Last Call Review of draft-ietf-sipcore-status-unwanted-04
review-ietf-sipcore-status-unwanted-04-secdir-lc-montville-2017-03-15-00

I have reviewed this document as part of the security directorate's ongoing
effort to review all IETF documents being processed by the IESG.  These
comments were written primarily for the benefit of the security area
directors.  Document editors and WG chairs should treat these comments just
like any other last call comments.

This draft is ready with (possible) issues.

This draft defines a new SIP response code, 666 "Unwanted", which allows
called parties to indicate when a call is unwanted.  The intent of the
Unwanted response code is to provide feedback to global or user-specific
filtering algorithms (implemented by carriers) from the context of a
SIP-initiated call.

>From a security perspective, there's nothing wrong with the draft, and the
Security Considerations section addresses what one might expect (denial of
service, relying on the code only when authenticated caller identities are
in play, etc.)  It seems that the biggest risk is false blocks, callers
having their feelings hurt, or folks not getting the calls they may expect
-- but implementers are made aware of these.

A potential issue can be seen by taking these two sentences together:
"Implementations will have to make appropriate trade-offs between falsely
labeling a caller as unwanted and delivering unwanted calls", "The service
provider...MAY report the calling party identity to government
authorities".  This gives rise to the possibility that a mislabeled caller
could be reported to authorities, when there is no real reason for such.

Either way, I found the document to be clear and well-written.  And while I
list the draft as "ready with issues" here, it may be the case that there
are no issues from the perspective of the ADs for whom I have performed
this review.

Kind regards,

Adam