draft-ietf-curdle-gss-keyex-sha2-01.txt   draft-ietf-curdle-gss-keyex-sha2-02.txt 
Internet Engineering Task Force S. Sorce Internet Engineering Task Force S. Sorce
Internet-Draft H. Kario Internet-Draft H. Kario
Updates: 4462 (if approved) Red Hat, Inc. Updates: 4462 (if approved) Red Hat, Inc.
Intended status: Standards Track June 4, 2017 Intended status: Standards Track June 15, 2017
Expires: December 6, 2017 Expires: December 17, 2017
GSS-API Key Exchange with SHA2 GSS-API Key Exchange with SHA2
draft-ietf-curdle-gss-keyex-sha2-01 draft-ietf-curdle-gss-keyex-sha2-02
Abstract Abstract
This document specifies additions and amendments to SSH GSS-API This document specifies additions and amendments to SSH GSS-API
Methods [RFC4462]. It defines a new key exchange method that uses Methods [RFC4462]. It defines a new key exchange method that uses
SHA-2 for integrity and deprecates weak DH groups. The purpose of SHA-2 for integrity and deprecates weak DH groups. The purpose of
this specification is to modernize the cryptographic primitives used this specification is to modernize the cryptographic primitives used
by GSS Key Exchanges. by GSS Key Exchanges.
Status of This Memo Status of This Memo
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on December 6, 2017. This Internet-Draft will expire on December 17, 2017.
Copyright Notice Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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3. Document Conventions . . . . . . . . . . . . . . . . . . . . 3 3. Document Conventions . . . . . . . . . . . . . . . . . . . . 3
4. New Diffie-Hellman Key Exchange methods . . . . . . . . . . . 3 4. New Diffie-Hellman Key Exchange methods . . . . . . . . . . . 3
4.1. gss-group14-sha256-* . . . . . . . . . . . . . . . . . . 3 4.1. gss-group14-sha256-* . . . . . . . . . . . . . . . . . . 3
4.2. gss-group15-sha512-* . . . . . . . . . . . . . . . . . . 3 4.2. gss-group15-sha512-* . . . . . . . . . . . . . . . . . . 3
4.3. gss-group16-sha512-* . . . . . . . . . . . . . . . . . . 4 4.3. gss-group16-sha512-* . . . . . . . . . . . . . . . . . . 4
4.4. gss-group17-sha512-* . . . . . . . . . . . . . . . . . . 4 4.4. gss-group17-sha512-* . . . . . . . . . . . . . . . . . . 4
4.5. gss-group18-sha512-* . . . . . . . . . . . . . . . . . . 4 4.5. gss-group18-sha512-* . . . . . . . . . . . . . . . . . . 4
5. New Elliptic Curve Diffie-Hellman Key Exchange methods . . . 4 5. New Elliptic Curve Diffie-Hellman Key Exchange methods . . . 4
5.1. Generic GSS-API Key Exchange with ECDH . . . . . . . . . 4 5.1. Generic GSS-API Key Exchange with ECDH . . . . . . . . . 4
5.2. ECDH Key Exchange Methods . . . . . . . . . . . . . . . . 11 5.2. ECDH Key Exchange Methods . . . . . . . . . . . . . . . . 11
5.2.1. gss-nistp256-sha256-* . . . . . . . . . . . . . . . . 11 5.2.1. gss-nistp256-sha256-* . . . . . . . . . . . . . . . . 12
5.2.2. gss-nistp384-sha384-* . . . . . . . . . . . . . . . . 12 5.2.2. gss-nistp384-sha384-* . . . . . . . . . . . . . . . . 12
5.2.3. gss-nistp521-sha512-* . . . . . . . . . . . . . . . . 12 5.2.3. gss-nistp521-sha512-* . . . . . . . . . . . . . . . . 12
5.2.4. gss-curve25519-sha256-* . . . . . . . . . . . . . . . 12 5.2.4. gss-curve25519-sha256-* . . . . . . . . . . . . . . . 12
5.2.5. gss-curve448-sha512-* . . . . . . . . . . . . . . . . 12 5.2.5. gss-curve448-sha512-* . . . . . . . . . . . . . . . . 13
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
7. Security Considerations . . . . . . . . . . . . . . . . . . . 13 7. Security Considerations . . . . . . . . . . . . . . . . . . . 13
7.1. New Finite Field DH mechanisms . . . . . . . . . . . . . 13 7.1. New Finite Field DH mechanisms . . . . . . . . . . . . . 13
7.2. New Elliptic Curve DH mechanisms . . . . . . . . . . . . 13 7.2. New Elliptic Curve DH mechanisms . . . . . . . . . . . . 13
8. Normative References . . . . . . . . . . . . . . . . . . . . 13 7.3. GSSAPI Delegation . . . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 8. Normative References . . . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 16
1. Introduction 1. Introduction
SSH GSS-API Methods [RFC4462] allows the use of GSSAPI for SSH GSS-API Methods [RFC4462] allows the use of GSSAPI for
authentication and key exchange in SSH. It defines three exchange authentication and key exchange in SSH. It defines three exchange
methods all based on DH groups and SHA-1. The new methods described methods all based on DH groups and SHA-1. The new methods described
in this document are intended to support environments that desire to in this document are intended to support environments that desire to
use the SHA-2 cryptographic hash functions. use the SHA-2 cryptographic hash functions.
2. Rationale 2. Rationale
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Except for the use of a different secure hash function and larger DH Except for the use of a different secure hash function and larger DH
groups, no significant changes has been made to the protocol groups, no significant changes has been made to the protocol
described by [RFC4462]; therefore all the original Security described by [RFC4462]; therefore all the original Security
Considerations apply. Considerations apply.
7.2. New Elliptic Curve DH mechanisms 7.2. New Elliptic Curve DH mechanisms
Although a new cryptographic primitive is used with these methods the Although a new cryptographic primitive is used with these methods the
actual key exchange closely follows the key exchange defined in actual key exchange closely follows the key exchange defined in
[RFC5656]; therefore all the original Security Considerations as well [RFC5656]; therefore all the original Security Considerations as well
as those expressed in [RFC5656] apply. as those expressed in [RFC5656] apply.
7.3. GSSAPI Delegation
Some GSSAPI mechanisms can optionally delegate credentials to the
target host by setting the deleg_ret_flag. In this case extra care
must be taken to ensure that the acceptor being authenticated matches
the target the user intended. Some mechanisms implementations (like
commonly used krb5 libraries) may use insecure DNS resolution to
canonicalize the target name; in these cases spoofing a DNS response
that points to an attacker-controlled machine may results in the user
silently delegating credentials to the attacker, who can then
impersonate the user at will.
8. Normative References 8. Normative References
[ANSI-X9-62-2005] [ANSI-X9-62-2005]
American National Standards Institute, "Public Key American National Standards Institute, "Public Key
Cryptography for the Financial Services Industry, The Cryptography for the Financial Services Industry, The
Elliptic Curve Digital Signature Algorithm (ECDSA)", ANSI Elliptic Curve Digital Signature Algorithm (ECDSA)", ANSI
Standard X9.62, 2005. Standard X9.62, 2005.
[FIPS-180-4] [FIPS-180-4]
National Institute of Standards and Technology, "FIPS PUB National Institute of Standards and Technology, "FIPS PUB
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