Failover on proper error responses. (#14620)
When querying a remote server handle a 404/405 with an
errcode of M_UNRECOGNIZED as an unimplemented endpoint.
2 files changed, 21 insertions, 9 deletions
diff --git a/changelog.d/14620.bugfix b/changelog.d/14620.bugfix
new file mode 100644
index 0000000000..cb95a87d92
--- /dev/null
+++ b/changelog.d/14620.bugfix
@@ -0,0 +1 @@
+Return spec-compliant JSON errors when unknown endpoints are requested.
diff --git a/synapse/federation/federation_client.py b/synapse/federation/federation_client.py
index 8bccc9c60d..137cfb3346 100644
--- a/synapse/federation/federation_client.py
+++ b/synapse/federation/federation_client.py
@@ -771,17 +771,28 @@ class FederationClient(FederationBase):
"""
if synapse_error is None:
synapse_error = e.to_synapse_error()
- # There is no good way to detect an "unknown" endpoint.
+ # MSC3743 specifies that servers should return a 404 or 405 with an errcode
+ # of M_UNRECOGNIZED when they receive a request to an unknown endpoint or
+ # to an unknown method, respectively.
#
- # Dendrite returns a 404 (with a body of "404 page not found");
- # Conduit returns a 404 (with no body); and Synapse returns a 400
- # with M_UNRECOGNIZED.
- #
- # This needs to be rather specific as some endpoints truly do return 404
- # errors.
+ # Older versions of servers don't properly handle this. This needs to be
+ # rather specific as some endpoints truly do return 404 errors.
return (
- e.code == 404 and (not e.response or e.response == b"404 page not found")
- ) or (e.code == 400 and synapse_error.errcode == Codes.UNRECOGNIZED)
+ # 404 is an unknown endpoint, 405 is a known endpoint, but unknown method.
+ (e.code == 404 or e.code == 405)
+ and (
+ # Older Dendrites returned a text or empty body.
+ # Older Conduit returned an empty body.
+ not e.response
+ or e.response == b"404 page not found"
+ # The proper response JSON with M_UNRECOGNIZED errcode.
+ or synapse_error.errcode == Codes.UNRECOGNIZED
+ )
+ ) or (
+ # Older Synapses returned a 400 error.
+ e.code == 400
+ and synapse_error.errcode == Codes.UNRECOGNIZED
+ )
async def _try_destination_list(
self,
|
