W3C home > Mailing lists > Public > www-validator@w3.org > April 2003

Re: Self-reference possible with validation service

From: Terje Bless <link@pobox.com>
Date: Sun, 20 Apr 2003 05:51:03 +0200
To: W3C Validator <www-validator@w3.org>
cc: SteveC <steve@fractalus.com>
Message-ID: <a0106000f-1025-4F5118BF72E311D7B5DF0030657B83E8@[]>

SteveC <steve@fractalus.com> wrote:

I thought I'd replied to this, but now I suddenly can't find the reply in
my archives; so just to make sure this didn't fall through the cracks...

>It appears possible to ask the validator to check itself, then check
>itself checking itself, then check itself checking itself checking
>itself and so on recursively.
>I tried the first 6 levels of recursion and got a roughly linearly
>increasing delay of about and extra second per recursion level. This
>makes it interesting as a DoS attack as you could cause multiple amounts
>of load on the machine for trivial increase in network traffic.
>I don't know if it is actually calling itself, but the increasing load
>time would seem to suggest it.

Yes, this is actually somewhat of a known issue, though it's good that you
point out that this is a potential Denial of Service issue. The problem is
that it's hard to protect against this sort of thing, at least in a
consistent and reliable manner.

I think we'll at the very least implement some fenceposts for this for
validator.w3.org, but I'm not sure I can see any reliable way to deal with
this in the general case (local installations, say).

I've logged this as Bug #204
<http://www.w3.org/Bugs/Public/show_bug.cgi?id=204>. Feel free to add
yourself to the CC list if you would like to track progress on this issue.

Now Playing "Mississippi Goddam" by "Nina Simone"",
 from the album "Feeling Good - The Very Best Of".
Received on Saturday, 19 April 2003 23:51:27 UTC

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