309 lines
15 KiB
HTML
309 lines
15 KiB
HTML
<?xml version="1.0" encoding="utf-8" ?>
|
|
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
|
|
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
|
|
<head>
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
|
|
<meta name="generator" content="Docutils 0.11: http://docutils.sourceforge.net/" />
|
|
<title>BitTorrent extension for arbitrary DHT store</title>
|
|
<meta name="author" content="Arvid Norberg, arvid@rasterbar.com" />
|
|
<link rel="stylesheet" type="text/css" href="../../css/base.css" />
|
|
<link rel="stylesheet" type="text/css" href="../../css/rst.css" />
|
|
<script type="text/javascript">
|
|
/* <![CDATA[ */
|
|
(function() {
|
|
var s = document.createElement('script'), t = document.getElementsByTagName('script')[0];
|
|
s.type = 'text/javascript';
|
|
s.async = true;
|
|
s.src = 'http://api.flattr.com/js/0.6/load.js?mode=auto';
|
|
t.parentNode.insertBefore(s, t);
|
|
})();
|
|
/* ]]> */
|
|
</script>
|
|
<link rel="stylesheet" href="style.css" type="text/css" />
|
|
<style type="text/css">
|
|
/* Hides from IE-mac \*/
|
|
* html pre { height: 1%; }
|
|
/* End hide from IE-mac */
|
|
</style>
|
|
</head>
|
|
<body>
|
|
<div class="document" id="bittorrent-extension-for-arbitrary-dht-store">
|
|
<div id="container">
|
|
<div id="headerNav">
|
|
<ul>
|
|
<li class="first"><a href="/">Home</a></li>
|
|
<li><a href="../../products.html">Products</a></li>
|
|
<li><a href="../../contact.html">Contact</a></li>
|
|
</ul>
|
|
</div>
|
|
<div id="header">
|
|
<div id="orange"></div>
|
|
<div id="logo"></div>
|
|
</div>
|
|
<div id="main">
|
|
<h1 class="title">BitTorrent extension for arbitrary DHT store</h1>
|
|
<table class="docinfo" frame="void" rules="none">
|
|
<col class="docinfo-name" />
|
|
<col class="docinfo-content" />
|
|
<tbody valign="top">
|
|
<tr><th class="docinfo-name">Author:</th>
|
|
<td>Arvid Norberg, <a class="last reference external" href="mailto:arvid@rasterbar.com">arvid@rasterbar.com</a></td></tr>
|
|
<tr><th class="docinfo-name">Version:</th>
|
|
<td>1.0.0</td></tr>
|
|
</tbody>
|
|
</table>
|
|
<div class="contents topic" id="table-of-contents">
|
|
<p class="topic-title first">Table of contents</p>
|
|
<ul class="simple">
|
|
<li><a class="reference internal" href="#terminology" id="id3">terminology</a></li>
|
|
<li><a class="reference internal" href="#messages" id="id4">messages</a></li>
|
|
<li><a class="reference internal" href="#immutable-items" id="id5">immutable items</a><ul>
|
|
<li><a class="reference internal" href="#put-message" id="id6">put message</a></li>
|
|
<li><a class="reference internal" href="#get-message" id="id7">get message</a></li>
|
|
</ul>
|
|
</li>
|
|
<li><a class="reference internal" href="#mutable-items" id="id8">mutable items</a><ul>
|
|
<li><a class="reference internal" href="#id1" id="id9">put message</a></li>
|
|
<li><a class="reference internal" href="#id2" id="id10">get message</a></li>
|
|
</ul>
|
|
</li>
|
|
<li><a class="reference internal" href="#signature-verification" id="id11">signature verification</a></li>
|
|
<li><a class="reference internal" href="#expiration" id="id12">expiration</a></li>
|
|
<li><a class="reference internal" href="#test-vectors" id="id13">test vectors</a></li>
|
|
</ul>
|
|
</div>
|
|
<p>This is a proposal for an extension to the BitTorrent DHT to allow
|
|
storing and retrieving of arbitrary data.</p>
|
|
<p>It supports both storing <em>immutable</em> items, where the key is
|
|
the SHA-1 hash of the data itself, and <em>mutable</em> items, where
|
|
the key is the public key of the key pair used to sign the data.</p>
|
|
<p>There are two new proposed messages, <tt class="docutils literal">put</tt> and <tt class="docutils literal">get</tt>.</p>
|
|
<div class="section" id="terminology">
|
|
<h1>terminology</h1>
|
|
<p>In this document, a <em>storage node</em> refers to the node in the DHT to which
|
|
an item is being announced and stored on. A <em>requesting node</em> refers to
|
|
a node which makes look-ups in the DHT to find the storage nodes, to
|
|
request items from them, and possibly re-announce those items to keep them
|
|
alive.</p>
|
|
</div>
|
|
<div class="section" id="messages">
|
|
<h1>messages</h1>
|
|
<p>The proposed new messages <tt class="docutils literal">get</tt> and <tt class="docutils literal">put</tt> are similar to the existing <tt class="docutils literal">get_peers</tt>
|
|
and <tt class="docutils literal">announce_peer</tt>.</p>
|
|
<p>Responses to <tt class="docutils literal">get</tt> should always include <tt class="docutils literal">nodes</tt> and <tt class="docutils literal">nodes6</tt>. Those fields
|
|
have the same semantics as in its <tt class="docutils literal">get_peers</tt> response. It should also include a write token,
|
|
<tt class="docutils literal">token</tt>, with the same semantics as int <tt class="docutils literal">get_peers</tt>. The write token MAY be tied
|
|
specifically to the key which <tt class="docutils literal">get</tt> requested. i.e. the <tt class="docutils literal">token</tt> can only be used
|
|
to store values under that one key.</p>
|
|
<p>The <tt class="docutils literal">id</tt> field in these messages has the same semantics as the standard DHT messages,
|
|
i.e. the node ID of the node sending the message, to maintain the structure of the DHT
|
|
network.</p>
|
|
<p>The <tt class="docutils literal">token</tt> field also has the same semantics as the standard DHT message <tt class="docutils literal">get_peers</tt>
|
|
and <tt class="docutils literal">announce_peer</tt>, when requesting an item and to write an item respectively.</p>
|
|
<p>The <tt class="docutils literal">k</tt> field is the 32 byte ed25519 public key, which the signature
|
|
can be authenticated with. When looking up a mutable item, the <tt class="docutils literal">target</tt> field
|
|
MUST be the SHA-1 hash of this key.</p>
|
|
<p>The distinction between storing mutable and immutable items is the inclusion
|
|
of a public key, a sequence number and signature (<tt class="docutils literal">k</tt>, <tt class="docutils literal">seq</tt> and <tt class="docutils literal">sig</tt>).</p>
|
|
<p><tt class="docutils literal">get</tt> requests for mutable items and immutable items cannot be distinguished from
|
|
eachother. An implementation can either store mutable and immutable items in the same
|
|
hash table internally, or in separate ones and potentially do two lookups for <tt class="docutils literal">get</tt>
|
|
requests.</p>
|
|
<p>The <tt class="docutils literal">v</tt> field is the <em>value</em> to be stored. It is allowed to be any bencoded type (list,
|
|
dict, string or integer). When it's being hashed (for verifying its signature or to calculate
|
|
its key), its flattened, bencoded, form is used. It is important to use the exact
|
|
bencoded representation as it appeared in the message. decoding and then re-encoding
|
|
bencoded structures is not necessarily an identity operation.</p>
|
|
<p>Storing nodes SHOULD reject <tt class="docutils literal">put</tt> requests where the bencoded form of <tt class="docutils literal">v</tt> is longer
|
|
than 1000 bytes.</p>
|
|
</div>
|
|
<div class="section" id="immutable-items">
|
|
<h1>immutable items</h1>
|
|
<p>Immutable items are stored under their SHA-1 hash, and since they cannot be modified,
|
|
there is no need to authenticate the origin of them. This makes immutable items simple.</p>
|
|
<p>A node making a lookup SHOULD verify the data it receives from the network, to verify
|
|
that its hash matches the target that was looked up.</p>
|
|
<div class="section" id="put-message">
|
|
<h2>put message</h2>
|
|
<p>Request:</p>
|
|
<pre class="literal-block">
|
|
{
|
|
"a":
|
|
{
|
|
"id": <em><20 byte id of sending node (string)></em>,
|
|
"v": <em><any bencoded type, whose encoded size <= 1000></em>
|
|
},
|
|
"t": <em><transaction-id (string)></em>,
|
|
"y": "q",
|
|
"q": "put"
|
|
}
|
|
</pre>
|
|
<p>Response:</p>
|
|
<pre class="literal-block">
|
|
{
|
|
"r": { "id": <em><20 byte id of sending node (string)></em> },
|
|
"t": <em><transaction-id (string)></em>,
|
|
"y": "r",
|
|
}
|
|
</pre>
|
|
</div>
|
|
<div class="section" id="get-message">
|
|
<h2>get message</h2>
|
|
<p>Request:</p>
|
|
<pre class="literal-block">
|
|
{
|
|
"a":
|
|
{
|
|
"id": <em><20 byte id of sending node (string)></em>,
|
|
"target": <em><SHA-1 hash of item (string)></em>,
|
|
},
|
|
"t": <em><transaction-id (string)></em>,
|
|
"y": "q",
|
|
"q": "get"
|
|
}
|
|
</pre>
|
|
<p>Response:</p>
|
|
<pre class="literal-block">
|
|
{
|
|
"r":
|
|
{
|
|
"id": <em><20 byte id of sending node (string)></em>,
|
|
"token": <em><write token (string)></em>,
|
|
"v": <em><any bencoded type whose SHA-1 hash matches 'target'></em>,
|
|
"nodes": <em><IPv4 nodes close to 'target'></em>,
|
|
"nodes6": <em><IPv6 nodes close to 'target'></em>
|
|
},
|
|
"t": <em><transaction-id></em>,
|
|
"y": "r",
|
|
}
|
|
</pre>
|
|
</div>
|
|
</div>
|
|
<div class="section" id="mutable-items">
|
|
<h1>mutable items</h1>
|
|
<p>Mutable items can be updated, without changing their DHT keys. To authenticate
|
|
that only the original publisher can update an item, it is signed by a private key
|
|
generated by the original publisher. The target ID mutable items are stored under
|
|
is the SHA-1 hash of the public key (as it appears in the <tt class="docutils literal">put</tt> message).</p>
|
|
<p>In order to avoid a malicious node to overwrite the list head with an old
|
|
version, the sequence number <tt class="docutils literal">seq</tt> must be monotonically increasing for each update,
|
|
and a node hosting the list node MUST not downgrade a list head from a higher sequence
|
|
number to a lower one, only upgrade. The sequence number SHOULD not exceed <tt class="docutils literal">MAX_INT64</tt>,
|
|
(i.e. <tt class="docutils literal">0x7fffffffffffffff</tt>. A client MAY reject any message with a sequence number
|
|
exceeding this.</p>
|
|
<p>The signature is a 64 byte ed25519 signature of the bencoded sequence
|
|
number and <tt class="docutils literal">v</tt> key. e.g. something like this:: <tt class="docutils literal">3:seqi4e1:v12:Hello world!</tt>.</p>
|
|
<div class="section" id="id1">
|
|
<h2>put message</h2>
|
|
<p>Request:</p>
|
|
<pre class="literal-block">
|
|
{
|
|
"a":
|
|
{
|
|
"id": <em><20 byte id of sending node (string)></em>,
|
|
"k": <em><ed25519 public key (32 bytes string)></em>,
|
|
"seq": <em><monotonically increasing sequence number (integer)></em>,
|
|
"sig": <em><ed25519 signature (64 bytes string)></em>,
|
|
"token": <em><write-token (string)></em>,
|
|
"v": <em><any bencoded type, whose encoded size < 1000></em>
|
|
},
|
|
"t": <em><transaction-id (string)></em>,
|
|
"y": "q",
|
|
"q": "put"
|
|
}
|
|
</pre>
|
|
<p>Storing nodes receiving a <tt class="docutils literal">put</tt> request where <tt class="docutils literal">seq</tt> is lower than or equal
|
|
to what's already stored on the node, MUST reject the request. If the sequence
|
|
number is equal, and the value is also the same, the node SHOULD reset its timeout
|
|
counter.</p>
|
|
<p>Note that this request does not contain a target hash. The target hash under
|
|
which this blob is stored is implied by the <tt class="docutils literal">k</tt> argument. The key is
|
|
the SHA-1 hash of the key (<tt class="docutils literal">k</tt>).</p>
|
|
<p>Response:</p>
|
|
<pre class="literal-block">
|
|
{
|
|
"r": { "id": <em><20 byte id of sending node (string)></em> },
|
|
"t": <em><transaction-id (string)></em>,
|
|
"y": "r",
|
|
}
|
|
</pre>
|
|
</div>
|
|
<div class="section" id="id2">
|
|
<h2>get message</h2>
|
|
<p>Request:</p>
|
|
<pre class="literal-block">
|
|
{
|
|
"a":
|
|
{
|
|
"id": <em><20 byte id of sending node (string)></em>,
|
|
"target:" <em><20 byte SHA-1 hash of public key (string)></em>
|
|
},
|
|
"t": <em><transaction-id (string)></em>,
|
|
"y": "q",
|
|
"q": "get"
|
|
}
|
|
</pre>
|
|
<p>Response:</p>
|
|
<pre class="literal-block">
|
|
{
|
|
"r":
|
|
{
|
|
"id": <em><20 byte id of sending node (string)></em>,
|
|
"k": <em><ed25519 public key (32 bytes string)></em>,
|
|
"nodes": <em><IPv4 nodes close to 'target'></em>,
|
|
"nodes6": <em><IPv6 nodes close to 'target'></em>,
|
|
"seq": <em><monotonically increasing sequence number (integer)></em>,
|
|
"sig": <em><ed25519 signature (64 bytes string)></em>,
|
|
"token": <em><write-token (string)></em>,
|
|
"v": <em><any bencoded type, whose encoded size <= 1000></em>
|
|
},
|
|
"t": <em><transaction-id (string)></em>,
|
|
"y": "r",
|
|
}
|
|
</pre>
|
|
</div>
|
|
</div>
|
|
<div class="section" id="signature-verification">
|
|
<h1>signature verification</h1>
|
|
<p>In order to make it maximally difficult to attack the bencoding parser, signing and verification of the
|
|
value and sequence number should be done as follows:</p>
|
|
<ol class="arabic simple">
|
|
<li>encode value and sequence number separately</li>
|
|
<li>concatenate "3:seqi" <tt class="docutils literal">seq</tt> "e1:v" and the encoded value.
|
|
sequence number 1 of value "Hello World!" would be converted to: 3:seqi1e1:v12:Hello World!
|
|
In this way it is not possible to convince a node that part of the length is actually part of the
|
|
sequence number even if the parser contains certain bugs. Furthermore it is not possible to have a
|
|
verification failure if a bencoding serializer alters the order of entries in the dictionary.</li>
|
|
<li>sign or verify the concatenated string</li>
|
|
</ol>
|
|
<p>On the storage node, the signature MUST be verified before accepting the store command. The data
|
|
MUST be stored under the SHA-1 hash of the public key (as it appears in the bencoded dict).</p>
|
|
<p>On the requesting nodes, the key they get back from a <tt class="docutils literal">get</tt> request MUST be verified to hash
|
|
to the target ID the lookup was made for, as well as verifying the signature. If any of these fail,
|
|
the response SHOULD be considered invalid.</p>
|
|
</div>
|
|
<div class="section" id="expiration">
|
|
<h1>expiration</h1>
|
|
<p>Without re-announcement, these items MAY expire in 2 hours. In order
|
|
to keep items alive, they SHOULD be re-announced once an hour.</p>
|
|
<p>Subscriber nodes MAY help out in announcing items the are interested in to the DHT,
|
|
to keep them alive.</p>
|
|
</div>
|
|
<div class="section" id="test-vectors">
|
|
<h1>test vectors</h1>
|
|
</div>
|
|
</div>
|
|
<div id="footer">
|
|
<span>Copyright © 2005-2013 Rasterbar Software.</span>
|
|
</div>
|
|
</div>
|
|
<script src="http://www.google-analytics.com/urchin.js" type="text/javascript">
|
|
</script>
|
|
<script type="text/javascript">
|
|
_uacct = "UA-1599045-1";
|
|
urchinTracker();
|
|
</script>
|
|
</div>
|
|
</body>
|
|
</html>
|