Internet DRAFT - draft-badra-tls-ciphersuite-identity-protection
draft-badra-tls-ciphersuite-identity-protection
TLS Working Group M. Badra
Internet-Draft DU
Intended status: Standards Track I. Hajjeh
Expires: September 28, 2012 INEOVATION
March 27, 2012
Credential Protection Ciphersuites for Transport Layer Security (TLS)
draft-badra-tls-ciphersuite-identity-protection-00
Abstract
This document defines a set of cipher suites to add client credential
protection to the Transport Layer Security (TLS) protocol. By
negotiating one of those ciphersuites, the TLS clients will be able
to determine for themselves when, how, to what extent and for what
purpose information about them is communicated to others. The
ciphersuites defined in this document can be used only when public
key certificates are used in the client authentication process.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on September 28, 2012.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
Badra & Hajjeh Expires September 28, 2012 [Page 1]
Internet-Draft Credential Protection Ciphersuites March 2012
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions Used in This Document . . . . . . . . . . . . . 3
2. The Credential Protection Ciphersuites . . . . . . . . . . . . 3
3. Security Considerations . . . . . . . . . . . . . . . . . . . . 4
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
6.1. Normative References . . . . . . . . . . . . . . . . . . . 7
6.2. Informative References . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
Badra & Hajjeh Expires September 28, 2012 [Page 2]
Internet-Draft Credential Protection Ciphersuites March 2012
1. Introduction
TLS client credential protection may be done by a signalling
mechanism based on a set of cipher suites as described in [Hajjeh].
This document specifies a set of cipher suites to add client
credential protection to the TLS protocol. These cipher suites reuse
existing key exchange algorithms with certificate-based
authentication, and reuse existing cipher and MAC algorithms from
[RFC5246], [RFC5288], and [RFC5932].
1.1. Conventions Used in This Document
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].
2. The Credential Protection Ciphersuites
The name of cipher suites defined in this document includes the text
"CP" to refer to the client credential protection. An example is
shown below.
CipherSuite Key Exchange Cipher Hash
TLS_CP_RSA_WITH_AES_128_CBC_SHA RSA AES_128_CBC SHA1
The client indicates its willingness to protect its credentials by
including one or more ciphersuites described here in the
ClientHello.cipher_suites. These cipher suites MUST be placed at the
top of the cipher suite list.
When one of the cipher suites defined through this document is
negotiated, the client MUST send the ChangeCipherSpec message before
the Certificate and the CertificateVerify messages and after the
ClientKeyExchange message.
Badra & Hajjeh Expires September 28, 2012 [Page 3]
Internet-Draft Credential Protection Ciphersuites March 2012
Client Server
ClientHello -------->
ServerHello
Certificate
CertificateRequest
<-------- ServerHelloDone
ClientKeyExchange
ChangeCipherSpec
ChangeCipherSpec
<-------- Finished
Certificate
CertificateVerify
Finished -------->
Application Data <-------> Application Data
If no certificates are available, the client MUST NOT include any
credential protection cipher suite in the ClientHello.cipher_suites.
If the server selects a cipher suite with client credential
protection, the server MUST send a certificate appropriate for the
negotiated cipher suite's key exchange algorithm, and MUST request a
certificate from the client. If the server, agreeing on using a
credential protection cipher suite, does not receive a client
certificate in response to the subsequent certificate request, then
it MUST abort the session by sending a fatal handshake failure alert.
The client certificate MUST be appropriate for the negotiated cipher
suite's key exchange algorithm, and any negotiated extensions.
Current TLS specifications note that if the client certificate
already contains a suitable DH or ECDH public key, then Yc is
implicit and does not need to be sent again and consequently, the
client key exchange message will be sent, but it MUST be empty. Even
if the client key exchange message is used to carry the Yc, using the
same Yc will allow traceability. Consequently, static Diffie-Hellman
SHOULD NOT be used with this document.
3. Security Considerations
The security considerations described throughout [RFC5246] apply here
as well.
Active attackers can modify messages and insert, remove, or replace
cipher suites. An attacker could attempt to get the peers to
negotiate a cipher suite that does not provide client credential
protection. However, actives attacks and eavesdroppers are
Badra & Hajjeh Expires September 28, 2012 [Page 4]
Internet-Draft Credential Protection Ciphersuites March 2012
impossible here because the client MUST terminate the connection
immediately upon failure to receive a valid Finished from the server
without sending the Certificate and CertificateVerify messages. Such
clients MUST generate a fatal "decrypt_error" alert prior to
terminating the connection.
In order for the client to be protected against man-in-the-middle
attacks, the client SHOULD verify that the server provided a valid
certificate and that the received public key belongs to the server.
Because the question of whether this is the correct certificate is
outside of TLS, applications that do implement credential protection
cipher suites SHOULD enable the client to carefully examine the
certificate presented by the server to determine if it meets its
expectations. Particularly, the client MUST check its understanding
of the server hostname against the server's identity as presented in
the server Certificate message.
In the absence of an application profile specifying otherwise, the
matching is performed according to the following rules:
o The client MUST use the server hostname it used to open the
connection (or the hostname specified in the TLS "server_name"
extension [RFC6066]) as the value to compare against the server
name as expressed in the server certificate. The client MUST NOT
use any form of the server hostname derived from an insecure
remote source (e.g., insecure DNS lookup). CNAME canonicalization
is not done.
o If a subjectAltName extension of type dNSName is present in the
certificate, it MUST be used as the source of the server's
identity.
o Matching is case-insensitive.
o A "*" wildcard character MAY be used as the left-most name
component in the certificate. For example, *.example.com would
match a.example.com, foo.example.com, etc., but would not match
example.com.
o If the certificate contains multiple names (e.g., more than one
dNSName field), then a match with any one of the fields is
considered acceptable.
If the match fails, the client MUST either ask for explicit user
confirmation or terminate the connection and indicate the server's
identity is suspect.
Badra & Hajjeh Expires September 28, 2012 [Page 5]
Internet-Draft Credential Protection Ciphersuites March 2012
Additionally, the client MUST verify the binding between the identity
of the server to which it connects and the public key presented by
this server. The client SHOULD implement the algorithm in Section 6
of [RFC5280] for general certificate validation, but MAY supplement
that algorithm with other validation methods that achieve equivalent
levels of verification (such as comparing the server certificate
against a local store of already-verified certificates and identity
bindings).
If the client has external information as to the expected identity of
the server, the hostname check MAY be omitted.
It will depend on the application whether or not the server will have
external knowledge of what the client's identity ought to be and what
degree of assurance it needs to obtain of it. In any case, the
server typically will have to check that the client has a valid
certificate chained to an application-specific trust anchor it is
configured with, following the rules of [RFC5280], before it
successfully finishes the TLS handshake.
One widely accepted layering principle is to decouple service
authorization from client authentication on access. We therefore
recommend that authorization decisions be performed and communicated
at the application layer after the TLS handshake has been completed.
4. IANA Considerations
This section provides guidance to the IANA regarding registration of
values related to the credential protection cipher suites.
CipherSuite TLS_CP_RSA_WITH_RC4_128_MD5 = { 0xXX,0xXX };
CipherSuite TLS_CP_RSA_WITH_RC4_128_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_RSA_WITH_3DES_EDE_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_RSA_WITH_AES_128_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_RSA_WITH_AES_256_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_RSA_WITH_AES_128_CBC_SHA256 = { 0xXX,0xXX };
CipherSuite TLS_CP_RSA_WITH_AES_256_CBC_SHA256 = { 0xXX,0xXX };
CipherSuite TLS_CP_RSA_WITH_CAMELLIA_128_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_RSA_WITH_CAMELLIA_256_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_RSA_WITH_CAMELLIA_128_CBC_SHA256 = { 0xXX,0xXX };
CipherSuite TLS_CP_RSA_WITH_CAMELLIA_256_CBC_SHA256 = { 0xXX,0xXX };
CipherSuite TLS_CP_RSA_WITH_CAMELLIA_128_GCM_SHA256 = { 0xXX,0xXX };
CipherSuite TLS_CP_RSA_WITH_CAMELLIA_256_GCM_SHA384 = { 0xXX,0xXX };
CipherSuite TLS_CP_RSA_WITH_ARIA_128_CBC_SHA256 = { 0xXX,0xXX };
CipherSuite TLS_CP_RSA_WITH_ARIA_256_CBC_SHA384 = { 0xXX,0xXX };
CipherSuite TLS_CP_RSA_WITH_ARIA_128_GCM_SHA256 = { 0xXX,0xXX };
Badra & Hajjeh Expires September 28, 2012 [Page 6]
Internet-Draft Credential Protection Ciphersuites March 2012
CipherSuite TLS_CP_RSA_WITH_ARIA_256_GCM_SHA384 = { 0xXX,0xXX };
5. Acknowledgements
In August 2000, Francisco Corella proposed adding client credential
protection to TLS by changing the order of TLS messages.
This document borrows text from [Hajjeh].
6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC4492] Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C., and B.
Moeller, "Elliptic Curve Cryptography (ECC) Cipher Suites
for Transport Layer Security (TLS)", RFC 4492, May 2006.
[RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.2", RFC 5246, August 2008.
[RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,
Housley, R., and W. Polk, "Internet X.509 Public Key
Infrastructure Certificate and Certificate Revocation List
(CRL) Profile", RFC 5280, May 2008.
[RFC5288] Salowey, J., Choudhury, A., and D. McGrew, "AES Galois
Counter Mode (GCM) Cipher Suites for TLS", RFC 5288,
August 2008.
[RFC5932] Kato, A., Kanda, M., and S. Kanno, "Camellia Cipher Suites
for TLS", RFC 5932, June 2010.
6.2. Informative References
[I-D.hajjeh-tls-identity-protection]
Hajjeh, I. and M. Badra, "Credential Protection
Ciphersuites for Transport Layer Security (TLS)",
draft-hajjeh-tls-identity-protection-09 (work in
progress), November 2009.
Badra & Hajjeh Expires September 28, 2012 [Page 7]
Internet-Draft Credential Protection Ciphersuites March 2012
Authors' Addresses
Mohamad Badra
DU
Email: mbadra@gmail.com
Ibrahim Hajjeh
INEOVATION
Email: ibrahim.hajjeh@ineovation.com
Badra & Hajjeh Expires September 28, 2012 [Page 8]