opsec F. Gont Internet-Draft UTN-FRH / SI6 Networks Intended status: Best Current Practice W. Liu Expires: January 5, 2015 Huawei Technologies R. Bonica Juniper Networks July 4, 2014 Recommendations on filtering of IPv6 packets containing IPv6 Extension Headers draft-gont-opsec-ipv6-eh-filtering-00.txt Abstract This document document provides advice on the filtering of IPv6 packets based on the IPv6 Extension Headers and the IPv6 options they contain. Additionally, it discusses the operational and interoperability implications of dropping packets based on the IPv6 Extension Headers and IPv6 options they contain. 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/. 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 January 5, 2015. Copyright 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 carefully, as they describe your rights and restrictions with respect Gont, et al. Expires January 5, 2015 [Page 1] Internet-Draft Filtering of IPv6 packets with EHs July 2014 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 and Conventions Used in This Document . . . . 3 2. IPv6 Extension Headers . . . . . . . . . . . . . . . . . . . 3 2.1. General Discussion . . . . . . . . . . . . . . . . . . . 3 2.2. General Security Implications . . . . . . . . . . . . . . 3 2.3. Advice on the Handling of IPv6 Packets with Specific IPv6 Extension Headers . . . . . . . . . . . . . . . . . . . . 3 3. IPv6 Options . . . . . . . . . . . . . . . . . . . . . . . . 10 3.1. General Discussion . . . . . . . . . . . . . . . . . . . 10 3.2. General Security Implications of IPv6 Options . . . . . . 10 3.3. Advice on the Handling of Packets with Specific IPv6 Options . . . . . . . . . . . . . . . . . . . . . . . . . 11 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22 5. Security Considerations . . . . . . . . . . . . . . . . . . . 22 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 22 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 22 7.1. Normative References . . . . . . . . . . . . . . . . . . 22 7.2. Informative References . . . . . . . . . . . . . . . . . 24 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 25 1. Introduction This document document discusses the filtering of IPv6 packets based on the IPv6 Extension Headers and the IPv6 options they contain. Since various protocols may use IPv6 Extension Headers (possibly with IPv6 options), dropping packets based on the the IPv6 Extension Headers or IPv6 options they contain may have implications on the proper functioning of such protocols. Thus, this document attempts to discuss the operational and interoperability implications of such dropping, and provide advice in this area. Additionally, it outlines what an administrator should do in a typical enterprise environments. This document is similar in nature to [RFC7123], which addresses the same problem for the IPv4 case. Section 2 of this document discusses IPv6 extension headers and IPv6 options, and provides advice in the area of filtering IPv6 packets that contain such IPv6 Extension Headers and/or options. Gont, et al. Expires January 5, 2015 [Page 2] Internet-Draft Filtering of IPv6 packets with EHs July 2014 1.1. Terminology and Conventions Used in This Document The terms "fast path", "slow path", and associated relative terms ("faster path" and "slower path") are loosely defined as in Section 2 of [RFC6398]. 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 [RFC2119]. 2. IPv6 Extension Headers 2.1. General Discussion IPv6 Extension Headers allow for the extension of the IPv6 [RFC2460] protocol. Since both IPv6 Extension Headers and upper-layer protocols share the same namespace ("Next Header" registry/ namespace), [RFC7045] identifies which of the currently assigned Internet Protocol numbers identify IPv6 Extension Headers vs. upper- layer protocols. This document discusses the filtering of packets based on the IPv6 Extension Headers (as specified by [RFC7045]) they contain. . NOTE: [RFC7112] specifies that non-fragmented IPv6 datagrams and Pv6 First-Fragments, must contain the entire IPv6 header chain [RFC7112]. Therefore, intermediate systems can always enforce the filtering policies discussed in this document, or resort to simply dropping the offending packets when they fail to comply with the requirements in [RFC7112]. 2.2. General Security Implications Depending on the specific device architecture, IPv6 packets that contain IPv6 Extension Headers may require processing by the device's general-purpose CPU, and hence can be leveraged for the purpose of Denial of Service (DoS) attacks [Cisco-EH] [FW-Benchmark]. Operators are urged to consider IPv6 Extension Header filtering and IPv6 options handling capabilities of different devices as they make deployment decisions in future. 2.3. Advice on the Handling of IPv6 Packets with Specific IPv6 Extension Headers Gont, et al. Expires January 5, 2015 [Page 3] Internet-Draft Filtering of IPv6 packets with EHs July 2014 2.3.1. IPv6 Hop-by-Hop Option (Number=0) 2.3.1.1. Uses The Hop-by-Hop Options header is used to carry optional information that must be examined by every node along a packet's delivery path. At the time of this writing, the folloing options have been specified for the Hop-by-Hop OPtions extension header: o Router Alert [RFC2711] o Jumbo Payload [RFC2675] o RPL Option [RFC6553] o SMF_DPD [RFC6621] o MPL Option [I-D.ietf-roll-trickle-mcast] o IPv6 DFF Header [RFC6971] 2.3.1.2. Specification This Extension Header is specified in [RFC2460]. 2.3.1.3. Specific Security Implications Since this Extension Header must me processed by all intermediate- systems en route, it can be leveraged to perform Denial of Service attacks against the network infrastructure. 2.3.1.4. Operational and Interoperability Impact if Blocked Dropping of packets containing a Hop-by-Hop Option extension header would break RSVP and multicast deployments. Additionally, it would cause IPv6 jumbograms to be dropped. 2.3.1.5. Advice Intermediate systems should, by default, drop packets containing a IPv6 Hop-by-Hop Option Extension Header. For obvious reasons, RPL routers must not drop packets based on the presence of an IPv6 Hop- by-Hop Option Extension Header. Those intermediate systems processing the contents of this extension header should drop packets that contain more than one instance of the Router Alert option (see [RFC2711]. Gont, et al. Expires January 5, 2015 [Page 4] Internet-Draft Filtering of IPv6 packets with EHs July 2014 2.3.2. Routing Header for IPv6 (Number=43) 2.3.2.1. Uses The Routing header is used by an IPv6 source to list one or more intermediate nodes to be "visited" on the way to a packet's destination. 2.3.2.2. Specification This Extension Header is specified in [RFC2460]. [RFC2460] originally specified the Routing Header Type 0, which has been later obsoleted by [RFC5095]. At the time of this writing, the following Routing Types have been specified: o Type 0: Source Route (DEPRECATED) [RFC2460] [RFC5095] o Type 1: Nimrod (DEPRECATED 2009-05-06) o Type 2: Type 2 Routing Header [RFC6275] o Type 3: RPL Source Route Header [RFC6554] o Types 4-252: Unassigned o Type 253: RFC3692-style Experiment 1 [RFC4727] o Type 254: RFC3692-style Experiment 2 [RFC4727] o Type 255: Reserved 2.3.2.3. Specific Security Implications The security implications of RHT0 have been discussed in detail in [Biondi2007] and [RFC5095]. 2.3.2.4. Operational and Interoperability Impact if Blocked Blocking packets containing a RHT0 has no operational implications. 2.3.2.5. Advice Drop packets containing a RHT0. Gont, et al. Expires January 5, 2015 [Page 5] Internet-Draft Filtering of IPv6 packets with EHs July 2014 2.3.3. Fragment Header for IPv6 (Number=44) 2.3.3.1. Uses This Extension Header provides the fragmentation functionality for IPv6. 2.3.3.2. Specification This Extension Header is specified in [RFC2460]. 2.3.3.3. Specific Security Implications The security implications of the Fragment Header range from Denial of Service attacks (based on blooding a target with IPv6 fragments) to information leakage attacks [I-D.ietf-6man-predictable-fragment-id]. 2.3.3.4. Operational and Interoperability Impact if Blocked Blocking packets that contain a Fragment Header would break any protocols that might rely on fragmentation (e.g., the DNS). 2.3.3.5. Advice Intemmediate systems should, by default, pass packets that contain a Fragment Header. 2.3.4. Encapsulating Security Payload (Number=50) 2.3.4.1. Uses This extension Header is employed for the IPsec suite [RFC4303]. 2.3.4.2. Specification This extension header is specified in [RFC4303]. 2.3.4.3. Specific Security Implications Besides the general implications of IPv6 Extension Headers, this extension header could be employed to potentially perform a DoS attack at the destination system by wasting CPU resources in validating the contents of the packet. Gont, et al. Expires January 5, 2015 [Page 6] Internet-Draft Filtering of IPv6 packets with EHs July 2014 2.3.4.4. Operational and Interoperability Impact if Blocked Dropping packets that employ this extension header would break IPsec deployments. 2.3.4.5. Advice Intemmediate systems should pass packets containing the Encapsulating Security Payload extensio header. 2.3.5. Authentication Header (Number=51) 2.3.5.1. Uses The Authentication Header can be employed for provide authentication services in IPv4 and IPv6. . 2.3.5.2. Specification This Extension Header is specified in [RFC4302]. 2.3.5.3. Specific Security Implications This header could be employed for performing a CPU-consumption attack at the target system. 2.3.5.4. Operational and Interoperability Impact if Blocked Traffic employing the Authentication Header would be dropped. 2.3.5.5. Advice Intermediary systems should not drop packets containing an Authentication Header. 2.3.6. Destination Options for IPv6 (Number=60) 2.3.6.1. Uses The Destination Options header is used to carry optional information that need be examined only by a packet's destination node(s). 2.3.6.2. Specification This Extension Header is specified in [RFC2460]. At the time of this writing, no options have been specified for this extension header. Gont, et al. Expires January 5, 2015 [Page 7] Internet-Draft Filtering of IPv6 packets with EHs July 2014 2.3.6.3. Specific Security Implications No security implications are known, other than the general implications of IPv6 extension headers. 2.3.6.4. Operational and Interoperability Impact if Blocked None. 2.3.6.5. Advice Pass packets that contain the Destination Options Header. 2.3.7. Mobility Header (Number=135) 2.3.7.1. Uses The Mobility Header is an extension header used by mobile nodes, correspondent nodes, and home agents in all messaging related to the creation and management of bindings in Mobile IPv6. 2.3.7.2. Specification This Extension Header is specified in [RFC6275]. 2.3.7.3. Specific Security Implications TBD. 2.3.7.4. Operational and Interoperability Impact if Blocked Dropping packets containing this extension header would break Mobile IPv6. 2.3.7.5. Advice Pass packets containing this extension header. 2.3.8. Host Identity Protocol (Number=139) 2.3.8.1. Uses This extension header is employed with the Host Identity Protocol (HIP), an experimental protocol that allows consenting hosts to securely establish and maintain shared IP-layer state, allowing separation of the identifier and locator roles of IP addresses, thereby enabling continuity of communications across IP address changes. Gont, et al. Expires January 5, 2015 [Page 8] Internet-Draft Filtering of IPv6 packets with EHs July 2014 2.3.8.2. Specification This extension Header is specified in [RFC5201]. 2.3.8.3. Specific Security Implications TBD. 2.3.8.4. Operational and Interoperability Impact if Blocked Dropping packets that contain the Host Identity Protocol would break HIP deployments. 2.3.8.5. Advice Pass packets that contain a Host Identity Protocol extension header. 2.3.9. Shim6 Protocol (Number=140) 2.3.9.1. Uses This extension header is employed by the Shim6 Protocol. 2.3.9.2. Specification This Extension Header is specified in [RFC5533]. 2.3.9.3. Specific Security Implications TBD. 2.3.9.4. Operational and Interoperability Impact if Blocked Dropping packets that contain this extension header would break Shim6. 2.3.9.5. Advice Pass packets containing this extension header. 2.3.10. Use for experimentation and testing (Numbers=253 and 254) 2.3.10.1. Uses . Gont, et al. Expires January 5, 2015 [Page 9] Internet-Draft Filtering of IPv6 packets with EHs July 2014 2.3.10.2. Specification This Extension Header is specified in [RFC3692] and [RFC4727]. 2.3.10.3. Specific Security Implications None. 2.3.10.4. Operational and Interoperability Impact if Blocked . 2.3.10.5. Advice Routers, security gateways, and firewalls SHOULD have configuration knobs for IP packets that contain this extension header to select between "ignore & forward" and "drop & log". Otherwise, no legitimate experiment using these options will be able to traverse any IP router. The aforementioned configuration knob SHOULD default to "drop & log". Special care needs to be taken in the case of "drop & log". Devices SHOULD count the number of packets dropped, but the logging of drop events SHOULD be limited so as to not overburden device resources. 3. IPv6 Options 3.1. General Discussion The following subsections describe specific security implications of different IPv6 options, and provide advice regarding filtering packets that contain such options. 3.2. General Security Implications of IPv6 Options The general security implications of IPv6 options are closely related to those discussed in Section 2.2. Essentially, packets that contain IPv6 options might need to be processed by IPv6 router's general- purpose CPU can be a DDoS risk to that router's general-purpose CPU (and thus to the router itself). For some architectures, a possible mitigation would be to rate-limit the packets that are to be processed by the general-purpose CPU (see e.g. [Cisco-EH]). Gont, et al. Expires January 5, 2015 [Page 10] Internet-Draft Filtering of IPv6 packets with EHs July 2014 3.3. Advice on the Handling of Packets with Specific IPv6 Options The following subsections contain a description of each of the IPv6 options that have so far been specified, a discussion of possible interoperability implications if packets containing such options are dropped, and specific advice on whether to drop packets containing these options in a typical enterprise firewall. 3.3.1. Pad1 (Type=0x00) 3.3.1.1. Uses This option is used when necessary to align subsequent options and to pad out the containing header to a multiple of 8 octets in length. 3.3.1.2. Specification This option is specified in [RFC2460]. 3.3.1.3. Specific Security Implications None. 3.3.1.4. Operational and Interoperability Impact if Blocked Dropping packets that contain this option would potentially break any protocol that relies on IPv6 extension headers. 3.3.1.5. Advice Do not drop packets based on the presence of this option. 3.3.2. PadN (Type=0x01) 3.3.2.1. Uses This option is used when necessary to align subsequent options and to pad out the containing header to a multiple of 8 octets in length. 3.3.2.2. Specification This option is specified in [RFC2460]. 3.3.2.3. Specific Security Implications Because of the possible size of this option, it could be leveraged as a large-bandwidth covert channel. Gont, et al. Expires January 5, 2015 [Page 11] Internet-Draft Filtering of IPv6 packets with EHs July 2014 3.3.2.4. Operational and Interoperability Impact if Blocked Dropping packets that contain this option would potentially break any protocol that relies on IPv6 extension headers. 3.3.2.5. Advice Do not drop packets based on the presence of this option. 3.3.3. Jumbo Payload (Type=0XC2) 3.3.3.1. Uses The Jumbo payload option provides the means of specifying payloads larger than 65535 bytes. 3.3.3.2. Specification This option is specified in [RFC2675]. 3.3.3.3. Specific Security Implications TBD. 3.3.3.4. Operational and Interoperability Impact if Blocked Dropping packets based on the presence would this option would cause IPv6 jumbograms to be dropped. 3.3.3.5. Advice By default, intermediate systems should drop packets that contain this option. This policy could be overiden in specific environments where support for IPv6 jumbograms is desired. 3.3.4. RPL Option (Type=0x63) 3.3.4.1. Uses The RPL Option provides a mechanism to include routing information with each datagram that an RPL router forwards. 3.3.4.2. Specification This option is specified in [RFC6553]. Gont, et al. Expires January 5, 2015 [Page 12] Internet-Draft Filtering of IPv6 packets with EHs July 2014 3.3.4.3. Specific Security Implications TBD. 3.3.4.4. Operational and Interoperability Impact if Blocked This options is meant to be employed within an RPL instance. As a result, dropping packets based on the presence of this option at e.g. an ISP does will not result in operational implications. 3.3.4.5. Advice Non-RPL routers should drop packets that contain an RPL option. 3.3.5. Tunnel Encapsulation Limit (Type=0x04) 3.3.5.1. Uses The Tunnel Encapsulation Limit option can be employed to specify how many further levels of nesting the packet is permitted to undergo. 3.3.5.2. Specification This option is specified in [RFC2473]. 3.3.5.3. Specific Security Implications TBD. 3.3.5.4. Operational and Interoperability Impact if Blocked Filtering packets based on the presence of this option could result in tunnel traffic being dropped. 3.3.5.5. Advice Intermediate systems should not drop packets based on the presence of this option. Since this option is meant to be included in the Destination Options Header, an intermediate system should drop packets that employ this option in any other extension header type. 3.3.6. Router Alert (Type=0x05) Gont, et al. Expires January 5, 2015 [Page 13] Internet-Draft Filtering of IPv6 packets with EHs July 2014 3.3.6.1. Uses Router Alert option [RFC2711], which is typically employed for the RSVP protocol [RFC2205] and the MLD protocol [RFC2710]. 3.3.6.2. Specification This option is specified in [RFC2711]. 3.3.6.3. Specific Security Implications Since this option causes the contents of the packet to be inspected by the handling device, this option could be leveraged for performing DoS attacks. 3.3.6.4. Operational and Interoperability Impact if Blocked Dropping packets that contain this option would break RSVP and multicast deployments. 3.3.6.5. Advice Intermediate systems should, by default, drop packets that contain this option. 3.3.7. Quick-Start (Type=0x26) 3.3.7.1. Uses This IP Option is used in the specification of Quick-Start for TCP and IP, which is an experimental mechanism that allows transport protocols, in cooperation with routers, to determine an allowed sending rate at the start and, at times, in the middle of a data transfer (e.g., after an idle period) [RFC4782]. 3.3.7.2. Specification This option is specified in [RFC4782], on the "Experimental" track. 3.3.7.3. Specific Security Implications Section 9.6 of [RFC4782] notes that Quick-Start is vulnerable to two kinds of attacks: o attacks to increase the routers' processing and state load, and, Gont, et al. Expires January 5, 2015 [Page 14] Internet-Draft Filtering of IPv6 packets with EHs July 2014 o attacks with bogus Quick-Start Requests to temporarily tie up available Quick-Start bandwidth, preventing routers from approving Quick-Start Requests from other connections. 3.3.7.4. Operational and Interoperability Impact if Blocked The Quick-Start functionality would be disabled, and additional delays in TCP's connection establishment (for example) could be introduced. (Please see Section 4.7.2 of [RFC4782].) We note, however, that Quick-Start has been proposed as a mechanism that could be of use in controlled environments, and not as a mechanism that would be intended or appropriate for ubiquitous deployment in the global Internet [RFC4782]. 3.3.7.5. Advice A given router, security gateway, or firewall system has no way of knowing a priori whether this option is valid in its operational environment. Therefore, routers, security gateways, and firewalls SHOULD, by default, ignore the Quick-Start option. Additionally, routers, security gateways, and firewalls SHOULD have a configuration setting that governs their reaction in the presence of packets containing the Quick-Start option. This configuration setting SHOULD allow to honor and process the option, ignore the option, or drop packets containing this option. The default configuration is to ignore the Quick-Start option. We note that if routers in a given environment do not implement and enable the Quick-Start mechanism, only the general security implications of IP options (discussed in Section 3.2) would apply. 3.3.8. CALIPSO (Type=0x07) 3.3.8.1. Uses This option is used for encoding explicit packet Sensitivity Labels on IPv6 packets. It is intended for use only within Multi-Level Secure (MLS) networking environments that are both trusted and trustworthy. 3.3.8.2. Specification This option is specified in [RFC5570]. Gont, et al. Expires January 5, 2015 [Page 15] Internet-Draft Filtering of IPv6 packets with EHs July 2014 3.3.8.3. Specific Security Implications Presence of this option in a packet does not by itself create any specific new threat. Packets with this option ought not normally be seen on the global public Internet. 3.3.8.4. Operational and Interoperability Impact if Blocked If packets with this option are blocked or if the option is stripped from the packet during transmission from source to destination, then the packet itself is likely to be dropped by the receiver because it is not properly labeled. In some cases, the receiver might receive the packet but associate an incorrect sensitivity label with the received data from the packet whose CALIPSO was stripped by an intermediate router or firewall. Associating an incorrect sensitivity label can cause the received information either to be handled as more sensitive than it really is ("upgrading") or as less sensitive than it really is ("downgrading"), either of which is problematic. 3.3.8.5. Advice A given IP router, security gateway, or firewall has no way to know a priori what environment it has been deployed into. Even closed IP deployments generally use exactly the same commercial routers, security gateways, and firewalls that are used in the public Internet. Since operational problems result in environments where this option is needed if either the option is dropped or IPv6 packets containing this option are dropped, but no harm results if the option is carried in environments where it is not needed, the default configuration SHOULD NOT (a) modify or remove this IPv6 option or (b) drop an IPv6 packet because the IPv6 packet contains this option. A given IPv6 router, security gateway, or firewall MAY be configured to drop this option or to drop IP packets containing this option in an environment known to not use this option. For auditing reasons, routers, security gateways, and firewalls SHOULD be capable of logging the numbers of packets containing the CALIPSO on a per-interface basis. Also, routers, security gateways, and firewalls SHOULD be capable of dropping packets based on the CALIPSO presence as well as the CALIPSO values. Gont, et al. Expires January 5, 2015 [Page 16] Internet-Draft Filtering of IPv6 packets with EHs July 2014 3.3.9. SMF_DPD (Type=0x08) 3.3.9.1. Uses This option is employed in the (experimental) Simplified Multicast Forwarding (SMF) for unique packet identification for IPv6 I-DPD, and as a mechanism to guarantee non-collision of hash values for different packets when H-DPD is used. . 3.3.9.2. Specification This option is specified in [RFC6621]. 3.3.9.3. Specific Security Implications TBD. 3.3.9.4. Operational and Interoperability Impact if Blocked TBD. 3.3.9.5. Advice TBD. 3.3.10. Home Address (Type=0xC9) 3.3.10.1. Uses The Home Address option is used by a Mobile IPv6 node while away from home, to inform the recipient of the mobile node's home address. 3.3.10.2. Specification This option is specified in [RFC6275]. 3.3.10.3. Specific Security Implications TBD. 3.3.10.4. Operational and Interoperability Impact if Blocked TBD. Gont, et al. Expires January 5, 2015 [Page 17] Internet-Draft Filtering of IPv6 packets with EHs July 2014 3.3.10.5. Advice TBD. 3.3.11. Endpoint Identification (Type=0x8A) 3.3.11.1. Uses The Endpoint Identification option was meant to be used with the Nimrod routing architecture [NIMROD-DOC], but has never seen widespread deployment. 3.3.11.2. Specification This option is specified in [NIMROD-DOC]. 3.3.11.3. Specific Security Implications TBD. 3.3.11.4. Operational and Interoperability Impact if Blocked None. 3.3.11.5. Advice An intermediate system should drop packets that contain this option. 3.3.12. ILNP Nonce (Type=0x8B) 3.3.12.1. Uses This option is employed by Identifier-Locator Network Protocol for IPv6 (ILNPv6) for providing protection against off-path attacks for packets when ILNPv6 is in use, and as a signal during initial network-layer session creation that ILNPv6 is proposed for use with this network-layer session, rather than classic IPv6. 3.3.12.2. Specification This option is specified in [RFC6744]. 3.3.12.3. Specific Security Implications TBD. Gont, et al. Expires January 5, 2015 [Page 18] Internet-Draft Filtering of IPv6 packets with EHs July 2014 3.3.12.4. Operational and Interoperability Impact if Blocked TBD. 3.3.12.5. Advice TBD. 3.3.13. Line-Identification Option (Type=0x8C) 3.3.13.1. Uses This option is used by an Edge Router to identify the subscriber premises in scenarios where several subscriber premises may be logically connected to the same interface of an Edge Router. 3.3.13.2. Specification This option is specified in [RFC6788]. 3.3.13.3. Specific Security Implications TBD. 3.3.13.4. Operational and Interoperability Impact if Blocked Since this options is meant to be employed in Router Solicitation messages, dropping packets based on the presence of this option at intermediate systems will result in no interoperability implications. 3.3.13.5. Advice Intermediate devices should drop packets that contain this option. 3.3.14. Deprecated (Type=0x4D) 3.3.14.1. Uses TBD. 3.3.14.2. Specification TB. Gont, et al. Expires January 5, 2015 [Page 19] Internet-Draft Filtering of IPv6 packets with EHs July 2014 3.3.14.3. Specific Security Implications TBD. 3.3.14.4. Operational and Interoperability Impact if Blocked TBD. 3.3.14.5. Advice TBD. 3.3.15. MPL Option (Type=0x6D) 3.3.15.1. Uses This option is specified in [I-D.ietf-roll-trickle-mcast], and is meant to be included only in Hop-by-Hop Option headers.. 3.3.15.2. Specification This option is specified in [I-D.ietf-roll-trickle-mcast]. 3.3.15.3. Specific Security Implications TBD. 3.3.15.4. Operational and Interoperability Impact if Blocked TBD. 3.3.15.5. Advice TBD. 3.3.16. IP_DFF (Type=0xEE) 3.3.16.1. Uses This options is employed with the (Experimental) Depth-First Forwarding (DFF) in Unreliable Networks. 3.3.16.2. Specification This option is specified in [RFC6971]. Gont, et al. Expires January 5, 2015 [Page 20] Internet-Draft Filtering of IPv6 packets with EHs July 2014 3.3.16.3. Specific Security Implications TBD. 3.3.16.4. Operational and Interoperability Impact if Blocked TBD. 3.3.16.5. Advice TBD. 3.3.17. RFC3692-style Experiment (Types = 0x1E, 0x3E, 0x5E, 0x7E, 0x9E, 0xBE, 0xDE, 0xFE) 3.3.17.1. Uses It is only appropriate to use these values in explicitly configured experiments; they MUST NOT be shipped as defaults in implementations. 3.3.17.2. Specification Specified in RFC 4727 [RFC4727] in the context of RFC3692-style experiments. 3.3.17.3. Specific Security Implications No specific security issues are known for this IPv4 option. 3.3.17.4. Operational and Interoperability Impact if Blocked None. 3.3.17.5. Advice Routers, security gateways, and firewalls SHOULD have configuration knobs for IPv6 packets that contain RFC3692-style Experiment options to select between "ignore & forward" and "drop & log". Otherwise, no legitimate experiment using these options will be able to traverse any IP router. Special care needs to be taken in the case of "drop & log". Devices SHOULD count the number of packets dropped, but the logging of drop events SHOULD be limited so as to not overburden device resources. The aforementioned configuration knob SHOULD default to "drop & log". Gont, et al. Expires January 5, 2015 [Page 21] Internet-Draft Filtering of IPv6 packets with EHs July 2014 4. IANA Considerations This document has no actions for IANA. 5. Security Considerations This document provides advice on the filtering of IPv6 packets that contain IPv6 Extension Headers (and possibly IPv6 options). Dropping such packets can help to mitigate the security issues that arise from the use of different IPv6 Extension Headers and options. 6. Acknowledgements This document borrows some text an analysis from [RFC7126], authored by Fernando Gont, Randall Atkinson, and Carlos Pignataro. 7. References 7.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2205] Braden, B., Zhang, L., Berson, S., Herzog, S., and S. Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1 Functional Specification", RFC 2205, September 1997. [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", RFC 2460, December 1998. [RFC2473] Conta, A. and S. Deering, "Generic Packet Tunneling in IPv6 Specification", RFC 2473, December 1998. [RFC2675] Borman, D., Deering, S., and R. Hinden, "IPv6 Jumbograms", RFC 2675, August 1999. [RFC2710] Deering, S., Fenner, W., and B. Haberman, "Multicast Listener Discovery (MLD) for IPv6", RFC 2710, October 1999. [RFC2711] Partridge, C. and A. Jackson, "IPv6 Router Alert Option", RFC 2711, October 1999. [RFC3692] Narten, T., "Assigning Experimental and Testing Numbers Considered Useful", BCP 82, RFC 3692, January 2004. [RFC4302] Kent, S., "IP Authentication Header", RFC 4302, December 2005. Gont, et al. Expires January 5, 2015 [Page 22] Internet-Draft Filtering of IPv6 packets with EHs July 2014 [RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC 4303, December 2005. [RFC4304] Kent, S., "Extended Sequence Number (ESN) Addendum to IPsec Domain of Interpretation (DOI) for Internet Security Association and Key Management Protocol (ISAKMP)", RFC 4304, December 2005. [RFC4727] Fenner, B., "Experimental Values In IPv4, IPv6, ICMPv4, ICMPv6, UDP, and TCP Headers", RFC 4727, November 2006. [RFC4782] Floyd, S., Allman, M., Jain, A., and P. Sarolahti, "Quick- Start for TCP and IP", RFC 4782, January 2007. [RFC5095] Abley, J., Savola, P., and G. Neville-Neil, "Deprecation of Type 0 Routing Headers in IPv6", RFC 5095, December 2007. [RFC5201] Moskowitz, R., Nikander, P., Jokela, P., and T. Henderson, "Host Identity Protocol", RFC 5201, April 2008. [RFC5533] Nordmark, E. and M. Bagnulo, "Shim6: Level 3 Multihoming Shim Protocol for IPv6", RFC 5533, June 2009. [RFC5570] StJohns, M., Atkinson, R., and G. Thomas, "Common Architecture Label IPv6 Security Option (CALIPSO)", RFC 5570, July 2009. [RFC6275] Perkins, C., Johnson, D., and J. Arkko, "Mobility Support in IPv6", RFC 6275, July 2011. [RFC6398] Le Faucheur, F., "IP Router Alert Considerations and Usage", BCP 168, RFC 6398, October 2011. [RFC6553] Hui, J. and JP. Vasseur, "The Routing Protocol for Low- Power and Lossy Networks (RPL) Option for Carrying RPL Information in Data-Plane Datagrams", RFC 6553, March 2012. [RFC6554] Hui, J., Vasseur, JP., Culler, D., and V. Manral, "An IPv6 Routing Header for Source Routes with the Routing Protocol for Low-Power and Lossy Networks (RPL)", RFC 6554, March 2012. [RFC6621] Macker, J., "Simplified Multicast Forwarding", RFC 6621, May 2012. Gont, et al. Expires January 5, 2015 [Page 23] Internet-Draft Filtering of IPv6 packets with EHs July 2014 [RFC6744] Atkinson,, RJ., "IPv6 Nonce Destination Option for the Identifier-Locator Network Protocol for IPv6 (ILNPv6)", RFC 6744, November 2012. [RFC6788] Krishnan, S., Kavanagh, A., Varga, B., Ooghe, S., and E. Nordmark, "The Line-Identification Option", RFC 6788, November 2012. [RFC6971] Herberg, U., Cardenas, A., Iwao, T., Dow, M., and S. Cespedes, "Depth-First Forwarding (DFF) in Unreliable Networks", RFC 6971, June 2013. [RFC7045] Carpenter, B. and S. Jiang, "Transmission and Processing of IPv6 Extension Headers", RFC 7045, December 2013. [RFC7112] Gont, F., Manral, V., and R. Bonica, "Implications of Oversized IPv6 Header Chains", RFC 7112, January 2014. [RFC7123] Gont, F. and W. Liu, "Security Implications of IPv6 on IPv4 Networks", RFC 7123, February 2014. 7.2. Informative References [Biondi2007] Biondi, P. and A. Ebalard, "IPv6 Routing Header Security", CanSecWest 2007 Security Conference, 2007, . [Cisco-EH] Cisco Systems, , "IPv6 Extension Headers Review and Considerations", Whitepaper. October 2006, . [FW-Benchmark] Zack, E., "Firewall Security Assessment and Benchmarking IPv6 Firewall Load Tests", IPv6 Hackers Meeting #1, Berlin, Germany. June 30, 2013, . [I-D.ietf-6man-predictable-fragment-id] Gont, F., "Security Implications of Predictable Fragment Identification Values", draft-ietf-6man-predictable- fragment-id-01 (work in progress), April 2014. Gont, et al. Expires January 5, 2015 [Page 24] Internet-Draft Filtering of IPv6 packets with EHs July 2014 [I-D.ietf-roll-trickle-mcast] Hui, J. and R. Kelsey, "Multicast Protocol for Low power and Lossy Networks (MPL)", draft-ietf-roll-trickle- mcast-09 (work in progress), April 2014. [IANA-IPV6] Internet Assigned Numbers Authority, "Internet Protocol Version 6 (IPv6) Parameters", December 2013, . [NIMROD-DOC] Nimrod Documentation Page, , "http://ana-3.lcs.mit.edu/~jnc/nimrod/", . [RFC7126] Gont, F., Atkinson, R., and C. Pignataro, "Recommendations on Filtering of IPv4 Packets Containing IPv4 Options", BCP 186, RFC 7126, February 2014. Authors' Addresses Fernando Gont UTN-FRH / SI6 Networks Evaristo Carriego 2644 Haedo, Provincia de Buenos Aires 1706 Argentina Phone: +54 11 4650 8472 Email: fgont@si6networks.com URI: http://www.si6networks.com Will Liu Huawei Technologies Bantian, Longgang District Shenzhen 518129 P.R. China Email: liushucheng@huawei.com Gont, et al. Expires January 5, 2015 [Page 25] Internet-Draft Filtering of IPv6 packets with EHs July 2014 Ronald P. Bonica Juniper Networks 2251 Corporate Park Drive Herndon, VA 20171 US Phone: 571 250 5819 Email: rbonica@juniper.net Gont, et al. Expires January 5, 2015 [Page 26]