Voice of VOIPSA

As I mentioned previously (here and here), the “RUCUS” BOF about voice spam at IETF 71 in Philadelphia is one of great interest with its focus on voice spam, a.k.a. “SPam for Internet Telephony” or “SPIT”. Unfortunately BOF co-chair Hannes Tschofenig ran into a problem with his domain and had to move the page to a new URL: http://www.shingou.info/bof-rucus.html

If you saved the URL or sent it on to someone, you’ll need to update to using the new URL. If you didn’t visit the RUCUS page before, please do check it out - and feel free to join the RUCUS mailing list. Of course, if you can, please do join us in person in Philadelphia!

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spit, ietf, spam, rucus, standards, sip

Want to learn more about the voip security aspects of peer-to-peer SIP? As I mentioned in the VOIPSEC mailing list last week, researchers from Huawei and the University of California recently released an Internet-Draft called “P2PSIP Security Analysis and Evaluation” which dives into an analysis of security issues in P2PSIP. It’s a good overview and one I’d strongly recommend to folks. (Note - you may want to read “P2PSIP Concepts” first to understand the language being used.)

Beyond the Internet-Draft, though, the researchers announced yesterday that their slides are now available (PPT) that go into the issues. These are being prepared from presentation at the upcoming IETF 71 meeting March 10-14 in Philadelphia, so if you are attending the event you’ll be able to hear the presentation yourself.

Peer-to-peer SIP is a fascinating area of current research and it’s good to see work like this being put into exploring the security aspects. Note - the researchers are looking for feedback so if you have comments on what you read, their contact information is in the Internet-Draft.

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SIP, IETF, security, voip security, SIP security, p2p, p2psip, peer-to-peer

As mentioned previously, there is a new session planned for IETF 71 in March called “Reducing Unwanted Communications Using SIP“, a.k.a. “RUCUS”.

The RUCUS mailing list is now open for subscriptions and we encourage anyone interested in looking at how we address the issue of voice spam, aka “Spam for Internet Telephony” aka “SPIT” to join into the conversation.

We would ask you to please read the group description prior to joining so that you understand what we are trying to do. The primary goal of this session in March in Philadelphia is to look to understand the architecture necessary to address the issue and identify the pieces of that architecture that may already be there or may need to be put in place.

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rucus, spit, spam, voice spam, voip, voip security, security, ietf, standards

As we’ve discussed both here and on Blue Box, the issue of securing the keys for Secure RTP is one of the remaining challenges to have secure voice transmission in the open standards world of SIP. Out of the large number of proposals to secure the key exchange, “DTLS” emerged as the choice of the IETF… but it still had the issue that an endpoint needed to be sure of the authenticity of the other endpoint’s certificate. SIP Identity (RFC 4474) and a draft “Identity-Media” from Dan Wing addressed the authenticity issue but broke in some common network configurations. Now Kai Fisher has put out an Internet Draft called “End-to-End Security for DTLS-SRTP” that proposes a mechanism to address that. In the post to the SIP mailing list, Kai explains the motivation:

I have submitted a draft proposing a solution to secure a DTLS-SRTP handshake and hence SRTP end-to-end (in terms of end-domain to end-domain). As discussed during the last IETF meetings and analyzed by Dan’s Identity-Media draft, current solutions like SIP Identity do not protect the authenticity of the fingerprint end-to-end in certain inter-domain scenarios. For example, a modification of SDP m-/c-lines or the From header field by intermediaries breaks the SIP-Identity or Identity-Media signature and causes a re-signing by a domain different to the originating one. The draft proposes a solution for such scenarios without the need to re-sign during domain traversal and which preserves the original identity information.

The abstract to the draft provides more info:

The end-to-end security properties of DTLS-SRTP depend on the authenticity of the certificate fingerprint exchanged in the signalling channel. In current approaches the authenticity is protected by SIP-Identity or SIP-Identity-Media. These types of signatures are broken if intermediaries like Session Border Controllers in other domains change specific information of the SIP header or the SIP body. The end-to-end security property between the originating and terminating domain is lost if these intermediaries re-sign the SIP message and create a new identity signature using their own domain credentials.

This document defines a new signature type ‘Fingerprint-Identity’ which is exchanged in the signalling channel. Fingerprint-Identity covers only those elements of a SIP message necessary to authenticate the certificate fingerprint and to secure media end-to-end. It is independent from SIP-Identity and SIP-Identity-Media and can be applied in parallel to them.

More details can, of course, be found in the draft. As noted in the post to the SIP mailing list, Kai is looking for feedback. This is an important issue to get done - and to get done correctly - so we strongly urge people to take a look at the document and provide feedback if you see ways the proposal can be improved.

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SIP, SRTP, IETF, standards, sip security, voip security, security, DTLS

UPDATE: The RUCUS mailing list is now open for subscription.

Want to get together with others and discuss in further detail what we can do about Spam for Internet Telephony (SPIT)? A new session has been approved for the IETF 71 meeting coming up in Philadelphia in March called “Reducing Unwanted Communications using SIP” a.k.a. “RUCUS” (Hey, it’s not a real IETF group until it has a cute acronym!) Hannes Tschofenig, who submitted the proposal, has created a RUCUS web page and is looking for feedback. The page says in part:

The topic of dealing with unwanted traffic in SIP has surfaced several times in the IETF in the context of preventing Spam for Internet telephony. Previous attempts to have a structured discussion about this topic have (among other reasons) failed due to the strong focus on selected solution approaches.

Prior work in SIP on identity management has an important role in this activity since a strong identity mechanism in SIP has been seen as a prerequisity for establishing authorization policies. Hence, the “Discussion and Analysis of SIP Identity” (DASI) BoF is relevant for this event. Even though there is no direct dependency between the two activities the number of interested participants will quite likely overlap.

This BoF focuses on the discussion of architectural aspects. The underlying theme is that the work on building blocks is more fruitful once the larger framework is understood. A number of solutions components have been submitted to the IETF, have been published in the academic literature and found their way into other standardization bodies. Reduce unwanted communication requires authorization decisions to be made. These decisions can be made based on individual sessions but also on the interaction at a higher granularity (e.g., the interaction with a specific VoIP provider network). Examples of questions with relevance for an architecture might be:

- Where does information for decision making come from?

- What are useful information items for decision making?

- Where are policy decision points located? What about the placement of
policy enforcement points?

- Are privacy aspects to consider with the exchange of information?

- How does the underlying trust model look like?

- What assumptions are certain mechanisms based on?

- Can individual proposals be combined in a reasonable way?
etc.

It is not the aim of the BoF to discuss specific solution approaches since it is likely that multiple techniques have to be used in concert.

If you are attending IETF 71 in Philadelphia in March, do plan on joining in the RUCUS! (I’ll be there.)

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rucus, spit, spam, voice spam, voip, voip security, security, ietf, standards

Previously I mentioned that Hannes Tschofenig had a presentation up about SIP security that he gave at the ETSI Security Workshop early this month. We were contacted by folks at ETSI to let us know that all the workshop presentations are now available online. I haven’t looked through them yet, but the workshop agenda looked good to I am looking forward to checking these presos out. Thanks to ETSI for making them publicly available.

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sip, etsi, standards, security, voip security

Within the IETF there’s been a bit of discussion in the past months
about voice spam/SPIT and just recently RFC 5039 from Jonathan
Rosenberg and Cullen Jennings was published that specifically
addresses the issue of SIP and Spam.

The RFC is an excellent summary of the current thinking about the
SPIT problem and potential solutions to address it. If you haven’t
read the document, I would *highly* recommend it.

A concern I had, though, was that it did not appear to me that
existing documents address the issue of what SPIT could look like at
a network level. For instance, if a network administrator monitoring
network traffic suddenly saw a large flood of SIP INVITE packets
coming into his/her network, it could be:

1. a telemarketer/spammer launching a flood of SIP connections to
deliver SPIT;
2. an attacker launching a DoS attack through one of the various SIP
attack tools out there; or
3. a legitimate notification system starting to notify a range of SIP
endpoints.

I could very easily see existing network tools that look at traffic
and perform anomaly detection (and potentially source suppression)
being modified to suppress large flows of SIP traffic. This last case
of legitimate traffic concerned me and so I put together an Internet-
Draft talking about the types of legitimate systems that might
generate a significant volume of traffic that could resemble SPIT (or
a DoS attack).

I put the document out primarily to stimulate discussion. Are these
legitimate scenarios being addressed in current thinking about
SPIT? If not, my point really is that they need to be considered.

Comments about the document are very definitely welcome. Are there other scenarios I
should include? Am I accurate? Am I overstating the case? or what?

Technorati Tags:
ietf, security, sip, standards, voip, voip security

Hannes Tschofenig is over at the 3rd ETSI Security Workshop in France this week and yesterday gave a talk about SIP security. He has now posted the slides to his blog - My Slides from the 3rd ETSI Security Workshop:

Yesterday I gave my presentation at the 3rd ETSI Security Workshop. My presentation title was ‘IETF Security’ and that is obviously pretty fuzzy. After looking on the agenda I decided that the most useful topic to speak about would be SIP identity management and media security. In case you are interested in this topic, please take a look at the following slide set.

His slide set does give an excellent overview of security issues in SIP, the various RFCs and approaches, etc. As he mentions, he focuses on identity and media security. A great contribution to the ongoing dialog on these issues. In fact, much of the workshop agenda looks quite intriguing. It will be interesting to see if other presenters make their slides available or if conclusions are posted anywhere.

Note to other presenters: If you do put your slides up somewhere, we’re glad to link to them here. In fact, if you use SlideShare (or a similar service), we’ll be glad to embed the presentations directly in this blog.

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ietf, security, sip, standards, voip, voip security, hannes tschofenig

The IETF leadership recently announced that they are seeking final comments on an Internet-Draft called “Requirements from SIP Session Border Controller Deployments” (current draft also available here) as they decide whether to move this document to an Informational RFC. The abstract of the document is as follows:

This document describes functions implemented in Session Initiation Protocol (SIP) intermediaries known as Session Border Controllers (SBCs). The goal of this document is to describe the commonly provided functions of SBCs. A special focus is given to those practices that are viewed to be in conflict with SIP architectural principles. This document also explores the underlying requirements of network operators that have led to the use of these functions and practices in order to identify protocol requirements and determine whether those requirements are satisfied by existing specifications or additional standards work is required.

If you work with SBCs, use them in your networks, or work for a SBC vendor, now is a good time to ensure that this document captures the requirements you have for deploying SBCs. Once finalized as an Informational RFC, the idea is that it will be used to assist in the potential creation of new SIP-related standards or the modification of existing standards. Now is the time to voice your opinion (and the note from the IETF explains how to do that). Comments have been requested to be received by January 16, 2008.

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ietf, security, standards, voip, voip security, session border controllers, sbcs

Blue Box Podcast#73 is now available for download. In this show, Jonathan and I discuss SIP security issues at IETF 70, Skype security, vulnerabilities in Cisco and Nokia phones, Vietnam’s cyberdissidents, VoIP security news, listener comments and more..

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blue box, bluebox, voip security, voipsecurity