Internet DRAFT - draft-alkemade-xmpp-iq-validation
draft-alkemade-xmpp-iq-validation
Network Working Group T. Alkemade
Internet-Draft February 9, 2014
Updates: 6120 (if approved)
Intended status: Standards Track
Expires: August 13, 2014
Validating Info/Query (IQ) stanzas in the Extensible Messaging and
Presence Protocol (XMPP)
draft-alkemade-xmpp-iq-validation-00
Abstract
This document provides security recommendations for the validation
and generation of Info/Query (IQ) stanzas in the Extensible Messaging
and Presence Protocol (XMPP). This document updates RFC 6120.
Status of this Memo
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This Internet-Draft will expire on August 13, 2014.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Discussion Venue . . . . . . . . . . . . . . . . . . . . . . . 3
4. Recommendations . . . . . . . . . . . . . . . . . . . . . . . . 3
4.1. No 'from' . . . . . . . . . . . . . . . . . . . . . . . . . 3
4.2. Rejecting spoofed replies to queries . . . . . . . . . . . 4
4.3. Preventing presence leaks . . . . . . . . . . . . . . . . . 4
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
7. Normative References . . . . . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 5
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1. Introduction
The Extensible Messaging and Presence Protocol (XMPP) [RFC6120] uses
Info/Query (IQ) stanzas as a "request-response" mechanism. The
semantics of IQ enable an entity to make a request of, and receive a
response from, another entity. The interaction is tracked by the
requesting entity through use of the 'id' attribute. Thus, IQ
interactions follow a common pattern of structured data exchange such
as get/result or set/result (although an error can be returned in
reply to a request if appropriate).
However, it was found not all implementations properly verify the
origin of IQ responses. This documents provides recommendations on
how to avoid spoofed responses.
2. Terminology
Various security-related terms are to be understood in the sense
defined in [RFC4949].
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
[RFC2119].
3. Discussion Venue
The discussion venue for this document is the mailing list of the
XMPP Working Group, for which archives and subscription information
can be found at <https://www.ietf.org/mailman/listinfo/xmpp>.
4. Recommendations
4.1. No 'from'
Section 8.1.2.1. of [RFC6120] specifies that IQ stanzas sent on
behalf of the user's own account MUST either (a) include no 'from'
attribute or (b) use the user's bare JID as 'from' address (i.e.,
<localpart@domainpart>). For compatibility with incorrect servers
and servers still following [RFC3920], implementations MAY
additionally accept a reply with either (a) a 'from' address equal to
the full JID of the client (i.e.,
<localpart@domainpart/resourcepart>) or (b) a 'from' address equal to
the domainpart of the JID of the account (i.e., <domainpart>).
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4.2. Rejecting spoofed replies to queries
'id' attributes are used as end-to-end identifiers of stanzas: the
same 'id' attribute is used across every hop. When delivered, the
receiver will see the same 'id' value as the sender specified. As
described in Section 8.1.3. of [RFC6120], it is REQUIRED to include
'id' values on IQ stanzas and RECOMMENDED for all other stanza types.
The entity creating a stanza needs to ensure the 'id' values it
generates are unique.
After sending an IQ stanza with type "get" or "set", an entity may
store the 'id' and 'to' of the outgoing <iq/> element to identify the
response. When an IQ stanza comes in with a matching 'id' and type
"result" or "error", the entity MUST verify that the 'from' attribute
on the <iq/> matches the 'to' of the outgoing stanza. If the 'from'
and 'to' attributes do not match, the entity MUST ignore the stanza.
As is mandatory in response to IQ stanzas of type "result" or
"error", the entity MUST NOT return an error.
For queries where the intended recipient is the server acting on
behalf of the user's own account entities MAY apply the exceptions in
Section 4.1.
4.3. Preventing presence leaks
Many implementations use a counter to generate new 'id' attributes
for stanzas to guarantee their uniqueness. However, this may leak
presence information of the user: it can give an approximation of how
long a client has been running and how many stanzas it has sent since
a previous stanza. This could, for example, give an indication of
how many messages a user has sent in a certain time. Therefore
clients SHOULD NOT include a counter in the 'id' attribute.
Additionally, it is RECOMMENDED to use randomly or pseudo-randomly
generated 'id' attributes. Implementations using [RFC4122] to
generate Universally Unique IDentifiers (UUIDs) to use as 'id'
attributes MUST use version 4 UUIDs, which are randomly or pseudo-
randomly generated and carry no identifying information.
Implementations using a pseudo-random generator, either directly or
for generating UUIDs, SHOULD make sure that future values are hard to
predict. For more information see [RFC4086].
5. IANA Considerations
This document requests no actions of the IANA.
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6. Security Considerations
This document covers security.
7. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3920] Saint-Andre, P., Ed., "Extensible Messaging and Presence
Protocol (XMPP): Core", RFC 3920, October 2004.
[RFC4086] Eastlake, D., Schiller, J., and S. Crocker, "Randomness
Requirements for Security", BCP 106, RFC 4086, June 2005.
[RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally
Unique IDentifier (UUID) URN Namespace", RFC 4122,
July 2005.
[RFC4949] Shirey, R., "Internet Security Glossary, Version 2",
RFC 4949, August 2007.
[RFC6120] Saint-Andre, P., "Extensible Messaging and Presence
Protocol (XMPP): Core", RFC 6120, March 2011.
Author's Address
Thijs Alkemade
Email: me@thijsalkema.de
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