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References: <A91E718E-B023-42DC-AC8D-BC989F5A80E4@cschneid.com> <CAF+90c_75x0ZoD63CoLXY3kUKNQQuR_HhaO998osHuzV7ZGXuw@mail.gmail.com>
In-Reply-To: <CAF+90c_75x0ZoD63CoLXY3kUKNQQuR_HhaO998osHuzV7ZGXuw@mail.gmail.com>
Date: Wed, 30 Oct 2019 18:32:32 +0000
Message-ID: <CAEKnhAHbUf0w1WYqHWYAQD79DJo21HFC1cYoo07AV12NhpBAQQ@mail.gmail.com>
To: Nikita Popov <nikita.ppv@gmail.com>
Cc: Christian Schneider <cschneid@cschneid.com>, PHP internals list <internals@lists.php.net>
Content-Type: multipart/alternative; boundary="0000000000006d4472059624f58b"
Subject: Re: [PHP-DEV] PHP 7.4 BC break with openssl_random_pseudo_bytes()
From: bukka@php.net (Jakub Zelenka)

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On Mon, 23 Sep 2019, 14:02 Nikita Popov, <nikita.ppv@gmail.com> wrote:

> On Mon, Sep 23, 2019 at 2:52 PM Christian Schneider <cschneid@cschneid.com
> >
> wrote:
>
> > Hi,
> > I just noted (too late in the process, I know) that
> > openssl_random_pseudo_bytes(0) now throws an exception.
> >
> > This breaks code like
> >         $ivsize = openssl_cipher_iv_length($method);
> >         $iv = openssl_random_pseudo_bytes($ivsize);
> >         $data = openssl_encrypt($string, $method, $key, OPENSSL_RAW_DATA,
> > $iv);
> > if $method is 'aes-256-ecb' because $ivsize is 0.
> >
> > I do realize that ECB mode ciphers are deprecated but having them throw
> an
> > exception indirectly via openssl_random_pseudo_bytes() seems a bit
> strange,
> > even in the context of security.
> >
> > I checked the RFC
> > https://wiki.php.net/rfc/improve-openssl-random-pseudo-bytes and it
> > doesn't mention this BC break:
> > "False-checks on the return value of openssl_random_pseudo_bytes() will
> do
> > nothing since the function fails closed. Usage of $crypto_strongwill
> > generate errors."
> >
> > While I would have preferred the exception to be thrown only when $ivsize
> > is not an integer or less than 0 but I guess this cannot be changed at
> the
> > RC stage.
> >
> > I would recommend though that we aim to keep BC breaks to what's
> mentioned
> > in RFCs.
> >
>
> This was noted during the PR review in:
> https://github.com/php/php-src/pull/3649#discussion_r230598754 Especially
> in conjunction with your example, I think we should revert this part an
> make openssl_random_pseudo_bytes(0) return "" without exception or warning.
> Ideally we'd adjust random_bytes() to do the same.
>

I agree this should be reverted for 7.4 at least as it's a BC and wasn't
really in RFC. It really doesn't matter if it's a good thing or not as it's
a BC that we shouldn't do in minor release.

Jakub

>

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