Subject: [secdir] sec-dir review of draft-ietf-siprec-architecture-08

From: Derek Atkins <[email-masked]>
Date: Tue, 01 Oct 2013 11:33:53 -0400

Hi,

I have reviewed this document as part of the security directorate's 
ongoing effort to review all IETF documents being processed by the 
IESG.  These comments were written primarily for the benefit of the 
security area directors.  Document editors and WG chairs should treat 
these comments just like any other last call comments.

   Session recording is a critical requirement in many communications
   environments such as call centers and financial trading.  In some of
   these environments, all calls must be recorded for regulatory,
   compliance, and consumer protection reasons.  Recording of a session
   is typically performed by sending a copy of a media stream to a
   recording device.  This document describes architectures for
   deploying session recording solutions in an environment which is
   based on the Session Initiation Protocol (SIP).

Retrieving recorded media is a potential Key Management problem which
this document completely ignores (and even claims is out of scope).
The key used to encrypt the recorded media (whether or not the media
is re-encrypted) must be stored and retrieved as part of the media
retrieval.  How this important data is stored and retrieved is left
out, leaving an implementation with no guidance on how to protect that
valuable asset.  In fact the document completely elides the question
of how a retriever obtains the data encryption key.  Even if it's just
additional guidance the Security Considerations should at least
explain the problem even if it doesn't provide a solution.

-derek

-- 
       Derek Atkins                 617-623-3745
       [email-masked]             www.ihtfp.com
       Computer and Internet Security Consultant

---

From: "Hutton, Andrew" <[email-masked]>
Date: Wed, 16 Oct 2013 14:20:21 +0000

Hi Derek,

Thanks for your comment and sorry for taking a while to get back to you.

The security considerations section contains the following text:

" It is the responsibility of the Session Recording Server to protect
   the Replicated Media and Recording Metadata once it has been received
   and archived.  The mechanism for protecting the storage and retrieval
   from the SRS is out of scope of this work."

Personally I think this is reasonable as we never say anything in SIP related specifications what a UA should do with the media once it has been received and this work is all about delivering the media and related metadata to the recording system not what it does with it afterwards.

Is it really necessary to go any further than this?

Regards
Andy (SIPREC Co-Chair).

> -----Original Message-----
> From: Derek Atkins [mailto:[email-masked]]
> Sent: 01 October 2013 16:34
> To: [email-masked]; [email-masked]
> Cc: [email-masked]; [email-masked];
> [email-masked]; [email-masked]; Hutton, Andrew
> Subject: sec-dir review of draft-ietf-siprec-architecture-08
> 
> Hi,
>

---

From: Derek Atkins <[email-masked]>
Date: Thu, 24 Oct 2013 10:53:26 -0400

Hi Andrew,

Sorry for the delay in responding.

I personally feel that there is a big difference between the
interactive, real-time SIP components versus a service that is
specifically designed to record and replay content later.  The key
management of the real-time components is all immediate, there is no
storage required, once the keys get to the endpoints you're done and all
you do is transmit encrypted content.

However a storage system has significantly different requirements.  It
has to store the keys that protect the content, and it must store those
keys securely.  It then has to be able to securely distribute those keys
only to authorized receipients.

So yes, I think it is important to talk about at least the requirements
for what the recording agent MUST do, even if you don't necessarily
specify HOW the agent must do it.  E.g. I think it's okay to say
something like "the stored content must be protected using a cipher at
least as strong (or stronger) than the original content" -- i.e., you
don't need to specify "you MUST use AES-256".  Yet I still think you
need to talk about the key management requirements of the storage (and
more importantly retrieval).

Thanks,

-derek

"Hutton, Andrew" <[email-masked]> writes:

> Personally I think this is reasonable as we never say anything in SIP
> related specifications what a UA should do with the media once it has
> been received and this work is all about delivering the media and
> related metadata to the recording system not what it does with it
> afterwards.
>

---

From: "Hutton, Andrew" <[email-masked]>
Date: Thu, 24 Oct 2013 15:36:57 +0000

Hi Derek,

I am ok with putting something in the security considerations to say the key management requirements for storage and retrieval is something that the recording system will need to consider but I would still say that saying anything more than that is out of scope.

What do others think?

Andy

> Sent: 24 October 2013 15:53
> To: Hutton, Andrew
> Cc: Derek Atkins; [email-masked]; [email-masked]; siprec-
> [email-masked]; [email-masked]; [email-masked];
> [email-masked]
> Subject: Re: sec-dir review of draft-ietf-siprec-architecture-08
> 
> Hi Andrew,
>

---

From: Raj Jain <[email-masked]>
Date: Thu, 24 Oct 2013 13:47:45 -0400

I think Andy's approach to addressing this is appropriate. The way recording systems deal with the security issues of archived media content seems out of scope of SIPREC. A statement can be made to clarify this the way Andy is proposing.

> From: [email-masked]
> To: [email-masked]
> CC: [email-masked]; [email-masked]; [email-masked]; [email-masked]; [email-masked]; [email-masked]
> Subject: RE: sec-dir review of draft-ietf-siprec-architecture-08
> Date: Thu, 24 Oct 2013 15:36:57 +0000
> 
> Hi Derek,
>

---

From: "Hutton, Andrew" <[email-masked]>
Date: Wed, 30 Oct 2013 17:39:16 +0000

Hi Derek,

Would the following change in the security considerations section resolve your issue:

"It is the responsibility of the SRS to protect the Replicated Media and Recording Metadata once it has been received and archived. The mechanism for protecting the storage and retrieval from the SRS is out of scope of this work"

To 

"It is the responsibility of the SRS to protect the Replicated Media and Recording Metadata once it has been received and archived. The stored content must be protected using a cipher at least as strong (or stronger) than the original content however the mechanism for protecting the storage and retrieval from the SRS is out of scope of this work"

Regards
Andy