--- 1/draft-ietf-dnsop-reflectors-are-evil-05.txt 2008-09-01 20:12:21.000000000 +0200 +++ 2/draft-ietf-dnsop-reflectors-are-evil-06.txt 2008-09-01 20:12:21.000000000 +0200 @@ -1,19 +1,19 @@ Network Working Group J. Damas Internet-Draft ISC -Intended status: Best Current F. Neves -Practice Registro.br -Expires: June 5, 2008 December 3, 2007 +Intended status: BCP F. Neves +Expires: March 5, 2009 Registro.br + September 1, 2008 Preventing Use of Recursive Nameservers in Reflector Attacks - draft-ietf-dnsop-reflectors-are-evil-05.txt + draft-ietf-dnsop-reflectors-are-evil-06.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that @@ -24,25 +24,21 @@ 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. - This Internet-Draft will expire on June 5, 2008. - -Copyright Notice - - Copyright (C) The IETF Trust (2007). + This Internet-Draft will expire on March 5, 2009. Abstract This document describes ways to prevent the use of default configured recursive nameservers as reflectors in Denial of Service (DoS) attacks. Recommended configuration as measures to mitigate the attack are given. Table of Contents @@ -100,21 +96,21 @@ 3. Problem Description Because most DNS traffic is stateless by design, an attacker could start a DoS attack in the following way: 1. The attacker starts by configuring a record on any zone he has access to, normally with large RDATA and TTL. 2. Taking advantage of clients on non-BCP38 networks, the attacker then crafts a query using the source address of their target - victim and sends it to an open recursive nameserver (ORNS). + victim and sends it to an open recursive nameserver. 3. Each open recursive nameserver proceeds with the resolution, caches the record and finally sends it to the target. After this first lookup, access to the authoritative nameservers is normally no longer necessary. The record will remain cached for the duration of the TTL at the open recursive nameserver even if it's deleted from the zone. 4. Cleanup of the zone might, depending on the implementation used in the open recursive nameserver, afford a way to clean the cached record from the open recursive nameserver. This would possibly involve queries luring the open recursive nameserver to @@ -143,24 +139,24 @@ knit community, some nameserver implementations have been made available with default configurations that when used for recursive nameservers made the server accessible to all hosts on the Internet. For years this was a convenient and helpful configuration, enabling wider availability of services. As this document aims to make apparent, it is now much better to be conscious of ones own nameserver services and focus the delivery of services on the intended audience of those services, be they a university campus, an enterprise or an ISP's customers. The target audience also includes - operators of small network operators and private server managers who - decide to operate nameservers with the aim of optimising their DNS - service, as these are more likely to use default configurations as - shipped by implementors. + operators of small networks and private server managers who decide to + operate nameservers with the aim of optimising their DNS service, as + these are more likely to use default configurations as shipped by + implementors. 4. Recommended Configuration In this section we describe the Best Current Practice for operating recursive nameservers. Following these recommendations would reduce the chances of having a given recursive nameserver be used for the generation of an amplification attack. The generic recommendation to nameserver operators is to use the means provided by the implementation of choice to provide recursive @@ -208,20 +204,28 @@ Multihomed Network" [BCP84] maybe a useful additional reference. By default, nameservers SHOULD NOT offer recursive service to external networks. 5. Security Considerations This document does not create any new security issues for the DNS protocol, it deals with a weakness in implementations. + Deployment of SIG(0) transaction security should consider the caveats + with SIG(0) computational expense as it uses public key cryptography + rather than the symmetric keys used by TSIG. In addition, the + identification of the appropriate keys needs similar mechanisms to + those for deploying TSIG, or alternatively, the use of DNSSEC + signatures (RRSIGs) over the KEY RRs if published in DNS. This will + in turn require the appropriate management of DNSSEC trust anchors. + 6. Acknowledgments The authors would like to acknowledge the helpful input and comments of Joe Abley, Olafur Gudmundsson, Pekka Savola, Andrew Sullivan and Tim Polk. 7. IANA Considerations This document does not define a registry and does not require any IANA action. @@ -272,21 +276,21 @@ Av. das Nacoes Unidas, 11541, 7 Sao Paulo, SP 04578-000 BR Phone: +55 11 5509 3511 Email: fneves@registro.br URI: http://registro.br/ Full Copyright Statement - Copyright (C) The IETF Trust (2007). + Copyright (C) The IETF Trust (2008). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF @@ -309,15 +313,10 @@ attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. - -Acknowledgment - - Funding for the RFC Editor function is provided by the IETF - Administrative Support Activity (IASA).