bugtraq - Re: a cheesy Apache / IIS DoS vuln (+a question)

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Date: Thu, 4 Jan 2007 09:18:23 +0100 (CET)
From: Michal Zalewski <lcamtuf@...ne.ids.pl>
To: "William A. Rowe, Jr." <wrowe@...e-clan.net>
Cc: bugtraq@...urityfocus.com, full-disclosure@...sys.com
Subject: Re: a cheesy Apache / IIS DoS vuln (+a question)

On Wed, 3 Jan 2007, William A. Rowe, Jr. wrote:

> Seriously, HTTP pipelining can accomplish EXACTLY the same thing with minimal
> pain.

No, it can't. Client-side pipelining using simultaneous sessions with
keep-alives is usually severely restricted on server-side (exactly for the
reason they can be abused to DoS the server), and the overhead is much
higher (you need to send hundreds of bytes to request a copy of a static
page).

Here, requesting an extra copy costs you 3 bytes, and that is in my
opinion notable - because you can do it thousands of times in a single
short request.

> If you have an issue with this behavior, of HTTP, then you have an issue
> with the behavior under FTP or a host of other protocols.

Not really; see above. These are typically well known, preventable by
configuring server-side limits, and require a much higher overhead.

/mz