DHC working group S. Nalluri Internet-Draft Ericsson Intended status: Standards Track December 26, 2016 Expires: June 11, 2017 DHCPv6 Options for LWM2M bootstrap information draft-nalluri-dhc-dhcpv6-lwm2m-bootstrap-options-00 Abstract This document defines Dynamic Host Configuration Protocol and Dynamic Host Configuration Protocol version 6 (DHCPv6) Options for LWM2M client bootstrap information, which are used to carry Uniform Resource Locater of LWM2M bootstrap server and certificate that validates the public key presented by server. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. 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/. 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Nalluri Expires June 11, 2017 [Page 1] Internet-Draft DHCPv6 Options for LWM2M December 2016 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2 3. LWM2M bootstrap server information through DHC . . . . . . . 3 3.1. DHCPv6 option for LWM2M bootstrap server URI . . . . . . 3 3.2. DHCPv6 option for LWM2M server certificate . . . . . . . 3 3.3. DHCP option for LWM2M bootstrap server URI . . . . . . . 4 3.4. DHCP option for LWM2M server certificate . . . . . . . . 4 4. Appearance of Option . . . . . . . . . . . . . . . . . . . . 5 4.1. Appearance of options in DHCPv6 control messages . . . . 5 4.2. Appearance of options in DHCP control messages . . . . . 6 5. Configuration Guidelines for the Server . . . . . . . . . . . 6 6. DHCP/DHCPv6 Client Behavior . . . . . . . . . . . . . . . . . 6 7. Relay agent Behavior . . . . . . . . . . . . . . . . . . . . 7 8. Security Considerations . . . . . . . . . . . . . . . . . . . 7 9. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 8 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 11. Normative References . . . . . . . . . . . . . . . . . . . . 8 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 9 1. Introduction Light weight machine to machine (LWM2M) protocol is used to manage end device life cycle in machine to machine communication scenarios. LWM2M device bootstrap is an optional life cycle phase for devices to get needed information when starting up for first time. Information gathered during bootstrapping might include management server details and security certificates required to establish connectivity with management server. Information required to connect with bootstrap server might be hard coded during device manufacturing phase. Hard coding configuration by device manufacturer forces device operator to use same configuration as hard coded. It is possible that reachability information of bootstrap server that is hard coded may be outdated and boot strap server reachability might fail during first use of device. In such cases connectivity with bootstrap server is possible only through device software upgrade. 2. Terminology This document makes use of the following terms: LWM2M: Lightweight Machine to Machine is a protocol from Open Mobile alliance for device management in M2M or Internet of Things scenarios Nalluri Expires June 11, 2017 [Page 2] Internet-Draft DHCPv6 Options for LWM2M December 2016 LWM2M bootstrap server: The server that provides LWM2M bootstrap interface which is used to optionally configure a LWM2M Client so that it can successfully register with a LWM2M management Server LWM2M management server: The server that provides registration, device management and service enablement interface to manage a LWM2M client. 3. LWM2M bootstrap server information through DHC LWM2M bootstrap server details like URI and security certificate can be collected during dynamic host configuration phase. DHCP and DHCPv6 options can be extended to collect LWM2M bootstrap server information for IPv4 and IPv6 networks respectively. DHCP or DHCPv6 client requests LWM2M bootstrap server URI and LWM2M server certificate using new options proposed in sections below 3.1. DHCPv6 option for LWM2M bootstrap server URI DHCPv6 option OPTION_LWM2M_BOOTSTRAP_URI conveys URI through which LWM2M client can reach LWM2M bootstrap server reachable through IPv6 network. The format of LWM2M bootstrap server URI option is as shown below: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | option-code | option-len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LWM2M-bootstrap-URI | | ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ option-code: OPTION_LWM2M_BOOTSTRAP_URI option-len: Length of the 'LWM2M-bootstrap-URI' field in octets LWM2M-bootstrap-URI: This string is URI of LWM2M bootstrap server. The string is not null-terminated. 3.2. DHCPv6 option for LWM2M server certificate DHCPv6 option OPTION_LWM2M_SERVER_CERTIFICATE conveys security certificate which can be used by LWM2M client to establish secure connection with LWM2M server reachable through IPv6 network. The format of LWM2M server certificate option is as shown below: Nalluri Expires June 11, 2017 [Page 3] Internet-Draft DHCPv6 Options for LWM2M December 2016 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | option-code | option-len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LWM2M-server-certificate | | (variable length data) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ option-code: OPTION_LWM2M_SERVER_CERTIFICATE option-len: Length of the 'LWM2M-server-certificate' field in octets LWM2M-server-certificate: Digital certificate of LWM2M server as defined in Section 3.6 of [RFC7296] 3.3. DHCP option for LWM2M bootstrap server URI DHCP option OPTION_LWM2M_BOOTSTRAP_URI conveys URI through which LWM2M client can reach LWM2M bootstrap server reachable through IPv4 network. The format of LWM2M bootstrap server URI option is as shown below: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | option-code | option-len | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | LWM2M-bootstrap-URI | | ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ option-code: OPTION_LWM2M_BOOTSTRAP_URI option-len: Length of the 'LWM2M-bootstrap-URI' field in octets Reserved: MUST be set to zero LWM2M-bootstrap-URI: This string is URI of LWM2M bootstrap server. The string is not null-terminated. 3.4. DHCP option for LWM2M server certificate DHCP option OPTION_LWM2M_SERVER_CERTIFICATE conveys security certificate which can be used by LWM2M client to establish secure Nalluri Expires June 11, 2017 [Page 4] Internet-Draft DHCPv6 Options for LWM2M December 2016 connection with LWM2M server reachable through IPv4 network. The format of LWM2M server certificate option is as shown below: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | option-code | option-len | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | LWM2M-server-certificate | | (variable length data) | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ option-code: OPTION_LWM2M_SERVER_CERTIFICATE option-len: Length of the 'LWM2M-server-certificate' field in octets Sequence Number: Sequence number of OPTION_LWM2M_SERVER_CERTIFICATE in the scope of DHCP packet. Sequence number starts with zero and incremented by 1 for every new OPTION_LWM2M_SERVER_CERTIFICATE option added to DHCP packet LWM2M-server-certificate: Digital certificate of LWM2M server as defined in Section 3.6 of [RFC7296] 4. Appearance of Option 4.1. Appearance of options in DHCPv6 control messages The OPTION_LWM2M_BOOTSTRAP_URI and OPTION_LWM2M_SERVER_CERTIFICATE options MUST NOT appear in messages other than the following: SOLICIT (1), ADVERTISE (2), REQUEST (3),REPLY (4) RENEW (5), REBIND (6), INFORMATION-REQUEST (11). If this option appears in messages other than those specified above, the receiver MUST ignore it. The option number for OPTION_LWM2M_BOOTSTRAP_URI and OPTION_LWM2M_SERVER_CERTIFICATE options MAY appear in the "Option Request" option [RFC3315] in the following messages: SOLICIT (1), REQUEST (3), RENEW (5), REBIND (6), INFORMATION-REQUEST (11) and RECONFIGURE (10). If this option number appears in the "Option Request" option in messages other than those specified above, the receiver SHOULD ignore it. Nalluri Expires June 11, 2017 [Page 5] Internet-Draft DHCPv6 Options for LWM2M December 2016 4.2. Appearance of options in DHCP control messages The OPTION_LWM2M_BOOTSTRAP_URI and OPTION_LWM2M_SERVER_CERTIFICATE options MUST NOT appear in messages other than the following: DHCPDISCOVER (1), DHCPOFFER (2), DHCPREQUEST (3), DHCPACK (5) and DHCPINFORM (8). If this option appears in messages other than those specified above, the receiver MUST ignore it. The option number for OPTION_LWM2M_BOOTSTRAP_URI and OPTION_LWM2M_SERVER_CERTIFICATE options MAY appear in the "Parameter Request List" option [RFC2132] in the following messages: DHCPDISCOVER (1), DHCPOFFER (2), DHCPREQUEST (3), DHCPACK (5) and DHCPINFORM (8). If this option number appears in the "Parameter Request List" option in messages other than those specified above, the receiver SHOULD ignore it. Maximum possible value of DHCP "option-len" is 255. LWM2M-server- certificate MAY be of length more than 255. To accommodate larger certificate, it SHOULD be possible to include multiple OPTION_LWM2M_SERVER_CERTIFICATE options in same DHCP message. DHCP server SHOULD be capable of including multiple OPTION_LWM2M_SERVER_CERTIFICATE options in same message. Certificates larger than 255 byte SHOULD be fragmented and adjusted in minimum possible number of OPTION_LWM2M_SERVER_CERTIFICATE options. Each OPTION_LWM2M_SERVER_CERTIFICATE option is tagged with a sequence number which can be used by DHCP client to reassemble received certificate 5. Configuration Guidelines for the Server DHCP or DHCPv6 server that supports OPTION_LWM2M_BOOTSTRAP_URI and OPTION_LWM2M_SERVER_CERTIFICATE SHOULD be configured with one and only one LWM2M bootstrap server URI, and one and only one certificate that validates bootstrap server's public key. In the absence of URI configuration, DHCP server SHOULD ignore option OPTION_LWM2M_BOOTSTRAP_URI, and SHOULD continue processing of DHCP control message In the absence of certificate configuration, DHCP server SHOULD ignore option OPTION_LWM2M_SERVER_CERTIFICATE, and SHOULD continue processing of DHCP control message 6. DHCP/DHCPv6 Client Behavior DHCP or DHCPv6 client MAY decide need for inclusion of OPTION_LWM2M_BOOTSTRAP_URI and OPTION_LWM2M_SERVER_CERTIFICATE options in DHCP or DHCPv6 control messages if device is capable of Nalluri Expires June 11, 2017 [Page 6] Internet-Draft DHCPv6 Options for LWM2M December 2016 supporting LWM2M client functionality irrespective of state of LWM2M client. It is possible that LWM2M client MAY not be active before DHCP or DHCPv6 message exchanges happens. In such scenario, DHCP or DHCPv6 client MAY collect LWM2M bootstrap server URI and LWM2M server certificate and keep ready for LWM2M client initialization DHCP or DHCPv6 client MAY prefer collecting LWM2M bootstrap server URI and LWM2M server certificate by including OPTION_LWM2M_BOOTSTRAP_URI and OPTION_LWM2M_SERVER_CERTIFICATE options in DHCPINFORM or INFORMATION-REQUEST message which MAY be send during LWM2M client initialization LWM2M client devices running with IPv6 stack MAY use stateless auto address configuration to get IPv6 address. Such clients MAY use DHCPv6 INFORMATION-REQUEST to get LWM2M bootstrap URI and LWM2M server server certificate through options OPTION_LWM2M_BOOTSTRAP_URI and OPTION_LWM2M_SERVER_CERTIFICATE 7. Relay agent Behavior This draft does not impose any new requirements on DHCP or DHCPv6 relay agent functionality 8. Security Considerations OPTION_LWM2M_BOOTSTRAP_URI and OPTION_LWM2M_SERVER_CERTIFICAT options could be used by an intruder to advertise the URI of a malicious LWM2M bootstrap server and certificate and can alter the LWM2M management server details provided to LWM2M client. The consequences of such an attack can be critical, because any data that is reported by LWM2M client MAY reach unwanted LWM2M management server. As an example, an attacker could collect data from secure locations by deploying malicious servers. To prevent these attacks, it is strongly advisable to secure the use of this option by either: o Using authenticated DHCP as described in [RFC3315], Section 21. o Using options OPTION_LWM2M_BOOTSTRAP_URI and OPTION_LWM2M_SERVER_CERTIFICATE only with trusted DHCP server The security considerations documented in [RFC3315] are to be considered. Nalluri Expires June 11, 2017 [Page 7] Internet-Draft DHCPv6 Options for LWM2M December 2016 9. Acknowledgement Particular thanks to A. Keraenen, J. Jimenez, J. Melen and S. Krishnan for the concept, inputs and review. 10. IANA Considerations IANA is requested to assign new DHCPv6 option codes in the registry maintained in http://www.iana.org/assignments/dhcpv6-parameters: | Option Name | Value | |---------------------------------+----------| | OPTION_LWM2M_BOOTSTRAP_URI | TBA | | OPTION_LWM2M_SERVER_CERTIFICATE | TBA | IANA is requested to assign new DHCP option codes in the registry maintained in http://www.iana.org/assignments/bootp-dhcp-parameters: | Option Name | Value | |--------------------------------+---------| | OPTION_LWM2M_BOOTSTRAP_URI | TBA | | OPTION_LWM2M_SERVER_CERTIFICATE| TBA | 11. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC2131] Droms, R., "Dynamic Host Configuration Protocol", RFC 2131, DOI 10.17487/RFC2131, March 1997, . [RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor Extensions", RFC 2132, DOI 10.17487/RFC2132, March 1997, . [RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins, C., and M. Carney, "Dynamic Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July 2003, . [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., Housley, R., and W. Polk, "Internet X.509 Public Key Infrastructure Certificate and Certificate Revocation List (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, . Nalluri Expires June 11, 2017 [Page 8] Internet-Draft DHCPv6 Options for LWM2M December 2016 [RFC7227] Hankins, D., Mrugalski, T., Siodelski, M., Jiang, S., and S. Krishnan, "Guidelines for Creating New DHCPv6 Options", BCP 187, RFC 7227, DOI 10.17487/RFC7227, May 2014, . [RFC7296] Kaufman, C., Hoffman, P., Nir, Y., Eronen, P., and T. Kivinen, "Internet Key Exchange Protocol Version 2 (IKEv2)", STD 79, RFC 7296, DOI 10.17487/RFC7296, October 2014, . Author's Address Srinivas Rao Nalluri Ericsson Bangalore India Email: srinivasa.rao.nalluri@ericsson.com Nalluri Expires June 11, 2017 [Page 9]