Merge tag 'v1.15.2'

Synapse 1.15.2 (2020-07-02)
===========================

Due to the two security issues highlighted below, server administrators are
encouraged to update Synapse. We are not aware of these vulnerabilities being
exploited in the wild.

Security advisory
-----------------

* A malicious homeserver could force Synapse to reset the state in a room to a
  small subset of the correct state. This affects all Synapse deployments which
  federate with untrusted servers. ([96e9afe6](https://github.com/matrix-org/synapse/commit/96e9afe62500310977dc3cbc99a8d16d3d2fa15c))
* HTML pages served via Synapse were vulnerable to clickjacking attacks. This
  predominantly affects homeservers with single-sign-on enabled, but all server
  administrators are encouraged to upgrade. ([ea26e9a9](https://github.com/matrix-org/synapse/commit/ea26e9a98b0541fc886a1cb826a38352b7599dbe))

  This was reported by [Quentin Gliech](https://sandhose.fr/).

1 files changed, 4 insertions, 9 deletions

diff --git a/synapse/handlers/oidc_handler.py b/synapse/handlers/oidc_handler.py
index 9c08eb5399..87f0c5e197 100644
--- a/synapse/handlers/oidc_handler.py
+++ b/synapse/handlers/oidc_handler.py
@@ -35,7 +35,7 @@ from typing_extensions import TypedDict
 from twisted.web.client import readBody
 
 from synapse.config import ConfigError
-from synapse.http.server import finish_request
+from synapse.http.server import respond_with_html
 from synapse.http.site import SynapseRequest
 from synapse.logging.context import make_deferred_yieldable
 from synapse.push.mailer import load_jinja2_templates
@@ -144,15 +144,10 @@ class OidcHandler:
                 access_denied.
             error_description: A human-readable description of the error.
         """
-        html_bytes = self._error_template.render(
+        html = self._error_template.render(
             error=error, error_description=error_description
-        ).encode("utf-8")
-
-        request.setResponseCode(400)
-        request.setHeader(b"Content-Type", b"text/html; charset=utf-8")
-        request.setHeader(b"Content-Length", b"%i" % len(html_bytes))
-        request.write(html_bytes)
-        finish_request(request)
+        )
+        respond_with_html(request, 400, html)
 
     def _validate_metadata(self):
         """Verifies the provider metadata.