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Date: Tue, 1 Dec 2020 18:23:34 +0000
Message-ID: <CAFPFaMLEdq0+hYkE49YVbcFvCt00rne6roApcoyY4aK=1ZHpuA@mail.gmail.com>
To: Paul Crovella <paul.crovella@gmail.com>
Cc: "Christoph M. Becker" <cmbecker69@gmx.de>, "Aimeos | Norbert Sendetzky" <norbert@aimeos.com>, 
	PHP internals <internals@lists.php.net>
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Subject: Re: [PHP-DEV] Re: PHP 8 is_file/is_dir input handling
From: george.banyard@gmail.com ("G. P. B.")

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On Tue, 1 Dec 2020 at 18:07, Paul Crovella <paul.crovella@gmail.com> wrote:

> On Tue, Dec 1, 2020 at 9:43 AM Christoph M. Becker <cmbecker69@gmx.de>
> wrote:
> >
> > On 01.12.2020 at 18:35, Aimeos | Norbert Sendetzky wrote:
> >
> > > Am 01.12.20 um 18:24 schrieb Christoph M. Becker:
> > >>
> > >>> In PHP 7, this returns FALSE:
> > >>>
> > >>> php -r 'var_dump(is_file("ab\0c"));'
> > >>>
> > >>> In PHP 8, the same code throws a ValueException. Problem is now that
> > >>> it's not possible to check upfront if the passed argument is a valid
> > >>> path to avoid the exception being thrown.
> > >>
> > >> This is only about the NUL byte in the filename.  You can easily check
> > >> for that yourself. :)
> > >
> > > There may be other checks that will throw a ValueException. I'm not
> sure
> > > how it's implemented in detail because the filestat.c file doesn't
> > > thrown an exception at all:
> >
> > The exception is thrown from inside the parameter parsing routines
> > (zend_parse_parameters() and friends).  Internal function differenciate
> > between string and path, whereas the latter is an arbitrary string which
> > does not contain NUL bytes.
> >
> > It would likely make sense to document that.  OTOH, it's probably a good
> > idea to check (almost) all user input for NUL bytes.
>
> Would it not make more sense for something like is_file to have
> obvious sane behavior and simply return false itself? I don't
> understand the resistance to making it more difficult for a developer
> to screw something up.
>
> --
> PHP Internals - PHP Runtime Development Mailing List
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So why having is_file()/is_dir() throw a warning for the past 8 years
(since PHP 5.4) a non-issue? Because by that logic it shouldn't
have been emitting warnings either.
Would it have been fine if this would have been a TypeError as it was
originally intended?
Is a warning fine because null bytes indicate a potential attack as in no
sane
context should null bytes be passed around?

I don't personally *care* that it throws a ValueError, but why is this
issue only
brought up *now* when it should have been shouting for 8 years and is
either an
indication of a bug or of something larger at play.

Best regards,

George P. Banyard

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