Re: Bug#499774: starttls is a joke

[arno@natisbad.org (Arnaud Ebalard)]

Hi,

Matthias Andree <matthias.andree@gmx.de> writes:

> Reiner Steib <reinersteib+gmane@imap.cc> writes:
>
>>> Then, someone should correct the code to support passing trust anchors,
>>> allow passing the verify value, and document capabilities and
>>> limitations. 
>>
>> Gnus currently uses starttls if starttls and gnutls-cli are available
>> for backward compatibility.  
>>
>> Would it make sense to prefer gnutls-cli and warn when using starttls
>> (if gnutls-cli is not installed)?
>
> It would make sense to fix the tools first, and stop using them in
> unsafe ways.
>
> I recently found on Cygwin, when setting up Emacs+Gnus, that gnutls-cli
> (2.4.2 IIRC) has some subtle "accept b0rked cert chain" behaviour: it
> would happily accept any garbage^Wuntrusted certificate chain without
> notice -- when I'm not using "--x509cafile FOO" on the command line.
> This isn't documented anywhere (manual, manpage, --help), I found this
> out through systematic testing.
>
> I find this most disturbing, since if I don't provide a set of trusted
> X.509 CA certs, I trust nobody (rather than everybody as gnutls-cli
> does)... gnutls-cli should bail out if it has no trusted root
> certificates, rather than silently trust everyone. Go figure - there's a
> difference between giving "--x509cafile /dev/null" and not giving this
> option at all. :-(

Maybe I missed the point in Simon's response below because if you are
correct (I just don't have gnutls-cli on my laptop to test) that
deserves a bug report (and a clarification from Simon): 

http://article.gmane.org/gmane.linux.debian.devel.bugs.general/493201

> While I'm at it, from the end user's perspective, I find it very hard to
> figure what options I need for a proper configuration that doesn't use
> b0rked protocols such as SSLv2, that uses proper X.509 certificate
> validation to detect MITM attacks. Few applications except Firefox 3 get
> that right, and I couldn't tell one off-hand.
>
> I think that EVERY tool that has a remotely security-related context
> should default to bulletproof mode and require that the user relaxes
> every test explicitly.
>
> Yes, I need to do homework here, fetchmail doesn't get this right
> either... compatibility and all that.
>
> So I'd say make Gnus default to gnutls-cli and change the sample
> configuration to include --x509cafile and add instructions to the
> defcustom blah self-documentation telling the user to cat(1) his trusted
> ROOT certificates (in PEM format) together to form this file.

+1 (a big one).

Cheers,

a+