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Date: Mon, 23 Dec 2013 09:26:05 +0800
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To: =?ISO-8859-1?Q?Rouven_We=DFling?= <me@rouvenwessling.de>
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Content-Type: multipart/alternative; boundary=089e0115f90202e9a704ee298323
Subject: Re: [PHP-DEV] [RFC] Timing attack safe string comparison function
From: tjerk.meesters@gmail.com (Tjerk Meesters)

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Hi,


On Mon, Dec 23, 2013 at 1:08 AM, Rouven We=DFling <me@rouvenwessling.de>wro=
te:

> Hi internals,
>
> I'd like to propose this RFC to introduce a time-constant string
> comparison function: https://wiki.php.net/rfc/timing_attack
>
>
On the whole it looks okay.

The special branch for `known_len =3D=3D 0 && user_len !=3D 0` can be avoid=
ed by
doing something like this:

    mod_len =3D max(known_len, 1);

And then use `j % mod_len` instead of `j % known_len` to avoid a division
by zero; since `x mod 1` always yields `0` you will always be comparing
against the null byte of the known string.

I will not open the voting before January 7 to account for holidays.
>
> Best regards
> Rouven
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> PHP Internals - PHP Runtime Development Mailing List
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>
>


--=20
--
Tjerk

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