Network Working Group D. L. McDonald
Internet Draft C. W. Metz
draft-mcdonald-pf-key-v2-01.txt B. G. Phan
17 March 1997
PF_KEY Key Management API, Version 2
STATUS OF THIS MEMO
This document is an Internet Draft. Internet Drafts are working
documents.
Internet Drafts are draft documents valid for a maximum of 6
months. Internet Drafts may be updated, replaced, or obsoleted by
other documents at any time. It is not appropriate to use Internet
Drafts as reference material or to cite them other than as "work in
progress".
A future version of this draft will be submitted to the RFC Editor
for publication as an Informational document.
ABSTRACT
A generic key management API that can be used not only for IP
Security [Atk95a] [Atk95b] [Atk95c] but also for other network
security services is presented in this document. Version 1 of this
API was implemented inside 4.4-Lite BSD as part of the U. S. Naval
Research Laboratory's freely distributable and usable IPv6 and IPsec
implementation[AMPMC96]. It is documented here for the benefit of
others who might also adopt and use the API, thus providing increased
portability of key management applications (e.g. an ISAKMP daemon, a
Photuris daemon or SKIP certificate discovery protocol daemon).
1. INTRODUCTION
PF_KEY is a new socket protocol family used by trusted privileged
key management applications to communicate with an operating system's
key management internals (referred to here as the "Key Engine" or the
SADB). The Key Engine and its structures incorporate the required
security attributes for a session and are instances of the "Security
Association" concept described in [Atk95a]. The names, PF_KEY and
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Key Engine, thus refer to more than cryptographic keys and are
retained for consistency with the traditional phrase, "Key
Management".
PF_KEY is derived in part from the BSD routing socket, PF_ROUTE.
[Skl91] This document describes Version 2 of PF_KEY. Version 1 was
implemented in the first three alpha test versions of the NRL
IPv6+IPsec Software Distribution for 4.4-Lite BSD UNIX and the Cisco
ISAKMP/Oakley key management daemon. Version 2 extends and refines
this interface.
Security policy is deliberately omitted from this interface.
PF_KEY is not a mechanism for tuning systemwide security policy, nor
is it intended to enforce any sort of key management policy. The
developers of PF_KEY believed that it was important to separate
security mechanisms (such as PF_KEY) from security policies. This
permits a single mechanism to more easily support multiple policies.
1.1 TERMINOLOGY
In this document, the words that are used to define the
significance of each particular requirement are usually capitalized.
These words are:
- MUST
This word or the adjective "REQUIRED" means that the item is an
absolute requirement of the specification.
- SHOULD
This word or the adjective "RECOMMENDED" means that there might
exist valid reasons in particular circumstances to ignore this item,
but the full implications should be understood and the case carefully
weighed before taking a different course.
- MAY
This word or the adjective "OPTIONAL" means that this item is truly
optional. One vendor might choose to include the item because a
particular marketplace requires it or because it enhances the
product, for example; another vendor may omit the same item.
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1.2 CONCEPTUAL MODEL
This section describes the conceptual model of an operating system
that implements the PF_KEY key management application programming
interface. This section is intended to provide background material
useful to understand the rest of this document. Presentation of this
conceptual model does not constrain a PF_KEY implementation to
strictly adhere to the conceptual components discussed in this
subsection.
Key management is most commonly implemented in whole or part at the
application-layer. For example, the Photuris, ISAKMP, and Oakley
proposals for IPsec key management are all application-layer
protocols. Even parts of the SKIP IP-layer keying proposal can be
implemented at the application layer. Figure 1 shows the
relationship between a Key Management daemon and PF_KEY, which it
uses to communicate with the Key Engine, and PF_INET (or PF_INET6 in
the case of IPv6), which it uses to communicate via the network with
a remote key management entity.
The "Key Engine" or "Security Association Database (SADB)" is a
logical entity in the kernel that stores, updates, and deletes
Security Association data for various security protocols. There are
logical interfaces within the kernel (e.g. getassocbyspi(),
getassocbysocket()) that security protocols inside the kernel (e.g.
IP Security, aka IPsec) use to request and obtain Security
Associations.
In the case of IPsec, if by policy a particular outbound packet
needs processing, then the IPsec implementation requests an
appropriate Security Association from the Key Engine via the kernel-
internal interface. If the Key Engine has an appropriate SA, it
allocates the SA to this session (marking it as used) and returns the
SA to the IPsec implementation for use. If the Key Engine has no
such SA but a key management application has previously indicated
(via a PF_KEY SADB_REGISTER message) that it can obtain such SAs,
then the Key Engine requests that such an SA be created (via a PF_KEY
SADB_ACQUIRE message). When the key management daemon creates a new
SA, it places it into the Key Engine for future use.
+---------------+
|Key Mgmt Daemon|
+---------------+
| |
| |
| | Applications
======[PF_KEY]====[PF_INET]==========================
| | OS Kernel
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+------------+ +-----------------+
| Key Engine | | TCP/IP, |
| or SADB |---| including IPsec |
+------------+ | |
+-----------------+
|
+-----------+
| Network |
| Interface |
+-----------+
Figure 1: Relationship of Key Mgmt to PF_KEY
For performance reasons, some security protocols (e.g. IP Security)
are usually implemented inside the operating system kernel. Other
security protocols (e.g. OSPFv2 Cryptographic Authentication) are
implemented in trusted privileged applications outside the kernel.
Figure 2 shows a trusted, privileged routing daemon using PF_INET to
communicate routing information with a remote routing daemon and
using PF_KEY to request, obtain, and delete Security Associations
used with a routing protocol.
+---------------+
|Routing Daemon|
+---------------+
| |
| |
| | Applications
======[PF_KEY]====[PF_INET]==========================
| | OS Kernel
+------------+ +---------+
| Key Engine | | TCP/IP |
| or SADB |---| |
+------------+ +---------+
|
+-----------+
| Network |
| Interface |
+-----------+
Figure 2: Relationship of Trusted Application to PF_KEY
When a trusted privileged application is using the Key Engine but
implements the security protocol within itself, then operation varies
slightly. In this case, the application needing an SA sends a PF_KEY
SADB_ACQUIRE message down to the Key Engine, which then either
returns an error or sends a similar SADB_ACQUIRE message up to one or
more key management applications capable of creating such SAs. As
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before, the key management daemon stores the SA into the Key Engine.
Then, the trusted privileged application uses a SADB_GET message to
obtain the SA from the Key Engine.
In some implementations, policy may be implemented in user-space,
even though the actually cryptographic processing takes place in the
kernel. Such policy communication between the kernel mechanisms and
the user-space policy MAY be implemented by PF_KEY extensions, or
other such mechanism. This document will not specify such
extensions.
Untrusted clients, for example a user's web browser or telnet
client, do not need to use PF_KEY. Mechanisms not specified here are
used by such untrusted client applications to request security
services (e.g. IPsec) from an operating system. For security
reasons, only trusted, privileged applications are permitted to open
a PF_KEY socket.
1.3 PF_KEY SOCKET DEFINITION
The PF_KEY protocol family (PF_KEY) symbol is defined in
<sys/socket.h> in the same manner that other protocol families are
defined. PF_KEY does not use any socket addresses. Applications
using PF_KEY MUST NOT depend on the availability of a symbol named
AF_KEY, but kernel implementations are encouraged to define that
symbol for completeness.
The key socket is created as follows:
#include <netkey/key.h>
int s;
s = socket(PF_KEY, SOCK_RAW, 0)
The PF_KEY domain currently supports only the SOCK_RAW socket type.
The protocol field MUST be set to 0. Only a trusted, privileged
process can create a PF_KEY socket. On conventional UNIX systems, a
privileged process is a process with an effective userid of zero. On
non-MLS proprietary operating systems, the notion of a "privileged
process" is implementation-defined. On Compartmented Mode
Workstations (CMWs) or other systems that claim to provide Multi-
Level Security (MLS), a process MUST have the "key management
privilege" in order to open a PF_KEY socket[DIA]. MLS systems that
don't currently have such a specific privilege MUST add that special
privilege and enforce it with PF_KEY in order to comply and conform
with this specification. Some systems, most notably some popular
personal computers, do not have the concept of a privileged user.
These systems SHOULD take steps to restrict the programs allowed to
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access the PF_KEY API.
1.4 OVERVIEW OF PF_KEY MESSAGING BEHAVIOR
A process interacts with the key engine by sending and receiving
messages using the PF_KEY socket. Security association information
can be inserted into and retrieved from the kernel's security
association table using a set of predefined messages. In the normal
case, all messages sent to the kernel are returned to all open PF_KEY
sockets, including the sender. A process can disable this looping
back of messages it generates by disabling the SO_USELOOPBACK option
using the setsockopt(2) call. A PF_KEY socket listener, which by
default receives all replies may disable message reception by
terminating socket input with the shutdown(2) call. PF_KEY message
delivery is not guaranteed, especially in cases where kernel or
socket buffers are exhausted and messages are dropped.
Some messages are generated by the operating system to indicate
that actions need to be taken, and are not necessarily in response to
any message sent down by the user. Such messages are not received by
all PF_KEY sockets, but by sockets which have indicated that kernel-
originated messages are to be received. These messages are special
because of the expected frequency at which they will occur. Also, an
implementation may further wish to restrict return message from the
kernel, in cases where not all PF_KEY sockets are in the same trust
domain.
*******
NOTE: SECTIONS LIKE THIS, INSIDE ******* ARE META-COMMENTS AND OPEN
ISSUES THAT NEED CONTEXT TO BE CLEAR.
[RJA: Clarifying text on security restrictions is needed here, IMHO.]
*******
1.5 COMMON PF_KEY OPERATIONS
There are two basic ways to add a new Security Association into the
kernel. The simplest is to send a single SADB_ADD message,
containing all of the SA information, from the application into the
kernel's Key Engine. This approach works particularly well with
manual key management.
The second approach to add a new Security Association into the
kernel is for the application to first request an SPI value from the
kernel using the SADB_GETSPI message and then send a SADB_UPDATE
message with the complete Security Association data. This second
approach works well with key management daemons when the SPI values
need to be known before the entire Security Association data is known
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(e.g. so the SPI value can be indicated to the remote end of the key
management session).
An individual Security Association can be deleted using the
SADB_DELETE message. Categories of SAs or the entire kernel SA table
can be deleted using the SADB_FLUSH message.
The SADB_GET message is used by a trusted application-layer process
(e.g. routed(8) or gated(8)) to retrieve an SA (e.g. RIP SA or OSPF
SA) from the kernel's Key Engine.
The kernel or an application-layer can use the SADB_ACQUIRE message
to request that a Security Association be created by some
application-layer key management process that has registered with the
kernel via a SADB_REGISTER message. This ACQUIRE message will have a
sequence number associated with it. This sequence number MUST be
used by followup SADB_GETSPI and SADB_UPDATE messages, in order to
keep track of which request gets its keying material. The sequence
number (described below) is analogous to a transaction ID in a remote
procedure call.
The SADB_EXPIRE message is sent from the kernel to key management
applications when the "soft lifetime" or "hard lifetime" of a
Security Association has expired. Key management applications should
use receipt of a SADB_EXPIRE message as a hint to negotiate a
replacement SA so the replacement SA will be ready and in the kernel
before it is needed.
A SADB_DUMP message is also defined, but this is primarily intended
for PF_KEY implementer debugging and is not used in ordinary
operation of PF_KEY.
1.6 DIFFERENCES BETWEEN PF_KEY AND THE PF_ROUTE ROUTING SOCKET
The following bullets are points of difference between the routing
socket and PF_KEY. Programmers who are used to the routing socket
semantics will find some subtle differences in PF_KEY.
* The write() call doesn't return the PF_KEY error number, only the
return message has the PF_KEY error number in cases of malformed fields.
This means that if SO_USELOOPBACK is disabled, error checking is hard.
* The entire message isn't always reflected in the reply. An SADB_ADD is
a good example of this.
* The PID is not set by the kernel. The process that originates the message
MUST set the sadb_msg_pid to its own PID. If the kernel originates a
message, it MUST set the sadb_msg_pid to 0.
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2. PF_KEY MESSAGE FORMAT
PF_KEY messages consist of a base header followed by additional
data fields, some of which may be optional. The format of the
additional data is dependent on the type of message.
PF_KEY messages currently do not mandate any specific ordering for
non-network multi-octet fields. Fields that may go across the wire
(e.g. SPI) MUST be in network byte order.
2.1 BASE MESSAGE HEADER FORMAT
PF_KEY messages consist of the base message header followed by
security association specific data whose types and lengths are
specified by a generic type-length encoding.
This base header is shown below, using POSIX types. The fields are
arranged primarily for alignment, and where possible, for reasons of
clarity.
struct sadb_msg_hdr {
/* Basic hdr stuff */
uint8_t sadb_version; /* 2 */
uint8_t sadb_msg_type;
uint8_t sadb_msg_errno;
uint8_t sadb_sa_type;
uint16_t sadb_msg_len; /* In 32-bit words, incl. */
uint16_t sadb_sa_assocopts;
uint32_t sadb_msg_seq;
uint32_t sadb_msg_pid;
/* Basic SA stuff */
uint32_t sadb_sa_spi;
uint8_t sadb_sa_replay_window_len;
uint8_t sadb_sa_state;
uint8_t sadb_sa_encrypt; /* Or uint16_t */
uint8_t sadb_sa_auth; /* sadb_sa_transform */
};
sadb_version The version field of this PF_KEY message. Set to 2.
sadb_msg_type Identifies the type of message. The valid message types
are described later in this document.
sadb_msg_errno Should be set to zero by the sender. The replier stores
the error code in this field if an error has occured.
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*******
[C. Metz: In some cases, it may be useful for the user-space
program to send errnos. In the case of proxying key
management, a EHOSTUNREACH may tell the kernel that there
is no peer for this server. For that matter such errnos
could work in the cases of no peer KMd being present.
These are in the context of having received an ACQUIRE
message.]
*******
sadb_sa_type indicates the type of security association (e.g. AH,
ESP, OSPF, etc). Valid Security Association types are
declared in the file <netkey/key.h>. The current set of
Security Association types are enumerated later in this
document.
sadb_msg_len Contains the total length, in 32-bit words, of all data in
the PF_KEY message including the base header length and
additional data after the base header, if any. This length
includes any padding or extra space that might exist. Unless
otherwise stated, all other length fields are also
measured in 32-bit words.
sadb_sa_assocopts
Contains a bitmap of options defined for the security
assocation (e.g. replay protection, PFS, etc.).
*******
[Dan McD: I may need to re-split these up into algorithm flags and
association flags. Some of these span both, some don't. ]
*******
sadb_msg_seq Contains the sequence number of this message. This field,
along with sadb_msg_pid, SHOULD be used to uniquely identify
requests to a process. The sender is responsible for filling
in this field. This resposibility also includes matching
the sadb_msg_seq of a request (e.g. SADB_ACQUIRE).
This field is analogous to a transaction ID in a remote
procedure call implementation.
*******
[Dan McD.: It may turn out that both sequence number and transaction
id are needed. In that case, I'll add another uint32_t.]
*******
sadb_msg_pid Identifies the process which originated this message, or
which process a message is bound for. For example: If
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process id 2112 sends a SADB_UPDATE message to the kernel,
the message to the kernel MUST set its process id to 2112,
and the SADB_UPDATE reply from the kernel will fill in this
fields with 2112. This field, along with sadb_msg_seq,
can be used to uniquely identify requests to a process.
It is currently believed that a 32-bit quantity will
hold an operating system's process ID space. If this
assumption is not true, then sadb_msg_pid will have to
be revisited.
*******
[Dan McD.: The seq and pid fields semantics change explicitly from
the routing socket semantics. This better facilitates
asynchronous kernels, while not taking away anything from
synchronous kernels. ]
*******
sadb_sa_spi Contains the Security Parameters Index value for the
Security Association. Although this is a 32-bit field,
some types of Security Association might have an SPI or
key identifier that is less than 32-bits long. In this
case, the smaller value shall be stored in the least
significant bits of this field and the unneeded bits
shall be zero. This field MUST be in network byte order.
*******
[Dan McD: ISAKMP can negotiate an SPI that's >32-bits. I may save this
for v3, though.]
*******
sadb_sa_replay_window_len
Specifies the size of the replay window, if not zero. If
zero, then no replay window is in use.
sadb_sa_state Is a bitmask field containing the state of the Security
Association. This field should be set to zero by the
sending process and is set to the state of the Security
Association when the message is received. The current
set of State flags are enumerated later in this
document.
*******
[Dan McD: The following fields may get merged into one 16-bit
sadb_sa_transform field, depending.]
*******
sadb_sa_encrypt Identifies the encryption algorithm used for this security
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association. This can identify that no encryption is used
for this association. See section 3.4 for values that can
be placed in this field.
sadb_sa_auth Identifies the authentication algorithm used for this
security association. This can identify that no
authentication is used for this association. See section
3.4 for values that can be placed in this field.
The kernel MUST check sanity in these cases. For example AH
with no authentication algorithm is probably an error.
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2.3 ADDITIONAL MESSAGE FIELDS
The additional data following the base header consists of various
type-length-values fields. The first 32-bits are of a constant form:
struct sadb_ext_hdr {
uint16_t ext_hdrtype; /* 0 is reserved */
uint16_t ext_len; /* In 32-bit words, inclusive */
};
There are currently seven types of extensions headers: Lifetime,
Address, Key, Identity, Sensitivity, Proposal, and Supported. There
SHOULD be only one instance of a extension type in a message. (e.g.
Base, Key, Lifetime, Key is STRONGLY discouraged).
All extensions MUST be implemented by a PF_KEY implementation.
2.3.1 LIFETIME EXTENSION
The Lifetime extension specifies a lifetime for this security
association. If no Lifetime extension is present the association
has an infinite lifetime. An association SHOULD have a lifetime of
some sort associated with it. The Lifetime extension looks like:
struct sadb_lifetime {
uint16_t life_hdrtype; /* 1 */
uint16_t life_len;
uint8_t life_type; /* Time, bytes, packets... */
uint8_t life_size; /* 2, 4, 8, 16, etc. octets */
uint16_t life_reserved; /* Or quantity */
/* uint64_t or uint32_t might follow. */
};
The life_size field is in octets, while the life_len field is in
32-bit words. The lifetime extension MAY be followed by a 32-bit
aligned quantity if the life_size field is larger than 2 octets,
otherwise the the lifetime itself can be stored in the 16-bit
life_reserved field.
Values for life_type are defined in the SYMBOLIC NAMES section.
2.3.2 ADDRESS EXTENSION
The Address extension specifies one or more addresses that are
associated with a security association. An Address extension MUST
be present, and MUST specify at least the source and destination
addresses. (The source address can be INADDR_ANY or it's IPv6
counterpart.) The format of an Address extension is:
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struct sadb_address {
uint16_t addr_hdrtype; /* 2 */
uint16_t addr_len;
uint8_t addr_which; /* Bitmask */
uint8_t addr_reserved[3]; /* Padding */
/* Followed by one or more struct sockaddr structures. */
};
The addr_which field contains a bitmask indicating what addresses;
source, destination, inner-source, inner-destination, and proxy;
follow. For each bit set in the addr_which field, a struct sockaddr
follows. The sockaddr structure MUST conform to the sockaddr
structure of the system implementing PF_KEY. (E.g. If the system
has an sa_len field, so MUST the sockaddrs in the message. If the
system has NO sa_len field, the sockaddrs MUST not have an sa_len
field.) All non-address information in the sockaddrs MUST be zeroed
out.
2.3.3 KEY EXTENSION
The Key extension specifies one or more keys that are associated
with a security association. A Key extension will not always be
present with messages, because of security risks. The format of a
Key extension is:
struct sadb_keyblk {
uint16_t kb_hdrtype; /* 3 */
uint16_t kb_len;
uint8_t kb_num_auth; /* # of auth. keys/ivs */
uint8_t kb_num_encrypt; /* # of encrypt. keys/ivs */
uint16_t kb_reserved; /* For 32-bit alignment */
/* Followed by sadb_key */
};
The Key extension is followed by the appropriate number of
authentication or encryption keys. These keys are encoded as
follows:
struct sadb_key {
uint8_t key_type; /* 3DES, DES, HMAC-MD5, etc. */
uint8_t key_flags; /* Right now, am I an IV? */
uint16_t key_length; /* Length of key in bits */
uint8_t key_key[4]; /* Actual key/iv. */
/* key_key is bounded by roundup(key_length / 8) */
};
The length of individual keys is in bits. Each key is padded to a
32-bit boundary. The key bits are arranged most-sigificant to least
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significant. For example, a 22-bit key would take up three octets,
with the least significant two bits not containing key material. An
additional octet would be used for padding to a 32-bit boundary.
The key_flags field indicates currently if this key is actually a
negotiated initialization vector.
2.3.4 IDENTITY EXTENSION
The Identity extension contains endpoint identities. If this
extension is not present, key management can assume that the
addresses in the Address extension are the only identities for this
Security Association. The Identity extension looks like:
struct sadb_id_hdr {
uint16_t idh_hdrtype; /* 4 */
uint16_t idh_len;
uint32_t idh_which; /* bitmask */
/* Followed by one or more sadb_certids */
};
The idh_which field is a bitmask, indicating if source or
destination certificate identities are present. Each identity is a
32-bit aligned quantity, specified as:
struct sadb_certid {
uint8_t certid_type;
uint8_t certid_reserved[3]; /* May be used */
/* certid_reserved is unbounded */
};
Following each sadb_certid is 32-bit aligned data. Sometimes it is
in the best interest to use the certid_reserved field for some of
that data. The type of data can either be nothing (if the specified
identity is the address), a null-terminated C string (for fully-
qualified domain names, or mailbox identities), and address/mask
pair (for address ranges), or a port-pair/protocol tuple, used in
concert with the addresses. See the ILLUSTRATION OF MESSAGE LAYOUT
section for details.
2.3.5 SENSITIVITY EXTENSION
The Sensitiviy extension contains security labelling information
for a security association. If this extension is not present, no
sensitivity-related data can be obtained from this security
association. If this extension is present, then the need for
explicit security labelling on the packet is obviated.
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struct sadb_sens_hdr {
uint16_t sens_hdrtype; /* 5 */
uint16_t sens_len;
uint32_t sens_dpd;
uint8_t sens_sens_level;
uint8_t sens_sens_bitmap_len; /* bytes */
uint8_t sens_integ_level;
uint8_t sens_integ_bitmap_len; /* bytes */
/*
* followed by two uint8_t arrays
* uint8_t sens_bitmap[sens_bitmap_len];
* uint8_t integ_bitmap[integ_bitmap_len];
*/
};
The lengths of the bitmaps are in bytes. Following this field are
the bitmaps. Only at the end of the second bitmap does padding to
32-bits occur. The sens_dpd describes the protection domain, which
allows interpretation of the levels and compartment bitmaps.
2.3.6 PROPOSAL EXTENSION
The Proposal extension contains a "proposed situation" of
algorithm preferences. It looks like:
struct sadb_prop_hdr {
uint16_t proph_hdrtype; /* 6 */
uint16_t proph_len;
uint8_t proph_num_auth; /* # of ordered auth algs */
uint8_t proph_num_encrypt; /* # of ordered encrypt algs */
uint8_t proph_algs[2];
/* proph_algs is bounded by num auth + num encrypt */
};
*******
[Dan McD.: As with the base header, this may become a list of
transforms.]
[C. Metz: An argument for the transform side of this is if I want to
express:
My preferences are:
1.) 3DES with HMAC-MD5 auth & replay
2.) 3DES with replay
...
]
*******
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Following the header are a list of one-octet algorithm identifiers, first
authentication algorithms in preferential order, then encryption algorithms
in preferential order.
2.3.7 SUPPORTED ALGORITHMS EXTENSION
The Supported Algorithms extension contains a list of all
algorithms supported by the kernel. This is useful for key
management, as it knows what it can negotiate. Its format is:
struct alg_hdr {
uint16_t algh_hdrtype; /* 7 */
uint16_t algh_len;
uint8_t algh_num_auth; /* # of auth algs supported */
uint8_t algh_num_encrypt; /* # of encrypt algs */
uint16_t algh_reserved;
/* Followed by one or more alg_desc */
};
It is followed by one or more algorithm descriptors. An algorithm
descriptor looks like:
struct alg_desc {
uint8_t algd_type; /* Algorithm type. */
uint8_t algd_flags; /* Algorithm properties (IV, etc.) */
uint8_t algd_ivlen; /* Algorithm IV len, if needed */
uint8_t algd_numkeys; /* Number of keys needed */
uint16_t algd_minlen; /* Minimum key length */
uint16_t algd_maxlen; /* Maximum key length */
};
32-bit alignment is guaranteed by the fields automatically. The
flags indicate properties such as an initialization vector. The
minlen and maxlen are key lengths in bits.
2.3.8 SPI RANGE EXTENSION
One PF_KEY message, SADB_GETSPI, might need a range of acceptable
SPI values. This extension performs such a function.
struct sadb_spirange {
uint16_t spir_type; /* 8 */
uint16_t spir_len;
uint32_t spi_low;
uint32_t spi_hi;
}
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2.4 ILLUSTRATION OF MESSAGE LAYOUT
The following shows how the octets are layed out in a PF_KEY message.
Optional fields are indicated as such.
The base header is as follows:
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+---------------+---------------+---------------+---------------+
| sadb_version | sadb_msg_type | sadb_msg_errno| sadb_sa_type |
+---------------+---------------+---------------+---------------+
| sadb_msg_len | sadb_sa_assocopts |
+---------------+---------------+---------------+---------------+
| sadb_msg_seq |
+---------------+---------------+---------------+---------------+
| sadb_msg_pid (NOTE: Assuming pid_t is 32 bits) |
+---------------+---------------+---------------+---------------+
| sadb_sa_spi |
+---------------+---------------+---------------+---------------+
| ...replay... | sadb_sa_state |sadb_sa_encrypt| sadb_sa_auth |
+---------------+---------------+---------------+---------------+
The base header may be followed by one or more of the following
extension fields, depending on the values of various base header
fields. The following fields are ordered such that if they appear,
they SHOULD appear in the order presented below.
An extension field MUST not be repeated. If there is a situation
where an extension MUST be repeated, it should be brought to the
attention of the authors.
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The Lifetime extension
0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+---------------+---------------+---------------+---------------+
| life_hdrtype (1) | life_len |
+---------------+---------------+---------------+---------------+
| life_type | life_size | life_reserved |
+---------------+---------------+---------------+---------------+
> lifetime_value, if 32-bit or 64-bit quantity <
+---------------+---------------+---------------+---------------+
The Address extension
+---------------+---------------+---------------+---------------+
| addr_hdrtype (2) | addr_len |
+---------------+---------------+---------------+---------------+
| addr_which | addr_reserved |
+---------------+---------------+---------------+---------------+
> 32-bit aligned struct sockaddr(s) <
+---------------+---------------+---------------+---------------+
The Key extension
+---------------+---------------+---------------+---------------+
| kbh_hdrtype (3) | kbh_len |
+---------------+---------------+---------------+---------------+
| kbh_num_auth |kbh_num_encrypt| kbh_reserved |
+---------------+---------------+---------------+---------------+
> One or more actual keys, encoded as follows... <
+---------------+---------------+---------------+---------------+
An actual key
+---------------+---------------+---------------+---------------+
| kh_type | kh_flags | kh_length |
+---------------+---------------+---------------+---------------+
> A key, padded to 32-bits, most sigificant bits to least. <
+---------------+---------------+---------------+---------------+
The Identity extension
+---------------+---------------+---------------+---------------+
| idh_hdrtype (4) | idh_len |
+---------------+---------------+---------------+---------------+
| idh_which |
+---------------+---------------+---------------+---------------+
> One or more certificate identities of the following forms <
+---------------+---------------+---------------+---------------+
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IPv6 address or IPv4 address should look in the previous Address
extension for actual values.
+---------------+---------------+---------------+---------------+
| certid_type | certid_reserved |
+---------------+---------------+---------------+---------------+
NOTE that certid_reserved gets filled with useful fields for some
identity types.
An IPv6 or IPv4 address range
+---------------+---------------+---------------+---------------+
| certid_type |pref_len (bits)| certid_reserved |
+---------------+---------------+---------------+---------------+
> 16-bytes of IPv6 or 4-bytes of IPv4 address prefix <
+---------------+---------------+---------------+---------------+
A Fully-qualified domain name, or a mailbox ID.
+---------------+---------------+---------------+---------------+
| certid_type | A null-terminated C-string |
+---------------+---------------+---------------+---------------+
> which MUST be padded out for 32-bit alignment <
+---------------+---------------+---------------+---------------+
A connection ID, which uses address plus port/protocol information.
+---------------+---------------+---------------+---------------+
| certid_type | protocol_id | certid_reserved |
+---------------+---------------+---------------+---------------+
| source_port | destination_port |
+---------------+---------------+---------------+---------------+
The Sensitivity extension
+---------------+---------------+---------------+---------------+
| sens_hdrtype (5) | sens_len |
+---------------+---------------+---------------+---------------+
| sens_dpd |
+---------------+---------------+---------------+---------------+
|sens_sens_level| ...bitmap_len |sens_integ_lev | ...bitmap_len |
+---------------+---------------+---------------+---------------+
> The sensitivity bitmap, followed immediately by the integrity <
< bitmap, padded to a 32-bit quantity. >
+---------------+---------------+---------------+---------------+
The Proposal extension
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+---------------+---------------+---------------+---------------+
| proph_hdrtype (6) | proph_len |
+---------------+---------------+---------------+---------------+
| proph_num_auth|proph_num_encr.| 1st auth alg | 2nd auth alg |
+---------------+---------------+---------------+---------------+
> Nth auth alg... then 1st encrypt alg, etc. Padded for 32-bits<
+---------------+---------------+---------------+---------------+
The Supported Algorithms extension
+---------------+---------------+---------------+---------------+
| algh_hdrtype (7) | algh_len |
+---------------+---------------+---------------+---------------+
| algh_num_auth |algh_num_encr. | algh_reserved |
+---------------+---------------+---------------+---------------+
Followed by one or more Algorithm Descriptors
+---------------+---------------+---------------+---------------+
| algd_type | algd_flags | algd_ivlen | algd_numkeys |
+---------------+---------------+---------------+---------------+
| algd_minlen | algd_maxlen |
+---------------+---------------+---------------+---------------+
The SPI Range extension
+---------------+---------------+---------------+---------------+
| spir_hdrtype (8) | spir_len |
+---------------+---------------+---------------+---------------+
| spir_hi |
+---------------+---------------+---------------+---------------+
| spir_low |
+---------------+---------------+---------------+---------------+
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3. SYMBOLIC NAMES
This section defines various symbols used with PF_KEY and the
semantics associated with each symbol. Applications SHOULD use the
symbolic name in order to be maximally portable. The numeric
definitions shown are for illustrative purposes, unless explicitly
stated otherwise. The numeric definition might vary on other
systems. The symbolic name MUST be kept the same for all conforming
implementations.
*******
[Dan McD: Should I give a prefix, like SADB_X_*, so that
implementation-specific hacks (i.e. policy) can fit in?]
*******
3.1 MESSAGE TYPES
The following message types are used with PF_KEY. These are
defined in the file <netkey/key.h>.
#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 /* not used by normal applications */
Each message has a behavior. A behavior is defined as where the
initial message travels (e.g. user to kernel), and what subsequent
actions are expected to take place. Contents of messages are
illustrated as:
<base, REQUIRED EXTENSION, REQ., (OPTIONAL EXT.,) (OPT) >
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In the case of an error, only the base header is returned.
3.1.1 SADB_GETSPI Message
The SADB_GETSPI message allows a process to obtain a unique SPI value for
given security association type, source address, and destination address.
This message followed by a SADB_UPDATE is one way to create a security
association (SADB_ADD is the other method). The process specifies the type
in the base header, the source and destination address in address extension,
and, if proxy key management is in use, the internal sockaddrs or the proxy
sockaddr are also included in the address extension. If the SADB_GETSPI
message is in response to a kernel-generated SADB_ACQUIRE, the sadb_msg_seq
MUST be the same as the SADB_ACQUIRE message. The application may also
specifiy the SPI. This is done by either setting the sadb_sa_spi field to a
single SPI, or having the kernel select within a range of SPI values by using
the SPI range extension. This use of the lifetime extension to specify SPI
ranges is detailed later. Permitting range specification is important
because the kernel can allocate an SPI value based on what it knows about SPI
values already in use. The kernel returns the same message with the
allocated SPI value stored in the spi field. An update message can later be
used to add an entry with the requested SPI value.
The message behavior of the SADB_GETSPI message is:
Send a SADB_GETSPI message from a user process to the kernel.
<base, address, (SPI range)>
The kernel returns the SADB_GETSPI message to all listening
processes.
<base, address>
Errors:
EINVAL Various message improprieties, including SPI ranges that
are malformed.
ENOBUFS No buffer space is available to process request.
EEXIST Requested SPI or SPI range is not available/already used.
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3.1.2 SADB_UPDATE Message
The SADB_UPDATE message allows a process to update the information
in an existing Security Association. Since SADB_GETSPI does not
allow setting of certain parameters, this message is needed to fully
form the larval security association created with SADB_GETSPI. The
format of the update message is a base header, followed by the
relevant extensions. If the keying material, lifetimes, compartment
bitmaps, or certificate identities need to be updated, these
extensions should be included. The kernel searches for the security
association with the same type, spi, source address and destination
address specified in the message and updates the Security Association
information using the content of the SADB_UPDATE message.
The kernel SHOULD perform sanity checking on various technical
parameters passed in as part of the SADB_UPDATE message. One example
is DES key parity bit checking. Other examples include key length
checking, and checks for keys known to be weak for the specified
algorithm.
The kernel SHOULD NOT allow SADB_UPDATE to succeed unless the
message is issued from the same socket that created the security
association. Such enforcement significantly reduces the chance of
accidental changes to an in-use security associations. Malicious
trusted parties could still issue a SADB_FLUSH or SADB_DELETE
message, but deletion of associations is more easily detected and
less likely to occur accidentally than an erroneous SADB_UPDATE.
The message behavior of the SADB_UPDATE message is:
Send a SADB_UPDATE message from a user process to the kernel.
<base, (lifetime,) address, key, (identity,) (sensitivity)>
The kernel returns the SADB_UPDATE message to all listening
processes.
<base, (lifetime,) address, (identity,) (sensitivity)>
The keying material is not returned on the message from the kernel
to listening sockets because listeners might not have the privileges
to see such keying material.
Errors:
ESRCH The security association to be updated was not found.
EINVAL Various message improprieties, including sanity check
failures on keys.
EACCES Insufficient privilege to update entry. Socket issuing
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the SADB_UPDATE is not creator of the entry to be updated.
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3.1.3 SADB_ADD Message
The SADB_ADD message is nearly identical to the SADB_UPDATE
message, except that it does not require a previous call to
SADB_GETSPI. The SADB_ADD message is optimal for manual keying
applications, and other strategies where the uniqueness of the SPI is
known immediately.
An SADB_ADD message is also used when negotiation is finished, and
the second of a pair of associations is added. The SPI for this
association was determined by the peer machine. It MAY be useful to
set the sadb_msg_seq to that of a kernel-generated SADB_ACQUIRE so
that both associations in a pair are bound to the same ACQUIRE
request.
The message behavior of the SADB_ADD message is:
Send a SADB_ADD message from a user process to the kernel.
<base, (lifetime,) address, key, (identity,) (sensitivity)>
The kernel returns the SADB_ADD message to all listening
processes.
<base, (lifetime,) address, (identity,) (sensitivity)>
The keying material is not returned on the message from the kernel to
listening sockets because listeners may not have the privileges to see
such keying material.
Errors:
EEXIST The security association that was to be added already
exists.
EINVAL Various message improprieties, including sanity check
failures on keys.
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3.1.4 SADB_DELETE Message
The SADB_DELETE message causes the kernel to delete a Security
Association from the key table. The delete message consists of the
base header followed by the source sockaddr and the destination
sockaddr in the address extension. The kernel deletes the security
association matching the type, spi, source address, and destination
address in the message.
There are two message behaviors for SADB_DELETE. The first is a
user- originated deletion
Send a SADB_DELETE message from a user process to the kernel.
<base, address>
The kernel returns the SADB_DELETE message to all listening
processes.
<base, address>
The second behavior is in the case of a hard-limit lifetime
expiration.
The kernel sends a SADB_DELETE message to all listening
processes when a security association times out.
<base, address>
Errors:
ESRCH The security association to be deleted was not found.
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3.1.5 SADB_GET Message
The SADB_GET message allows a process to retrieve a copy of a
Security Association from the kernel's key table. The get message
consists of the base header follows by the relevant extension fields.
The Security Association matching the type, spi, source address, and
destination address is returned. The K_USED flag is set inside the
Key Engine for the returned Security Association.
The message behavior of the SADB_GET message is:
Send a SADB_GET message from a user process to the kernel.
<base, address>
The kernel returns the SADB_GET message to the socket that sent
the SADB_GET message.
<base, (lifetime,) address, key, (identity,) (sensitivity)>
Errors:
ESRCH The sought security association was not found.
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3.1.6 SADB_ACQUIRE Message
The SADB_ACQUIRE message is typically sent only by the kernel to
key socket listeners who have registered their key socket (see
SADB_REGISTER message). SADB_ACQUIRE messages can be sent by
application-level consumers of security associations (such as an
OSPFv2 implementation that uses OSPF security). The SADB_ACQUIRE
message is a base header along with an address extension, possibly a
certificate identity extension, and if more than one algorithm and
options is acceptable, a proposal extension. The proposed situation
contains a list of desirable algorithms that can be used if the
algorithms in the base header are not available. The values for the
fields in the base header and in the security association data which
follows the base header indicate the properties of the Security
Association that the listening process should attempt to acquire. If
the message originates from the kernel (i.e. the sadb_msg_pid is 0),
the sadb_seq number MUST be used by a subsequent SADB_GETSPI message
to bind a security association to the request. This avoids the race
condition of two TCP connections between two IP hosts that each
require unique associations, and having one steal another's security
association. The sadb_errno and sadb_state fields should be ignored
by the listening process.
The SADB_ACQUIRE message is typically triggered by an outbound
packet that needs security but for which there is no applicable
Security Association existing in the key table. If the packet can be
sufficiently protected by more than one algorithm or combination of
options, the SADB_ACQUIRE message MUST order the preference of
possibilities by placing the most preferred algorithm in the base
header, and the subsequent ones in the proposed_situation field in
order of preference.
There are two messaging behaviors for SADB_ACQUIRE. The first is
where the kernel needs a security association (e.g. for IPsec).
The kernel sends a SADB_ACQUIRE message to registered sockets.
<base, address, (identity,) (sensitivity,) (proposal)>
The second is where an application-layer consumer of security
associations (e.g. an OSPFv2 or RIPv2 daemon) needs a security
association.
Send a SADB_ACQUIRE message from a user process to the kernel.
<base, address, (identity,) (sensitivity,) (proposal)>
The kernel returns a SADB_ACQUIRE message to registered sockets.
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<base, address, (identity,) (sensitivity,) (proposal)>
The user-level consumer waits for a SADB_UPDATE or SADB_ADD message
for its particular type, and then can use that association by using
SADB_GET messages.
Errors:
EINVAL Invalid acquire request.
EPROTONOSUPPORT No KM application has registered with the Key
Engine as being able to obtain the requested SA type, so
the requested SA cannot be acquired.
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3.1.7 SADB_REGISTER Message
The SADB_REGISTER message allows an application to register its key
socket as able to acquire new security associations for the kernel.
SADB_REGISTER allows a socket to receive SADB_ACQUIRE messages for
the type of security association specified in sadb_sa_type. The
application specifies the type of security association that it can
acquire for the kernel in the type field of its register message. If
an application can acquire multiple types of security association, it
MUST register each type in a separate message. Only the base header
is needed for the register message. For portability reasons, key
management applications MAY register for a type not known to the
kernel.
The reply of the SADB_REGISTER message contains a supported
algorithm extension. That field contains an array of supported
algorithm, one per octet. This allows key management applications to
know what algorithm are supported by the kernel.
In an enviroment where algorithms can be dynamically loaded and
unloaded, an asyncryonous SADB_REGISTER reply MAY be generated. The
list of supported algorithms MUST be a complete list, so the
application can make note of omissions or additions.
The messaging behavior of the SADB_REGISTER message is:
Send a SADB_REGISTER message from a user process to the kernel.
<base>
The kernel returns a SADB_REGISTER message, with algorithm types
supported by the kernel being indicated in the supported algorithms
field.
NOTE: This message may arrive asynchronously due to an algorithm
being loaded or unloaded into a dynamically linked kernel.
<base, supported>
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3.1.8 SADB_EXPIRE Message
The operating system kernel is responsible for tracking SA
expirations for security protocols that are implemented inside the
kernel. If the soft limit of a Security Association has expired for
a security protocol implemented inside the kernel, then the kernel
MUST issue an SADB_EXPIRE message to all key socket listeners. A
user application is responsible for tracking SA expirations for
security protocols (e.g. OSPF Authentication) that are implemented
inside that user application. If the soft limit of a Security
Association has expired, the user application SHOULD issue a
SADB_EXPIRE message. Regardless of where the security protocol is
implemented, if both the soft limit and the hard limit expire at the
same time, both SADB_DELETE and SADB_EXPIRE messages MUST be sent.
The base header will contain the security association information
followed by the source sockaddr, destination sockaddr, (and, if
present, internal sockaddr,) (and, if present, one or both
compartment bitmaps).
The messaging behavior of the SADB_EXPIRE message is:
The kernel sends a SADB_EXPIRE message when the soft limit of a
security association has been expired.
<base, address, (identity,) (sensitivity)>
ERRORS:
EINVAL Message Invalid for some reason.
EPROTONOSUPPORT ???
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3.1.9 SADB_FLUSH Message
The SADB_FLUSH message causes the kernel to delete all entries in
its key table for a certain sadb_sa_type. Only the base header is
required for a flush message. If sadb_sa_type is filled in with a
specific value, only associations of that type are deleted. If it is
filled in with SEC_TYPE_NONE, ALL associations are deleted.
The messaging behavior for SADB_FLUSH is:
Send a SADB_FLUSH message from a user process to the kernel.
<base>
The kernel will return a SADB_FLUSH message to all listening
sockets.
<base>
The reply message happens only after the actual flushing
of security associations has been attempted.
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3.1.10 SADB_DUMP Message
The SADB_DUMP message causes the kernel to dump the operating
system's entire Key Table to the requesting key socket. As in
SADB_FLUSH, if a sadb_sa_type value is in the message, only
associations of that type will be dumped. If SEC_TYPE_NONE is
specified, all associations will be used. Each Security Association
is returned in its own SADB_DUMP message. A SADB_DUMP message with a
sadb_seq field of zero indicates the end of the dump transaction.
Unlike other key messages, the dump message is returned only to the
key socket originating the dump request because of the potentially
large amount of data it can generate. The dump message is used for
debugging purposes only and is not intended for production use.
Support for the dump message MAY be discontinued in future versions
of the key socket, hence key management applications MUST NOT depend
on this message for basic operation.
The messaging behavior for SADB_DUMP is:
Send a SADB_DUMP message from a user process to the kernel.
<base>
Several SADB_DUMP messages will return from the kernel to the
sending socket.
<base, (lifetime,) address, key, (identity,) (sensitivity)>
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3.2 SECURITY ASSOCIATION STATE
The Security Association's state is a bitmask field. The related
symbolic definitions below should be used in order that applications
will be maximally portable:
#define SA_USED 0x01 /* SA used/not used */
#define SA_UNIQUE 0x02 /* SA unique/reusable */
#define SA_LARVAL 0x04 /* SPI assigned, but SA incomplete */
#define SA_ZOMBIE 0x08 /* SA expired but still useable */
#define SA_DEAD 0x10 /* SA marked for deletion */
#define SA_INBOUND 0x20 /* SA for packets destined here */
#define SA_OUTBOUND 0x40 /* SA for packets sourced here */
#define SA_FORWARD 0x80 /* SA for packets forwarded thru */
SA_USED is set by the operating system if the Security Association
has been used. Otherwise this flag is not set. If SADB_GET is used
to read an SA from the Key Engine, the Key Engine will set SA_USED on
the SA that was read via SADB_GET.
SA_UNIQUE is set by the operating system if the Security
Association has been allocated uniquely to a single user (e.g. a
particular network socket). If this is not set, then the Security
Association is considered sharable.
SA_LARVAL indicates that the operating system has assigned this SPI
value but that there is no complete Security Association yet stored
in the kernel.
SA_ZOMBIE indicates a Security Association that has expired but is
still useable until a replacement Security Association is added.
This is primarily used with OSPFv2 and RIPv2 cryptographic
authentication.
SA_DEAD indicates a Security Association that exists but is marked
for deletion.
SA_INBOUND is set for an inbound Security Association and
SA_OUTBOUND is set for an outbound Security Association. SA_FORWARD
is used for a Security Association used only for packets originating
elsewhere and destined elsewhere that have security processing on
this node. All Security Associations used with PF_KEY are
unidirectional.
*******
[Dan McD.: Why SA_FORWARD? Isn't SA_OUTBOUND sufficient? I may
implement forwarding such that it's hard or impossible for
the key engine/SADB to tell the difference. ]
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*******
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3.3 SECURITY ASSOCIATION TYPE
This defines the type of Security Association in this message. The
numeric definitions are those used in the prototype NRL
implementation, but might be different on other implementations. The
symbolic names are always the same, even on different
implementations. Applications should use the symbolic name in order
to have maximum portability across different implementations. These
are defined in the file <netkey/key.h>.
#define SEC_TYPE_NONE 0
#define SEC_TYPE_AH 1 /* RFC-1826 */
#define SEC_TYPE_ESP 2 /* RFC-1827 */
#define SEC_TYPE_RSVP 3 /* RSVP Authentication */
#define SEC_TYPE_OSPFV2 4 /* OSPFv2 Authentication */
#define SEC_TYPE_RIPV2 5 /* RIPv2 Authentication */
#define SEC_TYPE_MIPV4 6 /* Mobile IPv4 Authentication */
#define SEC_TYPE_MAX 6
SEC_TYPE_NONE is defined for completeness and means no
Security Association. This type is never used with PF_KEY.
SEC_TYPE_AH is for the IP Authentication Header defined in
[Atk95b]. SEC_TYPE_ESP is for the IP Encapsulating Security Payload
defined in [Atk95c].
SEC_TYPE_RSVP is for the RSVP Integrity Object.
SEC_TYPE_OSPFv2 is for OSPFv2 Cryptographic authentication,
while SEC_TYPE_RIPv2 is for RIPv2 Cryptographic authentication.
SEC_TYPE_MAX is never used with PF_KEY but is defined for
completeness. It is always set to the highest valid numeric value.
There MUST not be gaps in the numbering of security types; all
numbers must be used sequentially.
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3.4 ALGORITHM TYPES
The algorithm type is interpreted in the context of the Security
Association type defined above. The numeric value might vary between
implementations, but the symbolic name MUST NOT vary between
implementations. Applications should use the symbolic name in order
to have maximum portability to various implementations.
Some of the algorithm types defined below might not be standardized
or might be deprecated in the future. To obtain an assignment for a
symbolic name, contact the editor.
The symbols below are defined in <netkey/key.h>.
/* Authentication algorithms */
#define SADB_AALG_NONE 0
#define SADB_AALG_MD5_HMAC 1
#define SADB_AALG_SHA1_HMAC 2
/* Encryption algorithms */
#define SADB_EALG_NONE 0
#define SADB_EALG_DES_CBC 1
#define SADB_EALG_3DES 2
*******
[Dan McD.: This whole section is in anticipation of IPsec departing from
a pure "transform" model. This also allows security schemes
that do not have a transform model at all. ]
*******
The algorithm for SADB_AALG_MD5_HMAC is defined in [OG96]. The
algorithm for SADB_AALG_SHA1_HMAC is defined in [CG96]. The
algorithm for SADB_EALG_DES_CBC is defined in [Hug96].
3.5 ASSOCIATION OPTIONS
Security association types can have various options defined.
Options are denoted by a bit setting in the "Type Options" field of
the base header. The bitmasks for defined options MUST NOT vary
between implementations. Bits not defined are RESERVED and MUST NOT
be used.
#define SA_OPTION_PFS 0x0001 /* Use Perfect Forward Secrecy */
#define SA_OPTION_REPLAY 0x0002 /* Replay Protection enabled */
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The SEC_OPTION_PFS flag indicates to key management that this
association should have perfect forward secrecy in its key. (In
other words, the session key cannot be determined by cryptanalysis of
previous keying material.)
The SEC_OPTION_REPLAY specifies that replay protection should be
enabled on this association. The sadb_sa_replay_window_len field
will indicate the size of the replay field.
3.6 EXTENSION HEADER VALUES
To briefly recap the extension header values:
#define SA_EXT_RESERVED 0 /* Reserved */
#define SA_EXT_LIFETIME 1
#define SA_EXT_ADDRESS 2
#define SA_EXT_KEY 3
#define SA_EXT_IDENTITY 4
#define SA_EXT_SENSITIVITY 5
#define SA_EXT_PROPOSAL 6
#define SA_EXT_SUPPORTED 7
#define SA_EXT_SPI_RANGE 8
3.7 LIFETIME EXTENSION VALUES
The life_type field can contain the following values:
#define SA_LIFETYPE_TIME 0
#define SA_LIFETYPE_BYTES 1
#define SA_LIFETYPE_PACKETS 2
Each value specifies a type of association lifetime.
3.8 ADDRESS EXTENSION VALUES
The addr_which field is a bitmask which can indicate what sockaddrs
follow, and what they represent. These bit values are:
#define SADB_ADDR_SRC 0x1
#define SADB_ADDR_DST 0x2
#define SADB_ADDR_INNER_SRC 0x4
#define SADB_ADDR_INNNER_DST 0x8
#define SADB_ADDR_PROXY 0x10
3.9 KEY EXTENSION VALUES
These are already mentioned in the ALGORITHM TYPES section.
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3.10 IDENTITY EXTENSION VALUES
The idh_which field is a bitmask which indicates what identities
follow.
#define SADB_ID_SRC 0x1
#define SADB_ID_DST 0x2
Each identity can have a certain type.
#define SADB_IDT_IPV4_ADDR 1
#define SADB_IDT_IPV6_ADDR 2
#define SADB_IDT_IPV4_RANGE 3
#define SADB_IDT_IPV6_RANGE 4
#define SADB_IDT_FQDN 5
#define SADB_IDT_USER_FQDN 6
#define SADB_IDT_IPV4_CONNID 7
#define SADB_IDT_IPV6_CONNID 8
3.11 SENSITIVITY EXTENSION VALUES
The only field currently defined in the sensitivity extension is
the sens_dpd, which represents the data protection domain. The other
data in the senstivity extension is based off the sens_dpd value.
If the highest order bit of the DP/DOI is set to 1, then the DP/DOI
is not necessarily globally unique and is from a number space set
aside for private use among consenting users.
If the highest order bit of the DP/DOI is set to zero, the DP/DOI
is globally unique from a number space administered by the Internet
Assigned Numbers Authority. In order to conserve the limited amount
of globally unique DP/DOI number space, IANA will not normally permit
any one organization to obtain very many DP/DOI values. The all
zeros DP/DOI value is permanently reserved to mean that "no DP/DOI is
in use".
#define SADB_DPD_NONE 0
#define SADB_DPD_DOD_GENSER 1
#define SADB_DPD_DOD_SCI 2
#define SADB_DPD_DOE 3
#define SADB_DPD_NATO 4
3.12 PROPOSAL EXTENSION VALUES
These are already mentioned in the ALGORITHM TYPES section.
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3.12 PROPOSAL EXTENSION VALUES
Values for algd_type are mentioned in the ALGORITHM TYPES section.
Values for the bit vector algd_flags are as follows:
#define SADB_ALGDF_NEED_IV 0x1
4. FUTURE DIRECTIONS
While the current specification for the Sensitivity and Integrity
Labels is believed to be general enough, if a case should arise that
can't work with the current specification then this might cause a
change in a future version of PF_KEY.
Similarly, PF_KEY might need extensions to work with other kinds of
Security Associations in future. It is strongly desirable for such
extensions to be made in a backwards-compatible manner should they be
needed.
*******
[ALL: What else belongs here ? ]
*******
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5. SECURITY CONSIDERATIONS
This draft discusses a method for creating, reading, 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.
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ACKNOWLEDGEMENTS
The editors of this document are listed primarily in Alphabetical
order. A side effect of this particular alphabetical listing is to
also show the history (starting with the most recent) of text
contribution to this document. Ran Atkinson also contributed much
advice and wisdom toward this document. Finally, the editors would
like to thank the PF_KEY reviewers list.
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] Randall J. Atkinson, IP Security Architecture, RFC-1825,
August 1995.
[Atk95b] Randall J. Atkinson, IP Authentication Header, RFC-1826,
August 1995.
[Atk95c] Randall J. Atkinson, IP Encapsulating Security Payload, RFC-1827,
August 1995.
[CG96] S. Chang & Rob Glenn, "HMAC-SHA IP Authentication with Replay
Prevention", Internet Draft, May 1996.
[DIA] US Defense Intelligence Agency (DIA), "Compartmented Mode
Workstation Specification", Technical Report DDS-2600-6243-87.
[Hug96] Jim Hughes (Editor), "Combined DES-CBC, HMAC, and Replay
Prevention Security Transform", Internet Draft, April 1996.
[OG96] Mike Oehler & Rob Glenn, "HMAC-MD5 IP Authentication with
Replay Prevention", Internet Draft, May 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
judgement 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.
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EDITOR INFORMATION
Daniel L. McDonald
Sun Microsystems, Inc.
2550 Garcia Avenue, MS UMPK17-202
Mountain View, CA 94043-1100
E-mail: danmcd@eng.sun.com
Craig W. Metz
The Inner Net
Code 1123, Box 10314
Blacksburg, VA 24062-0314
E-mail: cmetz@inner.net
Bao G. Phan
U. S. Naval Research Laboratory
Code 5544
4555 Overlook Ave. SW
Washington, DC 20375
E-mail: phan@itd.nrl.navy.mil
APPENDIX A: CHANGE LOG
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 policy 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.
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