/usr/share/doc/ikiwiki-hosting-common/design/username.html is in ikiwiki-hosting-common 0.20170622ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 | <!DOCTYPE html>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>username</title>
<meta name="viewport" content="width=device-width, initial-scale=1" />
<link rel="stylesheet" href="../style.css" type="text/css" />
<link rel="stylesheet" href="../local.css" type="text/css" />
</head>
<body>
<div class="page">
<div class="pageheader">
<div class="header">
<span>
<span class="parentlinks">
<a href="../index.html">ikiwiki hosting internals</a>/
<a href="../design.html">design</a>/
</span>
<span class="title">
username
</span>
</span>
</div>
</div>
<div id="pagebody">
<div id="content" role="main">
<p>Site subdomains are mapped to unique unix usernames.</p>
<p>Subdomain limits:</p>
<ul>
<li>253 characters total (including top level domain)</li>
<li>a-zA-Z0-9-</li>
</ul>
<p>Unix username limits:</p>
<ul>
<li>32 characters limit (some things support longer, but not everything)</li>
<li>recommended to match: [a-z<em>][a-z0-9</em>-]*</li>
<li>may be user-visible (ie, for ssh)</li>
</ul>
<h2>format for short subdomains</h2>
<p>This format will be used most of the time, and it makes it easy to see
what hostname a process is running for, etc.</p>
<p>First 2 chars: Avoid conflict with system usernames, and briefly indicate
top-level domain name. "b-"</p>
<p>Remaining 30 chars: subdomain, if it is short enough</p>
<h2>format with hash for longer subdomains</h2>
<p>Any hash has potential for collisions. The chances of such a collision
occuring in relatively short, limited DNS subdomains are quite rare, and in
the unlikely case of one happening, the system should just print an error
and the user can pick a different subdomain. This means that the system has
to explicitly check for a hash collision at site creation time.</p>
<p>I think it follows that we do not have to choose a hash that is
crytographically strong.</p>
<p>md5_base64, with + replaced by _, and / by -</p>
<ul>
<li>22 characters</li>
<li>could spell a rude word, if unlucky</li>
<li>other 10 characters could be "b5-" + <7 characters of subdomain>
to avoid any overlap with other usernames, encode the hash type,
and make the subdomain semi-discoverable</li>
<li>small potential for collisions</li>
</ul>
<p>md5_hex</p>
<ul>
<li>32 characters</li>
<li>no rude words</li>
<li>small potential for overlap with (32 character only!) system usernames</li>
<li>small potential for collisions</li>
</ul>
<p>sha1_base64, with + replaced by _, and / by -</p>
<ul>
<li>27 characters</li>
<li>could spell a rude word, if unlucky</li>
<li>other 5 characters could be "bsh1-" to avoid any overlap
with other usernames, and encode the hash type
(or "b1-" + <2 characters of subdomain>, but 2 chars is not
a worthwhile amount)</li>
<li>small(er?) potential for collisions</li>
</ul>
<p>half of md5_hex</p>
<ul>
<li>16 characters</li>
<li>no rude words</li>
<li>other 16 characters can be "b5-" + <12 characters of subdomain> + "-"
to avoid any overlap with other usernames, encode the hash type,
and make the subdomain semi-discoverable</li>
<li>larger potential for collisions, as we have a 64 bit hash</li>
<li><strong>what is currently used</strong></li>
</ul>
</div>
</div>
<div id="footer" class="pagefooter" role="contentinfo">
<div id="pageinfo">
<div id="backlinks">
Links:
<a href="../design.html">design</a>
</div>
<div class="pagedate">
Last edited <span class="date">Thu Jun 22 09:08:31 2017</span>
<!-- Created <span class="date">Thu Jun 22 09:08:31 2017</span> -->
</div>
</div>
<!-- from ikiwiki hosting internals -->
</div>
</div>
</body>
</html>
|