Re: [PATCH] python/sepolicy: call segenxml.py with python3

[Nicolas Iooss <nicolas.iooss@m4x.org>]

On Mon, Oct 7, 2019 at 3:23 PM Stephen Smalley <sds@tycho.nsa.gov> wrote:
>
> On 9/30/19 3:36 PM, Nicolas Iooss wrote:
> > On Mon, Sep 30, 2019 at 6:29 PM Petr Lautrbach <plautrba@redhat.com> wrote:
> >>
> >> Stephen Smalley <sds@tycho.nsa.gov> writes:
> >>
> >>> On 9/26/19 5:58 PM, Nicolas Iooss wrote:
> >>>> On Thu, Sep 26, 2019 at 2:52 PM Stephen Smalley <sds@tycho.nsa.gov> wrote:
> >>>>>
> >>>>> Fixes: https://github.com/SELinuxProject/selinux/issues/61
> >>>>> Signed-off-by: Stephen Smalley <sds@tycho.nsa.gov>
> >>>>> ---
> >>>>>    python/sepolicy/sepolicy/interface.py | 2 +-
> >>>>>    1 file changed, 1 insertion(+), 1 deletion(-)
> >>>>>
> >>>>> diff --git a/python/sepolicy/sepolicy/interface.py b/python/sepolicy/sepolicy/interface.py
> >>>>> index 583091ae18aa..b1b39a492d73 100644
> >>>>> --- a/python/sepolicy/sepolicy/interface.py
> >>>>> +++ b/python/sepolicy/sepolicy/interface.py
> >>>>> @@ -196,7 +196,7 @@ def get_xml_file(if_file):
> >>>>>            from subprocess import getstatusoutput
> >>>>>        basedir = os.path.dirname(if_file) + "/"
> >>>>>        filename = os.path.basename(if_file).split(".")[0]
> >>>>> -    rc, output = getstatusoutput("python /usr/share/selinux/devel/include/support/segenxml.py -w -m %s" % basedir + filename)
> >>>>> +    rc, output = getstatusoutput("/usr/bin/python3 /usr/share/selinux/devel/include/support/segenxml.py -w -m %s" % basedir + filename)
> >>>>>        if rc != 0:
> >>>>>            sys.stderr.write("\n Could not proceed selected interface file.\n")
> >>>>>            sys.stderr.write("\n%s" % output)
> >>>>
> >>>> Considering that Python's "command" module was removed in Python 3
> >>>> (according to https://docs.python.org/2/library/commands.html), and
> >>>> that Python 3's subprocess.getstatusoutput() supports using a list of
> >>>> arguments instead of a string, it seems better to change this code to
> >>>> something like:
> >>
> >> I think this is not correct:
> >>
> >>      Execute the string 'cmd' in a shell with 'check_output' and
> >>      return a 2-tuple (status, output). The locale encoding is used
> >>      to decode the output and process newlines.
> >>
> >>
> >>>>> subprocess.getstatusoutput(["echo", "hey"])
> >> (0, '')
> >>
> >>>> subprocess.getstatusoutput("echo hey")
> >> (0, 'hey')
> >
> > Indeed, I am so used to subprocess.check_output() and
> > subprocess.Popen(), that can both take arguments as a list, that I
> > expected it to be the same with subprocess.getstatusoutput(), but it
> > is not correct. Sorry for the confusion, and thank you for fixing it!
> >
> > Anyway, using getstatusoutput() by concatenating a path to a command
> > line makes get_xml_file() broken when operating on paths with spaces,
> > as the paths are not quoted nor escaped before they are concatenated.
> > In my humble opinion, I would prefer if the code was written in a more
> > "defensive" way. But because nobody seems to have complained about
> > this so far and because Python's standard library does not help much,
> > I accept keeping getstatusoutput() for now.
> >
> >>>>
> >>>>       from subprocess import getstatusoutput
> >>>>       basedir = os.path.dirname(if_file)
> >>>>       filename = os.path.basename(if_file).split(".")[0]
> >>>>       rc, output = getstatusoutput(["python3",
> >>>> "/usr/share/selinux/devel/include/support/segenxml.py", "-w", "-m",
> >>>> os.path.join(basedir, filename)])
> >>>>
> >>>> The code that I suggest is not compatible with Python 2 (which does
> >>>> not support using list of arguments). Therefore, doing so makes
> >>>> sepolicy really Python-3 only. I do not consider this to be an issue,
> >>>> but others may prefer to wait for 3.0 to be released before dropping
> >>>> support for Python 2 completely.
> >>>
> >>> Anyone else have an opinion on whether we should fix this in a
> >>> python2-compatible manner?
> >>
> >> I'd stay with python2 compatible for now.
> >>
> >>> Also, should it be just "python3" or "/usr/bin/python3"?
> >>
> >> It would be great if it could use $(PYTHON) from Makefile.
> >
> > I agree, but this would be quite complex (the implementations of this
> > idea that I imagine would consists in editing the Python source code
> > with "sed" commands when installing the file). But it would
> > nonetheless be nice if
> > "/usr/share/selinux/devel/include/support/segenxml.py" could also be
> > configured in Makefile...
> > Anyway, for "python3 vs. /usr/bin/python3", I would like to stick as
> > closely as possible with the meaning: use "/usr/bin/..." for
> > system-wide programs/files and use "/usr/bin/env" or "python" for
> > programs that can be run in Python's virtual environments. As
> > /usr/share/selinux/devel/include/support/segenxml.py falls into
> > category "system-wide files", my choice would be for /usr/bin/python3.
>
> So, are people ok with merging the patch as posted in order to fix the
> open issue before the next release?

Yes, even though it would be nicer if the parameters were surrounded
by parentheses: rc, output = getstatusoutput("/usr/bin/python3
/usr/share/selinux/devel/include/support/segenxml.py -w -m %s" %
(basedir + filename))

Acked-by: Nicolas Iooss <nicolas.iooss@m4x.org>

Nicolas