Information management 1 Groep T Leuven – Information department 1/26 IPSec IP Security (IPSec)

Information management 2 Groep T Leuven – Information department 2/26 IP Security (IPSec) IPSec overview Authentication Header (AH) Encapsulating Security Payload (ESP) Internet Key Exchange (IKE) Main Mode negotiation Quick Mode negotiation Retransmit behavior

Information management 3 Groep T Leuven – Information department 3/26 Overall Architecture (RFC 1825) Framework for security protocols to provide: –Data integrity –Data authentication –Data confidentiality –Security association management –Key management

Information management 4 Groep T Leuven – Information department 4/26 Authentication Header (RFC 1826) Data integrity—no twiddling of bits Origin authentication—definitely came from router Uses keyed-hash mechanism Does not provide confidentiality IP Header plus Data AH Authentication Data (00ABCDEF) Authentication Data (00ABCDEF) IP Header plus Data Router IP HDR Data Router

Information management 5 Groep T Leuven – Information department 5/26 Encapsulating Security Payload (RFC 1827) Confidentiality Data origin authentication Data integrity Replay protection (optional) All Data-Encrypted Router

Information management 6 Groep T Leuven – Information department 6/26 Security Association (SA) Router Firewall Insecure Channel Agreement between two entities on method to communicate securely Unidirectional—two way communication consists of two SAs

Information management 7 Groep T Leuven – Information department 7/26 IKE Policy Negotiation Encryption Algorithm, Hash Algorithm, and Method of Authentication 3DES, MD5, and RSA Signatures, or IDEA, SHA, and DSS Signatures, or Blowfish, SHA, and RSA Encryption 3DES, MD5, and RSA Signatures, or IDEA, SHA, and DSS Signatures, or Blowfish, SHA, and RSA Encryption IDEA, SHA, and DSS Signatures ISAKMP Policy Tunnel

Information management 8 Groep T Leuven – Information department 8/26 IPSec Model Device authentication –Crypto devices obtain digital certificates from CAs Authorization –Packet selection via ACLs –Security Association (SA) established via ISAKMP/OAKLAY Privacy and integrity –IPSec-based encryption and digital signature Certificate Authority Digital Certificate SA Authenticated Encrypted Tunnel Encrypted Clear Text Internal Network Digital Certificate IKE Session

Information management 9 Groep T Leuven – Information department 9/26 IPsec Protocols and Formats Headers Key Exchange Modes Encryption Hashing Headers Key Exchange Modes Encryption Hashing Authentication Header Encapsulating Security Payload ISAKMP/Oakley Diffie-Hellman Transport Tunnel Authentication Header Encapsulating Security Payload ISAKMP/Oakley Diffie-Hellman Transport Tunnel Integrity, authentication Adds confidentiality Negotiates security parameters Uses digital certificates Generates shared secret keys IP payload only, Layer 4 is obscured Both end systems need IPsec Entire datagram No changes to intermediate systems DES, 3DES, RC4, IDEA, AES... HMAC MD5, HMAC SHA1 Integrity, authentication Adds confidentiality Negotiates security parameters Uses digital certificates Generates shared secret keys IP payload only, Layer 4 is obscured Both end systems need IPsec Entire datagram No changes to intermediate systems DES, 3DES, RC4, IDEA, AES... HMAC MD5, HMAC SHA1

Information management 10 Groep T Leuven – Information department 10/26 IPSec Modes IP HDR Encrypted IP HDR DATA IPSec HDR DATA IP HDR DATA IPSec HDR IP HDR New IP HDR Encrypted DATA Tunnel Mode Transport Mode

Information management 11 Groep T Leuven – Information department 11/26 Tunnel and Transport Modes Transport mode for end-to-end session Tunnel mode for everything else HR Server Joe’s PC Transport Mode Tunnel Mode

Information management 12 Groep T Leuven – Information department 12/26 Ipsec—Standards Based Internet Campus Firewall VLANs IPsec Dial

Information management 13 Groep T Leuven – Information department 13/26 IPSec Overview Router to Router Router to Firewall PC to Router PC to Server Proposed Internet standard for IP- layer cryptography with IPv4 and IPv6

Information management 14 Groep T Leuven – Information department 14/26 IPSec Process Initiating the IPSec session –Phase one—exchanging keys –Phase two—setting up security associations Encrypting/decrypting packets Rebuilding security associations Timing out security associations

Information management 15 Groep T Leuven – Information department 15/26 Initiating the IPSec Session Phase One — ISAKMP Internet Security Association Key Management Protocol (ISAKMP) Both sides need to agree on the ISAKMP security parameters (ISAKMP SADB) –ISAKMP parameters Encryption algorithm Hash algorithm Authentication method Diffie-Hellman modulus Group lifetime

Information management 16 Groep T Leuven – Information department 16/26 Initiating the IPSec Session Phase Two Both sides need to agree on the IPSec security parameters (IPSec SADB) IPSec parameters –IPSec peer Endpoint of IPSec tunnel –IPSec proxy Traffic to be encrypted/decrypted –IPSec transform Encryption and hashing –IPSec lifetime Phase two SA regeneration time

Information management 17 Groep T Leuven – Information department 17/26 Encrypting and Decrypting Packets Phase one and phase two completes Security Associations (SA) are created at both IPSec endpoints Using the negotiated SADB information –Outbound packets are encrypted –Inbound packets are decrypted

Information management 18 Groep T Leuven – Information department 18/26 Rebuilding Security Associations To ensure that keys are not compromised they are periodically refreshed Security associations will be rebuilt when: –The lifetime expires, or –Data volume has been exceeded, or –Another SA is attempted with identical parameters

Information management 19 Groep T Leuven – Information department 19/26 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

Information management 20 Groep T Leuven – Information department 20/26 IPSec Headers 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

Information management 21 Groep T Leuven – Information department 21/26 IPSec Modes Transport mode –Typically used for IPSec peers doing end-to-end security –Provides protection for upper-layer protocol data units (PDUs) Tunnel mode –Typically used by network routers to protect IP datagrams –Provides protection for entire IP datagrams

Information management 22 Groep T Leuven – Information department 22/26 AH Transport Mode IPUpper layer PDU IPAH Authenticated Upper layer PDU

Information management 23 Groep T Leuven – Information department 23/26 AH Tunnel Mode AH Authenticated IP IP (new) Upper layer PDU

Information management 24 Groep T Leuven – Information department 24/26 ESP Transport Mode IPESP Auth Data Encrypted Authenticated IPUpper layer PDU

Information management 25 Groep T Leuven – Information department 25/26 ESP with AH Transport Mode IPESP Auth Encrypted Authenticated with AH IP AH Upper layer PDU Authenticated with ESP

Information management 26 Groep T Leuven – Information department 26/26 ESP Tunnel Mode IP (new)ESP Auth Data IP Encrypted Authenticated IPUpper layer PDU