--- 1/draft-ietf-dhc-sedhcpv6-00.txt 2014-02-14 00:14:36.534351881 -0800 +++ 2/draft-ietf-dhc-sedhcpv6-01.txt 2014-02-14 00:14:36.574352837 -0800 @@ -1,19 +1,21 @@ -DHC Working Group S. Jiang +DHC Working Group S. Jiang, Ed. Internet-Draft Huawei Technologies Co., Ltd Intended status: Standards Track S. Shen -Expires: May 25, 2014 CNNIC - November 21, 2013 +Expires: August 18, 2014 CNNIC + D. Zhang + Huawei Technologies Co., Ltd + February 14, 2014 Secure DHCPv6 with Public Key - draft-ietf-dhc-sedhcpv6-00 + draft-ietf-dhc-sedhcpv6-01 Abstract The Dynamic Host Configuration Protocol for IPv6 (DHCPv6) enables DHCPv6 servers to pass configuration parameters. It offers configuration flexibility. If not secured, DHCPv6 is vulnerable to various attacks, particularly spoofing attacks. This document analyzes the security issues of DHCPv6 and specifies a Secure DHCPv6 mechanism for communication between DHCPv6 client and server. This mechanism is based on public/private key pairs. The authority of the @@ -28,62 +30,63 @@ 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 25, 2014. + This Internet-Draft will expire on August 18, 2014. Copyright Notice - Copyright (c) 2013 IETF Trust and the persons identified as the + 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 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 2. Requirements Language and Terminology . . . . . . . . . . . . 3 3. Security Overview of DHCPv6 . . . . . . . . . . . . . . . . . 3 4. Secure DHCPv6 Overview . . . . . . . . . . . . . . . . . . . 4 4.1. New Components . . . . . . . . . . . . . . . . . . . . . 5 4.2. Support for algorithm agility . . . . . . . . . . . . . . 5 - 5. Extensions for Secure DHCPv6 . . . . . . . . . . . . . . . . 5 + 5. Extensions for Secure DHCPv6 . . . . . . . . . . . . . . . . 6 5.1. Public Key Option . . . . . . . . . . . . . . . . . . . . 6 5.2. Certificate Option . . . . . . . . . . . . . . . . . . . 6 5.3. Signature Option . . . . . . . . . . . . . . . . . . . . 7 - 6. Processing Rules and Behaviors . . . . . . . . . . . . . . . 8 - 6.1. Processing Rules of Sender . . . . . . . . . . . . . . . 8 - 6.2. Processing Rules of Recipient . . . . . . . . . . . . . . 9 - 6.3. Processing Rules of Relay Agent . . . . . . . . . . . . . 10 - 6.4. Timestamp Check . . . . . . . . . . . . . . . . . . . . . 10 - 7. Security Considerations . . . . . . . . . . . . . . . . . . . 12 - 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 - 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 14 - 10. Change log [RFC Editor: Please remove] . . . . . . . . . . . 14 - 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 14 - 11.1. Normative References . . . . . . . . . . . . . . . . . . 14 - 11.2. Informative References . . . . . . . . . . . . . . . . . 15 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 + 5.4. Status Codes . . . . . . . . . . . . . . . . . . . . . . 9 + 6. Processing Rules and Behaviors . . . . . . . . . . . . . . . 9 + 6.1. Processing Rules of Sender . . . . . . . . . . . . . . . 9 + 6.2. Processing Rules of Recipient . . . . . . . . . . . . . . 10 + 6.3. Processing Rules of Relay Agent . . . . . . . . . . . . . 11 + 6.4. Timestamp Check . . . . . . . . . . . . . . . . . . . . . 12 + 7. Security Considerations . . . . . . . . . . . . . . . . . . . 13 + 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 + 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15 + 10. Change log [RFC Editor: Please remove] . . . . . . . . . . . 16 + 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 + 11.1. Normative References . . . . . . . . . . . . . . . . . . 16 + 11.2. Informative References . . . . . . . . . . . . . . . . . 16 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17 1. Introduction The Dynamic Host Configuration Protocol for IPv6 (DHCPv6, [RFC3315]) enables DHCPv6 servers to pass configuration parameters. It offers configuration flexibility. If not secured, DHCPv6 is vulnerable to various attacks, particularly spoofing attacks. This document analyzes the security issues of DHCPv6 in details. This document provides mechanisms for improving the security of @@ -222,24 +225,29 @@ the future with existing hash algorithms, as recommended in [RFC4270], this document provides a mechanism for negotiating the use of more secure hashes in the future. In addition to hash algorithm agility, this document also provides a mechanism for signature algorithm agility. The support for algorithm agility in this document is mainly a unilateral notification mechanism from sender to recipient. If the recipient does not support the algorithm used by the sender, it - cannot authenticate the message. Senders in a same administrative - domain are not required to upgrade to a new algorithm simultaneously. + cannot authenticate the message. In this case, the receiver SHOULD + reply with a NotSupportAlgorithm status code (defined in + Section 5.4). Upon receiving this status code, the sender MAY resend + the message protected with the mandatory algorithms (defined in + Section 5.3). Therefore, the senders in a same administrative domain + may be allowed to use various algorithms simultaneously. 5. Extensions for Secure DHCPv6 + This section extends DHCPv6. Three new options have been defined. The new options MUST be supported in the Secure DHCPv6 message exchange. 5.1. Public Key Option The Public Key option carries the public key of the sender. The format of the Public Key option is described as follows: 0 1 2 3 @@ -276,20 +284,21 @@ . . +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ option-code OPTION_CERT_PARAMETER (TBA2). option-len Length of certificate in octets. Certificate A variable-length field containing certificate. The encoding of certificate and certificate data MUST be in format as defined in Section 3.6, [RFC5996]. + The support of X.509 certificate is mandatory. 5.3. Signature Option The Signature option allows public key-based signatures to be attached to a DHCPv6 message. The Signature option could be any place within the DHCPv6 message. It protects the entire DHCPv6 header and options, except for the Authentication Option. The format of the Signature option is described as follows: 0 1 2 3 @@ -308,30 +317,32 @@ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ option-code OPTION_SIGNATURE (TBA3). option-len 12 + Length of Signature field in octets. HA-id Hash Algorithm id. The hash algorithm is used for computing the signature result. This design is adopted in order to provide hash algorithm agility. The value is from the Hash Algorithm for Secure - DHCPv6 registry in IANA. The initial values are - assigned for SHA-1 is 0x0001. + DHCPv6 registry in IANA. The support of SHA-256 is + mandatory. A registry of the initial assigned values + is defined in Section 8. SA-id Signature Algorithm id. The signature algorithm is used for computing the signature result. This design is adopted in order to provide signature algorithm agility. The value is from the Signature Algorithm for Secure DHCPv6 registry in IANA. The - initial values are assigned for RSASSA-PKCS1-v1_5 - is 0x0001. + support of RSASSA-PKCS1-v1_5 is mandatory. A + registry of the initial assigned values is defined + in Section 8. Timestamp The current time of day (NTP-format timestamp [RFC5905] in UTC (Coordinated Universal Time), a 64-bit unsigned fixed-point number, in seconds relative to 0h on 1 January 1900.). It can reduce the danger of replay attacks. Signature A variable-length field containing a digital signature. The signature value is computed with the hash algorithm and the signature algorithm, @@ -352,20 +363,32 @@ SA-id field. Note: if both signature and authentication option are presented, signature option does not protect authentication option. It is because both needs to apply hash algorithm to whole message, so there must be a clear order and there could be only one last-created option. In order to avoid update RFC3315 because of changing auth option, the authors chose not include authentication option in the signature. +5.4. Status Codes + + o NotSupportAlgorithm (TBD4): Indicates the recipient does not + support algorthims that sender used. + + o NotSupportFaithModel (TBD5): Indicates the recipient does not + support the leap of faith model. + + o FaithListExceed (TBD6): Indicates the recipient's list that stores + public keys or unverifiable certificates in the leap of faith + model currently exceeds. + 6. Processing Rules and Behaviors 6.1. Processing Rules of Sender The sender of a Secure DHCPv6 message could be a DHCPv6 server or a DHCPv6 client. The node must have a public/private key pair in order to create Secure DHCPv6 messages. The node may have a certificate which is signed by a CA trusted by both sender and recipient. @@ -382,47 +405,79 @@ messages, MUST contain the Signature option, which MUST be constructed as explained in Section 5.3. It protects the message header and the message payload and all DHCPv6 options except for the Signature option itself and the Authentication Option. Within the Signature option the Timestamp field SHOULD be set to the current time, according to sender's real time clock. A Relay-forward and relay-reply message MUST NOT contain any Public Key or Certificate option or Signature Option. + Upon receiving a Reply message with a NotSupportAlgorithm status + code, the sender MAY resend the message protected with the mandatory + algorithms. + + Upon receiving a Reply message with a NotSupportFaithModel or + FaithListExceed status code, the sender is not able to build up the + connection with the recipient. The sender MAY swith to a verifiable + certificate. In the latter case, the sender MAY retry later. + 6.2. Processing Rules of Recipient When receiving a DHCPv6 message, except for Relay-Forward and Relay- Reply messages, a Secure DHCPv6 enabled recipient SHOULD discard the DHCPv6 message if the Signature option is absent, or both the Public Key and Certificate option is absent, or both the Public Key and Certificate option are presented. If all three options are absent, the recipient MAY fall back the unsecure DHCPv6 model. - The recipient SHOULD first check the authority of this sender. If - the sender uses a public key, the recipient SHOULD validate it by + The recipient SHOULD first check the support of algorthims that + sender used. If not, an error NotSupportAlgorithm status code should + be sent back to the sender, while the message is dropped siliently. + If all algorthims are supported, the recipient then checks the + authority of this sender. + + If the sender uses certificate, the recipient SHOULD validate the + sender's certificate following the rules defined in [RFC5280]. An + implementation may create a local trust certificate record for a + verified certificate in order to avoid repeated verfication procedure + in the future. A sender certificate that finds a match in the local + trust certificate list are treated as verified. A fast search index + may be created for this list. + + If the sender uses a public key, the recipient SHOULD validate it by finding a match public key from the local trust public key list, which is pre-configured or recorded from previous communications. A local trust public key list is a data table maintained by the recipient. It restores public keys from all trustworthy senders. A - fast search index may be created for this data table. If the sender - uses certificate, the recipient SHOULD validate the sender's - certificate following the rules defined in [RFC5280]. An - implementation may then create a local trust certificate record. + fast search index may be created for this list. The recipient may choose to further process the message from a sender - for which no authorization information exists. By recording the key - that was used by the sender, when the first time it is seen, the - recipient can make a leap of faith that the sender is trustworthy. - If no evidence to the contrary surfaces, the recipient can then - validate the sender as trustworthy when it subsequently sees the same - key used to sign messages from the same server. + for which no authorization information exists, either non-matched + public key or certificate cannot be verified. By recording the + public key or unverifiable certificate that was used by the sender, + when the first time it is seen, the recipient can make a leap of + faith that the sender is trustworthy. If no evidence to the contrary + surfaces, the recipient can then validate the sender as trustworthy + when it subsequently sees the same public key or certificate used to + sign messages from the same sender. If the recipient does not + support the leap of faith model, it SHOULD reply a message with an + error NotSupportFaithModel status code, defined in Section 5.4, back + to the sender. + + The number of cached public keys or unverifiable certificates MUST be + limited in order to protect the DHCPv6 server against resource + exhaustion attacks. If the recipient's list that stores public keys + or unverifiable certificates in the leap of faith model exceeds, an + error FaithListExceed status code SHOULD be returned to the sender. + The resource releasing policy against exceeding situations is out of + scope. At this point, the recipient has either recognized the authorization of the sender, or decided to attempt a leap of faith. The recipient MUST now authenticate the sender by verifying the Signature and checking timestamp. The order of two procedures is left as an implementation decision. It is RECOMMENDED to check timestamp first, because signature verification is much more computationally expensive. The signature field verification MUST show that the signature has @@ -536,104 +591,124 @@ The Secure DHCPv6 mechanism is based on the pre-condition that the recipient knows the public key of senders or the sender's certificate can be verified through a trust CA. It prevents DHCPv6 server spoofing. The clients may decline the DHCPv6 messages from unknown/ unverified servers, which may be fake servers; or may prefer DHCPv6 messages from known/verified servers over unsigned messages or messages from unknown/unverified servers. The pre-configuration operation also needs to be protected, which is out of scope. The deployment of PKI is also out of scope. - However, when a DHCPv6 client first encounters a new public key or - new unverified certificate, it can make a leap of faith. If the - DHCPv6 server that used that public key or certificate is in fact - legitimate, then all future communication with that DHCPv6 server can - be protected by caching the public key. This does not provide - complete security, but it limits the opportunity to mount an attack - on a specific DHCPv6 client to the first time it communicates with a - new DHCPv6 server. + However, when a DHCPv6 client first encounters a new public key or a + new unverifiable certificate, it can make a leap of faith. If the + DHCPv6 server that used that public key or unverifiable certificate + is in fact legitimate, then all future communication with that DHCPv6 + server can be protected by storing the public key or unverifiable + certificate. This does not provide complete security, but it limits + the opportunity to mount an attack on a specific DHCPv6 client to the + first time it communicates with a new DHCPv6 server. The number of + cached public keys or unverifiable certificates MUST be limited in + order to protect the DHCPv6 server against resource exhaustion + attacks. Downgrade attacks cannot be avoided if nodes are configured to accept both secured and unsecured messages. A future specification may provide a mechanism on how to treat unsecured DHCPv6 messages. [RFC6273] has analyzed possible threats to the hash algorithms used in SEND. Since the Secure DHCPv6 defined in this document uses the same hash algorithms in similar way to SEND, analysis results could be applied as well: current attacks on hash functions do not constitute any practical threat to the digital signatures used in the signature algorithm in the Secure DHCPv6. A window of vulnerability for replay attacks exists until the timestamp expires. Secure DHCPv6 nodes are protected against replay attacks as long as they cache the state created by the message containing the timestamp. The cached state allows the node to protect itself against replayed messages. However, once the node flushes the state for whatever reason, an attacker can re-create the state by replaying an old message while the timestamp is still valid. + In addition, the effectiveness of timestamps is largely dependent + upon the accuracy of synchronization between communicating nodes. + However, the two communciating nodes can be synchronized is out of + scope of this work. Attacks against time synchronization protocols such as NTP [RFC5905] may cause Secure DHCPv6 nodes to have an incorrect timestamp value. This can be used to launch replay attacks, even outside the normal window of vulnerability. To protect against these attacks, it is recommended that Secure DHCPv6 nodes keep independently maintained clocks or apply suitable security measures for the time synchronization protocols. 8. IANA Considerations This document defines three new DHCPv6 [RFC3315] options. The IANA is requested to assign values for these three options from the DHCP - Option Codes table of the DHCPv6 Parameters registry. The three - options are: + Option Codes table of the DHCPv6 Parameters registry maintained in + http://www.iana.org/assignments/dhcpv6-parameters. The three options + are: The Public Key Option (TBA1), described in Section 5.1. The Certificate Option (TBA2), described in Section 5.2. The Signature Option (TBA3), described in Section 5.3. The IANA is also requested to add two new registry tables to the - DHCPv6 Parameters registry. The two tables are the Hash Algorithm + DHCPv6 Parameters registry maintained in http://www.iana.org/ + assignments/dhcpv6-parameters. The two tables are the Hash Algorithm for Secure DHCPv6 table and the Signature Algorithm for Secure DHCPv6 table. Initial values for these registries are given below. Future assignments are to be made through Standards Action [RFC5226]. Assignments for each registry consist of a name, a value and a RFC number where the registry is defined. Hash Algorithm for Secure DHCPv6. The values in this table are 16-bit unsigned integers. The following initial values are assigned for Hash Algorithm for Secure DHCPv6 in this document: Name | Value | RFCs - -------------------+---------+------------ + -------------------+---------+-------------- Reserved | 0x0000 | this document SHA-1 | 0x0001 | this document SHA-256 | 0x0002 | this document + SHA-512 | 0x0003 | this document Signature Algorithm for Secure DHCPv6. The values in this table are 16-bit unsigned integers. The following initial values are assigned for Signature Algorithm for Secure DHCPv6 in this document: Name | Value | RFCs - -------------------+---------+------------ + -------------------+---------+-------------- Reserved | 0x0000 | this document RSASSA-PKCS1-v1_5 | 0x0001 | this document + IANA is requested to assign the following new DHCPv6 Status Codes, + defined in Section 5.4, in the DHCPv6 Parameters registry maintained + in http://www.iana.org/assignments/dhcpv6-parameters: + + Code | Name | Reference + ---------+----------------------+-------------- + TBD4 | NotSupportAlgorithm | this document + TBD5 | NotSupportFaithModel | this document + TBD6 | FaithListExceed | this document + 9. Acknowledgements The authors would like to thank Bernie Volz, Ted Lemon, Ralph Droms, Jari Arkko, Sean Turner, Stephen Kent, Thomas Huth, David Schumacher, - Dacheng Zhang, Francis Dupont, Tomek Mrugalski, Gang Chen and other - members of the IETF DHC working groups for their valuable comments. + Francis Dupont, Tomek Mrugalski, Gang Chen and other members of the + IETF DHC working groups for their valuable comments. This document was produced using the xml2rfc tool [RFC2629]. 10. Change log [RFC Editor: Please remove] draft-ietf-dhc-sedhcpv6-00: adopted by DHC WG. 2013-11-19. draft-jiang-dhc-sedhcpv6-02: removed protection between relay agent and server due to complexity, following the comments from Ted Lemon, Bernie Volz. 2013-10-16. @@ -687,24 +762,33 @@ [RFC6273] Kukec, A., Krishnan, S., and S. Jiang, "The Secure Neighbor Discovery (SEND) Hash Threat Analysis", RFC 6273, June 2011. [RSA] RSA Laboratories, "RSA Encryption Standard, Version 2.1, PKCS 1", November 2002. Authors' Addresses - Sheng Jiang + Sheng Jiang (editor) Huawei Technologies Co., Ltd Q14, Huawei Campus, No.156 Beiqing Road Hai-Dian District, Beijing, 100095 P.R. China Email: jiangsheng@huawei.com + Sean Shen CNNIC 4, South 4th Street, Zhongguancun Beijing 100190 P.R. China Email: shenshuo@cnnic.cn + + Dacheng Zhang + Huawei Technologies Co., Ltd + Q14, Huawei Campus, No.156 Beiqing Road + Hai-Dian District, Beijing, 100095 + P.R. China + + Email: zhangdacheng@huawei.com