IPSec. What is IPSec? Concepts and Terms Architecture Operation Application Example. Some graphics originate (in part) from cisco

Transcription

1 IPSec What is IPSec? Concepts and Terms Architecture Operation Application Example Some graphics originate (in part) from cisco

2 What is IPSec? A security architecture Two IP security protocols Authentication Header (AH) Encapsulation Security Payload (ESP) Internet Key Exchange (IKE) Exchange of IPSec security seeds An open standard (RFC 2401) A security solution on the IP layer

3 Concepts of IPSec internet intranet Protects data transfers throughout the Internet, procuring Authentication, Integrity, Encryption Transparent to network infrastructure End-to-end security concept

4 Tunnel and Transport Mode Tunnel Mode Tunnel Mode Tunnel Mode Joe s PC HR Server Transport Mode (with ALG) Transport Mode Transport Mode End-to-End or via ALG Tunnel Mode for all connection types

5 Security Association (SA) Router A Insecure Channel Router B Directional description of security services in use (unidirectional per connection) Valid for individual data flow Two-way communication uses two SAs Each SA identified by a Security Parameter Index (SPI) - as part of the IPSec Headers - number with strictly local scope

6 Security Association (2) Destination Address Security Parameter Index (SPI) IPSec Transform A390BC1 AH, HMAC-MD5 MD5 Key Additional SA Attributes (e.g. lifetime) 7572CA49F One Day or 100MB

7 IPSec Authentication Header (AH) IP HDR Data Transport Mode IP HDR AH Data Authenticates all but variable fields Tunnel Mode New IP HDR AH IP HDR Data Authenticates all but variable fields of the new IP-Header

8 Authentication Header (2) Authentication header placed prior to TCP/UDP (IPv4) header (change of IPv4-Stack) or as extension Header (IPv6). Authenticates data source and integrity by a Message Authentication Code (MAC). Next Header Payload Length RESERVED Security Parameter Index (SPI) Sequence Number Field Authentication Data Remains unencrypted.

9 Encapsulating Security Payload (ESP) IP HDR Data Transport Mode IP HDR ESP HDR Data Encrypted Authenticated ESP Trailer ESP Auth Tunnel Mode ESP HDR IP HDR Data Encrypted Authenticated ESP Trailer ESP Auth

10 Encapsulating Security Payload ESP Header precedes IP packet (or upper protocol). ESP Header remains unencrypted, but authenticated with data. Encrypted IP packet becomes ESP payload Trailer for terminating 0s and alignment. Security Parameter Index (SPI) Sequence Number Field Initialization Vector Payload Data Padding (If Any) Pad Length Authentication Data Next Header

11 Encryption Methods IPSec can employ different encryption methods. To initiate a Security Association either a Public Key Infrastructure (PKI) or Preshared Secrets (offline) are needed. While an SA is running, data will be encrypted via symmetric encryption methods (performance). To regularly exchange keys an Internet Key Exchange Daemon is part of the IPSec concept.

12 Internet Key Exchange (IKE) IKE-Protocol (RFC 2409) implements Oakley and SKEME key exchange in ISAKMP Framework. Negotiates policies to use. Modi: Main, Aggressive, Quick and New Group. Authenticated Diffie-Hellman key exchange. Negotiates SAs to initiate IPSec.

13 Encryption Technologies supported by IPSec Encryption Authentication Integrity - Hash Functions Secret Key: DES, 3DES Public Key: RSA MAC SHA MD5 Key Management HMAC Digital Signature Manual Operation Secret Key Exchange: Diffie-Hellman Public Key Exchange: Certificate Authority

14 Operation of IPSec Notable Traffic? IKE Negociation IPSec Negociation Tunnel Construction IKE IPSec Data

15 IKE Initiation of a SA SA Request IPSec (triggered by ACL) Fred Wilma IKE SA Offer - des, sha, rsa sig, D-H group 1, lifetime Policy Match accept offer In the Clear ISAKMP Phase 1 Oakley Main Mode Fred D-H exchange : KE, nonce Wilma D-H exchange : KE, nonce Fred Authenticate D-H apply Hash Wilma Authenticate D-H apply Hash Protected IKE Bi-directional SA Established

16 IPSec Constructing the SA Fred Wilma IPSec SA Offer - transform, mode, pfs, authentication, lifetime ISAKMP Phase 2 Oakley Quick Mode Policy Match accept offer Fred D-H exchange or refresh IKE key Wilma D-H exchange or refresh IKE key Protected by the IKE SA IPSec Outbound SA Established IPSec Inbound SA Established

17 Tunnels of Tunnels

18 Application Example: Secure WLAN Access IPsec Authentifizieren Registrieren

19 Components IPsec: Tunnel mode with ESP, Aggressive Mode Tunnel routers: PCs, FreeBSD 4.x / Kame IKE-Daemon Racoon (patched) Wrapper Script to stir packet filtering ISC DHCPD 3.x (patched), OpenLDAP 2.x Web-Administration tool Clients: SSH Sentinell (MS), PGP (MAC OS9), Native BSD, Linux, MAC OSX

20 Performance Load tests with many Clients producing high traffic load: Main load produced by data, not # of clients Processing load dominates A 2,4 GHz PIV can handle about 80 Mbit/s One tunnel router serves 10 Accesspoints Improvements expected by upcoming crypto processor cards