Internet Draft A. Conta, Transwitch IPv6 Working Group S. Deering, Cisco Systems
1 June21 October 2004 M. Gupta, Nokia (ed.) Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification <draft-ietf-ipngwg-icmp-v3-04.txt><draft-ietf-ipngwg-icmp-v3-05.txt> Status of this Memo By submitting this Internet-Draft, I certify that any applicable patent or other IPR claims of which I am aware have been disclosed, and any of which I become aware will be disclosed, in accordance with RFC 3668. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This internet draft will expire on December 4,April 21, 2004. Abstract This document describes the format of a set of control messages used in ICMPv6 (Internet Control Message Protocol). ICMPv6 is the Internet Control Message Protocol for Internet Protocol version 6 (IPv6). Table of Contents 1. Introduction.....................................................3 2. ICMPv6 (ICMP for IPv6)...........................................3 2.1 Message General Format....................................3 2.2 Message Source Address Determination......................5 2.3 Message Checksum Calculation..............................6 2.4 Message Processing Rules..................................6 3. ICMPv6 Error Messages............................................9 3.1 Destination Unreachable Message...........................9 3.2 Packet Too Big Message...................................12 3.3 Time Exceeded Message....................................13 3.4 Parameter Problem Message................................15 4. ICMPv6 Informational Messages...................................17 4.1 Echo Request Message.....................................17 4.2 Echo Reply Message.......................................18 5. Security Considerations.........................................20 5.1 Authentication and Confidentiality of ICMP messages......20 5.2 ICMP Attacks.............................................20 6. IANA Considerations.............................................21 6.1 Procedure for new ICMPV6 Type and Code value assignments.22 6.2 Assignments for this document............................22 7. References......................................................23 7.1 Normative................................................23 7.2 Informative..............................................24 8. Acknowledgments.................................................24 9. Authors' Addresses..............................................24 Appendix A - Changes since RFC 2463................................24 1. Introduction The Internet Protocol, version 6 (IPv6) is a new version of IP. IPv6 uses the Internet Control Message Protocol (ICMP) as defined for IPv4 [RFC-792], with a number of changes. The resulting protocol is called ICMPv6, and has an IPv6 Next Header value of 58. This document describes the format of a set of control messages used in ICMPv6. It does not describe the procedures for using these messages to achieve functions like Path MTU discovery; such procedures are described in other documents (e.g., [PMTU]). Other documents may also introduce additional ICMPv6 message types, such as Neighbor Discovery messages [IPv6-DISC], subject to the general rules for ICMPv6 messages given in section 2 of this document. Terminology defined in the IPv6 specification [IPv6] and the IPv6 Routing and Addressing specification [IPv6-ADDR] applies to this document as well. This document obsoletes RFC 2463 [RFC-2463]. 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 [RFC-2119]. 2. ICMPv6 (ICMP for IPv6) ICMPv6 is used by IPv6 nodes to report errors encountered in processing packets, and to perform other internet-layer functions, such as diagnostics (ICMPv6 "ping"). ICMPv6 is an integral part of IPv6 and MUST be fully implemented by every IPv6 node. 2.1 Message General Format ICMPv6 messages are grouped into two classes: error messages and informational messages. Error messages are identified as such by having a zero in the high-order bit of their message Type field values. Thus, error messages have message Types from 0 to 127; informational messages have message Types from 128 to 255. This document defines the message formats for the following ICMPv6 messages: ICMPv6 error messages: 1 Destination Unreachable (see section 3.1) 2 Packet Too Big (see section 3.2) 3 Time Exceeded (see section 3.3) 4 Parameter Problem (see section 3.4) 100 Private experimentation 101 Private experimentation 127 Reserved for expansion of ICMPv6 error messages ICMPv6 informational messages: 128 Echo Request (see section 4.1) 129 Echo Reply (see section 4.2) 200 Private experimentation 201 Private experimentation 255 Reserved for expansion of ICMPv6 informational messages Type values 100, 101, 200, and 201 are reserved for private experimentation. These are not intended for general use. It is expected that multiple concurrent experiments will be done with the same type values. Any wide scale and/or uncontrolled usage should obtain real allocations as defined in section 6. Type value 255 is reserved for future expansion of the type value range if there should be a shortage in the future. The details of this are left for future work. One possible way of doing this that would not cause any problems with current implementations is if the type equals 255, use the code field for the new assignment. Existing implementations would ignore the new assignments as specified in section 2.4, section (b). The new messages using these expanded type values, could assign fields in the message body for it's code values. Every ICMPv6 message is preceded by an IPv6 header and zero or more IPv6 extension headers. The ICMPv6 header is identified by a Next Header value of 58 in the immediately preceding header. (NOTE: this is different than the value used to identify ICMP for IPv4.) The ICMPv6 messages have the following general format: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Code | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + Message Body + | | The type field indicates the type of the message. Its value determines the format of the remaining data. The code field depends on the message type. It is used to create an additional level of message granularity. The checksum field is used to detect data corruption in the ICMPv6 message and parts of the IPv6 header. The subclass of ICMPv6 messages used for reporting errors, i.e., those with a Type value between 0 and 127, inclusive, all have the following, more specific format: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Code | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | type-specific data (32 bits) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | As much of invoking packet | + as will fitpossible without the ICMPv6 packet + | exceeding the minimum IPv6 MTU [IPv6] | 2.2 Message Source Address Determination A node that sends an ICMPv6 message has to determine both the Source and Destination IPv6 Addresses in the IPv6 header before calculating the checksum. If the node has more than one unicast address, it MUST choose the Source Address of the message as follows: (a) If the message is a response to a message sent to one of the node's unicast addresses, the Source Address of the reply MUST be that same address. (b) If the message is a response to a message sent to a multicast or anycast group in which the node is a member, the Source Address of the reply MUST be a unicast address belonging to the interface on which the multicast or anycast packet was received. (c) If the message is a response to a message sent to an address that does not belong to the node, the Source Address SHOULD be that unicast address belonging to the node that will be most helpful in diagnosing the error. For example, if the message is a response to a packet forwarding action that cannot complete successfully, the Source Address SHOULD be a unicast address belonging to the interface on which the packet forwarding failed. (d) Otherwise, the node's routing table must be examined to determine which interface will be used to transmit the message to its destination, and a unicast address belonging to that interface MUST be used as the Source Address of the message. 2.3 Message Checksum Calculation The checksum is the 16-bit one's complement of the one's complement sum of the entire ICMPv6 message starting with the ICMPv6 message type field, prepended with a "pseudo-header" of IPv6 header fields, as specified in [IPv6, section 8.1]. The Next Header value used in the pseudo-header is 58. (NOTE: the inclusion of a pseudo-header in the ICMPv6 checksum is a change from IPv4; see [IPv6] for the rationale for this change.) For computing the checksum, the checksum field is first set to zero. 2.4 Message Processing Rules Implementations MUST observe the following rules when processing ICMPv6 messages (from [RFC-1122]): (a) If an ICMPv6 error message of unknown type is received, it MUST be passed to the upper layer. (b) If an ICMPv6 informational message of unknown type is received, it MUST be silently discarded. (c) Every ICMPv6 error message (type < 128) MUST include as much of the IPv6 offending (invoking) packet (the packet that caused the error) as will fitpossible without making the error message packet exceed the minimum IPv6 MTU [IPv6]. (d) In those cases where the internet-layer protocol is required to pass an ICMPv6 error message to the upper-layer process, the upper-layer protocol type is extracted from the original packet (contained in the body of the ICMPv6 error message) and used to select the appropriate upper-layer process to handle the error. If the original packet had an unusually large amount of extension headers, it is possible that the upper-layer protocol type may not be present in the ICMPv6 message, due to truncation of the original packet to meet the minimum IPv6 MTU [IPv6] limit. In that case, the error message is silently dropped after any IPv6-layer processing. (e) An ICMPv6 error message MUST NOT be sent as a result of receiving: (e.1) an ICMPv6 error message, or (e.2) an ICMPv6 redirect message [IPv6-DISC], or (e.3) a packet destined to an IPv6 multicast address (there are two exceptions to this rule: (1) the Packet Too Big Message - Section 3.2 - to allow Path MTU discovery to work for IPv6 multicast, and (2) the Parameter Problem Message, Code 2 - Section 3.4 - reporting an unrecognized IPv6 option that has the Option Type highest-order two bits set to 10), or (e.4) a packet sent as a link-layer multicast, (the exception from e.3 applies to this case too), or (e.5) a packet sent as a link-layer broadcast, (the exception from e.3 applies to this case too), or (e.6) a packet whose source address does not uniquely identify a single node -- e.g., the IPv6 Unspecified Address, an IPv6 multicast address, or an address known by the ICMP message sender to be an IPv6 anycast address. (f) Finally, in order to limit the bandwidth and forwarding costs incurred by sending ICMPv6 error messages, an IPv6 node MUST limit the rate of ICMPv6 error messages it sends. This situation may occur when a source sending a stream of erroneous packets fails to heed the resulting ICMPv6 error messages. A recommended method for implementing the rate-limiting function is a token bucket, limiting the average rate of transmission to N, where N can either be packets/second or a fraction of the attached link's bandwidth, but allowing up to B error messages to be transmitted in a burst, as long as the long-term average is not exceeded. Rate-limiting mechanisms which cannot cope with bursty traffic (e.g., traceroute) are not recommended; for example a simple timer-based implementation, allowing an error message every T milliseconds (even with low values for T), is not reasonable. The rate-limiting parameters SHOULD be configurable. In the case of a token-bucket implementation, the best defaults depend on where the implementation is expected to be deployed (e.g., a high-end router vs. an embedded host). For example, in a small/mid -sized device, the possible defaults could be B=10, N=10/s. NOTE: THE RESTRICTIONS UNDER (e) AND (f) ABOVE TAKE PRECEDENCE OVER ANY REQUIREMENT ELSEWHERE IN THIS DOCUMENT FOR SENDING ICMP ERROR MESSAGES. The following sections describe the message formats for the above ICMPv6 messages. 3. ICMPv6 Error Messages 3.1 Destination Unreachable Message 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Code | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Unused | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | As much of invoking packet | + as will fitpossible without the ICMPv6 packet + | exceeding the minimum IPv6 MTU [IPv6] | IPv6 Fields: Destination Address Copied from the Source Address field of the invoking packet. ICMPv6 Fields: Type 1 Code 0 - no route to destination 1 - communication with destination administratively prohibited 2 - beyond scope of source address 3 - address unreachable 4 - port unreachable 5 - source address failed ingress/egress policy 6 - reject route to destination Unused This field is unused for all code values. It must be initialized to zero by the sender and ignored by the receiver. Description A Destination Unreachable message SHOULD be generated by a router, or by the IPv6 layer in the originating node, in response to a packet that cannot be delivered to its destination address for reasons other than congestion. (An ICMPv6 message MUST NOT be generated if a packet is dropped due to congestion.) If the reason for the failure to deliver is lack of a matching entry in the forwarding node's routing table, the Code field is set to 0 (NOTE: this error can occur only in nodes that do not hold a "default route" in their routing tables). If the reason for the failure to deliver is administrative prohibition, e.g., a "firewall filter", the Code field is set to 1. If the reason for the failure to deliver is that the destination is beyond the scope of the source address, the Code field is set to 2. This condition can occur only when the scope of the source address is smaller than the scope of the destination address (e.g., when a packet has a link-local source address and a global-scope destination address) and the packet cannot be delivered to the destination without leaving the scope of the source address. If the reason for the failure to deliver can not be mapped to any of other codes, the Code field is set to 3. The example of such cases are inability to resolve the IPv6 destination address into a corresponding link address, or a link-specific problem of some sort. One specific case in which a Destination Unreachable message with a code 3 is sent is in response to a packet received by a router from a point-to-point link, destined to an address within a subnet assigned to that same link (other than one of the receiving router's own addresses). In such a case, the packet MUST NOT be forwarded back onto the arrival link. A destination node SHOULD send a Destination Unreachable message with Code 4 in response to a packet for which the transport protocol (e.g., UDP) has no listener, if that transport protocol has no alternative means to inform the sender. If the reason for the failure to deliver is that packet with this source address is not allowed due to ingress or egress filtering policies, the Code field is set to 5. If the reason for the failure to deliver is that the route to the destination is a reject route, the Code field is set to 6. This may occur if the router has been configured to reject all the traffic for a specific prefix. Codes 5 and 6 are more informative subsets of code 1. Upper layer notification A node receiving the ICMPv6 Destination Unreachable message MUST notify the upper-layer process. 3.2 Packet Too Big Message 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Code | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MTU | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | As much of invoking packet | + as will fitpossible without the ICMPv6 packet + | exceeding the minimum IPv6 MTU [IPv6] | IPv6 Fields: Destination Address Copied from the Source Address field of the invoking packet. ICMPv6 Fields: Type 2 Code Set to 0 (zero) by the sender and ignored by the receiver MTU The Maximum Transmission Unit of the next-hop link. Description A Packet Too Big MUST be sent by a router in response to a packet that it cannot forward because the packet is larger than the MTU of the outgoing link. The information in this message is used as part of the Path MTU Discovery process [PMTU]. Sending a Packet Too Big Message makes an exception to one of the rules of when to send an ICMPv6 error message, in that unlike other messages, it is sent in response to a packet received with an IPv6 multicast destination address, or a link-layer multicast or link- layer broadcast address. Upper layer notification An incoming Packet Too Big message MUST be passed to the upper-layer process. 3.3 Time Exceeded Message 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Code | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Unused | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | As much of invoking packet | + as will fitpossible without the ICMPv6 packet + | exceeding the minimum IPv6 MTU [IPv6] | IPv6 Fields: Destination Address Copied from the Source Address field of the invoking packet. ICMPv6 Fields: Type 3 Code 0 - hop limit exceeded in transit 1 - fragment reassembly time exceeded Unused This field is unused for all code values. It must be initialized to zero by the sender and ignored by the receiver. Description If a router receives a packet with a Hop Limit of zero, or a router decrements a packet's Hop Limit to zero, it MUST discard the packet and send an ICMPv6 Time Exceeded message with Code 0 to the source of the packet. This indicates either a routing loop or too small an initial Hop Limit value. An ICMPv6 Time Exceeded message with Code 1 is used to report fragment reassembly timeout, as specified in [IPv6, Section 4.5]. The rules for selecting the Source Address of this message are defined in section 2.2. Upper layer notification An incoming Time Exceeded message MUST be passed to the upper-layer process. 3.4 Parameter Problem Message 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Code | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Pointer | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | As much of invoking packet | + as will fitpossible without the ICMPv6 packet + | exceeding the minimum IPv6 MTU [IPv6] | IPv6 Fields: Destination Address Copied from the Source Address field of the invoking packet. ICMPv6 Fields: Type 4 Code 0 - erroneous header field encountered 1 - unrecognized Next Header type encountered 2 - unrecognized IPv6 option encountered Pointer Identifies the octet offset within the invoking packet where the error was detected. The pointer will point beyond the end of the ICMPv6 packet if the field in error is beyond what can fit in the maximum size of an ICMPv6 error message. Description If an IPv6 node processing a packet finds a problem with a field in the IPv6 header or extension headers such that it cannot complete processing the packet, it MUST discard the packet and SHOULD send an ICMPv6 Parameter Problem message to the packet's source, indicating the type and location of the problem. The pointer identifies the octet of the original packet's header where the error was detected. For example, an ICMPv6 message with Type field = 4, Code field = 1, and Pointer field = 40 would indicate that the IPv6 extension header following the IPv6 header of the original packet holds an unrecognized Next Header field value. Upper layer notification A node receiving this ICMPv6 message MUST notify the upper-layer process. 4. ICMPv6 Informational Messages 4.1 Echo Request Message 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Code | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Identifier | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data ... +-+-+-+-+- IPv6 Fields: Destination Address Any legal IPv6 address. ICMPv6 Fields: Type 128 Code 0 Identifier An identifier to aid in matching Echo Replies to this Echo Request. May be zero. Sequence Number A sequence number to aid in matching Echo Replies to this Echo Request. May be zero. Data Zero or more octets of arbitrary data. Description Every node MUST implement an ICMPv6 Echo responder function that receives Echo Requests and sends corresponding Echo Replies. A node SHOULD also implement an application-layer interface for sending Echo Requests and receiving Echo Replies, for diagnostic purposes. Upper layer notification Echo Request messages MAY be passed to processes receiving ICMP messages. 4.2 Echo Reply Message 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Code | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Identifier | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Data ... +-+-+-+-+- IPv6 Fields: Destination Address Copied from the Source Address field of the invoking Echo Request packet. ICMPv6 Fields: Type 129 Code 0 Identifier The identifier from the invoking Echo Request message. Sequence The sequence number from the invoking Echo Request Number message. Data The data from the invoking Echo Request message. Description Every node MUST implement an ICMPv6 Echo responder function that receives Echo Requests and sends corresponding Echo Replies. A node SHOULD also implement an application-layer interface for sending Echo Requests and receiving Echo Replies, for diagnostic purposes. The source address of an Echo Reply sent in response to a unicast Echo Request message MUST be the same as the destination address of that Echo Request message. An Echo Reply SHOULD be sent in response to an Echo Request message sent to an IPv6 multicast or anycast address. In this case, the source address of the reply MUST be a unicast address belonging to the interface on which the Echo Request message was received. The data received in the ICMPv6 Echo Request message MUST be returned entirely and unmodified in the ICMPv6 Echo Reply message. Upper layer notification Echo Reply messages MUST be passed to the process that originated an Echo Request message. An Echo Reply message MAY be passed to processes that did not originate the Echo Request message. 5. Security Considerations 5.1 Authentication and Confidentiality of ICMP messages ICMP protocol packet exchanges can be authenticated using the IP Authentication Header [IPv6-AUTH] or IP Encapsulating Security Payload Header [IPv6-ESP]. Confidentiality for the ICMP protocol packet exchanges can be achieved using IP Encapsulating Security Payload Header [IPv6-ESP]. A node SHOULD include an Authentication Header or Encapsulating Security Payload Header when sending ICMP messages if a security association for use with the IP Authentication Header or IP Encapsulating Security Payload Header exists for the destination address. The security associations may have been created through manual configuration or through the operation of some key management protocol. Received ICMP packets that have Authentication Header or Encapsulating Security Payload Header must be processed as specified in [IPv6-AUTH] and [IPv6-ESP]. The ICMP packets that fail the security processing MUST be ignored and discarded. The system administrator MAY be allowed to configure a node to ignore any ICMP messages that are not authenticated using either the Authentication Header or Encapsulating Security Payload. If provided, such a switch SHOULD default to allowing unauthenticated messages. Note that setting up Security Associations to deal with all the required ICMP packets is a very difficult task (e.g., consider the Path MTU Discovery packets). So Path MTU Discovery (and possibly some others) may not work if the node only allows authenticated ICMP packets. 5.2 ICMP Attacks ICMP messages may be subject to various attacks. A complete discussion can be found in the IP Security Architecture [IPv6-SA]. A brief discussion of such attacks and their prevention is as follows: 1. ICMP messages may be subject to actions intended to cause the receiver to believe the message came from a different source than the message originator. The protection against this attack can be achieved by applying the IPv6 Authentication mechanism [IPv6-AUTH] to the ICMP message. 2. ICMP messages may be subject to actions intended to cause the message or the reply to it go to a destination different than the message originator's intention. The protection against this attack can be achieved by using the Authentication Header [IPv6-AUTH] or the Encapsulating Security Payload Header [IPv6-ESP]. Authentication Header provides the protection against change for the source and the destination address of the IP packet. Encapsulating Security Payload Header does not provide this protection but the ICMP checksum calculation includes the source and the destination addresses and the Encapsulating Security Payload Header protects the checksum. Therefore, the combination of ICMP checksum and the Encapsulating Security Payload Header provides the protection against this attack. The protection provided by the Encapsulating Security Payload Header will not be as strong as the protection provided by the Authentication Header. 3. ICMP messages may be subject to changes in the message fields, or payload. The authentication [IPv6-AUTH] or encryption [IPv6-ESP] of the ICMP message is a protection against such actions. 4. ICMP messages may be used as attempts to perform denial of service attacks by sending back to back erroneous IP packets. An implementation that correctly followed section 2.4, paragraph (f) of this specifications, would be protected by the ICMP error rate limiting mechanism. 5. The exception number 2 of rule e.3 in section 2.4 gives the opportunity to a malicious node to cause a denial of service attack to a multicast source. A malicious node can send a multicast packet with an unknown destination option marked as mandatory with the IPv6 source address of a valid multicast source. A large number of destination nodes will send ICMP Parameter Problem Message to the multicast source causing a denial of service attack. The way multicast traffic is forwarded by the multicast routers does require the malicious node to be part of the correct multicast path i.e. near to the multicast source. This attack can only be avoided by securing the multicast traffic. The multicast source should be careful while sending multicast traffic with the destination options marked as mandatory because they can cause a denial of service attack to themselves if the destination option is unknown to a large number of destinations. 6. IANA Considerations 6.1 Procedure for new ICMPV6 Type and Code value assignments The IPv6 ICMP header [ICMPV6] contains the following fields that carry values assigned from IANA-managed name spaces: Type and Code. Code field values are defined relative to a specific Type value. Values for the IPv6 ICMP Type fields are allocated using the following procedure: 1. The IANA should allocate and permanently register new ICMPv6 type codes from IETF RFC publication. This is for all RFC types including standards track, informational, and experimental status, etc.status that originate from the IETF and have been approved by the IESG for publication. 2. IETF working groups with working group consensus and area director approval can request reclaimable ICMPV6 type code assignments from the IANA. The IANA will tag the values as "reclaimable in future". The "reclaimable in the future" tag will be removed when an RFC is published documenting the protocol as defined in 1). This will make the assignment permanent.permanent and update the reference on the IANA web pages. At the point where the ICMPv6 type values are 85% assigned, the IANA will request that theIETF will review the assignments tagged "reclaimable in the future" and make a recommendation toinform the IANA which ones canshould be reclaimed and reassigned. 3. Requests for new ICMPv6 type value assignments from outside ofthe IETF should be sent toare only made through the publication of an IETF for review. The general guideline for this review isdocument, per 1) above. Note also that the assignment should be made if there is public and open documentation of the protocol and if the assignment isdocuments published as "RFC Editor contributions" [RFC 3667] are not being usedconsidered to circumvent an existingbe IETF protocol or workdocuments. The assignment of new Code values for the Type values defined in progress.this document require standards action or IESG approval. The policy for assigning Code values for new IPv6 ICMP Types not defined in this document should be defined in the document defining the new Type values. 6.2 Assignments for this document The following should update the assignments located at: http://www.iana.org/assignments/icmpv6-parameters The IANA is requested to reassign ICMPv6 type 1 "Destination Unreachable" code 2, that was unassigned in [RFC-2463], to: 2 - beyond scope of source address The IANA is requested to assign the following two new codes values for ICMPv6 type 1 "Destination Unreachable": 5 - source address failed ingress/egress policy 6 - reject route to destination The IANA is requested to assign the following new type values: 100 Private experimentation 101 Private experimentation 200 Private experimentation 201 Private experimentation 255 Reserved for expansion 7. References 7.1 Normative [IPv6] Deering, S., R. Hinden, "Internet Protocol, Version 6, Specification", RFC2460, December 1998. [IPv6-DISC] Narten, T., E. Nordmark, W. Simpson, "Neighbor Discovery for IP Version 6 (IPv6)", RFC2461, December, 1998. [RFC-792] Postel, J., "Internet Control Message Protocol", STD 5, RFC792, September 1981. [RFC-2463] Conta, A., S. Deering, "Internet Control Message Protocol (ICMPv6) for the Internet Protocol Version 6 (IPv6) Specification", RFC2463, December, 1998. [RFC-1122] Braden, R., "Requirements for Internet Hosts - Communication Layers", STD 5, RFC1122, August 1989. [RFC-2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP14, RFC2119, March 1997. 7.2 Informative [RFC-2780] Bradner, S., V. Paxson, "IANA Allocation Guidelines For Values In the Internet Protocol and Related Headers", RFC 2780, March 2000. [IPv6-ADDR] Hinden, R., S. Deering, "IP Version 6 Addressing Architecture", RFC2373, July 1998. [PMTU] McCann, J., S. Deering, J. Mogul, "Path MTU Discovery for IP version 6", RFC1981, August 1996. [IPv6-SA] Kent, S., R. Atkinson, "Security Architecture for the Internet Protocol", RFC1825, November 1998. [IPv6-AUTH] Kent, S., R. Atkinson, "IP Authentication Header", RFC 2402, November 1998. [IPv6-ESP] Kent, S., R. Atkinson, "IP Encapsulating Security Payload (ESP)", RFC 2406, November 1998. 8. Acknowledgments The document is derived from previous ICMP drafts of the SIPP and IPng working group. The IPng working group and particularly Robert Elz, Jim Bound, Bill Simpson, Thomas Narten, Charlie Lynn, Bill Fink, Scott Bradner, Dimitri Haskin, Bob Hinden, Jun-ichiro Itojun Hagino, Tatuya Jinmei, Brian Zill, Pekka Savola, and Fred Templin (in chronological order) provided extensive review information and feedback. Mukesh Gupta andBob Hinden werewas the document editorseditor for this document. 9. Authors' Addresses Alex Conta Stephen DeeringTranswitch Corporation Cisco Systems, Inc.3 Enterprise Drive Shelton, CT 06484 USA Email: firstname.lastname@example.org Stephen Deering Cisco Systems, Inc. 170 West Tasman Drive Shelton, CT 06484San Jose, CA 95134-1706 US US email: email@example.comUSA Mukesh Gupta (ed.) Nokia 313 Fairchild Drive Mountain View, CA 94043 USA Phone: +1 650-625-2264 Email: firstname.lastname@example.org Appendix A - Changes fromsince RFC 2463 The following changes were made from RFC 2463: - Edited the Abstract to make it a little more elaborate. - Corrected typos in section 2.4, where references to sub-bullet e.2 were supposed to be references to e.3. - Removed the Timer-based and the Bandwidth-based methods from the example rate-limiting mechanism for ICMP error messages. Added Token-bucket based method. - Added specification that all ICMP error messages shall have exactly 32 bits of type-specific data, so that receivers can reliably find the embedded invoking packet even when they don't recognize the ICMP message Type. - In the description of Destination Unreachable messages, Code 3, added rule prohibiting forwarding of packets back onto point-to- point links from which they were received, if their destination addresses belong to the link itself ("anti-ping-ponging" rule). - Added description of Time Exceeded Code 1 (fragment reassembly timeout). - Added "beyond scope of source address", "source address failed ingress/egress policy", and "reject route to destination" messages to the family of "unreachable destination" type ICMP error messages (section 3.1). - Reserved some ICMP type values for experimentation. - Added a NOTE in section 2.4, that specifies ICMP message processing rules precedence. - Added ICMP REDIRECT to the list in Section 2.4 e) of cases in which ICMP error messages are not to be generated. - Made minor editorial changes in Section 2.3 on checksum calculation, and in Section 5.2. - Clarified in section 4.2, regarding the Echo Reply Message, that the source address of an Echo Reply to an anycast Echo Request should be a unicast address, as in the case of multicast. - Revised the Security Considerations section. Added the use of Encapsulating Security Payload Header for authentication. Changed the requirement of an option of "not allowing unauthenticated ICMP messages" to MAY from SHOULD. - Added a new attack in the list of possible ICMP attacks in section 5.2. - Separated References into Normative and Informative. - Added reference to RFC-2780 "IANA Allocation Guidelines For Values In the Internet Protocol and Related Headers" - Added a procedure for new ICMPv6 Type and Code value assignments in the IANA Consideration section. Full Copyright Statement Copyright (C) The Internet Society (2004). This document is subject to the rights, licenses and restrictions contained in BCP 78 and except as set forth therein, the authors retain all their rights. 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