Internet DRAFT - draft-asmithee-tls-dnssec-downprot
draft-asmithee-tls-dnssec-downprot
TLS Alan Smithee
Internet-Draft
Updates: 10000 (if approved) Alan Smithee
Intended status: Standards Track May 15, 2018
Expires: November 16, 2018
TLS Downgrade protection extension for TLS DNSSEC Authentication Chain
Extension
draft-asmithee-tls-dnssec-downprot-00
Abstract
This draft specifies a TLS extension that adds downgrade protection
for another TLS extension, [dnssec-chain-extension]. Without the
downgrade protection specified in this TLS extension, the only effect
of deploying [dnssec-chain-extension] is to reduce TLS security from
the standard "WebPKI security" to "WebPKI or DANE, whichever is
weaker".
This draft dictates that [dnssec-chain-extension] MUST only be used
in combination with this TLS extension, whose only content is a two
octet SupportLifetime value. A value of 0 prohibits the TLS client
from unilaterally requiring ongoing use of both TLS extensions based
on prior observation of their use (pinning). A non-zero value is the
value in hours for which this TLS extension as well as
[dnssec-chain-extension] MUST appear in subsequent TLS handshakes to
the same TLS hostname and port. If this TLS extention or
[dnssec-chain-extension] is missing from the TLS handshake within
this observed pinning time, the TLS client MUST assume it is under
attack and abort the TLS connection.
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 November 16, 2018.
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Copyright Notice
Copyright (c) 2018 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
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described in the Simplified BSD License.
Table of Contents
1. Requirements Notation . . . . . . . . . . . . . . . . . . . . 2
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
3. TLS DNSSEC Extension Downgrade Protection Extension format . 3
4. Operational Considerations . . . . . . . . . . . . . . . . . 3
5. Security Considerations . . . . . . . . . . . . . . . . . . . 4
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
7. Normative References . . . . . . . . . . . . . . . . . . . . 4
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5
1. Requirements Notation
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
2. Introduction
This draft specifies a TLS extension that adds downgrade protection
for another TLS extension, [dnssec-chain-extension]. Without the
downgrade protection specified in this TLS extension, the only effect
of deploying [dnssec-chain-extension] is to reduce TLS security from
the standard "WebPKI security" to "WebPKI or DANE, whichever is
weaker".
This draft dictates that [dnssec-chain-extension] MUST only be used
in combination with this TLS extension, whose only content is a two
byte SupportLifetime value. A value of 0 prohibits the TLS client
from unilaterally requiring ongoing use of both TLS extensions based
on prior observation of their use (pinning). A non-zero value is the
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value in hours for which this TLS extension as well as
[dnssec-chain-extension] MUST appear in subsequent TLS handshakes to
the same hostname and port. If this TLS extention or
[dnssec-chain-extension] is missing from the TLS handshake within
this observed pinning time, the TLS client MUST assume it is under
attack and abort the TLS connection.
3. TLS DNSSEC Extension Downgrade Protection Extension format
The "extension_data" field of the "dnssec_chain_commit" extension
contains a two octet value specifying the pinning time in hours for
both this extension and [dnssec-chain-extension] in the following
form:
struct {
uint16 SupportLifetime;
} DnssecChainExtensionCommitTime;
A zero "SupportLifetime" prohibits the client from unilaterally
requiring ongoing use of this extension or [dnssec-chain-extension]
based on prior observation of their use (pinning).
A non-zero value signifies the time in hours for which this resource
commits to publishing both this extension and
[dnssec-chain-extension]. If within the specified time a TLS
connection for this resource omits either TLS extension, the TLS
client MUST conclude it is under attack and MUST abort the TLS
connection.
4. Operational Considerations
A positive DANE validated response for the TLSA record in
[dnssec-chain-extension] MUST override any previous SupportLifetime
information that the TLS client stored previously. In addition, if
the TLS client previously obtained a valid TLSA record with a
SupportLifetime commitment further into the future, and as part of
the current TLS handshake it receives a DNSSEC-validated answer
containing no TLSA record and a Denial of Existence proof via
[dnssec-chain-extension], the TLS client MUST clear the previously
stored TLS extensions pinning value.
If a specific resource is served using multiple TLS servers or
clusters, and a non-zero value for SupportLifetime is used, all TLS
server instances MUST support serving both this extension and
[dnssec-chain-extension]. As long as no TLS service instance uses a
non-zero value, both TLS extensions can be rolled out incrementally
without any TLS clients commiting to either TLS extension.
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5. Security Considerations
This draft specifies a TLS extension that adds downgrade protection
for another TLS extension, [dnssec-chain-extension]. Without the
downgrade protection specified in this TLS extension, the only effect
of deploying [dnssec-chain-extension] is to reduce TLS security from
the standard "WebPKI security" to "WebPKI or DANE, whichever is
weaker".
This draft dictates that [dnssec-chain-extension] MUST only be used
in combination with this TLS extension, whose only content is a two
byte SupportLifetime value. A value of 0 prohibits the TLS client
from unilaterally requiring ongoing use of both TLS extensions based
on prior observation of their use (pinning). A non-zero value is the
value in hours for which this TLS extension as well as
[dnssec-chain-extension] MUST appear in subsequent TLS handshakes to
the same hostname and port. If this TLS extention or
[dnssec-chain-extension] is missing from the TLS handshake within
this observed pinning time, the TLS client MUST assume it is under
attack and abort the TLS connection.
6. IANA Considerations
This extension requires the registration of a new value in the TLS
ExtensionsType registry. The value requested from IANA is [TBD], and
the extension should be marked "Recommended" in accordance with "IANA
Registry Updates for TLS and DTLS" [TLSIANA].
7. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, <https://www.rfc-
editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[dnssec-chain-extension]
Shore, M., Barnes, R., Hugue, S., and W. Toorop, "A DANE
Record and DNSSEC Authentication Chain Extension for TLS",
March 2018, <https://tools.ietf.org/html/draft-ietf-tls-
dnssec-chain-extension-07>.
[TLSIANA] Salowey, J. and S. Turner, "IANA Registry Updates for TLS
and DTLS", <https://tools.ietf.org/html/draft-ietf-tls-
iana-registry-updates>.
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Authors' Addresses
Alan Smithee
EMail: pwouters@redhat.com
Alan Smithee
EMail: ietf-dane@dukhovni.org
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