Class 11 Enterprise Network Protection CIS 755: Advanced Computer Security Spring 2014 Eugene Vasserman eyv/CIS755_S14

Class 11Enterprise Network Protection

CIS 755: Advanced Computer SecuritySpring 2014

Eugene Vasserman

http://www.cis.ksu.edu/~eyv/CIS755_S14/

Administrative stuff

• Exam I on March 25th

• Don’t accidentally come to class next week :)

• I’ll be here, but no fixed office hours:– Email if you need to see me–Or stop by if my door is open (it usually is)

Distributed Systems: Definition

• “A system of multiple communicating entities performing a coordinated function”

• “A system where a computer that you’ve never heard of, located somewhere you’ve never been, can cause your computer to stop functioning correctly”

–Humorous paraphrase of Lamport

Distributed Systems: Why?

• Increased robustness (maybe)– Eliminating single point of failure

• Resource sharing–e.g. Beocat–e.g. a mobile device and a server

• Improved scalability (maybe)–e.g. Beocat

Distributed Systems: Security

• Eliminating a single point of failure–Denial of service protection (robustness)

• Eliminating a single point of trust–What if your boss is malicious?

• If we want to reap benefits of distributed system designs, we have to take care of the “maybes” in previous slides

• How?

Distributed Systems: Privacy

• Local system – local information• Distributed system – more access to

potentially private information• Privacy vs. authentication• Sometimes privacy is not a security

requirement, sometimes it is• Are there other potential security

requirements related to privacy?

Questions?

(Security) Problems with networking

• Many different systems– LANs, WANs, WLANs–Routers and switches–VLANs– Firewalls, gateways, VPNs

• Lots of work to configure independently• Enforcement at different layers– Each needs different security considerations

Layering (OSI 7-Layer Model)

• Data link• Network• Transport

– Lowest level end-to-end protocol

– Header generated by sender is interpreted only by the destination

– Routers treat transport header as part of the payload

• Application9/54

App.App.

66

55

App.App.

66

55

TransportTransport

NetworkNetwork

Data LinkData Link

PhysicalPhysical

TransportTransport

NetworkNetwork

Data LinkData Link

PhysicalPhysical

NetworkNetwork

Router

22 22

11 11

Security goals

• Strict admission control• Topology hiding (why?)• Link-layer enforcement (below IP)– Less likely to unintentionally allow access

• Single trusted component• Simple management• Simple and fast revocation

Compare to Kerberos…

Potential solutions

• Self-configuring systems–Difficult to determine “correct” protection without

administrator intervention

• Gossiping security devices– Translations between rule-sets

• SANE uses a centralized infrastructure–Access control database–Automated rule generation and device

programming

The SANE approach

• Domain controller provides–Authentication service–Network service directory (NSD)–Protection layer controller

• Least-privilege approach (for enterprise)• Capability-based routing• SANE protocol header right after Ethernet• IPs used for wide-area, ignored locally

Initialization/authentication

All roads lead to the DC

• DC is root of minimum spanning tree (MST)– Switches are the other nodes–Communication using distance vector (DV)• Like Ethernet

• Switches don’t learn network topology – they only see their neighbors in the tree–Can they misbehave in order to observe

topology?

DC: Bootstrapping topology info

• Communicate with nearest switches

• Compute shared keys• Receive topology updates• Repeat with next switch layer• Construct tree communication

capabilities• What can go wrong?

Protection layer controller

• Capability provider• Maintains global network view to

compute routes• Processes link state updated from

authenticated switches• Dynamically reprograms switches

Types of packets

• HELLO – discovery– Never forwarded, no authentication

• DC – capability (or revocation) request– Forwarded just to DC if no routing capability– Contains client authentication

• FORWARD – data packets (majority)– Capability, capability ID, expiration

• REVOKE– Capability ID, expiration, DC signature

Source routing with capabilities

B, dataS3S2S1 BS3

S2

S1

A

What the switches do

• DC packets, revocation requests–Use tree (MST) to send to DC

• FORWARD packets–Check capability for validity• Semantically correct (valid MAC)• Not expired• Not revoked

– If valid, forward, otherwise discard

Capabilities

• Require no payload• Onion-wrapped• Encrypted/MACed• IV to prevent topology inference• Principal names in capability incorporate

both identity and route (sanity checks)

Backward compatibility

• Incoming and outgoing translation proxies• Capabilities are strictly richer than IP

infrastructure– Includes naming and addressing; can be

translated seamlessly by correct software

• UPnP-like broadcast must be handled by DC– Increased load!

Tolerating horribleness

• What if a server “fails”?• A switch?• A gateway?• The DC?– Multiple DCs with multiple spanning trees– Byzantine consensus may be problematic in practice

• The physical network fabric?– Trees are fragile!

• Lots of recent work on centralized management controllers

Performance

• Tested using real network traces• DC can handle typical enterprise network load

using a desktop box– Multi-DC configuration untested

• O(n2) coordination messages may be a nasty surprise

• Switches need to be modified– Software-based forwarding almost impossible– Hardware-based crypto not easily upgradeable– Specific requirements unclear

Benefits

• Easier upgrades (may seem counter-intuitive)• Host [anti-]mobility• Transparent traffic rerouting– Logging– Transformation

• SSL, VPN

• Capabilities improve attack resistance• Built-in DoS resistance via revocation push-back– No coordination issues like Internet-wide schemes

Drawbacks

• Centralization can come back to bite you– Byzantine consensus can be costly

• Switches need to be updated• Incremental deployment requires “translator”

devices– “4D” features better incremental deployability

If you find this paper interesting I would strongly suggest reading “4D”

(http://portal.acm.org/citation.cfm?id=1096536.1096541 )

Questions?

Reading discussion