ISAKMP RFC 2408 Internet Security Association & Key Management Protocol Protocol Establish, modify, and delete SAs Negotiate crypto keys Procedures Authentication of peers Threat mitigation

ISAKMP Defines procedures and packet formats to deal with SAs and keys Provides a framework for secure communication on the Internet Does not specify algorithms, formats, or protocols ISAKMP is a framework in which a specific secure communication definition can be implemented

ISAKMP Security Associations Authentication Public Key Cryptography Protection DoS – Anti-Clogging Hijacking a connection Man in the middle attacks

ISAKMP Terminology DOI – Domain Of Interpretation: defines payload formats, exchange types, naming conventions

IISAKMP – Phases Phase 1: Two entities agree on how to protect further negotiation traffic. They negotiate an ISAKMP SA for an authenticated and secure channel Phase 2:The phase 1 secure channel is used to negotiate security services for IPSec.

ISAKMP Header Initiator Cookie Responder Cookie Major Version Minor Next Payload Exchange Type Flags Message ID Length

Header Fields Initiator Cookie (8 octets) – Cookie of entity that initiated SA establishment, notification or deletion. Responder Cookie (8 octets) – Cookie of the responder Next Payload (1 octet) – Type of first payload Major/Minor Version (4 bits each) – Version of ISAKMP in use Exchange Type (1 octet) – Type of exchange being used Flags (1 octet) – More stinking flags, encrypt, commit authentication only Message ID (4 octets) – Unique ID to identify things in Phase 2 Length (4 octets) – Length of total message (headers + payloads)

Next Payload Types Next Payload Type Value Next Payload Type Value NONE 0 SA 1 Proposal 2 Transform 3 Key Exchange 4 Identification 5 Certificate 6 Cert Request 7 Next Payload Type Value Hash 8 Signature 9 Nonce 10 Notification 11 Delete 12 Vendor ID 13 Reserved 14 – 127 Private Use 128 - 255

Exchange Types Exchange Type Value Exchange Type Value NONE 0 Base 1 Id Protection 2 Auth Only 3 Aggressive 4 Informational 5 Exchange Type Value ISAKMP Future Use 6 - 31 DOI Specific Use 32 – 127 Private Use 128 - 255

Generic Payload Header Next Payload Reserved Payload Length Payload Data

Domain of Interpretation (DOI) SA Payload Next Payload Reserved Payload Length Domain of Interpretation (DOI) ~ Situation DOI (4 octets) – Identifies the DOI under which this negotiation is taking place. A value of 0 (zero) during Phase 1 specifies a Generic ISAKMP SA which can be used for any protocol during Phase 2. Situation - A DOI-specific field that identifies the situation under which this negotiation is taking place.

Proposal Payload Next Payload Reserved Payload Length Proposal No. Proposal ID SPI Size No. of Transforms SPI (variable)

Proposal Payload Payload Length (2 octets) – Length is octets of the entire Proposal payload including the generic payload header, the Proposal payload, and all Transform payloads associated with this proposal. Proposal No. - Identifies the Proposal number for the current payload. Proposal ID – Specifies the protocol identifier such as IPSEC ESP, IPSEC AH, OSPF, TLS, etc. SPI Size – Length in octets of the SPI as defined by the Protocol ID. No. of Transforms – Specifies the number of transforms for the proposal. SPI (variable) – The sending entity's SPI.

Transform Payload ~ Next Payload Reserved Payload Length Transform No. Transform ID Reserved2 ~ SA Attributes

Transform Payload Payload Length (2 octets) – Length is octets of the current payload, including the generic payload header, Transform values, and all SA attributes Transform No. - Identifies the Transform number for the current payload. Transform ID – Specifies the Transform identifier fmor the protocol within the current proposal. Reserved 2 (2 octets) – Set to zero. SA Attributes (Variable length) – SA attributes should be represented using the Data Attributes format.

Key Exchange Payload ~ Reserved Payload Length Next Payload Key Exchange Data Key Exchange Data (variable length) – Data required to generate a session key. This data is specified by the DOI and the associated Key Exchange algorithm.

Certificate Payload ~ Reserved Payload Length Next Payload Cert Encoding Key Exchange Data ~ Cert Encoding (1 octet) – Indicates the type of certificate contained in the Certificate field.

Certificate Types Certificate Type Value Certificate Type Value NONE 0 PKCS #7 1 PGP Certificate 2 DNS Signed Key 3 X.509 Cert - Signature 4 X.509 Cert – Key Exchange 5 Certificate Type Value Kerberos Token 6 Cert Revoc List 7 Authority Revoc List 8 SPKI Cert. 9 X.509 Cert – Attribute 10 Reserved 11 - 255

Other Payloads ~ ~ ~ Reserved Payload Length Next Payload Hash Data Signature Data Next Payload Reserved Payload Length ~ Nonce Data

Notification Payload ~ ~ Next Payload Reserved Payload Length DOI Protocol ID SPI Size Notify Message Type ~ SPI ~ Notification Data

Notify Messages Errors Value INVALID-PAYLOAD-TYPE 1 DOI-NOT-SUPPORTED 2 SITUATION-NOT-SUPPORTED 3 INVALID-COOKIE 4 INVALID-MAJOR-VERSION 5 INVALID-MINOR-VERSION 6 INVALID-EXCHANGE-TYPE 7 INVALID-FLAGS 8 INVALID-MESSAGE-ID 9 INVALID-PROTOCOL-ID 10 INVALID-SPI 11 INVALID-TRANSFORM-ID 12 ATTRIBUTES-NOT-SUPPORTED 13 NO-PROPOSAL-CHOSEN 14 BAD-PROPOSAL-SYNTAX 15 Errors Value PAYLOAD-MALFORMED 16 INVALID-KEY-INFORMATION 17 INVALID-ID-INFORMATION 18 INVALID-CERT-ENCODING 19 INVALID-CERTIFICATE 20 CERT-TYPE-UNSUPPORTED 21 INVALID-CERT-AUTHORITY 22 INVALID-HASH-INFORMATION 23 AUTHENTICATION-FAILED 24 INVALID-SIGNATURE 25 ADDRESS-NOTIFICATION 26 NOTIFY-SA-LIFETIME 27 CERTIFICATE-UNAVAILABLE 28 UNSUPPORTED-EXCHANGE-TYPE 29 UNEQUAL-PAYLOAD-LENGTHS 30 RESERVED (Future Use) 31 - 8191 Private Use 8192 – 16383

ISAKMP Message Construction Initiator Cookie Responder Cookie Major Version Minor Version NP = KE Exchange Type Flags Message ID Total Message Length NP = Nonce Reserved KE Payload Length Key Exchange Data NP = 0 Reserved Nonce Payload Length Nonce Data

Proposal Syntax Proposal # Proposals with the same Proposal Transform # Proposals with the same Proposal number are taken as a logical AND. Proposals with different numbers are taken as a logical OR. Different Transform within a proposal are taken as a logical OR.

Proposal Example Proposal 1: AH Transform 1: HMAC-SHA Transform 2: HMAC-MD5 Proposal 2: ESP Transform 1: 3DES with HMAC-SHA Transform 2: 3DES with HMAC-MD5 Transform 3: AES with HMAC-SHA-256 Proposal 3: ESP Proposal 4: PCP Transform 1: LZS

Exchange Types Exchange Type Value Exchange Type Value NONE 0 Base 1 Id Protection 2 Auth Only 3 Aggressive 4 Informational 5 Exchange Type Value ISAKMP Future Use 6 - 31 DOI Specific Use 32 – 127 Private Use 128 - 255

Base Exchange Initiator Direction Responder Note Header, SA, Nonce => Begin ISAKMP-SA negotiation <= HDR, SA, Nonce Basic SA agreed upon Header, KE, Idii, Auth => Key generated by responder Initiator Ident verified <= HDR, KE, Idir, Auth Responder Ident verified Initiator key generated, SA est.