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56 lines
1.8 KiB
56 lines
1.8 KiB
12 years ago
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Request Content Checksums
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=========================
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Various pieces of code can consume the request data and preprocess it.
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For instance JSON data ends up on the request object already read and
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processed, form data ends up there as well but goes through a different
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code path. This seems inconvenient when you want to calculate the
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checksum of the incoming request data. This is necessary sometimes for
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some APIs.
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Fortunately this is however very simple to change by wrapping the input
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stream.
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The following example calculates the SHA1 checksum of the incoming data as
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it gets read and stores it in the WSGI environment::
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import hashlib
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class ChecksumCalcStream(object):
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def __init__(self, stream):
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self._stream = stream
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self._hash = hashlib.sha1()
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def read(self, bytes):
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rv = self._stream.read(bytes)
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self._hash.update(rv)
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return rv
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def readline(self, size_hint):
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rv = self._stream.readline(size_hint)
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self._hash.update(rv)
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return rv
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def generate_checksum(request):
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env = request.environ
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stream = ChecksumCalcStream(env['wsgi.input'])
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env['wsgi.input'] = stream
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return stream._hash
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To use this, all you need to do is to hook the calculating stream in
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before the request starts consuming data. (Eg: be careful accessing
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``request.form`` or anything of that nature. ``before_request_handlers``
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for instance should be careful not to access it).
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Example usage::
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@app.route('/special-api', methods=['POST'])
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def special_api():
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hash = generate_checksum(request)
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# Accessing this parses the input stream
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files = request.files
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# At this point the hash is fully constructed.
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checksum = hash.hexdigest()
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return 'Hash was: %s' % checksum
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