Privacy Issues inVirtual Private Networks

Tim Strayer

BBN Technologies

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What is a VPN?

• Private network running over shared network infrastructure (Internet) Allows interconnection of different

corporate network sites Allows remote users to access the

corporate network Allows controlled access between different

corporate networks

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Private“Intranet”Network

Headquarters

Why VPNs?

PublicInternet

Intranet

Headquarters

Intranet

Remote Site

Intranet

Remote Site

Frame RelayOr

ATMOr

Dial-Up Service

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VPN Rationale

• Private Networks Costly Inflexible Multiple Infrastructures

• Virtual Private Networks Inexpensive Configurable Single Infrastructure

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The First VPN

• 1975, BBN delivered the first Private Line Interface (PLI) to the Navy

• Created secure network communication over the ARPANET

• Used a proprietary encryption and manual keying system

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VPN Technologies

• Tunneling Overlay facilitates sharing common infrastructure IPsec, PPTP, L2TP, MPLS

• Security Authentication: PKI, RADIUS, Smartcard Access Control: Directory Servers, ACLs Data Security: Confidentiality, Integrity

• Provisioning QoS Traffic Engineering

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Island Metaphor

“Hello!”

“???”“Oh! Hi!

“Hello!”

“Hello!”SS Encapsulator

SS Encapsulator

“Hello!”

“Hello!”SS Encapsulator

Tunnel

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Tunneling

• Usually layers are inverted

Inner PacketOuter Header Trailer

For target network

For transport network

Ethernet IPIP PPP

2 323

Ethernet FTPIP TCP

2 743

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Tunnels at Layer 2

• Point-to-Point Tunneling Protocol (PPTP) Integrated into Microsoft DUN and RAS Authentication/encryption provided by PPP

• Layer 2 Tunneling Protocol (L2TP) Combines PPTP with Cisco L2F Layer 2 tunneling, UDP encapsulation

IP IP/IPXGREv2 PPP

IP IP/IPX/IPsecUDP PPP

3 324

3 324

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IPsec Protocol Suite

• Data encryption and authentication Two protocols

• Encapsulating Security Payload (ESP) assures data privacy and party authentication

• Authentication Header (AH) assures only party authentication

Cryptographic key management• Works well with Public Key Infrastructure and X.509

Certificates

• Transport and tunnel modes of operation• IPsec VPNs use tunnel mode and ESP

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IPsec Tunneling

Original IP Header

Original IP Payload

New IP Header

Security Parameter Index

Sequence Number

ESP Trailer

ESP Authentication

Encr

ypte

d

Auth

enti

cate

d

OriginalIP Packet

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MPLS “Tunneling”

• Multi-Protocol Label Switching High speed switching technology Tunnel any layer Built into edge/core routers and switches No authentication/encryption

Label IP PayloadIP Header

Original Packet

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IPsec vs. MPLS

• Two dominant VPN technologies

• Let’s compare them viz. their approaches to privacy

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What is meant by Private?

• No one can see your stuff Emphasis is on security Confidentiality, integrity, authentication,

authorization, access control

• Carve out a piece of a shared network for your own use Emphasis is on availability Traffic engineering

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Evolution of IPsec

• First defined as a security mode for IPv6

• “Ported” to IPv4

• Combines tunneling with security Orthogonal services

• Complex key management

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Evolution of MPLS

• ATM’s VCI/VPI used for cut-through switching Separates routing from forwarding Supports resource allocation

• MPLS IP cut-through switching using label Routers switch on preestablished label Routers don’t care what’s behind the label Originally proposed to accelerate routing

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A Protocol Looking for a Use

• Fast routing argument lost with new routing technology Switching technology applied to IP header

• MPLS for traffic engineering “Connection” oriented Stateful – keeps tracks resource allocation

and usage RSVP adapted for signaling

• Hot router selling feature

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MPLS-VPN Security

• Label Switch Routers will drop packets that do not belong to the VPN based on label

• BGP guards against injected routes using MD-5 authentication

• Note: No data confidentiality Weak authentication BGP is not sufficient to prevent fake routes

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Why MPLS-VPN?

• Embed label switching in routers Sell more routers

• Replace Frame Relay and ATM with something that looks like these services No profit in Frame Relay or ATM anymore

• Control provisioning at the edge of ISP Sell value added service

• ISP dependent Keeps customers within provider’s network

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Why IPsec-VPN?

• No changes to core routers Security gateway/tunnel endpoint placed

anywhere that is appropriate

• Separation through obfuscation Real data confidentiality Real authentication

• Routing protocol agnostic No (more than current) reliance on well-behaved

protocols

• ISP agnostic

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Guarding “Privates”

• What separates a VPN’s traffic from all other traffic? IPsec: data encryption MPLS: different labels, forwarding tables

• Who is responsible for separation? IPsec:

• ISPs, but not necessarily• Corporate IT group and even individuals

MPLS: ISPs

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Dichotomy of Assumptions

• IPsec assumes goal is: IP delivery No trust of intermediate systems

• MPLS assumes goal is: Engineered delivery Trust entities in the middle

• Begged question: Is leaving security to someone else a good thing?

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Which is the Right Way?

• Depends on what control you are willing to cede to service providers What SLAs you demand What you want to “black box”

• Depends on what you mean by “private” No one is supposed to use your resources No one is able to see your stuff

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Trends in VPNs

• IPsec is being built into routers, gateways, and firewalls, and can run at very high speeds

• Layer 2 tunneled through MPLS Martini Draft

• Combining MPLS and IPsec IP tunneled through IPsec tunneled

through MPLS Best of both worlds

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There’s more to it

• Establishing a VPN is much more than just building a set of tunnels between sites Authentication Access Control Data Confidentiality Data Integrity Remote Access

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Where does “Private” go?

• Virtual Private Network Makes sense What the designers had in mind

• Virtual Private Network What happens if you’re not careful

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More about me

• This talk and other information athttp://www.ir.bbn.com/~strayer