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From Marc Slemko <ma...@znep.com>
Subject Re: Apache 1.3.27 mod_proxy security issue
Date Wed, 30 Jul 2003 17:19:18 GMT
On Tue, 29 Jul 2003, Joshua Slive wrote:

>
> On Tue, 29 Jul 2003, William A. Rowe, Jr. wrote:
> > At 12:31 PM 7/23/2003, Greg A. Woods wrote:
> >
> > >I don't know how clients are matched against domains in ACL statements
> > >such as the above in Apache, but I will note that it is NEVER safe to
> > >rely on the Reverse DNS alone to implement ACLs that affect the ability
> > >of a random remote client system.
> >
> > On this point, too, it would be valuable to provide an example subnet as
> > a preferable alternative to reverse DNS queries.  That change has not been
> > made yet - but is referred to our documentation project.
>
> Apache does double-reverse lookups to assure that nothing too funky is
> going on, so using dns names is relatively safe.  It is still better to
> use an IP subnet for performance reasons, but the hostname may be easier
> to understand as an example.

Plus for 95% of installations, the performance really doesn't matter.
What matters more is the possibility of broken reverse DNS causing it
not to work in ways that are non obvious to many people.

However, this double reverse doesn't seem to be documented in mod_access...
there should probably be a note there saying it will force double
lookups... this is documented in the HostnameLookups directive, but
should be explicitly mentioned (not just linked to without mentioning
the double reverse issue) in the mod_access docs.

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