draft-ietf-xmpp-dna-10.txt   draft-ietf-xmpp-dna-11.txt 
Network Working Group P. Saint-Andre Network Working Group P. Saint-Andre
Internet-Draft &yet Internet-Draft &yet
Intended status: Standards Track M. Miller Intended status: Standards Track M. Miller
Expires: September 25, 2015 Cisco Systems, Inc. Expires: March 4, 2016 Cisco Systems, Inc.
P. Hancke P. Hancke
&yet &yet
March 24, 2015 September 1, 2015
Domain Name Associations (DNA) in the Extensible Messaging and Presence Domain Name Associations (DNA) in the Extensible Messaging and Presence
Protocol (XMPP) Protocol (XMPP)
draft-ietf-xmpp-dna-10 draft-ietf-xmpp-dna-11
Abstract Abstract
This document improves the security of the Extensible Messaging and This document improves the security of the Extensible Messaging and
Presence Protocol (XMPP) in two ways. First, it specifies how to Presence Protocol (XMPP) in two ways. First, it specifies how to
establish a strong association between a domain name and an XML establish a strong association between a domain name and an XML
stream, using the concept of "prooftypes". Second, it describes how stream, using the concept of "prooftypes". Second, it describes how
to securely delegate a service domain name (e.g., example.com) to a to securely delegate a service domain name (e.g., example.com) to a
target server host name (e.g., hosting.example.net), which is target server host name (e.g., hosting.example.net), which is
especially important in multi-tenanted environments where the same especially important in multi-tenanted environments where the same
skipping to change at page 1, line 41 skipping to change at page 1, line 41
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 25, 2015. This Internet-Draft will expire on March 4, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Client-to-Server (C2S) DNA . . . . . . . . . . . . . . . . . 3 3. Client-to-Server (C2S) DNA . . . . . . . . . . . . . . . . . 4
3.1. C2S Flow . . . . . . . . . . . . . . . . . . . . . . . . 4 3.1. C2S Flow . . . . . . . . . . . . . . . . . . . . . . . . 4
3.2. C2S Description . . . . . . . . . . . . . . . . . . . . . 4 3.2. C2S Description . . . . . . . . . . . . . . . . . . . . . 4
4. Server-to-Server (S2S) DNA . . . . . . . . . . . . . . . . . 5 4. Server-to-Server (S2S) DNA . . . . . . . . . . . . . . . . . 5
4.1. S2S Flow . . . . . . . . . . . . . . . . . . . . . . . . 5 4.1. S2S Flow . . . . . . . . . . . . . . . . . . . . . . . . 5
4.2. A Simple S2S Scenario . . . . . . . . . . . . . . . . . . 8 4.2. A Simple S2S Scenario . . . . . . . . . . . . . . . . . . 9
4.3. No Mutual PKIX Authentication . . . . . . . . . . . . . . 10 4.3. No Mutual PKIX Authentication . . . . . . . . . . . . . . 10
4.4. Piggybacking . . . . . . . . . . . . . . . . . . . . . . 11 4.4. Piggybacking . . . . . . . . . . . . . . . . . . . . . . 12
4.4.1. Assertion . . . . . . . . . . . . . . . . . . . . . . 11 4.4.1. Assertion . . . . . . . . . . . . . . . . . . . . . . 12
4.4.2. Supposition . . . . . . . . . . . . . . . . . . . . . 12 4.4.2. Supposition . . . . . . . . . . . . . . . . . . . . . 13
5. Alternative Prooftypes . . . . . . . . . . . . . . . . . . . 13 5. Alternative Prooftypes . . . . . . . . . . . . . . . . . . . 14
5.1. DANE . . . . . . . . . . . . . . . . . . . . . . . . . . 14 5.1. DANE . . . . . . . . . . . . . . . . . . . . . . . . . . 15
5.2. POSH . . . . . . . . . . . . . . . . . . . . . . . . . . 14 5.2. POSH . . . . . . . . . . . . . . . . . . . . . . . . . . 15
6. Secure Delegation and Multi-Tenancy . . . . . . . . . . . . . 15 6. Secure Delegation and Multi-Tenancy . . . . . . . . . . . . . 16
7. Prooftype Model . . . . . . . . . . . . . . . . . . . . . . . 16 7. Prooftype Model . . . . . . . . . . . . . . . . . . . . . . . 17
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 8. Guidance for Server Operators . . . . . . . . . . . . . . . . 17
8.1. Well-Known URI for xmpp-client Service . . . . . . . . . 17 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
8.2. Well-Known URI for xmpp-server Service . . . . . . . . . 17 9.1. POSH Service Name for xmpp-client Service . . . . . . . . 18
9. Security Considerations . . . . . . . . . . . . . . . . . . . 17 9.2. POSH Service Name for xmpp-server Service . . . . . . . . 19
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 10. Security Considerations . . . . . . . . . . . . . . . . . . . 19
10.1. Normative References . . . . . . . . . . . . . . . . . . 17 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
10.2. Informative References . . . . . . . . . . . . . . . . . 19 11.1. Normative References . . . . . . . . . . . . . . . . . . 19
Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 19 11.2. Informative References . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 Appendix A. Acknowledgements . . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22
1. Introduction 1. Introduction
In systems that use the Extensible Messaging and Presence Protocol In systems that use the Extensible Messaging and Presence Protocol
(XMPP) [RFC6120], it is important to establish a strong association (XMPP) [RFC6120], it is important to establish a strong association
between the DNS domain name of an XMPP service (e.g., example.com) between the DNS domain name of an XMPP service (e.g., example.com)
and the XML stream that a client or peer server initiates with that and the XML stream that a client or peer server initiates with that
service. In other words, the client or peer server needs to verify service. In other words, the client or peer server needs to verify
the identity of the server to which it connects. Additionally, the identity of the server to which it connects. Additionally,
servers need to verify incoming connections from other servers. servers need to verify incoming connections from other servers.
To date, such verification has been established based on information To date, such verification has been established based on information
obtained from the Domain Name System (DNS), the Public Key obtained from the Domain Name System (DNS), the Public Key
Infrastructure (PKI), or similar sources. In relation to such Infrastructure (PKI), or similar sources. In particular, XMPP as
associations, this document does the following: defined in [RFC6120] assumed that domain name associations are to be
proved using the "PKIX prooftype"; that is, the server's proof
consists of a PKIX certificate that is checked according to the XMPP
profile of the matching rules from [RFC6125] (and the overall
validation rules from [RFC5280]), the client's verification material
is obtained out of band in the form of a trusted root, and secure DNS
is not necessary.
By extending the concept of a domain name association within XMPP,
this document does the following:
1. Generalizes the model currently in use so that additional 1. Generalizes the model currently in use so that additional
prooftypes can be defined if needed. prooftypes can be defined if needed.
2. Provides a basis for modernizing some prooftypes to reflect 2. Provides a basis for modernizing some prooftypes to reflect
progress in underlying technologies such as DNS Security progress in underlying technologies such as DNS Security
[RFC4033]. [RFC4033].
3. Describes the flow of operations for establishing a domain name 3. Describes the flow of operations for establishing a domain name
association (DNA). association (DNA).
This document also provides guidelines for secure delegation of a This document also provides guidelines for secure delegation of a
service domain name (e.g., example.com) to a target server host name service domain name (e.g., example.com) to a target server host name
(e.g., hosting.example.net). The need for secure delegation arises (e.g., hosting.example.net). The need for secure delegation arises
because the process for resolving the domain name of an XMPP service because the process for resolving the domain name of an XMPP service
into the IP address at which an XML stream will be negotiated (see into the IP address at which an XML stream will be negotiated (see
[RFC6120]) can involve delegation of a service domain name to a [RFC6120]) can involve delegation of a service domain name to a
target server host name using technologies such as DNS SRV records target server host name using technologies such as DNS SRV records
[RFC2782]. A more detailed description of the delegation problem can [RFC2782]. A more detailed description of the delegation problem can
be found in [I-D.ietf-xmpp-posh]. If such delegation is not done in be found in [I-D.ietf-xmpp-posh]. The domain name association can be
a secure manner, then the domain name association cannot be verified. verified only if the delegation is done in a secure manner.
2. Terminology 2. Terminology
This document inherits XMPP terminology from [RFC6120] and This document inherits XMPP terminology from [RFC6120] and
[XEP-0220], DNS terminology from [RFC1034], [RFC1035], [RFC2782] and [XEP-0220], DNS terminology from [RFC1034], [RFC1035], [RFC2782] and
[RFC4033], and security terminology from [RFC4949] and [RFC5280]. [RFC4033], and security terminology from [RFC4949] and [RFC5280].
The terms "reference identity", and "presented identity" are used as The terms "reference identity", and "presented identity" are used as
defined in the "CertID" specification [RFC6125]. For the sake of defined in the "CertID" specification [RFC6125]. For the sake of
consistency with [I-D.ietf-dane-srv], this document uses the terms consistency with [I-D.ietf-dane-srv], this document uses the terms
"service domain name" and "target server host name" to refer to the "service domain name" and "target server host name" to refer to the
skipping to change at page 4, line 17 skipping to change at page 4, line 25
The following flow chart illustrates the protocol flow for The following flow chart illustrates the protocol flow for
establishing a domain name association for an XML stream from a establishing a domain name association for an XML stream from a
client (C) to a server (S) using the standard PKIX prooftype client (C) to a server (S) using the standard PKIX prooftype
specified in [RFC6120]. specified in [RFC6120].
| |
DNS RESOLUTION ETC. DNS RESOLUTION ETC.
| |
+-----------------STREAM HEADERS---------------------+ +-----------------STREAM HEADERS---------------------+
| | | |
| C: <stream from='user@a.example' to='a.example'> | | C: <stream to='a.example'> |
| | | |
| S: <stream from='a.example' to='user@a.example'> | | S: <stream from='a.example'> |
| | | |
+----------------------------------------------------+ +----------------------------------------------------+
| |
+-----------------TLS NEGOTIATION--------------------+ +-----------------TLS NEGOTIATION--------------------+
| | | |
| S: Server Certificate | | S: Server Certificate |
| | | |
+----------------------------------------------------+ +----------------------------------------------------+
| |
(client checks certificate and (client checks certificate and
establishes DNA for a.example) establishes DNA for a.example)
|
3.2. C2S Description 3.2. C2S Description
The simplified order of events (see [RFC6120] for details) in The simplified order of events (see [RFC6120] for details) in
establishing an XML stream from a client (user@a.exmaple) to a server establishing an XML stream from a client (user@a.exmaple) to a server
(a.example) is as follows: (a.example) is as follows:
1. The client resolves via DNS the service _xmpp- 1. The client resolves via DNS the service _xmpp-
client._tcp.a.example. client._tcp.a.example.
2. The client opens a TCP connection to the resolved IP address. 2. The client opens a TCP connection to the resolved IP address.
3. The client sends an initial stream header to the server: 3. The client sends an initial stream header to the server:
<stream:stream from='user@a.example' to='a.example'> <stream:stream to='a.example'>
4. The server sends a response stream header to the client, 4. The server sends a response stream header to the client,
asserting that it is a.example: asserting that it is a.example:
<stream:stream from='a.example' to='user@a.example'> <stream:stream from='a.example'>
5. The parties attempt TLS negotiation, during which the XMPP server 5. The parties attempt TLS negotiation, during which the XMPP server
(acting as a TLS server) presents a PKIX certificate proving that (acting as a TLS server) presents a PKIX certificate proving that
it is a.example. it is a.example.
6. The client checks the PKIX certificate that the server provided; 6. The client checks the PKIX certificate that the server provided;
if the proof is consistent with the XMPP profile of the matching if the proof is consistent with the XMPP profile of the matching
rules from [RFC6125] and the certificate is otherwise valid rules from [RFC6125] and the certificate is otherwise valid
according to [RFC5280], the client accepts that there is a strong according to [RFC5280], the client accepts that there is a strong
domain name association between its stream to the target server domain name association between its stream to the target server
and the DNS domain name of the XMPP service. and the DNS domain name of the XMPP service.
The certificate that the server presents might not be trusted by the The certificate that the server presents might not be acceptable to
client. As one example, the server might be hosting multiple domains the client. As one example, the server might be hosting multiple
and secure delegation as described in Section 6 is necessary. As domains and secure delegation as described in Section 6 is necessary.
another example, the server might present a self-signed certificate, As another example, the server might present a self-signed
which requires the client to apply either the fallback process certificate, which requires the client to apply either the fallback
described in section 6.6.4 of [RFC6125] or prompt the user to accept process described in section 6.6.4 of [RFC6125] or prompt the user to
an unauthenticated connection as described in [I-D.ietf-uta-xmpp]. accept an unauthenticated connection as described in Section 3.4 of
[RFC7590].
4. Server-to-Server (S2S) DNA 4. Server-to-Server (S2S) DNA
The server-to-server case is significantly more complex than the The server-to-server case is significantly more complex than the
client-to-server case, and involves checking of domain name client-to-server case, and involves checking of domain name
associations in both directions along with other "wrinkles" described associations in both directions along with other "wrinkles" described
in the following sections. The Server Dialback protocol is defined in the following sections. In some parts of the flow, server-to-
in [XEP-0220]. See [XEP-0344] for considerations when using it server communications use the Server Dialback protocol first
together with TLS and DNSSEC. Also, [XEP-0288] provides a way to use specified in (the now obsolete) [RFC3920] and since moved to
the server-to-server connections for bidirectional exchange of XML [XEP-0220]. See "Impact of TLS and DNSSEC on Dialback" [XEP-0344]
stanzas which reduces the complexity of some of the processes for considerations when using it together with TLS and DNSSEC. Also,
involved. "Bidirectional Server-to-Server Connections" [XEP-0288] provides a
way to use the server-to-server connections for bidirectional
exchange of XML stanzas, which reduces the complexity of some of the
processes involved.
4.1. S2S Flow 4.1. S2S Flow
The following flow chart illustrates the protocol flow for The following flow charts illustrate the protocol flow for
establishing domain name associations between Server A (the establishing domain name associations between Server 1 (the
initiating entity) and Server B (the receiving entity), as described initiating entity) and Server 2 (the receiving entity), as described
in the remaining sections of this document. in the remaining sections of this document.
| A simple S2S scenario would be as follows.
(A Simple S2S Scenario)
| |
DNS RESOLUTION ETC. DNS RESOLUTION ETC.
| |
+-------------STREAM HEADERS--------------------+ +-------------STREAM HEADERS--------------------+
| | | |
| A: <stream from='a.example' to='b.example'> | | A: <stream from='a.example' to='b.example'> |
| | | |
| B: <stream from='b.example' to='a.example'> | | B: <stream from='b.example' to='a.example'> |
| | | |
+-----------------------------------------------+ +-----------------------------------------------+
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+-------------TLS NEGOTIATION-------------------+ +-------------TLS NEGOTIATION-------------------+
| | | |
| B: Server Certificate | | B: Server Certificate |
| B: Certificate Request | | B: Certificate Request |
| A: Client Certificate | | A: Client Certificate |
| | | |
+-----------------------------------------------+ +-----------------------------------------------+
| |
(A establishes DNA for b.example) (A establishes DNA for b.example)
| |
After the domain name association has been established in one
direction, it is possible to perform mutual authentication using
Simple Authentication and Security Layer (SASL) [RFC4422] and thus
establish domain name associations in both directions.
|
+-------------AUTHENTICATION--------------------+ +-------------AUTHENTICATION--------------------+
| | | | | |
| {valid client certificate?} --+ | | {valid client certificate?} --+ |
| | | | | | | |
| | yes no | | | | yes no | |
| v | | | v | |
| SASL EXTERNAL | | | SASL EXTERNAL | |
| (mutual auth!) | | | (mutual auth) | |
| (B establishes DNA for a.example) | | | (B establishes DNA for a.example) | |
+-------------------------------------|---------+ +-------------------------------------|---------+
| |
However, if mutual authentication cannot be completed using SASL, the
receiving server needs to establish a domain name association in
another way. This scenario is described in Section 4.3.
|
+-----------------+ +-----------------+
|
(Section 4.3: No Mutual PKIX authentication)
|
| B needs to establish DNA | B needs to establish DNA
| for this stream from a.example, | for this stream from a.example,
| so A asserts its identity | so A asserts its identity
| |
+----------DIALBACK IDENTITY ASSERTION----------+ +----------DIALBACK IDENTITY ASSERTION----------+
| | | |
| A: <db:result from='a.example' | | A: <db:result from='a.example' |
| to='b.example'> | | to='b.example'> |
| some-dialback-key | | some-dialback-key |
| </db:result> | | </db:result> |
| | | |
+-----------------------------------------------+ +-----------------------------------------------+
| |
(Section 4.3: No Mutual PKIX authentication)
|
DNS RESOLUTION ETC. DNS RESOLUTION ETC.
| |
+-------------STREAM HEADERS--------------------+ +-------------STREAM HEADERS--------------------+
| | | |
| B: <stream from='b.example' to='a.example'> | | B: <stream from='b.example' to='a.example'> |
| | | |
| A: <stream from='a.example' to='b.example'> | | A: <stream from='a.example' to='b.example'> |
| | | |
+-----------------------------------------------+ +-----------------------------------------------+
| |
skipping to change at page 7, line 29 skipping to change at page 8, line 5
| | | |
| A: <db:verify from='a.example' | | A: <db:verify from='a.example' |
| to='b.example' | | to='b.example' |
| type='valid' | | type='valid' |
| id='...'> | | id='...'> |
| | | |
+-----------------------------------------------+ +-----------------------------------------------+
| |
(B establishes DNA for a.example) (B establishes DNA for a.example)
| |
If one of the servers hosts additional service names (e.g., Server 2
might host c.example in addition to b.example and Server 1 might host
rooms.a.example in addition to a.example), then the servers can use
Server Dialback "piggybacking" to establish additional domain name
associations for the stream, as described in Section 4.4.
There are two varieties of piggybacking. The first is here called
"assertion".
| |
(Section 4.4.1: Piggybacking Assertion) (Section 4.4.1: Piggybacking Assertion)
| |
+----------DIALBACK IDENTITY ASSERTION----------+ +----------DIALBACK IDENTITY ASSERTION----------+
| | | |
| B: <db:result from='c.example' | | B: <db:result from='c.example' |
| to='a.example'/> | | to='a.example'/> |
| | | |
+-----------------------------------------------+ +-----------------------------------------------+
| |
skipping to change at page 8, line 6 skipping to change at page 8, line 40
+-----------------------------------------------+ +-----------------------------------------------+
| |
+----------DIALBACK IDENTITY VERIFICATION-------+ +----------DIALBACK IDENTITY VERIFICATION-------+
| | | |
| A: <db:result from='a.example' | | A: <db:result from='a.example' |
| to='c.example' | | to='c.example' |
| type='valid'/> | | type='valid'/> |
| | | |
+-----------------------------------------------+ +-----------------------------------------------+
| |
The second variety of piggybacking is here called "supposition".
| |
(Section 4.4.2: Piggybacking Supposition) (Section 4.4.2: Piggybacking Supposition)
| |
+-----------SUBSEQUENT CONNECTION---------------+ +-----------SUBSEQUENT CONNECTION---------------+
| | | |
| B: <stream from='c.example' | | B: <stream from='c.example' |
| to='rooms.a.example'> | | to='rooms.a.example'> |
| | | |
| A: <stream from='rooms.a.example' | | A: <stream from='rooms.a.example' |
| to='c.example'> | | to='c.example'> |
skipping to change at page 8, line 36 skipping to change at page 9, line 35
+-----------DIALBACK OPTIMIZATION---------------+ +-----------DIALBACK OPTIMIZATION---------------+
| | | |
| B: <db:result from='c.example' | | B: <db:result from='c.example' |
| to='rooms.a.example'/> | | to='rooms.a.example'/> |
| | | |
| B: <db:result from='rooms.a.example' | | B: <db:result from='rooms.a.example' |
| to='c.example' | | to='c.example' |
| type='valid'/> | | type='valid'/> |
| | | |
+-----------------------------------------------+ +-----------------------------------------------+
|
4.2. A Simple S2S Scenario 4.2. A Simple S2S Scenario
To illustrate the problem, consider the simplified order of events To illustrate the problem, consider the simplified order of events
(see [RFC6120] for details) in establishing an XML stream between (see [RFC6120] for details) in establishing an XML stream between
Server A (a.example) and Server B (b.example): Server 1 (a.example) and Server 2 (b.example):
1. Server A resolves via DNS the service _xmpp- 1. Server 1 resolves via DNS the service _xmpp-
server._tcp.b.example. server._tcp.b.example.
2. Server A opens a TCP connection to the resolved IP address. 2. Server 1 opens a TCP connection to the resolved IP address.
3. Server A sends an initial stream header to Server B, asserting 3. Server 1 sends an initial stream header to Server 2, asserting
that it is a.example: that it is a.example:
<stream:stream from='a.example' to='b.example'> <stream:stream from='a.example' to='b.example'>
4. Server B sends a response stream header to Server A, asserting 4. Server 2 sends a response stream header to Server 1, asserting
that it is b.example: that it is b.example:
<stream:stream from='b.example' to='a.example'> <stream:stream from='b.example' to='a.example'>
5. The servers attempt TLS negotiation, during which Server B 5. The servers attempt TLS negotiation, during which Server 2
(acting as a TLS server) presents a PKIX certificate proving that (acting as a TLS server) presents a PKIX certificate proving that
it is b.example and Server A (acting as a TLS client) presents a it is b.example and Server 1 (acting as a TLS client) presents a
PKIX certificate proving that it is a.example. PKIX certificate proving that it is a.example.
6. Server A checks the PKIX certificate that Server B provided and 6. Server 1 checks the PKIX certificate that Server 2 provided and
Server B checks the PKIX certificate that Server A provided; if Server 2 checks the PKIX certificate that Server 1 provided; if
these proofs are consistent with the XMPP profile of the matching these proofs are consistent with the XMPP profile of the matching
rules from [RFC6125] and is otherwise valid according to rules from [RFC6125] and are otherwise valid according to
[RFC5280], each server accepts that there is a strong domain name [RFC5280], each server accepts that there is a strong domain name
association between its stream to the other party and the DNS association between its stream to the other party and the DNS
domain name of the other party. domain name of the other party (i.e., mutual authentication is
achieved).
Several simplifying assumptions underlie the happy scenario just Several simplifying assumptions underlie the happy scenario just
outlined: outlined:
o The PKIX certificate presented by Server B during TLS negotiation o The PKIX certificate presented by Server 2 during TLS negotiation
is trusted by Server A and matches the expected identity. is acceptable to Server 1 and matches the expected identity.
o The PKIX certificate presented by Server A during TLS negotiation o The PKIX certificate presented by Server 1 during TLS negotiation
is trusted by Server B, which enables the parties to complete is acceptable to Server 2, which enables the parties to complete
mutual authentication. mutual authentication.
o There are no additional domains associated with Server A and o There are no additional domains associated with Server 1 and
Server B (say, a subdomain rooms.a.example on Server A or a second Server 2 (say, a subdomain rooms.a.example on Server 1 or a second
domain c.example on Server B). domain c.example on Server 2).
o The server administrators are able to obtain PKIX certificates o The server administrators are able to obtain PKIX certificates
issued by a widely-accepted certificate authority (CA) in the issued by a widely-accepted certification authority (CA) in the
first place. first place.
o The server administrators are running their own XMPP servers, o The server administrators are running their own XMPP servers,
rather than using hosting services. rather than using hosting services.
Let's consider each of these "wrinkles" in turn. Since Server A is Let's consider each of these "wrinkles" in turn.
acting as a S2S client the behaviour is same as in the C2S case
described in Section 3.2.
4.3. No Mutual PKIX Authentication 4.3. No Mutual PKIX Authentication
If the PKIX certificate presented by Server A during TLS negotiation If the PKIX certificate presented by Server 1 during TLS negotiation
is not trusted by Server B, Server B is unable to mutually is not acceptable to Server 2, Server 2 is unable to mutually
authenticate Server A. Therefore, Server B needs to verify the authenticate Server 1. Therefore, Server 2 needs to verify the
asserted identity of Server A by other means. asserted identity of Server 1 by other means.
1. Server A asserts it is a.example using the Server Dialback 1. Server 1 asserts it is a.example using the Server Dialback
protocol: protocol:
<db:result from='a.example' to='b.example' id='...'>some- <db:result from='a.example' to='b.example' id='...'>some-
dialback-key</db:result> dialback-key</db:result>
2. Server B resolves via DNS the service _xmpp- 2. Server 2 resolves via DNS the service _xmpp-
server._tcp.a.example. server._tcp.a.example.
3. Server B opens a TCP connection to the resolved IP address. 3. Server 2 opens a TCP connection to the resolved IP address.
4. Server B sends an initial stream header to Server A, asserting 4. Server 2 sends an initial stream header to Server 1, asserting
that it is b.example: that it is b.example:
<stream:stream from='b.example' to='a.example'> <stream:stream from='b.example' to='a.example'>
5. Server A sends a response stream header to Server B, asserting 5. Server 1 sends a response stream header to Server 2, asserting
that it is a.example: that it is a.example:
<stream:stream from='a.example' to='b.example'> <stream:stream from='a.example' to='b.example'>
6. The servers attempt TLS negotiation, during which Server A 6. The servers attempt TLS negotiation, during which Server 1
(acting as a TLS server) presents a PKIX certificate proving that (acting as a TLS server) presents a PKIX certificate.
it is a.example.
7. Server B checks the PKIX certificate that Server A provided. 7. Server 2 checks the PKIX certificate that Server 1 provided (this
This might be the same certificate presented by Server A as a might be the same certificate presented by Server 1 as a client
client certificate in the initial connection. See [XEP-0344] for certificate in the initial connection). However, Server 2 does
further discussion about skipping the subsequent steps. not accept this certificate as proving that Server 1 is
authorized as a.example and therefore uses another method (here,
the Server Dialback protocol) to establish the domain name
association.
8. Server B proceeds with Server Dialback in order to establish the 8. Server 2 proceeds with Server Dialback in order to establish the
domain name association. In order to do this it sends a request domain name association. In order to do this it sends a request
for verification as described in [XEP-0220]: for verification as described in [XEP-0220]:
<db:verify from='b.example' to='a.example' id='...'>some- <db:verify from='b.example' to='a.example' id='...'>some-
dialback-key</db:verify> dialback-key</db:verify>
9. Server A responds to this: 9. Server 1 responds to this:
<db:verify from='a.example' to='b.example' id='...' type='valid/> <db:verify from='a.example' to='b.example' id='...' type='valid/>
allowing Server B to establish the domain name association.
allowing Server 2 to establish the domain name association.
In some situations (e.g., if the Authoritative Server in Server
Dialback presents the same certificate as the Originating Server), it
is the practice of some XMPP server implementations to skip steps 8
and 9. These situations are discussed in "Impact of TLS and DNSSEC
on Dialback" [XEP-0344].
4.4. Piggybacking 4.4. Piggybacking
4.4.1. Assertion 4.4.1. Assertion
Consider the common scenario in which Server B hosts not only Consider the common scenario in which Server 2 hosts not only
b.example but also a second domain c.example (often called a "multi- b.example but also a second domain c.example (often called a "multi-
tenanted" environment). If a user of Server B associated with tenanted" environment). If a user of Server 2 associated with
c.example wishes to communicate with a friend at a.example, Server B c.example wishes to communicate with a friend at a.example, Server 2
needs to send XMPP stanzas from the domain c.example rather than needs to send XMPP stanzas from the domain c.example rather than
b.example. Although Server B could open a new TCP connection and b.example. Although Server 2 could open a new TCP connection and
negotiate new XML streams for the domain pair of c.example and negotiate new XML streams for the domain pair of c.example and
a.example, that too is wasteful (especially if Server B hosts a large a.example, that is wasteful (especially if Server 2 hosts a large
number of domains). Server B already has a connection to a.example, number of domains). Server 2 already has a connection to a.example,
so how can it assert that it would like to add a new domain pair to so how can it assert that it would like to add a new domain pair to
the existing connection? the existing connection?
The traditional method for doing so is the Server Dialback protocol, The traditional method for doing so is the Server Dialback protocol
first specified in (the now obsolete) [RFC3920] and since moved to [XEP-0220]. Here, Server 2 can send a <db:result/> element for the
[XEP-0220]. Here, Server B can send a <db:result/> element for the
new domain pair over the existing stream. new domain pair over the existing stream.
<db:result from='c.example' to='a.example'> <db:result from='c.example' to='a.example'>
some-dialback-key some-dialback-key
</db:result> </db:result>
This element functions as Server B's assertion that it is (also) This element functions as Server 2's assertion that it is (also)
c.example, and thus is functionally equivalent to the 'from' address c.example, and thus is functionally equivalent to the 'from' address
of an initial stream header as previously described. of an initial stream header as previously described.
In response to this assertion, Server A needs to obtain some kind of In response to this assertion, Server 1 needs to obtain some kind of
proof that Server B really is also c.example. If the certificate proof that Server 2 really is also c.example. If the certificate
presented by Server B is also valid for c.example then no further presented by Server 2 is also valid for c.example then no further
action is necessary. However, if not then Server A needs to do a bit action is necessary. However, if not then Server 1 needs to do a bit
more work. Specifically, Server A can pursue the same strategy it more work. Specifically, Server 1 can pursue the same strategy it
used before: used before:
1. Server A resolves via DNS the service _xmpp- 1. Server 1 resolves via DNS the service _xmpp-
server._tcp.c.example. server._tcp.c.example.
2. Server A opens a TCP connection to the resolved IP address (which 2. Server 1 opens a TCP connection to the resolved IP address (which
might be the same IP address as for b.example). might be the same IP address as for b.example).
3. Server A sends an initial stream header to Server B, asserting 3. Server 1 sends an initial stream header to Server 2, asserting
that it is a.example: that it is a.example:
<stream:stream from='a.example' to='c.example'> <stream:stream from='a.example' to='c.example'>
4. Server B sends a response stream header to Server A, asserting 4. Server 2 sends a response stream header to Server 1, asserting
that it is c.example: that it is c.example:
<stream:stream from='c.example' to='a.example'> <stream:stream from='c.example' to='a.example'>
5. The servers attempt TLS negotiation, during which Server B 5. The servers attempt TLS negotiation, during which Server 2
(acting as a TLS server) presents a PKIX certificate proving that (acting as a TLS server) presents a PKIX certificate proving that
it is c.example. it is c.example.
6. At this point, Server A needs to establish that, despite 6. At this point, Server 1 needs to establish that, despite
different certificates, c.example is associated with the origin different certificates, c.example is associated with the origin
of the request. This is done using Server Dialback [XEP-0220]: of the request. This is done using Server Dialback [XEP-0220]:
<db:verify from='a.example' to='c.example' id='...'>some- <db:verify from='a.example' to='c.example' id='...'>some-
dialback-key</db:verify> dialback-key</db:verify>
7. Server B responds to this: 7. Server 2 responds to this:
<db:verify from='c.example' to='a.example' id='...' type='valid/> <db:verify from='c.example' to='a.example' id='...' type='valid/>
allowing Server A to establish the domain name association. allowing Server 1 to establish the domain name association.
Now that Server A accepts the domain name association, it informs Now that Server 1 accepts the domain name association, it informs
Server B of that fact: Server 2 of that fact:
<db:result from='a.example' to='c.example' type='valid'/> <db:result from='a.example' to='c.example' type='valid'/>
The parties can then terminate the second connection, since it was The parties can then terminate the second connection, since it was
used only for Server A to associate a stream with the domain name used only for Server 1 to associate a stream with the domain name
c.example (the dialback key links the original stream to the new c.example (the dialback key links the original stream to the new
association). association).
4.4.2. Supposition 4.4.2. Supposition
Piggybacking can also occur in the other direction. Consider the Piggybacking can also occur in the other direction. Consider the
common scenario in which Server A provides XMPP services not only for common scenario in which Server 1 provides XMPP services not only for
a.example but also for a subdomain such as a groupchat service (e.g., a.example but also for a subdomain such as a Multi-User Chat
Multi-User Chat [XEP-0045]) at rooms.a.example. If a user from [XEP-0045] service at rooms.a.example. If a user from c.example at
c.example at Server B wishes to join a room on the groupchat sevice, Server 2 wishes to join a room on the groupchat sevice, Server 2
Server B needs to send XMPP stanzas from the domain c.example to the needs to send XMPP stanzas from the domain c.example to the domain
domain rooms.a.example rather than a.example. First, Server B needs rooms.a.example rather than a.example.
to determine whether it can piggyback the domain rooms.a.example on
the connection to a.example:
1. Server B resolves vua DNS the service _xmpp- First, Server 2 needs to determine whether it can piggyback the
domain rooms.a.example on the connection to a.example:
1. Server 2 resolves vua DNS the service _xmpp-
server._tcp.rooms.a.example. server._tcp.rooms.a.example.
2. Server B determines this resolves to an IP address and port that 2. Server 2 determines this resolves to an IP address and port that
it is already connected to. it is already connected to.
3. Server B determines that the PKIX certificate for that active 3. Server 2 determines that the PKIX certificate for that active
connection would also be valid for the rooms.a.example domain and connection would also be valid for the rooms.a.example domain and
that Server A has announced support for dialback errors. that Server 1 has announced support for dialback errors.
Server B sends a dialback key to Server A over the existing Server 2 sends a dialback key to Server 1 over the existing
connection. connection.
<db:result from='c.example' to='rooms.a.example'> <db:result from='c.example' to='rooms.a.example'>
some-dialback-key some-dialback-key
</db:result> </db:result>
Server A then informs Server B that it accepts the domain name Server 1 then informs Server 2 that it accepts the domain name
association: association:
<db:result from='rooms.a.example' to='c.example' type='valid'/> <db:result from='rooms.a.example' to='c.example' type='valid'/>
5. Alternative Prooftypes 5. Alternative Prooftypes
The foregoing protocol flows assumed that domain name associations The foregoing protocol flows assumed that domain name associations
were proved using the PKI prooftype specified in [RFC6120]: that is, were proved using the PKIX prooftype. However, sometimes XMPP server
the server's proof consists of a PKIX certificate that is checked administrators are unable or unwilling to obtain valid PKIX
according to the XMPP profile [RFC6120] of the matching rules from certificates for all of the domains they host at their servers. For
[RFC6125] (and the overall validation rules from [RFC5280]), the example:
client's verification material is obtained out of band in the form of
a trusted root, and secure DNS is not necessary.
However, sometimes XMPP server administrators are unable or unwilling
to obtain valid PKIX certificates for all of the domains they host at
their servers. For example:
o In order to issue a PKIX certificate, a CA might try to send email o In order to issue a PKIX certificate, a CA might try to send email
messages to authoritative mailbox names [RFC2142], but the messages to authoritative mailbox names [RFC2142], but the
administrator of a subsidiary service such as im.cs.podunk.example administrator of a subsidiary service such as im.cs.podunk.example
cannot receive email sent to mailto:hostmaster@podunk.example. cannot receive email sent to mailto:hostmaster@podunk.example.
o A hosting provider such as hosting.example.net might not want to o A hosting provider such as hosting.example.net might not want to
take on the liability of holding the certificate and private key take on the liability of holding the certificate and private key
for a tenant such as example.com (or the tenant might not want the for a tenant such as example.com (or the tenant might not want the
hosting provider to hold its certificate and private key). hosting provider to hold its certificate and private key).
skipping to change at page 14, line 4 skipping to change at page 14, line 47
o A hosting provider such as hosting.example.net might not want to o A hosting provider such as hosting.example.net might not want to
take on the liability of holding the certificate and private key take on the liability of holding the certificate and private key
for a tenant such as example.com (or the tenant might not want the for a tenant such as example.com (or the tenant might not want the
hosting provider to hold its certificate and private key). hosting provider to hold its certificate and private key).
o Even if PKIX certificates for each tenant can be obtained, the o Even if PKIX certificates for each tenant can be obtained, the
management of so many certificates can introduce a large management of so many certificates can introduce a large
administrative load. administrative load.
(Additional discussion can be found in [I-D.ietf-xmpp-posh].) (Additional discussion can be found in [I-D.ietf-xmpp-posh].)
In these circumstances, prooftypes other than PKIX are desirable or In these circumstances, prooftypes other than PKIX are desirable or
necessary. As described below, two alternatives have been defined so necessary. As described below, two alternatives have been defined so
far: DNS-Based Authentication of Named Entities (DANE) and PKIX Over far: DNS-Based Authentication of Named Entities (DANE) and PKIX Over
Secure HTTP (POSH). Secure HTTP (POSH).
5.1. DANE 5.1. DANE
The DANE prooftype can be defined as follows: The DANE prooftype is defined as follows:
1. The server's proof consists of either a service certificate or 1. The server's proof consists of either a service certificate or
domain-issued certificate (TLSA usage PKIX-EE or DANE-EE, see domain-issued certificate (TLSA usage PKIX-EE or DANE-EE, see
[RFC6698] and [RFC7218]). [RFC6698] and [RFC7218]).
2. The proof is checked by verifying an exact match or a hash of 2. The proof is checked by verifying an exact match or a hash of
either the SubjectPublicKeyInfo or the full certificate. either the SubjectPublicKeyInfo or the full certificate.
3. The client's verification material is obtained via secure DNS 3. The client's verification material is obtained via secure DNS
[RFC4033] as described in [I-D.ietf-dane-srv]. [RFC4033] as described in [I-D.ietf-dane-srv].
4. Secure DNS is necessary in order to effectively establish an 4. Secure DNS is necessary in order to effectively establish an
alternative chain of trust from the service certificate or alternative chain of trust from the service certificate or
domain-issued certificate to the DNS root. domain-issued certificate to the DNS root.
The DANE prooftype makes use of the DNS-Based Authentication of Named The DANE prooftype makes use of DNS-Based Authentication of Named
Entities [RFC6698], specifically the use of DANE with DNS SRV records Entities [RFC6698], specifically the use of DANE with DNS SRV records
[I-D.ietf-dane-srv]. For XMPP purposes, the following rules apply: [I-D.ietf-dane-srv]. For XMPP purposes, the following rules apply:
o If there is no SRV resource record, pursue the fallback methods o If there is no SRV resource record, pursue the fallback methods
described in [RFC6120]. described in [RFC6120].
o Use the 'to' address of the initial stream header to determine the o Use the 'to' address of the initial stream header to determine the
domain name of the TLS client's reference identifier (since use of domain name of the TLS client's reference identifier (since use of
the Server Name Indication extension (TLS SNI) [RFC6066] is purely the Server Name Indication extension (TLS SNI) [RFC6066] is purely
discretionary in XMPP, as mentioned in [RFC6120]). discretionary in XMPP, as mentioned in [RFC6120]).
5.2. POSH 5.2. POSH
The POSH prooftype can be defined as follows: The POSH prooftype is defined as follows:
1. The server's proof consists of a PKIX certificate. 1. The server's proof consists of a PKIX certificate.
2. The proof is checked according to the rules from [RFC6120] and 2. The proof is checked according to the rules from [RFC6120] and
[RFC6125]. [RFC6125].
3. The client's verification material is obtained by retrieving a 3. The client's verification material is obtained by retrieving a
hash of the PKIX certificate over HTTPS at a well-known URI hash of the PKIX certificate over HTTPS at a well-known URI
[RFC5785]. [RFC5785].
4. Secure DNS is not necessary since the HTTPS retrieval mechanism 4. Secure DNS is not necessary since the HTTPS retrieval mechanism
relies on the chain of trust from the public key infrastructure. relies on the chain of trust from the public key infrastructure.
POSH is defined in [I-D.ietf-xmpp-posh]. For XMPP purposes, the POSH is defined in [I-D.ietf-xmpp-posh]. For XMPP purposes, the
following rules apply: following rules apply:
o If no verification materials are found via POSH, pursue the o If no verification material is found via POSH, pursue the fallback
fallback methods described in [RFC6120]. methods described in [RFC6120].
o Use the 'to' address of the initial stream header to determine the o Use the 'to' address of the initial stream header to determine the
domain name of the TLS client's reference identifier (since use of domain name of the TLS client's reference identifier (since use of
the Server Name Indication extension (TLS SNI) [RFC6066] is purely the Server Name Indication extension (TLS SNI) [RFC6066] is purely
discretionary in XMPP, as mentioned in [RFC6120]). discretionary in XMPP, as mentioned in [RFC6120]).
The well-known URIs [RFC5785] to be used for POSH are: The well-known URIs [RFC5785] to be used for POSH are:
o "/.well-known/posh._xmpp-client._tcp.json" for client-to-server o "/.well-known/posh/xmpp-client.json" for client-to-server
connections connections
o "/.well-known/posh._xmpp-server._tcp.json" for server-to-server o "/.well-known/posh/xmpp-server.json" for server-to-server
connections connections
6. Secure Delegation and Multi-Tenancy 6. Secure Delegation and Multi-Tenancy
One common method for deploying XMPP services is multi-tenancy: e.g., One common method for deploying XMPP services is multi-tenancy: e.g.,
XMPP services for the service domain example.com are actually hosted XMPP services for the service domain example.com are actually hosted
at the target server hosting.example.net. Such an arrangement is at the target server hosting.example.net. Such an arrangement is
relatively convenient in XMPP given the use of DNS SRV records relatively convenient in XMPP given the use of DNS SRV records
[RFC2782], such as the following delegation from example.com to [RFC2782], such as the following delegation from example.com to
hosting.example.net: hosting.example.net:
skipping to change at page 16, line 34 skipping to change at page 17, line 29
The PKIX, DANE, and POSH prooftypes adhere to this model. (Some The PKIX, DANE, and POSH prooftypes adhere to this model. (Some
prooftypes depend on, or are enhanced by, secure DNS [RFC4033] and prooftypes depend on, or are enhanced by, secure DNS [RFC4033] and
thus also need to describe how they ensure secure delegation.) thus also need to describe how they ensure secure delegation.)
Other prooftypes are possible; examples might include TLS with PGP Other prooftypes are possible; examples might include TLS with PGP
keys [RFC6091], a token mechanism such as Kerberos [RFC4120] or OAuth keys [RFC6091], a token mechanism such as Kerberos [RFC4120] or OAuth
[RFC6749], and Server Dialback keys [XEP-0220]. [RFC6749], and Server Dialback keys [XEP-0220].
Although the PKIX prooftype reuses the syntax of the XMPP Server Although the PKIX prooftype reuses the syntax of the XMPP Server
Dialback protocol [XEP-0220] for signalling between servers, this Dialback protocol [XEP-0220] for signaling between servers, this
framework document does not define how the generation and validation framework document does not define how the generation and validation
of Server Dialback keys (also specified in [XEP-0220]) is a DNA of Server Dialback keys (also specified in [XEP-0220]) is a DNA
prooftype. However, nothing in this document prevents the continued prooftype. However, nothing in this document prevents the continued
use of Server Dialback for signaling, and a future specification (or use of Server Dialback for signaling, and a future specification (or
an updated version of [XEP-0220]) might define a DNA prooftype for an updated version of [XEP-0220]) might define a DNA prooftype for
Server Dialback keys in a way that is consistent with this framework. Server Dialback keys in a way that is consistent with this framework.
8. IANA Considerations 8. Guidance for Server Operators
The POSH specification [I-D.ietf-xmpp-posh] provides guidelines for This document introduces the concept of a prooftype in order to
registering the well-known URIs [RFC5785] of protocols that make use explain and generalize the approach to establishing a strong
of POSH. This specification registers two such URIs, for which the association between the DNS domain name of an XMPP service and the
completed registration templates follow. XML stream that a client or peer server initiates with that service.
8.1. Well-Known URI for xmpp-client Service The operations and management implications of DNA prooftypes will
depend on the particular prooftypes that an operator supports. For
example:
This specification registers "posh._xmpp-client._tcp.json" in the o To support the PKIX prooftype [RFC6120], an operator needs to
Well-Known URI Registry as defined by [RFC5785]. obtain certificates for the XMPP server from a certification
authority (CA). However, DNS security is not required.
URI suffix: posh._xmpp-client._tcp.json o To support the DANE prooftype [I-D.ietf-dane-srv], an operator can
generate its own certificates for the XMPP server or obtain them
from a CA. In addition, DNS security is required.
o To support the POSH prooftype [I-D.ietf-xmpp-posh], an operator
can generate its own certificates for the XMPP server or obtain
them from a CA, but in addition needs to deploy the web server for
POSH files with certificates obtained from a CA. However, DNS
security is not required.
Considerations for use of the foregoing prooftypes are explained in
the relevant specifications. See in particular Section 13.7 of
[RFC6120], Section 6 of [I-D.ietf-dane-srv], and Section 8 of
[I-D.ietf-xmpp-posh].
Naturally, these operations and management considerations are
additive: if an operator wishes to use multiple prooftypes, the
complexity of deployment increases (e.g., the operator might want to
obtain a PKIX certificate from a certification authority for use in
the PKIX prooftype and generate its own certificate for use in the
DANE prooftype). This is an unavoidable aspect of supporting as many
prooftypes as needed in order to ensure that domain name associations
can be established in the largest possible percentage of cases.
9. IANA Considerations
The POSH specification [I-D.ietf-xmpp-posh] establishes a registry
for POSH service names to be used in well-known URIs [RFC5785]. This
specification registers two such URIs for use in XMPP: "xmpp-client"
and "xmpp-server". The completed registration templates follow.
9.1. POSH Service Name for xmpp-client Service
Service name: xmpp-client
Change controller: IETF Change controller: IETF
Specification document(s): [[ this document ]] Definition and usage: Specifies the location of a POSH file
containing verification material or a reference thereto that enables
a client to verify the identity of a server for a client-to-server
stream in XMPP
8.2. Well-Known URI for xmpp-server Service Specification: [[ this document ]]
This specification registers "posh._xmpp-server._tcp.json" in the 9.2. POSH Service Name for xmpp-server Service
Well-Known URI Registry as defined by [RFC5785].
URI suffix: posh._xmpp-server._tcp.json Service name: xmpp-server
Change controller: IETF Change controller: IETF
Specification document(s): [[ this document ]] Definition and usage: Specifies the location of a POSH file
containing verification material or a reference thereto that enables
a server to verify the identity of a peer server for a server-to-
server stream in XMPP
9. Security Considerations Specification: [[ this document ]]
10. Security Considerations
With regard to the PKIX prooftype, this document supplements but does With regard to the PKIX prooftype, this document supplements but does
not supersede the security considerations of [RFC6120] and [RFC6125]. not supersede the security considerations of [RFC6120] and [RFC6125].
With regard to the DANE and PKIX prooftypes, the reader is referred With regard to the DANE and PKIX prooftypes, the reader is referred
to [I-D.ietf-dane-srv] and [I-D.ietf-xmpp-posh], respectively. to [I-D.ietf-dane-srv] and [I-D.ietf-xmpp-posh], respectively.
Any future prooftypes need to thoroughly describe how they conform to Any future prooftypes need to thoroughly describe how they conform to
the prooftype model specified in Section 7 of this document. the prooftype model specified in Section 7 of this document.
10. References 11. References
10.1. Normative References 11.1. Normative References
[I-D.ietf-dane-srv] [I-D.ietf-dane-srv]
Finch, T., Miller, M., and P. Saint-Andre, "Using DNS- Finch, T., Miller, M., and P. Saint-Andre, "Using DNS-
Based Authentication of Named Entities (DANE) TLSA Records Based Authentication of Named Entities (DANE) TLSA Records
with SRV Records", draft-ietf-dane-srv-12 (work in with SRV Records", draft-ietf-dane-srv-14 (work in
progress), March 2015. progress), April 2015.
[I-D.ietf-xmpp-posh] [I-D.ietf-xmpp-posh]
Miller, M. and P. Saint-Andre, "PKIX over Secure HTTP Miller, M. and P. Saint-Andre, "PKIX over Secure HTTP
(POSH)", draft-ietf-xmpp-posh-04 (work in progress), (POSH)", draft-ietf-xmpp-posh-04 (work in progress),
February 2015. February 2015.
[RFC1034] Mockapetris, P., "Domain names - concepts and facilities", [RFC1034] Mockapetris, P., "Domain names - concepts and facilities",
STD 13, RFC 1034, November 1987. STD 13, RFC 1034, DOI 10.17487/RFC1034, November 1987,
<http://www.rfc-editor.org/info/rfc1034>.
[RFC1035] Mockapetris, P., "Domain names - implementation and [RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987. specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <http://www.rfc-editor.org/info/rfc1035>.
[RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for [RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
specifying the location of services (DNS SRV)", RFC 2782, specifying the location of services (DNS SRV)", RFC 2782,
February 2000. DOI 10.17487/RFC2782, February 2000,
<http://www.rfc-editor.org/info/rfc2782>.
[RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S. [RFC4033] Arends, R., Austein, R., Larson, M., Massey, D., and S.
Rose, "DNS Security Introduction and Requirements", RFC Rose, "DNS Security Introduction and Requirements", RFC
4033, March 2005. 4033, DOI 10.17487/RFC4033, March 2005,
<http://www.rfc-editor.org/info/rfc4033>.
[RFC4949] Shirey, R., "Internet Security Glossary, Version 2", RFC [RFC4422] Melnikov, A., Ed. and K. Zeilenga, Ed., "Simple
4949, August 2007. Authentication and Security Layer (SASL)", RFC 4422, DOI
10.17487/RFC4422, June 2006,
<http://www.rfc-editor.org/info/rfc4422>.
[RFC4949] Shirey, R., "Internet Security Glossary, Version 2", FYI
36, RFC 4949, DOI 10.17487/RFC4949, August 2007,
<http://www.rfc-editor.org/info/rfc4949>.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, May 2008. (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008,
<http://www.rfc-editor.org/info/rfc5280>.
[RFC5785] Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known [RFC5785] Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known
Uniform Resource Identifiers (URIs)", RFC 5785, April Uniform Resource Identifiers (URIs)", RFC 5785, DOI
2010. 10.17487/RFC5785, April 2010,
<http://www.rfc-editor.org/info/rfc5785>.
[RFC6120] Saint-Andre, P., "Extensible Messaging and Presence [RFC6120] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Core", RFC 6120, March 2011. Protocol (XMPP): Core", RFC 6120, DOI 10.17487/RFC6120,
March 2011, <http://www.rfc-editor.org/info/rfc6120>.
[RFC6125] Saint-Andre, P. and J. Hodges, "Representation and [RFC6125] Saint-Andre, P. and J. Hodges, "Representation and
Verification of Domain-Based Application Service Identity Verification of Domain-Based Application Service Identity
within Internet Public Key Infrastructure Using X.509 within Internet Public Key Infrastructure Using X.509
(PKIX) Certificates in the Context of Transport Layer (PKIX) Certificates in the Context of Transport Layer
Security (TLS)", RFC 6125, March 2011. Security (TLS)", RFC 6125, DOI 10.17487/RFC6125, March
2011, <http://www.rfc-editor.org/info/rfc6125>.
[RFC6698] Hoffman, P. and J. Schlyter, "The DNS-Based Authentication [RFC6698] Hoffman, P. and J. Schlyter, "The DNS-Based Authentication
of Named Entities (DANE) Transport Layer Security (TLS) of Named Entities (DANE) Transport Layer Security (TLS)
Protocol: TLSA", RFC 6698, August 2012. Protocol: TLSA", RFC 6698, DOI 10.17487/RFC6698, August
2012, <http://www.rfc-editor.org/info/rfc6698>.
[RFC7218] Gudmundsson, O., "Adding Acronyms to Simplify [RFC7218] Gudmundsson, O., "Adding Acronyms to Simplify
Conversations about DNS-Based Authentication of Named Conversations about DNS-Based Authentication of Named
Entities (DANE)", RFC 7218, April 2014. Entities (DANE)", RFC 7218, DOI 10.17487/RFC7218, April
2014, <http://www.rfc-editor.org/info/rfc7218>.
[XEP-0220] [XEP-0220]
Miller, J., Saint-Andre, P., and P. Hancke, "Server Miller, J., Saint-Andre, P., and P. Hancke, "Server
Dialback", XSF XEP 0220, August 2014. Dialback", XSF XEP 0220, August 2014.
10.2. Informative References 11.2. Informative References
[I-D.ietf-uta-xmpp]
Saint-Andre, P. and a. alkemade, "Use of Transport Layer
Security (TLS) in the Extensible Messaging and Presence
Protocol (XMPP)", draft-ietf-uta-xmpp-05 (work in
progress), January 2015.
[RFC2142] Crocker, D., "MAILBOX NAMES FOR COMMON SERVICES, ROLES AND [RFC2142] Crocker, D., "Mailbox Names for Common Services, Roles and
FUNCTIONS", RFC 2142, May 1997. Functions", RFC 2142, DOI 10.17487/RFC2142, May 1997,
<http://www.rfc-editor.org/info/rfc2142>.
[RFC3920] Saint-Andre, P., Ed., "Extensible Messaging and Presence [RFC3920] Saint-Andre, P., Ed., "Extensible Messaging and Presence
Protocol (XMPP): Core", RFC 3920, October 2004. Protocol (XMPP): Core", RFC 3920, DOI 10.17487/RFC3920,
October 2004, <http://www.rfc-editor.org/info/rfc3920>.
[RFC4120] Neuman, C., Yu, T., Hartman, S., and K. Raeburn, "The [RFC4120] Neuman, C., Yu, T., Hartman, S., and K. Raeburn, "The
Kerberos Network Authentication Service (V5)", RFC 4120, Kerberos Network Authentication Service (V5)", RFC 4120,
July 2005. DOI 10.17487/RFC4120, July 2005,
<http://www.rfc-editor.org/info/rfc4120>.
[RFC6066] Eastlake, D., "Transport Layer Security (TLS) Extensions: [RFC6066] Eastlake 3rd, D., "Transport Layer Security (TLS)
Extension Definitions", RFC 6066, January 2011. Extensions: Extension Definitions", RFC 6066, DOI
10.17487/RFC6066, January 2011,
<http://www.rfc-editor.org/info/rfc6066>.
[RFC6091] Mavrogiannopoulos, N. and D. Gillmor, "Using OpenPGP Keys [RFC6091] Mavrogiannopoulos, N. and D. Gillmor, "Using OpenPGP Keys
for Transport Layer Security (TLS) Authentication", RFC for Transport Layer Security (TLS) Authentication", RFC
6091, February 2011. 6091, DOI 10.17487/RFC6091, February 2011,
<http://www.rfc-editor.org/info/rfc6091>.
[RFC6749] Hardt, D., "The OAuth 2.0 Authorization Framework", RFC [RFC6749] Hardt, D., Ed., "The OAuth 2.0 Authorization Framework",
6749, October 2012. RFC 6749, DOI 10.17487/RFC6749, October 2012,
<http://www.rfc-editor.org/info/rfc6749>.
[RFC7590] Saint-Andre, P. and T. Alkemade, "Use of Transport Layer
Security (TLS) in the Extensible Messaging and Presence
Protocol (XMPP)", RFC 7590, DOI 10.17487/RFC7590, June
2015, <http://www.rfc-editor.org/info/rfc7590>.
[XEP-0045] [XEP-0045]
Saint-Andre, P., "Multi-User Chat", XSF XEP 0045, February Saint-Andre, P., "Multi-User Chat", XSF XEP 0045, February
2012. 2012.
[XEP-0288] [XEP-0288]
Hancke, P. and D. Cridland, "Bidirectional Server-to- Hancke, P. and D. Cridland, "Bidirectional Server-to-
Server Connections", XSF XEP 0288, September 2013. Server Connections", XSF XEP 0288, September 2013.
[XEP-0344] [XEP-0344]
Hancke, P. and D. Cridland, "Impact of TLS and DNSSEC on Hancke, P. and D. Cridland, "Impact of TLS and DNSSEC on
Dialback", XSF XEP 0344, March 2015. Dialback", XSF XEP 0344, March 2015.
Appendix A. Acknowledgements Appendix A. Acknowledgements
Thanks to Richard Barnes, Stephen Farrell, and Jonas Lindberg for Richard Barnes, Stephen Farrell, and Jonas Lindberg contributed as
contributing to earlier versions of this document. co-authors to earlier draft versions of this document.
Derek Atkins, Mahesh Jethanandani, and Dan Romascanu reviewed the
document on behalf of the Security Directorate, the Operations and
Management Directorate, and the General Area Review Team,
respectively.
During IESG review, Stephen Farrell and Barry Leiba provided helpful
input that led to improvements in the specification.
Thanks to Dave Cridland as document shepherd, Joe Hildebrand as
working group chair, and Ben Campbell as area director.
Peter Saint-Andre wishes to acknowledge Cisco Systems, Inc., for
employing him during his work on earlier draft versions of this
document.
Authors' Addresses Authors' Addresses
Peter Saint-Andre Peter Saint-Andre
&yet &yet
Email: peter@andyet.com Email: peter@andyet.com
URI: https://andyet.com/ URI: https://andyet.com/
Matthew Miller Matthew Miller
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