On Wed, 2010-01-13 at 15:31 -0500, Robert Joly wrote:
> 
> The issue with the set-based call forwarding is as follows:   

> Suppose that A calls B and B and does set-based call forwarding to C.
> In that scenario, what sipXecs ultimately see is A calling C and that
> call will be successful only if A has the permission to call C.  In
> your specific case, that lack of permission is what is causing the
> failure.  

Internally, the problem is this: set based forwarding is a SIP response
from the set to the proxy.  The set sends a "302 Redirect" response with
a Contact header that has whatever the forwarding destination is.  But
that 302 is not authenticated - the proxy doesn't have any secure way of
knowing that the response was not forged (the simplest way of doing that
is to walk up to an unwatched phone and set the forwarding).  

By doing the forwarding control inside sipXecs, we ensure make it much
more secure.


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