# XEP-xxxx: Token-based reconnection

Abstract: | This specification defines a token-based session authentication mechanism.
Authors: | Michał Piotrowski, Radosław Szymczyszyn
Copyright: | © 1999 - 2015 XMPP Standards Foundation. SEE LEGAL NOTICES.
Status: | ProtoXEP
Type: | Standards Track
Version: | 0.0.1
Last Updated: | 2016-02-04

WARNING: This document has not yet been accepted for consideration or approved in any official manner by the XMPP Standards Foundation, and this document is not yet an XMPP Extension Protocol (XEP). If this document is accepted as a XEP by the XMPP Council, it will be published at <http://xmpp.org/extensions/> and announced on the <standards@xmpp.org> mailing list.

## Table of Contents

1. Introduction
2. Requirements
3. Glossary
3.1. Token types
3.2. Token format
3.2.1. Access token format
3.2.2. Refresh token format
4. Use Cases
4.1. Obtaining a token
4.2. Authentication with an access token
4.3. Authentication with a refresh token
5. Business Rules
6. Implementation Notes
7. Security Considerations
8. IANA Considerations
9. XMPP Registrar Considerations
10. XML Schema

Appendices
A: Document Information
B: Author Information
C: Legal Notices
D: Relation to XMPP
E: Discussion Venue
F: Requirements Conformance
G: Notes
H: Revision History

## 1. Introduction

Automatic reconnection after spurious disconnection is a must-have feature in modern IM applications. One way of providing this feature is storing user login information on disk for reuse. However, plaintext storage of passwords is inherently insecure, while protecting the XMPP password with a master-password is inconvenient for the end-user. With a token-based authentication mechanism, the user only has to provide login information once, for the initial connection to the XMPP server, and can later rely on the application's automatic use of tokens for subsequent reconnections.

Moreover, while reconnecting to the XMPP server, the client usually has to go through the same long process of SASL challenge-response exchange which may lead to a noticeably long reconnection time, especially while using SCRAM-based mechanisms. Providing a token to the XMPP server is both secure and doesn't require multiple challenge-response roundtrips, therefore might significantly speed up reconnection times.

## 2. Requirements

This extension requires the client application to authenticate to the XMPP server using a regular XMPP authentication mechanism like SCRAM-SHA-1 at least once. After that, the following authentications may be done using X-OAUTH SASL mechanism with a token obtained from the server.

## 3. Glossary

### 3.1 Token types

Table 1: Token types

Token Type | Description
--- | ---
Access token | These are short lived tokens whose grants aren't tracked by the server (i.e. there's no need to store anything in a database). Access tokens can be used as a payload for the X-OAUTH authentication mechanism and grant access to the system. Access tokens can't be revoked. An access token is valid only until its expiry date is reached.
Refresh token | These are longer lived tokens which are tracked by the server, therefore require persistent storage. Refresh tokens can be used as a payload for the X-OAUTH authentication mechanism and grant access to the system, as well as result in a new set of tokens being returned upon successful authentication. Refresh tokens can be revoked. A refresh token is valid until it has expired, unless it has been revoked. On revocation, it immediately becomes invalid. As the server stores information about granted tokens, it can also persistently mark them as revoked.

While only two token types have been described above, implementations might use other token types for specific purposes. For example, a particular token type could limit the access privileges of a user logged into the system or denote an affiliation with a Multi User Chat room. None of such capability grants are subject of this specification, though.

### 3.2 Token format

This section is informal. The token formats described below are used in one of the experimental implementations, but are not proposed as standard. If such a standard turns out to be required, then JSON Web Tokens might be a viable format to adopt.

All tokens are exchanged as Base64 encoded binary data. Serialization format of the token before encoding with Base64 is dependent on its type. Common parts in every token are `BARE_JID` and `EXPIRES_AT`. `EXPIRES_AT` is a timestamp saying when given token will expire. `\0` stands for the ASCII null character (i.e. byte 0). Text in single quotes (`'example'`) is literal. `ALL_CAPS` denote parameters.

### 3.2.1 Access token format

    BASE64_encode
            ('access', \0, BARE_JID, \0, EXPIRES_AT, \0, DATA)

Example, please note the line break was added only for readability:

    'access' \0 Q8@wonderland.com \0 64875466454
        \0 0acd0a66d06934791d046060cf9f1ad3c2abb3274cc7e7d7b2bc7e2ac4453ed774b6c6813b40ebec2bbc3774d59d4087

### 3.2.2 Refresh token format

    BASE64_encode
            ('refresh', \0, BARE_JID, \0, EXPIRES_AT, \0, SEQUENCE_NO, \0, DATA)

Example, please note the line break was added only for readability:

    'refresh' \0 qp@wonderland.com \0 64875466457 \0 6
        \0 8f57cb019cd6dc6e7779be165b9558611baf71ee4a40d03e77b78b069f482f96c9d23b1ac1ef69f64c1a1db3d36a96ad

## 4. Use Cases

### 4.1 Obtaining a token

After authentication with some other mechanism like SCRAM-SHA-1, a client may request a token from the server by sending following iq get to its own bare JID:

Example 1. Client requests tokens

    <iq type='get' to='alice@wonderland.com' id='123'>
        <query xmlns='erlang-solutions.com:xmpp:token-auth:0'/>
    </iq>

Example 2. Servers responds with tokens

    <iq from="alice@wonderland.com" type="result" to="alice@wonderland.com/resource" id="123">
      <items xmlns="erlang-solutions.com:xmpp:token-auth:0">
        <access_token>YWNjZXNzAGFsaWNlQHdvbmRlcmxhbmQuY29tL01pY2hhbC1QaW90cm93c2tpcy1NYWNCb29rLVBybwA2MzYyMTg4Mzc2NAA4M2QwNzNiZjBkOGJlYzVjZmNkODgyY2ZlMzkyZWM5NGIzZjA4ODNlNDI4ZjQzYjc5MGYxOWViM2I2ZWJlNDc0ODc3MDkxZTIyN2RhOGMwYTk2ZTc5ODBhNjM5NjE1Zjk=</access_token>
        <refresh_token>cmVmcmVzaABhbGljZUB3b25kZXJsYW5kLmNvbS9NaWNoYWwtUGlvdHJvd3NraXMtTWFjQm9vay1Qcm8ANjM2MjMwMDYxODQAMQAwZGQxOGJjODhkMGQ0N2MzNTBkYzAwYjcxZjMyZDVmOWIwOTljMmI1ODU5MmNhN2QxZGFmNWFkNGM0NDQ2ZGU2MWYxYzdhNTJjNDUyMGI5YmIxNGIxNTMwMTE4YTM1NTc=</refresh_token>
      </items>
    </iq>

### 4.2 Authentication with an access token

Example 3. Client authenticates with access token

    <auth xmlns="urn:ietf:params:xml:ns:xmpp-sasl" mechanism="X-OAUTH">
    YWNjZXNzAGFsaWNlQHdvbmRlcmxhbmQuY29tL01pY2hhbC1QaW90cm93c2tpcy1NYWNCb29rLVBybwA2MzYyMTg4Mzc2NAA4M2QwNzNiZjBkOGJlYzVjZmNkODgyY2ZlMzkyZWM5NGIzZjA4ODNlNDI4ZjQzYjc5MGYxOWViM2I2ZWJlNDc0ODc3MDkxZTIyN2RhOGMwYTk2ZTc5ODBhNjM5NjE1Zjk=
    </auth>

Example 4. Server responds with success

    <success xmlns="urn:ietf:params:xml:ns:xmpp-sasl"/>

### 4.3 Authentication with a refresh token

In this situation server will respond with a new refresh token which SHOULD be used in future authentication.

Example 5. Client authenticates with refresh token

    <auth xmlns="urn:ietf:params:xml:ns:xmpp-sasl" mechanism="X-OAUTH">
    cmVmcmVzaABhbGljZUB3b25kZXJsYW5kLmNvbS9NaWNoYWwtUGlvdHJvd3NraXMtTWFjQm9vay1Qcm8ANjM2MjMwMDYxODQAMQAwZGQxOGJjODhkMGQ0N2MzNTBkYzAwYjcxZjMyZDVmOWIwOTljMmI1ODU5MmNhN2QxZGFmNWFkNGM0NDQ2ZGU2MWYxYzdhNTJjNDUyMGI5YmIxNGIxNTMwMTE4YTM1NTc=
    </auth>

Example 6. Server responds with success and new refresh token

    <success xmlns="urn:ietf:params:xml:ns:xmpp-sasl">
    cmVmcmVzaABhbGljZUB3b25kZXJsYW5kLmNvbS9NaWNoYWwtUGlvdHJvd3NraXMtTWFjQm9vay1Qcm8ANjM2MjMwMDYxODQAMgAwZGQxOGJjODhkMGQ0N2MzNTBkYzAwYjcxZjMyZDVmOWIwOTljMmI1ODU5MmNhN2QxZGFmNWFkNGM0NDQ2ZGU2MWYxYzdhNTJjNDUyMGI5YmIxNGIxNTMwMTE4YTM1NTc=
    </success>

## 5. Business Rules

A classical authentication is required in order to be able to use a token-based authentication later.

## 6. Implementation Notes

The DATA field in token is relevant only to the XMPP server supporting this extension.

## 7. Security Considerations

The tokens MUST be exchanged over a secured/encrypted C2S stream (via TLS, for example).

## 8. IANA Considerations

This document requires no interaction with the Internet Assigned Numbers Authority (IANA) [1].

## 9. XMPP Registrar Considerations

This document requires no interaction with the XMPP Registrar [2].

## 10. XML Schema

REQUIRED for protocol specifications.

## Appendices

### Appendix A: Document Information

Series: XEP
Number: xxxx
Publisher: XMPP Standards Foundation
Status: ProtoXEP
Type: Standards Track
Version: 0.0.1
Last Updated: 2016-02-04
Approving Body: XMPP Council
Dependencies: XMPP Core, XEP-0001
Supersedes: None
Superseded By: None
Short Name: NOT_YET_ASSIGNED
This document in other formats: XML PDF

### Appendix B: Author Information

### Michał Piotrowski

Email: michal.piotrowski@erlang-solutions.com

### Radosław Szymczyszyn

Email: radoslaw.szymczyszyn@erlang-solutions.com

### Appendix C: Legal Notices

#### Copyright

This XMPP Extension Protocol is copyright (c) 1999 - 2016 by the XMPP Standards Foundation (XSF).

#### Permissions

Permission is hereby granted, free of charge, to any person obtaining a copy of this specification (the "Specification"), to make use of the Specification without restriction, including without limitation the rights to implement the Specification in a software program, deploy the Specification in a network service, and copy, modify, merge, publish, translate, distribute, sublicense, or sell copies of the Specification, and to permit persons to whom the Specification is furnished to do so, subject to the condition that the foregoing copyright notice and this permission notice shall be included in all copies or substantial portions of the Specification. Unless separate permission is granted, modified works that are redistributed shall not contain misleading information regarding the authors, title, number, or publisher of the Specification, and shall not claim endorsement of the modified works by the authors, any organization or project to which the authors belong, or the XMPP Standards Foundation.

#### Disclaimer of Warranty

## NOTE WELL: This Specification is provided on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, express or implied, including, without limitation, any warranties or conditions of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A PARTICULAR PURPOSE. In no event shall the XMPP Standards Foundation or the authors of this Specification be liable for any claim, damages, or other liability, whether in an action of contract, tort, or otherwise, arising from, out of, or in connection with the Specification or the implementation, deployment, or other use of the Specification. ##

#### Limitation of Liability

In no event and under no legal theory, whether in tort (including negligence), contract, or otherwise, unless required by applicable law (such as deliberate and grossly negligent acts) or agreed to in writing, shall the XMPP Standards Foundation or any author of this Specification be liable for damages, including any direct, indirect, special, incidental, or consequential damages of any character arising out of the use or inability to use the Specification (including but not limited to damages for loss of goodwill, work stoppage, computer failure or malfunction, or any and all other commercial damages or losses), even if the XMPP Standards Foundation or such author has been advised of the possibility of such damages.

#### IPR Conformance

This XMPP Extension Protocol has been contributed in full conformance with the XSF's Intellectual Property Rights Policy (a copy of which may be found at <http://xmpp.org/extensions/ipr-policy.shtml> or obtained by writing to XSF, P.O. Box 1641, Denver, CO 80201 USA).

### Appendix D: Relation to XMPP

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.

### Appendix E: Discussion Venue

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 <http://xmpp.org/about/discuss.shtml> for a complete list.

Errata can be sent to <editor@xmpp.org>.

### Appendix F: Requirements Conformance

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".

### Appendix G: Notes

1. 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/>.

2. 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 <http://xmpp.org/registrar/>.

### Appendix H: Revision History

Note: Older versions of this specification might be available at http://xmpp.org/extensions/attic/

#### Version 0.0.1 (2016-02-04)

First draft.

(mp)

END