Re: Re: Firewalls breaking stuff: [Was re: fwtk]

["Marcus J. Ranum" <mjr () ranum com>]

Charles W. Swiger wrote:
> Please explain why SMTP AUTH or performing SSL-based encryption of mail en transit via STARTTLS is "stupid" rather 
> than important functionality which improves security?

OK. It seems pretty straightforward so I didn't elaborate sufficiently
on the first pass...

The last time I downloaded the SSL codebase library it was humongous.
I'm sure it's got more security bugs in it than a college dorm room
has cockroaches. We just haven't found them all yet - probably because
it's huge. So by adding SSL you're incorporating one huge thing into
another huge thing. Not only that, it's something hooked to a network
that accepts connections from the entire planet. That's just a bad idea.

SMTP AUTH I have't looked at the code for, but I bet it's another
plate of spaghetti.

But one thing I can tell you for sure!!! If they aren't built into
my mailer, I don't have to worry about 'em!! That's my whole point.
ESMTP was still a-borning when I wrote smap and I looked at it and
it was complicated and not necessary to support in order to collect
mail. Since it wasn't necessary, I left it out. I guess that's a
philosophical point I haven't raised: things that aren't strictly
necessary, if you're writing security code, are, by definition, dumb.

> If you also provide SSL-based IMAP (993/tcp), you can provide email access for remote employees where their usernames, 
> passwords, and the mail itself is never sent in plain text.  That seems quite worthwhile to me.

All built into the same mailer? Heck, why not throw a perl interpreter
in there while you're at it! And make it an SSL web server, too,
since you've already got SSL in there and it's already handling
everything else in one process. Shoot, why not just write the whole
thing as an apache plug-in and then it'll be _really_ secure! :)

> Someone capable of implementing SMTP correctly is more likely to produce secure code than someone not capable of 
> implementing SMTP correctly.  

Someone perfectly capable of implementing SMTP correctly may
just choose to omit features that made for a larger, more
complex, harder to secure implementation. This is both laziness
and a quest for perfection. It is the zen of knowing what is
enough.

mjr.
---
Marcus J. Ranum                         http://www.ranum.com
Computer and Communications Security    mjr () ranum com

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