Asterisk SIP/TLS Transport
==========================

When using TLS the client will typically check the validity of the
certificate chain.  So that means you either need a certificate that is
signed by one of the larger CAs, or if you use a self signed certificate
you must install a copy of your CA certificate on the client.

So far this code has been test with:
- Asterisk as client and server (TLS and TCP)
- Polycom Soundpoint IP Phones (TLS and TCP)
	Polycom phones require that the host (ip or hostname) that is
	configured match the 'common name' in the certificate
- Minisip Softphone (TLS and TCP)
- Cisco IOS Gateways (TCP only)
- SNOM 360 (TLS only)
- Zoiper Biz Softphone (TLS and TCP)


sip.conf options
----------------
tlsenable=[yes|no]
	Enable TLS server, default is no

tlsbindaddr=<ip address>
	Specify IP address to bind TLS server to, default is 0.0.0.0

tlscertfile=</path/to/certificate>
	The server's certificate file. Should include the key and 
	certificate.  This is mandatory if your going to run a TLS server.

tlscafile=</path/to/certificate>
	If the server your connecting to uses a self signed certificate
	you should have their certificate installed here so the code can 
	verify the authenticity of their certificate.

tlscadir=</path/to/ca/dir>
	A directory full of CA certificates.  The files must be named with 
	the CA subject name hash value. 
	(see man SSL_CTX_load_verify_locations for more info) 

tlsdontverifyserver=[yes|no]
	If set to yes, don't verify the servers certificate when acting as 
	a client.  If you don't have the server's CA certificate you can
	set this and it will connect without requiring tlscafile to be set.
	Default is no.

tlscipher=<SSL cipher string>
	A string specifying which SSL ciphers to use or not use
	A list of valid SSL cipher strings can be found at: 
		http://www.openssl.org/docs/apps/ciphers.html#CIPHER_STRINGS


Sample config
-------------

Here are the relevant bits of config for setting up TLS between 2
asterisk servers.  With server_a registering to server_b

On server_a:

[general]
tlsenable=yes
tlscertfile=/etc/asterisk/asterisk.pem
tlscafile=/etc/ssl/ca.pem  ; This is the CA file used to generate both certificates
register => tls://100:test@192.168.0.100:5061

[101]
type=friend
context=internal
host=192.168.0.100 ; The host should be either IP or hostname and should 
                   ; match the 'common name' field in the servers certificate
secret=test
dtmfmode=rfc2833
disallow=all
allow=ulaw
transport=tls 
port=5061

On server_b:
[general]
tlsenable=yes
tlscertfile=/etc/asterisk/asterisk.pem

[100]
type=friend
context=internal
host=dynamic
secret=test
dtmfmode=rfc2833
disallow=all
allow=ulaw
;You can specify transport= and port=5061 for TLS, but its not necessary in
;the server configuration, any type of SIP transport will work
;transport=tls 
;port=5061