Mr. Gopal Sakarkar

Security ConceptPart-3

Mr.Gopal Sakarkar

Mr. Gopal Sakarkar

What is a Firewall?a choke point of control and monitoring

interconnects networks with differing trust

imposes restrictions on network services

– only authorized traffic is allowed

auditing and controlling access

– can implement alarms for abnormal behavior

implement VPNs using IPSec

must be immune to penetration

Mr. Gopal Sakarkar

Firewall Design Principles

Centralized data processing system , with a central

mainframe supporting number of directly connected

terminals.

LAN’s interconnected PCs and terminals to each

other and the mainframe.

Premises network that consisting of a number of

LANs, interconnecting PCs , servers .

Enterprise –wide network consisting of multiple ,

geographical distributed premises network

interconnected by private WAN.

Mr. Gopal Sakarkar

Characteristics of Firewall

All traffic from inside to outside and vice

versa must pass through the firewall.

Only authorize traffic as defined by the

local security policy will be allowed to pass.

Firewall itself is immune to penetration .

Mr. Gopal Sakarkar

Firewall Techniques for control

Access

Service control : the firewall may filter traffic on the

basis of IP address. It determines the types of Internet

services that can be accessed inbound or outbound.

Direction Control: It determiner the direction in which

particular service request may be initiated and allowed to

flow through the firewall.

User Control : Controls access to a service according

to which user is attempting to access it. It is typically

applied to local user only.

Behavior control : Controls how particular service are

used. The firewall may filter e-mail to eliminated spam or it

may enable external access to specific portion of the

infromation.

Mr. Gopal Sakarkar

Firewall Limitations

cannot protect from attacks bypassing it

cannot protect against internal threats– eg unhappy or plan employees

cannot protect against transfer of all virus

infected programs or files– because of huge range of O/S & file types

Mr. Gopal Sakarkar

Types of Firewalls

1.Packet filtering router

2.Application level gateways

3.Circuit- level gateways

Mr. Gopal Sakarkar

Firewalls – Packet Filters

Mr. Gopal Sakarkar

Firewalls – Packet Filters

simplest, fastest firewall component It applies a set of rule to each incoming and outgoing IP packetExamine each IP packet and permit or deny according to rules Filtering rules are for

1. Source IP address : the IP address of the system that originated the IP packet.

2. Destination IP address : the IP address of the systems that the IP packet is trying to reach

Mr. Gopal Sakarkar

Firewalls – 2. Application Level

Gateway (or Proxy)have application specific gateway also called a proxy serverhas a full access to protocol

– user requests service from proxy– proxy validates request as legal– then actions request and returns result to user– can log / audit traffic at application level

need separate proxies for each service

– some services naturally support proxyingEg. Feedback Application, online examination

Application ,MIS etc

Mr. Gopal Sakarkar

Firewalls – 2. Application Level

Gateway (or Proxy)Application level gateways tend to be more secure

than packet filters because it scrutinize a fewallowable applications.

Mr. Gopal Sakarkar

Firewalls – 3.Circuit Level

Gateway

This is for a stand-alone system.Imposes security by limiting which such connections are allowed.once created, usually relays traffic without examining contents.Typically used by trust internal users for allowing general outbound

connections

Mr. Gopal Sakarkar

Firewalls – 3.Circuit Level

Gateway

It has two TCP connection , one between itself and a TCP user on an

inner host and one between itself and a TCP user on an outside host.

Mr. Gopal Sakarkar

Data Access Control

• Through the user access control procedure

(log on), a user can be identified to the system

• There can be a profile that specifiespermissible operations and file accesses

• The operating system can enforce rules basedon the user profile.

Mr. Gopal Sakarkar

Data Access Control

• General models of access control:

– Access matrix

– Access control list

– Capability list

Mr. Gopal Sakarkar

Data Access Control• Access Matrix

Mr. Gopal Sakarkar

Data Access Control

• Access Matrix: Basic elements of the model

– Subject: An entity capable of accessing objects, the

concept of subject associate with that of process (e.g.

Application soft.)

– Object: Anything to which access is controlled (e.g. files,

programs)

– Access right: The way in which an object is accessed by a

subject (e.g. read, write, execute)

Mr. Gopal Sakarkar

Data Access Control

• Access Control List: Decomposition of the

matrix by columns.

• One process , many program. E.g. CD Writer is one process in which writing is one

program and data verification of write data is second program.

Mr. Gopal Sakarkar

Data Access Control

• Access Control List

– An access control list, lists users and their

permitted access right

– The list may contain a default or public entry

Mr. Gopal Sakarkar

Data Access Control

• Capability list: Decomposition of the matrix by rows

A capability list specifies authorized objects and operations for a user.

Mr. Gopal Sakarkar

Trusted Systems

• Trusted Systems

– Protection of data and resources on the basis of

levels of security (e.g. military)

– In military, information is categorize as

unclassified , confidential , secret , top secret .

– Users can be granted clearances to access certain

categories of data.

Mr. Gopal Sakarkar

Trusted Systems

• Multilevel security

– In which a subject at high level may not conveyinformation to a subject at low level

• A multilevel secure system must enforce:

– No read up: A subject can only read an object of less or equal security level (Simple Security Property)

– No write down: A subject can only write into an object of greater or equal security level (*-Property)

Mr. Gopal Sakarkar

Trusted Systems

• Reference Monitor Concept: Multilevel

security for a data processing system

Mr. Gopal Sakarkar

The Concept of

Trusted Systems

• Reference Monitor

– Controlling element in the hardware and operatingsystem of a computer that regulates the access ofsubjects to objects on basis of security parameters

– The Reference monitor has access to a file(security kernel database)

– The monitor enforces the security rules (no readup, no write down)

Mr. Gopal Sakarkar

Trusted Systems

• Properties of the Reference Monitor

– Complete mediation: Security rules are enforcedon every access

– Isolation: The reference monitor and database areprotected from unauthorized modification

– Verifiability: The reference monitor’s correctnessmust be provable (mathematically)

– i.e. it is possible to demonstrate mathematically that the referencemonitor enforce the security rules and provides complete mediation andisolation.

Mr. Gopal Sakarkar

Trusted Systems

• A system that can provide such verifications

(properties) is referred to as a trusted system

Mr. Gopal Sakarkar

Summary

Data Access Control is use to control procedure

by which user can be identified to the system.

Trusted Systems is a computer and operating system that can br verified to

implement a given security policy.

Mr. Gopal Sakarkar

Mr. Gopal Sakarkar

Outline

• IP Security Overview

• IP Security Architecture

• Authentication Header

• Encapsulating Security Payload

• Combinations of Security Associations

• Key Management

Mr. Gopal Sakarkar

IP Security Overview

IPSec is not a single protocol. Instead,

IPSec provides a set of security

algorithms plus a general framework

that allows a pair of communicating

entities to use whichever algorithms

provide security appropriate for the

communication.

Mr. Gopal Sakarkar

IP Security Overview

• Applications of IPSec

– Secure branch office connectivity over the

Internet

– Secure remote access over the Internet

– Establsihing extranet and intranet connectivity

with partners

– Enhancing electronic commerce security

Mr. Gopal Sakarkar

IP Security Scenario

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IP Security Overview

• Benefits of IPSec– When IP Sec is implemented in a firewall , it provide

strong security that can be applied to all trafficcrossing the perimeter.

– IPSec in a firewall is resistant to bypass, if all trafficfrom the outside must use IP.

– IPSec can be transparent to end user. No need totrian user on security mechanisms.

– IPSec can provide security for individual users ifneeded.

Mr. Gopal Sakarkar

IP Security Architecture

Mr. Gopal Sakarkar

IPSec Architecture Overview• Architecture : Cover the general concept , security

requirements, definitions and mechanisms defining IPSec

technology.

• Encapsulating Security Payload (ESP) :Cover the packet

format and general issues related to the use of the ESP.

• Authentication Header (AH): Cover the packet format and

general issues related to the use of AH for packet

authentication.

• Key management : A set of documents that describe how

various authentication algorithms are used for AH.

• Domain of Interpretation (DOI): Contains values needed for

the document to relate to each other.

Mr. Gopal Sakarkar

IPSec Services

• Access Control

• Connectionless integrity

• Data origin authentication

• Rejection of replayed packets

• Confidentiality (encryption)

• Limited traffic flow confidentiallity

Mr. Gopal Sakarkar

Security Associations (SA)

• It is a one way relationsship between a

sender and a receiver that provide security

services to a traffic.

• Identified by three parameters:

– Security Parameter Index (SPI)

– Destination IP address

– Security Protocol Identifier :– This indicate whether the association is an AH or ESP security

association

(SPI) is an identification tag

added to the header while using

IPsec for tunnelling the IP traffic.

This tag helps the kernel discern

between two traffic streams

where different encryption rules

and algorithms may be in use

Mr. Gopal Sakarkar

Authentication Header

• Provides support for data integrity and authentication

(MAC code) of IP packets.

• Guards against replay attacks.

Conti…

What are replay attacks?

• Replay attacks are the network attacks in which an attacker spies

the conversation between the sender and receiver and takes the

authenticated information e.g. sharing key and then contact to the

receiver with that key. In Replay attack the attacker gives the proof

of his identity and authenticity.

Example:

Suppose in the communication of two parties A and B; A is sharing

his key to B to prove his identity but in the meanwhile Attacker C

eavesdrop the conversation between them and keeps the

information which are needed to prove his identity to B. Later C

contacts to B and prove its authenticity.

Mr. Gopal Sakarkar

• Next header (8bits):

identifies the type of header immediately following this header.

• Payload length (8bits):

it is a length of Authentication Header in 32 bits words minus 2.

• Reserved (16bits) :

For future use.

• Security parameter index(SPI) (32 bits):

Identifies a security association.

• Sequence Number(32bits):

It is used to increase counter value.

• Authentication data (Variable) : A variable length field that contain the Integrity

Check Value. Mr. Gopal Sakarkar

Authentication Header

Mr. Gopal Sakarkar

End-to-end VS End-to-Intermediate

Authentication

Mr. Gopal Sakarkar

Encapsulating Security Payload• ESP provides confidentiality services

• ESP provides confidentiality of message contens

• ESP provide limited traffic flow confidentiality

• Designed to provide both confidentiality

and integrity protection

• Everything after the IP header is encrypted

• The ESP header is inserted after the IP

header

Mr. Gopal Sakarkar

Encapsulating Security Payload

Mr. Gopal Sakarkar

Encryption and Authentication

Algorithms• Encryption:

– Three-key triple DES

– RC5

– IDEA

– Three-key triple IDEA

– CAST

– Blowfish

• Authentication:– HMAC-MD5-96

– HMAC-SHA-1-96

Mr. Gopal Sakarkar

TCP/IP Example

Basics: OSI 7-Layer RM

Congratulation for selecting papers

in

National Conference, Pune

Mr. Gopal Sakarkar

Mr. Gopal Sakarkar

IPv4 Header

IPv4 Header

• Internet Protocol version 4 (IPv4) is the fourth version in the development of the

Internet Protocol (IP) and the first version of the protocol to be widely deployed.

• It is one of the core protocols of standards-based internetworking methods of the

Internet, and routes most traffic in the Internet.

• IPv4 is a connectionless protocol for use on packet-switched networks.

• A connectionless protocol describes the communication between two network end

points where a message is sent from one end point to another without a prior

arrangement.

• At one end, the device transmits data to the other before ensuring that the device on

the other end is ready to use.

Mr. Gopal Sakarkar

60

IPv4 Header Fields• Version: IP Version

– 4 for IPv4

– 6 for IPv6

• HLen: Header Length– 32-bit words

• TOS: Type of Service– Priority information

• Length: Packet Length– Bytes (including header)

• Header format can change with versions– First byte identifies version

– IPv6 header are very different – will see later

• Length field limits packets to 65,535 bytes– In practice, break into much smaller packets for network performance

considerations

0 4 8 12 16 19 24 28 31

version HLen TOS Length

Identifier Flags Offset

TTL Protocol Checksum

Source Address

Destination Address

Options (if any)

Data

61

IPv4 Header Fields• Identifier, flags, fragment

offset used primarily forfragmentation

• Time to live– Must be decremented

at each router

– Packets with TTL=0 are thrown away

– Ensure packets exit the network

• Protocol– Demultiplexing to higher layer protocols

– TCP = 6, ICMP = 1, UDP = 17…

• Header checksum– Ensures some degree of header integrity

– Relatively weak – only 16 bits

• Options– E.g. Source routing, record route, etc.

– Performance issues at routers• Poorly supported or not at all

0 4 8 12 16 19 24 28 31

version HLen TOS Length

Identifier Flags Offset

TTL Protocol Checksum

Source Address

Destination Address

Options (if any)

Data

62

IPv4 Header Fields• Source Address

– 32-bit IP address of

sender

• Destination Address

– 32-bit IP address of

destination

0 4 8 12 16 19 24 28 31

version HLen TOS Length

Identifier Flags Offset

TTL Protocol Checksum

Source Address

Destination Address

Options (if any)

Data

Why IPv6?

• Deficiency of IPv4

• Address space exhaustion

• New types of service Integration

–Multicast

–Quality of Service

– Security

–Mobility (MIPv6)

• Header and format limitations

Advantages of IPv6 over IPv4

• Larger address space

• Better header format

• New options

• Allowance for extension

• Support for resource allocation

• Support for more security

• Support for mobility

Mr. Gopal Sakarkar

IPv6 Header

Avoid Checksum Redundancy

Fragmentation at end-to-end

The following list describes the function of each header field.

• Version – 4-bit Version number of Internet Protocol = 6.

• Traffic Class – 8-bit traffic class field.

• Flow Label – 20-bit field.

• Payload Length – 16-bit unsigned integer, which is the rest of the packet

that follows the IPv6 header, in octets.

• Next Header – 8-bit selector. Identifies the type of header that immediately

follows the IPv6 header. Uses the same values as the IPv4 protocol field.

• Hop Limit – 8-bit unsigned integer. Decremented by one by each node that

forwards the packet. The packet is discarded if Hop Limit is decremented to

zero.

• Source Address – 128 bits. The address of the initial sender of the packet.

• Destination Address – 128 bits. The address of the intended recipient of

the packet. The intended recipient is not necessarily the recipient if an

optional Routing Header is present.

Mr. Gopal Sakarkar

Video OSI-7 Layer

Video Lectures

• Complete working of Internet

• OSI Model with packets, IPs, Firewalls

ect.

Mr. Gopal Sakarkar

Mr. Gopal Sakarkar

WEB Security

Mr. Gopal Sakarkar

Outline

• Web Security Considerations

• Secure Socket Layer (SSL) and Transport

Layer Security (TLS)

• Secure Electronic Transaction (SET)

• Recommended Reading and WEB Sites

Mr. Gopal Sakarkar

Web Security Considerations

• The WEB is very visible.

• Complex software hide many security

flaws.

• Web servers are easy to configure and

manage.

• Users are not aware of the risks.

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Security facilities in the TCP/IP

protocol stack

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SSL and TLS

• SSL was originated by Netscape

• TLS working group was formed within

IETF

• First version of TLS can be viewed as an

SSLv3.1

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SSL Architecture

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SSL Record Protocol Operation

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SSL Record Format

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SSL Record Protocol Payload

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Handshake Protocol

• The most complex part of SSL.

• Allows the server and client to

authenticate each other.

• Negotiate encryption, MAC algorithm and

cryptographic keys.

• Used before any application data are

transmitted.

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Handshake Protocol Action

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Transport Layer Security

• The same record format as the SSL record format.

• Defined in RFC 2246.

• Similar to SSLv3.

• Differences in the:– version number

– message authentication code

– pseudorandom function

– alert codes

– cipher suites

– client certificate types

– certificate_verify and finished message

– cryptographic computations

– padding

Mr. Gopal Sakarkar

Secure Electronic Transactions

• An open encryption and security specification.

• Protect credit card transaction on the Internet.

• Companies involved:– MasterCard, Visa, IBM, Microsoft, Netscape, RSA,

Terisa and Verisign

• Not a payment system.

• Set of security protocols and formats.

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SET Services

• Provides a secure communication channel

in a transaction.

• Provides trust by the use of X.509v3 digital

certificates.

• Ensures privacy.

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SET Overview

• Key Features of SET:

– Confidentiality of information

– Integrity of data

– Cardholder account authentication

– Merchant authentication

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SET Participants

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Sequence of events for

transactions1. The customer opens an account.

2. The customer receives a certificate.

3. Merchants have their own certificates.

4. The customer places an order.

5. The merchant is verified.

6. The order and payment are sent.

7. The merchant request payment authorization.

8. The merchant confirm the order.

9. The merchant provides the goods or service.

10. The merchant requests payments.

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Dual Signature

H(OI))]||)(([ PIHHEDScKR

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Payment processing

Cardholder sends Purchase Request

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Payment processing

Merchant Verifies Customer Purchase Request

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Payment processing

• Payment Authorization:

– Authorization Request

– Authorization Response

• Payment Capture:

– Capture Request

– Capture Response

Mr. Gopal Sakarkar

Recommended Reading and

WEB sites• Drew, G. Using SET for Secure Electronic

Commerce. Prentice Hall, 1999

• Garfinkel, S., and Spafford, G. Web Security &

Commerce. O’Reilly and Associates, 1997

• MasterCard SET site

• Visa Electronic Commerce Site

• SETCo (documents and glossary of terms)