Assignment to req.filename and POSIX style pathnames.
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Key: MODPYTHON-171
URL: http://issues.apache.org/jira/browse/MODPYTHON-171
Project: mod_python
Type: Bug
Components: core
Versions: 3.2.8
Reporter: Graham Dumpleton
In Apache, all the path names relating to the matched target of a request are
dealt with as POSIX style paths. That is, a forward slash is used as the
directory separator even if the platform is Win32. The only real allowance for
Win32 stuff is that drive specifiers may still occur in which case the drive
letter is always converted to upper case.
All the Apache C API functions dealing with manipulation of and specifically
generation of modified paths will by default ensure that paths are maintained
in this POSIX style. To have a path be generated in its true native form, you
need to provide special flags to functions.
When an Apache module writer works with paths, they would normally rely on the
default behaviour and so long as they use the functions provided by the Apache
C API, the result will always be consistent.
Where would all this be a potential issue is where modules set the
request_rec->filename attribute, ie., the req.filename attribute of the
mod_python request object. In a C Apache module, as the result is always going
to be in the correct form when request_rec->filename is modified, everything
still comes out okay.
The problem in mod_python, or more perhaps when using Python, is that all the
directory manipulation routines in os.path as they exist on Win32 platform can
generate paths with back slashes in them. Further, it is often convenient to
use __file__ attribute of modules in some way, which again is going to use back
slashes on Win32 platform. If the results from either of these is assigned to
req.filename, the result request_rec->filename attribute is no longer going to
be in the POSIX style form which is would normally exist if only the Apache C
APIs were used.
One area where this causes a problem (and which isn't fixed) was described in
MODPYTHON-161, whereby setting req.filename to a path which includes back
slashes instead of the required POSIX style forward slashes can result in the
wrong interpreter being selected for a subsequent phase if the
PythonInterpPerDirectory directive is being used. The case used for any drive
specifier could similarly be a problem.
Now although Python provides os.path.normpath(), that normalises a path in the
native format. There is no function which can normalise a path and output it in
the POSIX style format. Trying to create a function in Python which does may
not yield the same result as what Apache expects.
The actual function in Apache which can be used to normalise paths and which
outputs the POSIX style path required is apr_filepath_merge(). The question is,
should this be exposed in some way so that it is useable from mod_python, or
for the req.filename case, should assignment to req.filename automatically
trigger normalisation of the path to ensure that it simply just works all the
time and isn't dependent on a user of mod_python realising they need to
normalise it first in the POSIX style to ensure their code is portable across
platforms.
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