Monthly Archives: February 2015

Renewing SSL certificates

It is that time of the year when I needed to renew all of my SSL certificates for my web servers and email servers.  This post is a reminder for myself on the steps and commands needed to succesfully renew the certificates, for future reference.

First, check the current certificates and key files.  For CentOS 6, this is located at /etc/pki/tls/private and /etc/pki/tls/certs.

[root@localhost ~]# cd /etc/pki/tls/private
[root@localhost private]# ls -lart
-rw-------. 1 root root 1704 Feb 19  2014 localhost.key
-rw-r--r--. 1 root root 1033 Feb 20  2014 localhost.csr
drwxr-xr-x. 5 root root 4096 Jan 29 15:33 ..
drwxr-xr-x. 2 root root 4096 Feb 16 09:06 .
[root@localhost private]# cd ../certs
[root@localhost certs]# ls -lart
-rw-r--r--. 1 root root    1805 Feb 20  2014 localhost.crt
-rw-r--r--. 1 root root    1757 Feb 20  2014 localhost-chain.crt
-rw-r--r--. 1 root root    1521 Feb 20  2014 localhost-root.crt
-rw-r--r--. 1 root root    5083 Feb 20  2014 localhost-postfix.crt
-rw-r--r--. 1 root root 1005005 Jul 14  2014
-rw-r--r--. 1 root root  786601 Jul 14  2014 ca-bundle.crt
-rwxr-xr-x. 1 root root     829 Jan 21 01:32 renew-dummy-cert
-rw-r--r--. 1 root root    2242 Jan 21 01:32 Makefile
-rwxr-xr-x. 1 root root     610 Jan 21 01:32 make-dummy-cert
drwxr-xr-x. 5 root root    4096 Jan 29 15:33 ..
drwxr-xr-x. 2 root root    4096 Feb 16 09:09 .

Next create the new certificate signing request (CSR).  Take this chance to create a new private key, with perhaps a higher number of bits and a better algorithm.  This is done using the -newkey, -sha256, and -keyout flags.  The -nodes flag is used to create the new private key without a passphrase (so that the services using the private key can start without needing input from a human).

[root@localhost ~]# cd /etc/pki/tls/private/
[root@localhost private]# openssl req -nodes -newkey rsa:4096 -sha256 -keyout localhost-new.key -out localhost-new.csr
Generating a 4096 bit RSA private key
writing new private key to 'localhost-new.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) [XX]:MY
State or Province Name (full name) []:Kuala Lumpur
Locality Name (eg, city) [Default City]:Kuala Lumpur
Organization Name (eg, company) [Default Company Ltd]
Organizational Unit Name (eg, section) []:localhost
Common Name (eg, your name or your server's hostname) []
Email Address []:

Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:
An optional company name []:
[root@localhost private]# ls -lart
-rw-------. 1 root root 1704 Feb 19  2014 localhost.key
-rw-r--r--. 1 root root 1033 Feb 20  2014 localhost.csr
drwxr-xr-x. 5 root root 4096 Jan 29 15:33 ..
-rw-r--r--. 1 root root 3272 Feb 16 10:05 localhost-new.key
-rw-r--r--. 1 root root 1748 Feb 16 10:05 localhost-new.csr
drwxr-xr-x. 2 root root 4096 Feb 16 10:05 .

Send the CSR file (localhost-new.csr) to the certificate authority, and wait for them to issue the certificate for your new key.  Put the certificate files (including the CA root and chain) in the /etc/pki/tls/certs directory.  Do not overwrite the old certificates yet!  I named them localhost-new.crt, localhost-chain-new.crt and localhost-root-new.crt

Now we need to stop all the services using the old certificates.

[root@localhost ~]# service httpd stop
Stopping httpd:                                            [  OK  ]
[root@localhost ~]# service dovecot stop
Stopping Dovecot Imap:                                     [  OK  ]
[root@localhost ~]# service postfix stop
Shutting down postfix:                                     [  OK  ]

Now rename the old certificates for backup.

[root@localhost ~]# cd /etc/pki/tls/certs
[root@localhost certs]# mv localhost.crt localhost-old.crt
[root@localhost certs]# mv localhost-chain.crt localhost-chain-old.crt
[root@localhost certs]# mv localhost-root.crt localhost-root-old.crt

[root@localhost certs]# mv localhost-postfix.crt localhost-postfix-old.crt

Then it is time to rename the new certificates to take the old certificates’ names.

[root@localhost certs]# mv localhost-new.crt localhost.crt
[root@localhost certs]# mv localhost-chain-new.crt localhost-chain.crt
[root@localhost certs]# mv localhost-root-new.crt localhost-root.crt

For postfix, all the root, chain and host certificates need to be in one file.  Create that file, taking the old file name.

[root@localhost certs]# cat localhost.crt >> localhost-postfix.crt
[root@localhost certs]# cat localhost-chain.crt >> localhost-postfix.crt
[root@localhost certs]# cat localhost-root.crt >> localhost-postfix.crt

Start all the services that was stopped.

[root@localhost ~]# service postfix start
Starting postfix:                                          [  OK  ]
[root@localhost ~]# service dovecot start
Starting Dovecot Imap:                                     [  OK  ]
[root@localhost ~]# service httpd start
Starting httpd:                                            [  OK  ]

If everything is done correctly, this should be the end of the exercise.  Test all the services and make sure everything is working as before.