SIP WG V. Gurbani Internet-Draft Bell Laboratories, Alcatel-Lucent Updates: rfc3261 S. Lawrence (if approved) Bluesocket Inc. Intended status: Standards Track A. Jeffrey Expires: January 15, 2009 Bell Laboratories, Alcatel-Lucent July 14, 2008 Domain Certificates in the Session Initiation Protocol (SIP) draft-ietf-sip-domain-certs-01 Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on January 15, 2009. Copyright Notice Copyright (C) The IETF Trust (2008). Abstract This document describes how to interpret certain information in a X.509 PKIX-compliant certificate used in a Session Initiation Protocol (SIP) over Transport Layer Security (TLS) connection. More specifically, it describes how to find the right identity for authentication in such certificates and how to use it for SIP domain Gurbani, et al. Expires January 15, 2009 [Page 1]
Internet-Draft Domain Certs July 2008 authentication. Table of Contents 1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Key Words . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Problem statement . . . . . . . . . . . . . . . . . . . . . . 3 4. SIP domain to host resolution . . . . . . . . . . . . . . . . 5 5. The need for mutual interdomain authentication . . . . . . . . 6 6. Guidelines for a SIP service provider . . . . . . . . . . . . 7 7. Behavior of SIP entities . . . . . . . . . . . . . . . . . . . 7 7.1. Finding SIP Identities in a Certificate . . . . . . . . . 8 7.2. Comparing SIP Identities . . . . . . . . . . . . . . . . . 9 7.3. Client behavior . . . . . . . . . . . . . . . . . . . . . 9 7.4. Server behavior . . . . . . . . . . . . . . . . . . . . . 10 7.5. Proxy behavior . . . . . . . . . . . . . . . . . . . . . . 11 7.6. Registrar behavior . . . . . . . . . . . . . . . . . . . . 11 7.7. Redirect server behavior . . . . . . . . . . . . . . . . . 11 7.8. Virtual SIP Servers and Certificate Content . . . . . . . 11 8. Security Considerations . . . . . . . . . . . . . . . . . . . 12 8.1. Connection authentication using Digest . . . . . . . . . . 13 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 13 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 11.1. Normative References . . . . . . . . . . . . . . . . . . . 13 11.2. Informative References . . . . . . . . . . . . . . . . . . 14 Appendix A. Editorial guidance (non-normative) . . . . . . . . . 14 A.1. Additions . . . . . . . . . . . . . . . . . . . . . . . . 15 A.2. Changes . . . . . . . . . . . . . . . . . . . . . . . . . 15 A.2.1. 26.3.1 . . . . . . . . . . . . . . . . . . . . . . . . 15 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15 Intellectual Property and Copyright Statements . . . . . . . . . . 17 Gurbani, et al. Expires January 15, 2009 [Page 2]
Internet-Draft Domain Certs July 2008 1. Terminology 1.1. Key Words 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 [1]. Additional definition(s): SIP domain identity: An identity (e.g., "sip:example.com") contained in an X.509 certificate bound to a subject that identifies the subject as an authoritative SIP server for a domain. 2. Introduction Transport Layer Security (TLS) [3] has started to appear in an increasing number of Session Initiation Protocol (SIP) [2] implementations. In order to use the authentication capabilities of TLS, certificates as defined by the Internet X.509 Public Key Infrastructure RFC 5280 [4] are required. Existing SIP specifications do not sufficiently specify how to use certificates for domain (as opposed to host) authentication. This document provides guidance to ensure interoperability and uniform conventions for the construction and interpretation of certificates used to identify their holders as being authoritative for the domain. The discussion in this document is pertinent to an X.509 PKIX- compliant certificate used for a TLS connection; it may not apply to use of such certificates with S/MIME, for instance. 3. Problem statement TLS uses X.509 Public Key Infrastructure [4] to bind an identity or a set of identities, to the subject of a X.509 certificate. Accordingly, the recommendations of the SIP working group have been to populate the X.509v3 Subject Alternative Names (subjectAltName, or SAN) extension with an identity. While RFC3261 provides adequate guidance on the use of X.509 certificates used for S/MIME, it is relatively silent on the use of such certificates for TLS. The concept of what should be contained in a site (or domain) certificate in RFC3261 is quoted below (Section 26.3.1): Gurbani, et al. Expires January 15, 2009 [Page 3]
Internet-Draft Domain Certs July 2008 Proxy servers, redirect servers and registrars SHOULD possess a site certificate whose subject corresponds to their canonical hostname. The security properties of TLS and S/MIME as used in SIP are different: X.509 certificates for S/MIME are generally used for end- to-end authentication and encryption, thus they serve to bind the identity of a user to the certificate and RFC3261 is sufficiently clear that in certificates used for S/MIME, the subjectAltName field will contain the appropriate identity. On the other hand, X.509 certificates used for TLS serve to bind the identities of the per-hop domain sending or receiving the SIP messages. However, the lack of guidelines in RFC3261 on exactly where to put identities -- in the subjectAltName field or carried as a Common Name (CN) in the Subject field -- of a X.509 certificates created ambiguities. Following the accepted practice of the time, legacy X.509 certificates were allowed to store the identity in the CN field of the certificate instead of the currently specified subjectAltName extension. Lack of further guidelines on how to interpret the identities, which identity to choose if more than one identity is present in the certificate, the behavior when multiple identities with different schemes were present in the certificate, etc. lead to ambiguities when attempting to interpret the certificate in a uniform manner for TLS use. This document shows how the certificates are to be used for mutual authentication when both the client and server possess appropriate certificates. It also contains normative behavior for matching the DNS query string with an identity stored in the X.509 certificate. Furthermore, it is permissible for a certificate to contain multiple identities for the subject in the subjectAltName extension (the "subject" of a certificate identifies the entity associated with the public key stored in the public key field.) As such, this document specifies appropriate matching rules to encompass various subject identity representation options. And finally, this document also provides guidelines to service providers for assigning certificates to SIP servers. The rest of this document is organized as follows: the next section provides an overview of the most primitive case of a client using DNS to access a SIP server and the resulting authentication steps. Section 5 looks at the reason why mutual inter-domain authentication is desired in SIP, and the lack of normative text and behavior in RFC3261 for doing so. Section 6 outlines normative guidelines for a service provider when it is assigning certificates to SIP servers. Section 7 provides normative behavior on the SIP entities (user agent clients, user agent servers, registrars, redirect servers, and proxies) that need perform authentication based on X.509 certificates. Section 8 includes the security considerations. Gurbani, et al. Expires January 15, 2009 [Page 4]
Internet-Draft Domain Certs July 2008 4. SIP domain to host resolution Routing in SIP is performed by having the client execute RFC 3263 [6] procedures on a URI, called the "Application Unique String (AUS) (c.f. Section 8 of RFC 3263 [6]). These procedures take as input a SIP AUS (the SIP domain) and return an ordered set containing one or more IP addresses, and a port number and transport corresponding to each IP address in the set (the "Expected Output") by querying an Domain Name Service (DNS). If the transport indicates the use of TLS, then a TLS connection is opened to the server on a specific IP address and port. The server presents an X.509 certificate to the client for verification as part of the initial TLS handshake. The client should extract identifiers from the Subject and subjectAltName extension in the certificate (see Section 7.1) and compare these values to the AUS. If any identifier match is found, the server is considered to be authenticated and subsequent signaling can now proceed over the TLS connection. Matching rules for X.509 certificates and the normative behavior for clients is specified in Section 7.3. As an example, consider a request that is to be routed to the SIP address "sips:alice@example.com". This address requires a secure connection to the SIP domain "example.com", which is taken to be the SIP AUS value. Through a series of DNS manipulations, the AUS is mapped to a set of host addresses and transports. From this set, an address appropriate for use with TLS is selected. A connection is subsequently established to that server, which presents a certificate asserting an identity of "sip:example.com". Since the host portion of the SIP AUS matches the subject of the certificate, the server is considered to be authenticated. SIPS borrows this behavior from HTTPS. However, to be pedantic, RFC 2818 [7] prefers that the identity be conveyed as a subjectAltName extension of type dNSName instead of the commonly used practice of conveying the identity in the CN field of the Subject field. Similarly, this document RECOMMENDS that the SIP domain identity be conveyed as a subjectAltName extension of type uniformResourceIdentifier (c.f. Section 6, Section 7.1). A domain name in an X.509 certificates is properly interpreted only as a sequence of octets to be compared to the URI used to reach the host. No inference should be made based on the DNS name hierarchy. Gurbani, et al. Expires January 15, 2009 [Page 5]
Internet-Draft Domain Certs July 2008 5. The need for mutual interdomain authentication Consider the SIP trapezoid shown in Figure 1. Proxy-A.example.com Proxy-B.example.net +-------+ +-------+ | Proxy |--------------------| Proxy | +----+--+ +---+---+ | | | | | | | +---+ 0---0 | | /-\ |___| +---+ / / +----+ alice@example.com bob@example.net Figure 1: SIP Trapezoid An user, alice@example.com, invites bob@example.net for a multimedia communication session. Alice's outbound proxy, Proxy-A.example.com, uses normal RFC 3263 [6] resolution rules to find a proxy -- Proxy- B.example.net -- in the example.net domain that uses TLS. Proxy-A actively establishes an interdomain TLS connection with Proxy-B and each presents a certificate to authenticate that connection. RFC 3261 [2] section 26.3.2.2 "Interdomain Requests" states that when a TLS connection is created between two proxies, mutual TLS authentication should follow whereby Each side of the connection SHOULD verify and inspect the certificate of the other, noting the domain name that appears in the certificate for comparison with the header fields of SIP messages. However, RFC3261 is silent on where in the certificate should the domain name be retrieved from (SAN or CN?) and which name takes precedence when there are multiple names identifying the holder of the certificate. The authentication problem for Proxy-A is straightforward: assuming a secure DNS infrastructure and no routing attacks, Proxy-A already knows that Proxy-B is a valid proxy for the example.net domain. Thus, in the certificate it receives from Proxy-B, Proxy-A should look for the host name ("Proxy-B.example.net") or an identity Gurbani, et al. Expires January 15, 2009 [Page 6]
Internet-Draft Domain Certs July 2008 consisting of a SIP URI ("sip:example.net") that asserts Proxy-B's authority over the example.net domain. Normative behavior for a TLS client like Proxy-A is specified in Section 7.3. The problem for Proxy-B is slightly more complex since it accepted the TLS request passively. Thus, it does not possess an equivalent AUS that it can use as an anchor in matching identities from Proxy-A's certificate. RFC 3261 [2] section 26.3.2.2 only exhorts Proxy-B to "compare the domain asserted by the certificate with the 'domainname' portion of the From header field in the INVITE request." The difficulty with this approach is that it is not always the case that the domainname in From corresponds to the domain from which the request is being received. The normative behavior for a TLS server like Proxy-B that passively accept TLS connections and requires authentication of the sending peer is provided in Section 7.4. 6. Guidelines for a SIP service provider Service providers MAY continue the practice of using existing certificates for SIP usage with the identity conveyed in the Subject field; however, such usage is NOT RECOMMENDED for new certificates, which MUST contain the identity or identities in the subjectAltName extension field. When assigning certificates to proxy servers, registrars, and redirect servers, a SIP service provider MUST ensure that the SIP AUS used to reach the server appears as an identity in the subjectAltName field, or for compatibility with existing certificates, the Subject field of the certificate. In practice, this means that a service provider distributes to its users SIP URIs whose domain portion corresponds to an identity for which the service provider has been issued a certificate. 7. Behavior of SIP entities This section normatively specifies the behavior of SIP entities when using X.509 certificates to determine an authenticated SIP domain identity. Gurbani, et al. Expires January 15, 2009 [Page 7]
Internet-Draft Domain Certs July 2008 7.1. Finding SIP Identities in a Certificate Procedures for constructing a certificate path and checking revocation status to determine the validity of a certificate are described in RFC 5280 [4]; implementations MUST follow checks as prescribed therein. This document adds additional rules for interpreting an X.509 certificate for use in SIP. The SIP Extended Key Usage (EKU) document [5] describes the method to validate EKU values found in the certificate used for SIP. If a certificate has a SIP EKU value specified, implementations MUST perform the checks prescribed by that specification. Given an X.509 certificate that the above checks have found to be acceptable, the following describes how to determine what SIP domain identity or identities it contains. Note that a single certificate MAY serve more than one purpose - that is, it MAY contain identities not valid for use in SIP, and/or MAY contain one or more identities that are valid for use in SIP. 1. Examine the values in the subjectAltName field. The contents of subjectAltName field and the constraints that may be imposed on them are defined in Section 4.2.1.6 of RFC 5280 [4]. The subjectAltName field may not be present or it may contain one or more identities. Each value in the subjectAltName has a type; the only types acceptable for encoding a SIP domain identity are: URI If the scheme of the URI value is "sip" (URI scheme tokens are always case insensitive), and there is no userinfo component in the URI (there is no '@'), then the hostpart is a SIP domain identity. A URI value that does contain a userpart MUST NOT be used as a domain identity (such a certificate identifies an individual user, not a server for the domain). If the scheme of the URI is not "sip", then the identity corresponding to that scheme MUST NOT be used as a SIP domain identity. DNS A domain name system identifier MUST be accepted as a SIP domain identity if and only if no other identity is found that matches the "sip" URI type described above. 2. If and only if the subjectAltName does not appear in the certificate, the client MAY examine the CN field of the certificate. If a valid DNS name is found there, the implementation MAY use this value as a SIP domain identity. The use of the CN value is allowed for backward compatibility, but is NOT RECOMMENDED. Service providers who are applying for new Gurbani, et al. Expires January 15, 2009 [Page 8]
Internet-Draft Domain Certs July 2008 X.509 certificates to be used with SIP SHOULD follow the guidelines of Section 6. The above procedure yields a set containing zero or more identities from the certificate. A client uses these identities to authenticate a server (see Section 7.3) and a server uses them to authenticate a client (see Section 7.4). 7.2. Comparing SIP Identities When comparing two values as SIP domain identities: Implementations MUST compare only that part of each identifier (from the procedure defined in Section 7.1) that is a DNS name. Any scheme or parameters extracted from an identifier MUST NOT be used in the comparison procedure described below. The values MUST be compared as DNS names, which means that the comparison is case insensitive. Internationalized Domain Names (IDNs) must be handled in accordance with Section 7.2 of RFC 5280 [4]. The match MUST be exact: A suffix match MUST NOT be considered a match. For example, "foo.example.com" does not match "example.com". Any form of wildcard, such as a leading "." or "*.", MUST NOT be considered a match. For example, "foo.example.com" does not match ".example.com" or "*.example.com". RFC 2818 (HTTP over TLS) [7] allows the dNSName component to contain a wildcard; e.g., "DNS:*.example.com". RFC 5280 [4], while not disallowing this explicitly, leaves the interpretation of wildcards to the individual specification. RFC 3261 [2] does not provide any guidelines on the presence of wildcards in certificates. This document reflects the consensus from the working group to not allow such wildcards. 7.3. Client behavior A client uses the domain portion of the SIP AUS to query a (possibly untrusted) DNS to obtain a result set, which is one or more SRV and A records identifying the server for the domain (see Section 4 for an overview.) The SIP server, when establishing a TLS connection, presents its Gurbani, et al. Expires January 15, 2009 [Page 9]
Internet-Draft Domain Certs July 2008 certificate to the client for authentication. The client MUST determine the SIP domain identities in the server certificate using the procedure in Section 7.1. Then, the client MUST compare the original domain portion of the SIP AUS used as input to the server location procedures [6] to the SIP domain identities obtained from the certificate. o If there were no identities found in the server certificate, the server is not authenticated. o If the AUS matches any SIP domain identity obtained from the certificate when compared as described in section Section 7.2, the server is authenticated for the domain. If the server is not authenticated, the client MUST close the connection immediately. 7.4. Server behavior When a server accepts a TLS connection, it presents its own X.509 certificate to the client. To authenticate the client, the server asks the client for a certificate. If the client possesses a certificate, it is presented to the server. If the client does not present a certificate, it MUST NOT be considered authenticated. Whether or not to close a connection if the client cannot present a certificate is a matter of local policy, and depends on the authentication needs of the server for the connection. Some currently deployed servers use Digest authentication to authenticate individual requests on the connection, and choose to treat the connection as authenticated by those requests for some purposes (but see Section 8.1). If the server requires client authentication for some local purpose, then it MAY implement a policy of allowing the connection only if the client is authenticated. For example, if the server is an inbound proxy that has peering relationships with the outbound proxies of other specific domains, it might only allow connections authenticated as coming from those domains. The server MUST obtain the set of SIP domain identities from the client certificate as described in Section 7.1. Because the server accepted the TLS connection passively, unlike a client, it does not possess an AUS for comparison. Nonetheless, server policies can use the set of SIP domain identities gathered from the certificate in Section 7.1 to make authorization decisions. For example, a very open policy could be to accept a X.509 Gurbani, et al. Expires January 15, 2009 [Page 10]
Internet-Draft Domain Certs July 2008 certificate and validate it using the procedures in RFC 5280 [4]. If the certificate is valid, the identity set is logged. Alternatively, the server could have a list of all SIP domains it is allowed to accept connections from; when a client presents its certificate, for each identity in the client certificate, the server searches for it in the list of acceptable domains to decide whether or not to accept the connection. Other policies that make finer distinctions are possible. Note that the decision of whether or not the authenticated connection to the client is appropriate for use to route new requests to the client domain is independent of whether or not the connection is authenticated; the connect-reuse [10] draft discusses this aspect in more detail. 7.5. Proxy behavior A proxy MUST use the procedures defined for a User Agent Server (UAS) in Section 7.4 when authenticating a connection from a client. A proxy MUST use the procedures defined for a User Agent Client (UAC) in Section 7.3 when requesting an authenticated connection to a UAS. If a proxy adds a Record-Route when forwarding a request with the expectation that the route is to use secure connections, it MUST insert into the Record-Route header a URI that corresponds to an identity for which it has a certificate; if it does not, then it will not be possible to create a secure connection using the value from the Record-Route as the AUS. 7.6. Registrar behavior A SIP registrar, acting as a server, follows the normative behavior of Section 7.4. When it accepts a TLS connection from the client, it present its certificate. Depending on the registrar policies, it may challenge the client with HTTP Digest. 7.7. Redirect server behavior A SIP redirect server follows the normative behavior of Section 7.4. When it accepts a TLS connection from the client, it present its certificate. Depending on the server policies, it may challenge the client with HTTP Digest. 7.8. Virtual SIP Servers and Certificate Content In the "virtual hosting" cases where multiple domains are managed by a single application, a certificate may contain multiple subjects by Gurbani, et al. Expires January 15, 2009 [Page 11]
Internet-Draft Domain Certs July 2008 having distinct identities in the subjectAltName field [9]. Clients seeking to authenticate a server on such a virtual host can still follow the directions in Section 7.3 to find the identity matching the SIP AUS used to query DNS. Alternatively, if the TLS client hello extension [8] is supported, the client SHOULD use it to request a certificate corresponding to the specific domain (the SIP AUS) that the client is seeking to establish a connection with. 8. Security Considerations The goals of TLS (when used with X.509 certificates) include the following security guarantees at the transport layer: Confidentiality: packets tunneled through TLS can be read only by the sender and receiver. Integrity: packets tunneled through TLS cannot be undetectably modified on the connection between the sender and receiver. Authentication: each principal is authenticated to the other as possessing a private key for which a certificate has been issued. Moreover, this certificate has not been revoked, and is verifiable by a certificate chain leading to a (locally configured) trust anchor. We expect appropriate processing of domain certificates to provide the following security guarantees at the application level: Confidentiality: SIPS messages from alice@example.com to bob@example.net can be read only by alice@example.com, bob@example.net, and SIP proxies issued with domain certificates for example.com or example.net. Integrity: SIPS messages from alice@example.com to bob@example.net cannot be undetectably modified on the links between alice@example.com, bob@example.net, and SIP proxies issued with domain certificates for example.com or example.net. Authentication: alice@example.com and proxy.example.com are mutually authenticated; moreover proxy.example.com is authenticated to alice@example.com as an authoritative proxy for domain example.com. Similar mutual authentication guarantees are given between proxy.example.com and proxy.example.net and between proxy.example.net and bob@example.net. As a result, alice@example.com is transitively mutually authenticated to Gurbani, et al. Expires January 15, 2009 [Page 12]
Internet-Draft Domain Certs July 2008 bob@example.net (assuming trust in the authoritative proxies for example.com and example.net). 8.1. Connection authentication using Digest Digest authentication in SIP provides for authentication of the message sender to the challenging UAS. As commonly deployed, it provides only very limited integrity protection of the authenticated message. Many existing deployments have chosen to use the Digest authentication of one or more messages on a particular connection as a way to authenticate the connection itself - and by implication, authenticating other (unchallenged) messages on that connection. Some even choose to similarly authenticate a UDP source address and port based on the Digest authentication of a message received from that address and port. This use of Digest goes beyond the assurances it was designed to provide, and is NOT RECOMMENDED. Authentication of the domain at the other end of a connection SHOULD be accomplished using TLS and the certificate validation rules described by this specification instead. 9. IANA Considerations This memo does not contain any considerations for IANA. 10. Acknowledgments The following IETF contributors provided substantive input to this document: Jeroen van Bemmel, Michael Hammer, Cullen Jennings, Paul Kyzivat, Derek MacDonald, Dave Oran, Jon Peterson, Eric Rescorla, Jonathan Rosenberg, Russ Housley. Special acknowledgement goes to Stephen Kent for extensively reviewing draft versions and suggesting invaluable feedback, edits, and comments. Paul Hoffman, Eric Rescorla and Robert Sparks provided much valuable WGLC comments. 11. References 11.1. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", RFC 2119, March 1997. [2] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M., and E. Schooler, "SIP: Gurbani, et al. Expires January 15, 2009 [Page 13]
Internet-Draft Domain Certs July 2008 Session Initiation Protocol", RFC 3261, June 2002. [3] Dierks, T. and E. Rescorla, "The TLS Protocol Version 1.1", RFC 4346, April 2006. [4] Cooper, D., Santesson, S., Farrell, S., Boyen, S., Housley, R., and W. Polk, "Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 5280, May 2008. [5] Lawrence, S. and V. Gurbani, "Using Extended Key Usage (EKU) for Session Initiation Protocol (SIP) X.509 Certificates", draft-ietf-sip-eku-01.txt (work in progress), February 2008. 11.2. Informative References [6] Rosenberg, J. and H. Schulzrinne, "Session Initiation Protocol (SIP): Location SIP Servers", RFC 3263, June 2002. [7] Rescorla, E., "HTTP Over TLS", RFC 2818, May 2000. [8] Blake-Wilson, S., Nystrom, M., Hopwood, D., Mikkelsen, J., and T. Wright, "Transport Layer Security (TLS) Extensions", RFC 4366, April 2006. [9] Peterson, J. and C. Jennings, "Enhancements for Authenticated Identity Management in the Session Initiation Protocol (SIP)", RFC 4474, August 2006. [10] Mahy, R., Gurbani, V., and B. Tate, "Connection Reuse in the Session Initiation Protocol", draft-ietf-sip-connect-reuse-08.txt (work in progress), October 2007. [11] Drage, K., "A Process for Handling Essential Corrections to the Session Initiation Protocol (SIP)", draft-drage-sip-essential-correction-02.txt (work in progress), November 2007. Appendix A. Editorial guidance (non-normative) This document is intended to update RFC 3261 in accordance with the SIP Working Group procedures described in [11] or its successor. This appendix provides guidance to the editor of the next comprehensive update to RFC 3261 [2] on how to incorporate the changes provided by this document. Gurbani, et al. Expires January 15, 2009 [Page 14]
Internet-Draft Domain Certs July 2008 A.1. Additions The content of sections Section 4 through Section 7 inclusive can be incorporated as subsections within a section that describes SIP domain authentication. Any normative references from this document should be carried forward to the successor document. A.2. Changes The following subsections describe changes in specific sections of RFC 3261 [2] that need to be modified in the successor document to align them with the content of this document. In each of the following, the token <domain-authentication> is a reference to the section added as described in Appendix A.1. A.2.1. 26.3.1 The current text says: Proxy servers, redirect servers and registrars SHOULD possess a site certificate whose subject corresponds to their canonical hostname. The suggested replacement for the above is: Proxy servers, redirect servers, registrars, and any other server that is authoritative for some SIP purpose in a given domain SHOULD possess a certificate whose subject is expressed as described in <domain-authentication>. Authors' Addresses Vijay K. Gurbani Bell Laboratories, Alcatel-Lucent 2701 Lucent Lane Room 9F-546 Lisle, IL 60532 USA Phone: +1 630 224-0216 Email: vkg@alcatel-lucent.com Gurbani, et al. Expires January 15, 2009 [Page 15]
Internet-Draft Domain Certs July 2008 Scott Lawrence Bluesocket Inc. 10 North Ave. Burlington, MA 01803 USA Phone: +1 781 229 0533 Email: slawrence@bluesocket.com Alan S.A. Jeffrey Bell Laboratories, Alcatel-Lucent 2701 Lucent Lane Room 9F-534 Lisle, IL 60532 USA Email: ajeffrey@alcatel-lucent.com Gurbani, et al. Expires January 15, 2009 [Page 16]
Internet-Draft Domain Certs July 2008 Full Copyright Statement Copyright (C) The IETF Trust (2008). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Intellectual Property The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Acknowledgment Funding for the RFC Editor function is provided by the IETF Administrative Support Activity (IASA). Gurbani, et al. Expires January 15, 2009 [Page 17]
