draft-ietf-dprive-edns0-padding-00.txt   draft-ietf-dprive-edns0-padding-01.txt 
Network Working Group A. Mayrhofer Network Working Group A. Mayrhofer
Internet-Draft nic.at GmbH Internet-Draft nic.at GmbH
Intended status: Standards Track November 4, 2015 Intended status: Standards Track November 24, 2015
Expires: May 7, 2016 Expires: May 27, 2016
The EDNS(0) Padding Option The EDNS(0) Padding Option
draft-ietf-dprive-edns0-padding-00 draft-ietf-dprive-edns0-padding-01
Abstract Abstract
This document specifies the EDNS(0) 'Padding' option, which allows This document specifies the EDNS(0) 'Padding' option, which allows
DNS clients and servers to pad request and response messages by a DNS clients and servers to pad request and response messages by a
variable number of octets. variable number of octets.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
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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 May 7, 2016. This Internet-Draft will expire on May 27, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 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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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. The 'Padding' Option . . . . . . . . . . . . . . . . . . . . 3 3. The 'Padding' Option . . . . . . . . . . . . . . . . . . . . 3
4. Usage Considerations . . . . . . . . . . . . . . . . . . . . 3 4. Usage Considerations . . . . . . . . . . . . . . . . . . . . 3
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4
6. Security Considerations . . . . . . . . . . . . . . . . . . . 4 6. Security Considerations . . . . . . . . . . . . . . . . . . . 4
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
8. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 8. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
8.1. draft-ieft-dprive-edns0-padding-00 . . . . . . . . . . . 4 8.1. draft-ietf-dprive-edns0-padding-01 . . . . . . . . . . . 4
8.2. draft-mayrhofer-edns0-padding-01 . . . . . . . . . . . . 4 8.2. draft-ieft-dprive-edns0-padding-00 . . . . . . . . . . . 5
8.3. draft-mayrhofer-edns0-padding-00 . . . . . . . . . . . . 4 8.3. draft-mayrhofer-edns0-padding-01 . . . . . . . . . . . . 5
9. Normative References . . . . . . . . . . . . . . . . . . . . 5 8.4. draft-mayrhofer-edns0-padding-00 . . . . . . . . . . . . 5
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
9.1. Normative References . . . . . . . . . . . . . . . . . . 5
9.2. Informative References . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5
1. Introduction 1. Introduction
The Domain Name System (DNS) [RFC1035] was specified to transport DNS The Domain Name System (DNS) [RFC1035] was specified to transport DNS
packets in clear text form. Since this can expose significant packets in clear text form. Since this can expose significant
amounts of information about the internet activities of an end user, amounts of information about the internet activities of an end user,
the IETF has undertaken work to provide confidentiality to DNS the IETF has undertaken work to provide confidentiality to DNS
transactions (see the DPRIVE WG). Encrypting the DNS transport is transactions (see the DPRIVE WG). Encrypting the DNS transport is
considered as one of the options to improve the situation. considered as one of the options to improve the situation.
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+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| OPTION-CODE | | OPTION-CODE |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| OPTION-LENGTH | | OPTION-LENGTH |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| (PADDING) ... (PADDING) ... / | (PADDING) ... (PADDING) ... /
+- - - - - - - - - - - - - - - - +- - - - - - - - - - - - - - - -
Figure 1 Figure 1
The OPTION-CODE for the 'Padding' option is [[TODO-IANA]]. The OPTION-CODE for the 'Padding' option is 12.
The OPTION-LENGTH for the 'Padding' option is the size (in octects) The OPTION-LENGTH for the 'Padding' option is the size (in octets) of
of the PADDING. The minimum number of padding octects is 0. the PADDING. The minimum number of padding octets is 0.
The PADDING octects MUST be set to 0x00. If a Responder detects non- The PADDING octets SHOULD be set to 0x00. Application developers who
0x00 octects in the padding of a query, a FORMERR (RCODE=1) MUST be are concerned about misguided lower layer compression MAY instead
returned. fill the PADDING octets with the output of a cryptographic random
number generator. Responders MUST NOT reject messages containing
non-0x00 PADDING octets.
4. Usage Considerations 4. Usage Considerations
This document does not specify the actual amount of padding to be This document does not specify the actual amount of padding to be
used, since this depends on the situation in which the option is used, since this depends on the situation in which the option is
used. However, padded DNS messages MUST NOT exceed the number of used. However, padded DNS messages MUST NOT exceed the number of
octets specified in the Requestor's Payload Size field encoded in The octets specified in the Requestor's Payload Size field encoded in The
RR Class Field (see Section 6.2.3 and 6.2.4 of [RFC6891]). RR Class Field (see Section 6.2.3 and 6.2.4 of [RFC6891]).
Responders MUST pad DNS responses when the respective DNS query Responders MUST pad DNS responses when the respective DNS query
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maximum UDP payload size. maximum UDP payload size.
Responders MAY pad DNS responses when the respective DNS query Responders MAY pad DNS responses when the respective DNS query
indicated EDNS(0) support of the Requestor. indicated EDNS(0) support of the Requestor.
Responders MUST NOT pad DNS responses when the respective DNS query Responders MUST NOT pad DNS responses when the respective DNS query
did not indicate EDNS(0). did not indicate EDNS(0).
5. IANA Considerations 5. IANA Considerations
IANA is requested to assign an EDNS Option Code (as described in IANA has assigned EDNS Option Code 12 for Padding.
Section 9 of [RFC6891]) for the 'Padding' option specified in this
document. IANA is requested to update the respective registration record by
changing the Reference field to [[THISRFC]] and the Status field to
'Standard'.
6. Security Considerations 6. Security Considerations
Padding DNS packets obviously increases their size, and will Padding DNS packets obviously increases their size, and will
therefore lead to increased traffic, can lead to increased number of therefore lead to increased traffic, can lead to increased number of
truncated packets when used over UDP-based transport. truncated packets when used over UDP-based transport.
The use of the EDNS(0) Padding provides only a benefit when DNS The use of the EDNS(0) Padding provides only a benefit when DNS
packets are not transported in clear text. Implementations therefore packets are not transported in clear text. Implementations therefore
SHOULD avoid using this option if the DNS transport is not encrypted. SHOULD avoid using this option if the DNS transport is not encrypted.
The payload of the 'Padding' option could be used as a covert Padding length might be affected by lower-level compression.
channel. In order to prevent this, padding octets are required to be Therefore (as described in Section 3.3 of [RFC7525]), implementations
set to 0x00. It shall be noted that variations in the OPTION-SIZE and deployments SHOULD disable TLS-level compression.
itself could still be abused for expensive and low-bandwith covert
communication. The payload of the 'Padding' option could (like many other fields in
the DNS protocol) be used as a covert channel.
7. Acknowledgements 7. Acknowledgements
This document was inspired by a discussion with Daniel Kahn Gillmor This document was inspired by a discussion with Daniel Kahn Gillmor
during IETF93, as an alternative to the proposed padding on the TLS during IETF93, as an alternative to the proposed padding on the TLS
layer. layer. Allison Mankin and Christian Huitema suggested text for this
document.
8. Changes 8. Changes
8.1. draft-ieft-dprive-edns0-padding-00 8.1. draft-ietf-dprive-edns0-padding-01
Fixed 'octects' typo. Changed 'covert channel' text to align with
allowing non-0x00 padding. changed IANA considerations - assigned
option code is 12. Changed field definitions to allow for non-0x00
padding, removed FORMERR requirement. referenced rfc7525 in security
considerations. added acknowledgements.
8.2. draft-ieft-dprive-edns0-padding-00
Adopted by WG. Changed text about message size limit based on Adopted by WG. Changed text about message size limit based on
feedback. feedback.
8.2. draft-mayrhofer-edns0-padding-01 8.3. draft-mayrhofer-edns0-padding-01
Changed minimum padding size to 0, rewrote Usage Considerations Changed minimum padding size to 0, rewrote Usage Considerations
section, extended Security considerations section section, extended Security considerations section
8.3. draft-mayrhofer-edns0-padding-00 8.4. draft-mayrhofer-edns0-padding-00
Initial version Initial version
9. Normative References 9. References
9.1. Normative References
[RFC1035] Mockapetris, P., "Domain names - implementation and [RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <http://www.rfc-editor.org/info/rfc1035>. November 1987, <http://www.rfc-editor.org/info/rfc1035>.
[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, DOI 10.17487/ Requirement Levels", BCP 14, RFC 2119,
RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms [RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms
for DNS (EDNS(0))", STD 75, RFC 6891, DOI 10.17487/ for DNS (EDNS(0))", STD 75, RFC 6891,
RFC6891, April 2013, DOI 10.17487/RFC6891, April 2013,
<http://www.rfc-editor.org/info/rfc6891>. <http://www.rfc-editor.org/info/rfc6891>.
Author's Address 9.2. Informative References
[RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
2015, <http://www.rfc-editor.org/info/rfc7525>.
Author's Address
Alexander Mayrhofer Alexander Mayrhofer
nic.at GmbH nic.at GmbH
Karlsplatz 1/2/9 Karlsplatz 1/2/9
Vienna 1010 Vienna 1010
Austria Austria
Email: alex.mayrhofer.ietf@gmail.com Email: alex.mayrhofer.ietf@gmail.com
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