Network Working Group M. Richardson
Internet-Draft SSW
Expires: May 6, 2009 November 2, 2008
An abstract interface between applications and IPsec
draft-ietf-btns-abstract-api-02.txt
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Abstract
This document explains in the abstract (no language bindings are
provided) how an application may learn that IPsec has been applied to
a conversation or specify that IPsec should be used. Though this is
useful in general it is particularly useful for applications that
wish to use BTNS (Better Than Nothing Security -- a mode of IPsec
keying), either in conjunction with channel binding or otherwise.
Table of Contents
1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . 4
3. Objects involved . . . . . . . . . . . . . . . . . . . . . 5
3.1. Scope of Protection Token . . . . . . . . . . . . . . . . 5
3.2. Scope of Identity Token . . . . . . . . . . . . . . . . . 6
3.3. Validity period of Protection Token . . . . . . . . . . . 6
3.4. Validity period of Identity Token . . . . . . . . . . . . 6
3.5. Serialization . . . . . . . . . . . . . . . . . . . . . . 6
3.5.1. Serialization of Protection Token . . . . . . . . . . . . 6
3.5.2. Serialization of Identity Token . . . . . . . . . . . . . 7
4. Name space . . . . . . . . . . . . . . . . . . . . . . . . 8
5. pToken discovery . . . . . . . . . . . . . . . . . . . . . 9
6. pToken templates . . . . . . . . . . . . . . . . . . . . . 10
7. Properties of pToken objects . . . . . . . . . . . . . . . 11
8. Properties of iToken objects . . . . . . . . . . . . . . . 12
9. Accessors Functions . . . . . . . . . . . . . . . . . . . 14
10. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . 15
11. Security Considerations . . . . . . . . . . . . . . . . . 16
12. IANA Considerations . . . . . . . . . . . . . . . . . . . 17
13. Acknowledgments . . . . . . . . . . . . . . . . . . . . . 18
14. TRACKING . . . . . . . . . . . . . . . . . . . . . . . . . 19
15. References . . . . . . . . . . . . . . . . . . . . . . . . 21
15.1. Normative references . . . . . . . . . . . . . . . . . . . 21
15.2. Non-normative references . . . . . . . . . . . . . . . . . 21
Author's Address . . . . . . . . . . . . . . . . . . . . . 22
Intellectual Property and Copyright Statements . . . . . . 23
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1. Overview
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC2119 [RFC2119].
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2. Introduction
Implementation of application protocols that depend on IPsec
[RFC4301] tend to depend on configuration of IPsec, without having
any portable (or even non-portable) way to ensure that IPsec is being
used properly. This state of affairs is unfortunate, as it limits
use of IPsec and encourages applications not to rely on IPsec, which
in environments that do use IPsec, may lead to redundant
cryptographic protection layers.
This document describes an abstract application programming interface
(API) that is intended to interface applications with IPsec. It is
abstract in that no programming language specific bindings are given
here, nor is this API specified in terms of familiar APIs such as the
"BSD sockets API," for example. Programming language specific
bindings, and operating system specific bindings are left to other
documents.
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3. Objects involved
There are two major kinds of objects that are defined by this
document. These are the Protection Token (pToken) and the Identity
Token (iToken). Both objects are abstracted into unique opaque
tokens which may be manipulated only indirectly by applications.
Here we use the term "opaque token" to mean much what "object" means
in a typical object-oriented programming language, but with no public
fields (only methods or generic functions). Additionally, the iToken
may be serialized -- that is, converted, by application of a suitable
function, into an octet string that can later be imported to create a
new iToken object that is equivalent to the original (though a value
equality test applied to both iTokens may fail).
Each object has a series of attributes associated with it. The API
provides a mechanism to query the value of attributes of the token.
The attributes are where all of the content of the objects are.
Each token has a scope - the place and time in which it can be
considered valid. There are many conflicting qualities that one
would wish for the token, and the result is a different compromise
among these qualities for each token type. The tokens should be:
easy to allocate and release
automatically cleaned up when an application terminates (both
properly and improperly)
easily compared (for equivalence)
easily interfaced with existing APIs (such as the BSD sockets API,
in that case as "auxiliary data")
We use terms such as "process" and "address space" without explaining
them or providing references, much as with "object." The terms refer
to pervasive, common concepts in operating systems theory and
practice over the past several decades.
3.1. Scope of Protection Token
The protection token has a per-process (i.e. per-address space)
scope, though it may be inherited by child processes in operating
systems that have a "fork()" operation. It SHOULD always be possible
to obtain a current protection token for an established connection
(whether for a connection-oriented transport protocol or for a
"connected" UDP socket). that is equivalent to any previous
protection token that was obtained. The scope of the token is not
related to any specific underlying Security Associations used by
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IPsec, but to the entire set of past, current and future SAs that
will be used by IPsec to protect that connection
[I-D.ietf-btns-connection-latching].
3.2. Scope of Identity Token
The identity token also has a per-process scope, but is serializable
such that its serialized form has a per-system or even universal,
scope. (We have to consider whether we want universal scope for
serialized iTokens, much as with exported name objects in the GSS-
API, which would mean agreeing on a standard, extensible
representation and encoding.)
3.3. Validity period of Protection Token
A pToken is valid only within the scope of a single process (though
it may be inherited by child processes which share the parent's
address space with copy on write semantics). The token may not be
serialized, and, therefore, may not be saved in any long term
storage.
It is permitted for one protection token to be replaced with another
(equivalent) protection token due to a node moving, suspending and
resuming, or due to extended network outages, however the underlying
identity token would be guaranteed to be the same. This would most
likely occur with unconnected sockets, where due to the outage/
downtime, the keying system was unable to maintain a keying channel,
and had to re-create the keys from scratch.
3.4. Validity period of Identity Token
The iToken may be valid across the entire system, although it may
need to be turned into an external representation (serialization).
Some forms of identity token may be valid across systems, but in
general an identity token is only valid in reference to a local
policy. (See [RFC2692]).
3.5. Serialization
Serialization refers to the process of turning an in memory object
into a format which can be saved on disk, and re-imported by the same
implementation. This document does not require a specification for
the serialization format, only that it be possible. The format is a
local matter.
3.5.1. Serialization of Protection Token
There is no requirement to serialize the protection token, or the
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attributes contained within. There is a desire to serialize
templates for protection tokens such that a set of minimum security
requirements can be saved for future connections to the same peer.
3.5.2. Serialization of Identity Token
There is a desire to be able to to serialize the identity token in
such a way that future communications can be confirmed to be with the
same identity as before.
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4. Name space
All symbols (functions, macros, etc.) defined by this API are
prefixed with "ipsec_". Specific rules for capitalizations should be
driven by the specific language binding.
Whenever sensible, the enumerated values defined in [RFC2367] are
used if appropriate.
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5. pToken discovery
An application that receives a connection using accept(2) (or
recvmsg(2)), or makes a connection using connect(2), needs to get a
protection token that is associated with the socket.
For connected sockets (UDP, TCP, some SCTP modes, etc.), the
protection token MUST not change during the lifetime of the socket,
so a simple process is appropriate.
([I-D.ietf-btns-connection-latching])
As the pToken will not change during the connection. (see notes about
re-keying). A simple function is provided to return a pToken from a
file descriptor. Many implementations are likely to implement this
using getsockopt(2), but an interface in those terms is not specified
in order to keep it more abstract, and therefore more portable.
For unconnected sockets (such as UDP and some SCTP modes), each
datagram received may be received may arrive from a different source,
and therefore may have different protections applied. A protection
token needs to be returned with each datagram, so it must be returned
as ancillary data with recvmsg(2).
A server using unconnected sockets, would receive a protection token
as ancillary data, and then would provide the same protection token
as ancillary data on the corresponding sendmsg(2) call.
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6. pToken templates
A pToken template is a type of pToken which is used only when setting
up a connection, or setting up a socket to listen for connections.
Properties which are not set on a pToken, are assumed to be do-not-
care values.
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7. Properties of pToken objects
privacyProtected - boolean. Set to false if the connection has
either no privacy configured (AH, ESP-null), or if the privacy
configured is known to be untrustworthy by the administrator.
Returns true otherwise. (XXX: False does not mean that there will
be no IPsec, but that it should not be considered useful)
integrityProtected - boolean. Set to false if there is no data
integrity protection other than the UDP/TCP checksum.
compressionAvailable - boolean. Set to true if data count sent/
received from socket may not map linearly to data sent/received on
wire.
policyName - string. A handle which describes the system policy
which was used (or is desired), to establish the connection. This
is a string, such as: "secure", "ospf", "iSCSI", "very-secure",
"do-not-tell-mom-secure", "minimum-security", "was-posted-on-
usenet-security".
iToken - object. Set to iToken object which represents identity
of remote system.
remote_iToken - object. Set to iToken object which was used to
represent our identity to the remote system.
tunnelMode - boolean. Set if tunnel mode was used, or if it is
desired.
ipoptionsProtected - boolean. Set if ip options (and IPv6 header
extensions), are protected.
auditString - string. readonly. Not part of a template. Valid
only after connection establishment. Contains a string which can
be used in system auditing and logging functions which describes
the details of the IPsec SA that was negotiated. No structure of
this string may be assumed. No session keys are disclosed by this
string.
informationString - string. readonly. Not part of a template.
Valid only after connection establishment. Contains a string
which can be displayed to a user, informing them of what kind of
security association was established for this connection. This
string may be localized. No session keys are disclosed by this
string.
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8. Properties of iToken objects
auditString - string. readonly on responder and readonly on
initiator after connection establishment. Contains a string which
can be used in system auditing and logging functions which
describes the remote identity, and the method by which it was
authenticated (i.e. it may list the CA or origin of a public key)
authenticationMethod - enumerated type. Indicates which method
was used to authenticate the peer, possible values are:
NONE - the peer was not authenticated in anyway
BTNS - the peer was authenticated using an inline key which was
not verified in anyway
LEAPOFFAITH - the peer was authenticated using a key which was
previously cached, but was previously received inline, and was
not verified in anyway.
PRESHAREDKEY - the peer was authenticated using a unique pre-
shared key
GROUPKEY - the peer was authenticated using a non-unique pre-
shared key
XAUTH - the type of phase1/PARENT-SA is not relevant, as the
peer was authenticated using a username/password.
EAP - the type of phase1/PARENT-SA is not relevant, as the peer
was authenticated using an EAP method. (Additional properties
may provide more information)
PKIX_TRUSTED - the peer was authenticated using a PKIX/X.509
certificate that was found in the trusted store.
PKIX_INLINE - the peer was authenticated using a PKIX/X.509
certificate that was transmitted inline, and was verified by
using a Certificate Authority that was found in the trusted
store.
PKIX_OFFLINE - the peer was authenticated using a PKIX/X.509
certificate that was retrieved out-of-band (such as by LDAP or
HTTP), and was verified by using a Certificate Authority that
was found in the trusted store.
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certificateAuthorityDN - string. readonly. the Distinguished Name
(DN) of certificate authority that was used to verify the key (for
methods that involved PKIX)
certificateDN - string. readonly. the DN of the peer that was
authenticated
pubKeyID - string. readonly. a somewhat unique identifier for the
public key. A suggestion is to use the first 9 base64 digits of
the RFC3110 public key modulus, but this is a local matter.
channelBinding - binary blog. readonly. provides the concatenated
set of public keys
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9. Accessors Functions
Methods to access the properties of the two objects are specific to
the language in which the bindings are done. See YYYY for
C-bindings.
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10. Use Cases
Explain slides from IETF68.
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11. Security Considerations
Probably lots to say here. Please help.
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12. IANA Considerations
There are no registries created by this document. The names (and
language specific enum, if applicable) of the pToken and iToken
properties are internal to a single system, and therefore do not need
standardization.
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13. Acknowledgments
stuff
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14. TRACKING
Document RCS tracking info
$Revision: 1.7 $
$Log: ietf-btns-abstract-api.xml,v $
Revision 1.7 2008/11/03 02:45:52 mcr
spell check and updated references
Revision 1.6 2008/02/18 02:37:45 mcr
updated edits.
Revision 1.5 2007/07/24 22:15:51 nico
New abstract, new intro, various minor changes (scope of objects,
etc...).
Revision 1.4 2007/07/24 03:30:19 mcr
edits to token scope, in collaboration with Nico.
Revision 1.3 2007/07/19 20:09:50 mcr
added more properties to describe the type of the SA.
Revision 1.2 2007/07/19 19:45:55 mcr
edits from 2007-07-19 discussion.
Revision 1.1 2007/06/25 15:34:08 mcr
renamed drafts in Makefile
Revision 1.3 2007/05/14 19:56:37 mcr
added abstract
Revision 1.2 2007/05/12 20:38:56 mcr
fixed id string
Revision 1.1 2007/05/12 01:31:00 mcr
updates to abstract api document
Revision 1.4 2007/02/16 03:24:09 mcr
updated to make XML happy, and dates corrected
Revision 1.3 2007/02/16 03:04:44 mcr
C API document.
Revision 1.2 2006/03/21 22:02:47 mcr
added API requirements and skeleton of original API spec
Revision 1.1 2006/03/21 21:04:43 mcr
added documents from ipsp WG
Revision 1.1 2003/06/03 20:45:06 mcr
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initial template
Figure 1: document tracking
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15. References
15.1. Normative references
[I-D.ietf-btns-connection-latching]
Williams, N., "IPsec Channels: Connection Latching",
draft-ietf-btns-connection-latching-07 (work in progress),
April 2008.
[I-D.ietf-btns-core]
Williams, N. and M. Richardson, "Better-Than-Nothing-
Security: An Unauthenticated Mode of IPsec",
draft-ietf-btns-core-07 (work in progress), August 2008.
[I-D.ietf-btns-prob-and-applic]
Touch, J., Black, D., and Y. Wang, "Problem and
Applicability Statement for Better Than Nothing Security
(BTNS)", draft-ietf-btns-prob-and-applic-07 (work in
progress), July 2008.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2367] McDonald, D., Metz, C., and B. Phan, "PF_KEY Key
Management API, Version 2", RFC 2367, July 1998.
[RFC2692] Ellison, C., "SPKI Requirements", RFC 2692,
September 1999.
15.2. Non-normative references
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, December 2005.
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Author's Address
Michael C. Richardson
Sandelman Software Works
470 Dawson Avenue
Ottawa, ON K1Z 5V7
CA
Email: mcr@sandelman.ottawa.on.ca
URI: http://www.sandelman.ottawa.on.ca/
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