req.read() with no arguments doesn't return all data where input filter inserts
extra data in input stream.
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Key: MODPYTHON-212
URL: https://issues.apache.org/jira/browse/MODPYTHON-212
Project: mod_python
Issue Type: Bug
Components: core
Affects Versions: 3.2.10, 3.3
Reporter: Graham Dumpleton
The req.read() function when supplied with no arguments is supposed to return
all available data from the request body input stream. To do this it uses
req.remaining as the amount of data still to be read and will only read up to
that amount of data.
The problem with this is that req.remaining is originally set to be the value
of the Content-Length header of the request. This however may not actually be
how much data there is to read as input filters may actually remove or add data
to the input stream. This will not cause a problem when an input filter removes
data as the amount it thinks there is to read will still be more than what is
actually available after the input filter has removed data.
In the case of an input filter that inserts additional data, the amount of data
to be read will actually exceed the value of req.remaining and as a consequence
req.read() will not return all the available data. Even subsequent calls to
req.read() with no arguments will not return all the data as req.remaining by
then is zero and it will think it has read all the available data.
The only way to get all the data is to make successive calls to req.read() but
supply some size as argument. Calls should be made to req.read() with the
argument until req.read() returns an empty string. Only when it returns an
empty string are you sure all data has been returned.
This problem will also affect req.readline() as it uses req.remaining in a
similar way. The req.readlines() function is also possibly indirectly affected
as it calls req.readline() to read individual lines and so it may not be able
to access any additional lines beyond the original content length specified in
the request.
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