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Bugtraq archives for 1st quarter (Jan-Mar) 1999: Re: Anonymous Qmail Denial of Service

Re: Anonymous Qmail Denial of Service

Nick Andrew (nickZETA.ORG.AU)
Tue, 5 Jan 1999 09:48:55 +1100 

In message <3.0.1.32.19990104013631.0092a770mail.kics.bc.ca>, Trev writes:
>Pardon my comments here, I am no qmail expert (I don't even run the thing),
>but surely you could get around this by applying a small patch to
>qmail-queue to look for such zero-length files and remove any that are
>found (ie: one of the first things it does).

Naively it sounds like a good idea. In practice though, there is a race
condition between one instance of qmail-queue creating a file (at which
point it has zero length) and another instance finding and removing the
same, in-use file. Additional tests would have to be performed such as
testing time-since-creation.

Holistically however, this kind of "cleanup" offends my sense of the tao
of system programming. Processes should not leave crud to be cleaned up by
later, unrelated processes.

Nick.