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 () smtp gmail com:587/"
to be
set smtp_url = "smtp://MYUSERNAME () mail 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.
