View source for Linux Postfix SMTP (Mail Server) SSL Certificate Installations and Configuration

Sumber: http://www.cyberciti.biz/tips/postfix-smtp-ssl-certificate-csr-installation-guide.html

In this tutorial you will learn about Installing SSL Certificate (Secure Server Certificate) to secure communication between Postfix SMTP server and mail client such as Outlook or Thunderbird.

You need to generate a CSR certificate for CA, to use with your Postfix mail server. This tutorial instuctions are tested under:

# Redhat enterprise Linux 5
# CentOS 5 Server
# FreeBSD 7 server

Procedure for creating a CSR on postfix MTA is just like web server. You need to use OpenSSL which is a cryptography toolkit implementing the Secure Sockets Layer (SSL v2/v3) and Transport Layer Security (TLS v1) network protocols and related cryptography standards under Linux / UNIX. To configure postfix SSL SMTP you need 3 files

* The private key generated using step #1
* Your .crt certificate file (it will be send by CA)
* CA certificate (also known as

Let us see how to create certificate for Postfix smtp server called smtp.theos.in.

===Step # 1: Generating a CSR and private key for Postfix SMTP===

Type the command to create a SSL CSR for a mail server called smtp.theos.in:

 mkdir /etc/postfix/ssl
 cd /etc/postfix/ssl/
 openssl req -new -nodes -keyout onnocenter.id.key -out onnocenter.id.csr

 Generating a 2048 bit RSA private key
 ......................+++
 ..................+++
 writing new private key to 'onnocenter.id.key'
 -----
 You are about to be asked to enter information that will be incorporated
 into your certificate request.
 What you are about to enter is what is called a Distinguished Name or a DN.
 There are quite a few fields but you can leave some blank
 For some fields there will be a default value,
 If you enter '.', the field will be left blank.
 -----
 Country Name (2 letter code) [AU]:ID
 State or Province Name (full name) [Some-State]:DKI     
 Locality Name (eg, city) []:Jakarta
 Organization Name (eg, company) [Internet Widgits Pty Ltd]:OnnoCenter
 Organizational Unit Name (eg, section) []:IT
 Common Name (e.g. server FQDN or YOUR name) []:onnocenter.id
 Email Address []:onno@onnocenter.id 
 
 Please enter the following 'extra' attributes
 to be sent with your certificate request
 A challenge password []:password
 An optional company name []:OnnoCenter

===Step # 2: Submit CSR to CA===

Now a CSR is generated. All you have to do is copy and paste the contents of the CSR file into the SSL certificate providers (aka CA) account. Never ever give out your private key or certificate to anyone. After verification you should receive a zip file with certificates.

===Step # 3 : Install your SSL certificate===

Unzip file and upload certificates to /etc/postfix/ssl directory.

===Step # 4: Configure Postfix SMTP for SSL certificate===

Open postfix smtp configuration file and append following directive:

 smtpd_use_tls = yes
 smtpd_tls_auth_only = yes
 smtpd_tls_key_file = /etc/postfix/ssl/smtp.theos.in.key
 smtpd_tls_cert_file = /etc/postfix/ssl/smtp.theos.in.crt
 smtpd_tls_CAfile = /etc/postfix/ssl/caroot.crt
 smtpd_tls_loglevel = 1 
 
 smtpd_tls_received_header = yes
 smtpd_tls_session_cache_timeout = 3600s
 tls_random_source = dev:/dev/urandom

Save and close the file. Restart or reload postfix service

 # postfix reload.
OR
 # /etc/init.d/postfix restart

Note I have SASL configured as follows in main.cf:

 smtpd_sasl_auth_enable = yes
 smtpd_sasl_local_domain =
 smtpd_sasl_security_options=noanonymous
 smtpd_recipient_restrictions = permit_sasl_authenticated, reject_unauth_destination, permit_mynetworks check_relay_domains
 smtpd_delay_reject = yes
 broken_sasl_auth_clients = yes

===Test Postfix TLS (SSL)===

In order to test the TLS, just telnet smpt.theos.in on port 25 (you must see STARTTLS and AUTH lines):

 $ telnet onnocenter.id 25

Output:

 220 onnocenter.id ESMTP

 ehlo onnocenter.id

 250-onnocenter.id
 250-PIPELINING
 250-SIZE 10240000
 250-VRFY
 250-ETRN
 250-STARTTLS
 250-AUTH DIGEST-MD5 NTLM CRAM-MD5 PLAIN LOGIN
 250-AUTH=DIGEST-MD5 NTLM CRAM-MD5 PLAIN LOGIN
 250-ENHANCEDSTATUSCODES
 250-8BITMIME
 250 DSN

And mail log file...

 # tail -f /var/log/maillog

Output:

 Jul 12 14:25:10 smtp postfix/smtpd[28817]: connect from unknown[84.167.114.61]
 Jul 12 14:25:11 smtp postfix/smtpd[28817]: setting up TLS connection from unknown[84.167.114.61]
 Jul 12 14:25:11 smtp postfix/smtpd[28817]: TLS connection established from unknown[84.167.114.61]: TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)
 Jul 12 14:25:12 smtp postfix/smtpd[28817]: B3A0A9D8443: client=unknown[84.167.114.61], sasl_method=PLAIN, sasl_username=user1@theos.in
 Jul 12 14:25:13 smtp postfix/cleanup[28807]: B3A0A9D8443: message-id=<46968015.50400@theos.in>
 Jul 12 14:25:13 smtp postfix/qmgr[28806]: B3A0A9D8443: from=, size=632, nrcpt=1 (queue active)
 Jul 12 14:25:14 smtp postfix/smtpd[28817]: disconnect from unknown[122.167.114.61]
 Jul 12 14:25:14 smtp postfix/smtp[28821]: B3A0A9D8443: to=, relay=aspmx.l.google.com[209.85.163.27]:25, delay=2.1, delays=1.5/0 /0.13/0.49, dsn=2.0.0, status=sent (250 2.0.0 OK 1184268314 n29si21297786elf)
 Jul 12 14:25:14 smtp postfix/qmgr[28806]: B3A0A9D8443: removed

You can use same SSL security certificates with dovecot secure IMAPS / POP3S server.
See also:

If you just need self signed postfix SSL certificate please see this tutorial for more information.

==Referensi==

* http://www.cyberciti.biz/tips/postfix-smtp-ssl-certificate-csr-installation-guide.html

==Pranala Menarik==

* [[Keamanan Jaringan]]
* [[Linux Howto]]

[[Category: Network Security]]