Use custom stage UIA error for MAS cross-signing reset (#17509)

Rather than 501 M_UNRECOGNISED

Client side implementation at
https://github.com/matrix-org/matrix-react-sdk/pull/12892/

1 files changed, 12 insertions, 1 deletions

diff --git a/synapse/rest/client/auth.py b/synapse/rest/client/auth.py

index 4221f35937..32eeecd662 100644
--- a/synapse/rest/client/auth.py
+++ b/synapse/rest/client/auth.py
@@ -27,7 +27,7 @@ from twisted.web.server import Request
 from synapse.api.constants import LoginType
 from synapse.api.errors import LoginError, SynapseError
 from synapse.api.urls import CLIENT_API_PREFIX
-from synapse.http.server import HttpServer, respond_with_html
+from synapse.http.server import HttpServer, respond_with_html, respond_with_redirect
 from synapse.http.servlet import RestServlet, parse_string
 from synapse.http.site import SynapseRequest
 
@@ -66,6 +66,17 @@ class AuthRestServlet(RestServlet):
         if not session:
             raise SynapseError(400, "No session supplied")
 
+        if (
+            self.hs.config.experimental.msc3861.enabled
+            and stagetype == "org.matrix.cross_signing_reset"
+        ):
+            config = self.hs.config.experimental.msc3861
+            if config.account_management_url is not None:
+                url = f"{config.account_management_url}?action=org.matrix.cross_signing_reset"
+            else:
+                url = config.issuer
+            respond_with_redirect(request, str.encode(url))
+
         if stagetype == LoginType.RECAPTCHA:
             html = self.recaptcha_template.render(
                 session=session,