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Cc: PHPdev <internals@lists.php.net>
Date: Tue, 27 Sep 2011 09:04:16 +0200
To: Christian Stocker <christian.stocker@liip.ch>
Subject: Re: [PHP-DEV] Question about ABI compatibility for an ext/xsl patch and an API question for the implementation
From: rasmus@lerdorf.com (Rasmus Lerdorf)

This sounds like the best approach actually.

On Sep 27, 2011, at 7:03 AM, Christian Stocker <christian.stocker@liip.ch> w=
rote:

> Hi again
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> I just had the idea for a 4th option. Won't be less controversy, but
> it's backwards and forwards compatible.
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> 4) use a php ini setting in PHP 5.3
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> I know, we try to avoid that as much as possible. BUT
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> * It will only be in 5.3, not even committed to 5.4
> * If you don't have the ini setting, your XSLT can't write files, the
> error will be pretty obvious. If you just read and transform, nothing
> will or has to change
> * Only a very very very small fraction will need to set this ini setting
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> The code for enable writing again, which would work in 5.0 - 5.4+ looks
> like this. With my first proposal, I'd need much more if/else to make my
> code work on 5.3.8-/5.3.9+/5.4+
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> ***
> $xsl =3D new XSLTProcessor();
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> //if you want to write from within the XSLT
> $oldvalini =3D ini_set("xsl_security_prefs",XSL_SECPREFS_NONE);
> if (version_compare(PHP_VERSION,'5.4',">=3D")) {
>    $oldval =3D $xsl->setSecurityPreferences(XSL_SECPREFS_NONE);
> }
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> $xsl->transformToXml(...);
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> //go back to the old setting. Better safe than sorry
> ini_set("xsl_security_prefs",$oldvalini);
> if (version_compare(PHP_VERSION,'5.4',">=3D")) {
>     $xsl->setSecurityPreferences($oldval);
> }
> ***
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> chregu
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>=20
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> On 26.09.11 19:59, Christian Stocker wrote:
>> Hi
>>=20
>> Some weeks ago I wrote a patch to disable writing from within XSLT
>> templates. That patch is now in 5.4 but wasn't accepted in PHP 5.3 since
>> it changed a struct in the header file.
>>=20
>> I have now I new patch which doesn't need that changing in the struct,
>> but I need a new .h file from libxslt.
>>=20
>> https://gist.github.com/3d3d3c3418236f748118 (unfinished patch, just a
>> proof of concept, but the basics are there)
>>=20
>> Can anybody tell me, if that still breaks binary compatibility for
>> extensions or if that would be ok?
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>> Then a more general question:
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>> There are now 2 ways to enable write access again (in 5.4). Via an
>> additional optional parameter to the transform methods (this works with
>> the patch above in 5.3 also) or via the new 5.4 only method
>> ->setSecurityPrefs(). The former is from a clean API point of view not
>> nice, adding more and more optional parameters to methods is the ticket
>> to hell usually. But I can't come up with a better solution for 5.3
>> without breaking the ABI. And since it's somehow a security issue, I
>> would sleep better a lot, if we have a proper patch for 5.3 as well.
>>=20
>> To keep BC, I can't just delete the optional parameter again for 5.4,
>> that would make portable code a pain. OTOH, the way I did it know, it
>> breaks BC with PHP < 5.3.9, if you want to enable write access in xslt
>> templates in PHP 5.3.9+. If you don't need that, which is maybe 99.9% of
>> all cases, BC is kept for since PHP 5.0 until much after PHP 5.4 :)
>>=20
>> So there are 3 options
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>> 1) leave it like it is currently. No write protection in 5.3, only in 5.4=

>> 2) Have 2 ways to enable write access from 5.3.9+ and 5.4.
>> 3) Remove the ->setSecurityPrefs() in 5.4, so there's only one way to
>> enable write access again, but it's the nasty one from a clean API POV.
>>=20
>> For 2) and 3), code with those new options won't work anymore in 5.3.8-
>> (but you can check it in PHP user land and treat it differently), but
>> you get write protection automatically
>>=20
>> Again, all this will only affect a very small fraction of users, those
>> who legitimately wrote files from within XSLT.
>>=20
>> Any opinions? Me personally would like to have it in PHP 5.3 (or at
>> least offer a proper patch).
>>=20
>> chregu
>>=20
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> --=20
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