MILE Working Group B. Trammell
Internet-Draft ETH Zurich
Obsoletes: 6046 (if approved) January 3, 2012
Intended status: Standards Track
Expires: July 04, 2012

Transport of Real-time Inter-network Defense (RID) Messages over HTTP/TLS


The Incident Object Description Exchange Format (IODEF) defines a common XML format for document exchange, and Realtime Internetwork Defense (RID) defines extensions to IODEF intended for the cooperative handling of security incidents within consortia of network operators and enterprises. This document specifies a transport protocol for RID based upon the passing of RID messages over HTTP/TLS.

Status of This Memo

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This Internet-Draft will expire on July 04, 2012.

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1. 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 an easy way for CSIRTs to exchange data in a way which can be easily parsed.

IODEF defines a message format, not a transport 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) [I-D.ietf-mile-rfc6045-bis] do require a specification of a transport 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 transported 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 from RFC6046

This document contains the following changes with respect to its predecessor [RFC6046]:

This document, when published, obsoletes [RFC6046] and moves it to Historic status.

2. 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 in Section 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 [I-D.ietf-mile-rfc6045-bis] 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. All RID systems 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 with BCP 56, RID systems listen for TCP connections on port 4590 (see Section 5). Every RID system participating in a consortium MUST listen for HTTP/TLS connections on the assigned port. RID systems SHOULD NOT use TCP port 443 (the standard port for HTTP over TLS) for RID messages, 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 no 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, itself containing a unique token generated by the receiving RID system. This token is a string 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. When performing RID callback, a responding system MUST connect to TCP port 4590 on the network-layer address from which the original request was sent; there is no mechanism in RID for redirected callback.

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 sending 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
TraceRequest 200 RequestAuthorization
TraceRequest 200 Result
TraceRequest 202 [empty]
RequestAuthorization X 202 [empty]
Result X 202 [empty]
Investigation 200 Result
Investigation 202 [empty]
Report X 202 [empty]
IncidentQuery 200 Report
IncidentQuery 202 [empty]

For security purposes, RID systems SHOULD NOT return 3xx Redirection response codes, and MUST NOT follow any 3xx Redirection. The protocol provides no in-band method for handling a change of address of a RID System. For this reason, the use of stable DNS names to address RID Systems is RECOMMENDED.

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 an 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, 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 with mutual authentication for transport confidentiality, identification, and authentication, as in [RFC2818]. 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; see Appendix E of [RFC5246] for more.

The TLS session MUST use non-NULL ciphersuites for authentication, integrity, and confidentiality. Sessions MAY be renegotiated within these constraints.

Each RID consortium SHOULD use a trusted public key infrastructure (PKI) to manage identities for RID systems participating in TLS connections. At minimum, each RID system MUST trust a set of X.509 Issuer identities ("Certificate Authorities") [RFC5280] to directly authenticate RID system peers with which it is willing to exchange information, and/or a specific white list of X.509 Subject identities of RID system peers.

RID systems MUST provide for the verification of the identity of a RID system peer presenting a valid and trusted certificate, by verifying the fully-qualified domain name and service name from the DNS SRV record, if available, against that stored in the certificate, as in Section 6 of [RFC6125].

4. Security Considerations

In addition to the final paragraphs in Section 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) [I-D.ietf-mile-rfc6045-bis]. The transport described herein is built on the foundation of these documents; the security considerations contained therein are incorporated by reference.

5. IANA Considerations

Consistent with BCP 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.

[NOTE to IANA: Since this document obsoletes RFC 6046, please update the reference in the Port Numbers registry for 4590/tcp to point to this document.]

6. Acknowledgments

The author would like to thank David Black for the review, and Kathleen Moriarty for work on earlier revisions of this specification.

7. References

7.1. 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.
[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.
[I-D.ietf-mile-rfc6045-bis] Moriarty, K, "Real-time Inter-network Defense (RID)", Internet-Draft draft-ietf-mile-rfc6045-bis-09, January 2012.
[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.

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.
[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:

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