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EXPERIMENTAL
Network Working Group B. FeinsteinRequest for Comments: 4767 SecureWorks, Inc.Category: Experimental G. Matthews CSC/NASA Ames Research Center March 2007The Intrusion Detection Exchange Protocol (IDXP)Status of This Memo This memo defines an Experimental Protocol for the Internet community. It does not specify an Internet standard of any kind. Discussion and suggestions for improvement are requested. Distribution of this memo is unlimited.Copyright Notice Copyright (C) The IETF Trust (2007).Abstract This memo describes the Intrusion Detection Exchange Protocol (IDXP), an application-level protocol for exchanging data between intrusion detection entities. IDXP supports mutual-authentication, integrity, and confidentiality over a connection-oriented protocol. The protocol provides for the exchange of IDMEF messages, unstructured text, and binary data. The IDMEF message elements are described inRFC 4765, "The Intrusion Detection Message Exchange Format (IDMEF)", a companion document of the Intrusion Detection Exchange Format Working Group (IDWG) of the IETF.Table of Contents1. Introduction ....................................................31.1. Purpose ....................................................31.2. Profiles ...................................................31.3. Terminology ................................................32. The Model .......................................................42.1. Connection Provisioning ....................................42.2. Data Transfer ..............................................62.3. Connection Teardown ........................................72.4. Trust Model ................................................83. The IDXP Profile ................................................83.1. IDXP Profile Overview ......................................83.2. IDXP Profile Identification and Initialization .............93.3. IDXP Profile Message Syntax ................................93.4. IDXP Profile Semantics .....................................9Feinstein & Matthews Experimental [Page 1]
RFC 4767 IDXP March 20073.4.1. The IDXP-Greeting Element ..........................103.4.2. The Option Element .................................113.4.3. The IDMEF-Message Element ..........................124. IDXP Options ...................................................124.1. The channelPriority Option ................................134.2. The streamType Option .....................................145. Fulfillment of IDWG Communications Protocol Requirements .......165.1. Reliable Message Transmission .............................165.2. Interaction with Firewalls ................................165.3. Mutual Authentication .....................................165.4. Message Confidentiality ...................................175.5. Message Integrity .........................................175.6. Per-Source Authentication .................................175.7. Denial of Service .........................................185.8. Message Duplication .......................................186. Extending IDXP .................................................187. IDXP Option Registration Template ..............................198. Initial Registrations ..........................................198.1. Registration: The IDXP Profile ............................19 8.2. Registration: The System (Well-Known) TCP Port Number for IDXP ...........................................198.3. Registration: The channelPriority Option ..................208.4. Registration: The streamType Option .......................209. The DTDs .......................................................209.1. The IDXP DTD ..............................................209.2. The channelPriority Option DTD ............................229.3. The streamType DTD ........................................2310. Reply Codes ...................................................2411. Security Considerations .......................................2511.1. Use of the TUNNEL Profile ................................2511.2. Use of Underlying Security Profiles ......................2512. IANA Considerations ...........................................2513. References ....................................................2613.1. Normative References .....................................2613.2. Informative References ...................................2614. Acknowledgements ..............................................26Feinstein & Matthews Experimental [Page 2]
RFC 4767 IDXP March 20071. Introduction IDXP is specified, in part, as a Blocks Extensible Exchange Protocol (BEEP) [4] "profile". BEEP is a generic application protocol framework for connection-oriented, asynchronous interactions. Features such as authentication and confidentiality are provided through the use of other BEEP profiles. Accordingly, many aspects of IDXP (e.g., confidentiality) are provided within the BEEP framework.1.1. Purpose IDXP provides for the exchange of IDMEF [2] messages, unstructured text, and binary data between intrusion detection entities. Addressing the security-sensitive nature of exchanges between intrusion detection entities, underlying BEEP security profiles should be used to offer IDXP the required set of security properties. SeeSection 5 for a discussion of how IDXP fulfills the IDWG communications protocol requirements. SeeSection 11 for a discussion of security considerations. IDXP is primarily intended for the exchange of data created by intrusion detection entities. IDMEF [2] messages should be used for the structured representation of this intrusion detection data, although IDXP may be used to exchange unstructured text and binary data.1.2. Profiles There are several BEEP profiles discussed, the first of which we define in this memo: The IDXP Profile The TUNNEL Profile [3] The Simple Authentication and Security Layer (SASL) Family of Profiles (see Section 4.1 of [4]) The TLS Profile (see Section 3.1 of [4])1.3. Terminology 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 inBCP 14,RFC 2119 [1].Feinstein & Matthews Experimental [Page 3]
RFC 4767 IDXP March 2007 Throughout this memo, the terms "analyzer" and "manager" are used in the context of the Intrusion Detection Message Exchange Requirements [5]. In particular, Section 2.2 of [5] defines a collection of intrusion detection terms. The terms "peer", "initiator", "listener", "client", and "server", and the characters "I", "L", "C", and "S" are used in the context of BEEP [4]. In particular,Section 2.1 of BEEP discusses the roles that a BEEP peer may perform. The term "Document Type Definition" is abbreviated as "DTD" and is defined inSection 2.8 of the Extensible Markup Language (XML) [7]. Note that the term "proxy" is specific to IDXP and does not exist in the context of BEEP. The term "intrusion detection" is abbreviated as "ID".2. The Model2.1. Connection Provisioning Intrusion detection entities using IDXP to transfer data are termed IDXP peers. Peers can exist only in pairs, and these pairs communicate over a single BEEP session with one or more BEEP channels opened for transferring data. Peers are either managers or analyzers, as defined in Section 2.2 of [5]. The relationship between analyzers and managers is potentially many- to-many. That is, an analyzer MAY communicate with many managers; similarly, a manager MAY communicate with many analyzers. Likewise, the relationship between different managers is potentially many-to- many, so that a manager MAY receive the alerts sent by a large number of analyzers by receiving them through intermediate managers. Analyzers MUST NOT establish IDXP exchanges with other analyzers. An IDXP peer wishing to establish IDXP communications with another IDXP peer does so by opening a BEEP channel, which may entail initiating a BEEP session. A BEEP security profile offering the required security properties SHOULD initially be negotiated (seeSection 11 for a discussion of security considerations). Following the successful negotiation of the BEEP security profile, IDXP greetings are exchanged and connection provisioning proceeds. In the following sequence, the peer 'Alice' initiates an IDXP exchange with the peer 'Bob'.Feinstein & Matthews Experimental [Page 4]
RFC 4767 IDXP March 2007 Alice Bob ---------------- xport connect(1) ------------------> <-------------------- greeting ----------------------> <-------------start security profile(2) -------------> <-------------------- greeting ----------------------> <------------------ start IDXP(3) -------------------> Notes: (1) 'Alice' initiates a transport connection to 'Bob', triggering the exchange of BEEP greeting messages. (2) Both entities negotiate the use of a BEEP security profile. (3) Both entities negotiate the use of the IDXP profile. In between a pair of IDXP peers may be an arbitrary number of proxies. A proxy may be necessary for administrative reasons, such as running on a firewall to allow restricted access. Another use might be one proxy per company department, which forwards data from the analyzer peers in the department onto a company-wide manager peer. A BEEP tuning profile MAY be used to create an application-layer tunnel that transparently forwards data over a chain of proxies. The TUNNEL profile [3] SHOULD be used for this purpose; see [3] for more detail concerning the options available to set up an application- layer tunnel using TUNNEL, and seeSection 11.1 for a discussion of TUNNEL-related security considerations. TUNNEL MUST be offered as a tuning profile for the creation of application-layer tunnels. The TUNNEL profile MUST offer the use of some form of SASL authentication (see Section 4.1 of [4]). Once a tunnel has been created, a BEEP security profile offering the required security properties SHOULD be negotiated, followed by negotiation of the IDXP profile. The following sequence shows how TUNNEL might be used to create an application-layer tunnel through which IDXP would operate. A peer 'Alice' initiates the creation of a BEEP session using the IDXP profile with the entity 'Bob' by first contacting 'proxy1'. In the greeting exchange between 'Alice' and 'proxy1', the TUNNEL profile is selected, and subsequently the use of the TUNNEL profile is extended to reach through 'proxy2' to 'Bob'.Feinstein & Matthews Experimental [Page 5]
RFC 4767 IDXP March 2007 Alice proxy1 proxy2 Bob -- xport connect --> <---- greeting -----> -- start TUNNEL ---> - xport connect(1) -> <----- greeting -----> --- start TUNNEL ---> --- xport connect --> <----- greeting -----> --- start TUNNEL ---> <----- <ok>(2) ------ <------- <ok> ------- <------ <ok> ------- <------------------------- greeting --------------------------> <------------------ start security profile -------------------> <------------------------- greeting --------------------------> <------------------------ start IDXP -------------------------> Notes: (1) Instead of immediately acknowledging the request from 'Alice' to start TUNNEL, 'proxy1' attempts to establish use of TUNNEL with 'proxy2'. 'proxy2' also delays its acknowledgment to 'proxy1'. (2) 'Bob' acknowledges the request from 'proxy2' to start TUNNEL, and this acknowledgment propagates back to 'Alice' so that a TUNNEL application-layer tunnel is established from 'Alice' to 'Bob'.2.2. Data Transfer Between a pair of ID entities communicating over a BEEP session, one or more BEEP channels MAY be opened using the IDXP profile. If desired, additional BEEP sessions MAY be established to offer additional channels using the IDXP profile. However, in most situations additional channels using the IDXP profile SHOULD be opened within an existing BEEP session, as opposed to provisioning a new BEEP session containing the additional channels using the IDXP profile. Peers assume the role of client or server on a per-channel basis, with one acting as the client and the other as the server. A peer's role of client or server is determined independent of whether the peer assumed the role of initiator or listener during the BEEP session establishment. Clients and servers act as sources and sinks, respectively, for exchanging data.Feinstein & Matthews Experimental [Page 6]
RFC 4767 IDXP March 2007 In a simple case, an analyzer peer sends data to a manager peer. For example, +----------+ +----------+ | | | | | |****** BEEP session ******| | | | | | | Analyzer | ----- IDXP profile ----> | Manager | | (Client) | | (Server) | | | | | | |**************************| | | | | | +----------+ +----------+ Use of multiple BEEP channels in a BEEP session facilitates categorization and prioritization of data sent between IDXP peers. For example, a manager 'M1', sending alert data to another manager, 'M2', may choose to open a separate channel to exchange different categories of alerts. 'M1' would act as the client on each of these channels, and manager 'M2' can then process and act on the incoming alerts based on their respective channel categorizations. SeeSection 4 for more detail on how to incorporate categorization and/or prioritization into channel creation. +----------+ +----------+ | | | | | |*************** BEEP session ***************| | | | | | | | -- IDXP profile, network-based alerts ---> | | | Manager | | Manager | | M1 | ---- IDXP profile, host-based alerts ----> | M2 | | (Client) | | (Server) | | | ------ IDXP profile, other alerts -------> | | | | | | | |********************************************| | | | | | +----------+ +----------+2.3. Connection Teardown An IDXP peer may choose to close an IDXP channel under many different circumstances (e.g., an error in processing has occurred). To close a channel, the peer sends a "close" element (see Section 2.3.1.3 of [4]) on channel zero indicating which channel is being closed. An IDXP peer may also choose to close an entire BEEP session by sending a "close" element indicating that channel zero is to be closed.Feinstein & Matthews Experimental [Page 7]
RFC 4767 IDXP March 2007 Section 2.3.1.3 of [4] offers a more complete discussion of the circumstances under which a BEEP peer is permitted to close a channel and the mechanisms for doing so. It is anticipated that due to the overhead of provisioning an application-layer tunnel and/or a BEEP security profile, BEEP sessions containing IDXP channels will be long-lived. In addition, the repeated overhead of IDXP channel provisioning (i.e., the exchange of IDXP greetings) may be avoided by keeping IDXP channels open even while data is not actively being exchanged on them. These are recommendations and, as such, IDXP peers may choose to close and re-provision BEEP sessions and/or IDXP channels as they see fit.2.4. Trust Model In our model, trust is placed exclusively in the IDXP peers. Proxies are always assumed to be untrustworthy. A BEEP security profile is used to establish end-to-end security between pairs of IDXP peers, doing away with the need to place trust in any intervening proxies. Only after successful negotiation of the underlying security profile are IDXP peers to be trusted. Only BEEP security profiles offering at least the protections required by Section 5 of [5] should be used to secure a BEEP session containing channels using the IDXP profile. See Section 3 of [4] for the registration of the TLS profile, an example of a BEEP security profile meeting the requirements of Section 5 of [5]. SeeSection 5 for a discussion of how IDXP fulfills the IDWG communications protocol requirements.3. The IDXP Profile3.1. IDXP Profile Overview The IDXP profile provides a mechanism for exchanging information between intrusion detection entities. A BEEP tuning profile MAY be used to create an application-layer tunnel that transparently forwards data over a chain of proxies. The TUNNEL profile [3] SHOULD be used for this purpose; see [3] for more detail concerning the options available to set up an application-layer tunnel using TUNNEL, and seeSection 11.1 for a discussion of TUNNEL-related security considerations. TUNNEL MUST be offered as a tuning profile for the creation of application-layer tunnels. The TUNNEL profile MUST offer the use of some form of SASL authentication (see Section 4.1 of [4]). The TLS profile SHOULD be used to provide the required combination of mutual-authentication, integrity, and confidentiality for the IDXP profile. For further discussion of application-layer tunnel and security issues, see Sections2.1 and11.Feinstein & Matthews Experimental [Page 8]
RFC 4767 IDXP March 2007 The IDXP profile supports several elements of interest: o The "IDXP-Greeting" element identifies an analyzer or manager at one end of a BEEP channel to the analyzer or manager at the other end of the channel. o The "Option" element is used to convey optional channel parameters between peers during the exchange of "IDXP-Greeting" elements. This element is OPTIONAL. o The "IDMEF-Message" element carries the structured information to be exchanged between the peers.3.2. IDXP Profile Identification and Initialization The IDXP profile is identified ashttp://idxp.org/beep/profile in the BEEP "profile" element during channel creation. During channel creation, "IDXP-Greeting" elements MUST be mutually exchanged between the peers. An "IDXP-Greeting" element MAY be contained within the corresponding "profile" element in the BEEP "start" element. Including an "IDXP-Greeting" element in the initial "start" element has exactly the same semantics as passing it as the first "MSG" message on the channel. If channel creation is successful, then before sending the corresponding reply, the BEEP peer processes the "IDXP-Greeting" element and includes the resulting response in the reply. This response will be an "ok" element or an "error" element. The choice of which element is returned is dependent on local provisioning of the peer.3.3. IDXP Profile Message Syntax BEEP messages in the profile MUST have a MIME Content-Type [8] of "text/xml", "text/plain", or "application/octet-stream". The syntax of the individual elements is specified inSection 9.1 of this document and Section 4 of [2].3.4. IDXP Profile Semantics Each BEEP peer issues the "IDXP-Greeting" element using "MSG" messages. The "IDXP-Greeting" element MAY contain one or more "Option" sub-elements, conveying optional channel parameters. Each BEEP peer then issues "ok" in "RPY" messages or "error" in "ERR" messages. (See Section 2.3.1 of [4] for the definitions of the "error" and "ok" elements.) An "error" element MAY be issued withinFeinstein & Matthews Experimental [Page 9]
RFC 4767 IDXP March 2007 a "RPY" message when piggy-backed within a BEEP "profile" element. SeeSection 3.4.1 for an example of an "error" element being issued within a "RPY" message. Based on the respective client/server roles negotiated during the exchange of "IDXP-Greeting" elements, the client sends data using "MSG" messages. Depending on the MIME Content-Type, this data may be an "IDMEF-Message" element, plain text, or binary. The server then issues "ok" in "RPY" messages or "error" in "ERR" messages.3.4.1. The IDXP-Greeting Element The "IDXP-Greeting" element serves to identify the analyzer or manager at one end of the BEEP channel to the analyzer or manager at the other end of the channel. The "IDXP-Greeting" element MUST include the role of the peer on the channel (client or server) and the Uniform Resource Identifier (URI) [6] of the peer. In addition, the "IDXP-Greeting" element MAY include the fully qualified domain name (see [9]) of the peer. One or more "Option" sub-elements MAY be present. An "IDXP-Greeting" element MAY be sent by either peer at any time. The peer receiving the "IDXP-Greeting" MUST respond with an "ok" (indicating acceptance), or an "error" (indicating rejection). A peer's identity and role on a channel and any optional channel parameters are, in effect, specified by the most recent "IDXP- Greeting" it sent that was answered with an "ok". An "IDXP-Greeting" may be rejected (with an "error" element) under many circumstances. These include, but are not limited to, authentication failure, lack of authorization to connect under the specified role, the negotiation of an inadequate cipher suite, or the presence of a channel option that must be understood but was unrecognized. For example, a successful creation with an embedded "IDXP-Greeting" might look like this: I: MSG 0 10 . 1592 187 I: Content-Type: text/xml I: I: <start number='1'> I: <profile uri='http://idxp.org/beep/profile'> I: <![CDATA[ <IDXP-Greeting uri='http://example.com/alice' I: role='client' /> ]]> I: </profile> I: </start> I: END L: RPY 0 10 . 1865 91Feinstein & Matthews Experimental [Page 10]
RFC 4767 IDXP March 2007 L: Content-Type: text/xml L: L: <profile uri='http://idxp.org/beep/profile'> L: <![CDATA[ <ok /> ]]> L: </profile> L: END L: MSG 0 11 . 1956 61 L: Content-Type: text/xml L: L: <IDXP-Greeting uri='http://example.com/bob' role='server' /> L: END I: RPY 0 11 . 1779 7 I: Content-Type: text/xml I: I: <ok /> I: END A creation with an embedded "IDXP-Greeting" that fails might look like this: I: MSG 0 10 . 1776 185 I: Content-Type: text/xml I: I: <start number='1'> I: <profile uri='http://idxp.org/beep/profile'> I: <![CDATA[ <IDXP-Greeting uri='http://example.com/eve' I: role='client' /> ]]> I: </profile> I: </start> I: END L: RPY 0 10 . 1592 182 L: Content-Type: text/xml L: L: <profile uri='http://idxp.org/beep/profile'> L: <![CDATA[ L: <error code='530'>'http://example.com/eve' must first L: negotiate the TLS profile</error> ]]> L: </profile> L: END3.4.2. The Option Element If present, the "Option" element MUST be contained within an "IDXP- Greeting" element. An individual "IDXP-Greeting" element MAY contain one or more "Option" sub-elements. Each "Option" element within an "IDXP-Greeting" element represents a request to enable an IDXP option on the channel being negotiated. SeeSection 4 for a complete description of IDXP options and the "Option" element.Feinstein & Matthews Experimental [Page 11]
RFC 4767 IDXP March 20073.4.3. The IDMEF-Message Element The "IDMEF-Message" element carries the information to be exchanged between the peers. See Section 4 of [2] for the definition of this element.4. IDXP Options IDXP provides a service for the reliable exchange of data between intrusion detection entities. Options are used to alter the semantics of the service. The specification of an IDXP option MUST define o the identity of the option; o what content, if any, is contained within the option; and o the processing rules for the option. An option registration template (seeSection 7) organizes this information. An "Option" element is contained within an "IDXP-Greeting" element. The "IDXP-Greeting" element itself MAY contain one or more "Option" elements. The "Option" element has several attributes and contains arbitrary content: o the "internal" and the "external" attributes, exactly one of which MUST be present, uniquely identify the option; o the "mustUnderstand" attribute, whose presence is OPTIONAL and whose default value is "false", specifies whether the option, if unrecognized, MUST cause an error in processing to occur; and o the "localize" attribute, whose presence is OPTIONAL, specifies one or more language tokens, each identifying a desirable language tag to be used if textual diagnostics are returned to the originator. The value of the "internal" attribute is the IANA-registered name for the option. If the "internal" attribute is not present, then the value of the "external" attribute is a URI or URI with a fragment- identifier. Note that a relative-URI value is not allowed. The "mustUnderstand" attribute specifies whether the peer may ignore the option if it is unrecognized. If the value of the "mustUnderstand" attribute is "true", and if the peer does notFeinstein & Matthews Experimental [Page 12]
RFC 4767 IDXP March 2007 recognize the option, then an error in processing has occurred. When absent, the value of the "mustUnderstand" attribute is defined to be "false".4.1. The channelPriority OptionSection 8.3 contains the IDXP option registration for the "channelPriority" option. This option contains a "channelPriority" element (seeSection 9.2). By default, IDXP does not place any requirements on how peers should manage multiple IDXP channels. The "channelPriority" option provides a way for peers using multiple IDXP channels to request relative priorities for each channel. When sending an "IDXP-Greeting" element during the provisioning of an IDXP channel, the originating peer MAY request that the remote peer assign a priority to the channel by including an "Option" element containing a "channelPriority" element. The "channelPriority" element has one attribute named "priority", of range 0..2147483647. This attribute is REQUIRED. Not coincidentally, this is the maximum range of possible BEEP channel numbers. 0 is defined to represent the highest priority, with relative priority decreasing as the "priority" value ascends. For example, during the exchange of "IDXP-Greeting" elements during channel provisioning, an analyzer successfully requests that a manager assign a priority to the channel: analyzer manager --------------- greeting w/ option -----------------> <---------------------- <ok> ------------------------ C: MSG 1 17 . 1984 165 C: Content-Type: text/xml C: C: <IDXP-Greeting uri='http://example.com/alice' role='client'> C: <Option internal='channelPriority'> C: <channelPriority priority='0' /> C: </Option> C: </IDXP-Greeting> C: END S: RPY 1 17 . 2001 7 S: Content-Type: text/xml S: S: <ok /> S: ENDFeinstein & Matthews Experimental [Page 13]
RFC 4767 IDXP March 2007 For example, during the exchange of "IDXP-Greeting" elements during channel provisioning, a manager unsuccessfully requests that an analyzer assign a priority to the channel: analyzer manager <---------------- greeting w/ option ---------------- --------------------- <error> ----------------------> S: MSG 1 17 . 1312 194 S: Content-Type: text/xml S: S: <IDXP-Greeting uri='http://example.com/bob' role='server'> S: <Option internal='channelPriority' mustUnderstand='true'> S: <channelPriority priority='2147483647' /> S: </Option> S: </IDXP-Greeting> S: END C: ERR 1 17 . 451 68 C: Content-Type: text/xml C: C: <error code='504'>'channelPriority' option was unrecognized</error> C: END4.2. The streamType OptionSection 8.4 contains the IDXP option registration for the "streamType" option. This option contains a "streamType" element (seeSection 9.3). By default, IDXP provides no explicit method for categorizing channels. The "streamType" option provides a way for peers to request that a channel be categorized as a particular stream type. When sending an "IDXP-Greeting" element during the provisioning of an IDXP channel, the originating peer MAY request that the remote peer assign a stream type to the channel by including an "Option" element containing a "streamType" element. The "streamType" element has one attribute named "type", with the possible values of "alert", "heartbeat", or "config". This attribute is REQUIRED. A value of "alert" indicates that the channel should be categorized as being used for the exchange of ID alerts. A value of "heartbeat" indicates that the channel should be categorized as being used for the exchange of heartbeat messages such as the "Heartbeat" element (see Section 4 of [2]). A value of "config" indicates that the channel should be categorized as being used for the exchange of configuration messages.Feinstein & Matthews Experimental [Page 14]
RFC 4767 IDXP March 2007 For example, during the exchange of "IDXP-Greeting" elements during channel provisioning, an analyzer successfully requests that a manager assign a stream type to the channel: analyzer manager --------------- greeting w/ option -----------------> <---------------------- <ok> ------------------------ C: MSG 1 21 . 1963 155 C: Content-Type: text/xml C: C: <IDXP-Greeting uri='http://example.com/alice' role='client'> C: <Option internal='streamType'> C: <streamType type='alert' /> C: </Option> C: </IDXP-Greeting> C: END S: RPY 1 21 . 1117 7 S: Content-Type: text/xml S: S: <ok /> S: END For example, during the exchange of "IDXP-Greeting" elements during channel provisioning, a manager unsuccessfully requests that an analyzer assign a stream type to the channel: analyzer manager <---------------- greeting w/ option ---------------- --------------------- <error> ----------------------> S: MSG 1 21 . 1969 176 S: Content-Type: text/xml S: S: <IDXP-Greeting uri='http://example.com/bob' role='server'> S: <Option internal='streamType' mustUnderstand='true'> S: <streamType type='config' /> S: </Option> S: </IDXP-Greeting> S: END C: ERR 1 21 . 1292 63 C: Content-Type: text/xml C: C: <error code='504'>'streamType' option was unrecognized</error> C: ENDFeinstein & Matthews Experimental [Page 15]
RFC 4767 IDXP March 20075. Fulfillment of IDWG Communications Protocol Requirements The following lists each of the communications protocol requirements established in Section 5 of [5] and, for each requirement, describes the manner in which it is fulfilled. IDXP itself does not fulfill each of the communications protocol requirements, but instead relies on the underlying BEEP protocol and a variety of BEEP profiles.5.1. Reliable Message Transmission "The [protocol] MUST support reliable transmission of messages." See Section 5.1 of [5]. IDXP operates over BEEP, which operates only over reliable connection-oriented transport protocols (e.g., TCP). In addition, BEEP peers communicate using a simple request-response protocol, which provides end-to-end reliability between peers.5.2. Interaction with Firewalls "The [protocol] MUST support transmission of messages between ID components across firewall boundaries without compromising security." See Section 5.2 of [5]. The TUNNEL profile [3] MUST be offered as an option for creation of application-layer tunnels to allow operation across firewalls. The TUNNEL profile SHOULD be used to provide an application-layer tunnel. The ability to authenticate hosts during the creation of an application-layer tunnel MUST be provided by the mechanism chosen to create such tunnels. A firewall may therefore be configured to authenticate all hosts attempting to tunnel into the protected network. If the TUNNEL profile is used, SASL (see Section 4.1 of [4]) MUST be offered as a mechanism by which hosts can be authenticated.5.3. Mutual Authentication "The [protocol] MUST support mutual authentication of the analyzer and the manager to each other." See Section 5.3 of [5]. IDXP supports mutual authentication of the peers through the use of an appropriate underlying BEEP security profile. The TLS profile and members of the SASL family of profiles (seeSection4.1 of [4]) are examples of security profiles that may be used to authenticate the identity of communicating ID components. TLS MUST be offered as a mechanism to provide mutual authentication, and TLS SHOULD be used to provide mutual authentication.Feinstein & Matthews Experimental [Page 16]
RFC 4767 IDXP March 20075.4. Message Confidentiality "The [protocol] MUST support confidentiality of the message content during message exchange. The selected design MUST be capable of supporting a variety of encryption algorithms and MUST be adaptable to a wide variety of environments." See Section 5.4 of [5]. IDXP supports confidentiality through the use of an appropriate underlying BEEP security profile. The TLS profile is an example of a security profile that offers confidentiality. The TLS profile with the TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA cipher suite MUST be offered as a mechanism to provide confidentiality, and TLS with this cipher suite SHOULD be used to provide confidentiality. The TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA cipher suite uses ephemeral Diffie-Hellman (DHE) with DSS signatures for key exchange and triple DES (Data Encryption Standard) (3DES) and cipher-block chaining (CBC) for encryption. Stronger cipher suites are optional.5.5. Message Integrity "The [protocol] MUST ensure the integrity of the message content. The selected design MUST be capable of supporting a variety of integrity mechanisms and MUST be adaptable to a wide variety of environments." See Section 5.5 of [5]. IDXP supports message integrity through the use of an appropriate underlying BEEP security profile. The TLS profile and members of the SASL family of profiles (see Section 4.1 of [4]) are examples of security profiles that offer message integrity. The TLS profile with the TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA cipher suite MUST be offered as a mechanism to provide integrity, and TLS with this cipher suite SHOULD be used to provide integrity. The TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA cipher suite uses the Secure Hash Algorithm (SHA) for integrity protection using a keyed message authentication code. Stronger cipher suites are optional.5.6. Per-Source Authentication "The [protocol] MUST support separate authentication keys for each sender." See Section 5.6 of [5]. IDXP supports separate authentication keys for each sender (i.e., per-source authentication) through the use of an appropriate underlying BEEP security profile. The TLS profile is an example of a security profile that supports per-source authentication through the mutual authentication of public-key certificates. TLS MUST be offered as a mechanism to provide per-sourceFeinstein & Matthews Experimental [Page 17]
RFC 4767 IDXP March 2007 authentication, and TLS SHOULD be used to provide per-source authentication.5.7. Denial of Service "The [protocol] SHOULD resist protocol denial-of-service attacks." See Section 5.7 of [5]. IDXP supports resistance to denial of service (DoS) attacks through the use of an appropriate underlying BEEP security profile. BEEP peers offering the IDXP profile MUST offer the use of TLS with the TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA cipher suite, and SHOULD use TLS with that cipher suite. To resist DoS attacks it is helpful to discard traffic arising from a non-authenticated source. BEEP peers MUST support the use of authentication in conjunction with any mechanism used to create application-layer tunnels. In particular, the use of some form of SASL authentication (see Section 4.1 of [4]) MUST be offered to provide authentication in the use of the TUNNEL profile. See Section 7 of [3] for a discussion of security considerations in the use of the TUNNEL profile.5.8. Message Duplication "The [protocol] SHOULD resist malicious duplication of messages." See Section 5.8 of [5]. IDXP supports resistance to malicious duplication of messages (i.e., replay attacks) through the use of an appropriate underlying BEEP security profile. The TLS profile is an example of a security profile offering resistance to replay attacks. The TLS profile with the TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA cipher suite MUST be offered as a mechanism to provide resistance against replay attacks, and TLS with this cipher suite SHOULD be used to provide resistance against replay attacks. The TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA cipher suite uses cipher-block chaining (CBC) to ensure that even if a message is duplicated the cipher-text duplicate will produce a very different plain-text result. Stronger cipher suites are optional.6. Extending IDXP The specification of IDXP options (seeSection 4) is the preferred method of extending IDXP. In order to extend IDXP, an IDXP option SHOULD be documented in an RFC and MUST be registered with the IANA (seeSection 7). IDXP extensions that cannot be expressed as IDXP options MUST be documented in an RFC.Feinstein & Matthews Experimental [Page 18]
RFC 4767 IDXP March 20077. IDXP Option Registration Template When an IDXP option is registered, the following information is supplied: Option Identification: specify the NMTOKEN or the URI that authoritatively identifies this option. Contains: specify the XML content that is contained within the "Option" element. Processing Rules: specify the processing rules associated with the option. Contact Information: specify the postal and electronic contact information for the author(s) of the option.8. Initial Registrations8.1. Registration: The IDXP Profile Profile identification:http://idxp.org/beep/profile Messages exchanged during channel creation: "IDXP-Greeting" Messages starting one-to-one exchanges: "IDXP-Greeting", "IDMEF- Message" Messages in positive replies: "ok" Messages in negative replies: "error" Messages in one-to-many exchanges: none Message syntax: seeSection 3.3 Message semantics: seeSection 3.4 Contact information: see the "Authors' Addresses" section of this memo8.2. Registration: The System (Well-Known) TCP Port Number for IDXP Protocol Number: 603 Message Formats, Types, Opcodes, and Sequences: seeSection 3.3 Functions: seeSection 3.4Feinstein & Matthews Experimental [Page 19]
RFC 4767 IDXP March 2007 Use of Broadcast/Multicast: none Proposed Name: Intrusion Detection Exchange Protocol Short name: idxp Contact Information: see the "Authors' Addresses" section of this memo8.3. Registration: The channelPriority Option Option Identification: channelPriority Contains: channelPriority (seeSection 9.2) Processing Rules: seeSection 4.1 Contact Information: see the "Authors' Addresses" section of this memo8.4. Registration: The streamType Option Option Identification: streamType Contains: streamType (seeSection 9.3) Processing Rules: seeSection 4.2 Contact Information: see the "Authors' Addresses" section of this memo9. The DTDs9.1. The IDXP DTD The following is the DTD defining the valid elements for the IDXP profile. <!-- DTD for the IDXP Profile Refer to this DTD as: <!ENTITY % IDXP PUBLIC "-//IETF//DTDRFC 4767 IDXP v1.0//EN"> %IDXP; -->Feinstein & Matthews Experimental [Page 20]
RFC 4767 IDXP March 2007 <!-- Includes --> <!ENTITY % BEEP PUBLIC "-//IETF//DTD BEEP//EN"> %BEEP; <!ENTITY % IDMEF-Message PUBLIC "-//IETF//DTDRFC 4765 IDMEF v1.0//EN"> %IDMEF; <!-- Profile Summary BEEP profilehttp://idxp.org/beep/profile role MSG RPY ERR ==== === === === I or L IDXP-Greeting ok error C IDMEF-Message ok error --> <!-- Entity Definitions entity syntax/reference example ====== ================ ======= an authoritative identification URI seeRFC 3986 [6] http://example.com a fully qualified domain name FQDN seeRFC 1034 [9] www.example.com --> <!ENTITY % URI "CDATA"> <!ENTITY % FQDN "CDATA"> <!-- The IDXP-Greeting element declares the role and identity of the peer issuing it, on a per-channel basis. The IDXP-Greeting element may contain one or more Option sub-elements. -->Feinstein & Matthews Experimental [Page 21]
RFC 4767 IDXP March 2007 <!ELEMENT IDXP-Greeting (Option*)> <!ATTLIST IDXP-Greeting uri %URI; #REQUIRED role (client|server) #REQUIRED fqdn %FQDN; #IMPLIED> <!-- The Option element conveys an IDXP channel option. Note that the %LOCS entity is imported from the BEEP Channel Management DTD. --> <!ELEMENT Option (ANY)> <!ATTLIST Option internal NMTOKEN "" external %URI; "" mustUnderstand (true|false) "false" localize %LOCS; "i-default"> <!-- The IDMEF-Message element conveys the intrusion detection information that is exchanged. This element is defined in the idmef-message.dtd --> <!-- End of DTD -->9.2. The channelPriority Option DTD The following is the DTD defining the valid elements for the channelPriority option. <!-- DTD for the channelPriority IDXP option, as of 2002-01-08 Refer to this DTD as: <!ENTITY % IDXP-channelPriority PUBLIC "-//IETF//DTDRFC 4767 IDXP-channelPriority v1.0//EN"> %IDXP-channelPriority; --> <!-- Entity Definitions entity syntax/reference example ====== ================ =======Feinstein & Matthews Experimental [Page 22]
RFC 4767 IDXP March 2007 a priority number PRIORITY 0..2147483647 1 --> <!ENTITY % PRIORITY "CDATA"> <!ELEMENT channelPriority EMPTY> <!ATTLIST channelPriority priority %PRIORITY #REQUIRED> <!-- End of DTD -->9.3. The streamType DTD The following is the DTD defining the valid elements for the streamType option. <!-- DTD for the streamType IDXP option, as of 2002-01-08 Refer to this DTD as: <!ENTITY % IDXP-streamType PUBLIC "-//IETF//DTDRFC 4767 IDXP-streamType v1.0//EN"> %IDXP-streamType; --> <!-- Entity Definitions entity syntax/reference example ====== ================ ======= a stream type STYPE (alert | heartbeat | config) "alert" --> <!ENTITY % STYPE (alert|heartbeat|config)> <!ELEMENT streamType EMPTY> <!ATTLIST streamType type %STYPE #REQUIRED> <!-- End of DTD -->Feinstein & Matthews Experimental [Page 23]
RFC 4767 IDXP March 200710. Reply Codes This section lists the three-digit error codes the IDXP profile may generate. code meaning ==== ======= 421 Service not available (e.g., the peer does not have sufficient resources) 450 Requested action not taken (e.g., DNS lookup failed or connection could not be established. See also 550.) 454 Temporary authentication failure 500 General syntax error (e.g., poorly-formed XML) 501 Syntax error in parameters (e.g., non-valid XML) 504 Parameter not implemented 530 Authentication required 534 Authentication mechanism insufficient (e.g., cipher suite too weak, sequence exhausted) 535 Authentication failure 537 Action not authorized for user 550 Requested action not taken (e.g., peer could be contacted, but malformed greeting or no IDXP profile advertised) 553 Parameter invalid 554 Transaction failed (e.g., policy violation)Feinstein & Matthews Experimental [Page 24]
RFC 4767 IDXP March 200711. Security Considerations The IDXP profile is a profile of BEEP. In BEEP, transport security, user authentication, and data exchange are orthogonal. Refer to Section 9 of [4] for a discussion of this. It is strongly recommended that those wanting to use the IDXP profile initially negotiate a BEEP security profile between the peers that offers the required security properties. The TLS profile SHOULD be used to provide for transport security. SeeSection 5 for a discussion of how IDXP fulfills the IDWG communications protocol requirements. SeeSection 2.4 for a discussion of the trust model.11.1. Use of the TUNNEL Profile SeeSection 5 for IDXP's requirements on application-layer tunneling and the TUNNEL profile specifically. See Section 7 of [3] for a discussion of the security considerations inherent in the use of the TUNNEL profile.11.2. Use of Underlying Security Profiles At present, the TLS profile is the only BEEP security profile known to meet all of the requirements set forth in Section 5 of [5]. When securing a BEEP session with the TLS profile, the TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA cipher suite offers an acceptable level of security. SeeSection 5 for a discussion of how IDXP fulfills the IDWG communications requirements through the use of an underlying security profile.12. IANA Considerations The IANA registered "idxp" as a TCP port number as specified inSection 8.2. The IANA maintains a list of: IDXP options, seeSection 7. For this list, the IESG is responsible for assigning a designated expert to review the specification prior to the IANA making the assignment. As a courtesy to developers of non-standards track IDXP options, the mailing list idxp-discuss@lists.idxp.org may be used to solicit commentary. IANA made the registrations specified in Sections8.3 and8.4.Feinstein & Matthews Experimental [Page 25]
RFC 4767 IDXP March 200713. References13.1. Normative References [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels",BCP 14,RFC 2119, March 1997. [2] Debar, H., Curry, D., and B. Feinstein, "The Intrusion Detection Message Exchange Format (IDMEF)",RFC 4765, March 2007. [3] New, D., "The TUNNEL Profile",RFC 3620, October 2003. [4] Rose, M., "The Blocks Extensible Exchange Protocol Core",RFC3080, March 2001. [5] Wood, M. and M. Erlinger, "Intrusion Detection Message Exchange Requirements",RFC 4766, March 2007.13.2. Informative References [6] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66,RFC 3986, January 2005. [7] Bray, T., Paoli, J., Sperberg-McQueen, C. and E. Maler, "Extensible Markup Language (XML) 1.0 (2nd ed)", W3C REC-xml, October 2000, <http://www.w3.org/TR/REC-xml>. [8] Freed, N. and N. Borenstein, "Multipurpose Internet Mail Extensions (MIME) Part Two: Media Types",RFC 2046, November 1996. [9] Mockapetris, P., "Domain names - concepts and facilities", STD 13,RFC 1034, November 1987.14. Acknowledgements The authors gratefully acknowledge the contributions of Darren New, Marshall T. Rose, Roy Pollock, Tim Buchheim, Mike Erlinger, John C. C. White, and Paul Osterwald.Feinstein & Matthews Experimental [Page 26]
RFC 4767 IDXP March 2007Authors' Addresses Benjamin S. Feinstein SecureWorks, Inc. PO Box 95007 Atlanta, GA 30347 US Phone: +1 404 327-6339 Email: bfeinstein@acm.org URI:http://www.secureworks.com/ Gregory A. Matthews CSC/NASA Ames Research Center EMail: gmatthew@nas.nasa.gov URI:http://www.nas.nasa.gov/Feinstein & Matthews Experimental [Page 27]
RFC 4767 IDXP March 2007Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained inBCP 78, and except as set forth therein, the authors retain all their rights. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.Intellectual Property The IETF takes no position regarding the validity or scope of any Intellectual Property Rights or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; nor does it represent that it has made any independent effort to identify any such rights. Information on the procedures with respect to rights in RFC documents can be found inBCP 78 andBCP 79. Copies of IPR disclosures made to the IETF Secretariat and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementers or users of this specification can be obtained from the IETF on-line IPR repository athttp://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org.Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society.Feinstein & Matthews Experimental [Page 28]
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