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Ip security in i psec

1) IPsec provides data confidentiality, integrity, and authentication for IPv4 and IPv6 networks through protocols like AH and ESP. 2) It uses security associations to define encryption and authentication parameters for secure communication between hosts or subnets. 3) The Internet Key Exchange (IKE) protocol negotiates security associations and authenticates peers to securely establish IPsec tunnels.

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IP security IPsec Ahmed Serhrouchni ENST’Paris CNRS
Plan • Présentation • Services • Architecture • Protocole AH • Protocole ESP • L’association de sécurité • Les politiques de sécurité • Protocole IKE • Conclusions
Présentation: motivations de IPSec • IPSec (IP Security) est intégré dans IPv6 • Motivations de IPv6 – Le protocole est définie pour répondre aux besoins de la future génération de l’Internet – Caractéristiques • Grande capacité d’adressage (128 bytes) avec un apport important pour alléger les tables de routage • Sécurisation des communications (IPSec) • Capacité de mise en œuvre de la qualité de service QoS • Protocole et architecture pour la mobilité • 6bone un réseau mondial d’expérimentation de IPv6 • Stratégie de migration sont en cours de développement
Présentation: standardisation de IPSec • IPSec = IP security Protocol – Standard développé à l’IETF – Premier RFC en 1995 sans gestion de clés – Deuxième version en Novembre 1998 avec la gestion des clés (IKE) – Partie commune entre IPv4 et IPv6 (obligatoire en IPv6) • Implémentation de IPSec – Implémentation Native (dans la pile IP avec IPSec en native) – BITS (Bump in the Stack) : logiciel additionnel – BITW (Bump in the Wire) : processeur cryptographique externe
Présentation: bénéfice de IPSec • IPSec – Couche réseau pour le chiffrement et l’authentification – Standards ouvert pour offrir des communications privés et sécurisés – Solution flexible pour déployer des politiques de sécurité à grande échelle • Status de IPSec – Plusieurs RFCs bien définis – Plusieurs implémentations (Nortel, Redcreek, Sun Solaris, Microsoft, DEC, Cisco, HP, Telebit, 6Wind, Freeswan, etc.) – Plusieurs tests de conformance et d’interopérabilité basés sur des implantations de référence • Caractéristiques de IPSec – Standard pour la confidentialité, l’intégrité, et l’authentification pour les échanges sur le réseau Internet – Transparent aux infrastructures du réseau – Solution de sécurité de bout en bout incluant routeurs, firewalls, PCs et serveurs
Services de sécurité fournis par IPsec • Confidentialité des données • Integrité des données • Authentification de l’origine des données • Contrôle d’accès control & contre analyse de trafic • Non rejeu
Architecture Ahmed's PC to Omar Server Encrypted Ahmed's PC Omar Server All Other Traffic Chloe’s PC Cleartext E-Mail Server • Traffic protected on a flow-by-flow basis between specific hosts or subnets • Media and interface independent • Transparent to intermediate network devices • Topology independent
Protocoles • AH: Authentication Header • ESP: EncapSuled Payload • IKE: Internet Key Exchange • ISAKMP • OAKLEY
Protocole: encapsulation Interoperable Authentication, Integrity and Encryption IP D (Enc ata r y pt ed) IPSec Header(s) AH/ESP IP He ad er
Protocole: mode Transport • Dans le cas de la confidentialité seulement les données sont chiffrées • Implémenter au dessus de IP – Special processing (like QoS, Multicast) enabled – Useful for tunneling protocol (like L2TP) IP HDR Données Mode Transport IP HDR IPSec HDR Données Peut être chiffré
Architecture: IPSec Transport Mode Internet Gateway Gateway Security Association Host Host Authenticated Unencrypted Encrypted Orig IP Header IP Header Orig ESP ESP TCP DATA ESP Trailer (any options) options) (any Authentication Authenticated Orig IP Header IP Header Orig AH TCP DATA (any options) options) (any
IPSec Tunnel Mode • Tunnel mode – All IP datagram are encrypted – Implementation above IP – ESP tunnel mode : • can provide more security • less complexity and cost – Ideal for VPN IP HDR Data Tunnel Mode New IP HDR IPSec HDR IP HDR Data May Be Encrypted
Architecture: IPSec Tunnel Mode Internet Security Gateway Security Gateway Security Association Host Host Authenticated Unencrypted Encrypted New IP Header Orig IP Header ESP ESP Paylaod ESP Trailer (any options) (any options) Authentication Authenticated New IP Header Orig IP Header AH Paylaod (any options) (any options)
Authentication Header (AH) • Data integrity • Data origin authentication • Anti-replay protection • Protects the IP header • No confidentiality
Protocol AH (Authentication Header) • Provides: – Origin Authentication, Integrity, Anti-replay protection, does not provide encryption Authenticated IPv4 Header AH Upper Protocol (i.e. TCP, UDP, ICMP) Data Next Header Length Reserved Security Parameters Index Sequence Number Field Authentication Data (variable length) Contains Integrity Check Value (ICV) 32 bits
Protocol ESP: (Encapsulating Security Payload) • Data confidentiality • Limited traffic flow confidentiality • Data integrity • Data origin authentication • Anti-replay protection • Does not protect IP Header
Protocol ESP (Encapsulating Security Payload) • Provides: – Confidentiality (Encryption), Origin Authentication, Integrity, Anti- replay protection Authenticated Encrypted Unencrypted Orig IP Header ESP ESP ESP Payload (any options) Trailer Authentication Security Parameters Index Sequence Number Field 32 bits Variable length (depending on encryption transform used)
Security Association (SA) • Defines a secure and unidirectional relationship • Data structure containing the security parameters : – SPI (Security Parameter Index) – SNF (Sequence Number Field) used to avoid anti-replay – Anti-replay sequence number receive window – Authentication parameters (algorithms, keys, initialization vector) – Encryption parameters (algorithms, keys, length, initialization vector) – Key lifetime – SA lifetime – Protocol mode – PMTU • For a typical bi-directional communication, two SAs (one in each direction) are needed)
Mechanisms: IPSec Security Associations • A relationship between two or more entities that describes how the entities will use security services to communicate securely • Simplex "connection" that affords security services to the traffic carried by it • Bi-directional traffic requires one SA in each direction • Security services provided by either AH or ESP • If both AH and ESP required two SAs are formed • Uniquely identified by • a SPI (Security Parameter Index) • IP destination address • Security Protocol Identifier (AH or ESP) Security Gateway Security Gateway Security Association Host Internet Host
Security Association (SA) • Agreement between two entities on a security policy, including: – Encryption algorithm – Authentication algorithm – Shared session keys – SA lifetime • Unidirectional – Two-way communication consists of two Sas • Key management – Manual mode – Automatic mode (via IKE)
Combining Security Associations Transport SA (A& B) Mode SA (R1&R2) Tunnel Aicha Brahim Mode R1 R2 Internet IP inner header AH/ESP header Data IP outer header AH/ESP header IP inner header AH/ESP header Data IP inner header AH/ESP header Data
Security Policy Database (SPD) • The SPD is the recipient for the system administrator’s specification, of the security policies to be applied to outbound and inbound traffic • The nominal form of the SPD includes for each entry : – The selectors that defines the traffic to which the policy should be applied – The security policy to be applied to the packet matching the associated selectors • Per interface, inbound and outbound SPDs
Security Association Database (SAD) • The SAD contains the list of all inbound and outbound established SAs • Each entry in the SAD defines the parameters associated with one SA. The entry is characterized by a set of values given to the field selectors. This defines the traffic flows to which the SA should be applied. • For outbound processing, SAD entries are pointed to by entries in the SPD • For inbound processing, each SAD entry is indexed by : – Outer header’s destination IP address – IPSec protocol (AH or ESP) in the IP header (Protocol or Next Header fields) – SPI (Security Parameters Index) in the AH/ESP header : a 32-bit value used to distinguish among different SAs terminating at the same destination and using the same IPSec protocol
Mechanisms : Principle Administrator Applications DOI Oakley (ftp, http,…) IKE ISAKMP SPD TCP/UDP IP / IPSec (AH, ESP) SAD NAP
Internet Key Exchange (IKE) • IKE protocol – Negotiates policy to protect communication – Authenticated Diffie-Hellman key exchange – Negotiates (possibly multiple) security associations for IPSec – Hybrid of three earlier protocols • ISAKMP (payload, syntax and encoding) • OAKLEY (based on Diffie-Hellman) – Objective : offer a secure and automated IPSec SA negotiation – Two phase • Establishment of a secure channel between the two peers – Called ISAKMP Security Association – Negotiation of the ISAKMP parameters ( Authentication method, Algorithms used for encryption and authentication) – Key exchange • Ipsec negotiation inside the ISAKMP secure channel – Negotiation of the IPSec parameters : security protocols, algorithms and keys used for data authentication and encryption
Initiating new connections IKE IPSec Data • Establish IKE SA—“Main mode/Phase 1” • Establish IPSec SA—“Quick mode/Phase 2” • Send protected data
How IPSec Uses IKE 1. Outbound packet from 4. Packet is sent from Astrid to Astrid to Barnabe. No IPSec SA Barnabe protected by IPSec SA IPSec IPSec Barnabe’s Astrid’s router router IKE IKE Tunnel IKE 2. Astrid’s IKE begins 3. Negotiation complete. negotiation with Barnabe’s Astrid and Barnabe now have complete set of SAs in place
Creating IPSec SA—Quick Mode IKE SA DES DES DES MD5 SHA MD5 DH1 DH1 DH1 YA YB Data • Requires IKE SA to be in place • Negotiate IPSec parameters • Create shared session key Local Policy { Exchange DH numbers for PFS or Exchange nonces for quick rekey
Conclusions • IPSec is a whole system which can answer needs of security and could be adapted in a lot of situations • The implementation of IPSec in IPv6 and his efficient adaptation in IPv4 assures IPSec to become one of the major security solutions of the Internet and Intranet in the future • but some improvements have to be done … – Treatment packet by packet – Interoperability • NAT • Dynamic allocation address • Multicast • all IPSec implementations 29