Internet Engineering Task Force I. Hajjeh
ESRGroups
M. Badra
LIMOS Laboratory
Expires: November 2007 June, 2007
Credential Protection Ciphersuites for Transport Layer Security
<draft-hajjeh-tls-identity-protection-01.txt>
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Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
TLS defines several ciphersuites providing authentication, data
protection and session key exchange between two communicating
entities. Some of these ciphersuites are used for completely
anonymous key exchange, in which neither party is authenticated.
However, they are vulnerable to man-in-the-middle attacks and are
therefore deprecated.
This document defines a set of ciphersuites to add client credential
protection to the Transport Layer Security (TLS) protocol.
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1. Introduction
TLS is the most deployed security protocol for securing exchanges.
It provides end-to-end secure communications between two entities
with authentication and data protection.
TLS supports three authentication modes: authentication of both
parties, only server-side authentication, and anonymous key
exchange. For each mode, TLS specifies a set of ciphersuites.
However, anonymous ciphersuites are strongly discouraged because
they cannot prevent man-in-the-middle attacks.
Client credential protection may be established by changing the
order of the messages that the client sends after receiving
ServerHelloDone [CORELLA]. This is done by sending the
ChangeCipherSpec message before the Certificate and the
CertificateVerify messages and after the ClientKeyExchange message.
However, it requires a major change to TLS machine state as long as
a new TLS version.
Client credential protection may also be done through a DHE exchange
before establishing an ordinary handshake with identity information
[RESCORLA]. This wouldn't however be secure enough against active
attackers, which will be able to disclose the client's credentials
and wouldn't be favorable for some environments (e.g. mobile), due
to the additional cryptographic computations.
Client credential protection may be also possible, assuming that the
client permits renegotiation after the first server authentication.
However, this requires more cryptographic computations and augments
significantly the number of rounds trips.
Client credential protection may as well be realized by exchanging a
TLS extension that negotiates the symmetric encryption algorithm to
be used for client certificate encrypting/decrypting [EAPTLSIP].
This solution may suffer from interoperability issues related to TLS
Extensions, TLS 1.0 and TLS 1.1 implementations, as described in
[INTEROP].
This document defines a set of ciphersuites to add client credential
protection to TLS protocol. Client credential protection is provided
by symmetrically encrypting the client certificate with a key
derived from the SecurityParameters.master_secret,
SecurityParameters.server_random and
SecurityParameters.client_random. The symmetric encryption algorithm
is set to the cipher algorithm of the ServerHello.cipher_suite.
1.2. Requirements language
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The key words "MUST", "MUST NOT" and "MAY" in this document are to
be interpreted as described in RFC-2119.
2. TLS credential protection overview
This document specifies a set of ciphersuites for TLS. These
ciphersuites reuse existing key exchange algorithms that require
based-certificates authentication, and reuse also existing MAC,
stream and bloc ciphers algorithms from [TLS] and [TLSCTR],
[TLSECC], [TLSAES] and [TLSCAM]. Their names include the text "CP"
to refer to the client credential protection. An example is shown
below.
CipherSuite Key Exchange Cipher Hash
TLS_CP_RSA_EXPORT_WITH_RC4_40_MD5 RSA RC4_40 MD5
TLS_CP_DHE_DSS_WITH_AES_128_CBC_SHA DHE AES_128_CBC SHA
If the client has not a certificate with a type appropriate for one
of the supported cipher key exchange algorithms or if the client
will not be able to send such a certificate, it MUST NOT include any
ciphersuite with client credential protection in the
ClientHello.cipher_suites.
If the server selects a ciphersuite with client credential
protection, the server MUST request a certificate from the client.
If the server selects one of the ciphersuites defined in this
document, the client MUST encrypt the Certificate and the
CertificateVerify messages using the symmetric algorithm selected by
the server from the list in ClientHello.cipher_suites and a key
derived from the SecurityParameters.master_secret. This key is the
same key used to encrypt data written by the client.
If a stream cipher encryption algorithm has been selected, the
client symmetrically encrypts Certificate and CertificateVerify
messages without any padding byte.
If a block cipher encryption algorithm has been selected, the client
uses an explicit IV and adds padding value to force the length of
the plaintext to be an integral multiple of the block cipher's block
length, as it is described in section 6.2.3.2 of [TLS1.1].
For DHE key exchange algorithm, the client always sends the
ClientKeyExchange message conveying its ephemeral DH public key Yc.
For ECDHE key exchange algorithm, the client always sends the
ClientKeyExchange message conveying its ephemeral ECDH public key
Yc.
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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.
Implementations of this document MUST send ClientKeyExchange message
but always carrying the client Yc, whatever the PublicValueEncoding
is implicit or explicit. Note that it is possible to correlate
sessions by the same client when DH or ECDH are in use.
Client Server
ClientHello -------->
ServerHello
Certificate
ServerKeyExchange*
CertificateRequest
<-------- ServerHelloDone
{Certificate}
ClientKeyExchange
{CertificateVerify}
[ChangeCipherSpec]
Finished -------->
[ChangeCipherSpec]
<-------- Finished
Application Data <-------> Application Data
* Indicates optional or situation-dependent messages that are not
always sent.
{} Indicates messages that are symmetrically encrypted.
The ciphersuites in Section 3 (CP_RSA Key Exchange Algorithm) use
RSA based certificates to mutually authenticate a RSA exchange with
the client credential protection.
The ciphersuites in Section 4 (CP_DHE and CP_DH Key Exchange
Algorithm) use DHE_RSA, DH_RSA, DHE_DSS or DH_DSS to mutually
authenticate a (Ephemeral) Diffie-Hellman exchange.
The ciphersuites in Section 5 (CP_ECDH and CP_ECDHE Key Exchange
Algorithms) use ECDH_ECDSA, ECDHE_ECDSA, ECDH_RSA or ECDHE_RSA to
mutually authenticate a (Ephemeral) EC Diffie-Hellman exchange.
3. CP_RSA Key Exchange Algorithm
This section defines additional ciphersuites that use RSA based
certificates to authenticate a RSA exchange. These ciphersuites give
client credential protection.
CipherSuite Key Exchange Cipher Hash
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TLS_CP_RSA_EXPORT_WITH_RC4_40_MD5 RSA RC4_40 MD5
TLS_CP_RSA_WITH_RC4_128_MD5 RSA RC4_128 MD5
TLS_CP_RSA_WITH_RC4_128_SHA RSA RC4_128 SHA
TLS_CP_RSA_EXPORT_WITH_RC2_CBC_40_MD5 RSA RC2_CBC_40 MD5
TLS_CP_RSA_WITH_IDEA_CBC_SHA RSA IDEA_CBC SHA
TLS_CP_RSA_EXPORT_WITH_DES40_CBC_SHA RSA DES40_CBC_ SHA
TLS_CP_RSA_WITH_DES_CBC_SHA RSA DES_CBC SHA
TLS_CP_RSA_WITH_3DES_EDE_CBC_SHA RSA 3DES_EDE SHA
TLS_CP_RSA_WITH_AES_128_CBC_SHA RSA AES_128_CBC SHA
TLS_CP_RSA_WITH_AES_256_CBC_SHA RSA AES_256_CBC SHA
TLS_CP_RSA_WITH_AES_128_CTR_SHA RSA AES_128_CTR SHA
TLS_CP_RSA_WITH_CAMELLIA_128_CBC_SHA RSA CAMELLIA_128_CBC SHA
TLS_CP_RSA_WITH_AES_256_CTR_SHA RSA AES_256_CTR SHA
TLS_CP_RSA_WITH_CAMELLIA_256_CBC_SHA RSA CAMELLIA_256_CBC SHA
4. CP_DHE and CP_DH Key Exchange Algorithms
This section defines additional ciphersuites that use DH and DHE as
key exchange algorithms, with RSA or DSS based certificates to
authenticate a (Ephemeral) Diffie-Hellman exchange. These
ciphersuites give client credential protection.
CipherSuite Key Exchange Cipher Hash
TLS_CP_DHE_DSS_WITH_DES_CBC_SHA DHE DES_CBC SHA
TLS_CP_DHE_DSS_WITH_3DES_EDE_CBC_SHA DHE 3DES_EDE_CBC SHA
TLS_CP_DHE_RSA_WITH_DES_CBC_SHA DHE DES_CBC SHA
TLS_CP_DHE_RSA_WITH_3DES_EDE_CBC_SHA DHE 3DES_EDE_CBC SHA
TLS_CP_DHE_DSS_WITH_AES_128_CBC_SHA DHE AES_128_CBC SHA
TLS_CP_DHE_RSA_WITH_AES_128_CBC_SHA DHE AES_128_CBC SHA
TLS_CP_DHE_DSS_WITH_AES_256_CBC_SHA DHE AES_256_CBC SHA
TLS_CP_DHE_RSA_WITH_AES_256_CBC_SHA DHE AES_256_CBC SHA
TLS_CP_DHE_DSS_WITH_CAMELLIA_128_CBC_SHA DHE CAMELLIA_128_CBC SHA
TLS_CP_DHE_RSA_WITH_CAMELLIA_128_CBC_SHA DHE CAMELLIA_128_CBC SHA
TLS_CP_DHE_DSS_WITH_CAMELLIA_256_CBC_SHA DHE CAMELLIA_256_CBC SHA
TLS_CP_DHE_RSA_WITH_CAMELLIA_256_CBC_SHA DHE CAMELLIA_256_CBC SHA
TLS_CP_DHE_DSS_WITH_AES_128_CTR_SHA DHE AES_128_CTR SHA
TLS_CP_DHE_RSA_WITH_AES_128_CTR_SHA DHE AES_128_CTR SHA
TLS_CP_DHE_DSS_WITH_AES_256_CTR_SHA DHE AES_256_CTR SHA
TLS_CP_DHE_RSA_WITH_AES_256_CTR_SHA DHE AES_256_CTR SHA
TLS_CP_DH_DSS_WITH_DES_CBC_SHA DH DES_CBC SHA
TLS_CP_DH_DSS_WITH_3DES_EDE_CBC_SHA DH 3DES_EDE_CBC SHA
TLS_CP_DH_RSA_WITH_DES_CBC_SHA DH DES_CBC SHA
TLS_CP_DH_RSA_WITH_3DES_EDE_CBC_SHA DH 3DES_EDE_CBC SHA
TLS_CP_DH_DSS_WITH_AES_128_CBC_SHA DH AES_128_CBC SHA
TLS_CP_DH_RSA_WITH_AES_128_CBC_SHA DH AES_128_CBC SHA
TLS_CP_DH_DSS_WITH_AES_256_CBC_SHA DH AES_256_CBC SHA
TLS_CP_DH_RSA_WITH_AES_256_CBC_SHA DH AES_256_CBC SHA
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5. CP_ECDH and CP_ECDHE Key Exchange Algorithm
This section defines additional ciphersuites that use ECDH and ECDHE
as key exchange algorithms, with RSA or ECDSA based certificates to
authenticate a (Ephemeral) ECDH exchange. These ciphersuites give
client credential protection.
CipherSuite Key Exchange Cipher Hash
TLS_CP_ECDH_ECDSA_WITH_RC4_128_SHA ECDH RC4_128_ SHA
TLS_CP_ECDH_ECDSA_WITH_3DES_EDE_CBC_SHA ECDH 3DES_EDE_CBC SHA
TLS_CP_ECDH_ECDSA_WITH_AES_128_CBC_SHA ECDH AES_128_CBC SHA
TLS_CP_ECDH_ECDSA_WITH_AES_256_CBC_SHA ECDHE AES_256_CBC SHA
TLS_CP_ECDHE_ECDSA_WITH_RC4_128_SHA ECDHE RC4_128 SHA
TLS_CP_ECDHE_ECDSA_WITH_3DES_EDE_CBC_SHA ECDHE 3DES_EDE_CBC SHA
TLS_CP_ECDHE_ECDSA_WITH_AES_128_CBC_SHA ECDHE AES_128_CBC SHA
TLS_CP_ECDHE_ECDSA_WITH_AES_256_CBC_SHA ECDHE AES_256_CBC SHA
TLS_CP_ECDH_RSA_WITH_RC4_128_SHA ECDH RC4_128 SHA
TLS_CP_ECDH_RSA_WITH_3DES_EDE_CBC_SHA ECDH 3DES_EDE_CBC SHA
TLS_CP_ECDH_RSA_WITH_AES_128_CBC_SHA ECDH AES_256_CBC SHA
TLS_CP_ECDH_RSA_WITH_AES_256_CBC_SHA ECDH AES_256_CBC SHA
TLS_CP_ECDHE_RSA_WITH_RC4_128_SHA ECDHE RC4_128 SHA
TLS_CP_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA ECDHE 3DES_EDE_CBC SHA
TLS_CP_ECDHE_RSA_WITH_AES_128_CBC_SHA ECDHE AES_256_CBC SHA
TLS_CP_ECDHE_RSA_WITH_AES_256_CBC_SHA ECDHE AES_256_CBC SHA
6. Security Considerations
The security considerations described throughout [TLS], [DTLS],
[TLS1.1], [TLSAES], [TLSECC] and [TLSAES] apply here as well.
7. IANA Considerations
This section provides guidance to the IANA regarding registration of
values related to the credential protection ciphersuites.
CipherSuite TLS_CP_RSA_EXPORT_WITH_RC4_40_MD5 = { 0xXX,0xXX };
CipherSuite TLS_CP_RSA_WITH_RC4_128_MD5 = { 0xXX,0xXX };
CipherSuite TLS_CP_RSA_WITH_RC4_128_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_RSA_EXPORT_WITH_RC2_CBC_40_MD5 = { 0xXX,0xXX };
CipherSuite TLS_CP_RSA_WITH_IDEA_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_RSA_EXPORT_WITH_DES40_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_RSA_WITH_DES_CBC_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_CTR_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_RSA_WITH_CAMELLIA_128_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_RSA_WITH_AES_256_CTR_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_RSA_WITH_CAMELLIA_256_CBC_SHA = { 0xXX,0xXX };
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CipherSuite TLS_CP_DHE_DSS_WITH_DES_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_DHE_DSS_WITH_3DES_EDE_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_DHE_RSA_WITH_DES_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_DHE_RSA_WITH_3DES_EDE_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_DHE_DSS_WITH_AES_128_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_DHE_RSA_WITH_AES_128_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_DHE_DSS_WITH_AES_256_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_DHE_RSA_WITH_AES_256_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_DHE_DSS_WITH_CAMELLIA_128_CBC_SHA= { 0xXX,0xXX };
CipherSuite TLS_CP_DHE_RSA_WITH_CAMELLIA_128_CBC_SHA= { 0xXX,0xXX };
CipherSuite TLS_CP_DHE_DSS_WITH_CAMELLIA_256_CBC_SHA= { 0xXX,0xXX };
CipherSuite TLS_CP_DHE_RSA_WITH_CAMELLIA_256_CBC_SHA= { 0xXX,0xXX };
CipherSuite TLS_CP_DHE_DSS_WITH_AES_128_CTR_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_DHE_RSA_WITH_AES_128_CTR_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_DHE_DSS_WITH_AES_256_CTR_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_DHE_RSA_WITH_AES_256_CTR_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_DH_DSS_WITH_DES_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_DH_DSS_WITH_3DES_EDE_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_DH_RSA_WITH_DES_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_DH_RSA_WITH_3DES_EDE_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_DH_DSS_WITH_AES_128_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_DH_RSA_WITH_AES_128_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_DH_DSS_WITH_AES_256_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_DH_RSA_WITH_AES_256_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_ECDH_ECDSA_WITH_RC4_128_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_ECDH_ECDSA_WITH_3DES_EDE_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_ECDH_ECDSA_WITH_AES_128_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_ECDH_ECDSA_WITH_AES_256_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_ECDHE_ECDSA_WITH_RC4_128_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_ECDHE_ECDSA_WITH_3DES_EDE_CBC_SHA= { 0xXX,0xXX };
CipherSuite TLS_CP_ECDHE_ECDSA_WITH_AES_128_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_ECDHE_ECDSA_WITH_AES_256_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_ECDH_RSA_WITH_RC4_128_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_ECDH_RSA_WITH_3DES_EDE_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_ECDH_RSA_WITH_AES_128_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_ECDH_RSA_WITH_AES_256_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_ECDHE_RSA_WITH_RC4_128_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_ECDHE_RSA_WITH_AES_128_CBC_SHA = { 0xXX,0xXX };
CipherSuite TLS_CP_ECDHE_RSA_WITH_AES_256_CBC_SHA = { 0xXX,0xXX };
Note: For implementation and deployment facilities, it is helpful to
reserve a specific registry sub-range (minor, major) for credential
protection ciphersuites.
8. References
8.1. Normative References
[TLS] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",
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RFC 2246, January 1999.
[TLS1.1] Dierks, T. and E. Rescorla, "The TLS Protocol Version
1.1", RFC 4346, April 2005.
[DTLS] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security", RFC 4347, April 2006.
[TLSCAM] Moriai, S., Kato, A., Kanda M., "Addition of Camellia
Cipher Suites to Transport Layer Security (TLS)",
RFC 4132, July 2005.
[TLSAES] Chown, P., "Advanced Encryption Standard (AES)
Ciphersuites for Transport Layer Security (TLS)",
RFC 3268, June 2002.
[TLSECC] Blake-Wilson, S., Bolyard, N., Gupta, V., Hawk, C.,
Moeller, B., "Elliptic Curve Cryptography (ECC) Cipher
Suites for Transport Layer Security (TLS)", RFC 4492, May
2006
[TLSCTR] Modadugu, N. and E. Rescorla, "AES Counter Mode Cipher
Suites for TLS and DTLS", draft-ietf-tls-ctr-01.txt (work
8.1. Informative References
[RESCORLA] Rescorla, E., "SSL and TLS: Designing and Building Secure
Systems", Addison-Wesley, March 2001.
[CORELLA] Corella, F., "adding client identity protection to TLS",
message on ietf-tls@lists.certicom.com mailing list,
http://www.imc.org/ietf-tls/mail-archive/msg02004.html,
August 2000.
[INTEROP] Pettersen, Y., "Clientside interoperability
experiences for the SSL and TLS protocols", draft-ietf-
tls-interoperability-00 (work in progress), October 2006.
in progress), June 2006.
[EAPTLSIP] Urien, P. and M. Badra, "Identity Protection within EAP-
TLS",
draft-urien-badra-eap-tls-identity-protection-01.txt
(work in progress), October 2006.
Author's Addresses
Ibrahim Hajjeh
ESRGroups, Security WG
France Email: Ibrahim.Hajjeh@esrgroups.org
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Mohamad Badra
LIMOS Laboratory - UMR (6158), CNRS
France Email: badra@isima.fr
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