Muhammad Nasir Mumtaz BhuttaCentre for Communication Systems Research

University of SurreyGuildford, Surrey

GU2 7XHEmail: m.bhutta@surrey.ac.uk,

Tel: 01483 68 3036

www.surrey.ac.uk

Multilayer Security Architecture for Internet

Protocol (ML-IPSec)

1 October, 2010

www.ee.surrey.ac.uk/CCSR2

• Demonstrate “Security Architecture for Internet Protocol” (IPSec) protection model.

• Highlight the limitations of IPSec. • Demonstrate the working or ML-IPSec. • Demonstrate the detailed experiment

plans.

Objectives

www.ee.surrey.ac.uk/CCSR3

Introduction

• Security Architecture for Internet Protocol (IPSec) provides security services at IP layer in protocol stack.

• All upper layers than IP layer can get security services without reengineering the applications.

• IPSec operates in two modes, tunnel and transport, to secure path(s) between communicating nodes.

www.ee.surrey.ac.uk/CCSR4

Path(s) Security

• Between Pairs of Gateways– Gateways need to implement IPSec.– Works in Tunnel Mode (complete IP

packet is protected & new IP header is appended).

– Different source and destination addresses in dual IP headers.

Protected Subnet

Tunnel EndpointGateway

Un Protected SubnetIPSec Tunnel

Tunnel EndpointGateway

Protected Subnet

www.ee.surrey.ac.uk/CCSR5

Path(s) Security

• Between Pair of Hosts– End nodes need to implement IPSec. – Works in Transport Mode (Upper layers

headers and IP data are protected). – IP addresses are unchanged.

Un Protected SubnetIPSec Tunnel OR Transport mode

Protected EndpointProtected Endpoint

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Path(s) Security

• Between Host and Gateway– Both end hosts and gateways implement

IPSec. – Usually works in tunnel mode to take

benefits of hiding external characteristics of communication.

Un Protected SubnetIPSec Tunnel

Protected Endpoint

Protected SubnetAND/ORInternet

Protected Endpoint

www.ee.surrey.ac.uk/CCSR7

Security Goals

• Access Control– Prevent unauthorized access to

resources. • Connectionless Integrity

– Check any modifications in IP datagram without caring about the arrival order of IP datagrams.

• Origin Authentication– Identify claimed source of data.

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Security Goals (continued..)

• Partial Sequence Integrity– Check for duplicate packets (Replay

attacks).• Data Confidentiality

– Protect against disclosure of data to unauthorized entities.

• Limited Traffic Flow Confidentiality – Protect external characteristics of

communications (e.g. source and destination addresses etc.).

www.ee.surrey.ac.uk/CCSR9

Major IPSec Components

• Security Policies– Provides rules for user access and control level.

• Security Protocols– Authentication Header (AH)

• Provides origin authentication, connectionless integrity and optional partial sequence integrity.

– Encapsulating Security Payload (ESP)• Provides all services provided by AH, data

confidentiality and limited traffic flow confidentiality as well.

www.ee.surrey.ac.uk/CCSR10

Major IPSec Components (continued..)

• Cryptographic Algorithms– Helps to achieve integrity and

confidentiality. • Key Management

– All security operations are provided by cryptographic means, so keys are required.

– Internet Key Exchange (IKE v2) is used to provide key management.

www.ee.surrey.ac.uk/CCSR11

Assumptions

• To achieve high quality of security services, certain assumptions need to be met: – Good implementation of IPSec.– Security is dependent on many things in

over all system (e.g. personnel & physical procedures, security policies etc.), so IPSec just play its role as a part.

– Good Implementation of Operating System (OS) security services.

www.ee.surrey.ac.uk/CCSR12

IPSec Components to Help in Achieving Security Goals

• Security Association (SA)– SA is a one way traffic secure

connection between communicating parties.

– For Bidirectional communication, two SAs are established.

– SA, providing actually all security services, is setup by IKE.

– Functionality is dependent upon security protocols, mode of IPSec working, endpoints of SA and chosen security services.

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IPSec Components to Help in Achieving Security Goals (continued..)

• Security Policy Database (SPD)– Stores security policies. – Provides information about security policy rules

to be applied.– At least one SPD implementation must be

supported in IPSec.– Three logical components

• SPD-Secure (S) contains rules for all IPSec protected traffic.

• SPD-Outbound (O) contains rules for all outbound traffic

• SPD-Inbound (I) contains rules for all inbound traffic or bypassed.

www.ee.surrey.ac.uk/CCSR14

IPSec Components to Help in Achieving Security Goals (continued..)

• Security Association Database (SAD)– Stores SAs. – Provides information about security

associations. – For outbound processing SAD is pointed by

SPD-S part. – For inbound processing SAD is pointed by SPD-I

part.• Peer Authorization Database (PAD)

– Stores information about links between SPD and SAD.

– Helps IPSec components in security services practice.

www.ee.surrey.ac.uk/CCSR15

IPSec Working & Role of IKE

• IKE helps in setup of security associations (SAs). – The functionality of all cryptographic protocols

is dependent on these SAs. – Control information exchange also requires SA

setup. • IKE provides this setup by message

exchanges. – IKE_SA_INIT, IKE_AUTH– IKE_CHILD_SA– Informational Exchanges

www.ee.surrey.ac.uk/CCSR16

IPSec Working & Role of ESP

• ESP provides origin authentication, connectionless and sequence integrity, data and limited traffic flow confidentiality.

• Security services are offered in three modes by ESP.– Confidentiality Only (may be supported) – Integrity Only (must be supported) – Confidentiality and Integrity (must be

supported)

www.ee.surrey.ac.uk/CCSR17

IPSec Working & Role of ESP (continued..)

• Data Confidentiality– Data confidentiality is provided via encryption.– Encryption scheme selection is dependent

upon SA out of various encryption algorithms. • Origin Authentication and Connectionless

Integrity – Integrity of IP datagram is validated via

Message Authentication Code (MAC). – Origin authentication is provided indirectly by

binding of the key with the holding entity (origin).

www.ee.surrey.ac.uk/CCSR18

IPSec Working & Role of ESP (continued..)

• Anti-Replay Service (Partial Sequence Integrity)– This is service to detect arrival of

duplicate packets. – Provides sequential integrity and may

be supported in ESP. • Limited Traffic Flow Confidentiality

– This service hides source and destination addresses and usually employed in Tunnel Mode.

www.ee.surrey.ac.uk/CCSR19

Limitations of IPSec

• IPSec follows very strict layering and protection model works end-to-end.

• With advancement in wireless technology according to characteristics of networks, certain cross-layer optimizations are performed.

• Some examples of wireless technology highlights the functionality of new network applications.

www.ee.surrey.ac.uk/CCSR20

Limitations of IPSec (continued..)

• Conflicts between IPSec and TCP PEPs– TCP PEPs work on two pieces of

information, TCP flow identification and sequence numbers.

– IPSec encapsulate whole TCP packet. • Traffic Analysis

– For functioning of upper layers, some information from headers is required at intermediate nodes.

– IPSec hides all upper layer headers.

www.ee.surrey.ac.uk/CCSR21

Limitations of IPSec (continued..)

• Traffic Engineering– Flow classification is essential in providing rich

classes of service and QoS (RED, RSVP). – The flow information present in upper layers

such ac TCP is hidden by IPSec. • Application Layer Agents/Proxies

– Some modern routers can serve the HTTP requests from their local cache in order to improve performance.

– They need information from upper layers like HTTP but, that is hidden by IPSec.

www.ee.surrey.ac.uk/CCSR22

Summary of IPSec Limitations and Conclusion

• All above defined mechanisms, try to access upper layers information for their working.

• IPSec works on end-to-end basis and encrypts all the upper layer information.

• So IPSec has basic functioning conflict with many intermediate devices.

• Need to resolve these issues for optimal performance.

www.ee.surrey.ac.uk/CCSR23

Problem Statement for ML-IPSec

• Develop a security scheme with below defined features:– Supports the services and applications

which have conflict with IPsec working. – Should grant trusted intermediate nodes

a secure, controlled and limited access to a selected portion of IP datagram.

– Should preserve the end-to-end security protection for user data.

www.ee.surrey.ac.uk/CCSR24

• Using a transport-layer security mechanism as an alternative to IPsec to provide security services.

• The transport-layer mechanism, such as secure sockets layer (SSL) or transport layer security (TLS) operates above TCP and works well with TCP PEP: – it encrypts the TCP data while leaving the TCP

header in unencrypted and unauthenticated form

• Limitations:– Vulnerable to traffic analysis attack– SSL/TLS only works on TCP but not on UDP so

the range of applications is limited

Approaches - Transport Layer Security

www.ee.surrey.ac.uk/CCSR25

• This approach tries to use transport layer security protocols, SSL/TLS, inside IPsec.

• SSL/TLS will protect the TCP data and IPSec will protect TCP header information

• Limitations:– wastage of resources because TCP data

will be encrypted twice by SSL/TLS and IPsec,

– IPsec still encrypts the whole TCP information including header and data part

Approaches – Tunnelling one security protocol

www.ee.surrey.ac.uk/CCSR26

• The transport-friendly ESP (TF-ESP) protocol format was proposed:– The TCP state information (such as flow

identifications and sequence numbers) are in a disclosure header outside the encryption scope, bbut authenticated.

• Limitations:– Vulnerable to traffic analysis attack– it does not work well with TCP spoofing

when a write access is needed

Approaches - Using a Transport Friendly ESP Format

www.ee.surrey.ac.uk/CCSR27

• IPsec protection can be applied twice, once between sender and security gateway and second time between security gateway and destination.

• Limitations:– It exposes the information to

intermediate nodes while confidentiality is only meant for end-to-end

Approaches – Splitting IPsec into Two Segments

www.ee.surrey.ac.uk/CCSR28

• ML-IPsec breaks the IP datagram into different parts and apply different security mechanisms on different parts:– one security mechanism for transport

header– different security mechanism for

application data• This approach allows the intermediate

nodes to co-exist with end-to-end IPsec

• Limitations:– More complex than IPsec

Approaches – Multi - Layer IP Security Protocol

www.ee.surrey.ac.uk/CCSR29

Standardization & Issues

• Many meetings were attended at IETF to present the idea of IPSec and internet draft was written.

• IETF Concerns: – Application domains is limited (Satellite

Networks only). – Implementation complexity is increased.

(shown feasible via implementation in IPSec).– Two more implementations required to prove

the points.• Key Management Complexity is major

issue.

www.ee.surrey.ac.uk/CCSR

Applications

30

www.ee.surrey.ac.uk/CCSR31

Principle of ML-IPSec Security Protection• Multilayer protection model:

• Divides IP datagram into zones

• Different protection schemes for different zones (e.g. SA, public/private keys, access control rules etc.)

www.ee.surrey.ac.uk/CCSR32

General Model of IPSec Processing

• .

MulticastKey Exchange

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Composite Security Association (CSA)

• Security Association

• one-way relationship between sender and receiver.

• defines set of parameters (e.g. sequence number, anti-replay window, lifetime of SA, Path MTU etc).

• Controls outbound, inbound processing.

www.ee.surrey.ac.uk/CCSR34

CSA Continued..

• CSA has two elements: – Zone Map: defines coverage of each

zone in IP datagram. – Zone List: is a list of all SAs for all zones.

(all stored in “Security Association Database (SAD)”).

www.ee.surrey.ac.uk/CCSR35

Zones and Zone Map• A zone is any portion of IP datagram under same

security protection.

• Entire IP datagram can be broken into zones.

• Zones can not overlap.

• A zone can be split into multiple sub zones (continuous part of IP datagram).

• A zone map is a mapping relationship between IP octets and zones.

• Remains Constant for a security relationship.

• zones that covers last part of IP datagram (data) should be variable according to size.

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Composite Security Association (CSA)

• Zone Map

• Zone List – In zone list area we show the SAs, their

parameters and access control.

www.ee.surrey.ac.uk/CCSR37

Zone List continued

• SA (designated)– Sequence Number Counter (64 bit)– Sequence Counter Overflow – Anti-Replay Window (64 bit)– Protocol mode (Transport or Tunnel)– Path MTU – Lifetime – Encryption algorithm (DES-CBC)– Encryption Key – Authentication algorithm (HMAC-MD5-32)– Authentication Key

www.ee.surrey.ac.uk/CCSR38

Outbound Processing (zone by zone)

Outbound: IP datagram

Zone map

Plain Text (masked and concatenated)

Encryption (using ESP)

Cipher Text (ESP)

Authentication

AH

ICV

SA

AH or ESP authentication data

ESP paylod data

www.ee.surrey.ac.uk/CCSR39

Inbound Processing (zone by zone)

Outbound: IP datagram

Zone map

Plain Text (masked and concatenated)

Decryption (using ESP)

Cipher Text (ESP)

Authentication

AH

ICV

SA

AH or ESP authentication data

ESP paylod data

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ESP Header

• Security Parameter Index: Identifies Security Association (SA).

• Sequence Number: Counts the packet sent.

• Encrypted Payload Data for Zone: contains the encrypted payload data (IP payload data, padding, pad length, Next Header).

• Authentication Data for Zone: Contains the Integrity Check Values (ICV) for each zone.

40

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Implementation and Evaluation

• Two different evaluations of ML-IPSec shall be performed. – Simulations based, to see the scalability

and reliability behaviour. • Impact of network bandwidth on

Performance ( SA establishment latency, TCP throughput and delay).

• Impact of different data packet size on performance and security protocol behaviour.

– Reference Implementation of ML-IPSec to see the overhead on real network. 41

www.ee.surrey.ac.uk/CCSR

Testbed Experiment Requirements

• Use Cases– IP Only: running standard IP with no security. – IPSec: running IPSec using ESP with

authentication mode enabled. – ML-IPSec (1 Zone) = IPSec– ML-IPSec (2 Zone) – ML-IPSec (3 Zones)

• The ML-IPSec experiment will be evaluated for processing delays, CPU overload and bandwidth overhead

42

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Testbed Experiment Requirements

Processing Delay • The processing delay will

be measured by taking following parameters into consideration: – One Host pinging other– Packet size will be fixed. – Processing Time will be

evaluated.

Bandwidth Overhead– One host generate and

send packets as fast as it can and other counting after receiving.

– CPU speed will be fixed.

– Network speed will be fixed.

– Throughput and protocol overhead relationship will be studied

Comparing CPU Overload• For evaluation of CPU

overhead environment will be configured as given below: – One host generate and

send packets as fast as it can and other counting after receiving.

– CPU speed will be fixed. – Network speed will be

fixed. . – Throughput and CPU load

relationship will be studied.

43

www.ee.surrey.ac.uk/CCSR

ML-IPSec Testbed

• Current Status– Fedora 13

Installed– Computers are

configured as shown in diagram.

• Future Plans– Need to configure

network’s speed. – Need to configure

NIST Net according to requirements.

44

www.ee.surrey.ac.uk/CCSR

Simulations & Standalone Implementation Plans

• NIST has performed IPSec simulations as part of project “NIIST(NIST IPSec and IKE Simulation Tool”.

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• SPD: Security Policy Database

• SAD: Security Association Database

• PF_Key: Generic Socket Key Management API

www.ee.surrey.ac.uk/CCSR

Simulations & Standalone Implementation Plans

46

www.ee.surrey.ac.uk/CCSR47

Conclusion

• Intermediate gateways can have access to partial IP datagram (e.g. TCP header) by partial keys.

• Can solve the conflict between IPSec and TCP PEPs being used in satellite networks.

• The current new and future networks can improve quality of service using fair queuing, differential services etc.

• IPSec problems are solved.