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<title>TLS Mapping for Scalability Protocols</title>
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<body class="article">
<div id="header">
<h1>TLS Mapping for Scalability Protocols</h1>
<div class="details">
<span id="author" class="author">Garrett D'Amore</span><br>
<span id="email" class="email"><a href="mailto:garrett@damore.org">garrett@damore.org</a></span><br>
<span id="revnumber">version 1.3.1,</span>
<span id="revdate">2017-11-28</span>
</div>
</div>
<div id="content">
<div id="preamble">
<div class="sectionbody">
<div class="paragraph">
<p><span class="image"><img src="https://img.shields.io/badge/status-draft-yellow.svg?style=for-the-badge" alt="draft"></span></p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_tls_mapping_for_scalability_protocols">TLS Mapping for Scalability Protocols</h2>
<div class="sectionbody">
<div class="ulist">
<ul>
<li>
<p>Status: draft</p>
</li>
<li>
<p>Authors: <a href="mailto:garrett@damore.org">Garrett D&#8217;Amore</a></p>
</li>
<li>
<p>Version 1.3.1</p>
</li>
</ul>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_abstract">Abstract</h2>
<div class="sectionbody">
<div class="paragraph">
<p>This document defines the <a href="https://tools.ietf.org/html/rfc5246">TLS v1.2</a>
mapping for scalability protocols, where TLS is running on top of
<a href="https://tools.ietf.org/html/rfc793">TCP</a>.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_license">License</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Copyright 2017 <a href="mailto:garrett@damore.org">Garrett D&#8217;Amore</a><br>
Copyright 2017 <a href="mailto:info@capitar.com">Capitar IT Group BV</a><br>
Copyright 2017 <a href="mailto:info@staysail.tech">Staysail Systems, Inc.</a></p>
</div>
<div class="paragraph">
<p>This specification is licensed under the Apache License, Version 2.0
(the "License"); you may not use this file except in compliance with the
License.
You may obtain a copy of the license
<a href="http://www.apache.org/licenses/LICENSE-2.0">online</a>.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_language">Language</h2>
<div class="sectionbody">
<div class="paragraph">
<p>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 <a href="https://tools.ietf.org/html/rfc2119">RFC 2119</a>.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_underlying_protocol">Underlying protocol</h2>
<div class="sectionbody">
<div class="paragraph">
<p>This mapping should be layered directly on the top of TLS v1.2
secured connections. While it is possible to use TLS on top of other
transports, this document specifically concerns itself with TLS
running on top of TCP.</p>
</div>
<div class="paragraph">
<p>Other combinations may be contemplated, and should follow the same
details as discussed here.</p>
</div>
<div class="paragraph">
<p>As when running SP over TCP directly, the TCP port number is
determined by the application or user.</p>
</div>
<div class="paragraph">
<p>Implementations <strong>MUST NOT</strong> support versions of TLS or SSL older than
v1.2. Implementations <strong>MAY</strong> support newer versions, and <strong>SHOULD</strong>
avoid using algorithms or features removed from newer versions.</p>
</div>
<div class="admonitionblock note">
<table>
<tr>
<td class="icon">
<i class="fa icon-note" title="Note"></i>
</td>
<td class="content">
It is our intent that when TLS v1.3 is finalized, to support, and
possibly even mandate, the use of TLS v1.3.
</td>
</tr>
</table>
</div>
<div class="paragraph">
<p>Implementations <strong>MUST NOT</strong> use RC4, DES, MD5, SHA1, or any
algorithm in CBC (cipher-block-chaining) mode.
This prohibition applies to both use in cipher suites and in certificates.</p>
</div>
<div class="paragraph">
<p>Implementations <strong>MUST NOT</strong> use RSA, DSA, or DH public key algorithms
with key lengths smaller than 1024 bits, and <strong>SHOULD</strong> use 2048-bit key
lengths or larger.</p>
</div>
<div class="paragraph">
<p>Implementations <strong>MUST NOT</strong> use renegotiation. An attempt to renegotiate
<strong>MUST</strong> cause the connection to be closed immediately.</p>
</div>
<div class="paragraph">
<p>Implementations <strong>MUST NOT</strong> use session resumption, but <strong>MUST</strong> instead
open a new TCP port when creating a new session, and <strong>MUST</strong> close the
underlying TCP when completing a session (after processing any
CLOSE-NOTIFY messages. (It is assumed that implementations will
generally use long-lived connections, and elimination of session resumption
leads to simpler, and therefore more secure, implementation.)</p>
</div>
<div class="paragraph">
<p>Implementations <strong>MUST NOT</strong> use TLS layer compression, as it has been
found to weak TLS. (Compression <strong>MAY</strong> be done by the application
in the layer above, if it is needed.)</p>
</div>
<div class="paragraph">
<p>Certificate and key management are out of scope for this document.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_connection_initiation">Connection Initiation</h2>
<div class="sectionbody">
<div class="paragraph">
<p>The first phase of connections involves setting up the TLS connection.
The details of this are not specific to this protocol. Implementations
<strong>MUST</strong> validate remote peers using standard TLS verification methods.
The specific validation checks, such as certificate enforcement and
time/date checks <strong>SHOULD</strong> be administrator configurable.</p>
</div>
<div class="paragraph">
<p>If a secure TLS connection cannot be established, then the underlying
connection <strong>MUST</strong> be closed immediately. (Each peer may apply it&#8217;s own
checks in determining whether the connection is secure or not.)</p>
</div>
<div class="paragraph">
<p>As soon as the TLS connection is established, both peers <strong>MUST</strong> send a
protocol header immediately. The protocol header has the following form,
in big-endian:</p>
</div>
<div class="imageblock">
<div class="content">
<img src="tls1-header.png" alt="tls1 header" width="896" height="200">
</div>
</div>
<div class="paragraph">
<p>The <code>version</code> field <strong>MUST</strong> be zero.</p>
</div>
<div class="paragraph">
<p>The first three bytes are used to identify that the connection is
being used for scalability protocols (note that in ASCII this will look
like "\0SP"), using this version of the standard (0x0).</p>
</div>
<div class="paragraph">
<p>The 16-bit <code>type</code> field corresponds to the numeric scalability
protocol ID of the sender. For example, a <em>PAIRv1</em> sender would use the
numeric value 0x11 here, corresponding to the <em>PAIR</em> protocol version 1.</p>
</div>
<div class="paragraph">
<p>The final 16-bit <code>reserved</code> field <strong>MUST</strong> be set to zero.</p>
</div>
<div class="paragraph">
<p>After each peer sends this initial handshake message, they <strong>MUST</strong>
wait until the other peers handshake message is received.</p>
</div>
<div class="paragraph">
<p>Each peer <strong>MUST</strong> validate that the remote peer is using the same
values for the first 32-bits, and that the <code>type</code> fields are compatible.
Additionally the <code>reserved</code> field <strong>MUST</strong> be zero.</p>
</div>
<div class="paragraph">
<p>If any of these validation checks, the peer <strong>MUST</strong> close the connection.
No error indication is sent to the other peer.</p>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_message_format">Message Format</h2>
<div class="sectionbody">
<div class="paragraph">
<p>Each SP message sent over this mapping is prefixed by a
64-bit<sup class="footnote">[<a id="_footnoteref_1" class="footnote" href="#_footnote_1" title="View footnote.">1</a>]</sup>
(big-endian) length, followed by the payload:</p>
</div>
<div class="imageblock">
<div class="content">
<img src="tls1-message.png" alt="tls1 message" width="896" height="320">
</div>
</div>
<div class="paragraph">
<p>The <code>payload size</code> represents the size of the <code>payload</code> field, in octets.</p>
</div>
<div class="paragraph">
<p>The <code>payload</code> field may be absent, in which case the <code>payload size</code> field
will be zero. (This would indicate an empty message.)</p>
</div>
<div class="paragraph">
<p>Sending the size in advance allows the receiver to preallocate a buffer
large enough to hold the entire incoming message. It also offers the
receiver a chance to reject messages larger than it is willing to accept,
which can be useful for avoiding certain forms of denial-of-service
attacks.</p>
</div>
<div class="paragraph">
<p>Implementations <strong>MUST</strong> support a configurable maximum limit on the
received message size. It is <strong>RECOMMENDED</strong> the default value for
this be one megabyte. Implementations <strong>MUST</strong> also support disabling
this check.</p>
</div>
<div class="paragraph">
<p>If an implementation choosed to reject a received message as too large,
it <strong>MUST</strong> immediately close the connection.</p>
</div>
<div class="sect2">
<h3 id="_no_multiplexing">No Multiplexing</h3>
<div class="paragraph">
<p>While some modern protocols multiplex multiple communications channels
over a single TCP or TLS stream, we have chosen not to do this. Typically
this is done to mitigate against the high cost of the 3-way TCP handshake
used when setting up a connection. Such approaches benefit primarily
applications with very short-lived TCP connections.</p>
</div>
<div class="paragraph">
<p>In contrast, we expect most SP applications to use longer lived
connections.</p>
</div>
<div class="quoteblock">
<blockquote>
<div class="paragraph">
<p>Don&#8217;t cross the streams.</p>
</div>
</blockquote>
<div class="attribution">
&#8212; Egon Spengler<br>
<cite>Ghostbusters</cite>
</div>
</div>
<div class="paragraph">
<p>Protocols which multiplex multiple channels are subject to head-of-line
blocking, where one slow channel can have a detrimental impact on others.
Additionally, they add a great deal more complexity, and usually require
extra data copying.</p>
</div>
</div>
</div>
</div>
<div class="sect1">
<h2 id="_uri_format">URI Format</h2>
<div class="sectionbody">
<div class="paragraph">
<p>The URI scheme used to represent TLS addresses is similar
that used for TCP.</p>
</div>
<div class="paragraph">
<p>The format <strong>SHALL</strong> be <code>tls+tcp://<em>host</em>:<em>port</em></code>, where the <em>host</em>
represents either an Internet host name, or an IP address, and the <em>port</em>
represents the TCP port number used.</p>
</div>
<div class="paragraph">
<p>When specifying an IPv6 address for the <em>host</em>, the address <strong>SHALL</strong> be
enclosed in square backets (<code>[</code> and <code>]</code>) to avoid confusion with the final colon
separating the IP address and the <em>port</em>. For example, to specify the IPv6
loopback address, and port 4300, the URI would be <code>tls+tcp://[::1]:4300</code>.</p>
</div>
<div class="paragraph">
<p>A responder <strong>MAY</strong> elide the <em>host</em> portion, to just bind to itself,
in which case the format will be <code>tls+tcp://:<em>port</em></code>.</p>
</div>
<div class="paragraph">
<p>Implementations <strong>MAY</strong> offer the ability to specify a wild card of <code>*</code>
when listening to indicate that the server should listen on all locally
configured IP addresses.</p>
</div>
<div class="paragraph">
<p>Implementations <strong>MAY</strong> allow a <em>port</em> number of 0 to be specified when
listening, in which case a randomly chosen ephemeral TCP port <strong>SHALL</strong> be
used.<sup class="footnote">[<a id="_footnoteref_2" class="footnote" href="#_footnote_2" title="View footnote.">2</a>]</sup></p>
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<div class="sect1">
<h2 id="_security_considerations">Security Considerations</h2>
<div class="sectionbody">
<div class="paragraph">
<p>The correct configuration and administration of TLS is required to
provide a channel secure from eavesdropping, modification, and replay
attacks. The discussion of how to do this, and the important details
around key and certificate administration, are implementation specific
and out of scope for this document.</p>
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<div class="paragraph">
<p>Denial-of-service considerations are discussed, in particular the
use of a limit on the incoming message sizes.</p>
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<div id="footnotes">
<hr>
<div class="footnote" id="_footnote_1">
<a href="#_footnoteref_1">1</a>. In practice no message will ever be so large as needing 64-bits to represent the length, but in our experience a simple fixed width field of this size will support any conceivable future message sizes, and is more efficient and easier to use than a variable length field. The overhead of sending several extra bytes per message is negligible for most practical protocols, and unlikely to even be measurable.
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<div class="footnote" id="_footnote_2">
<a href="#_footnoteref_2">2</a>. In this case the implementation will need to offer a method for applications to determine the ephemeral TCP port number chosen.
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Version 1.3.1<br>
Last updated 2017-11-28 16:50:44 UTC
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