[Full-disclosure] Mutt: failure to check server certificate in SMTP TLS connection

[dave b <db.pub.mail@xxxxxxxxx>]

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@xxxxxxxxxxxxxx:587/"
to be
set smtp_url = "smtp://MYUSERNAME@xxxxxxxxxxxxxx: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).

--
Patch griefs with proverbs.             -- William Shakespeare, "Much Ado About 
Nothing"

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