Askozia. How Autoprovisioning Plug & Play Works

When developing the Askozia PBX, we faced the task of automatically setting up the phones and solved it in our own way.



Autoprovisioning Plug & Play (PnP), this technology is supported by many manufacturers - Yealink, Snom, Fanvil.



The main advantages of automatic phone settings:

• Facilitates initial setup - no need to go to the web interface of each device. It is enough to indicate the correspondence of the MAC address of the device and the account on the auto-tuning server.
• Simplifies support - it really becomes easier if you need to change device settings. We control the settings again on the server
• It is possible to reduce the setting to the set of starcode “* 911 * <SIP_ACC>” - in some cases, this function simply does not have a price. Not every office worker can configure an IP phone, but dialing a combination of numbers is a simple task.

Let's describe how the Autoprovisioning Plug & Play works. At the end of the article, a link to the sources of a small PHP script that implements the functionality of the PnP server.

Case Study

We had an interesting case when introducing telephony to one of our customers. The main problem was that the client was in another city. At the same time, one of the requirements was that after unpacking the parcel with the telephones and plugging them into the network, telephony should immediately work.



The problem was solved relatively simply. The client has reserved a number of IP addresses for us. We set up the equipment in our office and packed it in a box and sent it by courier.



Using automatic device configuration, the task would become much simpler.

Simplified PnP Scheme

The telephone set at the beginning of operation sends a broadcast SIP SUBSCRIBE request to the address 224.0.1.75 multicast IP.



In response, he expects to receive a NOTIFY response with configuration instructions.

The most important and interesting headlines

• From - the poppy address of the device is 0015657322ff
• Event - comprehensively describes the device, Manufacturer, model, firmware version
• Contact - device address
• Call-ID - this header is interesting when configuring DECT devices from Yealink, it transfers the line identifier (tube serial number), delimiter " _ "

Once the PnP server has received such a request, it should respond





In a NOTIFY message, the most valuable information is in the message body. As a rule, in the body you must pass a link to get the configuration file:

 http://172.16.32.153:84/0015657322ff.cfg
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
     

If several PnP servers are running on the network, then who is the first who will respond to the device will configure it.



The phone, upon receipt of NOTIFY, attempts to fulfill the request at the specified address.





An example implementation of the server is available on github https://github.com/boffart/MikoServerPnP



For this PnP server to work, you must:

• PHP 7.1.9
• Php sockets
• BusyBox v1.26.2
• Broadcast requests must be allowed on the network

PnP Server Features

• Listens for requests sent to the address ' 224.0.1.75:5060 '
• When you start, it starts the web server ( busybox httpd )
• Allows you to create a simplified phone configuration
• Allows you to send NOTIFY to Yealink to reboot

Using a PnP server allows you to use "One-time links."

Suppose we give the file by the link:

 http://172.16.32.153:84/0015657322ff.cfg
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
     

The usual direct link to the file. Obviously, this is NOT safe. Knowing the MAC address of the phone and the server address, you can try to get a config with logins and passwords.



When working with a PnP server, it is possible to give a unique link for each SUBSCRIBE request:

 http://172.16.32.153:84/?mac=0015657322ff&hash=0a67f5290
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
     

An example of a formula for calculating a hash:

 hash = md5(MAC + DATE + PID)
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
     

PID is the process ID of the PnP server. Only root can recognize it.

Choosing such a hash is almost impossible.



If an appeal occurs via an invalid link, then we ban the pest.

Reboot Yealink NOTIFY means without authorization

Yes, yes, without authorization .

I could not close the device from the current version of the firmware from this possibility.



Just run the command

 php -f MikoServerPnP.php socket_client_notify <IP_PBX> <PORT_SIP_PBX> <IP_PHONE> <PORT_PHONE>
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
     

And the phone will go into reboot. By hanging such a command in cron you can achieve a terrifying effect. Of course, this is possible if we know the IP address and SIP port of the phone.

PnP Server Setup

Located in settings / settings.json

 { "url": "http://<pbx_host>:<http_port>/", "http_port": 84, "pbx_host": "172.16.32.153", "pbx_sip_port": "5060", "vm_extension": "*001", "feature_transfer": "**" }
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
     

MAC White List

Can be described in settings / mac_white.conf . Separator - line feed.

MAC blacklist

Can be described in settings / mac_black.conf . Separator - line feed.

Phone configuration files

Must be placed in the configs directory.

By means of the PnP server, it is possible to create the simplest configs for Yeakink and Snom:

 php -f MikoServerPnP.php mk_config SIP_ACCAUNT SECRET MAC
      
      

        
        
        
      

    
        
        
        
      
      

        
        
        
      

    
     

Useful materials

• Askozia is a free product. Sources on Github
• Wiki by Snom
• Yealink Support Site
• MikoServerPnP repository on Github