Jingle RTP Sessions (XEP-0167) [1] recommends the use of the Secure Real-time Transport Protocol (SRTP) for end-to-end encryption of RTP sessions negotiated using Jingle (XEP-0166) [2]. RFC 5763 [3] provides an approach to establish a Secure Real-time Transport Protocol (SRTP) security context using the Datagram Transport Layer Security (DTLS) protocol. A mechanism of transporting the fingerprint attribute that identifies the key that will be presented during the DTLS handshake in Jingle is defined herein. Inclusion of this information is OPTIONAL in both SIP/SDP and Jingle.
Note that while this specification only describes the use in the context of DTLS-SRTP, the fingerprint transported can be used in other contexts like for example establishing connections using SCTP over DTLS as described in Signaling WebRTC datachannels in Jingle (XEP-0343) [4].
The SDP format (defined in RFC 4572 [5]) is shown below.
a=fingerprint:hash-func fingerprint
An example follows.
a=fingerprint:sha-256 02:1A:CC:54:27:AB:EB:9C:53:3F:3E:4B:65:2E:7D:46:3F:54:42:CD:54:F1:7A:03:A2:7D:F9:B0:7F:46:19:B2
Additionally, the SDP setup attribute defined in RFC 4145 [6] must be mapped, whose usage for DTLS-SRTP is defined in RFC 5763 [3].
a=setup:role
Note that no mapping for the 'holdconn' role is defined herein.
These SDP attributes can be translated into Jingle as a <fingerprint/> element qualified by the 'urn:xmpp:jingle:apps:dtls:0' namespace, as shown below.
<fingerprint xmlns='urn:xmpp:jingle:apps:dtls:0' hash='hash-func' setup='role'> fingerprint </fingerprint>
An example follows. Note that the whitespace would not appear in actual XML content.
<fingerprint xmlns='urn:xmpp:jingle:apps:dtls:0' hash='sha-256' setup='actpass'> 02:1A:CC:54:27:AB:EB:9C:53:3F:3E:4B:65:2E:7D:46:3F:54:42:CD:54:F1:7A:03:A2:7D:F9:B0:7F:46:19:B2 </fingerprint>
If the Jingle initiator wishes to use DTLS-SRTP, it includes the <fingerprint/> element in its session invitation.
<iq from='romeo@montague.lit/orchard'
id='uz61v4m4'
to='juliet@capulet.lit/balcony'
type='set'>
<jingle xmlns='urn:xmpp:jingle:1'
action='session-initiate'
initiator='romeo@montague.lit/orchard'
sid='a73sjjvkla37jfea'>
<content creator='initiator' name='voice'>
<description xmlns='urn:xmpp:jingle:apps:rtp:1' media='audio'>
<payload-type id='96' name='speex' clockrate='16000'/>
<payload-type id='97' name='speex' clockrate='8000'/>
<payload-type id='18' name='G729'/>
<payload-type id='103' name='L16' clockrate='16000' channels='2'/>
<payload-type id='98' name='x-ISAC' clockrate='8000'/>
</description>
<transport xmlns='urn:xmpp:jingle:transports:ice-udp:1'
pwd='asd88fgpdd777uzjYhagZg'
ufrag='8hhy'>
<fingerprint xmlns='urn:xmpp:jingle:apps:dtls:0' hash='sha-256' setup='actpass'>
02:1A:CC:54:27:AB:EB:9C:53:3F:3E:4B:65:2E:7D:46:3F:54:42:CD:54:F1:7A:03:A2:7D:F9:B0:7F:46:19:B2
</fingerprint>
<candidate component='1'
foundation='1'
generation='0'
id='el0747fg11'
ip='10.0.1.1'
network='1'
port='8998'
priority='2130706431'
protocol='udp'
type='host'/>
<candidate component='1'
foundation='2'
generation='0'
id='y3s2b30v3r'
ip='192.0.2.3'
network='1'
port='45664'
priority='1694498815'
protocol='udp'
rel-addr='10.0.1.1'
rel-port='8998'
type='srflx'/>
</transport>
</content>
</jingle>
</iq>
If the receiving party wishes to use DTLS, it also includes the <fingerprint/> element in its session-accept message.
<iq from='juliet@capulet.lit/balcony'
id='pn2va48j'
to='romeo@montague.lit/orchard'
type='set'>
<jingle xmlns='urn:xmpp:jingle:1'
action='session-accept'
initiator='romeo@montague.lit/orchard'
responder='juliet@capulet.lit/balcony'
sid='a73sjjvkla37jfea'>
<content creator='initiator' name='voice'>
<description xmlns='urn:xmpp:jingle:apps:rtp:1' media='audio'>
<payload-type id='97' name='speex' clockrate='8000'/>
<payload-type id='18' name='G729'/>
</description>
<transport xmlns='urn:xmpp:jingle:transports:ice-udp:1'
pwd='YH75Fviy6338Vbrhrlp8Yh'
ufrag='9uB6'>
<fingerprint xmlns='urn:xmpp:jingle:apps:dtls:0' hash='sha-256' setup='active'>
BD:E8:2C:D3:BD:B6:98:50:45:7D:5B:36:89:53:31:15:52:25:88:82:06:95:88:A3:3D:A5:43:8D:5C:21:21:66
</fingerprint>
<candidate component='1'
foundation='1'
generation='0'
id='or2ii2syr1'
ip='192.0.2.1'
network='0'
port='3478'
priority='2130706431'
protocol='udp'
type='host'/>
</transport>
</content>
</jingle>
</iq>
Alternatively, if the receiving party wishes to expedite with ICE and DTLS negotiation without accepting the session, it MAY include the <fingerprint/> element when sending a transport-info message:
<iq from='juliet@capulet.lit/balcony'
id='pn2va48j'
to='romeo@montague.lit/orchard'
type='set'>
<jingle xmlns='urn:xmpp:jingle:1'
action='transport-info'
initiator='romeo@montague.lit/orchard'
responder='juliet@capulet.lit/balcony'
sid='a73sjjvkla37jfea'>
<content creator='initiator' name='voice'>
<transport xmlns='urn:xmpp:jingle:transports:ice-udp:1'
pwd='YH75Fviy6338Vbrhrlp8Yh'
ufrag='9uB6'>
<fingerprint xmlns='urn:xmpp:jingle:apps:dtls:0' hash='sha-256' setup='active'>
BD:E8:2C:D3:BD:B6:98:50:45:7D:5B:36:89:53:31:15:52:25:88:82:06:95:88:A3:3D:A5:43:8D:5C:21:21:66
</fingerprint>
<candidate component='1'
foundation='1'
generation='0'
id='or2ii2syr1'
ip='192.0.2.1'
network='0'
port='3478'
priority='2130706431'
protocol='udp'
type='host'/>
</transport>
</content>
</jingle>
</iq>
If an entity supports establishing a Secure Real-time Transport Protocol security context using the Datagram Transport Layer Security protocol, it MUST advertise that fact in its responses to Service Discovery (XEP-0030) [7] information ("disco#info") requests by returning a feature of "urn:xmpp:jingle:apps:dtls:0":
<iq type='get'
from='calvin@usrobots.lit/lab'
to='herbie@usrobots.lit/home'
id='disco1'>
<query xmlns='http://jabber.org/protocol/disco#info'/>
</iq>
<iq type='result'
from='herbie@usrobots.lit/home'
to='calvin@usrobots.lit/lab'
id='disco1'>
<query xmlns='http://jabber.org/protocol/disco#info'>
<feature var='urn:xmpp:jingle:1'/>
<feature var='urn:xmpp:jingle:apps:dtls:0'/>
</query>
</iq>
In order for an application to determine whether an entity supports this protocol, where possible it SHOULD use the dynamic, presence-based profile of service discovery defined in Entity Capabilities (XEP-0115) [8]. However, if an application has not received entity capabilities information from an entity, it SHOULD use explicit service discovery instead.
Security considerations for DTLS-SRTP itself are provided in RFC 5763 [3].
XMPP stanzas such as Jingle messages and service discovery exchanges are not encrypted or signed. As a result, it is possible for an attacker to intercept these stanzas and modify them, thus convincing one party that the other party does not support DTLS-SRTP and therefore denying the parties an opportunity to use DTLS-SRTP.
This document requires no interaction with the Internet Assigned Numbers Authority (IANA) [9].
Thanks to Justin Uberti, Peter Saint-Andre and Lance Stout.
This specification defines the following XML namespace:
The XMPP Registrar [10] includes the foregoing namespace to the registry located at <https://xmpp.org/registrar/namespaces.html>, as described in Section 4 of XMPP Registrar Function (XEP-0053) [11].
If the protocol defined in this specification undergoes a revision that is not fully backwards-compatible with an older version, the XMPP Registrar shall increment the protocol version number found at the end of the XML namespaces defined herein, as described in Section 4 of XEP-0053.
<?xml version='1.0' encoding='UTF-8'?>
<xs:schema
xmlns:xs='http://www.w3.org/2001/XMLSchema'
targetNamespace='urn:xmpp:jingle:apps:dtls:0'
xmlns='urn:xmpp:jingle:apps:dtls:0'
elementFormDefault='qualified'>
<xs:annotation>
<xs:documentation>
The protocol documented by this schema is defined in
XEP-xxxx: http://www.xmpp.org/extensions/xep-xxxx.html
</xs:documentation>
</xs:annotation>
<xs:element name='fingerprint'>
<xs:complexType>
<xs:simpleContent>
<xs:extension base='xs:string'>
<xs:attribute name='hash' type='xs:string' use='required'/>
<xs:attribute name='setup' use='required'/>
<xs:simpleType>
<xs:restriction base='xs:NCName'>
<xs:enumeration value='active'/>
<xs:enumeration value='passive'/>
<xs:enumeration value='actpass'/>
<xs:enumeration value='holdconn'/>
<xs:annotation>
<xs:documentation>
the 'holdconn' value is not used and included only for completeness.
</xs:documentation>
</xs:annotation>
</xs:restriction>
</xs:simpleType>
</xs:attribute>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
</xs:schema>
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This XMPP Extension Protocol has been contributed in full conformance with the XSF's Intellectual Property Rights Policy (a copy of which can be found at <https://xmpp.org/about/xsf/ipr-policy> or obtained by writing to XMPP Standards Foundation, P.O. Box 787, Parker, CO 80134 USA).
The HTML representation (you are looking at) is maintained by the XSF. It is based on the YAML CSS Framework, which is licensed under the terms of the CC-BY-SA 2.0 license.
The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 6120) and XMPP IM (RFC 6121) specifications contributed by the XMPP Standards Foundation to the Internet Standards Process, which is managed by the Internet Engineering Task Force in accordance with RFC 2026. Any protocol defined in this document has been developed outside the Internet Standards Process and is to be understood as an extension to XMPP rather than as an evolution, development, or modification of XMPP itself.
There exists a special venue for discussion related to the technology described in this document: the <jingle@xmpp.org> mailing list.
The primary venue for discussion of XMPP Extension Protocols is the <standards@xmpp.org> discussion list.
Discussion on other xmpp.org discussion lists might also be appropriate; see <https://xmpp.org/community/> for a complete list.
Given that this XMPP Extension Protocol normatively references IETF technologies, discussion on the <xsf-ietf@xmpp.org> list might also be appropriate.
Errata can be sent to <editor@xmpp.org>.
The following requirements keywords as used in this document are to be interpreted as described in RFC 2119: "MUST", "SHALL", "REQUIRED"; "MUST NOT", "SHALL NOT"; "SHOULD", "RECOMMENDED"; "SHOULD NOT", "NOT RECOMMENDED"; "MAY", "OPTIONAL".
1. XEP-0167: Jingle RTP Sessions <https://xmpp.org/extensions/xep-0167.html>.
2. XEP-0166: Jingle <https://xmpp.org/extensions/xep-0166.html>.
3. RFC 5763: Framework for Establishing a Secure Real-time Transport Protocol (SRTP) Security Context Using Datagram Transport Layer Security (DTLS) <http://tools.ietf.org/html/rfc5763>.
4. XEP-0343: Signaling WebRTC datachannels in Jingle <https://xmpp.org/extensions/xep-0343.html>.
5. RFC 4572: Connection-Oriented Media Transport over the Transport Layer Security (TLS) Protocol in the Session Description Protocol (SDP) <http://tools.ietf.org/html/rfc4572>.
6. RFC 4145: TCP-Based Media Transport in the Session Description Protocol (SDP) <http://tools.ietf.org/html/rfc4145>.
7. XEP-0030: Service Discovery <https://xmpp.org/extensions/xep-0030.html>.
8. XEP-0115: Entity Capabilities <https://xmpp.org/extensions/xep-0115.html>.
9. The Internet Assigned Numbers Authority (IANA) is the central coordinator for the assignment of unique parameter values for Internet protocols, such as port numbers and URI schemes. For further information, see <http://www.iana.org/>.
10. The XMPP Registrar maintains a list of reserved protocol namespaces as well as registries of parameters used in the context of XMPP extension protocols approved by the XMPP Standards Foundation. For further information, see <https://xmpp.org/registrar/>.
11. XEP-0053: XMPP Registrar Function <https://xmpp.org/extensions/xep-0053.html>.
Note: Older versions of this specification might be available at https://xmpp.org/extensions/attic/
Move to Draft as per Council vote from 2020-05-20.
Initial published version approved by the XMPP Council.
Second draft, rewrite no longer based on XEP-0262.
First draft, copied from XEP-0262.
@report{hancke2012xep0320,
title = {Use of DTLS-SRTP in Jingle Sessions},
author = {Hancke, Philipp},
type = {XEP},
number = {0320},
version = {1.0.0},
institution = {XMPP Standards Foundation},
url = {https://xmpp.org/extensions/xep-0320.html},
date = {2012-12-13/2020-05-26},
}END