1. Securing the CASP Protocol
Hannes Tschofenig
CT IC 3

2. Creating a Security Solution for CASP
Threat-Analysis
Security
Requirements
Framework Thoughts
Custom Security
Existing Security
Key Management (authentication, authorization, session key establishment), Signaling message protection (integrity, confidentiality, replay protection), authorization, denial of service protection, identity protection, topology hiding, protocol specific security issues

3. CASP Protocol Parts Implication for Security
Many usage scenarios have to be supported
Unlike RSVP a transport connection is established
Unlike RSVP the next peer has to be known in advance before a CASP payload message is sent
Using existing security mechanisms does not always fit 100%
CASP tries to be more complete than RSVP
Security also includes key management aspects and addresses framework issues

4. Security for the Discovery Component The Scout Protocol
Threat
Denial of service attacks, man-in-the-middle attacks, downgrading of security or capabilities
Problems
Other node is unknown (reason for discovery)
Message is restricted to a single roundtrip and message size is small
Security protection can easily introduce other attacks such as DoS
Solution
Scout message contains only very few protection mechanisms BUT
Subsequent the subsequent message exchange has to repeat information and
Has to provide some additional security verifications

5. Security for the Transport Layer
Threat
Attacks against the transport layer can cause a connection abort.
Problems
Vulnerability of TCP itself
TLS does not protect TCP header
Solution
If attack is a concern then
Use IPSec at network layer
Use the more robust SCTP

6. Security for the Messaging Layer
Threat
Messaging layer contains security relevant information for a variety of attacks
Problems
More than a single security mechanisms has to be supported
(for different parts of the network and different usage scenarios)
Solution
IPSec
TLS (possibly with EAP on top of it)
Many different key exchange protocols supported (IKE, KINK, SOI, etc.)
Efficiency gained by reusing security association more a number of client-layers and a number of messages.

7. Security for the Client-Layers
Threat
Intermediate CASP node is able to inspect and modify information
Problems
Peer-to-Peer protection not always sufficient
Examples: Authorization tokens, transport of local information, selectively protecting objects, transporting sensitive information
Solution
CMS used to selectively wrap objects and to provide protection for them.
For investigation: Reusing of a CMS security association

8. Miscellaneous Issues Non-Repudiation Rarely required
Supported for client-layer protocols by using digitally signed encapsulated objects (CMS) and possibly applying a counter-signature by the other party
Denial of Service Prevention
Network Topology Hiding
Supported for Record Route object
Additionally supported by removing addresses from a (strict or loose) route object

9. Miscellaneous Issues Authorization
Supports both “online” or “offline” authorization
“Online” authorization requires protocol interaction with third party entity (AAA-based). EAP/Diameter support is possible. Identity mapping possibly required
“Offline” authorization supported via Kerberos authorization information or attribute certificate
Authorization language is open issue – research required.
Usage of specific authorization information is scenario and environment dependent.

10. Are there any questions?