[arm-allstar] Workaround: How to use *4 Remote Command mode?

[John Wagner]

A few days ago I posted a question about using the *4 remote command function in Allstar to be able to enter DTMF on one node, and have it execute functions on another node. I was not able to get the *4 remote command function to work, and didn’t receive any good tips on what I was doing wrong. 

Here’s what I ended up doing instead and I figured I’d post it to the list in hopes it helps someone else in the future. 

For this to work, Node #1 needs to be able to reach Node #2 via SSH, and you’ll need to be able to log into both. In our case they’re all behind the same firewall, but you could accomplish the same thing with port forwarding, VPN, or other techniques. As always, if you’re going to expose your SSH directly to the Internet, use strong passwords, patch often, and use non-standard ports.

Short version of entering DTMF on Node #1 and having it execute commands on Node #2: 
1. On Node #1, generate SSH keys so a script can log in from one node to another node via SSH without entering a password, and copy the public key Node #2. Instructions here: https://www.digitalocean.com/community/tutorials/how-to-set-up-ssh-keys--2
2. Make a shell script on Node #1 that uses SSH and the key you created and copied in step 1 to run a command on Node #2. Instructions on how to remotely execute commands via SSH are here: https://www.cyberciti.biz/faq/unix-linux-execute-command-using-ssh/
3. Test it from the command line on Node #1 to make sure your script works from the command line on Node #1.
4. Add a line in Node #1’s rpt.conf to run the script you created above in step #2 with a DTMF command
5. Restart Asterisk on Node #1, test, celebrate your success.


Longer version of Entering DTMF on Node #1 to make Node #2 announce the time (or any other Allstar function):
In this example - Node #1 is 42757 with the prompt “[root at 42757 ~]#” and Node #2 is 43258 on the IP address 192.168.102.10. Replace node numbers and IP addresses with your own. I tested this with the Say Time function *81, but you should be able to do it with any function.

1. On Node #1, generate SSH keys so a script can log in from one node to another node via SSH, and copy the public key Node #2. Instructions here: https://www.digitalocean.com/community/tutorials/how-to-set-up-ssh-keys--2 .

**** GENERATE A PUBLIC/PRIVATE KEYPAIR FOR SSH ****
[root at 42757 ~]# ssh-keygen -t rsa
   Generating public/private rsa key pair.
   Enter file in which to save the key (/root/.ssh/id_rsa): **leave this blank and hit enter**
   Enter passphrase (empty for no passphrase): **leave this blank and hit enter**
   Enter same passphrase again: **leave this blank and hit enter**
   Your identification has been saved in /root/.ssh/id_rsa.
   Your public key has been saved in /root/.ssh/id_rsa.pub.
   The key fingerprint is:
   SHA256:Xnm12Y0fvvlQ2OSCkk5UkIHnQxN57X1w7TpTzQLzLjA root at 442-7375
   The key's randomart image is:
   +---[RSA 2048]----+
   |           .. . .|
   |            o o.o|
   |             . o-o|
   +----[SHA256]-----+

**** COPY THE PUBLIC KEY TO NODE #2 ****
[root at 42757 ~]# ssh-copy-id -p 222 root at 192.168.102.10
   /usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "/root/.ssh/id_rsa.pub"
   /usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
   /usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
   root at 192.168.102.10's password:  
   Number of key(s) added: 1


2. Make a script to run the SSH command on the other machine. In my case, my script was “/root/saytime-on-43258.sh", and contains one line:
ssh -p 222 root at 192.168.102.10 'asterisk -rx "rpt fun 43258 *81” '


3. From Node #1, make your script executable and test it to make sure time announces on Node #2
[root at 42757 ~]# chmod a+x /root/saytime-on-43258.sh 
[root at 42757 ~]# /root/saytime-on-43258.sh 


4. In the Functions section of /etc/asterisk/rpt.conf , add a line to execute your script when a DTMF sequence is entered. I used *966:
[functions42757]
...
966=cmd,/root/saytime-on-43258.sh
…


5. on Node #1, do an astres.sh to reload the rpt.conf, and then on Node #1 enter DTMF *966 (in my case) on the radio. If you did it all right, the time should be announced on Node #2.