Sendmail With Optional Auth

dschuett · 05-21-2014, 09:05 PM

I have a CentOS 6.5 server running sendmail. I use this server as a smarthost for all my other servers. I use the /etc/access file to control what machines are allowed to use this server as a relay using:

Code:

Connect:192.168.100.1 RELAY
Connect:192.168.100.2 RELAY

mydomain.com RELAY

This is all working great. The issue I am having is that I use IMAP in order to send and receive emails on my cell phone. I can receive email just fine. However, I am unable to use the server as a relay to send email from my phone because (obviously) my phone has a dynamic IP, so I can't add it to the access.db.

Is there a way to set up some sort of optional auth mechanism for my cell phone to authenticate with sendmail to allow it to use the server as a relay for outbound email from my phone?

Rawcous · 05-22-2014, 08:10 AM

Hello "dschuett",

I have kind of been thinking the same thing myself in terms of accessing my domain mail via my smart phone. Until I have the time to sit down and read all the blurb and do it the proper way I have done the following:

1. Installed Webmin, a great web-based tool that can be used for locally and remotely administering a *Nix - type server.
2. Create a restricted webmin user account that can only read / create emails for specific accounts (blocking access to any admin activities).
3. Access webmin via my smartphone's browser.

The only downside (if it can be considered a downside), is that it requires the installation & configuration of Apache (not an issue), domain registration & hosting

I have done it - nice and simple.

As mentioned it's only a temporary measure until I find the time to do things "properly". I am sure there are hundreds of guys out there who can provide a quick-fire step-by-step guide on how-to's

Regards,

Rawcous!

dschuett · 05-22-2014, 09:53 AM

## Install Needed Packages

Code:

yum install sendmail sendmail-cf cyrus-sasl-plain cyrus-sasl-md5

## Edit /etc/sasl2/Sendmail.conf

Code:

pwcheck_method:saslauthd

## Edit /etc/pam.d/smtp

Code:

#%PAM-1.0
auth       include      system-auth
account    include      system-auth

## Edit /etc/sysconfig/saslauthd

Code:

MECH=pam
# these two settings are the defaults
SOCKETDIR=/var/run/saslauthd
FLAGS=

## Start saslauthd

Code:

chkconfig saslauthd on
service saslauthd start

## Add/Edit These Lines To sendmail.mc

Code:

TRUST_AUTH_MECH(`EXTERNAL DIGEST-MD5 CRAM-MD5 LOGIN PLAIN PAM')dnl
define(`confAUTH_MECHANISMS', `EXTERNAL GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLAIN PAM')dnl

define(`CERT_DIR', `/etc/mail/certs')
define(`confCACERT_PATH', `CERT_DIR')
define(`confCACERT', `CERT_DIR/ca-bundle.crt')
define(`confCRL', `CERT_DIR/ca-bundle.crt')
define(`confSERVER_CERT', `CERT_DIR/sendmail.pem')
define(`confSERVER_KEY', `CERT_DIR/sendmail.pem')
define(`confCLIENT_CERT', `CERT_DIR/sendmail.pem')
define(`confCLIENT_KEY', `CERT_DIR/sendmail.pem')

define(`confAUTH_OPTIONS', `A p y')dnl

DAEMON_OPTIONS(`Port=smtp,Addr=0.0.0.0, Name=MTA')dnl
DAEMON_OPTIONS(`Port=smtps,Addr=0.0.0.0, Name=MTA-SSL M=E')dnl

## Create The Certs

Code:

cd /etc/mail
mkdir certs
cd certs
openssl req -new -x509 -keyout cakey.pem -out cacert.pem -days 365
openssl req -nodes -new -x509 -keyout sendmail.pem -out sendmail.pem -days 365
cp /etc/ssl/certs/ca-bundle.crt /etc/mail/certs
chmod -R 600 /etc/mail/certs/*

## Add trusted user to /etc/mail/trusted-users

Code:

yourlinuxusername

## Make New sendmail.cf and restart

Code:

m4 /etc/mail/sendmail.mc > /etc/mail/sendmail.cf
service sendmail restart

Profit!