Re: [exim] Really Cool Trick

On Oct 19, 2006, at 3:10 PM, W B Hacker wrote:

>
> If one simply insists on a domain-wide differentiator, such as a
> prefixed/suffixed address format:
>
> <folder/listname>.<real_user>@<domain.tld>
>
> or
>
> <real_user>.<folder/listname>@<domain.tld>
>
> or
> <whatever_else_you_wish_to_parse_embedded_local_part>@<domain>.<tld>
>
> Then *ALL* IMAP users may have this feature. No symlinks required.
>
> CAVEAT: Best to NOT allow the router/transport code for this
> special structure
> to create folders that do not pre-exist.
>
> ELSE you have a catch-all-builder that dictionery attacks may exploit.
>
> - Though one can see uses for that as a 'feature' as well...

We have a setup where accountname*folder@domain will be delivered
straight to the folder and will auto create the folder. This has not
been a problem since they have to know the original accountname and a
dictionary attack against the accountname alone is just as easy as
one with accountname*folder . This allows the users to, at the spur
of the moment, create new folders when entering in email addresses on
web forms, etc, without having to remember to create the folder in
their mua. The downside is that they cannot turn off such addresses
since they will be autocreated. (I have had to go in change the
protections on the folder so that the MTA cannot write into it). I
am thinking about how to allow the autocreate of folders but have a
user administrable way (no local logins for the users) to be able to
turn off a folder and make it inactive.

where * = our special character, not an asterisk


Chad

>
> One might also wish to provide each user with a dynamically-
> generated alias as
> damage control against address harvesting.




---
Chad Leigh -- Shire.Net LLC
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chad at shire.net