IP Security IPSec

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• IP Security(IPSec)
• Thomas LeeChief Technologist QAthomas.lee_at_qa.co
  m

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Agenda

• What is IPSec?
• How does IPSec Work?
• Configuring/Using IPSec
• Issues
• Best Practices
• Resources

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What is IPSec?

• Framework of open standards for ensuring private,
  secure communications over Internet Protocol (IP)
  networks
• IPSec provides authenticated and encrypted
  traffic between hosts at the IP protocol level
• Provides aggressive protection against private
  network and Internet attacks through end-to-end
  security.
• Protects communication between workgroups, local
  area network computers, domain clients and
  servers, branch offices (which might be
  physically remote), extranets, and roving
  clients.
• IPSec is the long-term direction for secure
  networking

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IPSec Objectives

• To protect the contents of IP packets.
• To provide a defense against network attacks
  through packet filtering
• To enforce trusted communication based on either
  local or central policy
• These objectives are met through the use of
  cryptography-based protection services, security
  protocols, dynamic key management and Windows
  Group Policy.

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Why IPSec?

• IPv4 not designed with security in mind
• Attacks possible with IPv4
• Eavesdropping
• Data modification
• Identity spoofing (IP address spoofing)
• Denial-of-service attack
• Man-in-the-middle attack
• These can be avoided by use of IPSec

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IPSec Protection

• Eavesdropping
• The Encapsulating Security Payload (ESP) protocol
  in IPSec provides data confidentiality by
  encrypting the payload of IP packets
• Data modification
• Cryptography-based keys, shared only by the
  sending and receiving computers, are use to
  create a cryptographic checksum for each IP
  packet.
• Modification of the data alters the checksum,
  which indicates to the receiving computer that
  the packet was modified in transit
• Identity spoofing
• IPSec allows verification of identities without
  exposing that information to an attacker.
• Mutual authentication establishes trust between
  the hosts.
• Man-in-the-middle attacks
• IPSec combines mutual authentication with shared,
  cryptography-based keys.
• Denial-of-service attacks
• IPSec uses IP packet filtering allow, secure, or
  block traffic based on IP address ranges, IP
  protocols, or even specific TCP/UDP ports.

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Agenda

• What is IPSec?
• How does IPSec Work?
• Configuring/using IPSec
• Issues
• Best Practices
• Resources

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How Components Interacts?
Application/Service client
Application Server or Gateway
IPSec Policy Agent
IKE (ISAKMP)
IKE (ISAKMP)
IPSec Driver
IPSec Driver
TCPIP
TCPIP
NIC
NIC

• Internet Key Exchange (IKE) - Identity Protect
  Mode defined in RFC 2409
• Phase 1 Main Mode establishes IKE SA trusted
  channel between systems, negotiation establishes
  encrypted channel, mutual trust, and dynamically
  generates shared secret key (master key)
• Phase 2 Quick Mode establishes IPSec SAs for
  data protection, one SA for each direction
  identified by packet label (SPI), algorithms and
  packet formats agreed, generates shared session
  secret keys derived from master key

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IPSec Policy

• One Active IPSec Policy
• Multiple IPSec Policies can be defined
• Policy Consists of
• ISAKMP Policy
• IPSec rules
• An IPSec policy can have many rules
• IPSec Rules
• Filter identifies the traffic to
  secure/drop/etc
• Filter action drop, deny, authenticate, encrypt
• Authentication, encryption, etc

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IPSec Policy Components

• Polling interval used to detect changes in policy
  
• IKE parameters, such as encryption key lifetimes.
• IPSec behavior for the policy
• The types of traffic to which an action is
  applied
• Permit, block, or secure
• Kerberos, certificate, or preshared key
• LAN, Dialup, or both

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IPSec packet filtering

• Filters allow and block traffic
• Filters can overlap
• Most specific match determines action
• NO stateful inspection
• Example to open only port 80 on the IIS

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Negotiation of Protection

• Require two messages
• Initiator to Responder (contains proposals)
• Responder to Initiator (contains a selected
  proposal)
• Details later!
• Protection suites

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IPSec Modes

• Transport mode
• Used for IPSec peers doing end-to-end security
• Provides protection for upper-layer protocol data
  units (PDUs)
• Tunnel mode
• Used by network routers to protect IP datagrams
  passing across insecure network
• Provides protection for entire IP datagrams

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Security Associations

• Combination of mutually agreed security services,
  protection mechanisms, and cryptographic keys
• ISAKMP SA
• IPSec SAs
• One for inbound traffic
• One for outbound traffic
• Security Parameters Index (SPI)
• Helps identify an SA
• Creating SAs
• Main Mode for ISAKMP SA
• Quick Mode for IPSec SAs

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Agenda

• What is IPSec?
• How does IPSec Work? (at the packet level!)
• Configuring/using IPSec
• Issues
• Best Practices
• Resources

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Internet Key Exchange

• How IPSec peers establish SAs
• Combines ISAKMP and the Oakley Key Determination
  Protocol
• ISAKMP is used to identify and authenticate
  peers, manage SAs, and exchange key material
• Oakley Key Determination Protocol is used to
  generate secret key material for secure
  communications (Diffie-Hellman key exchange
  algorithm)

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ISAKMP Message Structure
IP header
ISAKMP payloads
UDP header
ISAKMP header
UDP message
IP datagram
ISAKMP uses UDP source/destination port 500
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ISAKMP Header
Initiator Cookie Responder Cookie Next
Payload Major Version Minor Version Exchange
Type Flags Message ID LengthA
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ISAKMP Payloads

• SA
• Proposal
• Transform
• Vendor ID
• Nonce
• Key Exchange
• Notification
• Delete
• Identification
• Hash
• Certificate Request
• Certificate
• Signature

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IPSec Headers

• IPSec Headers live inside IP datagrams and define
  IPSec contents
• Authentication Header (AH)
• Provides data origin authentication, data
  integrity, and replay protection for the entire
  IP datagram
• Encapsulating Security Payload (ESP)
• Provides data origin authentication, data
  integrity, replay protection, and data
  confidentiality for the ESP-encapsulated portion
  of the packet

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AH Transport Mode
IP
Upper layer PDU
IP
AH
Upper layer PDU
Authenticated
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AH Tunnel Mode
IP
Upper layer PDU
AH
IP
IP (new)
Upper layer PDU
Authenticated
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Authentication Header (AH)
Next Header Payload Length Reserved Security
Parameters Index Sequence Number Authentication
Data Payload
. . .
. . .
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ESP Transport Mode
IP
Upper layer PDU
IP
ESP
ESP
Auth Data
Upper layer PDU
Encrypted
Authenticated
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ESP with AH Transport Mode
IP
Upper layer PDU
IP
ESP
ESP
ESP Auth
AH
Upper layer PDU
Encrypted
Authenticated with ESP
Authenticated with AH
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ESP Tunnel Mode
IP
Upper layer PDU
IP (new)
ESP
ESP
Auth Data
IP
Upper layer PDU
Encrypted
Authenticated
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ESP Header and Trailer
Security Parameters Index Sequence
Number Payload Padding Padding Length Next
Header Authentication Data
. . .
. . .
. . .
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Internet Key Exchange

• Standard that defines a mechanism to establish
  SAs
• Combines ISAKMP and the Oakley Key Determination
  Protocol
• ISAKMP is used to identify and authenticate
  peers, manage SAs, and exchange key material
• Oakley Key Determination Protocol is used to
  generate secret key material for secure
  communications (Diffie-Hellman key exchange
  algorithm)

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Main Mode Negotiation

• Phases of main mode negotiation
• 1. Negotiation of protection suites
• 2. A Diffie-Hellman exchange
• 3. Authentication
• Six ISAKMP messages
• 1, 2 all authentication types
• 3, 4, 5, and 6 - vary by Authentication type

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Authentication in MM Negotiation

• Kerberos Authentication
• Kerberos Tokens exchanged and validated
• Certificate Authentication
• Certificates and signatures exchanged and
  validated
• Preshared Key Authentication
• Hash payloads exchanged and validated

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Main Mode Negotiation Messages

• Message 1
• Sent by initiator
• Contains proposed security association details,
  vendor ID
• Message 2
• Sent by responder
• Contains acceptable SA proposal, vendor ID
• These messages negotiate
• Encryption (DES, 3DES)
• Identity Algorithm (MD5, SHA-1)
• Authentication Method (Kerberos, Pre-shared key,
  Certificate)
• Diffie-Hellman group (768-bit, 1024-bit, 2048-bit)

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Main Mode Kerberos Authentication

• Message 3 - Sent from initiator
• Contains key exchange, Nonce, initiators
  Kerberos Token, NAT Discovery information
• Message 4 - Sent from responder
• Contains key exchange, Nonce, responders
  Kerberos Token , NAT Discovery information
• Message 5 - Sent from initiator (encrypted)
• Contains identification (of initiator), plus hash
• Message 6 - Sent from responder (encrypted)
• Contains identification (of responder), plus hash

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Main Mode Certificate Authentication

• Message 3 - Sent from initiator
• Contains key exchange, Nonce, NAT Discovery
  information
• Message 4 - Sent from responder
• Contains key exchange, Nonce, NAT Discovery
  information
• Also contains certificate request (list of
  trusted root CAs)
• Message 5 - Sent from initiator (encrypted)
• Contains Initiators Certificate, signature
• Message 6 - Sent from responder (encrypted)
• Contains Responders certificate, signature

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Main Mode Pre-Shared Key Authentication

• Message 3 - Sent from initiator
• Contains Key Exchange, Nonce, NAT Discovery
• Message 4 - Sent from responder
• Contains Key Exchange, Nonce, NAT Discovery
• Message 5 - Sent from initiator (encrypted)
• Contains Identification (of initiator), hash
• Message 6 - Sent from responder (encrypted)
• Contains Identification (of responder), hash

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Quick Mode Negotiation

• Four ISAKMP messages to determine traffic to be
  secured and how it is secured
• Initiator and responder exchange
• SA payloads (how to secure traffic)
• Identification payloads (the traffic to secure)

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Demo
IPSec On the Wire Or Fun With NetMon!
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Agenda

• What is IPSec?
• How does IPSec Work?
• Configuring/Using IPSec
• Issues
• Best Practices
• Resources

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Issues with IPSec

• Need for machine certificates
• Interoperability
• Performance/Overhead
• NAT traversal

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Need for Machine Certificates/Keys

• IPSec is based on machine to machine
  communication
• User credentials not used
• You therefore need machine certificates
• For Kerberos
• Machine is the security principal
• Only works for Windows 2000/2003/XP
• For Certificate based authentication
• How to manage/deliver certificates

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Performance/Overhead

• IPSec incurs three sets of overhead
• Startup
• Wire protocol overheads
• Speed of encryption
• Start up over-head
• Main Mode 6 packets
• Quick Mode 10 packets

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Wire Protocol Overhead
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IPSec Hardware Acceleration

• IPSec per-packet hardware acceleration for 10/100
  Ethernet
• Client/Svr cards retail circa 100
• 3Com
• 3CR990B-97 - 10/100 UTP
• 3CR990B-FX-97 10/100 Fiber
• Wire Speed IPSec
• Max 75 SAs supported
• http//www.3com.com/other/pdfs/products/en/400833.
  pdf
• - Or -
• http//tinyurl.com/3er3f
• Intel
• Intel PRO/100 S Desktop/Server
• http//www.intel.com/network/connectivity/resource
  s/doc_library/documents/pdf/intel_ipsec_final.pdf
• - Or -
• http//tinyurl.com/37hcn

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XP IPSec Performance Improvements

• Doubled number of new SAs per minute
• Reliable delete handling in IKE
• Doubled packet filtering speed (throughput)
• Client LDAP retrieval of AD policy 5 times faster
  than Windows 2000
• Both Intel and 3Com 32bit x86 10/100Ethernet
  offload support shipping in the box

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IPSec NAT-T

• Network Address Translators (NATs) invalidate
  IPSec packet protections
• IPSec NAT Traversal (NAT-T)
• Encapsulates ESP-protected payloads with a UDP
  header
• Defines additional Main Mode payloads to detect
  IPSec NAT-T-capable peers and whether either is
  behind a NAT
• Defines an additional Quick Mode payload to
  indicate untranslated addresses
• Allows ESP-protected traffic to traverse a NAT

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Agenda

• What is IPSec?
• How does IPSec Work?
• Configuring/Using IPSec
• Issues
• Best Practices
• Resources

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Scripting

• NETSH C IPSEC with Windows Server 2003
• Netsh IPsec
• No dump command ?
• It is included
• It does nothing!
• Help text has few examples
• Error messages generally totally unhelpful
• Lots of trial and error seems to be needed!

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Best Practices

• Establish an IP Security deployment plan
• Avoid Pre-shared keys
• Configuration of certificate requests
• Script, script, script