This document defines a protocol that enables verification of an HTTP request via XMPP.
NOTICE: This JEP is currently within Last Call or under consideration by the Jabber Council for advancement to the next stage in the JSF standards process. For further details, visit <http://www.jabber.org/council/queue.shtml>.
Status: Proposed
Type: Standards Track
Number: 0070
Version: 0.10
Last Updated: 2005-12-01
JIG: Standards JIG
Approving Body: Jabber Council
Dependencies: XMPP Core, RFC 2616, RFC 2617, JEP-0030
Supersedes: None
Superseded By: None
Short Name: http-auth
Wiki Page: <http://wiki.jabber.org/index.php/Verifying HTTP Requests via XMPP (JEP-0070)>
Email: linuxwolf@outer-planes.net
JID: linuxwolf@outer-planes.net
Email: jhildebrand@jabber.com
JID: hildjj@jabber.org
Email: dizzyd@jabber.org
JID: dizzyd@jabber.org
Email: stpeter@jabber.org
JID: stpeter@jabber.org
This Jabber Enhancement Proposal is copyright 1999 - 2005 by the Jabber Software Foundation (JSF) and is in full conformance with the JSF's Intellectual Property Rights Policy <http://www.jabber.org/jsf/ipr-policy.shtml>. This material may be distributed only subject to the terms and conditions set forth in the Creative Commons Attribution License (<http://creativecommons.org/licenses/by/2.5/>).
The preferred venue for discussion of this document is the Standards-JIG discussion list: <http://mail.jabber.org/mailman/listinfo/standards-jig>.
Given that this JEP normatively references IETF technologies, discussion on the JSF-IETF list may also be appropriate (see <http://mail.jabber.org/mailman/listinfo/jsf-ietf> for details).
The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 3920) and XMPP IM (RFC 3921) specifications contributed by the Jabber Software 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 JEP 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.
The keywords "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.
HTTP (see RFC 2616 [1]) is a nearly-ubiquitous mechanism for the publication and retrieval of information over the Internet. Sometimes it is appropriate for an HTTP Server to allow access to that information only if the HTTP Client first provides authentication credentials. While there exist several standardized HTTP authentication schemes (see RFC 2617 [2]), it may be useful in some applications to enforce verification of an HTTP request by requiring an XMPP entity (normally an IM user) to confirm that it made the request. This request verification can be combined with native HTTP authentication to provide a stronger association between the request and a particular user, as well as to take advantage of the strong user authentication provided in XMPP (see RFC 3920 [3]).
This document inherits terminology about the HyperText Transfer Protocol from RFC 2616 and RFC 2617.
Table 1: Terms for Entities Described Herein
| Term | Definition |
|---|---|
| HTTP Client | A client that implements the HyperText Transfer Protocol (HTTP) |
| HTTP Server | A server that implements the HyperText Transfer Protocol (HTTP) |
| XMPP Client | A client that implements the Extensible Messaging and Presence Protocol (XMPP) or its antecedents |
| XMPP Server | A server that implements the Extensible Messaging and Presence Protocol (XMPP) or its antecedents |
Note well that an XMPP Client can simultaneously be an HTTP Client (or vice-versa), and that an XMPP Server can simultaneously be an HTTP Server (or vice-versa). However, for the purposes of this discussion, we assume that these entities are logically if not physically separate and distinct.
The motivations for this document are to:
The process flow for this protocol is as follows:
Error cases:
This process flow is described in more detail in the following sections.
Let us stipulate that an XMPP user (say, <juliet@capulet.com>) learns of an HTTP URL (e.g., <https://files.shakespeare.lit:9345/missive.html>). The user then attempts to retrieve the URL using her HTTP Client, which opens a TCP connection to the appropriate port of the host and sends an HTTP request as defined in RFC 2616. The request method MAY be any valid HTTP request method, including user-defined methods.
An example is provided below:
Example 1. HTTP Client Makes Request (No Credentials)
GET https://files.shakespeare.lit:9345/missive.html HTTP/1.1
In order to avoid a round trip, the initial request MAY contain HTTP authorization credentials as described below.
If the user did not provide authorization credentials in the initial request, the HTTP Server then MUST respond with a (401) Authenticate response as defined in RFC 2616. The response MUST contain an HTTP 401 error and one WWW-Authenticate header for each authentication scheme recognized by the HTTP Server. In order to provide verification via XMPP, at least one of these headers MUST specify a realm of "xmpp" (case-sensitive).
Example 2. HTTP Server Returns Authenticate Response
401 Unauthorized HTTP/1.1
WWW-Authenticate: Basic realm="xmpp"
WWW-Authenticate: Digest realm="xmpp",
domain="files.shakespeare.lit",
stale=false,
nonce="ec2cc00f21f71acd35ab9be057970609",
qop="auth",
algorithm="MD5"
The HTTP Client responds with an Authorization Request as defined in RFC 2616. The following rules apply:
The Authorization Request process is described in the following subsections.
The Basic Access Authentication scheme is defined in RFC 2617. This scheme specifies that the authorization information shall consist of a userid and password, separated by a ':' character and then encoded using Base64. When the realm is "xmpp", the profile defined herein further specifies that the userid MUST be a valid JID as described above, that the password entity MUST be a transaction identifier as described above, that any character in the JID or transaction identifier that is outside the range of the US-ASCII coded character set MUST be transformed into a percent-encoded octet as specified in Section 2.1 of RFC 3986 [5] prior to Base64 encoding, and that Base64 encoding MUST adhere to Section 3 of RFC 3548 [6].
(Refer to RFC 2617 for specification of the syntax of the Basic Access Authentication scheme; that information is not duplicated here.)
Example 3. HTTP Client Makes Basic Authorization Request
Authorization: Basic QWxhZGRpbjpvcGVuIHNlc2FtZQ==
The Digest Access Authentication scheme is defined in RFC 2617. This scheme specifies that the authorization information shall consist of the MD5 checksum of the username, the password, a nonce value provided in the challenge, the HTTP method, and the requested URL. When the realm is "xmpp", the profile defined herein further specifies that prior to creating the MD5 checksum the username MUST be a valid JID as described above, that the password MUST be a transaction identifier as described above, and that any character in the JID or transaction identifier that is outside the range of the US-ASCII coded character set MUST be transformed into a percent-encoded octet as specified in Section 2.1 of RFC 3986.
(Refer to RFC 2617 for specification of the syntax of the Digest Access Authentication scheme; that information is not duplicated here.)
Example 4. HTTP Client Makes Digest Authorization Request
Authorization: Digest username="juliet@capulet.com",
realm="xmpp",
nonce="ec2cc00f21f71acd35ab9be057970609",
uri="missive.html",
qop=auth,
nc=00000001,
cnonce="0a4f113b",
response="6629fae49393a05397450978507c4ef1",
opaque="5ccc069c403ebaf9f0171e9517f40e41"
The HTTP Server MAY offer any other valid authentication scheme, instead of or in addition to the Basic and Digest schemes mentioned above, as long as the scheme makes it possible to specify a userid (JID) and transaction identifier as described above. However, it is RECOMMENDED to implement both the Basic and Digest authentication schemes.
Once the HTTP Client has communicated the JID and transaction identifier to the HTTP Server, the HTTP Server MUST verify that the JID is authorized to access the HTTP resource. This may involve JID-level or domain-level access checks, or (depending on local service policies) potentially no access checks at all if only verification is required.
If the JID is authorized to access the HTTP resource, the HTTP Server MUST pass the URL, method, JID, and transaction identifier to the XMPP Server for confirmation. Exactly how this is done is up to the implementation. It is RECOMMENDED for the HTTP Server to connect to the XMPP Server as a trusted server component and to itself generate the confirmation request as described below.
Upon receiving the JID and transaction identifier from the HTTP Server, the XMPP Server MUST send a confirmation request (via XMPP) to the XMPP Client (or route the confirmation request generated by the HTTP Server acting as a trusted XMPP server component).
The confirmation request shall consist of an empty <confirm/> element qualified by the ''http://jabber.org/protocol/http-auth' namespace. This element MUST possess a 'method' attribute whose value is the method of the HTTP request, MUST possess a 'url' attribute whose value is the full HTTP URL that was requested, and MUST possess an 'id' attribute whose value is the transaction identifier provided in the HTTP Authorization Request.
If the JID provided was a full JID, the confirmation request SHOULD be sent in an <iq/> stanza of type "get" whose 'to' attribute is set to the full JID, but MAY be sent in a <message/> stanza.
If the JID provided was a bare JID, the confirmation request MUST be sent in a <message/> stanza whose 'to' attribute is set to the bare JID; this enables delivery to the "most available" resource for the user (however "most available" is determined by the XMPP Server). The <message/> stanza SHOULD include a <thread/> element for tracking purposes and MAY include a <body/> element that provides human-readable information or instructions.
Example 5. Confirmation Request Sent via IQ
<iq type='get'
from='files.shakespeare.lit'
to='juliet@capulet.com/balcony'
id='ha000'>
<confirm xmlns='http://jabber.org/protocol/http-auth'
id='transaction-identifier'
method='GET'
url='https://files.shakespeare.lit:9345/missive.html'/>
</iq>
Example 6. Confirmation Request Sent via Message
<message type='normal'
from='files.shakespeare.lit'
to='juliet@capulet.com'>
<thread>e0ffe42b28561960c6b12b944a092794b9683a38</thread>
<body>
Someone (maybe you) has requested the file
https://files.shakespeare.lit:9345/missive.html.
If you wish to confirm the request, please reply
to this message by typing "OK". If not, please
reply with "No".
</body>
<confirm xmlns='http://jabber.org/protocol/http-auth'
id='transaction-identifier'
method='GET'
url='https://files.shakespeare.lit:9345/missive.html'/>
</message>
If the confirmation request was provided via an <iq/> stanza, the XMPP Client MUST respond to the request by sending an <iq/> stanza back to the XMPP Server. If the user wishes to confirm the request, the <iq/> response stanza MUST be of type "result" and MAY contain the original <confirm/> child element (although this is not necessary since the XMPP 'id' attribute can be used for tracking purposes):
Example 7. XMPP Client Confirms Request via IQ
<iq type='result'
from='juliet@capulet.com/balcony'
to='files.shakespeare.lit'
id='ha000'/>
If the user wishes to deny the request, the <iq/> response stanza MUST be of type "error", MAY contain the original <confirm/> child element (although this is not necessary since the XMPP 'id' attribute can be used for tracking purposes), and MUST specify an error, which SHOULD be <not-authorized/>:
Example 8. XMPP Client Denies Request via IQ
<iq type='error'
from='juliet@capulet.com/balcony'
to='files.shakespeare.lit'
id='ha000'>
<confirm xmlns='http://jabber.org/protocol/http-auth'
id='transaction-identifier'
method='GET'
url='https://files.shakespeare.lit:9345/missive.html'/>
<error code='401' type='auth'>
<not-authorized xmlns='urn:ietf:params:xml:xmpp-stanzas'/>
</error>
</iq>
If the confirmation request was provided via a <message/> stanza and the <message/> contains a human-readable <body/> or does not contain a <body/> but the XMPP Client understands the 'http://jabber.org/protocol/http-auth' namespace, the XMPP Client SHOULD respond to the request by sending a <message/> stanza back to the XMPP Server. If the user wishes to confirm the request, the <message/> response stanza SHOULD be of type "normal", MUST mirror the <thread/> ID (if provided by the XMPP Server), and MUST contain the original <confirm/> child element:
Example 9. XMPP Client Confirms Request via Message
<message from='juliet@capulet.com/balcony'
to='files.shakespeare.lit'>
<thread>e0ffe42b28561960c6b12b944a092794b9683a38</thread>
<confirm xmlns='http://jabber.org/protocol/http-auth'
id='transaction-identifier'
method='GET'
url='https://files.shakespeare.lit:9345/missive.html'/>
</message>
If the user wishes to deny the request, the <message/> response stanza MUST be of type "error", MUST mirror the <thread/> ID (if provided by the XMPP Server), MUST contain the original <confirm/> child element, and MUST specify an error, which SHOULD be <not-authorized/>:
Example 10. XMPP Client Denies Request via Message
<message type='error'
from='juliet@capulet.com/balcony'
to='files.shakespeare.lit'>
<thread>e0ffe42b28561960c6b12b944a092794b9683a38</thread>
<confirm xmlns='http://jabber.org/protocol/http-auth'
id='transaction-identifier'
method='GET'
url='https://files.shakespeare.lit:9345/missive.html'/>
<error code='401' type='auth'>
<not-authorized xmlns='urn:ietf:params:xml:xmpp-stanzas'/>
</error>
</message>
Once the XMPP Client has successfully confirmed the request, the XMPP Server forwards that confirmation to the HTTP Server, which allows access:
Example 11. HTTP Server Allows Access to Object
200 OK HTTP/1.1
Content-Type: text/html
Content-Length: 3032
...
If the XMPP Client denied the request, the HTTP Server MUST return a Forbidden error:
Example 12. HTTP Server Denies Access to Object
403 Forbidden HTTP/1.1
For the HEAD and OPTIONS methods, the credentials SHOULD be usable for a subsequent request from the same entity. This enables an entity to both determine support for the mechanism defined herein and start the authentication process.
For the POST and PUT methods (or any method containing a message body), clients MUST send all data with each request (if needed, the client should obtain credentials with a previous HEAD or OPTIONS method).
In order to associate the HTTP request with the XMPP confirmation, a transaction identifier MUST be provided by the user in the HTTP Authorization Request, then passed unchanged to the XMPP Client as the value of the <confirm/> element's 'id' attribute. If the XMPP Client generated the HTTP request, it MUST check the transaction identifier against the requests it has made to verify that the request has not yet been confirmed. If the XMPP Client did not generate the HTTP request, it MUST present the transaction identifier to the user for confirmation. If the XMPP Client or User confirms the request, the XMPP Client MUST then return a confirmation to the XMPP Server for delivery to the HTTP Server.
To reduce the likelihood of man-in-the-middle attacks, channel encryption SHOULD be used for both the XMPP channel and the HTTP channel. In particular:
For added security, the XMPP Server and XMPP Client may wish to communicate using end-to-end encryption. Methods for doing so are outside the scope of this proposal.
This document requires no interaction with the Internet Assigned Numbers Authority (IANA) [8].
The Jabber Registrar [9] shall include "http://jabber.org/protocol/http-auth" in its registry of protocol namespaces.
<?xml version='1.0' encoding='UTF-8'?>
<xs:schema
xmlns:xs='http://www.w3.org/2001/XMLSchema'
targetNamespace='http://jabber.org/protocol/http-auth'
xmlns='http://jabber.org/protocol/http-auth'
elementFormDefault='qualified'>
<xs:element name='confirm'>
<xs:complexType>
<xs:simpleContent>
<xs:extension base='empty'>
<xs:attribute name='id' use='required' type='xs:string'/>
<xs:attribute name='method' use='required' type='xs:NCName'/>
<xs:attribute name='url' use='required' type='xs:anyURI'/>
</xs:extension>
</xs:simpleContent>
</xs:complexType>
</xs:element>
<xs:simpleType name='empty'>
<xs:restriction base='xs:string'>
<xs:enumeration value=''/>
</xs:restriction>
</xs:simpleType>
</xs:schema>
1. RFC 2616: Hypertext Transport Protocol -- HTTP/1.1 <http://www.ietf.org/rfc/rfc2616.txt>.
2. RFC 2617: HTTP Authentication: Basic and Digest Access Authentication <http://www.ietf.org/rfc/rfc2617.txt>.
3. RFC 3920: Extensible Messaging and Presence Protocol (XMPP): Core <http://www.ietf.org/rfc/rfc3920.txt>.
4. JEP-0066: Out of Band Data <http://www.jabber.org/jeps/jep-0066.html>.
5. RFC 3986: Uniform Resource Identifiers (URI): Generic Syntax <http://www.ietf.org/rfc/rfc3986.txt>.
6. RFC 3548: The Base16, Base32, and Base64 Data Encodings <http://www.ietf.org/rfc/rfc3548.txt>.
7. RFC 2817: Upgrading to TLS Within HTTP/1.1 <http://www.ietf.org/rfc/rfc2817.txt>.
8. 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/>.
9. The Jabber Registrar maintains a list of reserved Jabber protocol namespaces as well as registries of parameters used in the context of protocols approved by the Jabber Software Foundation. For further information, see <http://www.jabber.org/registrar/>.
END