STIR Ray. Singh Internet-Draft Vencore Labs Intended status: Standards Track Martin. Dolly Expires: December 8, 2017 AT&T Subir. Das Vencore Labs An. Nguyen Office of Emergency Communication/DHS June 06, 2017 PASSporT Extension for Resource-Priority Authorization draft-singh-stir-rph-00 Abstract This document extends the PASSporT object to convey cryptographically-signed assertions of authorization for communications 'Resource-Priority'. It extends PASSporT to allow cryptographic-signing of the SIP 'Resource-Priority" header field which is used for communications resource prioritization. It also describes how the PASSPorT extension is used in SIP signaling to convey assertions of authorization of the information in the SIP 'Resource-Priority' header field. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on December 8, 2017. Copyright Notice Copyright (c) 2017 IETF Trust and the persons identified as the document authors. All rights reserved. Singh, et al. Expires December 8, 2017 [Page 1] Internet-Draft PASSporT-ext June 2017 This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://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 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. PASSporT 'rph' Claim . . . . . . . . . . . . . . . . . . . . 3 4. 'rph' in SIP . . . . . . . . . . . . . . . . . . . . . . . . 4 4.1. Authentication Service Behavior . . . . . . . . . . . . . 4 4.2. Verification Service Behavior . . . . . . . . . . . . . . 5 5. Further Information Associated with Resource-Priority . . . . 6 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 6.1. JSON Web Token Claims Registration . . . . . . . . . . . 6 6.2. PASSporT RPH Types . . . . . . . . . . . . . . . . . . . 6 7. Security Considerations . . . . . . . . . . . . . . . . . . . 7 7.1. Avoidance of replay and cut and past attacks . . . . . . 7 7.2. Solution Considerations . . . . . . . . . . . . . . . . . 7 7.3. Acknowledgements . . . . . . . . . . . . . . . . . . . . 8 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 8.1. Normative References . . . . . . . . . . . . . . . . . . 8 8.2. Informative References . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 1. Introduction PASSporT [I-D.ietf-stir-passport] is a token format based on JWT [RFC7519] for conveying cryptographically-signed information about the identities involved in personal communications; it is used with STIR [I-D.ietf-stir-rfc4474bis] to convey a signed assertion of the identity of the participants in real-time communications established via a protocol like SIP. This specification extends PASSporT to allow cryptographic-signing of the SIP 'Resource-Priority' header field defined in [RFC4412]. [RFC4412] defines the SIP 'Resource-Priority' header field for communications Resource Priority. As specified in [RFC4412], the 'Resource-Priority' header field may be used by SIP user agents, including, Public Switched Telephone Network (PSTN) gateways and terminals, and SIP proxy servers to influence prioritization afforded to communication sessions,including PSTN calls. However, the SIP Singh, et al. Expires December 8, 2017 [Page 2] Internet-Draft PASSporT-ext June 2017 'Resource-Priority' header field could be spoofed and abused by unauthorized entities. The STIR architecture assumes that an authority on the originating side of a call provides a cryptographic assurance of the validity of the calling party number in order to prevent impersonation attacks. The STIR architecture allows extension that can be utilized by authorities supporting real-time communication services using the 'Resource-Priority' header field to cryptographically sign the SIP 'Resource-Priority' header field and convey assertion of the authorization for 'Resource-Priority'. For example, the authority on the originating side verifying the authorization of a particular communication for Resource-Priority can use a PASSPorT claim to cryptographically-sign the SIP 'Resource-Priority' header field and convey an assertion of the authorization for 'Resource-Priority'. This will allow a receiving entity (including entities located in different network domains/boundaries) to verify the validity of assertions authorizating Resource-Priority. Cryphographically-signed SIP 'Resource-Priority' headers will allow a receiving entity to verify and act on the information with confidence that the information have not been spoofed or compromised. This specification documents an optional extension to PASSporT and the associated STIR mechanisms to provide a function to sign the SIP 'Resource-Priority' header field. How the optional extension to PASSporT is used for real-time communications supported using SIP 'Resource-Priority' header field is defined in other documents and is outside the scope of this document. 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. 3. PASSporT 'rph' Claim This specification defines a new JSON Web Token claim for "rph", which provides an assertion for information in SIP 'Resource- Priority'header. The creator of a PASSporT object adds a "ppt" value of "rph" to the header of a PASSporT object, in which case the PASSporT claims MUST contain a "rph" claim, and any entities verifying the PASSporT object will be required to understand the "ppt" extension in order to process the PASSporT in question. A PASSPort header with the "ppt" included will look as follows: Singh, et al. Expires December 8, 2017 [Page 3] Internet-Draft PASSporT-ext June 2017 { "typ":"passport", "ppt":"rph", "alg":"ES256", "x5u":"https://www.example.org/cert.cer"} The "rph" claim will provide an assertion of authorization,"auth", for information in the SIP "Resource-Priority" header field (i.e., Resource-Priority: namespace "." r-priority) based on [RFC4412]. The value of the "rph" claim is an array containing one or more of JSON objects for the content of the SIP 'Resource-Priority' header that is being asserted of which one of the "rph" object, is mandatory. The following is an example "rph" claim for a SIP "Resource-Priority" header field with a "namespace "." r-priority" value of "ets.0". { "orig":{"tn":"12155551212"} "dest":{"tn":"12125551213"}, "iat":1443208345, "rph":{"auth":":"Resource-Priority: ets.0"}} After the header and claims PASSporT objects have been constructed, their signature is generated normally per the guidance in [I-D.ietf-stir-passport] using the full form of PASSPorT. The credentials (e.g., authority responsible for authorizating Resource- Priority) used to create the signature must have authority over the "rph" claim. 4. 'rph' in SIP This section specifies SIP-specific usage for the "rph" claim in PASSporT. 4.1. Authentication Service Behavior The Authentication Service will create the "rph" claim using the values discussed in section 3 based on [RFC4412]. The constrcution of "rph" claim follows the steps described in Section 4 of [I-D.ietf-stir-rfc4474bis]. The resulting Identity header for "rph" might look as follows: Singh, et al. Expires December 8, 2017 [Page 4] Internet-Draft PASSporT-ext June 2017 "eyJhbGciOiJFUzI1NiIsInR5cCI6IkpXVCJ9.eyJpc3MiOiJleUowZVhBaU9pSndZWE56Y0c5eW RDSXNEUW9pY0hCMElqb2ljbkJvSWl3TkNpSmhiR2NpT2lKRlV6STFOaUlzRFFvaWVEVjFJanBvZE hSd2N6b3ZMM2QzZHk1bGVHRnRjR3hsTG1OdmJTOWpaWEowTG1ObGNuME5DZz09LmV5SnZjbWxuSW pwN0luUnVJam9pTVRJeE5UVTFOVEV5TVRJaWZTd2dEUW9pYVdGMElqb2lNVFEwTXpJd09ETTBOU0 lzSUEwS0ltUmxjM1FpT25zaWRHNGlPaUl4TWpFMU5UVTFNVEl4TXlKOURRb2ljbkJvSWpwN0ltRj FkR2dpT2lKU1pYTnZkWEpqWlMxUWNtbHZjbWwwZVRvZ1pYUnpMakFpWFgxOURRb05DZzBLIiwibm JmIjoxNDk2NzU4Mzk0LCJleHAiOjE0OTY3NjE5OTQsImlhdCI6MTQ5Njc1ODM5NH0.0-oNMVgchp biDzSxCktUIQVbkJWL48DfxOTllSHBmj3sZtV2S3SKZkmnU2V9akv2LnJ50JK9W_1ynz7JrChJ3g"; info= "https://www.example.org/cert.cer";alg=ES256;ppt="rph" A SIP authentication service typically will derive the value of "rph" from the 'Resource-Priority' header field based on policy associated with service specific use of the "namespace "." r-priority" values based on [RFC4412]. The authentication service derives the value of the PASSPorT claim by verifying the authorization for Resource- Priority (i.e., verifying a calling user privilege for Resoure- Priority based on its identity) which mighth be derived from customer profile data or from access to external services. [RFC4412] allows multiple "namespace "." r-priority" pairs, either in a single SIP Resource-Priority header or across multiple SIP Resource-Priority headers. However, it is not necessary to sign all content of a SIP Resource-Priority header or all SIP Resource- Priority headers in a given SIP message. An authority is only responsible for signing the content of a SIP Resource-Priority header for which it has authority (e.g., a specific "namespace "." r-priority"). 4.2. Verification Service Behavior [I-D.ietf-stir-rfc4474bis] Section 6.2 Step 5 requires that specifications defining "ppt" values describe any additional verifier behavior. The behavior specified for the "ppt" values of "rph" is as follows: The verification service MUST extract the value associated with the "auth" key in a full form PASSPorT with a "ppt" value of "rph". If the signature validates, then the verification service can use the value of the "rph" claim as validation that the calling party is authorized for Resource-Priority, which would in turn be used for priority treatment in accordance with local policy for the associated communication service. The verification service MUST extract the value associated with the "auth" key in a full form PASSPorT with a "ppt" value of "rph". If the signature validates, then the verification service can use the value of the "rph" claim as validation that the calling party is authorized for Resource-Priority, which would in turn be used for Singh, et al. Expires December 8, 2017 [Page 5] Internet-Draft PASSporT-ext June 2017 priority treatment in accordance with local policy for the associated communication service. In addition, [I-D.ietf-stir-rfc4474bis] Section 6.2 Step 4 requires "iat" value in "rph" claim to be verified. The behavior of a SIP UAs upon receiving an INVITE containing a PASSporT object with a "rph" claim will largely remain a matter of implementation policy for the specific communication service. In most cases,implementations would act based on confidence in the veracity of this information. 5. Further Information Associated with Resource-Priority There may be additional information about the calling party or the call that could be relevant to authorization for Resource-Priority. This may include information related to the device subscription of the caller, or to any institutions that the caller or device is associated with, or even categories of institutions. All of these data elements would benefit from the secure attestations provided by the STIR and PASSporT frameworks. The specification of the "rph" claim could entail the optional presence of one or more such additional information fields. A new IANA registry has been defined to hold potential values of the "rph" array; see Section 8.3. Details of extensions to the "rph" claim to encompass other data elements are left for future version of this specification. 6. IANA Considerations 6.1. JSON Web Token Claims Registration o Claim Name: "rph" o Claim Description: Resource Priority Header o Change Controller: IESG o Specification Document(s): Section 3 of [RFCThis] 6.2. PASSporT RPH Types This document requests that the IANA create a new registry for PASSporT RPH types. Registration of new PASSporT RPH types shall be under the specification required policy. Singh, et al. Expires December 8, 2017 [Page 6] Internet-Draft PASSporT-ext June 2017 This registry is to be initially populated with a single value for "namespace" which is specified in [RFCThis]. 7. Security Considerations The security considerations discussed in [I-D.ietf-stir-rfc4474bis] in Section 10 are applicable here. 7.1. Avoidance of replay and cut and past attacks The PASSporT extension with a "ppt" value of "rph" MUST only be sent with SIP when 'Resource-Priority' header is used to convey the priority of the communication as defined in [RFC4412]. A uniqueness of the set of token with extension claims and token signature is constructed using the originating identity being asserted with the "orig" claim along with the following two claims: o "iat" claim should correspond to a date/time the message was originated. It should also be within a relative time that is reasonable for clock drift and transmission time characteristics associated with the application using the PASSporT token. Therefore, validation of the token should consider date and time correlation, which could be influenced by signaling protocol specific use and network time differences. o "dest" claim is included to prevent the valid re-use of a previously originated message to send to another destination party. 7.2. Solution Considerations The use of extension to PASSporT tokens with ppt value rph based on the validation of the digital signature and the associated certificate requires consideration of the authentication and authority or reputation of the signer to attest to the identity being asserted. The following considerations should be recognized when using PASSporT extension with "ppt" value of "rph": o The use of this token should not, in it's own right, be considered a full solution for absolute non-repudiation of the identity being asserted. o An authority (signer) is only allowed to sign the content of a SIP 'Resource-Priority' header for which it has the right authority. The authority that signs the token MUST have a secure method for authentication of the end user or the device. Singh, et al. Expires December 8, 2017 [Page 7] Internet-Draft PASSporT-ext June 2017 o The verification of the signature MUST include means of verifying that the signer is authoritative for the signed content of the SIP 'Resource-Priority' header. 7.3. Acknowledgements We would like to thank STIR members, ATIS/SIP Forum Task Force on IPNNI members, and the NS/EP Priority Services community for contributions to this problem statement and specification. We would also like to thank David Hancock for his valuable inputs. 8. References 8.1. Normative References [I-D.ietf-stir-passport] Wendt, C. and J. Peterson, "Personal Assertion Token (PASSporT)", February 2017. [I-D.ietf-stir-rfc4474bis] Peterson, J., Jennings, C., Rescorla, E., and C. Wendt, "Authenticated Identity Management in the Session Initiation Protocol (SIP)", February 2017. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC4412] Schulzrinne, H. and J. Polk, "Communications Resource Priority for the Session Initiation Protocol (SIP)", RFC 4412, DOI 10.17487/RFC4412, February 2006, . [RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015, . 8.2. Informative References [RFC3261] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, DOI 10.17487/RFC3261, June 2002, . Singh, et al. Expires December 8, 2017 [Page 8] Internet-Draft PASSporT-ext June 2017 [RFC6919] Barnes, R., Kent, S., and E. Rescorla, "Further Key Words for Use in RFCs to Indicate Requirement Levels", RFC 6919, DOI 10.17487/RFC6919, April 2013, . [RFC7340] Peterson, J., Schulzrinne, H., and H. Tschofenig, "Secure Telephone Identity Problem Statement and Requirements", RFC 7340, DOI 10.17487/RFC7340, September 2014, . Authors' Addresses Ray P. Singh Vencore Labs 150 Mount Airy Road New Jersey, NJ 07920 USA Email: rsingh@vencorelabs.com Martin Dolly AT&T 200 Laurel Avenue Middletown, NJ 07748 USA Email: md3135@att.com Subir Das Vencore Labs 150 Mount Airy Road New Jersey, NJ 07920 USA Email: sdas@vencorelabs.com An Nguyen Office of Emergency Communication/DHS 245 Murray Lane, Building 410 Washington, DC 20528 USA Email: an.p.nguyen@HQ.DHS.GOV Singh, et al. Expires December 8, 2017 [Page 9]