Internet Engineering Task Force C. Paasch
Internet-Draft Apple, Inc.
Intended status: Experimental A. Ford
Expires: November 28, 2016 Pexip
May 27, 2016
TLS Authentication for MPTCP
draft-paasch-mptcp-tls-authentication-00
Abstract
Multipath TCP (MPTCP), described in [4], is an extension to TCP to
provide the ability to simultaneously use multiple paths between
peers.
draft-paasch-mptcp-application-authentication specifies "application
layer authentication" for Multipath TCP, an alternatively negotiated
keying mechanism for MPTCP. This allows keying material to be
sourced from an application layer protocol in order to secure MP_JOIN
handshakes.
This document explains how to use the proposed application-layer
authentication extension with TLS [6], in order to leverage securely
exchanged keys for MPTCP security, whilst simultaneously freeing the
MPTCP token to be used as a channel for additional information.
Status of This Memo
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This Internet-Draft will expire on November 28, 2016.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Technical Implementation . . . . . . . . . . . . . . . . . . 3
3. Security Considerations . . . . . . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
5. References . . . . . . . . . . . . . . . . . . . . . . . . . 4
5.1. Normative References . . . . . . . . . . . . . . . . . . 4
5.2. Informative References . . . . . . . . . . . . . . . . . 4
1. Introduction
As described in draft-paasch-mptcp-application-authentication, the
use of "application-layer authentication" allows the Key used in
MPTCP authentication to be provided by the application layer, thus
permitting the use of existing secure communication channels for
exchanging keying material. Furthermore, this decouples the key from
the token and thus allows the token to be used for conveying
additional semantics, such as helping front-end proxies route traffic
to appropriate back-end servers.
TLS [6] provides a secure authentication channel between end hosts,
where keys are not transmitted in the clear. The protocol generates
a master secret for a connection, and a method is described in [3]
for exporting a key generated from this and other properties which
can then be used by the application layer. This document shows how
to use this exported key, along with the method in draft-paasch-
mptcp-application-authentication, for providing alternative keying
mechanisms for MPTCP.
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2. Technical Implementation
As described in draft-paasch-mptcp-application-authentication, the
initial MP_CAPABLE handshake will exchange an arbitrary token for
identifying an MPTCP connection. Whilst it is RECOMMENDED that the
token is hard to guess, it can be used to carry any data, such as
arbitrary routing information, and the security provided by the
application-layer security will mitigate any risks of an attacker
guessing tokens.
When an MPTCP end host wishes to open a new subflow, it will follow
the same exchange as described in [4], however the keying material
(Key-A and Key-B) will be derived from the TLS handshake, as
described in [3]. The "label" field MUST be "EXPORTER-MPTCP". The
length used in the key-derivation, following [3] is 16. Key-A are
the 64 most-significant bits, while Key-B are the 64 remaining bits.
This requires the key exchange to have completed before subflows can
be created. Other than the source of the keys, the exchange remains
the same. The MP_CAPABLE and MP_JOIN exchange therefore looks like
this:
Host A Host B
------------------------ ----------
Address A1 Address A2 Address B1
---------- ---------- ----------
| | |
| | SYN + MP_CAPABLE |
|--------------------------------------------->|
|<---------------------------------------------|
| SYN/ACK + MP_CAPABLE(Token-B) |
| | |
| ACK + MP_CAPABLE(Token-A, Token-B) |
|--------------------------------------------->|
| | |
| | SYN + MP_JOIN(Token-B, R-A) |
| |------------------------------->|
| |<-------------------------------|
| | SYN/ACK + MP_JOIN(HMAC-B, R-B) |
| | |
| | ACK + MP_JOIN(HMAC-A) |
| |------------------------------->|
| |<-------------------------------|
| | ACK |
HMAC-A = HMAC(Key=(Key-A+Key-B), Msg=(R-A+R-B))
HMAC-B = HMAC(Key=(Key-B+Key-A), Msg=(R-B+R-A))
Figure 1: Example Use of MPTCP Authentication
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3. Security Considerations
This draft relies on the security provided by TLS [6] and the key
export mechanism of [3] to provide additional security for the MPTCP
handshake mechanism. These changes remove lingering risks,
originally identified in [7], where an intercept of the initial MPTCP
handshake could allow session hijack.
4. IANA Considerations
IANA would be requested to add a value to the TLS Exporter Label
registry as described in [3]. The label is "EXPORTER-MPTCP".
5. References
5.1. Normative References
[1] Postel, J., "Transmission Control Protocol", STD 7, RFC
793, September 1981.
[2] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[3] Rescorla, E., "Keying Material Exporters for Transport
Layer Security (TLS)", RFC 5705, DOI 10.17487/RFC5705,
March 2010, <http://www.rfc-editor.org/info/rfc5705>.
[4] Ford, A., Raiciu, C., Handley, M., Bonaventure, O., and C.
Paasch, "TCP Extensions for Multipath Operation with
Multiple Addresses", draft-ietf-mptcp-rfc6824bis-05 (work
in progress), January 2016.
[5] National Institute of Science and Technology, "Secure Hash
Standard", Federal Information Processing Standard (FIPS)
180-3, October 2008,
<http://csrc.nist.gov/publications/fips/fips180-3/
fips180-3_final.pdf>.
5.2. Informative References
[6] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, DOI 10.17487/
RFC5246, August 2008,
<http://www.rfc-editor.org/info/rfc5246>.
[7] Ford, A., Raiciu, C., Handley, M., and O. Bonaventure,
"TCP Extensions for Multipath Operation with Multiple
Addresses", RFC 6824, January 2013.
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Authors' Addresses
Christoph Paasch
Apple, Inc.
Cupertino
US
EMail: cpaasch@apple.com
Alan Ford
Pexip
EMail: alan.ford@gmail.com
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