INTERNET-DRAFT Norihiro Ishikawa NTT Nagatsugu Yamanouchi IBM Expires: September 1998 Osamu Takahashi NTT March 12, 1998 IGMP Extension for Authentication Status of this Memo This document is an Internet-Draft. 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". To learn the current status of any Internet-Draft, please check the "1id-abstracts.txt" listing contained in the Internet- Drafts Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or ftp.isi.edu (US West Coast). Abstract The security enhancement is one of the most important enhancements to IP multicast. There are no security functions in IGMP, version 2 (IGMPv2) [1]. Any host can send IP multicast datagrams to a host group. Any host can join a host group and receive IP multicast datagrams which are sent to the host group. This document describes the extensions to IGMPv2 for the authentication of sending and receiving hosts which comply with IGMPv2. Ishikawa, Yamanouchi, Takahashi Expires September 1998 [Page 1] INTERNET-DRAFT IGMP Authentication March, 1998 1. Introduction The rapid deployment of IP multicast over the Internet has been realized by MBone, an experimental IP multicast network over the Internet. IP multicast is at the experimental stage. In order to make IP multicast a commercial service, many enhancements to IP multicast are required. Among them, the security enhancement is one of the most important enhancements to IP multicast. There are no security functions in IGMPv2. Any host can send IP multicast datagrams to a host group. Any host can join a host group and receive IP multicast datagrams which are sent to the host group. There are no means to know who are the current sending and receiving hosts regarding each host group. This document describes the security extensions for IGMPv2. 2. Requirements The requirements for the security functions of IP multicast are described below. (1) Group Membership Control: An Internet Service Provider (ISP) needs to know who are the current sending and receiving hosts regarding each host group, because of the various reasons (e.g. accounting and network management). A sending host may request to know who are the current receiving hosts regarding the host group. (2) Authentication: An Internet Service Provider (ISP) needs to authenticate sending and receiving hosts regarding each host group, because of the various reasons (e.g. security and accounting). A sending host may request to send IP multicast datagrams only to receiving hosts that are authenticated. (3) IP Multicast Routing Protocols: Various IP multicast routing protocols such as DVMRP [2], PIM [3] and CBT [4] are being developed within IETF. The security functions of IP multicast must not depend on a specific IP multicast routing protocol. NOTE: Other requirements on the security functions of IP Multicast are for further study. This document describes security extensions to IGMPv2, which satisfy the above requirements. Ishikawa, Yamanouchi, Takahashi Expires September 1998 [Page 2] INTERNET-DRAFT IGMP Authentication March, 1998 3. Architecture The overall architecture for the security functions of IP multicast is described below. A sending host sends IP multicast datagrams to an ingress router in an IP multicast network. IP multicast datagrams travel towards egress routers through IP multicast routers within an IP multicast network. An IP multicast routing is controlled by IP multicast routing protocols such as DVMRP, PIM and CBT. An egress router sends IP multicast datagrams to receiving hosts which join the host group. This document describes the authentication functions of IP multicast, using the Challenge-Response mechanism in a similar way as CHAP [5]. NOTE: Other mechanisms for the authentication functions of IP Multicast are for further study. An ingress router may optionally authenticate a sending host. When a sending host wants to send IP multicast datagrams, it sends a Sender Start message to an ingress router. When a ingress router receives a Sender Start message, it sends a Challenge message to the sending host which sent the Sender Start message. When a Challenge message is received, a sending host sends a Response message to an ingress router. When a Response message is received, an ingress router compares the response value with the expected value for the authentication of the sending host. Alternatively, an ingress router may ask a RADIUS server to authenticate the sending host. NOTE: The interaction between a multicast router and a RADIUS server is described in Appendix A. The separate document [6] describes the extensions to RADIUS [7] for the authentication of sending and receiving hosts which comply with IGMPv2. If the result of the authentication is successful, an ingress router sends a Success message to a sending host. When a Success message is received, a sending host starts to send IP multicast datagrams. An egress router may optionally authenticate a receiving host. When a receiving host wants to receive IP multicast datagrams, it sends a Membership Report message to an egress router. When an egress router receives a Membership Report message, it sends a Challenge message to the receiving host which sent the Membership Report message. When a Challenge message is received, a receiving host sends a Response message to an egress router. When a Response message is received, an egress router compares the response value with the expected value for the authentication of the receiving host. Alternatively, an egress router may ask a RADIUS server to authenticate the receiving host. Ishikawa, Yamanouchi, Takahashi Expires September 1998 [Page 3] INTERNET-DRAFT IGMP Authentication March, 1998 If the result of the authentication is successful, an egress router sends a Success message to a receiving host. When a Success message is received, a receiving host starts to receive IP multicast datagrams. There are two levels of multicast routers. (1) Level 1: Unsecure Multicast Router The multicast router complies with IGMPv2. (2) Level 2: Secure Multicast Router The multicast router complies with both IGMPv2 and this document. All multicast routers in a subnetwork must be either secure or unsecure. In other words, unsecure multicast routers and secure multicast routers must not coexist in the same subnetwork. 4. Protocol Description This section describes the mechanisms for the authentication functions of IP multicast. 4.1 Procedures for Authentication of Sending Hosts 4.1.1 Operation of Sending hosts When a sending host wants to send IP multicast datagrams, it sends a Sender Start message to a multicast router. When [Retry Interval] expires, a sending host resends a Sender Start message to a multicast router, until a Challenge message is received, or [Retry Count] expires. When a Challenge message is received, A sending host sends a Response message to a multicast router. When [Retry Interval] expires, a sending host resends a Response message to a multicast router, until a Success or Failure message is received, or [Retry Count] expires. When a Success message is received, a sending host starts to send IP multicast datagrams. When a Failure message is received, a sending host is not allowed to send IP multicast datagrams. After a sending host starts to send IP multicast datagrams, it may receive a Challenge message. When a Challenge message is received, a sending host sends a Response message to a multicast router. After a sending host sends a Response message, it may receive the same Challenge message. In this case, a sending host resends the same Response message. NOTE: This is the case where a Response message was lost. Ishikawa, Yamanouchi, Takahashi Expires September 1998 [Page 4] INTERNET-DRAFT IGMP Authentication March, 1998 When [Retry Interval] expires, a sending host resends a Response message to a multicast router, until a Success or Failure message is received, or [Retry Count] expires. When a Success message is received, a sending host can continue to send IP multicast datagrams. When a Failure message is received, a sending host stops to send IP multicast datagrams. 4.1.2 Operation of Multicast Routers When a multicast router receives a Sender Start message, it sends a Challenge message to the sending host which sent the Sender Start message. After a multicast router sent the Challenge message, it may receive the same Sender Start message. In this case, a multicast router resends the same Challenge message. NOTE: This is the case where a Challenge message was lost. When a Response message is received, a multicast router compares the response value with the expected value for the authentication of the sending host. Alternatively, a multicast router may ask a RADIUS server to authenticate the sending host. If the result of the authentication is successful, a multicast router sends a Success message to the sending host. If the result of the authentication is not successful, a multicast router sends a Failure message to the sending host. After a multicast router sent the Success message, it may receive the same Response message. In this case, a multicast router resends the same Success message. NOTE: This is the case where a Success message was lost. A multicast router manages a list of IP addresses of authenticated sending hosts regarding each host group. When the authentication of the sending host is successful, a multicast router adds its IP address to the list. When a multicast router receives an IP multicast datagram from a sending host, it checks the source IP address of the received IP multicast datagram. If the source IP address was registered in the list of IP addresses of authenticated sending hosts, a multicast router forwards the received IP multicast datagram. If the source IP address was not registered in the list of IP addresses of authenticated sending hosts, a multicast router silently discards the received IP multicast datagram. The [Validity Period] of the authentication of a sending host is set in the authentication parameter of a Success message. If the [Validity Period] expires, a multicast router may reauthenticate the sending host. Ishikawa, Yamanouchi, Takahashi Expires September 1998 [Page 5] INTERNET-DRAFT IGMP Authentication March, 1998 When a multicast router reauthenticates the sending host, it sends a Challenge message. When a [Retry Interval] expires, the multicast router resends a Challenge message, until a Response message is received, or [Retry Count] expires. When a Response message is received, a multicast router compares the response value with the expected value for the authentication of the sending host. Alternatively, a multicast router may ask a RADIUS server to authenticate the sending host. If the result of the authentication is successful, a multicast router sends a Success message to the sending host. If the result of the authentication is not successful, a multicast router sends a Failure message to the sending host. After a multicast router sent the Success message, it may receive the same Response message. In this case, a multicast router resends the same Success message. NOTE: This is the case where a Success message was lost. A multicast router deletes the IP address of a sending host from a list of IP addresses of authenticated sending hosts, in the following cases. - When the [Validity Period] of the authentication of a sending host expires, a multicast router does not want to reauthenticate the sending host. - The reauthentication of a sending host is not successful. 4.2 Procedures for Authentication of Receiving Hosts 4.2.1 Operation of Receiving Hosts When a receiving host wants to receive IP multicast datagrams, it sends a Membership Report message with an authentication parameter to a multicast router. When [Retry Interval] expires, a receiving host resends a Membership Report message to a multicast router, until a Challenge message is received, or [Retry Count] expires. When a Challenge message is received, a receiving host sends a Response message to a multicast router. When [Retry Interval] expires, a receiving host resends a Response message to a multicast router, until a Success or Failure message is received, or [Retry Count] expires. When a Success message is received, a receiving host starts to receive IP multicast datagrams. When a Failure message is received, a receiving host is not allowed to receive IP multicast datagrams. When a receiving host leaves the host group, it must send a Leave message to a multicast router. NOTE: The authentication procedure for a Leave message is for further study. Ishikawa, Yamanouchi, Takahashi Expires September 1998 [Page 6] INTERNET-DRAFT IGMP Authentication March, 1998 After a receiving host starts to receive IP multicast datagrams, it may receive a Group-Specific Query message with a reason parameter (reason = "reauthentication is required"). When a Group-Specific Query message with a reason parameter (reason = "reauthentication is required") is received, a receiving host sets a delay timer to a random value selected from the range (0, Max Response Time) for the host group being queried. Max Response Time is specified in the Group-Specific Query message. If the receiving host receives another Membership Report message with an authentication parameter while the timer is running, it stops the timer for the host group and does not send a Membership Report message with an authentication parameter, in order to suppress duplicate Membership Report messages. When the timer expires, the receiving host sends a Membership Report message with an authentication parameter to a multicast router. When [Retry Interval] expires, a receiving host resends a Membership Report message to a multicast router, until a Challenge message is received, or [Retry Count] expires. When a Challenge message is received, a receiving host sends a Response message to a multicast router. When [Retry Interval] expires, a receiving host resends a Response message to a multicast router, until a Success or Failure message is received, or [Retry Count] expires. When a Success message is received, a receiving host can continue to receive IP multicast datagrams. When a Failure message is received, a sending host stops to receive IP multicast datagrams. 4.2.2 Operation of Multicast Routers When a multicast router receives a Membership Report message with an authentication parameter, it sends a Challenge message to the receiving host which sent the Membership Report message. After a multicast router sent the Challenge message, it may receive the same Membership Report message. In this case, a multicast router resends the same Challenge message. NOTE: This is the case where a Challenge message was lost. When a Response message is received, a multicast router compares the response value with the expected value for the authentication of the receiving host. Alternatively, a multicast router may ask a RADIUS server to authenticate the receiving host. If the result of the authentication is successful, a multicast router sends a Success message to the receiving host. If the result of the authentication is not successful, a multicast router sends a Failure message to the receiving host. After a multicast router sent the Success message, it may receive the same Response message. In this case, a multicast router resends the same Success message. NOTE: This is the case where a Success message was lost. Ishikawa, Yamanouchi, Takahashi Expires September 1998 [Page 7] INTERNET-DRAFT IGMP Authentication March, 1998 A multicast router manages a list of group addresses of host groups which have at least one authenticated receiving host for each of its attached networks. When the authentication of the receiving host is successful, a multicast router adds the address of the host group which the receiving host wants to join to the list, unless the address is already registered in the list. The [Validity Period] of the authentication of a receiving host is set in the authentication parameter of a Success message. If the [Validity Period] expires, a multicast router may reauthenticate the receiving host. When a multicast router reauthenticates the receiving host, it sends a Group-Specific Query message with a reason parameter ( reason = "reauthentication is required"). The Group-Specific Query message has the Max Response Time set to [Reauthentication Query Interval]. When a [Reauthentication Query Interval] expires, the multicast router resends the Group-Specific Query message, until a Membership Report message with an authentication parameter is received, or a [Retry Count] expires. When a multicast router receives a Membership Report message with an authentication parameter, it sends a Challenge message to the receiving host which sent the Membership Report message. After a multicast router sent the Challenge message, it may receive the same Membership Report message. In this case, a multicast router resends the same Challenge message. NOTE: This is the case where a Challenge message was lost. When a Response message is received, a multicast router compares the response value with the expected value for the authentication of the receiving host. Alternatively, a multicast router may ask a RADIUS server to authenticate the receiving host. If the result of the authentication is successful, a multicast router sends a Success message to the receiving host. If the result of the authentication is not successful, a multicast router sends a Failure message to the receiving host. When the result of the authentication is not successful, the multicast router resends a Group-Specific Query message with a reason parameter ( reason = "reauthentication is required"), until the authentication succeeds, or [Retry Count] expires. After a multicast router sent the Success message, it may receive the same Response message. In this case, a multicast router resends the same Success message. NOTE: This is the case where a Success message was lost. Ishikawa, Yamanouchi, Takahashi Expires September 1998 [Page 8] INTERNET-DRAFT IGMP Authentication March, 1998 A multicast router deletes the address of the host group from a list of the addresses of host groups which have at least one authenticated receiving host, in the following cases. - When the [Validity Period] of the authentication of a receiving host expires, a multicast router does not want to reauthenticate the receiving host. - The reauthentication of a receiving host is not successful. - A multicast router finds that there are no local members for the host group in accordance with IGMPv2. When a multicast router receives a Membership Report message without an authentication parameter, it silently discards the received Membership Report message, if the group address set in the Membership Report message is not registered in the list of the addresses of host groups which have at least one authenticated receiving host. NOTE: A multicast router receives a Membership Report message without an authentication parameter as the response to a Membership Query, in accordance with IGMPv2. 5. Compatibility with IGMPv2 Hosts 5.1 Compatibility with IGMPv2 Sending Hosts A sending host which only complies with IGMPv2 sends IP multicast datagrams without having any authentication procedures. In this case, a multicast router which complies with this document silently discards IP multicast datagrams received. A multicast router must be able to manually register the address of a host group to the access control list (i.e. the list of host group addresses to which an unauthenticated host may send IP multicast datagrams) managed by the multicast router, so that a sending host can send IP multicast datagrams to the host group without having any authentication procedures. 5.2 Compatibility with IGMPv2 Receiving Hosts A receiving host which only complies with IGMPv2 sends a Membership Report message without having an authentication parameter. If there exists at least one authenticated receiving host on the same subnetwork, a multicast router treats this message as a valid Membership Report message, and hence the receiving host starts to receive IP multicast datagrams. If there exists no authenticated receiving host on the same subnetwork, a multicast router silently discards this message, and hence the receiving host can not receive IP multicast datagrams. A multicast router must be able to manually register the address of a host group to the access control list managed by the multicast router, so that a Ishikawa, Yamanouchi, Takahashi Expires September 1998 [Page 9] INTERNET-DRAFT IGMP Authentication March, 1998 receiving host can receive IP multicast datagrams sent to the host group without having any authentication procedures. A multicast router treats a Membership Report message without an authentication parameter as a valid message, if its destination address (i.e. host group address) is registered in the access control list. 6. Extensions to IGMPv2 Messages The following messages and parameters are added to IGMPv2 for the security extensions. 6.1 New Messages The format of new messages is as follows. 0 1 2 3 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Max Resp Time | Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Group Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ (1) Type The types of new messages are as follows: 0x21 = Sender Start 0x22 = Challenge 0x23 = Response 0x24 = Success 0x25 = Failure (2) Max Response Time The use of this field is same as specified in IGMPv2. (3) Checksum The use of this field is same as specified in IGMPv2. (4) Group Address In a Sender Start message, the address of the host group to which a sending host wants to send IP multicast datagrams is set to the group address field. In a Challenge, Response, Success or Failure message, the group address field is set to zero. Ishikawa, Yamanouchi, Takahashi Expires September 1998 [Page 10] INTERNET-DRAFT IGMP Authentication March, 1998 6.2 Optional Parameters The following optional parameters may be set following the fixed fields of IGMP messages. The format of the optional parameters is as follows: +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Option1 | Option2 | ... | Padding | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Thus, padding is added in the end, in order to complete them in 32-bit boundary. The value of padding is zero. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Option Type | Option Data Length | Option Data | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - Option Type: An 8-bit identifier of the option type - Option Data Length: Length of the option data in octet (8 bits) - Option Data: Data specific to each option with variable length 6.2.1 Optional Parameters for the Group-Specific Query Message (1) Reason This parameter specifies the reason why the Group-Specific Query message is sent by a multicast router. Option Type: 1 The format of the option data is as follows: +-+-+-+-+-+-+-+ | Reason | +-+-+-+-+-+-+-+ Reason: This field is one octet (8 bits). This field specifies the reason why the Group-Specific Query message is sent by a multicast router. 1=a Leave Group message is received by a multicast router 2=a reauthentication is required NOTE: If this parameter is omitted, Value 1 (a Leave Group message is received) is assumed. Ishikawa, Yamanouchi, Takahashi Expires September 1998 [Page 11] INTERNET-DRAFT IGMP Authentication March, 1998 6.2.2 Optional Parameters for the Version 2 Membership Report Message and the Sender Start Message (1) Authentication This parameter of a Version 2 Membership Report message is used to authenticate an user on a receiving host which wants to receive IP multicast datagrams. This parameter of a Sender Start message is used to authenticate an user on a sending host which wants to send IP multicast datagrams. Option Type: 1 The format of the option data is as follows: +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Mechanism | Identifier | User-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Mechanism: An 8-bit identifier of the mechanism for the authentication of a receiving or sending host. 1 = the authentication mechanism specified in this document NOTE: Other authentication mechanisms are for further study. Identifier: This field is one octet (8 bits). This field is used to identify the sequence for the authentication of a receiving or sending host. When a new authentication starts, this field must be changed. User-ID: The User-ID field is one or more octets representing the identification of an user on a receiving or sending host to be authenticated. An User-ID may be ASCII character strings or an e-mail address of an user. 6.2.3 Optional Parameters for the Challenge Message and the Response Message (1) Authentication This parameter of is used to authenticate an user on a receiving host which wants to receive IP multicast datagrams and an user on a sending host which wants to send IP multicast datagrams. Option Type: 1 The format of the option data is as follows: Ishikawa, Yamanouchi, Takahashi Expires September 1998 [Page 12] INTERNET-DRAFT IGMP Authentication March, 1998 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Identifier | Value-Size | Value | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | User-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Identifier: This field is one octet (8 bits). When a Challenge message is sent, this field must be copied from the Identifier field of the preceding Version 2 Membership Report or Sender Start message. When a Response message is sent, this field must be copied from the Identifier field of the preceding Challenge message. Value-Size: This field is one octet and indicates the length of the Value field. Value: The Value field is one or more octets. The Challenge Value is a variable stream of octets. Each Challenge Value should be unique, since repetition of a challenge value in conjunction with the same secret would permit an attacker to reply with a previously intercepted response. The Challenge Value must be changed each time a Challenge message is sent. The length of the Challenge Value depends upon the method used to generate the octets, and is independent of the hash algorithm used. The Response Value is the one-way hash calculated over a stream of octets consisting of the Identifier, followed by (concatenated with) the "secret", followed by (concatenated with) the Challenge Value. The length of the Response Value depends upon the hash algorithm used. MD5 [8] is used as the hash algorithm. In the case of MD5, The length of the Response Value is 16 octets. The length of "secret" must be at least 1 octet. The "secret" should be at least as large and unguessable as a well-chosen password. User-ID: The User-ID field is one or more octets representing the identification of an user on a receiving or sending host to be authenticated. An User-ID may be ASCII character strings or an e-mail address of an user. Ishikawa, Yamanouchi, Takahashi Expires September 1998 [Page 13] INTERNET-DRAFT IGMP Authentication March, 1998 6.2.4 Optional Parameters for the Success Message (1) Authentication This parameter is used to authenticate an user on a receiving host which wants to receive IP multicast datagrams and an user on a sending host which wants to send IP multicast datagrams. Option Type: 1 The format of the option data is as follows: +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Identifier | Validity-Period | Message | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Identifier: This field is one octet (8 bits). When a Success or Failure message is sent, this field must be copied from the Identifier field of the preceding Response message. Validity-Period: This field is four octets (32 bits). This field specifies the period of the validity for the authentication of an user on a receiving or sending host in units of second. When a Success message is sent, a multicast router specifies the validity period for the authentication. Message: The Message field is zero or more octets, and its contents are implementation dependent. It is intended to be human readable, and must not affect the operation of the protocol. 6.2.5 Optional Parameters for the Failure Message (1) Authentication This parameter is used to authenticate an user on a receiving host which wants to receive IP multicast datagrams and an user on a sending host which wants to send IP multicast datagrams. Option Type: 1 The format of the option data is as follows: +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Identifier | Message | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Ishikawa, Yamanouchi, Takahashi Expires September 1998 [Page 14] INTERNET-DRAFT IGMP Authentication March, 1998 Identifier: This field is one octet (8 bits). When a Success or Failure message is sent, this field must be copied from the Identifier field of the preceding Response message. Message: The Message field is zero or more octets, and its contents are implementation dependent. It is intended to be human readable, and must not affect the operation of the protocol. 6.2.6 Optional Parameters for the Leave Group Message (1) Authentication This parameter is used to authenticate an user on a receiving host which wants to receive IP multicast datagrams. Option Type: 1 The format of the option data is as follows: +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | User-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ User-ID: The User-ID field is one or more octets representing the identification of an user on a receiving host which was authenticated when the receiving host joined the host group. An User-ID may be ASCII character strings or an e-mail address of an user. 7. List of Timers and Default Values This document defines the following timers and their default values, in addition to those defined in IGMPv2. 7.1 Retry Interval The Retry Interval is the time between repetitions of a Sender Start message, a Membership Report message, a Challenge message or a Response message during the authentication phase. Default: 10 seconds ?. 7.2 Retry Count The Retry Count is the number of Sender Start messages, Membership Report messages, Group-Specific Query message, Challenge messages or Response messages sent before the authentication procedure is abandoned. Default: the Robustness Variable. NOTE: The Robustness Variable is defined in IGMPv2. Ishikawa, Yamanouchi, Takahashi Expires September 1998 [Page 15] INTERNET-DRAFT IGMP Authentication March, 1998 7.3 Validity Period The Validity Period of the authentication of a sending or receiving host sesage Destinations in a Success message. 7.4 Reauthentication Query Interval The Reauthentication Query Interval is the Max Response Time set in a Group-Specific Query message sent when the [Validity Period] of the authentication of a receiving host expires. Default: 10 seconds ?. 8. Message Destinations The destinations of messages defined in this document are summarized below. Message Type Destination ---------------- --------------- Sender Start ALL-ROUTERS (224.0.0.2) Challenge The sending host which sent a Sender Start message, or the receiving host which sent a Membership Report message with an authentication parameter Response The multicast router which sent a Challenge message Success The sending or receiving host which sent a Response message Failure The sending or receiving host which sent a Response message 9. Security Considerations This document describes the IGMPv2 extension for authentication. Ishikawa, Yamanouchi, Takahashi Expires September 1998 [Page 16] INTERNET-DRAFT IGMP Authentication March, 1998 Appendix A. Interaction with the RADIUS Server This appendix gives an outline of the interaction between a secure multicast router and a RADIUS server. The detailed specifications of the interaction between them are described in [6]. A.1 Interaction with the RADIUS Server for the Authentication of Sending and Receiving Hosts A.1.1 Interaction with the RADIUS Server for the Authentication of Sending Hosts When a multicast router receives a Response message from a sending host, it sends an Access-Request message in RADIUS to a RADIUS server. When the multicast router receives an Access-Accept message in RADIUS from the RADIUS server, it sends a Success message to the sending host. When the multicast router receives an Access-Reject message in RADIUS, it sends a Failure message to the sending host. A.1.2 Interaction with the RADIUS Server for the Authentication of Receiving Hosts When a multicast router receives a Response message from a receiving host, it sends an Access-Request message in RADIUS to a RADIUS server. When the multicast router receives an Access-Accept message in RADIUS from the RADIUS server, it sends a Success message to the receiving host. When the multicast router receives an Access-Reject message in RADIUS, it sends a Failure message to the receiving host. A.2 Interaction with the RADIUS Accounting Server for the Group Membership Control of Receiving Hosts A RADIUS accounting server [9] may be used for the group membership control of receiving hosts. The interaction between a multicast router and a RADIUS accounting server is described below for the group membership control of receiving hosts. When the result of the authentication of a receiving host is successful, a multicast router may send an Accounting-Request (start) message to a RADIUS accounting server. When the multicast router receives a Leave message from the receiving host, it sends an Accounting-Request (stop) message to the RADIUS accounting server, if it sent the Accounting-Request (start) message to the RADIUS accounting server regarding the receiving host. Ishikawa, Yamanouchi, Takahashi Expires September 1998 [Page 17] INTERNET-DRAFT IGMP Authentication March, 1998 Appendix B. Issues B.1 Receiving Hosts on Shared Media Networks Once one receiving host on a shred media network such as Ethernet is is authenticated, a multicast router starts to send IP multicast datagrams to the network. As a result, other receiving hosts on the network can receive IP multicast datagrams, even if they are not authenticated. The most straightforward solution on this issue is the use of encryption. Encryption mechanisms for IP multicast are under development at the IPsec WG. If Encryption mechanisms for IP multicast are standardized, they could be integrated with the authentication mechanism described in this document. B.2 Granularity on Filtering of IP multicast Datagrams An ingress router drops IP multicast datagrams sent from unauthenticated sending hosts, based on only their source IP addresses, even if user-IDs are used for authenticating sending hosts. B.3 Quick detection of Sender Leave When the reauthentication of a sending host fails, a multicast router detects the leave of the sending host. To detect the leave of a sending host more quickly, it is necessary to define a new message (i.e. Sender Stop message). When a sending host stops sending IP multicast datagrams, it sends a Sender Stop message to a multicast router. When a multicast router receives a Sender Stop message from a sending host, A multicast router detects the leave of a sending host. This mechanism allows a multicast router to detect the leave of a sending host more quickly. Ishikawa, Yamanouchi, Takahashi Expires September 1998 [Page 18] INTERNET-DRAFT IGMP Authentication March, 1998 References [1] W. Fenner, "Internet Group Management Protocol, Version 2", RFC 2236, Xerox PARC, November 1997. [2] D. Waitzman, C. Partridge, S. Deering, "Distance Vector Multicast Routing Protocolモ, RFC 1075, November 1988. [3] D. Estrin et al., "Protocol Independent Multicast-Sparse Mode (PIM-SM): Protocol Specificationモ, RFC 2117, June 1997. [4] A. Ballardie, "Core Based Tree (CBT version2) Multicast Routing: Protocol Specificationモ, RFC 2189, September 1997. [5] W. Simson, "PPP Challenge Handshake Authentication Protocol (CHAP)", RFC 1994, August 1996. [6] N. Yamanouchi et al, "RADIUS Extension for Multicast Router Authentication", Internet Draft, March 1998. [7] C. Rigney, A. Rubens, W. Simpson, S. Willens, "Remote Authentication Dial In User Service (RADIUS)", RFC 2138, April 1997. [8] R. Rivest, S. Dusse, "The MD5 Message-Digest Algorithm", RFC 1321, April 1992. [9] C. Rigney, "RADIUS Accounting", RFC 2139, Livingston, April 1997. Acknowledgements Authors' Address: Norihiro Ishikawa NTT Information and Communication Systems Laboratory 1-1 Hikarino-oka Yokosuka-Shi Kanagawa 239 Japan isic@isl.ntt.co.jp +81 468 59 2434 (tel) +81 468 59 3796 (fax) Ishikawa, Yamanouchi, Takahashi Expires September 1998 [Page 19] INTERNET-DRAFT IGMP Authentication March, 1998 Nagatsugu Yamanouchi IBM Research, Tokyo Research Laboratory IBM Japan, Ltd. 1623-14, Shimotsuruma, Yamato-shi, Kanagawa 242, Japan yamanouc@trl.ibm.co.jp +81 462 73 5150 (tel) +81 462 74 4282 (fax) Osamu Takahashi NTT Information and Communication Systems Laboratory 1-1 Hikarino-oka Yokosuka-Shi Kanagawa 239 Japan osamu@isl.ntt.co.jp +81 468 59 2415 (tel) +81 468 59 3796 (fax) Ishikawa, Yamanouchi, Takahashi Expires September 1998 [Page 20]