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Message-ID: <AANLkTimw45aBdz6aenSqnZaYOmJPpEyM4=AK7RVHsQVC@mail.gmail.com> Date: Tue, 8 Mar 2011 21:09:49 +1100 From: dave b <db.pub.mail@...il.com> To: full-disclosure@...ts.grok.org.uk Cc: Joachim Schipper <joachim@...chimschipper.nl> Subject: Re: Mutt: failure to check server certificate in SMTP TLS connection On 8 March 2011 19:00, Joachim Schipper <joachim@...chimschipper.nl> wrote: > On Tue, Mar 08, 2011 at 12:36:01PM +1100, dave b wrote: >> Hi all. It seems that mutt fails to check the validity of a SMTP >> servers certificate during a TLS connection. In my mutt configuration >> I have >> >> set ssl_starttls = yes >> set ssl_force_tls = yes >> >> However, after performing the steps below I found that mutt did not >> properly validate the remote servers SMTP tls certificate. This means >> that an attacker could potentially MITM a mutt user connecting to >> their SMTP server even when the user has forced a TLS connection. >> >> Steps to test this: >> 1. I set in my hosts file the ip for smtp.gmail.com to be bound to >> mail.lolok.com >> >> in /etc/hosts >> 74.125.127.109 mail.LOLOK.com >> >> 2.Then I changed my >> >> set smtp_url = "smtp://MYUSERNAME@...p.gmail.com:587/" >> to be >> set smtp_url = "smtp://MYUSERNAME@...l.lolok.com:587/" >> >> 3. I opened up mutt and emailed my self. I note that I saw mutt say >> "connecting to mail.lolok.com". >> >> I feel that this is an issue because mutt _does_ actually perform IMAP >> server certificate validation (at least it did when I last tested it >> :P). > > I'm on the train and not able to test, but the muttrc(5) man page has > > smtp_url > Type: string > Default: "" > > Defines the SMTP smarthost where sent messages should relayed > for delivery. This should take the form of an SMTP URL, e.g.: > > > > smtp[s]://[user[:pass]@]host[:port] > > > > where "[...]" denotes an optional part. Setting this variable > overrides the value of the $sendmail variable. > > Note the "[s]". But yes, you should arguably file a documentation-bug > with the Mutt maintainers, since ssl_starttls does suggest that it works > for SMTP too. Oh really? I'll test it out now! _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.grok.org.uk/full-disclosure-charter.html Hosted and sponsored by Secunia - http://secunia.com/
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