proposal
Kernel->Registered: SADB_ACQUIRE of OSPF, <same as sent message>
The KMd sees this and performs actions similar to the previous
example. One difference, however, is that when the UPDATE message
comes back, the OSPFd will then perform a GET of the updated SA to
retrieve all of its parameters.
5.4 Miscellaneous
Some messages work well only in system maintenance programs, for
debugging, or for auditing. In a system panic situation, such as a
detected compromise, an SADB_FLUSH message should be issued for a
particular SA type, or for ALL SA types.
Program->Kernel: SADB_FLUSH for ALL
<Kernel then flushes all internal SAs>
Kernel->All: SADB_FLUSH for ALL
Some SAs may need to be explicitly deleted, either by a KMd, or by a
system maintenance program.
Program->Kernel: SADB_DELETE for AH, association, addrs
Kernel->All: SADB_DELETE for AH, association, addrs
Common usage of the SADB_DUMP message is discouraged. For debugging
purposes, however, it can be quite useful. The output of a DUMP
message should be read quickly, in order to avoid socket buffer
overflows.
Program->Kernel: SADB_DUMP for ESP
Kernel->Program: SADB_DUMP for ESP, association, <all fields>
Kernel->Program: SADB_DUMP for ESP, association, <all fields>
Kernel->Program: SADB_DUMP for ESP, association, <all fields>
<ad nauseam...>
6 Security Considerations
This memo discusses a method for creating, reading, modifying, and
deleting Security Associations from an operating system. Only
trusted, privileged users and processes should be able to perform any
of these operations. It is unclear whether this mechanism provides
any security when used with operating systems not having the concept
of a trusted, privileged user.
If an unprivileged user is able to perform any of these operations,
then the operating system cannot actually provide the related
security services. If an adversary knows the keys and algorithms in
use, then cryptography cannot provide any form of protection.
This mechanism is not a panacea, but it does provide an important
operating system component that can be useful in creating a secure
internetwork.
Users need to understand that the quality of the security provided by
an implementation of this specification depends completely upon the
overall security of the operating system, the correctness of the
PF_KEY implementation, and upon the security and correctness of the
applications that connect to PF_KEY. It is appropriate to use high
assurance development techniques when implementing PF_KEY and the
related security association components of the operating system.
Acknowledgments
The authors of this document are listed primarily in alphabetical
order. Randall Atkinson and Ron Lee provided useful feedback on
earlier versions of this document.
At one time or other, all of the authors worked at the Center for
High Assurance Computer Systems at the U.S. Naval Research
Laboratory. This work was sponsored by the Information Security
Program Office (PMW-161), U.S. Space and Naval Warfare Systems
Command (SPAWAR) and the Computing Systems Technology Office, Defense
Advanced Research Projects Agency (DARPA/CSTO). We really appreciate
their sponsorship of our efforts and their continued support of
PF_KEY development. Without that support, PF_KEY would not exist.
The "CONFORMANCE and COMPLIANCE" wording was taken from [MSST98].
Finally, the authors would like to thank those who sent in comments
and questions on the various iterations of this document. This
specification and implementations of it are discussed on the PF_KEY
mailing list. If you would like to be added to this list, send a note
to <pf_key-request@inner.net>.
References
[AMPMC96] Randall J. Atkinson, Daniel L. McDonald, Bao G. Phan, Craig
W. Metz, and Kenneth C. Chin, "Implementation of IPv6 in 4.4-Lite
BSD", Proceedings of the 1996 USENIX Conference, San Diego, CA,
January 1996, USENIX Association.
[Atk95a] Atkinson, R., "IP Security Architecture", RFC1825, August
1995.
[Atk95b] Atkinson, R., "IP Authentication Header", RFC1826, August
1995.
[Atk95c] Atkinson, R., "IP Encapsulating Security Payload", RFC1827,
August 1995.
[Atk97] Atkinson, R., "Key Exchange Delegation Record for the Domain
Name System", RFC2230, October 1997.
[BA97] Baker, F., and R. Atkinson, "RIP-2 MD5 Authentication", RFC
2082, January 1997.
[Biba77] K. J. Biba, "Integrity Considerations for Secure Computer
Systems", MTR-3153, The MITRE Corporation, June 1975; ESD-TR-76-372,
April 1977.
[BL74] D. Elliot Bell and Leonard J. LaPadula, "Secure Computer
Systems: Unified Exposition and Multics Interpretation", MTR 2997,
The MITRE Corporation, April 1974. (AD/A 020 445)
[Bra97] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC2119, March 1997.
[CW87] D. D. Clark and D. R. Wilson, "A Comparison of Commercial and
Military Computer Security Policies", Proceedings of the 1987
Symposium on Security and Privacy, pp. 184-195, IEEE Computer
Society, Washington, D.C., 1987.
[DIA] US Defense Intelligence Agency (DIA), "Compartmented Mode
Workstation Specification", Technical Report DDS-2600-6243-87.
[GK98] Glenn, R., and S. Kent, "The NULL Encryption Algorithm and Its
Use with IPsec", Work in Progress.
[HM97a] Harney, H., and C. Muckenhirn, "Group Key Management Protocol
(GKMP) Specification", RFC2093, July 1997.
[HM97b] Harney, H., and C. Muckenhirn, "Group Key Management Protocol
(GKMP) Architecture", RFC2094, July 1997.
[MD98] Madsen, C., and N. Doraswamy, "The ESP DES-CBC Cipher
Algorithm With Explicit IV", Work in Progress.
[MG98a] Madsen, C., and R. Glenn, "The Use of HMAC-MD5-96 within ESP
and AH", Work in Progress.
[MG98b] Madsen, C., and R. Glenn, "The Use of HMAC-SHA-1-96 within
ESP and AH", Work in Progress.
[MSST98] Maughan, D., Schertler, M., Schneider, M., and J. Turner,
"Internet Security Association and Key Management Protocol (ISAKMP)",
Work in Progress.
[Moy98] Moy, J., "OSPF Version 2", STD 54, RFC2328, April 1998.
[Per97] Perkins, C., "IP Mobility Support", RFC2002, October 1996.
[Pip98] Piper, D., "The Internet IP Security Domain of Interpretation
for ISAKMP", Work in Progress.
[Sch96] Bruce Schneier, Applied Cryptography, p. 360, John Wiley &
Sons, Inc., 1996.
[Skl91] Keith Sklower, "A Tree-based Packet Routing Table for
Berkeley UNIX", Proceedings of the Winter 1991 USENIX Conference,
Dallas, TX, USENIX Association. 1991. pp. 93-103.
Disclaimer
The views and specification here are those of the editors and are not
necessarily those of their employers. The employers have not passed
judgment on the merits, if any, of this work. The editors and their
employers specifically disclaim responsibility for any problems
arising from correct or incorrect implementation or use of this
specification.
Authors' Addresses
Daniel L. McDonald
Sun Microsystems, Inc.
901 San Antonio Road, MS UMPK17-202
Palo Alto, CA 94303
Phone: +1 650 786 6815
EMail: danmcd@eng.sun.com
Craig Metz
(for Code 5544)
U.S. Naval Research Laboratory
4555 Overlook Ave. SW
Washington, DC 20375
Phone: (DSN) 754-8590
EMail: cmetz@inner.net
Bao G. Phan
U. S. Naval Research Laboratory
EMail: phan@itd.nrl.navy.mil
Appendix A: Promiscuous Send/Receive Message Type
A kernel supporting PF_KEY MAY implement the following extension for
development and debugging purposes. If it does, it MUST implement the
extension as specified here. An implementation MAY require an
application to have additional privileges to perform promiscuous send
and/or receive operations.
The SADB_X_PROMISC message allows an application to send and receive
messages in a "promiscuous mode." There are two forms of this
message: control and data. The control form consists of only a
message header. This message is used to toggle the promiscuous-
receive function. A value of one in the sadb_msg_satype field enables
promiscuous message reception for this socket, while a value of zero
in that field disables it.
The second form of this message is the data form. This is used to
send or receive messages in their raw form. Messages in the data form
consist of a message header followed by an entire new message. There
will be two message headers in a row: one for the SADB_X_PROMISC
message, and one for the payload message.
Data messages sent from the application are sent to either the PF_KEY
socket of a single process identified by a nonzero sadb_msg_seq or to
all PF_KEY sockets if sadb_msg_seq is zero. These messages are sent
without any processing of their contents by the PF_KEY interface
(including sanity checking). This promiscuous-send capability allows
an application to send messages as if it were the kernel. This also
allows it to send erroneous messages.
If the promiscuous-receive function has been enabled, a copy of any
message sent via PF_KEY by another application or by the kernel is
sent to the promiscuous application. This is done before any
processing of the message's contents by the PF_KEY interface (again,
including sanity checking). This promiscuous-receive capability
allows an application to receive all messages sent by other parties
using PF_KEY.
The messaging behavior of the SADB_X_PROMISC message is:
Send a control-form SADB_X_PROMISC message from a user process
to the kernel.
<base>
The kernel returns the SADB_X_PROMISC message to all listening
processes.
<base>
Send a data-form SADB_X_PROMISC message from a user process to
the kernel.
<base, base(, others)>
The kernel sends the encapsulated message to the target
process(s).
<base(, others)>
If promiscuous-receive is enabled, the kernel will encapsulate
and send copies of all messages sent via the PF_KEY interface.
<base, base(, others)>
Errors:
EPERM Additional privileges are required to perform the
requested operations.
ESRCH (Data form, sending) The target process in sadb_msg_seq
does not exist or does not have an open PF_KEY Version 2
socket.
Appendix B: Passive Change Message Type
The SADB_X_PCHANGE message is a passive-side (aka. the "listener" or
"receiver") counterpart to the SADB_ACQUIRE message. It is useful
for when key management applications wish to more effectively handle
incoming key management requests for passive-side sessions that
deviate from systemwide default security services. If a passive
session requests that only certain levels of security service be
allowed, the SADB_X_PCHANGE message expresses this change to any
registered PF_KEY sockets. Unlike SADB_ACQUIRE, this message is
purely informational, and demands no other PF_KEY interaction.
The SADB_X_PCHANGE message is typically triggered by either a change
in an endpoint's requested security services, or when an endpoint
that made a special request disappears. In the former case, an
SADB_X_PCHANGE looks like an SADB_ACQUIRE, complete with an
sadb_proposal extension indicating the preferred algorithms,
lifetimes, and other attributes. When a passive session either
disappears, or reverts to a default behavior, an SADB_X_PCHANGE will
be issued with _no_ sadb_proposal extension, indicating that the
exception to systemwide default behavior has disappeared.
There are two messaging behaviors for SADB_X_PCHANGE. The first is
the kernel-originated case:
The kernel sends an SADB_X_PCHANGE message to registered
sockets.
<base, address(SD), (identity(SD),) (sensitivity,) (proposal)>
NOTE: The address(SD) extensions MUST have the port fields
filled in with the port numbers of the session
requiring keys if appropriate.
The second is for a user-level consumer of SAs.
Send an SADB_X_PCHANGE message from a user process to the
kernel.
<base, address(SD), (identity(SD),) (sensitivity,) (proposal)>
The kernel returns an SADB_X_PCHANGE message to registered
sockets.
<base, address(SD), (identity(SD),) (sensitivity,) (proposal)>
Appendix C: Key Management Private Data Extension
The Key Management Private Data extension is attached to either an
SADB_ADD or an SADB_UPDATE message. It attaches a single piece of
arbitrary data to a security association. It may be useful for key
managment applications that could use an SADB_DUMP or SADB_GET
message to obtain additional state if it needs to restart or recover
after a crash. The format of this extension is:
#define SADB_X_EXT_KMPRIVATE 17
struct sadb_x_kmprivate {
uint16_t sadb_x_kmprivate_len;
uint16_t sadb_x_kmprivate_exttype;
uint32_t sadb_x_kmprivate_reserved;
};
/* sizeof(struct sadb_x_kmprivate) == 8 */
/* followed by arbitrary data */
The data following the sadb_x_kmprivate extension can be anything.
It will be stored with the actual security association in the kernel.
Like all data, it must be padded to an eight byte boundary.
Appendix D: Sample Header File
/*
This file defines structures and symbols for the PF_KEY Version 2
key management interface. It was written at the U.S. Naval Research
Laboratory. This file is in the public domain. The authors ask that
you leave this credit intact on any copies of this file.
*/
#ifndef __PFKEY_V2_H
#define __PFKEY_V2_H 1
#define PF_KEY_V2 2
#define PFKEYV2_REVISION 199806L
#define SADB_RESERVED 0
#define SADB_GETSPI 1
#define SADB_UPDATE 2
#define SADB_ADD 3
#define SADB_DELETE 4
#define SADB_GET 5
#define SADB_ACQUIRE 6
#define SADB_REGISTER 7
#define SADB_EXPIRE 8
#define SADB_FLUSH 9
#define SADB_DUMP 10
#define SADB_X_PROMISC 11
#define SADB_X_PCHANGE 12
#define SADB_MAX 12
struct sadb_msg {
uint8_t sadb_msg_version;
uint8_t sadb_msg_type;
uint8_t sadb_msg_errno;
uint8_t sadb_msg_satype;
uint16_t sadb_msg_len;
uint16_t sadb_msg_reserved;
uint32_t sadb_msg_seq;
uint32_t sadb_msg_pid;
};
struct sadb_ext {
uint16_t sadb_ext_len;
uint16_t sadb_ext_type;
};
struct sadb_sa {
uint16_t sadb_sa_len;
uint16_t sadb_sa_exttype;
uint32_t sadb_sa_spi;
uint8_t sadb_sa_replay;
uint8_t sadb_sa_state;
uint8_t sadb_sa_auth;
uint8_t sadb_sa_encrypt;
uint32_t sadb_sa_flags;
};
struct sadb_lifetime {
uint16_t sadb_lifetime_len;
uint16_t sadb_lifetime_exttype;
uint32_t sadb_lifetime_allocations;
uint64_t sadb_lifetime_bytes;
uint64_t sadb_lifetime_addtime;
uint64_t sadb_lifetime_usetime;
};
struct sadb_address {
uint16_t sadb_address_len;
uint16_t sadb_address_exttype;
uint8_t sadb_address_proto;
uint8_t sadb_address_prefixlen;
uint16_t sadb_address_reserved;
};
struct sadb_key {
uint16_t sadb_key_len;
uint16_t sadb_key_exttype;
uint16_t sadb_key_bits;
uint16_t sadb_key_reserved;
};
struct sadb_ident {
uint16_t sadb_ident_len;
uint16_t sadb_ident_exttype;
uint16_t sadb_ident_type;
uint16_t sadb_ident_reserved;
uint64_t sadb_ident_id;
};
struct sadb_sens {
uint16_t sadb_sens_len;
uint16_t sadb_sens_exttype;
uint32_t sadb_sens_dpd;
uint8_t sadb_sens_sens_level;
uint8_t sadb_sens_sens_len;
uint8_t sadb_sens_integ_level;
uint8_t sadb_sens_integ_len;
uint32_t sadb_sens_reserved;
};
struct sadb_prop {
uint16_t sadb_prop_len;
uint16_t sadb_prop_exttype;
uint8_t sadb_prop_replay;
uint8_t sadb_prop_reserved[3];
};
struct sadb_comb {
uint8_t sadb_comb_auth;
uint8_t sadb_comb_encrypt;
uint16_t sadb_comb_flags;
uint16_t sadb_comb_auth_minbits;
uint16_t sadb_comb_auth_maxbits;
uint16_t sadb_comb_encrypt_minbits;
uint16_t sadb_comb_encrypt_maxbits;
uint32_t sadb_comb_reserved;
uint32_t sadb_comb_soft_allocations;
uint32_t sadb_comb_hard_allocations;
uint64_t sadb_comb_soft_bytes;
uint64_t sadb_comb_hard_bytes;
uint64_t sadb_comb_soft_addtime;
uint64_t sadb_comb_hard_addtime;
uint64_t sadb_comb_soft_usetime;
uint64_t sadb_comb_hard_usetime;
};
struct sadb_supported {
uint16_t sadb_supported_len;
uint16_t sadb_supported_exttype;
uint32_t sadb_supported_reserved;
};
struct sadb_alg {
uint8_t sadb_alg_id;
uint8_t sadb_alg_ivlen;
uint16_t sadb_alg_minbits;
uint16_t sadb_alg_maxbits;
uint16_t sadb_alg_reserved;
};
struct sadb_spirange {
uint16_t sadb_spirange_len;
uint16_t sadb_spirange_exttype;
uint32_t sadb_spirange_min;
uint32_t sadb_spirange_max;
uint32_t sadb_spirange_reserved;
};
struct sadb_x_kmprivate {
uint16_t sadb_x_kmprivate_len;
uint16_t sadb_x_kmprivate_exttype;
uint32_t sadb_x_kmprivate_reserved;
};
#define SADB_EXT_RESERVED 0
#define SADB_EXT_SA 1
#define SADB_EXT_LIFETIME_CURRENT 2
#define SADB_EXT_LIFETIME_HARD 3
#define SADB_EXT_LIFETIME_SOFT 4
#define SADB_EXT_ADDRESS_SRC 5
#define SADB_EXT_ADDRESS_DST 6
#define SADB_EXT_ADDRESS_PROXY 7
#define SADB_EXT_KEY_AUTH 8
#define SADB_EXT_KEY_ENCRYPT 9
#define SADB_EXT_IDENTITY_SRC 10
#define SADB_EXT_IDENTITY_DST 11
#define SADB_EXT_SENSITIVITY 12
#define SADB_EXT_PROPOSAL 13
#define SADB_EXT_SUPPORTED_AUTH 14
#define SADB_EXT_SUPPORTED_ENCRYPT 15
#define SADB_EXT_SPIRANGE 16
#define SADB_X_EXT_KMPRIVATE 17
#define SADB_EXT_MAX 17
#define SADB_SATYPE_UNSPEC 0
#define SADB_SATYPE_AH 2
#define SADB_SATYPE_ESP 3
#define SADB_SATYPE_RSVP 5
#define SADB_SATYPE_OSPFV2 6
#define SADB_SATYPE_RIPV2 7
#define SADB_SATYPE_MIP 8
#define SADB_SATYPE_MAX 8
#define SADB_SASTATE_LARVAL 0
#define SADB_SASTATE_MATURE 1
#define SADB_SASTATE_DYING 2
#define SADB_SASTATE_DEAD 3
#define SADB_SASTATE_MAX 3
#define SADB_SAFLAGS_PFS 1
#define SADB_AALG_NONE 0
#define SADB_AALG_MD5HMAC 2
#define SADB_AALG_SHA1HMAC 3
#define SADB_AALG_MAX 3
#define SADB_EALG_NONE 0
#define SADB_EALG_DESCBC 2
#define SADB_EALG_3DESCBC 3
#define SADB_EALG_NULL 11
#define SADB_EALG_MAX 11
#define SADB_IDENTTYPE_RESERVED 0
#define SADB_IDENTTYPE_PREFIX 1
#define SADB_IDENTTYPE_FQDN 2
#define SADB_IDENTTYPE_USERFQDN 3
#define SADB_IDENTTYPE_MAX 3
#define SADB_KEY_FLAGS_MAX 0
#endif /* __PFKEY_V2_H */
Appendix E: Change Log
The following changes were made between 05 and 06:
* Last change before becoming an informational RFC. Removed all
Internet-Draft references. Also standardized citation strings.
Now cite RFC2119 for MUST, etc.
* New appendix on optional KM private data extension.
* Fixed example to indicate the ACQUIRE messages with errno mean
KM failure.
* Added SADB_EALG_NULL.
* Clarified proxy examples to match definition of PROXY address being
the inner packet's source address. (Basically a sign-flip. The
example still shows how to protect against policy vulnerabilities
in tunnel endpoints.)
* Loosened definition of a destination address to include broadcast.
* Recommended that LARVAL security associations have implicit short
lifetimes.
The following changes were made between 04 and 05:
* New appendix on Passive Change message.
* New sadb_address_prefixlen field.
* Small clarifications on sadb_ident_id usage.
* New PFKEYV2_REVISION value.
* Small clarification on what a PROXY address is.
* Corrected sadb_spirange_{min,max} language.
* In ADD messages that are in response to an ACQUIRE, the
sadb_msg_seq MUST be the same as that of the originating ACQUIRE.
* Corrected ACQUIRE message behavior, ACQUIRE message SHOULD send up
PROXY addresses when it needs them.
* Clarification on SADB_EXPIRE and user-level security protocols.
The following changes were made between 03 and 04:
* Stronger language about manual keying.
* PFKEYV2_REVISION, ala POSIX.
* Put in language about sockaddr ports in ACQUIRE messages.
* Mention of asymmetric algorithms.
* New sadb_ident_id field for easier construction of USER_FQDN
identity strings.
* Caveat about source addresses not always used for collision
detection. (e.g. IPsec)
The following changes were made between 02 and 03:
* Formatting changes.
* Many editorial cleanups, rewordings, clarifications.
* Restrictions that prevent many strange and invalid cases.
* Added definitions section.
* Removed connection identity type (this will reappear when it is
more clear what it should look like).
* Removed 5.2.1 (Why involve the kernel?).
* Removed INBOUND, OUTBOUND, and FORWARD flags; they can be computed
from src, dst, and proxy and you had to anyway for sanity checking.
* Removed REPLAY flag; sadb_sa_replay==0 means the same thing.
* Renamed bit lengths to "bits" to avoid potential confusion.
* Explicitly listed lengths for structures.
* Reworked identities to always use a string format.
* Removed requirements for support of shutdown() and SO_USELOOPBACK.
* 64 bit alignment and 64 bit lengths instead of 32 bit.
* time_t replaced with uint64 in lifetimes.
* Inserted Appendix A (SADB_X_PROMISC) and Appendix B (SAMPLE HEADER
FILE).
* Explicit error if PF_KEY_V2 not set at socket() call.
* More text on SO_USELOOPBACK.
* Made fields names and symbol names more consistent.
* Explicit error if PF_KEY_V2 is not in sadb_msg_version field.
* Bytes lifetime field now a 64-bit quantity.
* Explicit len/exttype wording.
* Flattening out of extensions (LIFETIME_HARD, LIFETIME_SOFT, etc.)
* UI example (0x123 == 0x1230 or 0x0123).
* Cleaned up and fixed some message behavior examples.
The following changes were made between 01 and 02:
* Mentioned that people COULD use these same messages between user
progs. (Also mentioned why you still might want to use the actual
socket.)
* Various wordsmithing changes.
* Took out netkey/ directory, and make net/pfkeyv2.h
* Inserted PF_KEY_V2 proto argument per C. Metz.
* Mentioned other socket calls and how their PF_KEY behavior is
undefined.
* SADB_EXPIRE now communicates both hard and soft lifetime expires.
* New "association" extension, even smaller base header.
* Lifetime extension improvements.
* Length now first in extensions.
* Errors can be sent from kernel to user, also.
* Examples section inserted.
* Some bitfield cleanups, including STATE and SA_OPTIONS cleanup.
* Key splitting now only across auth algorithm and encryption
algorithm. Thanks for B. Sommerfeld for clues here.
The following changes were made between 00 and 01:
* Added this change log.
* Simplified TLV header syntax.
* Splitting of algorithms. This may be controversial, but it allows
PF_KEY to be used for more than just IPsec. It also allows some
kinds of policies to be placed in the KMd easier.
* Added solid definitions and formats for certificate identities,
multiple keys, etc.
* Specified how keys are to be layed out (most-to-least bits).
* Changed sequence number semantics to be like an RPC transaction ID
number.
F. Full Copyright Statement
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This document and translations of it may be copied and furnished to
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