📄 rfc2407.txt
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SA Life Type 1 B SA Life Duration 2 V Group Description 3 B Encapsulation Mode 4 B Authentication Algorithm 5 B Key Length 6 B Key Rounds 7 B Compress Dictionary Size 8 B Compress Private Algorithm 9 V Class Values SA Life Type SA Duration Specifies the time-to-live for the overall security association. When the SA expires, all keys negotiated under the association (AH or ESP) must be renegotiated. The life type values are: RESERVED 0 seconds 1 kilobytes 2 Values 3-61439 are reserved to IANA. Values 61440-65535 are for private use. For a given Life Type, the value of the Life Duration attribute defines the actual length of the component lifetime -- either a number of seconds, or a number of Kbytes that can be protected. If unspecified, the default value shall be assumed to be 28800 seconds (8 hours). An SA Life Duration attribute MUST always follow an SA Life Type which describes the units of duration. See Section 4.5.4 for additional information relating to lifetime notification. Group Description Specifies the Oakley Group to be used in a PFS QM negotiation. For a list of supported values, see Appendix A of [IKE].Piper Standards Track [Page 13]RFC 2407 IP Security Domain of Interpretation November 1998 Encapsulation Mode RESERVED 0 Tunnel 1 Transport 2 Values 3-61439 are reserved to IANA. Values 61440-65535 are for private use. If unspecified, the default value shall be assumed to be unspecified (host-dependent). Authentication Algorithm RESERVED 0 HMAC-MD5 1 HMAC-SHA 2 DES-MAC 3 KPDK 4 Values 5-61439 are reserved to IANA. Values 61440-65535 are for private use. There is no default value for Auth Algorithm, as it must be specified to correctly identify the applicable AH or ESP transform, except in the following case. When negotiating ESP without authentication, the Auth Algorithm attribute MUST NOT be included in the proposal. When negotiating ESP without confidentiality, the Auth Algorithm attribute MUST be included in the proposal and the ESP transform ID must be ESP_NULL. Key Length RESERVED 0 There is no default value for Key Length, as it must be specified for transforms using ciphers with variable key lengths. For fixed length ciphers, the Key Length attribute MUST NOT be sent. Key Rounds RESERVED 0 There is no default value for Key Rounds, as it must be specified for transforms using ciphers with varying numbers of rounds.Piper Standards Track [Page 14]RFC 2407 IP Security Domain of Interpretation November 1998 Compression Dictionary Size RESERVED 0 Specifies the log2 maximum size of the dictionary. There is no default value for dictionary size. Compression Private Algorithm Specifies a private vendor compression algorithm. The first three (3) octets must be an IEEE assigned company_id (OUI). The next octet may be a vendor specific compression subtype, followed by zero or more octets of vendor data.4.5.1 Required Attribute Support To ensure basic interoperability, all implementations MUST be prepared to negotiate all of the following attributes. SA Life Type SA Duration Auth Algorithm4.5.2 Attribute Parsing Requirement (Lifetime) To allow for flexible semantics, the IPSEC DOI requires that a conforming ISAKMP implementation MUST correctly parse an attribute list that contains multiple instances of the same attribute class, so long as the different attribute entries do not conflict with one another. Currently, the only attributes which requires this treatment are Life Type and Duration. To see why this is important, the following example shows the binary encoding of a four entry attribute list that specifies an SA Lifetime of either 100MB or 24 hours. (See Section 3.3 of [ISAKMP] for a complete description of the attribute encoding format.) Attribute #1: 0x80010001 (AF = 1, type = SA Life Type, value = seconds) Attribute #2: 0x00020004 (AF = 0, type = SA Duration, length = 4 bytes) 0x00015180 (value = 0x15180 = 86400 seconds = 24 hours) Attribute #3: 0x80010002 (AF = 1, type = SA Life Type, value = KB)Piper Standards Track [Page 15]RFC 2407 IP Security Domain of Interpretation November 1998 Attribute #4: 0x00020004 (AF = 0, type = SA Duration, length = 4 bytes) 0x000186A0 (value = 0x186A0 = 100000KB = 100MB) If conflicting attributes are detected, an ATTRIBUTES-NOT-SUPPORTED Notification Payload SHOULD be returned and the security association setup MUST be aborted.4.5.3 Attribute Negotiation If an implementation receives a defined IPSEC DOI attribute (or attribute value) which it does not support, an ATTRIBUTES-NOT-SUPPORT SHOULD be sent and the security association setup MUST be aborted, unless the attribute value is in the reserved range. If an implementation receives an attribute value in the reserved range, an implementation MAY chose to continue based on local policy.4.5.4 Lifetime Notification When an initiator offers an SA lifetime greater than what the responder desires based on their local policy, the responder has three choices: 1) fail the negotiation entirely; 2) complete the negotiation but use a shorter lifetime than what was offered; 3) complete the negotiation and send an advisory notification to the initiator indicating the responder's true lifetime. The choice of what the responder actually does is implementation specific and/or based on local policy. To ensure interoperability in the latter case, the IPSEC DOI requires the following only when the responder wishes to notify the initiator: if the initiator offers an SA lifetime longer than the responder is willing to accept, the responder SHOULD include an ISAKMP Notification Payload in the exchange that includes the responder's IPSEC SA payload. Section 4.6.3.1 defines the payload layout for the RESPONDER-LIFETIME Notification Message type which MUST be used for this purpose.4.6 IPSEC Payload Content The following sections describe those ISAKMP payloads whose data representations are dependent on the applicable DOI.4.6.1 Security Association Payload The following diagram illustrates the content of the Security Association Payload for the IPSEC DOI. See Section 4.2 for a description of the Situation bitmap.Piper Standards Track [Page 16]RFC 2407 IP Security Domain of Interpretation November 1998 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Next Payload ! RESERVED ! Payload Length ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Domain of Interpretation (IPSEC) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Situation (bitmap) ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Labeled Domain Identifier ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Secrecy Length (in octets) ! RESERVED ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Secrecy Level ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Secrecy Cat. Length (in bits) ! RESERVED ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Secrecy Category Bitmap ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Integrity Length (in octets) ! RESERVED ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Integrity Level ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ! Integ. Cat. Length (in bits) ! RESERVED ! +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Integrity Category Bitmap ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: Security Association Payload Format The Security Association Payload is defined as follows: o Next Payload (1 octet) - Identifier for the payload type of the next payload in the message. If the current payload is the last in the message, this field will be zero (0). o RESERVED (1 octet) - Unused, must be zero (0). o Payload Length (2 octets) - Length, in octets, of the current payload, including the generic header. o Domain of Interpretation (4 octets) - Specifies the IPSEC DOI, which has been assigned the value one (1). o Situation (4 octets) - Bitmask used to interpret the remainder of the Security Association Payload. See Section 4.2 for a complete list of values.Piper Standards Track [Page 17]RFC 2407 IP Security Domain of Interpretation November 1998 o Labeled Domain Identifier (4 octets) - IANA Assigned Number used to interpret the Secrecy and Integrity information. o Secrecy Length (2 octets) - Specifies the length, in octets, of the secrecy level identifier, excluding pad bits. o RESERVED (2 octets) - Unused, must be zero (0). o Secrecy Level (variable length) - Specifies the mandatory secrecy level required. The secrecy level MUST be padded with zero (0) to align on the next 32-bit boundary. o Secrecy Category Length (2 octets) - Specifies the length, in bits, of the secrecy category (compartment) bitmap, excluding pad bits. o RESERVED (2 octets) - Unused, must be zero (0). o Secrecy Category Bitmap (variable length) - A bitmap used to designate secrecy categories (compartments) that are required. The bitmap MUST be padded with zero (0) to align on the next 32-bit boundary. o Integrity Length (2 octets) - Specifies the length, in octets, of the integrity level identifier, excluding pad bits. o RESERVED (2 octets) - Unused, must be zero (0). o Integrity Level (variable length) - Specifies the mandatory integrity level required. The integrity level MUST be padded with zero (0) to align on the next 32-bit boundary. o Integrity Category Length (2 octets) - Specifies the length, in bits, of the integrity category (compartment) bitmap, excluding pad bits. o RESERVED (2 octets) - Unused, must be zero (0). o Integrity Category Bitmap (variable length) - A bitmap used to designate integrity categories (compartments) that are required. The bitmap MUST be padded with zero (0) to align on the next 32-bit boundary.4.6.1.1 IPSEC Labeled Domain Identifiers The following table lists the assigned values for the Labeled Domain Identifier field contained in the Situation field of the Security Association Payload.Piper Standards Track [Page 18]RFC 2407 IP Security Domain of Interpretation November 1998 Domain Value ------- ----- RESERVED 04.6.2 Identification Payload Content The Identification Payload is used to identify the initiator of the Security Association. The identity of the initiator SHOULD be used by the responder to determine the correct host system security policy
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