Submitting a S3 CopyObject to replace user metadata with Content-Length 0 causes Error 500 after the checksum workaround

[jeking3]

Example request:

[DEBUG] 2025-02-13 20:48:40.015 CURL [140340847924992] (HeaderOut) PUT /s3testbucket/dst/testfile HTTP/1.1
Host: 127.0.0.1:12509
Accept: */*
amz-sdk-invocation-id: 008050B0-3919-4A52-AA41-5E93710D4049
amz-sdk-request: ttl=20250213T205140Z; attempt=4
authorization: ...
content-encoding: aws-chunked
content-length: 0
content-type: binary/octet-stream
user-agent: aws-sdk-cpp/1.11.500 md/internal ua/2.1 api/S3 os/Linux#5.10.233-204.894.x86_64 lang/c++#C++11 md/aws-crt#0.30.1 md/arch#x86_64 md/GCC#7.3.1 m/Z,b
x-amz-api-version: 2006-03-01
x-amz-content-sha256: e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855
x-amz-copy-source: s3testbucket/dst/testfile
x-amz-copy-source-if-match: "620f0b67a91f7f74151bc5be745b7110"
x-amz-date: 20250213T204840Z
x-amz-meta-last-modified: 1739479675000
x-amz-meta-usermetakey: usermetaval
x-amz-metadata-directive: REPLACE
x-amz-security-token: ...

Example 500 stack:

Error on request:
Traceback (most recent call last):
  File "/test-runtime/lib/python3.9/site-packages/werkzeug/serving.py", line 370, in run_wsgi
    execute(self.server.app)
  File "/test-runtime/lib/python3.9/site-packages/werkzeug/serving.py", line 331, in execute
    application_iter = app(environ, start_response)
  File "/test-runtime/lib/python3.9/site-packages/moto/moto_server/werkzeug_app.py", line 264, in __call__
    return backend_app(environ, start_response)
  File "/test-runtime/lib/python3.9/site-packages/flask/app.py", line 1478, in __call__
    return self.wsgi_app(environ, start_response)
  File "/test-runtime/lib/python3.9/site-packages/flask/app.py", line 1458, in wsgi_app
    response = self.handle_exception(e)
  File "/test-runtime/lib/python3.9/site-packages/flask_cors/extension.py", line 176, in wrapped_function
    return cors_after_request(app.make_response(f(*args, **kwargs)))
  File "/test-runtime/lib/python3.9/site-packages/flask/app.py", line 1455, in wsgi_app
    response = self.full_dispatch_request()
  File "/test-runtime/lib/python3.9/site-packages/flask/app.py", line 869, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/test-runtime/lib/python3.9/site-packages/flask_cors/extension.py", line 176, in wrapped_function
    return cors_after_request(app.make_response(f(*args, **kwargs)))
  File "/test-runtime/lib/python3.9/site-packages/flask/app.py", line 867, in full_dispatch_request
    rv = self.dispatch_request()
  File "/test-runtime/lib/python3.9/site-packages/flask/app.py", line 852, in dispatch_request
    return self.ensure_sync(self.view_functions[rule.endpoint])(**view_args)
  File "/test-runtime/lib/python3.9/site-packages/moto/core/utils.py", line 112, in __call__
    result = self.callback(request, request.url, dict(request.headers))
  File "/test-runtime/lib/python3.9/site-packages/moto/core/responses.py", line 307, in _inner
    response = getattr(cls(), to_call.__name__)(request, full_url, headers)
  File "/test-runtime/lib/python3.9/site-packages/moto/s3/responses.py", line 1377, in key_response
    self.setup_class(request, full_url, headers)
  File "/test-runtime/lib/python3.9/site-packages/moto/s3/responses.py", line 191, in setup_class
    self.body = request.input_stream.getvalue()
AttributeError: '_io.BufferedReader' object has no attribute 'getvalue'

Code in question:

moto/moto/s3/responses.py

Line 191 in c2a0d9c

self.body = request.input_stream.getvalue()

I'm not sure where the BufferedReader comes from; it does not appear to be from moto.

[bpandola]

I put a comment in #8596 with some thoughts on this. Something that would also be helpful, if you're up for it, would be to stand up a minimal failing test case using the AWS SDK for C++. You can look in the other_langs directory in moto for some examples using other AWS SDKs.