draft-ietf-kitten-gssapi-channel-bindings-01.txt   draft-ietf-kitten-gssapi-channel-bindings-02.txt 
KITTEN WG N. Williams KITTEN WG N. Williams
Internet-Draft Sun Internet-Draft Sun
Expires: April 19, 2006 October 16, 2005 Expires: December 28, 2006 June 26, 2006
Clarifications and Extensions to the GSS-API for the Use of Channel Clarifications and Extensions to the GSS-API for the Use of Channel
Bindings Bindings
draft-ietf-kitten-gssapi-channel-bindings-01.txt draft-ietf-kitten-gssapi-channel-bindings-02.txt
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Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2005). Copyright (C) The Internet Society (2006).
Abstract Abstract
This document clarifies and generalizes the GSS-API "channel This document clarifies and generalizes the GSS-API "channel
bindings" facility. This document also specifies the format of the bindings" facility. This document also specifies the format of the
various types of channel bindings. various types of channel bindings.
Table of Contents Table of Contents
1. Conventions used in this document . . . . . . . . . . . . . . 3 1. Conventions used in this document . . . . . . . . . . . . . . 3
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4. Channel Bindings for SSHv2 . . . . . . . . . . . . . . . . . . 6 4. Channel Bindings for SSHv2 . . . . . . . . . . . . . . . . . . 6
4.1. GSS_Make_sshv2_channel_bindings() . . . . . . . . . . . . 6 4.1. GSS_Make_sshv2_channel_bindings() . . . . . . . . . . . . 6
4.1.1. C-Bindings . . . . . . . . . . . . . . . . . . . . . . 7 4.1.1. C-Bindings . . . . . . . . . . . . . . . . . . . . . . 7
5. Channel Bindings for TLS . . . . . . . . . . . . . . . . . . . 8 5. Channel Bindings for TLS . . . . . . . . . . . . . . . . . . . 8
5.1. GSS_Make_tls_channel_bindings() . . . . . . . . . . . . . 8 5.1. GSS_Make_tls_channel_bindings() . . . . . . . . . . . . . 8
5.1.1. C-Bindings . . . . . . . . . . . . . . . . . . . . . . 9 5.1.1. C-Bindings . . . . . . . . . . . . . . . . . . . . . . 9
6. Channel Bindings for IPsec . . . . . . . . . . . . . . . . . . 10 6. Channel Bindings for IPsec . . . . . . . . . . . . . . . . . . 10
6.1. GSS_Make_ipsec_channel_bindings() . . . . . . . . . . . . 10 6.1. GSS_Make_ipsec_channel_bindings() . . . . . . . . . . . . 10
6.1.1. C-Bindings . . . . . . . . . . . . . . . . . . . . . . 11 6.1.1. C-Bindings . . . . . . . . . . . . . . . . . . . . . . 11
7. Security Considerations . . . . . . . . . . . . . . . . . . . 12 7. Security Considerations . . . . . . . . . . . . . . . . . . . 12
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 8. Normative . . . . . . . . . . . . . . . . . . . . . . . . . . 12
8.1. Normative . . . . . . . . . . . . . . . . . . . . . . . . 13 Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 13
8.2. Informative . . . . . . . . . . . . . . . . . . . . . . . 13 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 14
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 14 Intellectual Property and Copyright Statements . . . . . . . . . . 15
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 15
Intellectual Property and Copyright Statements . . . . . . . . . . 16
1. Conventions used in this document 1. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
2. Introduction 2. Introduction
The concept of "channel bindings" and the abstract construction of The concept of "channel bindings" and the abstract construction of
channel bindings for several types of channels are described in channel bindings for several types of channels are described in
[CHANNEL-BINDINGS] [I-D.ietf-nfsv4-channel-bindings]
To actually use channel bindings in GSS-API aplications additional To actually use channel bindings in GSS-API aplications additional
details are required that are given below. details are required that are given below.
First the structure given to channel bindings data in [RFC2744] is First the structure given to channel bindings data in [RFC2744] is
generalized to all of the GSS-API, not just its C-Bindings. generalized to all of the GSS-API, not just its C-Bindings.
Then the actual construction of channel bindings to SSHv2, TLS and Then the actual construction of channel bindings to SSHv2, TLS and
IPsec channels is given. IPsec channels is given.
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application-data OCTET STRING, application-data OCTET STRING,
} }
The values for the address fields are described in [RFC2744]. The values for the address fields are described in [RFC2744].
Language-specific bindings of the GSS-API should specify a language- Language-specific bindings of the GSS-API should specify a language-
specific formulation of this structure. specific formulation of this structure.
3.1. Proper Mechanism Use of Channel Bindings 3.1. Proper Mechanism Use of Channel Bindings
As described in [CHANNEL-BINDINGS], GSS mechanisms should exchange As described in [I-D.ietf-nfsv4-channel-bindings], GSS mechanisms
integrity protected proofs of channel bindings, where the proof is should exchange integrity protected proofs of channel bindings, where
obtained by running a strong hash of the channel bindings data the proof is obtained by running a strong hash of the channel
(encoded as per some mechanism-specific, such as in [RFC1964]) and a bindings data (encoded as per some mechanism-specific, such as in
binary value to represent the initiator->acceptor, and opposite, [RFC1964]) and a binary value to represent the initiator->acceptor,
direction. and opposite, direction.
The encoding of channel bindings used in [RFC1964], with the addition The encoding of channel bindings used in [RFC1964], with the addition
of a binary value as described above, and the substitution of SHA-1 of a binary value as described above, and the substitution of
for MD5 is a reasonable, generic encoding of GSS-CHANNEL-BINDINGS stronger hash functions (or even the identity function) for MD5 is a
that any future GSS mechanisms can use. reasonable, generic encoding of GSS-CHANNEL-BINDINGS that any future
GSS mechanisms can use.
4. Channel Bindings for SSHv2 4. Channel Bindings for SSHv2
The SSHv2 channel bindings are constructed as an octet string for the The SSHv2 channel bindings are constructed as an octet string for the
'application-data' field of the channel bindings by concatenating the 'application-data' field of the channel bindings by concatenating the
following values and in this order: following values and in this order:
1. The ASCII string "GSS SSHv2 CB:" 1. The ASCII string "GSS SSHv2 CB:"
2. The SSHv2 session ID 2. Four octet network byte order length of the SSHv2 session ID
3. Any additional application-provided data, encoded as the DER 3. The SSHv2 session ID
4. Any additional application-provided data, encoded as the DER
encoding of an ASN.1 OCTET STRING encoding of an ASN.1 OCTET STRING
4.1. GSS_Make_sshv2_channel_bindings() 4.1. GSS_Make_sshv2_channel_bindings()
Inputs: Inputs:
o session_id OCTET STRING, o session_id OCTET STRING,
o additional_app_data OCTET STRING o additional_app_data OCTET STRING
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); );
5. Channel Bindings for TLS 5. Channel Bindings for TLS
The TLS channel bindings are constructed as an octet string for the The TLS channel bindings are constructed as an octet string for the
'application-data' field of the channel bindings by concatenating the 'application-data' field of the channel bindings by concatenating the
following values and in this order: following values and in this order:
1. The ASCII string "GSS TLSv1.0 CB:" 1. The ASCII string "GSS TLSv1.0 CB:"
2. The TLS finished message sent by the client 2. The output of the TLS PRF as applied to a constant octet string
(TBD) (number of octets also to be determined).
3. The TLS finished message sent by the server
4. Any additional application-provided data, encoded as the DER 3. Any additional application-provided data, encoded as the DER
encoding of an ASN.1 OCTET STRING encoding of an ASN.1 OCTET STRING
5.1. GSS_Make_tls_channel_bindings() 5.1. GSS_Make_tls_channel_bindings()
Inputs: Inputs:
o client_finished_msg OCTET STRING, o prf_output OCTET STRING,
o server_finished_msg OCTET STRING,
o additional_app_data OCTET STRING o additional_app_data OCTET STRING
Outputs: Outputs:
o major_status INTEGER, o major_status INTEGER,
o minor_status INTEGER, o minor_status INTEGER,
o channel_bindings_app_data OCTET STRING o channel_bindings_app_data OCTET STRING
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as a result, perhaps, of a memory management, or similar failure. as a result, perhaps, of a memory management, or similar failure.
This function constructs an OCTET STRING for use as the value of the This function constructs an OCTET STRING for use as the value of the
application-data field of the GSS-CHANNEL-BINDINGS structure application-data field of the GSS-CHANNEL-BINDINGS structure
described above. described above.
5.1.1. C-Bindings 5.1.1. C-Bindings
OM_uint32 gss_make_tls_channel_bindings( OM_uint32 gss_make_tls_channel_bindings(
OM_uint32 *minor_status, OM_uint32 *minor_status,
const gss_buffer_t client_finished_msg, const gss_buffer_t prf_octets,
const gss_buffer_t server_finished_msg,
const gss_buffer_t additional_app_data, const gss_buffer_t additional_app_data,
gss_buffer_t channel_bindings_app_data gss_buffer_t channel_bindings_app_data
); );
6. Channel Bindings for IPsec 6. Channel Bindings for IPsec
The IPsec channel bindings are constructed as an octet string for the The IPsec channel bindings are constructed as an octet string for the
'application-data' field of the channel bindings by concatenating the 'application-data' field of the channel bindings by concatenating the
following values and in this order: following values and in this order:
1. The ASCII string "GSS IPsec CB:" 1. The ASCII string "GSS IPsec CB:"
2. The transform ID for encryption, as a 16-bit big-endian word 2. The transform ID for encryption, as a 16-bit big-endian word
3. The transform ID for integrity protection, as 16-bit in big- 3. The transform ID for integrity protection, as 16-bit in big-
endian word endian word
4. NOTE: The following needs to be updated to take into account 4. Length (four octet, network byte order) and value of the local
progress of BTNS. IKE ID (may be a PUBLICKEY ID[I-D.ietf-btns-core])
5. The initiator ID payload as used in the key exchange protocol
used for setting up the channel's SAs
6. The responder ID payload as used in the key exchange protocol 5. Length (four octet, network byte order) and value of the peer IKE
used for setting up the channel's SAs (may be a PUBLICKEY ID [I-D.ietf-btns-core]
7. Any additional application-provided data, encoded as the DER 6. Any additional application-provided data, encoded as the DER
encoding of an ASN.1 OCTET STRING encoding of an ASN.1 OCTET STRING
See also: [I-D.ietf-btns-connection-latching]
Note that traffic selectors are not included. Inclusion of Note that traffic selectors are not included. Inclusion of
confidentiality/integrity algorithms protects against MITMs that can confidentiality/integrity algorithms protects against MITMs that can
compromise weaker algorithms that policy might permit, for the same compromise weaker algorithms that policy might permit, for the same
peers, for other traffic. peers, for other traffic.
6.1. GSS_Make_ipsec_channel_bindings() 6.1. GSS_Make_ipsec_channel_bindings()
Inputs: Inputs:
o encr_alg INTEGER, o encr_alg INTEGER,
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OM_uint32 integ_alg, OM_uint32 integ_alg,
const gss_buffer_t initiator_id, const gss_buffer_t initiator_id,
const gss_buffer_t acceptor_id, const gss_buffer_t acceptor_id,
const gss_buffer_t additional_app_data, const gss_buffer_t additional_app_data,
gss_buffer_t channel_bindings_app_data gss_buffer_t channel_bindings_app_data
); );
7. Security Considerations 7. Security Considerations
For general security considerations relating to channel bindings see For general security considerations relating to channel bindings see
[CHANNEL-BINDINGS] [I-D.ietf-nfsv4-channel-bindings]
8. References 8. Normative
8.1. Normative [I-D.ietf-btns-connection-latching]
Williams, N., "IPsec Channels: Connection Latching",
draft-ietf-btns-connection-latching-00 (work in progress),
February 2006.
[I-D.ietf-btns-core]
Williams, N., "Better-Than-Nothing-Security: An
Unauthenticated Mode of IPsec", draft-ietf-btns-core-00
(work in progress), February 2006.
[I-D.ietf-nfsv4-channel-bindings]
Williams, N., "On the Use of Channel Bindings to Secure
Channels", draft-ietf-nfsv4-channel-bindings-03 (work in
progress), February 2005.
[RFC1964] Linn, J., "The Kerberos Version 5 GSS-API Mechanism", [RFC1964] Linn, J., "The Kerberos Version 5 GSS-API Mechanism",
RFC 1964, June 1996. RFC 1964, June 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2743] Linn, J., "Generic Security Service Application Program [RFC2743] Linn, J., "Generic Security Service Application Program
Interface Version 2, Update 1", RFC 2743, January 2000. Interface Version 2, Update 1", RFC 2743, January 2000.
[RFC2744] Wray, J., "Generic Security Service API Version 2 : [RFC2744] Wray, J., "Generic Security Service API Version 2 :
C-bindings", RFC 2744, January 2000. C-bindings", RFC 2744, January 2000.
8.2. Informative
[RFC0854] Postel, J. and J. Reynolds, "Telnet Protocol
Specification", STD 8, RFC 854, May 1983.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[RFC2025] Adams, C., "The Simple Public-Key GSS-API Mechanism
(SPKM)", RFC 2025, October 1996.
[RFC2203] Eisler, M., Chiu, A., and L. Ling, "RPCSEC_GSS Protocol
Specification", RFC 2203, September 1997.
[RFC2478] Baize, E. and D. Pinkas, "The Simple and Protected GSS-API
Negotiation Mechanism", RFC 2478, December 1998.
[RFC2623] Eisler, M., "NFS Version 2 and Version 3 Security Issues
and the NFS Protocol's Use of RPCSEC_GSS and Kerberos V5",
RFC 2623, June 1999.
[RFC3530] Shepler, S., Callaghan, B., Robinson, D., Thurlow, R.,
Beame, C., Eisler, M., and D. Noveck, "Network File System
(NFS) version 4 Protocol", RFC 3530, April 2003.
Appendix A. Acknowledgments Appendix A. Acknowledgments
The author would like to thank Mike Eisler for his work on the The author would like to thank Mike Eisler for his work on the
Channel Conjunction Mechanism I-D and for bringing the problem to a Channel Conjunction Mechanism I-D and for bringing the problem to a
head, Sam Hartman for pointing out that channel bindings provide a head, Sam Hartman for pointing out that channel bindings provide a
general solution to the channel binding problem, Jeff Altman for his general solution to the channel binding problem, Jeff Altman for his
suggestion of using the TLS finished messages as the TLS channel suggestion of using the TLS finished messages as the TLS channel
bindings, Bill Sommerfeld, for his help in developing channel bindings, Bill Sommerfeld, for his help in developing channel
bindings for IPsec, and Radia Perlman for her most helpful comments. bindings for IPsec, and Radia Perlman for her most helpful comments.
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This document and the information contained herein are provided on an This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Copyright Statement Copyright Statement
Copyright (C) The Internet Society (2005). This document is subject Copyright (C) The Internet Society (2006). This document is subject
to the rights, licenses and restrictions contained in BCP 78, and to the rights, licenses and restrictions contained in BCP 78, and
except as set forth therein, the authors retain all their rights. except as set forth therein, the authors retain all their rights.
Acknowledgment Acknowledgment
Funding for the RFC Editor function is currently provided by the Funding for the RFC Editor function is currently provided by the
Internet Society. Internet Society.
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