Secure Telephone Identity Revisited (STIR) Out-of-Band Architecture and Use Cases
RFC 8816
Document | Type |
RFC - Informational
(February 2021; No errata)
Was draft-ietf-stir-oob (stir WG)
|
|
---|---|---|---|
Authors | Eric Rescorla , Jon Peterson | ||
Last updated | 2021-02-11 | ||
Replaces | draft-rescorla-stir-fallback | ||
Stream | Internent Engineering Task Force (IETF) | ||
Formats | plain text html xml pdf htmlized (tools) htmlized bibtex | ||
Reviews | |||
Stream | WG state | Submitted to IESG for Publication | |
Document shepherd | Robert Sparks | ||
Shepherd write-up | Show (last changed 2019-07-11) | ||
IESG | IESG state | RFC 8816 (Informational) | |
Action Holders |
(None)
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||
Consensus Boilerplate | Yes | ||
Telechat date | |||
Responsible AD | Adam Roach | ||
Send notices to | Robert Sparks <rjsparks@nostrum.com> | ||
IANA | IANA review state | Version Changed - Review Needed | |
IANA action state | No IANA Actions |
Internet Engineering Task Force (IETF) E. Rescorla Request for Comments: 8816 Mozilla Category: Informational J. Peterson ISSN: 2070-1721 Neustar February 2021 Secure Telephone Identity Revisited (STIR) Out-of-Band Architecture and Use Cases Abstract The Personal Assertion Token (PASSporT) format defines a token that can be carried by signaling protocols, including SIP, to cryptographically attest the identity of callers. However, not all telephone calls use Internet signaling protocols, and some calls use them for only part of their signaling path, while some cannot reliably deliver SIP header fields end-to-end. This document describes use cases that require the delivery of PASSporT objects outside of the signaling path, and defines architectures and semantics to provide this functionality. Status of This Memo This document is not an Internet Standards Track specification; it is published for informational purposes. This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Not all documents approved by the IESG are candidates for any level of Internet Standard; see Section 2 of RFC 7841. Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at https://www.rfc-editor.org/info/rfc8816. Copyright Notice Copyright (c) 2021 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction 2. Terminology 3. Operating Environments 4. Dataflows 5. Use Cases 5.1. Case 1: VoIP to PSTN Call 5.2. Case 2: Two Smart PSTN Endpoints 5.3. Case 3: PSTN to VoIP Call 5.4. Case 4: Gateway Out-of-Band 5.5. Case 5: Enterprise Call Center 6. Storing and Retrieving PASSporTs 6.1. Storage 6.2. Retrieval 7. Solution Architecture 7.1. Credentials and Phone Numbers 7.2. Call Flow 7.3. Security Analysis 7.4. Substitution Attacks 7.5. Rate Control for CPS Storage 8. Authentication and Verification Service Behavior for Out-of-Band 8.1. Authentication Service (AS) 8.2. Verification Service (VS) 8.3. Gateway Placement Services 9. Example HTTPS Interface to the CPS 10. CPS Discovery 11. Encryption Key Lookup 12. IANA Considerations 13. Privacy Considerations 14. Security Considerations 15. Informative References Acknowledgments Authors' Addresses 1. Introduction The STIR problem statement [RFC7340] describes widespread problems enabled by impersonation in the telephone network, including illegal robocalling, voicemail hacking, and swatting. As telephone services are increasingly migrating onto the Internet, and using Voice over IP (VoIP) protocols such as SIP [RFC3261], it is necessary for these protocols to support stronger identity mechanisms to prevent impersonation. For example, [RFC8224] defines a SIP Identity header field capable of carrying PASSporT objects [RFC8225] in SIP as a means to cryptographically attest that the originator of a telephone call is authorized to use the calling party number (or, for native SIP cases, SIP URI) associated with the originator of the call. Not all telephone calls use SIP today, however, and even those that do use SIP do not always carry SIP signaling end-to-end. Calls from telephone numbers still routinely traverse the Public Switched Telephone Network (PSTN) at some point. Broadly, calls fall into one of three categories: 1. One or both of the endpoints is actually a PSTN endpoint. 2. Both of the endpoints are non-PSTN (SIP, Jingle, etc.) but the call transits the PSTN at some point. 3. Non-PSTN calls that do not transit the PSTN at all (such as native SIP end-to-end calls). The first two categories represent the majority of telephone calls associated with problems like illegal robocalling: many robocallsShow full document text