Mobile Ad hoc Networking (MANET) U. Herberg Internet-Draft T. Clausen Intended status: Standards Track LIX, Ecole Polytechnique Expires: January 7, 2010 July 6, 2009 MANET Cryptographical Signature TLV Definition draft-herberg-manet-packetbb-sec-00 Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. 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The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on January 7, 2010. Copyright Notice Copyright (c) 2009 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 Herberg & Clausen Expires January 7, 2010 [Page 1] Internet-Draft MANET Cryptographical Signature TLV July 2009 Provisions Relating to IETF Documents in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Abstract This document describes a general and flexible TLV (type-length-value structure) for representing cryptographic signatures as well as timestamps, using the generalized MANET packet/message format [RFC5444]. It defines two Message TLVs and two Packet TLVs, for affixing a cryptographic signature and a timestamp to a packet and message, respectively. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Applicability Statement . . . . . . . . . . . . . . . . . . . 4 4. Protocol Overview and Functioning . . . . . . . . . . . . . . 5 5. General SIGNATURE TLV Structure . . . . . . . . . . . . . . . 5 6. General TIMESTAMP TLV Structure . . . . . . . . . . . . . . . 6 7. Message TLVs . . . . . . . . . . . . . . . . . . . . . . . . . 6 7.1. Message SIGNATURE TLV . . . . . . . . . . . . . . . . . . 6 7.2. Message TIMESTAMP TLV . . . . . . . . . . . . . . . . . . 7 8. Packet TLVs . . . . . . . . . . . . . . . . . . . . . . . . . 7 8.1. Packet SIGNATURE TLV . . . . . . . . . . . . . . . . . . . 7 8.1.1. Packet TIMESTAMP TLV . . . . . . . . . . . . . . . . . 7 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 9.1. TLV Registrations . . . . . . . . . . . . . . . . . . . . 7 9.1.1. Expert Review: Evaluation Guidelines . . . . . . . . . 7 9.1.2. Message TLV Type Registrations . . . . . . . . . . . . 8 9.1.3. Packet TLV Type Registrations . . . . . . . . . . . . 8 9.2. New IANA registries . . . . . . . . . . . . . . . . . . . 9 9.2.1. Expert Review: Evaluation Guidelines . . . . . . . . . 9 9.2.2. Hash-Function Registry . . . . . . . . . . . . . . . . 9 9.2.3. Cryptographic Algorithm Registry . . . . . . . . . . . 9 10. Security Considerations . . . . . . . . . . . . . . . . . . . 10 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10 12.1. Normative References . . . . . . . . . . . . . . . . . . . 10 12.2. Informative References . . . . . . . . . . . . . . . . . . 11 Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 11 A.1. Example Signed Message . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13 Herberg & Clausen Expires January 7, 2010 [Page 2] Internet-Draft MANET Cryptographical Signature TLV July 2009 1. Introduction This document: o specifies two TLVs for carrying cryptographic signatures and timestamps in packets and messages as defined by [RFC5444], o requests IANA allocations for these Packet and Message TLVs from the 0-127 message TLV range and the 0-128 Packet TLV range from [RFC5444], o describes how cryptographic signatures are calculated, taking into account the mutable message header fields ( and ) for messages where these fields are present, o requests creation of two IANA registries for recording code points for hash function and signature calculation, respectively. This document does not stipulate how to sign, validate, or encrypt messages. A specification of a routing protocol, using the security representation of this document, MUST specify appropriate interpretation of the TLVs. This document does also not promote a single algorithm for signature calculation or a single hash function, but rather establishes IANA registries for such. 2. Terminology The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119]. This document uses the terminology defined in [RFC5444]. Additionally, it defines the following terminology: o Hash-Function A hash function is an algorithm that takes a message of any length as input and produces a fixed-length string as output. Hash functions are used in cryptography for authentication and message integrity. o Signature: Herberg & Clausen Expires January 7, 2010 [Page 3] Internet-Draft MANET Cryptographical Signature TLV July 2009 A secure hash of the entire message is encrypted using the signer's private key, so that any change to the document will invalidate the signature and in order to prove that the message originates from the claimed sender. o Timestamp The timestamp indicates the time when a signature has been created. This information can be useful to determine the "freshness" of the signed message. "Old" messages can indicate replayed messages. 3. Applicability Statement The packet and message format defined in [RFC5444] accords MANET routing protocols using this format the ability to carry additional information in control messages, through inclusion of TLVs. Information so included in a control message MAY be used by the routing protocol, or an extension of the routing protocol, according to its specification. This document specifies how to calculate a cryptographic signature for a packet or message, as specified in [RFC5444], specifically how to treat "mutable" fields ( and ) in the message header such that the resulting signature can be correctly verified by any recipient, and how to include this signature, and other relevant information, by way of TLVs. A MANET routing protocol specification, or an extension of a MANET routing protocol specification, MAY use such included cryptographic signatures for, for example, rejecting messages where signature verification fails. Basic MANET routing protocol specifications are often "oblivious to security", however have a clause allowing a control message to be rejected as "badly formed" prior to it being processed or forwarded. Protocols such as [NHDP] and [OLSRv2] both recognize external reasons (such as failure to verify a signature) as being reasons for rejecting a message as "badly formed". This architecture is the result of the observation that with respect to security in MANETs, "one size rarely fits all" and that MANET routing protocol deployment domains have varying security requirements ranging from "unbreakable" to "virtually none". The virtue of this approach is that MANET routing protocol specifications (and implementations) can remain "generic", with extensions providing proper deployment-domain specific security mechanisms. The MANET routing protocol "security architecture", in which this specification situates itself, can therefore be summarized as Herberg & Clausen Expires January 7, 2010 [Page 4] Internet-Draft MANET Cryptographical Signature TLV July 2009 follows: o Security-oblivious MANET routing protocol specification, with a clause allowing an extension to reject a message (prior to processing/forwarding) as "badly formed". o MANET routing protocol security extensions, rejecting messages as "badly formed", as appropriate for a given deployment-domain. o Code-points and an exchange format for information necessary for specification of such security extensions. This document addresses the last of these issues, by specifying a common exchange format for cryptographic signatures. This document also makes reservations from within the Message TLV and Packet TLV registries of [RFC5444], to be used (and shared) among MANET routing protocol security extensions. Finally, this document establishes two shared IANA registries for code-points for hash functions and signature functions. 4. Protocol Overview and Functioning This specification does not describe a protocol, nor does it mandate specific node or protocol behavior. It represents a purely syntactical representation of security related information for use with [RFC5444] messages and packets, as well as sets up IANA registrations and registries. 5. General SIGNATURE TLV Structure The following data structure allows the representation of a cryptographic signature, including specification of the appropriate hash function and cryptographic algorithm used for calculating the signature. This data structure is specified, using the regular expression syntax of [RFC5444], by: = where: is an 8-bit unsigned integer field specifying the hash-function according to Table 3. Herberg & Clausen Expires January 7, 2010 [Page 5] Internet-Draft MANET Cryptographical Signature TLV July 2009 is an 8-bit unsigned integer field specifying the hash-function according to Table 4. is an unsigned integer field, whose length is -16, and which contains the cryptographic signature. The algorithm that is used for calculating the hash function MUST be selected from one of those listed in Table 3. Furthermore, MUST correspond to the number in that table assigned by IANA. The algorithm that is used for calculating the cryptographic algorithm MUST be selected from one of those listed in Table 4. Furthermore, MUST correspond to the number in that table assigned by IANA. 6. General TIMESTAMP TLV Structure The following data structure allows the representation of a timestamp. This data structure is specified, using the regular expression syntax of [RFC5444], by: = where: is an unsigned integer field, whose length is , and which contains the timestamp. The value of this variable is to be interpreted by the routing protocol as specified by the type extension of the TIMESTAMP TLV (refer to Table 2). 7. Message TLVs Two Message TLVs are defined, for including the cryptographic signature of a message, and for including the timestamp indicating the time at which the cryptographic signature was calculated. 7.1. Message SIGNATURE TLV A Message SIGNATURE TLV is an example of a SIGNATURE TLV as described in Section 5. When determining the for a message, the signature is calculated over the entire message, including the message header and all Message TLVs (other than Message SIGNATURE TLVs), with the following consideration: Herberg & Clausen Expires January 7, 2010 [Page 6] Internet-Draft MANET Cryptographical Signature TLV July 2009 o the fields and MUST be both assumed to have the value 0 (zero). 7.2. Message TIMESTAMP TLV A Message TIMESTAMP TLV is an example of a TIMESTAMP TLV as described in Section 6. 8. Packet TLVs Two Packet TLVs are defined, for including the cryptographic signature of a packet, and for including the timestamp indicating the time at which the cryptographic signature was calculated. 8.1. Packet SIGNATURE TLV A Packet SIGNATURE TLV is an example of a SIGNATURE TLV as described in Section 5. When calculating the for a Packet, the signature is calculated over the entire Packet, including the packet header, all Packet TLVs (other than Packet SIGNATURE TLVs) and all included Messages and their message headers. 8.1.1. Packet TIMESTAMP TLV A Packet TIMESTAMP TLV is an example of a TIMESTAMP TLV as described in Section 6. 9. IANA Considerations 9.1. TLV Registrations This specification defines two Message TLV types which must be allocated from the 0-127 range of the "Assigned Message TLV Types" repository of [RFC5444] as specified in Table 1 and two Packet TLV types which must be allocated from the 0-127 range of the "Assigned Packet TLV Types" repository of [RFC5444] as specified in Table 2. IANA is requested to assign the same numerical value to the Message TLV and Packet TLV types with the same name. 9.1.1. Expert Review: Evaluation Guidelines For the registries for TLV type extensions where an Expert Review is required, the designated expert SHOULD take the same general recommendations into consideration as are specified by [RFC5444]. Herberg & Clausen Expires January 7, 2010 [Page 7] Internet-Draft MANET Cryptographical Signature TLV July 2009 9.1.2. Message TLV Type Registrations +-----------+------+-----------+------------------------------------+ | Name | Type | Type | Description | | | | Extension | | +-----------+------+-----------+------------------------------------+ | SIGNATURE | TBD1 | 0 | Signature of a message | | | | 1-223 | Expert Review | | | | 224-255 | Experimental Use | | TIMESTAMP | TBD2 | 0 | Timestamp of arbitrary length, | | | | | given by the tlv-length field. The | | | | | MANET routing protocol has to | | | | | define how to interpret this | | | | | timestamp | | | | 1 | 32-bit timestamp representing the | | | | | number of seconds elapsed since | | | | | January 1, 1970 | | | | 2 | NTP timestamp format as defined in | | | | | [RFC4330] | | | | 3-223 | Expert Review | | | | 224-255 | Experimental Use | +-----------+------+-----------+------------------------------------+ Table 1 9.1.3. Packet TLV Type Registrations +-----------+------+-----------+------------------------------------+ | Name | Type | Type | Description | | | | Extension | | +-----------+------+-----------+------------------------------------+ | SIGNATURE | TBD3 | 0 | Signature of a packet. | | | | 1-223 | Expert Review | | | | 224-255 | Experimental Use | | TIMESTAMP | TBD2 | 0 | Timestamp of arbitrary length, | | | | | given by the tlv-length field. The | | | | | MANET routing protocol has to | | | | | define how to interpret this | | | | | timestamp | | | | 1 | 32-bit timestamp representing the | | | | | number of seconds elapsed since | | | | | January 1, 1970. | | | | 2 | NTP timestamp format as defined in | | | | | [RFC4330] | | | | 3-223 | Expert Review | | | | 224-255 | Experimental Use | +-----------+------+-----------+------------------------------------+ Herberg & Clausen Expires January 7, 2010 [Page 8] Internet-Draft MANET Cryptographical Signature TLV July 2009 Table 2 9.2. New IANA registries This document specifies some values where IANA registries are required. 9.2.1. Expert Review: Evaluation Guidelines For the registries for the following tables (OMF) where an Expert Review is required, the designated expert SHOULD take the same general recommendations into consideration as are specified by [RFC5444]. 9.2.2. Hash-Function Registry IANA is requested to create a new registry for the hash functions that can be used when creating a signature. The initial assignments and allocation policies are specified in Table 3. +------------------+-----------+------------------------------------+ | Hash function | Algorithm | Description | | value | | | +------------------+-----------+------------------------------------+ | 0 | MD2 | The hash function is specified in | | | | [RFC1319] | | 1 | MD4 | The hash function is specified in | | | | [RFC1320] | | 2 | MD5 | The hash function is specified in | | | | [RFC1321] | | 3 | SHA1 | The hash function is specified in | | | | [RFC3174] | | 4 | SHA256 | The hash function is specified in | | | | [SHA256] | +------------------+-----------+------------------------------------+ Table 3: Hash-Function registry 9.2.3. Cryptographic Algorithm Registry IANA is requested to create a new registry for the cryptographic cipher function. Initial assignments and allocation policies are specified in Table 4. Herberg & Clausen Expires January 7, 2010 [Page 9] Internet-Draft MANET Cryptographical Signature TLV July 2009 +---------------+-----------+---------------------------------------+ | Cryptographic | Algorithm | Description | | algorithm | | | | value | | | +---------------+-----------+---------------------------------------+ | 0 | none | No cryptographic signature is used. | | | | Only a hash function from Table 3 is | | | | used for the value of the TLV. | | 1 | RSA | RSA is specified in [RSA78]. | | 2 | DSA | DSA is specified in [DSA94]. | +---------------+-----------+---------------------------------------+ Table 4: Cryptographic algorithm registry 10. Security Considerations This document does not provide a protocol itself. However, it provides a syntactical component for cryptographic signatures of messages and packets as defined in [RFC5444]. It can be used to address security issues of a protocol or extension that uses the component specified in this document. As such, it has the same security considerations as [RFC5444]. In addition, a protocol that includes this component MUST specify the usage as well as the security that is attained by the cryptographic signatures of a message or a packet. As an example, a routing protocol that uses this component to reject "badly formed" messages if a control message does not contain a valid signature, should indicate the security assumption that iff the signature is valid, the message is considered valid. It also should indicate the security issues that are counteracted by this measure (e.g. link or identity spoofing) as well as the issues that are not counteracted (e.g. compromised keys, replay attacks). 11. Acknowledgements The authors would like to thank Jerome Milan (Ecole Polytechnique). 12. References 12.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", RFC 2119, BCP 14, March 1997. Herberg & Clausen Expires January 7, 2010 [Page 10] Internet-Draft MANET Cryptographical Signature TLV July 2009 [RFC5444] Clausen, T., Dearlove, C., Dean, J., and C. Adjih, "Generalized MANET Packet/Message Format", RFC 5444, February 2009. 12.2. Informative References [DSA94] "Digital Signature Standard", NIST, FIPS PUB 186 , May 1994. [NHDP] Clausen, T., Dean, J., and C. Dearlove, "MANET Neighborhood Discovery Protocol (NHDP)", work in progress draft-ietf-manet-nhdp-09.txt, March 2009. [OLSRv2] Clausen, T., Dearlove, C., and P. Jacquet, "The Optimized Link State Routing Protocol version 2", work in progress draft-ietf-manet-olsrv2-08.txt, March 2009. [RFC1319] Kaliski, B., "The MD2 Message-Digest Algorithm", RFC 1319, April 1992. [RFC1320] Rivest, R., "The MD4 Message-Digest Algorithm", RFC 1320, April 1992. [RFC1321] Rivest, R., "The MD5 Message-Digest Algorithm", RFC 1321, April 1992. [RFC3174] Eastlake, D. and P. Jones, "US Secure Hash Algorithm 1 (SHA1)", RFC 3174, September 2001. [RFC4330] Mills, D., "Simple Network Time Protocol (SNTP) Version 4 for IPv4, IPv6 and OSI", RFC 4330, January 2006. [RSA78] Rivest, R., Shamir, A., and L. Adleman, "A method for obtaining digital signatures and public-key cryptosystems", Communications of the ACM 21(2):120-126, February 1978. [SHA256] "Secure Hash Algorithm. NIST FIPS 180-2", National Institute of Standards and Technology , August 2002. Appendix A. Examples A.1. Example Signed Message The sample message depicted in Figure 1 is taken from the appendix of [RFC5444]. However, a SIGNATURE Message TLV has been added. It is assumed that the SIGNATURE TLV type is lesser than the TLV type of Herberg & Clausen Expires January 7, 2010 [Page 11] Internet-Draft MANET Cryptographical Signature TLV July 2009 the second message TLV (i.e. it comes first in the order of Message TLVs). The TLV has the thasvalue flags set ('1'). The TLV value represents a 15 octet long signature of the whole message. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0 0 0 0 1 0 0 0| Packet Sequence Number | Message Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1 1 1 1 0 0 0 0|0 0 0 0 0 0 0 0 0 1 0 0 1 0 1 0| Orig Addr | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Originator Address (cont) | Hop Limit | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Hop Count | Message Sequence Number |0 0 0 0 0 0 0 0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0 0 0 1 1 1 0 1| SIGNATURE |0 0 0 1 0 0 0 0| hash-function | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |crypto-function|0 0 0 0 1 1 1 1| Signature Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Signature Value (cont) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Signature Value (cont) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Signature Value (cont) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Sig. Val (cont)| TLV Type |0 0 0 1 0 0 0 0|0 0 0 0 0 1 1 0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Value (cont) |0 0 0 0 0 0 1 0|0 0 1 1 0 0 0 0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0 0 0 0 0 0 1 0| Mid | Mid | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Mid (cont) | Prefix Length |0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0 0 0 0 0 0 1 1|1 0 0 0 0 0 0 0|0 0 0 0 0 0 1 0| Head | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Head (cont) | Mid | Mid | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Mid (cont) | Mid |0 0 0 0 0 0 0 0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0 0 0 0 1 0 0 1| TLV Type |0 0 0 1 0 0 0 0|0 0 0 0 0 0 1 0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Value | TLV Type |0 0 1 0 0 0 0 0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Index Start | Index Stop | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Herberg & Clausen Expires January 7, 2010 [Page 12] Internet-Draft MANET Cryptographical Signature TLV July 2009 Figure 1: Example message with signature Authors' Addresses Ulrich Herberg LIX, Ecole Polytechnique 91128 Palaiseau Cedex, France Phone: +33-1-6933-4126 Email: ulrich@herberg.name URI: http://www.herberg.name/ Thomas Heide Clausen LIX, Ecole Polytechnique 91128 Palaiseau Cedex, France Phone: +33 6 6058 9349 Email: T.Clausen@computer.org URI: http://www.thomasclausen.org/ Herberg & Clausen Expires January 7, 2010 [Page 13]