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