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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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filtersfiltersfiltersfilters
How Components Interacts?
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
NICNIC
TCPIPTCPIP
ApplicationApplicationServer or GatewayServer or Gateway
IPSecIPSecDriverDriver
IPSecIPSecPolicyAgentPolicyAgentIKE (ISAKMP)IKE (ISAKMP)
IPSecIPSecDriverDriver
IPSecIPSecPolicy Policy AgentAgent IKE (ISAKMP)IKE (ISAKMP)
NICNIC
TCPIPTCPIP
Application/ServiceApplication/Serviceclientclient
““IKE Responder”IKE Responder”““IKE Initiator”IKE Initiator”
UDP port 500 UDP port 500 negotiationnegotiation 1 IKE SA 1 IKE SA
2 IPSec SAs2 IPSec SAs
IP protocol 50/51IP protocol 50/51
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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:
From IP To IP Protocol Src Port Dest Port Action
Any My Internet IP Any n/a n/a Block
Any My Internet IP TCP Any 80 Permit
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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:
Attribute Attribute Value
Encryption algorithm DES, 3DES, Null
Integrity algorithm MD5, SHA-1, Null
Authentication method Kerberos, preshared key, certificate
Diffie-Hellman group Group 1 (768-bit), Group 2 (1024-bit)
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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 message
IP datagram
UDP header
ISAKMPheader
ISAKMP uses UDP source/destination port 500
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ISAKMP Header
Initiator CookieResponder Cookie
Next PayloadMajor VersionMinor Version
Exchange TypeFlags
Message IDLengthA
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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
Authenticated
Upper layer PDU
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AH Tunnel Mode
AH
Authenticated
IP
IP
IP (new)
Upper layer PDU
Upper layer PDU
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Next HeaderPayload Length
ReservedSecurity Parameters Index
Sequence NumberAuthentication Data
Payload
. . .
Authentication Header (AH)
. . .
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ESP Transport Mode
IP ESP ESPAuthData
Encrypted
Authenticated
IP Upper layer PDU
Upper layer PDU
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ESP with AH Transport Mode
IP ESP ESPESPAuth
Encrypted
Authenticated with AH
IP
AH
Upper layer PDU
Upper layer PDU
Authenticated with ESP
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ESP Tunnel Mode
IP (new) ESP ESPAuthData
IP
Encrypted
Authenticated
IP Upper layer PDU
Upper layer PDU
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Security Parameters IndexSequence Number
Payload
PaddingPadding Length
Next Header
Authentication Data
. . .
. . .
. . .
ESP Header and Trailer
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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, initiator’s Kerberos Token, NAT
Discovery information
Message 4 - Sent from responder• Contains key exchange, Nonce, responder’s 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 Initiator’s Certificate, signature
Message 6 - Sent from responder (encrypted)• Contains Responder’s 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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IPSec On the WireIPSec On the WireOrOr
Fun With NetMon!Fun With NetMon!
Demo
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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
Mode Inbound Outbound Total Bytes
Normal IP Traffic 2,084,031 94,646,227 96,730,257
AH Traffic 2,700,627 96,174,275 98,874,902
ESP Traffic 2,867,099 96,941,132 99,808,231
AH Overhead 616,596 1,528,048 2,144,645
ESP Overhead 783,068 2,294,905 3,077,974
% AH Overhead 29.59% 1.61% 2.22%
% ESP Overhead 37.57% 2.42% 3.18%
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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/resources/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
46
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
