/server.py b/synapse/http/server.py
index e3dcc3f3dd..cf2d6f904b 100644
--- a/synapse/http/server.py
+++ b/synapse/http/server.py
@@ -928,6 +928,17 @@ def set_cors_headers(request: Request) -> None:
     )
 
 
+def set_corp_headers(request: Request) -> None:
+    """Set the CORP headers so that javascript running in a web browsers can
+    embed the resource returned from this request when their client requires
+    the `Cross-Origin-Embedder-Policy: require-corp` header.
+
+    Args:
+        request: The http request to add the CORP header to.
+    """
+    request.setHeader(b"Cross-Origin-Resource-Policy", b"cross-origin")
+
+
 def respond_with_html(request: Request, code: int, html: str) -> None:
     """
     Wraps `respond_with_html_bytes` by first encoding HTML from a str to UTF-8 bytes.
diff --git a/synapse/rest/media/v1/download_resource.py b/synapse/rest/media/v1/download_resource.py
index 6180fa575e..048a042692 100644
--- a/synapse/rest/media/v1/download_resource.py
+++ b/synapse/rest/media/v1/download_resource.py
@@ -15,7 +15,11 @@
 import logging
 from typing import TYPE_CHECKING
 
-from synapse.http.server import DirectServeJsonResource, set_cors_headers
+from synapse.http.server import (
+    DirectServeJsonResource,
+    set_corp_headers,
+    set_cors_headers,
+)
 from synapse.http.servlet import parse_boolean
 from synapse.http.site import SynapseRequest
 
@@ -38,6 +42,7 @@ class DownloadResource(DirectServeJsonResource):
 
     async def _async_render_GET(self, request: SynapseRequest) -> None:
         set_cors_headers(request)
+        set_corp_headers(request)
         request.setHeader(
             b"Content-Security-Policy",
             b"sandbox;"
diff --git a/synapse/rest/media/v1/thumbnail_resource.py b/synapse/rest/media/v1/thumbnail_resource.py
index 53b1565243..2295adfaa7 100644
--- a/synapse/rest/media/v1/thumbnail_resource.py
+++ b/synapse/rest/media/v1/thumbnail_resource.py
@@ -18,7 +18,11 @@ import logging
 from typing import TYPE_CHECKING, Any, Dict, List, Optional, Tuple
 
 from synapse.api.errors import SynapseError
-from synapse.http.server import DirectServeJsonResource, set_cors_headers
+from synapse.http.server import (
+    DirectServeJsonResource,
+    set_corp_headers,
+    set_cors_headers,
+)
 from synapse.http.servlet import parse_integer, parse_string
 from synapse.http.site import SynapseRequest
 from synapse.rest.media.v1.media_storage import MediaStorage
@@ -58,6 +62,7 @@ class ThumbnailResource(DirectServeJsonResource):
 
     async def _async_render_GET(self, request: SynapseRequest) -> None:
         set_cors_headers(request)
+        set_corp_headers(request)
         server_name, media_id, _ = parse_media_id(request)
         width = parse_integer(request, "width", required=True)
         height = parse_integer(request, "height", required=True)