--- 1/draft-ietf-dprive-edns0-padding-00.txt 2015-11-24 04:15:35.015196710 -0800 +++ 2/draft-ietf-dprive-edns0-padding-01.txt 2015-11-24 04:15:35.031197098 -0800 @@ -1,18 +1,18 @@ Network Working Group A. Mayrhofer Internet-Draft nic.at GmbH -Intended status: Standards Track November 4, 2015 -Expires: May 7, 2016 +Intended status: Standards Track November 24, 2015 +Expires: May 27, 2016 The EDNS(0) Padding Option - draft-ietf-dprive-edns0-padding-00 + draft-ietf-dprive-edns0-padding-01 Abstract This document specifies the EDNS(0) 'Padding' option, which allows DNS clients and servers to pad request and response messages by a variable number of octets. Status of This Memo This Internet-Draft is submitted in full conformance with the @@ -21,21 +21,21 @@ 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 May 7, 2016. + This Internet-Draft will expire on May 27, 2016. Copyright Notice Copyright (c) 2015 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 @@ -48,24 +48,27 @@ Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2 3. The 'Padding' Option . . . . . . . . . . . . . . . . . . . . 3 4. Usage Considerations . . . . . . . . . . . . . . . . . . . . 3 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 6. Security Considerations . . . . . . . . . . . . . . . . . . . 4 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 8. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 - 8.1. draft-ieft-dprive-edns0-padding-00 . . . . . . . . . . . 4 - 8.2. draft-mayrhofer-edns0-padding-01 . . . . . . . . . . . . 4 - 8.3. draft-mayrhofer-edns0-padding-00 . . . . . . . . . . . . 4 - 9. Normative References . . . . . . . . . . . . . . . . . . . . 5 + 8.1. draft-ietf-dprive-edns0-padding-01 . . . . . . . . . . . 4 + 8.2. draft-ieft-dprive-edns0-padding-00 . . . . . . . . . . . 5 + 8.3. draft-mayrhofer-edns0-padding-01 . . . . . . . . . . . . 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 1. Introduction The Domain Name System (DNS) [RFC1035] was specified to transport DNS packets in clear text form. Since this can expose significant amounts of information about the internet activities of an end user, the IETF has undertaken work to provide confidentiality to DNS transactions (see the DPRIVE WG). Encrypting the DNS transport is considered as one of the options to improve the situation. @@ -106,28 +109,30 @@ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | OPTION-CODE | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | OPTION-LENGTH | +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ | (PADDING) ... (PADDING) ... / +- - - - - - - - - - - - - - - - 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) - of the PADDING. The minimum number of padding octects is 0. + 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 octects MUST be set to 0x00. If a Responder detects non- - 0x00 octects in the padding of a query, a FORMERR (RCODE=1) MUST be - returned. + The PADDING octets SHOULD be set to 0x00. Application developers who + are concerned about misguided lower layer compression MAY instead + 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 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. However, padded DNS messages MUST NOT exceed the number of 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]). Responders MUST pad DNS responses when the respective DNS query @@ -135,77 +140,98 @@ maximum UDP payload size. Responders MAY pad DNS responses when the respective DNS query indicated EDNS(0) support of the Requestor. Responders MUST NOT pad DNS responses when the respective DNS query did not indicate EDNS(0). 5. IANA Considerations - IANA is requested to assign an EDNS Option Code (as described in - Section 9 of [RFC6891]) for the 'Padding' option specified in this - document. + IANA has assigned EDNS Option Code 12 for Padding. + + 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 Padding DNS packets obviously increases their size, and will therefore lead to increased traffic, can lead to increased number of truncated packets when used over UDP-based transport. The use of the EDNS(0) Padding provides only a benefit when DNS packets are not transported in clear text. Implementations therefore SHOULD avoid using this option if the DNS transport is not encrypted. - The payload of the 'Padding' option could be used as a covert - channel. In order to prevent this, padding octets are required to be - set to 0x00. It shall be noted that variations in the OPTION-SIZE - itself could still be abused for expensive and low-bandwith covert - communication. + Padding length might be affected by lower-level compression. + Therefore (as described in Section 3.3 of [RFC7525]), implementations + and deployments SHOULD disable TLS-level compression. + + The payload of the 'Padding' option could (like many other fields in + the DNS protocol) be used as a covert channel. 7. Acknowledgements This document was inspired by a discussion with Daniel Kahn Gillmor 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 -8.1. 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 feedback. -8.2. draft-mayrhofer-edns0-padding-01 +8.3. draft-mayrhofer-edns0-padding-01 Changed minimum padding size to 0, rewrote Usage Considerations section, extended Security considerations section -8.3. draft-mayrhofer-edns0-padding-00 +8.4. draft-mayrhofer-edns0-padding-00 Initial version -9. Normative References +9. References + +9.1. Normative References [RFC1035] Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, November 1987, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate - Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ - RFC2119, March 1997, + Requirement Levels", BCP 14, RFC 2119, + DOI 10.17487/RFC2119, March 1997, . [RFC6891] Damas, J., Graff, M., and P. Vixie, "Extension Mechanisms - for DNS (EDNS(0))", STD 75, RFC 6891, DOI 10.17487/ - RFC6891, April 2013, + for DNS (EDNS(0))", STD 75, RFC 6891, + DOI 10.17487/RFC6891, April 2013, . -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, . + +Author's Address Alexander Mayrhofer nic.at GmbH Karlsplatz 1/2/9 Vienna 1010 Austria Email: alex.mayrhofer.ietf@gmail.com