- Red Hat Enterprise Linux (RHEL)
- How to setup and test SMTP AUTH within Sendmail
1. Setting up SMTP AUTH:
- Install following packages by using yum or update command.
cyrus-sasl-gssapi cyrus-sasl-md5 cyrus-sasl cyrus-sasl-plain cyrus-sasl-devel
- Start "saslauthd" service
# service saslauthd start # chkconfig saslauthd on
- Within the /etc/mail/sendmail.mc make sure following lines are uncommented
TRUST_AUTH_MECH(`EXTERNAL DIGEST-MD5 CRAM-MD5 LOGIN PLAIN'')dnl define(`confAUTH_MECHANISMS'', `EXTERNAL GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLAIN'')dnl
- Run m4 command to rebuild the sendmail.cf file:
# cp /etc/mail/sendmail.mc /etc/mail/sendmail.mc.orig # cp /etc/mail/sendmail.cf /etc/mail/sendmail.cf.orig # m4 /etc/mail/sendmail.mc > /etc/mail/sendmail.cf
- Restart sendmail and saslauthd
# service saslauthd restart Stopping saslauthd: [ OK ] Starting saslauthd: [ OK ] # service sendmail restart Shutting down sendmail: [ OK ] Shutting down sm-client: [ OK ] Starting sendmail: [ OK ] Starting sm-client: [ OK ]
2. Testing SMTP AUTH
To test SMTP AUTH from command line a valid username/password is required, following command uses username "test" and password "redhat" as example.
Generate base64 encoded string for username and password
# echo -ne "\0test\0redhat" | base64 AHRlc3QAcmVkaGF0
- Telnet can be used to test SMTP AUTH by using above encoded string
# telnet 127.0.0.1 25 Trying 127.0.0.1... Connected to localhost.localdomain (127.0.0.1). Escape character is ''^]''. 220 dhcp.redhat.com ESMTP Sendmail 8.12.10/8.12.10; Wed, 24 Mar 2004 13:03:57 -0500 hello test 250-dhcp.redhat.com Hello localhost.localdomain [127.0.0.1], pleased to meet you 250-ENHANCEDSTATUSCODES 250-PIPELINING 250-8BITMIME 250-SIZE 250-DSN 250-ETRN 250-AUTH GSSAPI DIGEST-MD5 CRAM-MD5 LOGIN PLAIN 250-DELIVERBY 250 HELP auth plain AHRlc3QAcmVkaGF0 235 2.0.0 OK Authenticated quit 221 2.0.0 dhcp.redhat.com closing connection Connection closed by foreign host.
- Note: Be sure to remove the
pam_stack.somodule if you are using RHEL 5 or newer.
For example /etc/pam.d/smtp:
#%PAM-1.0 auth include password-auth account include password-auth
A possible issue is that if you have postfix also installed (a known bug) - postfix will remove the needed pam smtp auth file, without it SMTP-AUTH within sendmail will fail. Check to see if the following file exists and has the following data within it (in fact my system had postfix installed and so I needed to fix this during verification and testing while witting this up) :
# cp /etc/pam.d/smtp.postfix /etc/pam.d/smtp # cat /etc/pam.d/smtp #%PAM-1.0 auth required pam_stack.so service=system-auth account required pam_stack.so service=system-auth #
The bugzilla on this issue can be found at:
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