[asterisk-dev] [Code Review] 3362: func_periodic_hook: New function for periodic hooks.

[Corey Farrell]

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/trunk/funcs/func_periodic_hook.c
<https://reviewboard.asterisk.org/r/3362/#comment21198>

    The xmldoc states that these parameters are required so I think it would be better to report failure if either are ast_strlen_zero.
    
    I have tagged this issue here instead of the documentation since I don't agree with them having defaults.  I would not object strongly if args.exten were optional / default "s", but only if the parameters were reordered to PERIODIC_INTERVAL(interval,context,exten).  My preference is to require the caller to be explicit with all parameters.



/trunk/funcs/func_periodic_hook.c
<https://reviewboard.asterisk.org/r/3362/#comment21200>

    I just had a thought about AMI (and ARI?) security.  This function should be unavailable to users without originate permissions.  I'm not aware of a way to require Originate permissions from someone who is using AMI to write to this function, so I think this might need to use ast_custom_function_register_escalating.
    
    I am very sure with AMI access to read this function and channel events I could perform a DoS attack against the local system while harassing 1 or more individuals with a continuous stream of silent calls (they hangup one call, another call comes within 1 second).  Normally a lack of permission to originate channels should prevent me from doing this.


- Corey Farrell


On April 1, 2014, 12:43 p.m., Russell Bryant wrote:
> 
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> This is an automatically generated e-mail. To reply, visit:
> https://reviewboard.asterisk.org/r/3362/
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> 
> (Updated April 1, 2014, 12:43 p.m.)
> 
> 
> Review request for Asterisk Developers.
> 
> 
> Repository: Asterisk
> 
> 
> Description
> -------
> 
>     This commit introduces a new dialplan function, PERIODIC_HOOK().
>     It allows you run to a dialplan hook on a channel periodically.  The
>     original use case that inspired this was the ability to play a beep
>     periodically into a call being recorded.  The implementation is much
>     more generic though and could be used for many other things.
>     
>     The implementation makes heavy use of existing Asterisk components.
>     It uses a combination of Local channels and ChanSpy() to run some
>     custom dialplan and inject any audio it generates into an active call.
>     
>     The other important bit of the implementation is how it figures out
>     when to trigger the beep playback.  This implementation uses the
>     audiohook API, even though it's not actually touching the audio in any
>     way.  It's a convenient way to get a callback and check if it's time
>     to kick off another beep.  It would be nice if this was timer event
>     based instead of polling based, but unfortunately I don't see a way to
>     do it that won't interfere with other things.
> 
> 
> Diffs
> -----
> 
>   /trunk/funcs/func_periodic_hook.c PRE-CREATION 
>   /trunk/CHANGES 411583 
> 
> Diff: https://reviewboard.asterisk.org/r/3362/diff/
> 
> 
> Testing
> -------
> 
> Called the following extension (100 at test), both letting it run all the way through, as well as hanging up at various points in the middle.
> 
> [hooks]
> 
> exten => beep,1,Answer()
>     same => n,Verbose(1,Channel name: ${HOOK_CHANNEL})
>     same => n,Verbose(1,Hook ID: ${HOOK_ID})
>     same => n,Playback(beep)
> 
> [test]
> 
> exten => 100,1,Answer()
>     same => n,Set(BEEP_ID=${PERIODIC_HOOK(hooks,beep,5)})
>     same => n,Wait(20)
>     same => n,Set(PERIODIC_HOOK(${BEEP_ID})=off)
>     same => n,Wait(20)
>     same => n,Set(PERIODIC_HOOK(${BEEP_ID})=on)
>     same => n,Wait(20)
>     same => n,Hangup()
> 
> 
> Thanks,
> 
> Russell Bryant
> 
>

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