IP Security Remote Access (ipsra)

Last Modified: 2002-12-04

Chair(s):

Paul Hoffman <paul.hoffman@vpnc.org>
Sara Bitan <sarab@cs.technion.ac.il>

Security Area Director(s):

Russell Housley <housley@vigilsec.com>
Steven Bellovin <smb@research.att.com>

Security Area Advisor:

Steven Bellovin <smb@research.att.com>

Mailing Lists:

General Discussion: ietf-ipsra@vpnc.org
To Subscribe: ietf-ipsra-request@vpnc.org
In Body: subscribe
Archive: http://www.vpnc.org/ietf-ipsra/mail-archive/

Description of Working Group:

The work of the IPSec working group is almost concluded at the time
this charter is being written.  The IPSEC working group has produced
three proposed-standard protocols: AH, ESP, and IKE.

When the IPSec WG considered requirements for the protocols it
produced, inadequate attention was given to the support for so-called
"road warriors"-- remote users that use personal portable computing
devices, or who use Internet "kiosks" to access private networks on the
other side of an IPSEC gateway.  Such users will typically connect to
the Internet at a point most convenient to them at the time of
connection:

  o Dial-in to a local ISP

  o Wireless or wired LAN access at a conference, hotel or airport

There are some fundamental differences, that are relevant to IPSec
usage, between these remote access scenarios and scenarios where both
parties reside in fixed locations:

-  The authenticated entity must be a human user, i.e. human
    interaction is required during the authentication process.

-  In each session the remote access entity interacts with at least two
    access points- the Internet access point and the organization entry
    point. The authentication must be established between the remote
    access entity and the entry point to its organization (and not into
    the ISP).

-  The remote access entity wishes to connect to its organization's
    distributed network. This network might be large and complex and
    with multiple remote access entry points.  Although the user
    physical location is not changing during the remote access session,
    he might use different entry points during the same session.

-  In the above scenario, the entry points don't have information on
    all the entities that are allowed to access the network. When the
    remote access begins the entry point should obtain information on
    the remote access entity that will enable it to grant secure access
    to the network. This information might be credentials supplied by
    the remote access entity itself, or information supplied by some
    other server.

-  Several human users can share the same physical machine.

-  The remote access entity doesn't have its configuration information.
    This information must be transported securely to the remote access
    implementation after the entity's identity has been authenticated.

-  There are systems that rely on different identities for access
    control - examples are IP address, users names and others. Most of
    the time the user's remote access implementation won't have this
    information available to it before the connection begins.
    Organizations will not change their access control systems. Hence
    this information must be conveyed securely to the remote access's
    implementation after the authentication.

IKE supports four authentication methods; one method is based on pre-
shared secrets, while the other three are all public-key variants, with
various desirable properties.  The use of pre-shared secrets scales
very badly, requiring O(N**2) keys to be managed to provide effective
security.  The authentication methods based on public-key technology
assume, to a certain extent, that the organization involved has
deployed its own public-key infrastructure for authentication of
individual human users. This assumption is taking much longer to reach
fruition than one would hope.

Most organizations have legacy authentication systems that are adequate
for providing authentication of individual human users (OTP,
username/password, hardware authentication tokens, etc).  Most
organizations insist on the ability to continue to to support such
legacy authentication mechanisms as they deploy an IPSEC infrastructure
at the perimeter of their networks.

The goals of this working group are:

- to define a remote access architecture. The entities participating
  in the remote access and their relationships will be defined in a
  framework document. This document will be published as an
  Informational RFC.

- to define a standard mechanism to accomplish human user
  authentication to an IPSec device running IKE, using legacy
  authentication mechanisms. One of the goals of introducing this
  mechanism is to allow for an easy migration path to PKI. The
  mechanism will be published as a standards-track protocol document.

- to define a standard mechanism to convey user configuration
  information from user's own private network to its local IPSec
  implementation. This mechanism will be published as a
standards-track
  protocol document.

- to provide a standard mechanism to convey user information required
  for access control from the user's own private network to its local
  IPSec implementation,  while answering the special requirements of
  remote access users. This mechanism will be published as a
standards-
  track protocol document.

- to work closely with the MOBILEIP Working Group so that the
  respective protocols work together.

The WG strongly prefers mechanisms that require no changes to AH, ESP
or IKE protocols. If such changes are deemed necessary, the IPSec WG is
contracted to carry out such changes. Pursuing this approach is most
likely to produce mechanisms that are easy to implement and deploy.

Goals and Milestones:

MAR 00    Submit Internet-Drafts of requirements and framework documents
MAR 00    First WG meeting
JUL 00    Requirements document submitted for Informational
JUL 00    Remote access framework submitted for standards track
DEC 00    User authentication to IKE mechanism submitted for standard track
DEC 00    User configuration mechanism submitted for standard track
MAR 01    User access control mechanism submitted for standard track

Internet-Drafts:

PIC, A Pre-IKE Credential Provisioning Protocol (63512 bytes)

Request For Comments:

Dynamic Host Configuration Protocol (DHCPv4) Configuration of IPsec Tunnel Mode (RFC 3456) (40340 bytes)
Requirements for IPsec Remote Access Scenarios (RFC 3457) (75167 bytes)