Nadav Har'El 653f2df28f alternator: fix JSON escaping of error responses ...

In the DynamoDB API, error responses are in JSON format with specific
fields ("__type" and "message" in the x-amz-json-1.0 format currently
used). Alternator tried to be clever and build the string representation
of this JSON itself, instead of using RapidJSON. But this optimization
was a mistake - if the error message contains characters that need
escaping (such as double quotes and newlines), they weren't escaped,
and the resulting JSON was malformed. When the client library boto3
read this malformed JSON it got confused, cosidered the entire error
response to be a string, which resulted in an ugly error message.

The fix is easy - just build the JSON output as usual with RapidJSON
instead of trying to optimize using string operation.

The patch also includes two tests reproducing this bug and checking its
fix. The first test uses boto3 and shows it got confused on the type
of error (not understanding that it is a ValidationException). The
second test bypasses boto3 and shows exactly where the bug happens -
the response is an unparsable JSON.

Fixes #10278

Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20220327132705.3707979-1-nyh@scylladb.com>

2022-03-27 16:32:36 +03:00

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