On Wed, 2009-04-29 at 12:56 -0400, Paul Mossman wrote:
> Hi all,
> 
> Alert-Info headers are used by both the Page and Intercom features to
> trigger certain phone types to auto-answer INVITEs.  In the case of
> Polycoms, the phone must be pre-configured with the an Alert-Info string
> for the feature.
> 
> It seems there may be a good reason to keep this string secret, since it
> can be used to cause phones to auto-answer a call.  You don't want
> hackers to be able to do this.  Though, hopefully sipXproxy rejects (or
> amends) unauthorized INVITEs that contain an Alert-Info header...
> 
> I ask because the Page and Intercom Alert-Info strings are treated
> inconsistently in this respect.
> 
> The Page Alert-Info string is hard-coded to "sipXpage".  Also, the
> Polycom profile generation is hard-coded with configuration to
> auto-answer at this Alert-Info string.  It's always there, regardless of
> whether any page groups are defined or not.
> 
> The Intercom Alert-Info string on the other hand is a randomly generated
> string, such as "A0mJkSQI".  Furthermore it is only put into generated
> profiles when the Polycom is a member of a phone group for which
> Intercom is enabled.  If you enable the Intercom feature, then you need
> to push the Polycom profiles for it to take effect.  (sipXconfig tells
> you about the services that need to be restarted, but not about the
> phone profiles that need to be re-generated.)
> 
> It seems like if there's no need to keep the strings secret, then
> Intercom should use a hard-coded one so that phone configuration doesn't
> need to be updated.  But if the strings should be kept secret then I
> don't see the point in hiding one but not the other.
> 
> Is there a reason for the Page and Intercom Alert-Info strings to be
> handled so differently?  Thanks.

No, but there's also no point in attempting to keep 'secret' anything
that's sent over the wire in cleartext.

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