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full-disclosure-uk: Re: [Full-disclosure] noise about full-width

Re: [Full-disclosure] noise about full-width encoding bypass?

From: Steven Adair <steven_at_nospam>
Date: Mon May 21 2007 - 19:41:58 GMT
To: "Brian Eaton" <eaton.lists@gmail.com>


> On 5/21/07, ascii <ascii@katamail.com> wrote:
>> Brian Eaton wrote:
>> > To summarize what I've heard from various sources: I am missing
>> > something important. =) Both PHP and ASP.NET will decode these
>> > characters into their ASCII equivalents.
>>
>> (AFAIK)
>>
>> Only ASP.NET/IIS decodes that automatically.
>>
>> PHP *can* do that as like JSP and probably others but that has
>> to happen explicitly in the application code or on an other layer.
>
> (Cracking up that somebody going by the handle ascii is commenting on
> character encoding issues. =)
>
> Given how few application platforms decode full-width unicode to ASCII
> equivalents, is there a case to be made that those application
> platforms that do decide this conversion is a good idea are broken?
>
> Put another way: should this be considered a bug in ASP.NET?
>

I think you could be on either side, but I would learn towards this being a feature than a bug. Multiple products appear to do the decoding in the same manner and intentionally perform this function. However, the recent advisories that went out were geared towards IDS/IPS products that were not designed to be able to recognize such half-/full-width encoded traffic. Unless there is some RFC or generally followed documentation saying the traffic should not be encoded/decoded as such, I would continue to lean towards this being a feature. It just appears to be a place much of the IT (security) world has overlooked.

Steven
securityzone.org

> Regards,
> Brian
>
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