Subject: [MMUSIC] I-D ACTION:draft-ietf-mmusic-kmgmt-ext-08.txt

From: [email-masked]
Date: Fri, 01 Aug 2003 15:28:44 -0400

A New Internet-Draft is available from the on-line Internet-Drafts directories.
This draft is a work item of the Multiparty Multimedia Session Control Working Group of the IETF.

	Title		: Key Management Extensions for Session Description
                          Protocol (SDP) and Real Time Streaming Protocol (RTSP)
	Author(s)	: J. Arkko et al.
	Filename	: draft-ietf-mmusic-kmgmt-ext-08.txt
	Pages		: 16
	Date		: 2003-8-1
	
This document defines general extensions for SDP and RTSP to carry
the security information needed by a key management protocol, in
order to secure the media. These extensions are presented as a
framework, to be used by one or more key management protocols. As
such, its use is meaningful only when it is completed by the key
management protocol in use.
General guidelines are also given on how the framework should be used
together with SIP and RTSP.

A URL for this Internet-Draft is:
http://www.ietf.org/internet-drafts/draft-ietf-mmusic-kmgmt-ext-08.txt

To remove yourself from the IETF Announcement list, send a message to 
ietf-announce-request with the word unsubscribe in the body of the message.

Internet-Drafts are also available by anonymous FTP. Login with the username
"anonymous" and a password of your e-mail address. After logging in,
type "cd internet-drafts" and then
	"get draft-ietf-mmusic-kmgmt-ext-08.txt".

A list of Internet-Drafts directories can be found in
http://www.ietf.org/shadow.html 
or ftp://ftp.ietf.org/ietf/1shadow-sites.txt

Internet-Drafts can also be obtained by e-mail.

Send a message to:
	[email-masked].
In the body type:
	"FILE /internet-drafts/draft-ietf-mmusic-kmgmt-ext-08.txt".
	
NOTE:	The mail server at ietf.org can return the document in
	MIME-encoded form by using the "mpack" utility.  To use this
	feature, insert the command "ENCODING mime" before the "FILE"
	command.  To decode the response(s), you will need "munpack" or
	a MIME-compliant mail reader.  Different MIME-compliant mail readers
	exhibit different behavior, especially when dealing with
	"multipart" MIME messages (i.e. documents which have been split
	up into multiple messages), so check your local documentation on
	how to manipulate these messages.

Below is the data which will enable a MIME compliant mail reader
implementation to automatically retrieve the ASCII version of the
Internet-Draft.

---

From: Colin Perkins <[email-masked]>
Date: Mon, 11 Aug 2003 18:26:49 +0100

> http://www.ietf.org/internet-drafts/draft-ietf-mmusic-kmgmt-ext-08.txt

I have a number of comments on this draft:

  - The ABNF in Sections 2.1 and 2.2 is contradictory. The key management
    data is defined as "text" in one section, and "quoted-string" in the
    other, yet these two types have different ranges of valid characters
    (and both are more liberal than the explanatory text, which implies
    that only base-64 encoded data is allowed). Similar for the protocol
    identifier: the definitions of "non-ws-string" in SDPnew and "token"
    in RTSP are not consistent.

  - It should be stated that the protocol identifiers in Section 2.1 and
    Section 2.2 refer to the same set of values, and a reference to the
    registry of legal values should be given (i.e. reference the IANA
    parameter registry defined in Section 6).

  - The draft repeatedly mentions Kerberos, and indicates that Kerberos
    tickets may be included in key management messages, but does not
    specify how this is to be achieved. Should either specify how to use
    Kerberos, or remove all references to it.

  - The second bullet point on Page 6 mentions that other parameters may
    need to be specified for certain key management protocols, but does
    not specify how an implementor knows if a particular key management
    protocol uses additional parameters. Suggest this is listed as part
    of the IANA registration for a particular key management protocol?

  - Section 3.1 seems to assume Offer/Answer usage. It is not clear how
    it applies to SDP used with, for example, SAP, HTTP, or email? What
    about one-to-many distribution of SDP? Or distributions where there
    is no back-channel? It is acceptable for the draft to be explicit
    about the limits of its scope, but it cannot ignore the wider problem
    space.

  - The discussion of authentication on Page 7 is not mentioned in the
    list of things senders and receivers of SDP must do, on pages 5 and
    6.

  - Section 3.3 does not mention authentication. Should I assume that
    there is no need for authentication when key management is used with
    RTSP?

  - Section 4 needs to provide strict guidance about the parameters and
    specifications needed for new key management protocols. The interface
    between the key management protocol and this framework should be made
    explicit.

  - I find the arguments about security of the SDP in Section 5 weak. The
    draft needs to be explicit about the threats it prevents and those it
    leaves open. Recommend re-reading RFC 3553, Section 5.

  - In section 5, how is a beat-down attack prevented when the attacker
    wishes to beat-down to no security? What is the correct response to
    an answer which suggests no security?

  - Section 6 needs to register the RTSP extensions needed, and make it
    clear that the namespace for key management protocol identifiers is
    shared between the RTSP and SDP extensions.

  - Section 6 mentions that new key management protocols specify "the
    syntax of possible additional arguments", yet this contradicts the
    ABNF which states that only a single argument is present.

The main issue behind these seems to be the desire to define new 
parameters which can be left open for future uses. As was mentioned in 
the context of the "a=gpmd:" attribute, this is not acceptable: there 
needs to be a precise definition of the semantics of any new SDP 
attribute/RTSP header before the draft can advance.

-- 
Colin Perkins
http://csperkins.org/

_______________________________________________
mmusic mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/mmusic