--- 1/draft-ietf-sipbrandy-osrtp-07.txt 2019-03-26 04:16:17.086862775 -0700 +++ 2/draft-ietf-sipbrandy-osrtp-08.txt 2019-03-26 04:16:17.110863361 -0700 @@ -1,26 +1,26 @@ SIPBRANDY Working Group A. Johnston Internet-Draft Villanova University Intended status: Informational B. Aboba -Expires: June 6, 2019 Microsoft +Expires: September 27, 2019 Microsoft A. Hutton Atos R. Jesske Deutsche Telekom T. Stach Unaffiliated - December 3, 2018 + March 26, 2019 An Opportunistic Approach for Secure Real-time Transport Protocol (OSRTP) - draft-ietf-sipbrandy-osrtp-07 + draft-ietf-sipbrandy-osrtp-08 Abstract Opportunistic Secure Real-time Transport Protocol (OSRTP) is an implementation of the Opportunistic Security mechanism, as defined in RFC 7435, applied to Real-time Transport Protocol (RTP). OSRTP allows encrypted media to be used in environments where support for encryption is not known in advance, and not required. OSRTP does not require SDP extensions or features and is fully backwards compatible with existing implementations using encrypted and authenticated media @@ -38,25 +38,25 @@ 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/. 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 June 6, 2019. + This Internet-Draft will expire on September 27, 2019. Copyright Notice - Copyright (c) 2018 IETF Trust and the persons identified as the + Copyright (c) 2019 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 @@ -64,39 +64,39 @@ Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Applicability Statement . . . . . . . . . . . . . . . . . 3 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3 3. SDP Offer/Answer Considerations . . . . . . . . . . . . . . . 3 3.1. Generating the Initial OSRTP Offer . . . . . . . . . . . 4 3.2. Generating the Answer . . . . . . . . . . . . . . . . . . 4 3.3. Offerer Processing the Answer . . . . . . . . . . . . . . 4 - 3.4. Modifying the Session . . . . . . . . . . . . . . . . . . 4 + 3.4. Modifying the Session . . . . . . . . . . . . . . . . . . 5 4. Security Considerations . . . . . . . . . . . . . . . . . . . 5 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 6. Implementation Status . . . . . . . . . . . . . . . . . . . . 5 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 8.1. Normative References . . . . . . . . . . . . . . . . . . 6 - 8.2. Informative References . . . . . . . . . . . . . . . . . 7 + 8.2. Informative References . . . . . . . . . . . . . . . . . 8 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 1. Introduction Opportunistic Security [RFC7435] (OS) is an approach to security that defines a third mode for security between "cleartext" and "comprehensive protection" that allows encryption and authentication - to be used if supported but will not result in failures if it is not - supported. In terms of secure media, cleartext is RTP [RFC3550] - media which is negotiated with the RTP/AVP (Audio Video Profile) - [RFC3551] or the RTP/AVPF profile [RFC4585]. Comprehensive + of media to be used if supported but will not result in failures if + it is not supported. In terms of secure media, cleartext is RTP + [RFC3550] media which is negotiated with the RTP/AVP (Audio Video + Profile) [RFC3551] or the RTP/AVPF profile [RFC4585]. Comprehensive protection is Secure RTP [RFC3711], negotiated with a secure profile, such as SAVP or SAVPF [RFC5124]. OSRTP allows SRTP to be negotiated with the RTP/AVP profile, with fallback to RTP if SRTP is not supported. There have been some extensions to SDP to allow profiles to be negotiated such as SDP Capabilities Negotiation (capneg) [RFC5939] . However, these approaches are complex and have very limited deployment in communication systems. Other key management protocols for SRTP have been developed which by design use OS, such as ZRTP @@ -119,47 +119,49 @@ OSRTP is a transitional approach that provides a migration path from unencrypted communication (RTP) to fully encrypted communication (SRTP). It is only to be used in existing deployments which are attempting to transition to fully secure communications. New applications and new deployments will not use OSRTP. 2. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and - "OPTIONAL" in this document are to be interpreted as described in RFC - 2119 [RFC2119]. + "OPTIONAL" in this document are to be interpreted as described in BCP + 14 RFC 2119 [RFC2119] RFC 8174 [RFC8174] when, and only when, they + appear in all capitals, as shown here. 3. SDP Offer/Answer Considerations This section defines the SDP offer/answer considerations for opportunistic security. The procedures are for a specific m- section describing RTP-based media. If an SDP offer or answer contains multiple such m- sections, the procedures are applied to each m- section individually. "Initial OSRTP offer" refers to the offer in which oportunistic security is offered for an m- section for the first time within an SDP session. It is important to note that OSRTP makes no changes, and has no effect on media sessions in which the offer contains a secure profile - of RTP, such as SAVP or SAVPF. As discussed in [RFC7435], this is + of RTP, such as SAVP or SAVPF. As discussed in [RFC7435], that is the "comprehensive protection" for media mode. 3.1. Generating the Initial OSRTP Offer To indicate support for OSRTP in an SDP offer, the offerer uses the RTP/AVP profile [RFC3551] or the RTP/AVPF profile [RFC4585] but includes SRTP keying attributes. OSRTP is not specific to any key - management technique for SRTP. For example: + management technique for SRTP and multiple key management techniques + can be included on the SDP offer. For example: If the offerer supports DTLS-SRTP key agreement [RFC5763], then an a=fingerprint attribute will be present, or If the offerer supports SDP Security Descriptions key agreement [RFC4568], then an a=crypto attribute will be present, or If the offerer supports ZRTP key agreement [RFC6189], then an a=zrtp-hash attribute will be present. @@ -180,34 +182,35 @@ If the offerer of OSRTP receives an SDP answer which does not contain SRTP keying attributes, then the media session proceeds with RTP. If the SDP answer contains SRTP keying attributes then the associated SRTP key management approach is followed and SRTP media is used for this session. If the SRTP key management fails, the media session MUST fail. 3.4. Modifying the Session - When an offerer generates a subsequent offer it should do so + When an offerer generates a subsequent SDP offer it should do so following the principles of [RFC6337] meaning that the decision to - create an OSRTP type offer or something else should not be influenced - by what was previously negotiated. For example if a previous OSRTP - offer did not result in SRTP being established the offerer may try - again and generate a new OSRTP offer as specified in section [3.1]. + create the new SDP offer should not be influenced by what was + previously negotiated. For example if a previous OSRTP offer did not + result in SRTP being established the offerer may try again and + generate a new OSRTP offer as specified in section [3.1]. 4. Security Considerations The security considerations of [RFC7435] apply to OSRTP, as well as the security considerations of the particular SRTP key agreement approach used. However, the authentication requirements of a particular SRTP key agreement approach are relaxed when that key - agreement is used with OSRTP. For example: + agreement is used with OSRTP, which is consistent with the + Opportunistic Security approach described [RFC7435]. For example: For DTLS-SRTP key agreement [RFC5763], an authenticated signaling channel does not need to be used with OSRTP if it is not available. For SDP Security Descriptions key agreement [RFC4568], an authenticated signaling channel does not need to be used with OSRTP if it is not available, although an encrypted signaling channel must still be used. @@ -319,69 +322,75 @@ [RFC6189] Zimmermann, P., Johnston, A., Ed., and J. Callas, "ZRTP: Media Path Key Agreement for Unicast Secure RTP", RFC 6189, DOI 10.17487/RFC6189, April 2011, . [RFC7435] Dukhovni, V., "Opportunistic Security: Some Protection Most of the Time", RFC 7435, DOI 10.17487/RFC7435, December 2014, . + [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC + 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, + May 2017, . + 8.2. Informative References [I-D.kaplan-mmusic-best-effort-srtp] Audet, F. and H. Kaplan, "Session Description Protocol (SDP) Offer/Answer Negotiation For Best-Effort Secure Real-Time Transport Protocol", draft-kaplan-mmusic-best- effort-srtp-01 (work in progress), October 2006. [IMTC-SIP] - "Best Practices for SIP Security", IMTC SIP Parity + Group, I. S. P. A., "Best Practices for SIP Security", + IMTC SIP Parity Group http://www.imtc.org/uc/sip-parity-activity-group/, 2011, . [RFC5939] Andreasen, F., "Session Description Protocol (SDP) Capability Negotiation", RFC 5939, DOI 10.17487/RFC5939, September 2010, . [RFC6337] Okumura, S., Sawada, T., and P. Kyzivat, "Session Initiation Protocol (SIP) Usage of the Offer/Answer Model", RFC 6337, DOI 10.17487/RFC6337, August 2011, . [RFC6982] Sheffer, Y. and A. Farrel, "Improving Awareness of Running Code: The Implementation Status Section", RFC 6982, DOI 10.17487/RFC6982, July 2013, . [SIPCONNECT] - "SIP-PBX / Service Provider Interoperability SIPconnect - 2.0 - Technical Recommendation", SIP Forum http://www.sipf - orum.org/component/option,com_docman/task,doc_download/ - gid,838/Itemid,261/, 2017, . + Group, S. F. S. 2. T., "SIP-PBX / Service Provider + Interoperability SIPconnect 2.0 - Technical + Recommendation", SIP Forum http://www.sipforum.org/compone + nt/option,com_docman/task,doc_download/gid,838/ + Itemid,261/, 2017, . Authors' Addresses Alan Johnston Villanova University Villanova, PA USA Email: alan.b.johnston@gmail.com - Bernard Aboba Microsoft One Microsoft Way Redmond, WA 98052 USA Email: bernard.aboba@gmail.com + Andrew Hutton Atos Mid City Place London WC1V 6EA UK Email: andrew.hutton@atos.net Roland Jesske Deutsche Telekom