Fix host header port mismatch in signing #578
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jonathan343
reviewed
Oct 17, 2025
| ) | ||
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| signing_fields = self._normalize_signing_fields(request=new_request) | ||
| # If any headers have been added, make sure those are reflected in the new request |
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Is there a reason we can't apply this in the _apply_required_fields method where we set X-Amz-Date and X-Amz-Security-Token? Just seeing that now
jonathan343
reviewed
Oct 17, 2025
| if "host" not in request.fields: | ||
| request.fields.set_field( | ||
| Field(name="host", values=[request.destination.host]) | ||
| Field(name="host", values=[request.destination.netloc]) |
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We should look into if netloc is the right choice. It would follow the format of {username}:{password}@{host}:{port}.
I see ruby does {host}:{port} (src)
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This PR includes a bugfix which breaks signing any requests that are sent to a non-default port.
Problem:
There's a mismatch between the host header used for signing vs. the actual request header when connecting to non-default ports.
• During signing: The host header includes port (from URI netloc) and gets added to signed headers. The header does not get added to the final request.
• During request creation: The host header excludes port (from URI host) if not already present.
• Result: The request is signed with
example.com:8080but sent with the host header having a value ofexample.com. This creates a signature validation issue server-side.Solution:
This PR fixes the issue in two places:
This ensures the host header value is consistent between signing and transmission for non-default ports.
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