Transport of Real-time Inter-network Defense (RID) Messages over HTTP/TLS
draft-ietf-mile-rfc6046-bis-08.txt

Abstract

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 application-layer protocol for RID based upon the passing of RID messages over HTTP/TLS.

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http:/⁠/⁠datatracker.ietf.org/⁠drafts/⁠current/⁠.

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This Internet-Draft will expire on July 24, 2012.

Copyright Notice

Copyright (c) 2012 IETF Trust and the persons identified as the document authors. All rights reserved.

This document is subject to BCP 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.

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 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 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 from RFC6046

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

• The intended status of the document is now Standards Track.
• The document is updated to refer to the updated RID specification, [I-D.ietf-mile-rfc6045-bis], where appropriate.
• Language regarding the use of HTTP/1.1 and TCP ports for RID transport is clarified.
• 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.
• The minimum required version of TLS is upgraded to 1.1, and the minimum recommend version to 1.2.

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 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, 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 field, itself containing an 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 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.