opsec F. Gont Internet-Draft UTN-FRH / SI6 Networks Intended status: Best Current Practice W. Liu Expires: February 27, 2015 Huawei Technologies R. Bonica Juniper Networks August 26, 2014 Recommendations on Filtering of IPv6 Packets Containing IPv6 Extension Headers draft-gont-opsec-ipv6-eh-filtering-02.txt Abstract This 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 discarding 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 February 27, 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 February 27, 2015 [Page 1] Internet-Draft Filtering of IPv6 packets with EHs August 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 2. Terminology and Conventions Used in This Document . . . . . . 3 2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 2.2. Conventions . . . . . . . . . . . . . . . . . . . . . . . 3 3. IPv6 Extension Headers . . . . . . . . . . . . . . . . . . . 4 3.1. General Discussion . . . . . . . . . . . . . . . . . . . 4 3.2. General Security Implications . . . . . . . . . . . . . . 5 3.3. Advice on the Handling of IPv6 Packets with Specific IPv6 Extension Headers . . . . . . . . . . . . . . . . . . . . 5 3.4. Advice on the Handling of Packets with Unknown IPv6 Extension Headers . . . . . . . . . . . . . . . . . . . . 13 4. IPv6 Options . . . . . . . . . . . . . . . . . . . . . . . . 14 4.1. General Discussion . . . . . . . . . . . . . . . . . . . 14 4.2. General Security Implications of IPv6 Options . . . . . . 14 4.3. Advice on the Handling of Packets with Specific IPv6 Options . . . . . . . . . . . . . . . . . . . . . . . . . 14 4.4. Advice on the handling of Packets with Unknown IPv6 Options . . . . . . . . . . . . . . . . . . . . . . . . . 24 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 6. Security Considerations . . . . . . . . . . . . . . . . . . . 25 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 25 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 26 8.1. Normative References . . . . . . . . . . . . . . . . . . 26 8.2. Informative References . . . . . . . . . . . . . . . . . 28 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29 1. Introduction Recent studies (see e.g.[I-D.gont-v6ops-ipv6-ehs-in-real-world]) suggest that there is widespread filtering of IPv6 packets that contain IPv6 Extension Headers (EHs). While some operators "officially" filter packets that contain IPv6 extension headers, it is possible that some of the measured packet drops be the result of improper configuration defaults, or inappropriate advice in this area. This 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), discarding packets based on the IPv6 Extension Headers or IPv6 options they contain may have implications on the proper Gont, et al. Expires February 27, 2015 [Page 2] Internet-Draft Filtering of IPv6 packets with EHs August 2014 functioning of such protocols. Thus, this document attempts to discuss the operational and interoperability implications of such filtering policies, and provide advice in this area. This document is similar in nature to [RFC7126], which addresses the same problem for the IPv4 case. Section 2 of this document specifies the terminology and conventions employed throughout this document. Section 3 of this document discusses IPv6 extension headers and provides advice in the area of filtering IPv6 packets that contain such IPv6 Extension Headers. Section 4 of this document discusses IPv6 options and provides advice in the area of filtering IPv6 packets that contain such options. 2. Terminology and Conventions Used in This Document 2.1. Terminology 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 terms "permit" (allow the traffic), "drop" (drop with no notification to sender), and "reject" (drop with appropriate notification to sender) are employed as defined in [RFC3871]. Throughout this document we also employ the term "discard" as a generic term to indicate the act of discarding a packet, irrespective of whether the sender is notified of such drops. 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]. 2.2. Conventions This document assumes that nodes comply with the requirements in [RFC7045]. Namely (from [RFC7045]), o If a forwarding node discards a packet containing a standard IPv6 extension header, it MUST be the result of a configurable policy and not just the result of a failure to recognise such a header. o The discard policy for each standard type of extension header MUST be individually configurable. o The default configuration SHOULD allow all standard extension headers. Gont, et al. Expires February 27, 2015 [Page 3] Internet-Draft Filtering of IPv6 packets with EHs August 2014 The advice provided in this document is only meant to guide an operator in configuring forwarding devices, and is *not* to be interpreted as advice regarding default configuration settings for network devices. That is, this document provides advice with respect to operational configurations, but does not change the implementation defaults required by [RFC7045] and [draft-gont-6man-ipv6-opt-transmit]. We recommend that a configuration option is made available to govern the processing of each IPv6 Extension Header type and each IPv6 option type. Such configuration options may include the following possible settings: o Permit this IPv6 Extension Header or IPv6 Option type o Drop (and log) packets containing this IPv6 Extension Header or option type o Reject (and log) packets containing this IPv6 Extension Header or option type (where the packet drop is signaled with an ICMPv6 error message) o Rate-limit the processing of packets containing this IPv6 Extension Header or option type o Ignore this IPv6 Extension Header or option type (forwarding packets that contain them) We note that special care needs to be taken when devices log packet drops/rejects. Devices should count the number of packets dropped/ rejected, but the logging of drop/reject events should be limited so as to not overburden device resources. Finally, we note that when discarding packets, it is generally desirable that the sender be signaled of the packet drop, since this is of use for trouble-shooting purposes. However, throughout this document (when recommending that packets be discarded) we generically refer to the action as "discard" without specifying whether the sender is signaled of the packet drop. 3. IPv6 Extension Headers 3.1. General Discussion IPv6 [RFC2460] Extension Headers allow for the extension of the IPv6 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 Gont, et al. Expires February 27, 2015 [Page 4] Internet-Draft Filtering of IPv6 packets with EHs August 2014 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 IPv6 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 discarding the offending packets when they fail to comply with the requirements in [RFC7112]. 3.2. General Security Implications Depending on the specific device architecture, IPv6 packets that contain IPv6 Extension Headers may cause the corresponding packets to be processed on the slow path, and hence may 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. 3.3. Advice on the Handling of IPv6 Packets with Specific IPv6 Extension Headers 3.3.1. IPv6 Hop-by-Hop Options (Protocol Number=0) 3.3.1.1. Uses The Hop-by-Hop Options header is used to carry optional information that should be examined by every node along a packet's delivery path. 3.3.1.2. Specification This Extension Header is specified in [RFC2460], and its processing rules have been updated by [RFC7045]. At the time of this writing, the following options have been specified for the Hop-by-Hop Options extension header: o Type 0x05: Router Alert [RFC2711] o Type 0xC2: Jumbo Payload [RFC2675] o Type 0x63: RPL Option [RFC6553] o Type 0x08: SMF_DPD [RFC6621] Gont, et al. Expires February 27, 2015 [Page 5] Internet-Draft Filtering of IPv6 packets with EHs August 2014 o Type 0x6D: MPL Option [I-D.ietf-roll-trickle-mcast] o Type 0xEE: IPv6 DFF Header [RFC6971] o Type 0x26: Quick-Start [RFC4782] o Type 0x07: CALIPSO [RFC5570] 3.3.1.3. Specific Security Implications Since this Extension Header should be processed by all intermediate- systems en route, it can be leveraged to perform Denial of Service attacks against the network infrastructure. 3.3.1.4. Operational and Interoperability Impact if Blocked Discarding packets containing a Hop-by-Hop Option extension header would break any of the protocols that rely on it for proper functioning. For example, it would break RSVP [RFC2205] and multicast deployments, and would cause IPv6 jumbograms to be discarded. 3.3.1.5. Advice The recommended configuration for the processing of these packets depends on the features and capabilities of the underlying platform. On platforms that allow forwarding of packets with HBH Options on the fast path, we recommend that packets with a HBH Options extension header be forwarded as normal (for instance, [RFC7045] allows for implementations to ignore the HBH Options extension header when forwarding packets). Otherwise, on platforms in which processing of packets with a IPv6 HBH Options extension header is carried out in the slow path, and an option is provided to rate-limit these packets, we recommend that this option be selected. Finally, when packets containing a HBH Options extension header are processed in the slow- path, and the underlying platform does not have any mitigation options available for attacks based on these packets, we recommend that such platforms discard packets containing IPv6 HBH Options extension headers. Finally, we note that, for obvious reasons, RPL (Routing Protocol for Low-Power and Lossy Networks) [RFC6550] routers must not discard packets based on the presence of an IPv6 Hop-by-Hop Options Extension Header. Gont, et al. Expires February 27, 2015 [Page 6] Internet-Draft Filtering of IPv6 packets with EHs August 2014 3.3.2. Routing Header for IPv6 (Protocol Number=43) 3.3.2.1. 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. 3.3.2.2. 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) 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 3.3.2.3. Specific Security Implications The security implications of RHT0 have been discussed in detail in [Biondi2007] and [RFC5095]. 3.3.2.4. Operational and Interoperability Impact if Blocked Blocking packets containing a RHT0 or RTH1 has no operational implications. However, blocking packets employing other routing header types will break the protocols that rely on them. Gont, et al. Expires February 27, 2015 [Page 7] Internet-Draft Filtering of IPv6 packets with EHs August 2014 3.3.2.5. Advice Intermediate systems should discard packets containing a RHT0 or RHT1. As required by [RFC7045], packets containing standardised and undeprecated Routing Headers should be permitted. 3.3.3. Fragment Header for IPv6 (Protocol Number=44) 3.3.3.1. Uses This Extension Header provides the fragmentation functionality for IPv6. 3.3.3.2. Specification This Extension Header is specified in [RFC2460]. 3.3.3.3. Specific Security Implications The security implications of the Fragment Header range from Denial of Service attacks (e.g. based on flooding a target with IPv6 fragments) to information leakage attacks [I-D.ietf-6man-predictable-fragment-id]. 3.3.3.4. Operational and Interoperability Impact if Blocked Blocking packets that contain a Fragment Header will break any protocol that may rely on fragmentation (e.g., the DNS [RFC1034]). 3.3.3.5. Advice Intermediate systems should permit packets that contain a Fragment Header. 3.3.4. Encapsulating Security Payload (Protocol Number=50) 3.3.4.1. Uses This extension Header is employed for the IPsec suite [RFC4303]. 3.3.4.2. Specification This extension header is specified in [RFC4303]. Gont, et al. Expires February 27, 2015 [Page 8] Internet-Draft Filtering of IPv6 packets with EHs August 2014 3.3.4.3. 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. 3.3.4.4. Operational and Interoperability Impact if Blocked Discarding packets that employ this extension header would break IPsec deployments. 3.3.4.5. Advice Intermediate systems should permit packets containing the Encapsulating Security Payload extension header. 3.3.5. Authentication Header (Number=51) 3.3.5.1. Uses The Authentication Header can be employed for provide authentication services in IPv4 and IPv6. 3.3.5.2. Specification This Extension Header is specified in [RFC4302]. 3.3.5.3. 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. 3.3.5.4. Operational and Interoperability Impact if Blocked Discarding packets that employ this extension header would break IPsec deployments. 3.3.5.5. Advice Intermediate systems should permit packets containing an Authentication Header. Gont, et al. Expires February 27, 2015 [Page 9] Internet-Draft Filtering of IPv6 packets with EHs August 2014 3.3.6. Destination Options for IPv6 (Protocol Number=60) 3.3.6.1. Uses The Destination Options header is used to carry optional information that needs be examined only by a packet's destination node(s). 3.3.6.2. Specification This Extension Header is specified in [RFC2460]. At the time of this writing, the following options have been specified for this extension header: o Type 0x04: Tunnel Encapsulation Limit [RFC2473] o Type 0xC9: Home Address [RFC6275] o Type 0x8B: ILNP Nonce [RFC6744] o Type 0x8C: Line-Identification Option [RFC6788] 3.3.6.3. Specific Security Implications No security implications are known, other than the general implications of IPv6 extension headers. 3.3.6.4. Operational and Interoperability Impact if Blocked Discarding packets that contain a Destination Options header would break protocols that rely on this EH type for conveying information, including protocols such as ILNP [RFC6740] and Mobile IPv6 [RFC6275], and IPv6 tunnels that employ the Tunnel Encapsulation Limit option. 3.3.6.5. Advice Intermediate systems should permit packets that contain a Destination Options Header. 3.3.7. Mobility Header (Number=135) 3.3.7.1. 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. Gont, et al. Expires February 27, 2015 [Page 10] Internet-Draft Filtering of IPv6 packets with EHs August 2014 3.3.7.2. Specification This Extension Header is specified in [RFC6275]. 3.3.7.3. Specific Security Implications TBD. 3.3.7.4. Operational and Interoperability Impact if Blocked Discarding packets containing this extension header would break Mobile IPv6. 3.3.7.5. Advice Intermediate systems should permit packets containing this extension header. 3.3.8. Host Identity Protocol (Protocol Number=139) 3.3.8.1. 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. 3.3.8.2. Specification This extension Header is specified in [RFC5201]. 3.3.8.3. Specific Security Implications TBD. 3.3.8.4. Operational and Interoperability Impact if Blocked Discarding packets that contain the Host Identity Protocol would break HIP deployments. 3.3.8.5. Advice Intermediate systems should permit packets that contain a Host Identity Protocol extension header. Gont, et al. Expires February 27, 2015 [Page 11] Internet-Draft Filtering of IPv6 packets with EHs August 2014 3.3.9. Shim6 Protocol (Protocol Number=140) 3.3.9.1. Uses This extension header is employed by the Shim6 [RFC5533] Protocol. 3.3.9.2. Specification This Extension Header is specified in [RFC5533]. 3.3.9.3. Specific Security Implications TBD. 3.3.9.4. Operational and Interoperability Impact if Blocked Discarding packets that contain this extension header will break Shim6. 3.3.9.5. Advice Intermediate systems should permit packets containing this extension header. 3.3.10. Use for experimentation and testing (Protocol Numbers=253 and 254) 3.3.10.1. Uses These IPv6 extension headers are employed for performing RFC3692-Style experiments (see [RFC3692] for details). 3.3.10.2. Specification These Extension Headers are specified in [RFC3692] and [RFC4727]. 3.3.10.3. Specific Security Implications The security implications of these extension headers will depend on their specific use. 3.3.10.4. Operational and Interoperability Impact if Blocked For obvious reasons, discarding packets that contain these extension headers limits the ability to perform legitimate experiments across IPv6 routers. Gont, et al. Expires February 27, 2015 [Page 12] Internet-Draft Filtering of IPv6 packets with EHs August 2014 3.3.10.5. Advice Intermediate systems should discard packets containing these extension headers. Only in specific scenarios in which RFC3692-Style experiments are to be performed should these extension headers be permitted. 3.4. Advice on the Handling of Packets with Unknown IPv6 Extension Headers We refer to IPv6 extension headers that have not been assigned an Internet Protocol Number by IANA (and marked as such) in [IANA-PROTOCOLS] as "unknown IPv6 extension headers". 3.4.1. Uses New IPv6 extension headers may be specified as part of future extensions to the IPv6 protocol. Since IPv6 Extension Headers and Upper-layer protocols employ the same namespace, it is impossible to tell whether an unknown "Internet Protocol Number" is being employed for an IPv6 Extension Header or an Upper-Layer protocol. 3.4.2. Specification The processing of unknown IPv6 extension headers is specified in [RFC2460] and [RFC7045]. 3.4.3. Specific Security Implications For obvious reasons, it is impossible to determine specific security implications of unknown IPv6 extension headers. 3.4.4. Operational and Interoperability Impact if Blocked As noted in [RFC7045], discarding unknown IPv6 extension headers may slow down the deployment of new IPv6 extension headers and transport protocols. The corresponding IANA registry ([IANA-PROTOCOLS] should be monitored such that filtering rules are updated as new IPv6 extension headers are standardized. We note that since IPv6 extension headers and upper-layer protocols share the same numbering space, discarding unknown IPv6 extension headers may result in packets encapsulating unknown upper-layer protocols being discarded. Gont, et al. Expires February 27, 2015 [Page 13] Internet-Draft Filtering of IPv6 packets with EHs August 2014 3.4.5. Advice Intermediate systems should discard packets containing unknown IPv6 extension headers. 4. IPv6 Options 4.1. General Discussion The following subsections describe specific security implications of different IPv6 options, and provide advice regarding filtering packets that contain such options. 4.2. General Security Implications of IPv6 Options The general security implications of IPv6 options are closely related to those discussed in Section 3.2 for IPv6 Extension Headers. Essentially, packets that contain IPv6 options might need to be processed by an IPv6 router's general-purpose CPU,and hence could present 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]). 4.3. 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 discarded, and specific advice regarding whether packets containing these options should be permitted. 4.3.1. Pad1 (Type=0x00) 4.3.1.1. 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. 4.3.1.2. Specification This option is specified in [RFC2460]. 4.3.1.3. Specific Security Implications None. Gont, et al. Expires February 27, 2015 [Page 14] Internet-Draft Filtering of IPv6 packets with EHs August 2014 4.3.1.4. Operational and Interoperability Impact if Blocked Discarding packets that contain this option would potentially break any protocol that relies on IPv6 extension headers. 4.3.1.5. Advice Intermediate systems should not discard packets based on the presence of this option. 4.3.2. PadN (Type=0x01) 4.3.2.1. 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. 4.3.2.2. Specification This option is specified in [RFC2460]. 4.3.2.3. Specific Security Implications Because of the possible size of this option, it could be leveraged as a large-bandwidth covert channel. 4.3.2.4. Operational and Interoperability Impact if Blocked Discarding packets that contain this option would potentially break any protocol that relies on IPv6 extension headers. 4.3.2.5. Advice Intermediate systems should not discard IPv6 packets based on the presence of this option. 4.3.3. Jumbo Payload (Type=0XC2) 4.3.3.1. Uses The Jumbo payload option provides the means of specifying payloads larger than 65535 bytes. 4.3.3.2. Specification This option is specified in [RFC2675]. Gont, et al. Expires February 27, 2015 [Page 15] Internet-Draft Filtering of IPv6 packets with EHs August 2014 4.3.3.3. Specific Security Implications TBD. 4.3.3.4. Operational and Interoperability Impact if Blocked Discarding packets based on the presence of this option will cause IPv6 jumbograms to be discarded. 4.3.3.5. Advice Intermediate systems should discard packets that contain this option. An operator should permit this option only in specific scenarios in which support for IPv6 jumbograms is desired. 4.3.4. RPL Option (Type=0x63) 4.3.4.1. Uses The RPL Option provides a mechanism to include routing information with each datagram that an RPL router forwards. 4.3.4.2. Specification This option is specified in [RFC6553]. 4.3.4.3. Specific Security Implications TBD. 4.3.4.4. Operational and Interoperability Impact if Blocked This option is meant to be employed within an RPL instance. As a result, discarding packets based on the presence of this option (e.g. at an ISP) will not result in interoperability implications. 4.3.4.5. Advice Non-RPL routers should discard packets that contain an RPL option. 4.3.5. Tunnel Encapsulation Limit (Type=0x04) 4.3.5.1. Uses The Tunnel Encapsulation Limit option can be employed to specify how many further levels of nesting the packet is permitted to undergo. Gont, et al. Expires February 27, 2015 [Page 16] Internet-Draft Filtering of IPv6 packets with EHs August 2014 4.3.5.2. Specification This option is specified in [RFC2473]. 4.3.5.3. Specific Security Implications TBD. 4.3.5.4. Operational and Interoperability Impact if Blocked Discarding packets based on the presence of this option could result in tunnel traffic being discarded. 4.3.5.5. Advice Intermediate systems should not discard packets based on the presence of this option. 4.3.6. Router Alert (Type=0x05) 4.3.6.1. Uses The Router Alert option [RFC2711] is typically employed for the RSVP protocol [RFC2205] and the MLD protocol [RFC2710]. 4.3.6.2. Specification This option is specified in [RFC2711]. 4.3.6.3. 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. 4.3.6.4. Operational and Interoperability Impact if Blocked Discarding packets that contain this option would break RSVP and multicast deployments. 4.3.6.5. Advice Intermediate systems should discard packets that contain this option. Only in specific environments where support for RSVP or similar protocols is desired should this option be permitted. Gont, et al. Expires February 27, 2015 [Page 17] Internet-Draft Filtering of IPv6 packets with EHs August 2014 4.3.7. Quick-Start (Type=0x26) 4.3.7.1. 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]. 4.3.7.2. Specification This option is specified in [RFC4782], on the "Experimental" track. 4.3.7.3. 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, 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. 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 4.2) would apply. 4.3.7.4. 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]. 4.3.7.5. Advice Intermediate systems should not discard IPv6 packets based on the presence of this option. Gont, et al. Expires February 27, 2015 [Page 18] Internet-Draft Filtering of IPv6 packets with EHs August 2014 4.3.8. CALIPSO (Type=0x07) 4.3.8.1. 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. 4.3.8.2. Specification This option is specified in [RFC5570]. 4.3.8.3. 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. 4.3.8.4. Operational and Interoperability Impact if Blocked If packets with this option are discarded or if the option is stripped from the packet during transmission from source to destination, then the packet itself is likely to be discarded 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. 4.3.8.5. Advice Intermediate systems that do not operate in Multi-Level Secure (MLS) networking environments should discard packets that contain this option. 4.3.9. SMF_DPD (Type=0x08) 4.3.9.1. 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. Gont, et al. Expires February 27, 2015 [Page 19] Internet-Draft Filtering of IPv6 packets with EHs August 2014 4.3.9.2. Specification This option is specified in [RFC6621]. 4.3.9.3. Specific Security Implications TBD. 4.3.9.4. Operational and Interoperability Impact if Blocked TBD. 4.3.9.5. Advice TBD. 4.3.10. Home Address (Type=0xC9) 4.3.10.1. 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. 4.3.10.2. Specification This option is specified in [RFC6275]. 4.3.10.3. Specific Security Implications TBD. 4.3.10.4. Operational and Interoperability Impact if Blocked Discarding IPv6 packets based on the presence of this option will break Mobile IPv6. 4.3.10.5. Advice Intermediate systems should not discard IPv6 packets based on the presence of this option. 4.3.11. Endpoint Identification (Type=0x8A) 4.3.11.1. Uses The Endpoint Identification option was meant to be used with the Nimrod routing architecture [NIMROD-DOC], but has never seen widespread deployment. Gont, et al. Expires February 27, 2015 [Page 20] Internet-Draft Filtering of IPv6 packets with EHs August 2014 4.3.11.2. Specification This option is specified in [NIMROD-DOC]. 4.3.11.3. Specific Security Implications TBD. 4.3.11.4. Operational and Interoperability Impact if Blocked None. 4.3.11.5. Advice Intermediate systems should discard packets that contain this option. 4.3.12. ILNP Nonce (Type=0x8B) 4.3.12.1. 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. 4.3.12.2. Specification This option is specified in [RFC6744]. 4.3.12.3. Specific Security Implications TBD. 4.3.12.4. Operational and Interoperability Impact if Blocked Discarding packets that contain this option will break INLPv6 deployments. 4.3.12.5. Advice Intermediate systems should not discard packets based on the presence of this option. Gont, et al. Expires February 27, 2015 [Page 21] Internet-Draft Filtering of IPv6 packets with EHs August 2014 4.3.13. Line-Identification Option (Type=0x8C) 4.3.13.1. 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. 4.3.13.2. Specification This option is specified in [RFC6788]. 4.3.13.3. Specific Security Implications TBD. 4.3.13.4. Operational and Interoperability Impact if Blocked Since this option is meant to be employed in Router Solicitation messages, discarding packets based on the presence of this option at intermediate systems will result in no interoperability implications. 4.3.13.5. Advice Intermediate devices should discard packets that contain this option. 4.3.14. Deprecated (Type=0x4D) 4.3.14.1. Uses No information has been found about this option type. 4.3.14.2. Specification No information has been found about this option type. 4.3.14.3. Specific Security Implications No information has been found about this option type, and hence it has been impossible to perform the corresponding security assessment. 4.3.14.4. Operational and Interoperability Impact if Blocked Unknown. Gont, et al. Expires February 27, 2015 [Page 22] Internet-Draft Filtering of IPv6 packets with EHs August 2014 4.3.14.5. Advice Intermediate systems should discard packets that contain this option. 4.3.15. MPL Option (Type=0x6D) 4.3.15.1. Uses This option is used with the Multicast Protocol for Low power and Lossy Networks (MPL), that provides IPv6 multicast forwarding in constrained networks. 4.3.15.2. Specification This option is specified in [I-D.ietf-roll-trickle-mcast], and is meant to be included only in Hop-by-Hop Option headers. 4.3.15.3. Specific Security Implications TBD. 4.3.15.4. Operational and Interoperability Impact if Blocked TBD. 4.3.15.5. Advice TBD. 4.3.16. IP_DFF (Type=0xEE) 4.3.16.1. Uses This option is employed with the (Experimental) Depth-First Forwarding (DFF) in Unreliable Networks. 4.3.16.2. Specification This option is specified in [RFC6971]. 4.3.16.3. Specific Security Implications TBD. Gont, et al. Expires February 27, 2015 [Page 23] Internet-Draft Filtering of IPv6 packets with EHs August 2014 4.3.16.4. Operational and Interoperability Impact if Blocked TBD. 4.3.16.5. Advice TBD. 4.3.17. RFC3692-style Experiment (Types = 0x1E, 0x3E, 0x5E, 0x7E, 0x9E, 0xBE, 0xDE, 0xFE) 4.3.17.1. Uses These options can be employed for performing RFC3692-style experiments. It is only appropriate to use these values in explicitly configured experiments; they must not be shipped as defaults in implementations. 4.3.17.2. Specification Specified in RFC 4727 [RFC4727] in the context of RFC3692-style experiments. 4.3.17.3. Specific Security Implications The specific security implications will depend on the specific use of these options. 4.3.17.4. Operational and Interoperability Impact if Blocked For obvious reasons, discarding packets that contain these options limits the ability to perform legitimate experiments across IPv6 routers. 4.3.17.5. Advice Intermediate systems should discard packets that contain these options. Only in specific environments where RFC3692-style experiments are meant to be performed should these options be permitted. 4.4. Advice on the handling of Packets with Unknown IPv6 Options We refer to IPv6 options that have not been assigned an IPv6 option type in the corresponding registry ([IANA-IPV6-PARAM]) as "unknown IPv6 options". Gont, et al. Expires February 27, 2015 [Page 24] Internet-Draft Filtering of IPv6 packets with EHs August 2014 4.4.1. Uses New IPv6 options may be specified as part of future protocol work. 4.4.2. Specification The processing of unknown IPv6 options is specified in [RFC2460]. 4.4.3. Specific Security Implications For obvious reasons, it is impossible to determine specific security implications of unknown IPv6 options. 4.4.4. Operational and Interoperability Impact if Blocked Discarding unknown IPv6 options may slow down the deployment of new IPv6 options. As noted in [draft-gont-6man-ipv6-opt-transmit], the corresponding IANA registry ([IANA-IPV6-PARAM] should be monitored such that IPv6 option filtering rules are updated as new IPv6 options are standardized. 4.4.5. Advice Enterprise intermediate systems that process the contents of IPv6 extension headers should discard packets that contain unknown options. Other intermediate systems that process the contents of IPv6 extension headers should permit packets that contain unknown options. 5. IANA Considerations This document has no actions for IANA. 6. Security Considerations This document provides advice on the filtering of IPv6 packets that contain IPv6 Extension Headers (and possibly IPv6 options). Discarding such packets can help to mitigate the security issues that arise from the use of different IPv6 Extension Headers and options. 7. Acknowledgements The authors of this document would like to thank (in alphabetical order) Mikael Abrahamsson, Brian Carpenter, Mike Heard, and Donald Smith, for providing valuable comments on earlier versions of this document. Gont, et al. Expires February 27, 2015 [Page 25] Internet-Draft Filtering of IPv6 packets with EHs August 2014 This document borrows some text an analysis from [RFC7126], authored by Fernando Gont, Randall Atkinson, and Carlos Pignataro. 8. References 8.1. Normative References [RFC1034] Mockapetris, P., "Domain names - concepts and facilities", STD 13, RFC 1034, November 1987. [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. [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. Gont, et al. Expires February 27, 2015 [Page 26] Internet-Draft Filtering of IPv6 packets with EHs August 2014 [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. [RFC6550] Winter, T., Thubert, P., Brandt, A., Hui, J., Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur, JP., and R. Alexander, "RPL: IPv6 Routing Protocol for Low-Power and Lossy Networks", RFC 6550, March 2012. [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. [RFC6740] Atkinson,, RJ., "Identifier-Locator Network Protocol (ILNP) Architectural Description", RFC 6740, November 2012. Gont, et al. Expires February 27, 2015 [Page 27] Internet-Draft Filtering of IPv6 packets with EHs August 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. [draft-gont-6man-ipv6-opt-transmit] Gont, F., Liu, W., and R. Bonica, "Transmission and Processing of IPv6 Options", IETF Internet Draft, work in progress, August 2014. 8.2. 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.gont-v6ops-ipv6-ehs-in-real-world] Gont, F., Linkova, J., Chown, T., and W. Will, "IPv6 Extension Headers in the Real World", draft-gont-v6ops- ipv6-ehs-in-real-world-00 (work in progress), August 2014. Gont, et al. Expires February 27, 2015 [Page 28] Internet-Draft Filtering of IPv6 packets with EHs August 2014 [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. [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-PARAM] Internet Assigned Numbers Authority, "Internet Protocol Version 6 (IPv6) Parameters", December 2013, . [IANA-PROTOCOLS] Internet Assigned Numbers Authority, "Protocol Numbers", 2014, . [NIMROD-DOC] Nimrod Documentation Page, , "http://ana-3.lcs.mit.edu/~jnc/nimrod/", . [RFC3871] Jones, G., "Operational Security Requirements for Large Internet Service Provider (ISP) IP Network Infrastructure", RFC 3871, September 2004. [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 Gont, et al. Expires February 27, 2015 [Page 29] Internet-Draft Filtering of IPv6 packets with EHs August 2014 Will(Shucheng) Liu Huawei Technologies Bantian, Longgang District Shenzhen 518129 P.R. China Email: liushucheng@huawei.com 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 February 27, 2015 [Page 30]