Below are diffs to draft-williams-on-channel-binding-01.txt including:
- Alexey Melnikov's IANA text
- Fixes to Eric Gray's nits
- New text about EAP channel binding
- A clarification requested by Sam: this doc describes a generic notion
of channel binding, not [just] the GSS-API's
Please review and comment. Particularly w.r.t. EAP channel binding.
--- on-channel-binding-01.txt
+++ on-channel-binding-02.txt
@@ -1,18 +1,18 @@
NETWORK WORKING GROUP N. Williams
Internet-Draft Sun
-Expires: September 6, 2007 March 5, 2007
+Expires: October 18, 2007 April 16, 2007
On the Use of Channel Bindings to Secure Channels
- draft-williams-on-channel-binding-01.txt
+ draft-williams-on-channel-binding-02.txt
Status of this Memo
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79.
@@ -27,17 +27,17 @@
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
- This Internet-Draft will expire on September 6, 2007.
+ This Internet-Draft will expire on October 18, 2007.
Copyright Notice
Copyright (C) The IETF Trust (2007).
@@ -47,19 +47,19 @@
-Williams Expires September 6, 2007 [Page 1]
+Williams Expires October 18, 2007 [Page 1]
-Internet-Draft On Channel Bindings March 2007
+Internet-Draft On Channel Bindings April 2007
Abstract
The concept of channel binding allows applications to establish that
the two end-points of a secure channel at one network layer are the
same as at a higher layer by binding authentication at the higher
layer to the channel at the lower layer. This allows applications to
@@ -71,59 +71,59 @@
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions used in this document . . . . . . . . . . 4
2. Definitions . . . . . . . . . . . . . . . . . . . . . 5
2.1. Properties of channel binding . . . . . . . . . . . . 6
+ 2.2. EAP channel binding . . . . . . . . . . . . . . . . . 8
3. Authentication and channel binding semantics . . . . . 9
3.1. The GSS-API and channel binding . . . . . . . . . . . 9
3.2. SASL and channel binding . . . . . . . . . . . . . . . 9
4. Channel bindings specifications . . . . . . . . . . . 11
4.1. Examples of unique channel bindings . . . . . . . . . 11
4.2. Examples of end-point channel bindings . . . . . . . . 11
5. Uses of channel binding . . . . . . . . . . . . . . . 13
6. Benefits of channel binding to secure channels . . . . 15
7. IANA Considerations . . . . . . . . . . . . . . . . . 16
- 8. Security Considerations . . . . . . . . . . . . . . . 17
+ 7.1. Registration Procedure . . . . . . . . . . . . . . . . 16
+ 7.2. Comments on channel bindings Registrations . . . . . . 17
+ 7.3. Change control . . . . . . . . . . . . . . . . . . . . 18
+ 8. Security Considerations . . . . . . . . . . . . . . . 19
8.1. Non-unique channel bindings and channel binding
- re-establishment . . . . . . . . . . . . . . . . . . . 17
- 9. References . . . . . . . . . . . . . . . . . . . . . . 19
- 9.1. Normative References . . . . . . . . . . . . . . . . . 19
- 9.2. Informative References . . . . . . . . . . . . . . . . 19
- Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 22
- Author's Address . . . . . . . . . . . . . . . . . . . 23
- Intellectual Property and Copyright Statements . . . . 24
+ re-establishment . . . . . . . . . . . . . . . . . . . 19
+ 9. References . . . . . . . . . . . . . . . . . . . . . . 21
+ 9.1. Normative References . . . . . . . . . . . . . . . . . 21
+ 9.2. Informative References . . . . . . . . . . . . . . . . 21
+ Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 24
+ Author's Address . . . . . . . . . . . . . . . . . . . 25
+ Intellectual Property and Copyright Statements . . . . 26
+Williams Expires October 18, 2007 [Page 2]
+Internet-Draft On Channel Bindings April 2007
-
-Williams Expires September 6, 2007 [Page 2]
-
-Internet-Draft On Channel Bindings March 2007
-
-
1. Introduction
In a number of situations, it is useful for an application to be able
to handle authentication within the application layer, while
simultaneously being able to utilize session or transport security at
- a lower network layer. For example, while IPsec [RFC4301] [RFC4303]
+ a lower network layer. For example, IPsec [RFC4301] [RFC4303]
[RFC4302] is amenable to being accelerated in hardware to handle very
high link speeds, but IPsec key exchange protocols and the IPsec
architecture are not as amenable to use as a security mechanism
within applications, particularly applications that have users as
clients. A method of combining security at both layers is therefore
attractive. To enable this to be done securely, it is necessary to
"bind" the mechanisms together -- so as to avoid man-in-the-middle
vulnerabilities and enable the mechanisms to be integrated in a
@@ -131,49 +131,58 @@
The term "channel binding" as used in this document derives from the
GSS-API [RFC2743], which has a channel binding facility that was
intended for binding GSS-API authentication to secure channels at
lower network layers. The purpose and benefits of the GSS-API
channel binding facility were not discussed at length, and some
details were left unspecified. Now we find that this concept can be
very useful, therefore we begin with a generalization and
- formalization of "channel binding."
+ formalization of "channel binding" independent of the GSS-API.
+ Although inspired by and derived from the GSS-API, the notion of
+ channel binding described herein is not at all limited to use by GSS-
+ API applications. We envision use of channel binding by applications
+ that utilize other security frameworks, such as SASL [RFC4422] and
+ even protocols that provide their own authentication mechanisms
+ (e.g., the KDC exchanges of Kerberos V [RFC4120]). We also envision
+ use of the notion of channel binding in the analysis of security
+ protocols.
+
The main goal of channel binding is to be able to delegate
cryptographic session protection to network layers below the
application in hopes of being able to better leverage hardware
implementations of cryptographic protocols. Section 5 describes some
intended uses of channel binding. Some applications may benefit
additionally by reducing the amount of active cryptographic state,
thus reducing overhead in accessing such state and, therefore, the
impact of security on latency.
The critical security problem to solve in order to achieve such
delegation of session protection is: ensuring that there is no man-
in-the-middle (MITM), from the point of view the application, at the
lower network layer to which session protection is to be delegated.
+
+
+
+Williams Expires October 18, 2007 [Page 3]
+
+Internet-Draft On Channel Bindings April 2007
+
+
And there may well be a MITM, particularly if the lower network layer
either provides no authentication or if there is no strong connection
between the authentication or principals used at the application and
those used at the lower network layer.
Even if such MITM attacks seem particularly difficult to effect, the
attacks must be prevented for certain applications to be able to make
effective use of technologies such as IPsec [RFC2401] [RFC4301] or
HTTP with TLS [RFC4346] in certain contexts (e.g., when there is no
-
-
-
-Williams Expires September 6, 2007 [Page 3]
-
-Internet-Draft On Channel Bindings March 2007
-
-
authentication to speak of, or when one node's set of trust anchors
is too weak to believe that it can authenticate its peers).
Additionally, secure channels that are susceptible to MITM attacks
because they provide no useful end-point authentication are useful
when combined with application-layer authentication (otherwise they
are only somewhat "better than nothing" -- see BTNS
[I-D.ietf-btns-prob-and-applic]).
@@ -206,30 +215,21 @@
+Williams Expires October 18, 2007 [Page 4]
+Internet-Draft On Channel Bindings April 2007
-
-
-
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-Williams Expires September 6, 2007 [Page 4]
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-
-
2. Definitions
o Secure channel: a packet, datagram, octet stream connection, or
sequence of connections, between two end-points that affords
cryptographic integrity and, optionally, confidentiality to data
exchanged over it. We assume that the channel is secure -- if an
attacker can successfully cryptanalyze a channel's session keys,
for example, then the channel is not secure.
@@ -261,104 +261,96 @@
channel bindings that name the authenticated end-points, or
even a single end-point, of a channel which are, in turn,
securely bound to the channel, but which do not identify a
channel uniquely in time.
o Cryptographic binding: (e.g., "cryptographically bound") a
cryptographic operation that causes an object, such as a private
encryption or signing key, or an established secure channel, to
- "speak for" [Lapmson91] some principal, such as a user, a
+ "speak for" [Lampson91] some principal, such as a user, a
computer, etcetera. For example, a PKIX certificate binds a
private key to the name of a principal in the trust domain of the
certificate's issuer such that a possessor of said private key can
act on behalf of the user (or other entity) named by the
certificate.
-Williams Expires September 6, 2007 [Page 5]
+Williams Expires October 18, 2007 [Page 5]
-Internet-Draft On Channel Bindings March 2007
+Internet-Draft On Channel Bindings April 2007
- Cryptographic bindings are generally assymetric in nature (not to
+ Cryptographic bindings are generally asymmetric in nature (not to
be confused with symmetric or assymetric key cryptography) in that
an object is rendered capable of standing for another, but the
reverse is not usually the case (we don't say that a user speaks
for their private keys, but we do say that the user's private keys
speak for the user).
Note that there may be many instances of "cryptographic binding" in
an application of channel binding. The credentials that authenticate
principals at the application layer bind private or secret keys to
the identities of those principals, such that said keys speak for
them. A secure channel typically consists symmetric session keys
- used to provide confidentiality and integrity ptoection to data sent
+ used to provide confidentiality and integrity protection to data sent
over the channel; each end-point's session keys speak for that end-
point of the channel. Finally, each end-point of a channel bound to
authentication at the application layer speaks for the principal
authenticated at the application layer on the same side of the
channel.
The terms defined above have been in use for many years and have been
taken to mean, at least in some contexts, what is stated below.
Unfortunately this means that "channel binding" can refer to the
channel binding operation and, sometimes to the name of a channel,
and "channel bindings" -- a difference of only one letter --
generally refers to the name of a channel.
- Also unfortunately there is a conflict with the Extensible
- Authentication Protocol (EAP) [RFC3748] which uses "channel binding"
- to refer to a facility that is subtly different from the one
- described here. (It does not seem feasible to adopt new terminology
- to avoid these problems now. The GSS-API, NFSv4 and other
- communities have been using the terms "channel binding" and "channel
- bindings" in these ways for a long time, sometimes with variations
- such as "channel binding facility" and so on.)
+ Note that the Extensible Authentication Protocol (EAP) [RFC3748]
+ which "channel binding" to refer to a facility that is substantially
+ similar one described here. See Section 2.2 for more details.
2.1. Properties of channel binding
- [NOTE: This section needs more work, I'm sure I've missed
- somethings...]
-
Applications, authentication frameworks (e.g., the GSS-API, SASL),
security mechanisms (e.g., the Kerberos V GSS-API mechanism
[RFC1964]) and secure channels must meet the following requirement
and should follow the following recommendations.
Requirements:
+ o Specifications of channel bindings for any secure channels MUST
+ provide for a single, canonical octet string encoding of the
+ channel bindings.
+ o The channel bindings for a given type of secure channel MUST be
+ constructed in such a way that an MITM could not easily force the
+ channel bindings of a given channel to match those of another.
-Williams Expires September 6, 2007 [Page 6]
-Internet-Draft On Channel Bindings March 2007
+Williams Expires October 18, 2007 [Page 6]
- o Specifications of channel bindings for any secure channels MUST
- provide for a single, canonical octet string encoding of the
- channel bindings.
+Internet-Draft On Channel Bindings April 2007
- o The channel bindings for a given type of secure channel MUST be
- constructed in such a way that an MITM could not easily force the
- channel bindings of a given channel to match those of another.
o Unique channel bindings MUST bind not only the key exchange for
the secure channel, but also any negotiations and authentication
that may have taken place to establish the channel.
o End-point channel bindings MUST be bound into the secure channel
and all its negotiations. E.g., if an end-point channel binding
is the name of a certificate and this certificate is used in
- establishng the channel to sign material, say, all the initinial
- key exchange and negotiation messages for that channel, then that
+ establishng the channel to sign material, say, all the initial key
+ exchange and negotiation messages for that channel, then that
certificate name could be said to be bound into the channel.
o End-point channel bindings may be identifiers which must be
authenticated through some infrastructure, such as a public key
infrastructure (PKI). In such cases the channel binding can be no
stronger, cryptographically, than the infrastructure, including
trust establishment. Applications MUST NOT use end-point channel
bindings when the end-points cannot be strongly authenticated due
@@ -365,47 +357,47 @@
to the configuration of the authentication service (e.g., because
there are too many trust anchors, or because some are of dubious
repute).
o Applications MUST use application-layer session protection
services for confidentiality protection when the bound channel
does not provide confidentiality protection.
- o The integrity of a secure channels MUST NOT be weakened should
+ o The integrity of a secure channel MUST NOT be weakened should
their channel bindings be revealed to an attacker. That is, the
construction of the channel bindings for any type of secure
channel MUST NOT leak secret information about the channel. End-
point channel bindings, however, MAY leak information about the
end-points of the channel (e.g., their names).
o The channel binding operation MUST be at least integrity protected
in the security mechanism used at the application layer.
o Authentication frameworks and mechanisms that support channel
binding MUST communicate channel binding failure to applications.
Recommendations:
-
-
-
-Williams Expires September 6, 2007 [Page 7]
-
-Internet-Draft On Channel Bindings March 2007
-
-
o Applications SHOULD use mutual authentication at the application
layer when using channel binding.
o End-point channel bindings where the end-points are meaningful
names SHOULD NOT be used when the channel does not provide
confidentiality protection and privacy protection is desired.
Alternatively channels that export such channel bindings SHOULD
provide for the use of a digest and SHOULD NOT introduce new
+
+
+
+Williams Expires October 18, 2007 [Page 7]
+
+Internet-Draft On Channel Bindings April 2007
+
+
digest/hash agility problems as a result.
Options:
o Authentication frameworks and mechanisms that support channel
binding MAY fail to establish authentication if channel binding
fails.
@@ -415,45 +407,53 @@
o A security mechanism MAY exchange integrity protected digests of
channel bindings. Such mechanisms SHOULD provide for hash/digest
agility.
o A security mechanism MAY use channel bindings in key exchange,
authentication or key derivation, prior to the exchange of
"authenticator" messages.
+2.2. EAP channel binding
+ This section is informative. This document does not update EAP
+ [RFC3748], it imposes no requirements on EAP nor EAP methods.
+ EAP [RFC3748] includes a concept of channel binding desribed as
+ follows:
+ The communication within an EAP method of integrity-protected
+ channel properties such as endpoint identifiers which can be
+ compared to values communicated via out of band mechanisms (such
+ as via a AAA or lower layer protocol).
+ Section 7.15 of [RFC3748] describes the problem as one where an
+ attacker may impersonate a Network Access Server (NAS), (a.k.a.
+ "authenticator"). Although not stated clearly therein, this leads to
+ an MITM attack on the EAP peer whereby one NAS pretends to be the one
+ that the peer wanted to connect to; the attacker then passes all
+ communications through to the real NAS and ultimately it will be an
+ MITM between the peer and the real NAS.
+ Section 7.15 of [RFC3748] calls for "a protected exchange of channel
+ properties such as endpoint identifiers" such that "it is possible to
+ match the channel properties provided by the authenticator via out-
+ of-band mechanisms against those exchanged within the EAP method."
+ In other words: EAP channel binding is very similar to the generic
+ notion of channel binding described in this document, both in terms
+ of intent and in terms of how it is intended to operate.
+Williams Expires October 18, 2007 [Page 8]
+Internet-Draft On Channel Bindings April 2007
-
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3. Authentication and channel binding semantics
Some authentication frameworks and/or mechanisms provide for channel
binding, such as the GSS-API and some GSS-API mechanisms, whereas
others may not, such as SASL (however, ongoing work is adding channel
binding support to SASL). Semantics may vary with respect to
negotiation, how the binding occurs, and handling of channel binding
failure (see below).
@@ -495,19 +495,19 @@
Work is ongoing [I-D.ietf-sasl-gs2] to specify how SASL, particularly
it's new bridge to the GSS-API, performs channel binding. SASL will
likely differ from the GSS-API in its handling of channel binding
failure (i.e., when there may be a MITM) in that channel binding
success/failure will only affect the negotiation of SASL security
-Williams Expires September 6, 2007 [Page 9]
+Williams Expires October 18, 2007 [Page 9]
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+Internet-Draft On Channel Bindings April 2007
layers. I.e., when channel binding succeeds SASL should select no
security layers, leaving session cryptographic protection to the
secure channel that has been bound to.
@@ -551,19 +551,19 @@
-Williams Expires September 6, 2007 [Page 10]
+Williams Expires October 18, 2007 [Page 10]
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+Internet-Draft On Channel Bindings April 2007
4. Channel bindings specifications
Channel bindings for various types of secure channels are not
described herein. Some channel bindings specifications can be found
in:
@@ -570,19 +570,21 @@
+--------------------+----------------------------------------------+
| Secure Channel | Reference |
| Type | |
+--------------------+----------------------------------------------+
| SSHv2 | [I-D.williams-sshv2-channel-bindings] |
| | |
| TLS | [I-D.altman-tls-channel-bindings] |
| | |
- | IPsec | There is no specification for this yet. We |
- | | expect that channel bindings for IPsec will |
- | | be of the non-unique variety. |
+ | IPsec | There is no specification for IPsec channel |
+ | | bindings yet, but the IETF Better Than |
+ | | Nothing Security (BTNS) WG is working to |
+ | | specify IPsec channels, and possibly IPsec |
+ | | channel bindings. |
+--------------------+----------------------------------------------+
4.1. Examples of unique channel bindings
The following text is not normative, but is here to show how one
might construct channel bindings for various types of secure
channels.
@@ -602,26 +604,26 @@
The following text is not normative, but is here to show how one
might construct channel bindings for various types of secure
channels.
For SSHv2 [RFC4251] the SSHv2 host public key, when present, should
suffice as it is used to sign the algorithm suite negotiation and
Diffie-Hellman key exchange; as long the client observes the host
public key that corresponds to the private host key that the server
- used then there cannot be a MITM in the SSHv2 connection. Note that
- not all SSHv2 key exchanges use host public keys, therefore this
-Williams Expires September 6, 2007 [Page 11]
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+Internet-Draft On Channel Bindings April 2007
+ used then there cannot be a MITM in the SSHv2 connection. Note that
+ not all SSHv2 key exchanges use host public keys, therefore this
channel bindings construction is not as useful as the one given in
Section 4.1 above.
For TLS [RFC4346]the server certificate should suffice for the same
reasons as above. Again, not all TLS cipher suites involve server
certificates, therfore the utility of this construction of channel
bindings is limited to scenarios where server certificates are
commonly used.
@@ -661,23 +663,21 @@
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-Williams Expires September 6, 2007 [Page 12]
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-
-
5. Uses of channel binding
Uses for channel binding identified so far:
o Delegating session cryptographic protection to layers where
hardware can reasonably be expected to support relevant
cryptographic protocols:
@@ -719,30 +719,30 @@
cleartext relative to this RDDP layer, or the RDDP implementation
must know how to implement cryptographic session protection protocols
used at the application layer.
There are a multitude of application layer cryptographic session
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+Internet-Draft On Channel Bindings April 2007
protection protocols available. It is not reasonable to expect the
NICs should support many such protocols. Further, some application
protocols may maintain many cryptographic session contexts per-
connection (for example, NFSv4 does). It is thought to be simpler to
- push the cryptographic session protection down the network stack, to
- IPsec, and yet be able to produce NICs that offload TCP/IP, ESP/AH,
- and DDP operations, than it would be to add support in the NIC for
- the many session cryptographic protection protocols in use in common
- applications at the application layer.
+ push the cryptographic session protection down the network stack (to
+ IPsec), and yet be able to produce NICs that offload other operations
+ (i.e. - TCP/IP, ESP/AH, and DDP), than it would be to add support in
+ the NIC for the many session cryptographic protection protocols in
+ use in common applications at the application layer.
The following figure shows how the various network layers are
related:
+---------------------+
| Application layer |<---+
| |<-+ | In cleartext, relative
+---------------------+ | | to each other.
@@ -775,19 +775,19 @@
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+Internet-Draft On Channel Bindings April 2007
6. Benefits of channel binding to secure channels
The use of channel binding to delegate session cryptographic
protection include:
o Performance improvements by avoiding double protection of
@@ -831,77 +831,189 @@
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+Internet-Draft On Channel Bindings April 2007
7. IANA Considerations
- There are no IANA considerations in this document.
+ The IANA is hereby requested to create a new registry for channel
+ bindings specifciations for various types of channels.
+ The purpose of this registry is not only to ensure uniqueness of
+ values used to name channel bindings, but also to provide a
+ definitive reference to technical specifications detailing each
+ channel binding available for use on the Internet.
+ There is no naming convention for channel bindings: any string
+ composed of US-ASCII alphanumeric characters, period ('.') and dash
+ ('-') will suffice.
+ The procedure detailed in Section 7.1 is to be used for registration
+ of a value naming a specific individual mechanism.
+ Comments may be included in the registry as discussed in Section 7.2
+ and may be changed as discussed in Section 7.3.
+7.1. Registration Procedure
+ Registration of a new channel binding requires expert review as
+ defined in BCP 26 [RFC2434].
+ Registration of a Channel binding is requested by filling in the
+ following template:
+ o Subject: Registration of channel binding X
+ o Channel binding unique prefix (name):
+ o Channel binding type: (One of "unique" or "end-point")
+ o Channel type: (E.g., TLS, IPsec, SSH, etc...)
+ o Published specification (recommended, optional):
+ o Description (optional if a specification is given; required if no
+ Published specification is specified):
+ o Intended usage: (One of COMMON, LIMITED USE, or OBSOLETE)
+ o Person and email address to contact for further information:
+ o Owner/Change controller name and email address:
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+ o Expert reviewer name and contact information: (leave blank)
+ o Note: (Any other information that the author deems relevant may be
+ added here.)
+ and sending it via electronic mail to a list to be determined [note:
+ an ietf.org list for this is needed, say, channel-binding@xxxxxxxx]
+ and carbon copying IANA at <iana@xxxxxxxx>. After allowing two weeks
+ for community input on the mailing list to be determined, an expert
+ will determine the appropriateness of the registration request and
+ either approve or disapprove the request with notice to the
+ requestor, the mailing list, and IANA.
+ If the expert approves registration, it adds her/his name to the
+ submitted registration.
+ The expert has the primary responsibility of making sure that channel
+ bindings for IETF specifications go through the IETF consensus
+ process and that prefixes are unique.
+ The review should focus on the appropriateness of the requested
+ channel binding for the proposed use, the appropriateness of the
+ proposed prefix and correctness of the channel binding type in the
+ registration. The scope of this request review may entail
+ consideration of relevant aspects of any provided technical
+ specification, such as their IANA Considerations section. However,
+ this review is narrowly focused on the appropriateness of the
+ requested registration and not on the overall soundness of any
+ provided technical specification.
+ Authors are encouraged to pursue community review by posting the
+ technical specification as an Internet-Draft and soliciting comment
+ by posting to appropriate IETF mailing lists.
+7.2. Comments on channel bindings Registrations
+ Comments on a registered Channel bindings should first be sent to the
+ "owner" of the channel bindings and to the channel binding mailing
+ list.
+ Submitters of comments may, after a reasonable attempt to contact the
+ owner, request IANA to attach their comment to the channel binding
+ type registration itself by sending mail to <iana@xxxxxxxx>. At
+ IANA's sole discretion, IANA may attach the comment to the Channel
+ binding's registration.
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+7.3. Change control
+ Once a Channel bindings registration has been published by IANA, the
+ author may request a change to its definition. The change request
+ follows the same procedure as the registration request.
+ The owner of a Channel bindings may pass responsibility for the
+ Channel bindings to another person or agency by informing IANA; this
+ can be done without discussion or review.
+ The IESG may reassign responsibility for a Channel bindings. The
+ most common case of this will be to enable changes to be made to
+ mechanisms where the author of the registration has died, has moved
+ out of contact, or is otherwise unable to make changes that are
+ important to the community.
+ Channel bindings registrations may not be deleted; mechanisms that
+ are no longer believed appropriate for use can be declared OBSOLETE
+ by a change to their "intended usage" field; such Channel bindings
+ will be clearly marked in the lists published by IANA.
+ The IESG is considered to be the owner of all channel bindings that
+ are on the IETF standards track.
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8. Security Considerations
Security considerations appear throughout this document. In
particular see Section 2.1.
When delegating session protection from one layer to another, one
will almost certainly be making some session security trade-offs,
such as using weaker cipher modes in one layer than might be used in
@@ -939,29 +1051,29 @@
Consider a user multiplexing protocol like NFSv4 using channel
binding to IPsec on a multi-user client. If another user can connect
directly to port 2049 (NFS) on some server using IPsec and merely
assert RPCSEC_GSS credential handles, then this user will be able to
impersonate any user authenticated by the client to the server. This
is because the new connection will have the same channel bindings as
the NFS client's! To prevent this the server must require that at
- least a hostbased client principal, and perhaps all the client's user
+ least a host-based client principal, and perhaps all the client's
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-Internet-Draft On Channel Bindings March 2007
+Internet-Draft On Channel Bindings April 2007
- principals, re-authenticate and perform channel binding before the
- server will allow the clients to assert RPCSEC_GSS context handles.
- Alternatively the protocol could: a) require that secure channels
- provide confidentiality protection, and b) that fast re-
+ user principals, re-authenticate and perform channel binding before
+ the server will allow the clients to assert RPCSEC_GSS context
+ handles. Alternatively the protocol could: a) require that secure
+ channels provide confidentiality protection, and b) that fast re-
authentication cookies be difficult to guess (e.g., large numbers
selected randomly).
In other contexts there may not be such problems, for example, in the
case of application protocols that don't multiplex users over a
single channel and where confidentiality protection is always used in
the secure channel.
@@ -999,19 +1111,19 @@
-Williams Expires September 6, 2007 [Page 18]
+Williams Expires October 18, 2007 [Page 20]
-Internet-Draft On Channel Bindings March 2007
+Internet-Draft On Channel Bindings April 2007
9. References
9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
@@ -1055,32 +1167,32 @@
[I-D.ietf-nfsv4-nfsdirect]
Callaghan, B. and T. Talpey, "NFS Direct Data Placement",
draft-ietf-nfsv4-nfsdirect-04 (work in progress),
October 2006.
-Williams Expires September 6, 2007 [Page 19]
+Williams Expires October 18, 2007 [Page 21]
-Internet-Draft On Channel Bindings March 2007
+Internet-Draft On Channel Bindings April 2007
[I-D.ietf-sasl-gs2]
Josefsson, S., "Using GSS-API Mechanisms in SASL: The GS2
Mechanism Family", draft-ietf-sasl-gs2-06 (work in
progress), February 2007.
[I-D.williams-sshv2-channel-bindings]
Williams, N., "Channel Bindings for Secure Shell
Channels", draft-williams-sshv2-channel-bindings-00 (work
in progress), July 2006.
- [Lapmson91]
+ [Lampson91]
Lampson, B., Abadi, M., Burrows, M., and E. Wobber,
"Authentication in Distributed Systems: Theory and
Practive", October 1991.
[RFC1964] Linn, J., "The Kerberos Version 5 GSS-API Mechanism",
RFC 1964, June 1996.
[RFC2401] Kent, S. and R. Atkinson, "Security Architecture for the
@@ -1111,19 +1223,19 @@
[RFC4251] Ylonen, T. and C. Lonvick, "The Secure Shell (SSH)
Protocol Architecture", RFC 4251, January 2006.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the
-Williams Expires September 6, 2007 [Page 20]
+Williams Expires October 18, 2007 [Page 22]
-Internet-Draft On Channel Bindings March 2007
+Internet-Draft On Channel Bindings April 2007
Internet Protocol", RFC 4301, December 2005.
[RFC4302] Kent, S., "IP Authentication Header", RFC 4302,
December 2005.
[RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)",
@@ -1167,19 +1279,19 @@
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+Williams Expires October 18, 2007 [Page 23]
-Internet-Draft On Channel Bindings March 2007
+Internet-Draft On Channel Bindings April 2007
Appendix A. Acknowledgments
Thanks to Mike Eisler for his work on the Channel Conjunction
Mechanism I-D and for bringing the problem to a head, Sam Hartman for
pointing out that channel binding provide a general solution to the
channel binding problem, Jeff Altman for his suggestion of using the
@@ -1223,19 +1335,19 @@
-Williams Expires September 6, 2007 [Page 22]
+Williams Expires October 18, 2007 [Page 24]
-Internet-Draft On Channel Bindings March 2007
+Internet-Draft On Channel Bindings April 2007
Author's Address
Nicolas Williams
Sun Microsystems
5300 Riata Trace Ct
Austin, TX 78727
@@ -1279,19 +1391,19 @@
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+Williams Expires October 18, 2007 [Page 25]
-Internet-Draft On Channel Bindings March 2007
+Internet-Draft On Channel Bindings April 2007
Full Copyright Statement
Copyright (C) The IETF Trust (2007).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
@@ -1335,10 +1447,10 @@
Funding for the RFC Editor function is provided by the IETF
Administrative Support Activity (IASA).
-Williams Expires September 6, 2007 [Page 24]
+Williams Expires October 18, 2007 [Page 26]
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