Ejecutando comandos del sistema desde Asterisk

 Con la Aplicacion System() podemos ejecutar comandos del sistema desde Asterisk. Es decir que llamando a una extension o  selecionando alguna opcion del nuestro IVR, Podriamos reiniciar nuestra central, Descargar un archivo, Borrar un fichero o lo que tu imaginacion y conocimiento te permitan.

UNA NOTA IMPORTANTE PODEMOS USAR EL COMANDO  which   para saber la ruta completa del comando que queremos ejecutar desde Asterisk. Ejemplo para saber la ruta especifica del comando ls

$ which ls
/bin/ls 

System()

[shell]

exten=>500,1,Authenticate(5415)    ; Apaga nuestro Sistema

same=>n,Playback(goodbye)

same=>n,system(/sbin/init 0)

same=>hangup()

exten=>501,1,Authenticate(5415)  ; Reinicia nuestro Sistema

same=>n,Playback(goodbye)

same=>n,system(/sbin/init 6)

same=>hangup()

Example 1

exten => s,1,system(echo "${DATETIME} - ${CALLERID} - ${CHANNEL}" >> /var/log/asterisk/calls)

Example 2

; dial 700 = Restart Asterisk
 exten => 700,1,Playback(posix-restarting) ; "Restarting asterisk"
 exten => 700,2,Wait(1)
 exten => 700,3,System(/usr/sbin/asterisk -rx reload)
 exten => 700,4,Hangup

Example 3

; Extension 200 Mini Call ID WinPopup Example
 exten => 200,1,NoOp(${CALLERID} ${DATETIME})
 exten => 200,2,System(/bin/echo -e "'Incoming Call From: ${CALLERID} \\r Received: ${DATETIME}'"|/usr/bin/smbclient -M target_netbiosname)
 exten => 200,3,Dial,sip/sipuser|30|t        
 exten => 200,4,Congestion

Example 4

 ; Dump call info to a serial receipt printer on ttyS1
 exten => 200,1,NoOp(${CALLERID} ${DATETIME})
 exten => 200,2,System(/bin/echo "'${CALLERID} ${DATETIME}'" > /dev/ttyS1)
 exten => 200,3,Dial,sip/sipuser|30|t        
 exten => 200,4,Congestion

Security

My associate received a call from PG&E and realized the horror of System()

Problem

Running System() has access to any program the user running asterisk has access to
CALLERID can be set by a remote user

Example

exten => 200,1,Set(CALLERID(NAME)=PG&/bin/echo BADIDEA > /ROOTED.txt)
exten => 200,2,System(/bin/echo -e "'Incoming Call From: ${CALLERID} \\r Received: ${DATETIME}'"|/usr/bin/smbclient -M target_netbiosname)

Measure 1

By using perl I was able to prevent the first example but I'm sure the possibility is still there:

exten => 200,1,Set(CALLERID(NAME)=PG&/bin/echo BADIDEA > /ROOTED.txt)
exten => 200,2,System(/bin/perl -e 'print Incoming Call From:" . "${CALLERIDNAME}" | /usr/bin/smbclient -M target_netbiosname)

Measure 2

Fine tune this to your liking:

[macro-smb-cid]
exten => s,1,NoOp
exten => s,2,Set(regx="([a-zA-Z0-9]+)")
exten => s,3,Set(CCIDNAME=$["${CALLERIDNAME}": ${regx}])
exten => s,4,Set(regx="([0-9]+)")
exten => s,5,Set(CCIDNUM=$["${CALLERIDNUM}": ${regx}])
exten => s,6,TrySystem(/usr/bin/perl -e \'print "${DATETIME} " . " ${CCIDNAME} " . " \<${CCIDNUM}\>" \' | /usr/bin/smbclient -M target_netbiosname)

Update!! Asterisk-1.4 returns 0 (as it should) when your regex matches. Instead use the function FILTER.
This example is experimental...
[macro-smb-cid]
exten => s,1,NoOp
exten => s,2,Set(FLTNA=0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz)
exten => s,3,Set(CIDNA=${FILTER(${FLTNA},${CALLERID(NAME)})})
exten => s,4,Set(FLTNU=(0123456789)
exten => s,5,Set(CIDNU=${FILTER(${FLTNU},${CALLERID(num)})})
exten => s,6,TrySystem(/usr/bin/perl -e \'print "${DATETIME} " . " ${CCIDNAME} " . " \<${CCIDNUM}\>" \' | /usr/bin/smbclient -M target_netbiosname)

I'd like to hear from you if you know another way... cwidger@gmail.com
what's wrong with using System(su userWithNoRights -c "some command") ?

See also

• Asterisk cmd TrySystem: Unlike System() returns 0 on any situation
• Asterisk func SHELL: Function to return a value from a Shell script (introduced in Asterisk 1.6.0)
• Asterisk cmd ReadFile - Read contents of a file into a dialplan variable
• Backticks: Application to return a value from a Shell script
• Asterisk cmd Exec: Execute a dialplan application
• Asterisk cmd ExecIf: Conditionally execute a dialplan application
• AGI: Asterisk Gateway Interface
• Call notification: Example for generating pop-up messages