Working Group Aravind Prasad Sridharan Internet-Draft DELL Intended Status: Standards Track November 12, 2014 Expires: May 16, 2015 Data Confidentiality in IS-IS draft-aravind-isis-confidentiality-data-00 Abstract This document specifies the mechanism to provide data confidentiality for Intermediate System to Intermediate System (IS-IS) Link State PDUs (LSPs) and avoid possible replay attacks. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/1id-abstracts.html The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html This Internet-Draft will expire on May 16, 2015 Copyright and License Notice Copyright (c) 2014 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 Aravind Prasad Sridharan Expires May 16, 2015 [Page 1] INTERNET DRAFT Data Confidentiality in IS-IS November 12, 2014 carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Fields for Encryption . . . . . . . . . . . . . . . . . . . . . 3 3. Implementation and Backward Compatibility . . . . . . . . . . . 3 4. Other considerations . . . . . . . . . . . . . . . . . . . . . 3 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 4 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 4 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 4 7.1 Normative References . . . . . . . . . . . . . . . . . . . 4 7.2 Informative References . . . . . . . . . . . . . . . . . . 4 8. Authors' Address . . . . . . . . . . . . . . . . . . . . . . . 5 1 Introduction Currently, ISIS doesn't have any mechanism that provides confidentiality for its data sent across the network. Authentication mechanisms can only authenticate routers and cannot avoid replay attacks. Further checksums and Authentications in LSPs don't include "Remaining Lifetime field" in its calculations and hence, are prone to replay attacks that can exploit this behavior (Lifetime field could be modified and replayed). Hence, it is possible for an attacker to snoop the ISIS packets and replay it with modifications to affect the overall functioning of the protocol in the network. The IETF Draft ([I-D.chunduri-isis-extended-sequence-no-tlv]) proposes the use of optional sequence number TLVs. Although it provides a way to counter replay attacks, no mechanism is available to maintain the data confidentiality of the packets. Hence, its possible for the intruders to initiate LSPs with zero "Remaining Lifetime field" and thereby causing the LSPs to purge in the network. The Target Router may retransmit the LSP with higher sequence numbers but this could again be compromised by the attacker. This continuous LSP re-transmissions and purges could cause flood the network creating a havoc and may also cause the sequence number of all the LSPs to increase fast. If the sequence number increases to the maximum (0xFFFFFFFF), the IS-IS process must shut down for around 20 minutes (the product of MaxAge +ZeroAgeLifetime) to allow the old LSPs to age out of all the router databases. Aravind Prasad Sridharan Expires May 16, 2015 [Page 2] INTERNET DRAFT Data Confidentiality in IS-IS November 12, 2014 1.1 Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. 2 Fields for Encryption The "Remaining Life Time" field is generally not included in the Checksum calculations and Authentications and hence remains the most vulnerable field in LSP packet. Any changes made to the rest of the packet can be identified during evaluation at receiving systems. Proposal is to encrypt the key parameters in ISIS packets so as to increase the confidentiality of data exchanged. Practically, the entire PDU could be encrypted. But the most important part here is to maintain the confidentiality and also reduce the processing overload as much as possible at the Intermediate Systems. Since sequence numbers play a major role in finding out duplicate packets, it is more logical to encrypt the sequence numbers in the packets. Hence this reduces the probability of intruder to easily deduce the overall flow of packets. Hence the combination of proposed data confidentiality mechanism with Authentications will help to improve the overall security of data exchanged in network. 3 Implementation and Backward Compatibility For maintaining backward compatibility of legacy systems, the use of proposed sequence Number TLVs ([I-D. chunduri-isis-extended-sequence- no-tlv]) could be more useful since only the systems implementing this mechanism may process this TLV and other systems may neglect it thereby maintaining backward compatibility with legacy systems and help in easier deployment. Encryption could be carried out for the Packet Sequence Number (PSN) alone or for the Extended Session Sequence Number (ESSN) too (as referred in the [I-D. chunduri-isis- extended-sequence-no-tlv]). 4 Other considerations The keying mechanisms to be followed is out of scope for this draft and implementation specific. The focus of this draft is only to introduce a way to maintain the data confidentiality in ISIS LSPs and avoid possible replay attacks. Aravind Prasad Sridharan Expires May 16, 2015 [Page 3] INTERNET DRAFT Data Confidentiality in IS-IS November 12, 2014 5 Security Considerations This document does not introduce any new security concerns to IS-IS or any other specifications referenced in this document. 6 IANA Considerations No IANA actions required. 7 References 7.1 Normative References [ISO-10589] ISO, "Intermediate System to Intermediate System intra-domain routing information exchange protocol for use in conjunction with the protocol for providing the connectionless-mode network service (ISO 8473)", International Standard 10589:2002, Second Edition, 2002. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 7.2 Informative References [I-D.ietf-karp-isis-analysis] Chunduri, U., Tian, A., and W. Lu, "KARP IS-IS security analysis", draft-ietf-karp-isis-analysis-03 (work in progress), February 2014. [RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R., and M. Fanto, "IS-IS Generic Cryptographic Authentication", February 2009. [RFC6518] Lebovitz, G. and M. Bhatia, "Keying and Authentication for Routing Protocols (KARP) Design Guidelines", February 2012. [DoS] Voydock, V. and S. Kent, "Security Mechanisms in High-level Networks", ACM Computing Surveys Vol. 15, No. 2, June 1983. [Dobb96a] Dobbertin, H., "Cryptanalysis of MD5 Compress", EuroCrypt Rump Session 1996, May 1996. [I-D.chunduri-isis-extended-sequence-no-tlv] Chunduri, U., Tian, A., and Shen, "IS-IS Extended Sequence number TLV", draft-chunduri-isis-extended- sequence-no-tlv-04 (work in progress), July 4, 2014. Aravind Prasad Sridharan Expires May 16, 2015 [Page 4] INTERNET DRAFT Data Confidentiality in IS-IS November 12, 2014 8 Authors' Address Aravind Prasad Sridharan DELL Olympia Technology Park Guindy, Chennai 600032 India Phone: +91 44 4220 8658 Email: aravind_sridharan@dell.com Aravind Prasad Sridharan Expires May 16, 2015 [Page 5]