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Date: Tue, 1 Dec 2020 10:35:22 -0800
Message-ID: <CAN2symii22mQknY=Y=zxJDF+EdZ0XcBBc8FsFTyEYR=PTY6k_g@mail.gmail.com>
To: "G. P. B." <george.banyard@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: paul.crovella@gmail.com (Paul Crovella)

On Tue, Dec 1, 2020 at 10:23 AM G. P. B. <george.banyard@gmail.com> wrote:
>
> 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
>> To unsubscribe, visit: https://www.php.net/unsub.php
>
>
> 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.

That's correct, it shouldn't have.

> Would it have been fine if this would have been a TypeError as it was
> originally intended?

No, I imagine it would've been fixed sooner.

> Is a warning fine because null bytes indicate a potential attack as in no sane
> context should null bytes be passed around?

Null bytes come from many places and do not necessarily indicate an
"attack." There's plenty of UTF-16 in the world, for example, that's
got oodles of them.

> 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

Because it didn't break userland code for 8 years. A ValueError is a
much louder thing - that's the whole point of it in fact. It shouldn't
be a surprise that it comes up now.