Network Working Group M. Barnes Internet-Draft iconectiv Intended status: Informational C. Wendt Expires: May 3, 2018 Comcast October 30, 2017 ACME Identifiers and Challenges for VoIP Service Providers draft-barnes-acme-service-provider-code-00 Abstract This document describes the use of the Entity Code Identifier and token challenge type to enable the Automated Certificate Management Environment (ACME) to issue certificates for VoIP service providers to support Secure Telephony Identity (STI). 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 https://datatracker.ietf.org/drafts/current/. 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Barnes & Wendt Expires May 3, 2018 [Page 1] Internet-Draft Service Provider Identifiers and Challenges October 2017 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 2 3. Using Service Provider Codes for Token Authorization . . . . 3 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 6. Informative References . . . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction [I-D.ietf-acme-acme] is a mechanism for automating certificate management on the Internet. It enables administrative entities to prove effective control over resources like domain names, and automates the process of generating and issuing certificates. [I- D.barnes-acme-token-challenge] defines a new Identifier type (Entity Code) and new challenge type based on a token (Entity Code Token) for authorizing entities to request certificates. The model includes an administrative authority that allocates the entity codes and creates the service provider code tokens for the entities. This specification defines the use of the Entity Code Identifier and Entity Code Token to enable certification authorities to issue certificates based on service provider codes and related tokens. 2. Overview The document [ATIS-1000080] provides a framework and model for using certificates based on service provider codes. In this model, each service provider requires only a few certificates, which are used in conjunction with a PASSporT that contains additional information attesting to a service provider's knowledge of the originator of the call. Further details on the PASSporT extensions for this model are provided in the SHAKEN Framework [ATIS-1000074]. In the SHAKEN Certificate Management framework [ATIS-1000080], there is an administrative entity that is responsible for allocating service provider codes. This is referred to as the STI Policy Administrator (STI-PA). This allows a certification authority to validate that the entity requesting issuance of a certificate is authorized to request certificates on behalf of the entity that has been assigned a specific service provider code. A single VoIP service provider can be allocated multiple service provider codes. A service provider can choose to use the same certificate for multiple service providers as reflected by the structure of the TN Authorization List certificate extension defined in [I-D.ietf-stir-certificates]. Barnes & Wendt Expires May 3, 2018 [Page 2] Internet-Draft Service Provider Identifiers and Challenges October 2017 The intent of the challenges in this document is not to establish that an entity is a valid service provider but rather to provide evidence that an established administrative authority entity has authorized the entity to provide VoIP services in the network and thus to request credentials on behalf of the VoIP users in the network. 3. Using Service Provider Codes for Token Authorization In order to issue certificates for service providers based on service provider code values, the Entity Code ACME identifier type is used in the ACME authorization objects. The value is set to the value of the service provider code. The ACME challenge type of "ec-token-01" is used to support the authorization of service provider code tokens. The following is the response that the ACME client receives when it sends a GET for the challenges in the case of a "EntityCode" identifer: HTTP/1.1 200 OK Content-Type: application/json Link: ;rel="directory" { "status": "pending", "identifier": { "type": "EntityCode", "value": ["1234-0111"] }, "challenges": [ { "type": "ec-token-01", "url": "https://sti-ca.com/authz/asdf/0" "token": "DGyRejmCefe7v4NfDGDKfA" } ], } A client responds to this challenge by using the service provider code token for the "ec-token" value. In the SHAKEN Certificate Management framework, the Service Provider has a secure exchange with the STI-PA to obtain a service provider code token that can be used for authorization by the CA when requesting a certificate. The service provider code token is a standard JWT token [RFC7519] using a JWS defined signature string [RFC7515]. It is RECOMMENDED that the lifetime of the service provider code token be greater than the certificate lifetime, in particular in cases where multiple Barnes & Wendt Expires May 3, 2018 [Page 3] Internet-Draft Service Provider Identifiers and Challenges October 2017 certificates are being issued using the same service provider code token. The entity code token JWT Protected Header to support service provider code tokens MUST include the following: alg: Defines the algorithm used in the signature of the token. For Service Provider Code tokens, the algorithm MUST be "ES256". typ: Set to standard "JWT" value. x5u: Defines the URL of the certificate of the STI-PA validating the Service Provider Code. The service provide code token JWT Payload MUST include the following: sub: Service Provider Code value being validated in the form of an ASCII string. iat: DateTime value of the time and date the token was issued. nbf: DateTime value of the starting time and date that the token is valid. exp: DateTime value of the ending time and date that the token expires. fingerprint: : Fingerprint of the ACME credentials the Service Provider used to create an account with the CA. The fingerprint is of the form: base64url(JWK_Thumbprint(accountKey)). The "JWK_Thumbprint" step indicates the computation specified in [RFC7638], using the SHA-256 digest [FIPS180-4]. As noted in JWA [RFC7518] any prepended zero octets in the JWK object MUST be stripped before doing the computation. To respond to a service provider code token challenge, the ACME client constructs an entity code authorization ("ec-authz") using the "token" value provided in the challenge and the service provider code token, that has been previously obtained from the STI-PA, as the "ecAuthzToken" value. Barnes & Wendt Expires May 3, 2018 [Page 4] Internet-Draft Service Provider Identifiers and Challenges October 2017 An example of the use of the "ec-token-01" in a challenge response sent by the ACME client is provided below: POST /acme/authz/asdf/0 HTTP/1.1 Host: sti-ca.com Content-Type: application/jose+json { "protected": base64url({ "alg": "ES256", "kid": "https://sti-ca.com/acme/reg/asdf", "nonce": "Q_s3MWoqT05TrdkM2MTDcw", "url": "https://sti-ca.com/acme/authz/asdf/0" }), "payload": base64url({ "ecAuthorization": "DGyRejmCefe7v4N...vb29HhjjLPSggwiE" }), "signature": "9cbg5JO1Gf5YLjjz...SpkUfcdPai9uVYYQ" } Upon receiving a response to the challenge, the ACME server determines the validity of the response as described in [I-D.barnes- acme-token-challenge]. 4. IANA Considerations This document requires no IANA registrations. 5. Security Considerations This document relies on the security considerations established for the ACME protocol per [I-D.ietf-acme-acme]. The service provider code token is initially obtained through a secure exchange between the service provider and the entity in the network that is responsible for determining what entities can operate as VoIP service providers (the STI Policy Administrator). Further details on this are provided in [ATIS-1000080]. 6. Informative References [ATIS-1000074] ATIS/SIP Forum NNI Task Group, "Signature-based Handling of Asserted information using toKENs (SHAKEN)", January 2017. Barnes & Wendt Expires May 3, 2018 [Page 5] Internet-Draft Service Provider Identifiers and Challenges October 2017 [ATIS-1000080] ATIS/SIP Forum NNI Task Group, "Signature-based Handling of Asserted information using toKENs (SHAKEN): Governance Model and Certificate Management", May 2017. [FIPS180-4] Department of Commerce, National, "NIST FIPS 180-4, Secure Hash Standard", March 2012. [I-D.ietf-acme-acme] Barnes, R., Hoffman-Andrews, J., and J. Kasten, "Automatic Certificate Management Environment (ACME)", draft-ietf- acme-acme-07 (work in progress), June 2017. [I-D.ietf-acme-telephone] Peterson, J. and R. Barnes, "ACME Identifiers and Challenges for Telephone Numbers", draft-ietf-acme- telephone-00 (work in progress), July 2017. [I-D.ietf-stir-certificates] Peterson, J. and S. Turner, "Secure Telephone Identity Credentials: Certificates", draft-ietf-stir- certificates-14 (work in progress), May 2017. [I-D.ietf-stir-passport] Wendt, C. and J. Peterson, "Personal Assertion Token (PASSporT)", draft-ietf-stir-passport-11 (work in progress), 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)", draft-ietf-stir-rfc4474bis-16 (work in progress), February 2017. [RFC7340] Peterson, J., Schulzrinne, H., and H. Tschofenig, "Secure Telephone Identity Problem Statement and Requirements", RFC 7340, DOI 10.17487/RFC7340, September 2014, . [RFC7515] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Signature (JWS)", RFC 7515, DOI 10.17487/RFC7515, May 2015, . [RFC7518] Jones, M., "JSON Web Algorithms (JWA)", RFC 7518, DOI 10.17487/RFC7518, May 2015, . Barnes & Wendt Expires May 3, 2018 [Page 6] Internet-Draft Service Provider Identifiers and Challenges October 2017 [RFC7519] Jones, M., Bradley, J., and N. Sakimura, "JSON Web Token (JWT)", RFC 7519, DOI 10.17487/RFC7519, May 2015, . [RFC7638] Jones, M. and N. Sakimura, "JSON Web Key (JWK) Thumbprint", RFC 7638, DOI 10.17487/RFC7638, September 2015, . Authors' Addresses Mary Barnes iconectiv Email: mary.ietf.barnes@gmail.com Chris Wendt Comcast One Comcast Center Philadelphia, PA 19103 US Email: chris-ietf@chriswendt.net Barnes & Wendt Expires May 3, 2018 [Page 7]