Use `max_upload_size` as the limit when following the `Location` header (#17543)

Otherwise we use the `expected_size` from the initial federation
request, which might be far too low.

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---------

Co-authored-by: Erik Johnston <erikj@element.io>

1 files changed, 5 insertions, 1 deletions

diff --git a/synapse/http/matrixfederationclient.py b/synapse/http/matrixfederationclient.py

index 6fd75fd381..12c41c39e9 100644
--- a/synapse/http/matrixfederationclient.py
+++ b/synapse/http/matrixfederationclient.py
@@ -464,6 +464,8 @@ class MatrixFederationHttpClient:
         self.max_long_retries = hs.config.federation.max_long_retries
         self.max_short_retries = hs.config.federation.max_short_retries
 
+        self.max_download_size = hs.config.media.max_upload_size
+
         self._cooperator = Cooperator(scheduler=_make_scheduler(self.reactor))
 
         self._sleeper = AwakenableSleeper(self.reactor)
@@ -1756,8 +1758,10 @@ class MatrixFederationHttpClient:
                 request.destination,
                 str_url,
             )
+            # We don't know how large the response will be upfront, so limit it to
+            # the `max_upload_size` config value.
             length, headers, _, _ = await self._simple_http_client.get_file(
-                str_url, output_stream, expected_size
+                str_url, output_stream, self.max_download_size
             )
 
         logger.info(