Secure VoIP

From Taridium

Latest revision as of 15:50, 18 July 2011

SIP/TLS and SRTP are experimental!

This will require the asterisk16 or asterisk18 packages for SIP/TLS and asterisk18 for SRTP (encrypted media). Also make sure to use the latest ipbx package release. If you would like to change your Asterisk version, you can use the Switch Updater script.

Configuring SIP/TLS

Creating a Key File and CA

You can use your CA to sign your server certificate or you can use a commercial certificate from places such as http://www.verisign.com/.

$ openssl genrsa -des3 -out ca.key 4096

$ openssl req -new -x509 -days 365 -key ca.key -out ca.crt

Sample CA Cert

 Country Name (2 letter code) [GB]:US
 State or Province Name (full name) [Berkshire]:New York
 Locality Name (eg, city) [Newbury]:New York
 Organization Name (eg, company) [My Company Ltd]:Taridium
 Organizational Unit Name (eg, section) []:engineering
 Common Name (eg, your name or your server's hostname) []:Taridium CA www.taridium.com
 Email Address []:info@taridium.com

$ openssl genrsa -out key.pem 1024

Sample Certificate Signing Request

$ openssl req -new -key key.pem -out req-ipbx_taridium.csr

Country Name (2 letter code) [GB]:US
 State or Province Name (full name) [Berkshire]:New York
 Locality Name (eg, city) [Newbury]:New York
 Organization Name (eg, company) [My Company Ltd]:Taridium
 Organizational Unit Name (eg, section) []:engineering
 Common Name (eg, your name or your server's hostname) []:pbx.taridium.com
 Email Address []:support@taridium.com
 
 Please enter the following 'extra' attributes
 to be sent with your certificate request
 A challenge password []:
 An optional company name []:

Make sure your common name (CN) matches your server. Some phones will check for a matching name! This also means that your phone will have to be configured with the common name.

Creating a Self-Signed Certificate

To create the self-signed certificate, do the following:

$ openssl x509 -req -days 365 -in req-ipbx_taridium.csr -CA ca.crt -CAkey ca.key -set_serial 01 -out cert-ipbx.cert

Installing the Certificate

$ cat key.pem > asterisk.pem
$ cat cert-ipbx.cert >> asterisk.pem

$ mv asterisk.pem /etc/asterisk/
$ chown asterisk:asterisk /etc/asterisk/asterisk.pem

Setting up ipbx for TLS Use

Go to → Manual Editor → SIP Configuration → Edit and add the following parameters:

 [general]
 ...
 tcpenable = yes
 tcpbindaddr = xxx.xxx.xxx.xxx:5060
 tlsenable = yes
 tlsbindaddr = xxx.xxx.xxx.xxx:5061
 tlscertfile = /etc/asterisk/asterisk.pem
 tlsdontverifyserver = no
 ...

Restart Asterisk:

 [root@ipbx ~]# service asterisk restart

Asterisk should now be listening on port 5061. Double check the CLI by issuing a 'sip reload'.

Setting up your Device

ipbx Configuration

Device Configuration

Aastra

Aastra phones using TLS check for the following:

• Whether the certificate hasn't expired (make sure your NTP server is configured)
• Whether the CN (common name) of the certificate matches the SIP registrar and proxy
• Whether the certificate has been signed by a trusted entity. In the above case we have created our own CA certificate. See instructions below on how to place your CA certificate.

1. Place the ca.crt file in your Aastra provisioning directory (on ipbx this is usually /var/www/html/prov)/
2. Configure the Trusted Certificates Filename to be ca.crt
3. In your Global SIP Settings select Advanced SIP Settings → Transport Protocol → Persistent TLS
4. Make sure your proxy and registrar ports are set to 5061

Counterpath Bria for iPhone

Counterpath softphones use your operating system's certificate store to verify your TLS certificates. Place the ca.crt file on a webserver and load it using your browser to store it in our operatings system's certificate store. Use Internet Explorer for Windows or Safari for OS X and iOS (iPhone & iPad) operating systems. For further details on how to setup Bria see Bria for iPhone Setup.