draft-ietf-dprive-edns0-padding-01.txt   draft-ietf-dprive-edns0-padding-02.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 24, 2015 Intended status: Standards Track January 25, 2016
Expires: May 27, 2016 Expires: July 28, 2016
The EDNS(0) Padding Option The EDNS(0) Padding Option
draft-ietf-dprive-edns0-padding-01 draft-ietf-dprive-edns0-padding-02
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 27, 2016. This Internet-Draft will expire on July 28, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2016 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
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carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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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-ietf-dprive-edns0-padding-01 . . . . . . . . . . . 4 8.1. draft-ietf-dprive-edns0-padding-02 . . . . . . . . . . . 4
8.2. draft-ieft-dprive-edns0-padding-00 . . . . . . . . . . . 5 8.2. draft-ietf-dprive-edns0-padding-01 . . . . . . . . . . . 5
8.3. draft-mayrhofer-edns0-padding-01 . . . . . . . . . . . . 5 8.3. draft-ieft-dprive-edns0-padding-00 . . . . . . . . . . . 5
8.4. draft-mayrhofer-edns0-padding-00 . . . . . . . . . . . . 5 8.4. draft-mayrhofer-edns0-padding-01 . . . . . . . . . . . . 5
8.5. draft-mayrhofer-edns0-padding-00 . . . . . . . . . . . . 5
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
9.1. Normative References . . . . . . . . . . . . . . . . . . 5 9.1. Normative References . . . . . . . . . . . . . . . . . . 5
9.2. Informative References . . . . . . . . . . . . . . . . . 5 9.2. Informative References . . . . . . . . . . . . . . . . . 5
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6
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 messages 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.
However, even if both DNS query and response packets were encrypted, However, even if both DNS query and response messages were encrypted,
meta data of these packets could be used to correlate such packets meta data of could still be used to correlate such messages with well
with well known unencrypted packets, hence jeopardizing some of the known unencrypted messages, hence jeopardizing some of the
confidentiality gained by encryption. One such property is the confidentiality gained by encryption. One such property is the
message size. message size.
This document specifies the Extensions Mechanisms for DNS (EDNS(0)) This document specifies the Extensions Mechanisms for DNS (EDNS(0))
"Padding" Option, which allows to artificially increase the size of a "Padding" Option, which allows to artificially increase the size of a
DNS message by a variable number of bytes, significantly hampering DNS message by a variable number of bytes, significantly hampering
size-based correlation of the encrypted packet. size-based correlation of the encrypted message.
2. Terminology 2. Terminology
The terms "Requestor", "Responder" are to be interpreted as specified The terms "Requestor", "Responder" are to be interpreted as specified
in [RFC6891]. in [RFC6891].
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in "OPTIONAL" in this document are to be interpreted as described in
[RFC2119]. [RFC2119].
3. The 'Padding' Option 3. The 'Padding' Option
The EDNS(0) [RFC6891] specifies a mechanism to include new options in The EDNS(0) [RFC6891] specifies a mechanism to include new options in
DNS packets, contained in the RDATA of the OPT meta-RR. This DNS packets, contained in the RDATA of the OPT meta-RR. This
document specifies the 'Padding' option in order to allow clients and document specifies the 'Padding' option in order to allow clients and
servers pad DNS packets by a variable number of bytes. The 'Padding' servers pad DNS packets by a variable number of bytes. The 'Padding'
option MUST occur at most once per OPT meta-RR. option MUST occur at most once per OPT meta-RR (and hence, at most
once per message).
The figure below specifies the structure of the option in the RDATA The figure below specifies the structure of the option in the RDATA
of the OPT RR: of the OPT RR:
0 8 16 0 8 16
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| OPTION-CODE | | OPTION-CODE |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| OPTION-LENGTH | | OPTION-LENGTH |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
| (PADDING) ... (PADDING) ... / | (PADDING) ... (PADDING) ... /
+- - - - - - - - - - - - - - - - +- - - - - - - - - - - - - - - -
Figure 1 Figure 1
The OPTION-CODE for the 'Padding' option is 12. The OPTION-CODE for the 'Padding' option is 12.
The OPTION-LENGTH for the 'Padding' option is the size (in octets) of The OPTION-LENGTH for the 'Padding' option is the size (in octets) of
the PADDING. The minimum number of padding octets is 0. the PADDING. The minimum number of padding octets is 0.
The PADDING octets SHOULD be set to 0x00. Application developers who The PADDING octets SHOULD be set to 0x00. Other values MAY be used;
are concerned about misguided lower layer compression MAY instead for example, in cases where there is a concern that the padded
fill the PADDING octets with the output of a cryptographic random message could be subject to compression before encryption. PADDING
number generator. Responders MUST NOT reject messages containing octets of any value MUST be accepted in messages received.
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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IANA has assigned EDNS Option Code 12 for Padding. IANA has assigned EDNS Option Code 12 for Padding.
IANA is requested to update the respective registration record by IANA is requested to update the respective registration record by
changing the Reference field to [[THISRFC]] and the Status field to changing the Reference field to [[THISRFC]] and the Status field to
'Standard'. '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.
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.
Padding length might be affected by lower-level compression. Padding length might be affected by lower-level compression.
Therefore (as described in Section 3.3 of [RFC7525]), implementations Therefore (as described in Section 3.3 of [RFC7525]), implementations
and deployments SHOULD disable TLS-level compression. and deployments SHOULD disable TLS-level compression.
The payload of the 'Padding' option could (like many other fields in The payload of the 'Padding' option could (like many other fields in
the DNS protocol) be used as a covert channel. 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. Allison Mankin and Christian Huitema suggested text for this layer. Allison Mankin, Andreas Gustaffson, Christian Huitema and
document. Jinmei Tatuya suggested text for this document.
8. Changes 8. Changes
8.1. draft-ietf-dprive-edns0-padding-01 Note to RFC Editors: Please remove this whole section before
publication
8.1. draft-ietf-dprive-edns0-padding-02
Clarified that changes section is to be removed before publication.
Clarified that both Requestors and Responders are to ignore padding
contents. changed text about non-zero padding contents based on WGLC
comments. removed security considerations about truncation based on
WGLC comment. added more acknowledgements. replaced "packets" with
"messages" where appropriate.
8.2. draft-ietf-dprive-edns0-padding-01
Fixed 'octects' typo. Changed 'covert channel' text to align with Fixed 'octects' typo. Changed 'covert channel' text to align with
allowing non-0x00 padding. changed IANA considerations - assigned allowing non-0x00 padding. changed IANA considerations - assigned
option code is 12. Changed field definitions to allow for non-0x00 option code is 12. Changed field definitions to allow for non-0x00
padding, removed FORMERR requirement. referenced rfc7525 in security padding, removed FORMERR requirement. referenced rfc7525 in security
considerations. added acknowledgements. considerations. added acknowledgements.
8.2. draft-ieft-dprive-edns0-padding-00 8.3. 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.
8.3. draft-mayrhofer-edns0-padding-01 8.4. 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
8.4. draft-mayrhofer-edns0-padding-00 8.5. draft-mayrhofer-edns0-padding-00
Initial version Initial version
9. References 9. References
9.1. Normative 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>.
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