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Internet Engineering Task Force (IETF)                       B. TrammellRequest for Comments: 6546                                    ETH ZurichObsoletes:6046                                               April 2012Category: Standards TrackISSN: 2070-1721Transport of Real-time Inter-network Defense (RID) Messagesover HTTP/TLSAbstract   The Incident Object Description Exchange Format (IODEF) defines a   common XML format for document exchange, and Real-time Inter-network   Defense (RID) defines extensions to IODEF intended for the   cooperative handling of security incidents within consortia of   network operators and enterprises.  This document specifies an   application-layer protocol for RID based upon the passing of RID   messages over HTTP/TLS.Status of This Memo   This is an Internet Standards Track document.   This document is a product of the Internet Engineering Task Force   (IETF).  It represents the consensus of the IETF community.  It has   received public review and has been approved for publication by the   Internet Engineering Steering Group (IESG).  Further information on   Internet Standards is available inSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc6546.Copyright Notice   Copyright (c) 2012 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (http://trustee.ietf.org/license-info) in effect on the date of   publication of this document.  Please review these documents   carefully, as they describe your rights and restrictions with respect   to this document.  Code Components extracted from this document must   include Simplified BSD License text as described in Section 4.e of   the Trust Legal Provisions and are provided without warranty as   described in the Simplified BSD License.Trammell                     Standards Track                    [Page 1]

RFC 6546                      RID Transport                   April 20121.  Introduction   The Incident Object Description Exchange Format (IODEF) [RFC5070]   describes an XML document format for the purpose of exchanging data   between Computer Security Incident Response Teams (CSIRTs) or those   responsible for security incident handling for service providers   (SPs).  The defined document format provides a simple way for CSIRTs   to exchange data in a way which can be easily parsed.   IODEF defines a message format, not a protocol, as the sharing of   messages is assumed to be out of scope in order to allow CSIRTs to   exchange and store messages in a way most suited to their established   incident-handling processes.  However, Real-time Inter-network   Defense (RID) [RFC6545] does require a specification of a protocol to   ensure interoperability among members in a RID consortium.  This   document specifies the transport of RID messages within HTTP   [RFC2616] Request and Response messages over TLS [RFC5246] (herein,   HTTP/TLS).  Note that any IODEF message may also be transported using   this mechanism, by sending it as a RID Report message.1.1.  Changes fromRFC 6046   This document contains the following changes with respect to its   predecessor [RFC6046]:   o  The status of the document is Standards Track.   o  The document is updated to refer to the updated RID specification,      [RFC6545], where appropriate.   o  Language regarding the use of HTTP/1.1 and TCP ports for RID      transport is clarified.   o  The RID-Callback-Token entity header field is added to allow      matching of RID replies during callback, independent of the      content of the underlying RID message.   o  The minimum required version of TLS is upgraded to 1.1, and the      minimum recommended version to 1.2.   o  Language regarding PKI for RID over HTTPS is clarified, and      updated to refer to [RFC6125].   This document obsoletes [RFC6046] and moves it to Historic status.Trammell                     Standards Track                    [Page 2]

RFC 6546                      RID Transport                   April 20122.  Terminology and Normative Sections   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this   document are to be interpreted as described in [RFC2119].   RID systems participating in a consortium are required to fully   implement the protocol inSection 3 in order to interoperate within   the consortium; the remainder of this document is informative and   provides helpful background or explanatory information.3.  Transmission of RID Messages over HTTP/TLS   This section specifies the details of the transport of RID messages   [RFC6545] over HTTP/TLS.  In this arrangement, each RID server is   both an HTTP/TLS server and an HTTP/TLS client.  When a RID message   is sent, the sending RID system connects to the receiving RID system   and sends the message, optionally receiving a message in reply.  Each   RID system MUST be prepared to accept HTTP/TLS connections from any   RID peer with which it communicates, in order to support callback for   delayed replies (see below).BCP 56 [RFC3205] contains a number of important considerations when   using HTTP for application protocols.  These include the size of the   payload for the application, whether the application will use a web   browser, whether the protocol should be defined on a port other than   80, and if the security provided through HTTP/TLS suits the needs of   the new application.   It is acknowledged within the scope of these concerns that HTTP/TLS   is not ideally suited for RID transport, as the former is a client-   server protocol and the latter a message-exchange protocol; however,   the ease of implementation of RID systems over HTTP/TLS outweighs   these concerns.  Consistent withBCP 56, RID systems listen for TCP   connections on port 4590 (seeSection 5).  Every RID system   participating in a consortium SHOULD listen for HTTP/TLS connections   on the assigned port.  RID systems MAY be configurable to listen on   ports other than the well-known port; this configuration is out of   scope for this specification.  RID systems SHOULD NOT use TCP port   443 (the standard port for HTTP over TLS) for RID messages in order   to avoid confusing standard HTTP/TLS servers for RID systems.   RID systems MUST implement all REQUIRED functionality for HTTP/1.1   [RFC2616].  All RID messages sent in HTTP Requests MUST be sent using   the POST method with a Request-URI of '/'.  As RID documents are XML,   the RID media type is 'text/xml'; i.e., the 'Content-type' Request   and Response headers MUST be 'text/xml'.  As RID messages MUST be   sent using the POST method, the GET and HEAD methods have noTrammell                     Standards Track                    [Page 3]

RFC 6546                      RID Transport                   April 2012   particular meaning on a RID system; a RID system SHOULD answer   'GET /' or 'HEAD /' with 204 No Content.  Other Request-URIs are   reserved for future use; any access to Request-URIs other than '/' by   any method on a RID system SHOULD return the appropriate HTTP error   (404 Not Found).   Since the content of RID messages is essentially declarative, a RID   system interrupted during transport MAY simply repeat the   transaction; the sending of a RID message is idempotent.   As the queries and replies in a RID message exchange may be   significantly separated in time, RID over HTTP/TLS supports a   callback mechanism.  In this mechanism, the receiving RID system MAY   return a 202 Accepted response, called a RID callback, instead of a   RID message.  The RID callback MUST contain a zero-length entity body   and a 'RID-Callback-Token' entity header field, itself containing a   unique token generated by the receiving RID system.   The RID-Callback-Token is an opaque, whitespace-free string of up to   255 printable ASCII characters that MUST uniquely identify the   callback among all callbacks from the receiving RID system to the   sending RID system.  Due to the amount of time that may be required   to generate a RID Result or Report response, there is no upper bound   on the time period for this uniqueness requirement.  The RID-   Callback-Token in ABNF [RFC5234] form is shown below:   callback-token = 1*255(VCHAR)   When performing RID callback, a responding system MUST connect to the   host at the network-layer address from which the original request was   sent; there is no mechanism in RID for redirected callback.  This   callback SHOULD use TCP port 4590 unless configured to use a   different port.   While a RID system SHOULD return the reply in an HTTP Response if it   is available immediately or within a generally accepted HTTP client   timeout (about thirty seconds), this is not mandatory, and as such   RID systems MUST be prepared for a query to be met with a 202   Accepted, an empty Response body, a connection termination, and a   callback.  Note that all RID messages require a response from the   receiving RID system, so a sending RID system can expect either an   immediate response or a callback.   Table 1 lists the allowable RID message types in an HTTP Response for   a given RID message type in the Request.  A RID system MUST be   prepared to handle an HTTP Response of the given type(s) when sendingTrammell                     Standards Track                    [Page 4]

RFC 6546                      RID Transport                   April 2012   the corresponding HTTP Request.  A RID system MUST NOT send an HTTP   Response containing any RID message other than the one corresponding   to the one sent in the HTTP Request.     +----------------------+----------+--------+-------------------+     | Request RID type     | Callback | Result | Response RID type |     +----------------------+----------+--------+-------------------+     | InvestigationRequest |          | 200    | Acknowledgement   |     | InvestigationRequest |          | 200    | Result            |     | InvestigationRequest |          | 200    | Report            |     | InvestigationRequest |          | 202    | [empty]           |     | TraceRequest         |          | 200    | Acknowledgement   |     | TraceRequest         |          | 200    | Result            |     | TraceRequest         |          | 200    | Report            |     | TraceRequest         |          | 202    | [empty]           |     | Query                |          | 200    | Acknowledgement   |     | Query                |          | 200    | Report            |     | Query                |          | 202    | [empty]           |     | Acknowledgement      |     X    | 200    | [empty]           |     | Result               |     X    | 200    | [empty]           |     | Report               |          | 200    | Acknowledgement   |     | Report               |          | 200    | [empty]           |     | Report               |     X    | 200    | [empty]           |     +----------------------+----------+--------+-------------------+                                  Table 1   The use of stable DNS names to address RID systems is RECOMMENDED; in   addition to facilitating connection to RID systems within a   consortium, these are to be used as reference identifiers for a RID   system's peers.  For security purposes, RID systems SHOULD NOT return   3xx Redirection response codes, and SHOULD NOT follow any 3xx   Redirection.  The protocol provides no in-band method for handling a   change of address of a RID system.   If a RID system receives an improper RID message in an HTTP Request,   it MUST return an appropriate 4xx Client Error result code to the   requesting RID system.  If a RID system cannot process a RID message   received in an HTTP Request due to an error on its own side, it MUST   return an appropriate 5xx Server Error result code to the requesting   RID system.   Note that HTTP provides no mechanism for signaling to a server that a   response body is not a valid RID message.  If a RID system receives   an improper RID message in an HTTP Response, or cannot process a RID   message received in an HTTP Response due to an error on its own side,Trammell                     Standards Track                    [Page 5]

RFC 6546                      RID Transport                   April 2012   it MUST log the error and present it to the RID system administrator   for handling; the error logging format is an implementation detail   and is considered out of scope for this specification.   RID systems MUST support and SHOULD use HTTP/1.1 persistent   connections as described in [RFC2616].  RID systems MUST support   chunked transfer encoding on the HTTP server side to allow the   implementation of clients that do not need to pre-calculate message   sizes before constructing HTTP headers.   RID systems MUST use TLS version 1.1 [RFC4346] or higher for   confidentiality, identification, and authentication, when sending RID   messages over HTTPS.  HTTPS is specified inSection 2 of [RFC2818].   RID systems MUST use mutual authentication; that is, both RID systems   acting as HTTPS clients and RID systems acting as HTTPS servers MUST   be identified by an X.509 certificate [RFC5280].  Mutual   authentication requires full path validation on each certificate, as   defined in [RFC5280].   The TLS session MUST use non-NULL ciphersuites for authentication,   integrity, and confidentiality.  Sessions MAY be renegotiated within   these constraints.   All RID systems SHOULD be identified by a certificate containing   DNS-ID identifier as inSection 6.4 of [RFC6125]; the inclusion of   Common Names (CN-IDs) in certificates identifying RID systems is NOT   RECOMMENDED.  RID systems MUST verify the reference identifiers of   their peers against those stored in the certificates presented using   one of the methods in the following paragraph.  Wildcards MUST NOT   appear in the DNS-ID or CN-ID of a certificate identifying a RID   system.   RID systems MUST support the verification of certificates against an   explicit whitelist of peer certificates.  RID systems SHOULD support   the verification of reference identifiers by matching the DNS-ID or   CN-ID with a reverse DNS lookup of the connecting RID peer; this   support SHOULD allow the lookup to be cached and/or done in advance   in order to ensure verifiability during instability or compromise of   DNS itself.   Additional general information on the use of PKI with RID systems is   detailed inSection 9.3 of [RFC6545].   RID systems MUST support TLS version 1.1 and SHOULD support TLS   version 1.2 [RFC5246]; RID systems MUST NOT request, offer, or use   any version of SSL, or any version of TLS prior to 1.1, due to known   security vulnerabilities in prior versions of the protocol; seeAppendix E of [RFC5246] for more information.Trammell                     Standards Track                    [Page 6]

RFC 6546                      RID Transport                   April 20124.  Security Considerations   In addition to the final paragraphs inSection 3 on the use of TLS to   secure RID message transport, all security considerations of related   documents apply, especially the Incident Object Description Exchange   Format (IODEF) [RFC5070] and Real-time Inter-network Defense (RID)   [RFC6545].  The protocol described herein is built on the foundation   of those documents; the security considerations contained therein are   incorporated by reference.5.  IANA Considerations   Consistent withBCP 56 [RFC3205], since RID over HTTP/TLS is a   substantially new service, and should be controlled at the consortium   member network's border differently than HTTP/TLS, it requires a new   port number.  IANA has assigned port 4590/tcp to RID with service   name "RID over HTTP/TLS".6.  Acknowledgements   The author would like to thank David Black for the review, and   Kathleen Moriarty for work on earlier revisions of this   specification.  This work was partially supported by the European   Union Seventh Framework Program under grant agreement 257315   (DEMONS).7.  References7.1.  Normative References   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate              Requirement Levels",BCP 14,RFC 2119, March 1997.   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext              Transfer Protocol -- HTTP/1.1",RFC 2616, June 1999.   [RFC2818]  Rescorla, E., "HTTP Over TLS",RFC 2818, May 2000.   [RFC5070]  Danyliw, R., Meijer, J., and Y. Demchenko, "The Incident              Object Description Exchange Format",RFC 5070,              December 2007.   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security              (TLS) Protocol Version 1.2",RFC 5246, August 2008.Trammell                     Standards Track                    [Page 7]

RFC 6546                      RID Transport                   April 2012   [RFC5280]  Cooper, D., Santesson, S., Farrell, S., Boeyen, S.,              Housley, R., and W. Polk, "Internet X.509 Public Key              Infrastructure Certificate and Certificate Revocation List              (CRL) Profile",RFC 5280, May 2008.   [RFC6125]  Saint-Andre, P. and J. Hodges, "Representation and              Verification of Domain-Based Application Service Identity              within Internet Public Key Infrastructure Using X.509              (PKIX) Certificates in the Context of Transport Layer              Security (TLS)",RFC 6125, March 2011.   [RFC6545]  Moriarty, K., "Real-time Inter-network Defense (RID)",RFC 6545, April 2012.7.2.  Informative References   [RFC3205]  Moore, K., "On the use of HTTP as a Substrate",BCP 56,RFC 3205, February 2002.   [RFC4346]  Dierks, T. and E. Rescorla, "The Transport Layer Security              (TLS) Protocol Version 1.1",RFC 4346, April 2006.   [RFC5234]  Crocker, D. and P. Overell, "Augmented BNF for Syntax              Specifications: ABNF", STD 68,RFC 5234, January 2008.   [RFC6046]  Moriarty, K. and B. Trammell, "Transport of Real-time              Inter-network Defense (RID) Messages",RFC 6046,              November 2010.Author's Address   Brian Trammell   Swiss Federal Institute of Technology Zurich   Gloriastrasse 35   8092 Zurich   Switzerland   Phone: +41 44 632 70 13   EMail: trammell@tik.ee.ethz.chTrammell                     Standards Track                    [Page 8]