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| author | Laurent Bercot <ska-skaware@skarnet.org> | 2014-12-15 23:08:59 +0000 |
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| committer | Laurent Bercot <ska-skaware@skarnet.org> | 2014-12-15 23:08:59 +0000 |
| commit | e0fc82203d677a6f1e808e9a1a46176c109d89be (patch) | |
| tree | e9609209b755e3f7a8480aea86601ffe9d4ca540 /doc/s6-ipcserver-access.html | |
| download | s6-networking-e0fc82203d677a6f1e808e9a1a46176c109d89be.tar.xz | |
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diff --git a/doc/s6-ipcserver-access.html b/doc/s6-ipcserver-access.html new file mode 100644 index 0000000..817425b --- /dev/null +++ b/doc/s6-ipcserver-access.html @@ -0,0 +1,172 @@ +<html> + <head> + <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> + <meta http-equiv="Content-Language" content="en" /> + <title>s6-networking: the s6-ipcserver-access program</title> + <meta name="Description" content="s6-networking: the s6-ipcserver-access program" /> + <meta name="Keywords" content="s6-networking s6-tcpserver-access unix access control ipcrules" /> + <!-- <link rel="stylesheet" type="text/css" href="http://skarnet.org/default.css" /> --> + </head> +<body> + +<p> +<a href="index.html">s6-networking</a><br /> +<a href="http://skarnet.org/software/">Software</a><br /> +<a href="http://skarnet.org/">skarnet.org</a> +</p> + +<h1> The <tt>s6-ipcserver-access</tt> program </h1> + +<p> +<tt>s6-ipcserver-access</tt> is a command-line access +control tool for Unix domain sockets on systems where the +<a href="http://www.superscript.com/ucspi-ipc/getpeereid.html">getpeereid()</a> system call can be implemented. +It is meant to be run after +<a href="s6-ipcserver.html">s6-ipcserver</a> and before +the application program on the s6-ipcserver command line. +</p> + +<h2> Interface </h2> + +<pre> + s6-ipcserver-access [ -v <em>verbosity</em> ] [ -E | -e ] [ -l <em>localname</em> ] [ -i <em>rulesdir</em> | -x <em>rulesfile</em> ] <em>prog...</em> +</pre> + +<ul> + <li> s6-ipcserver-access checks it is run under a UCSPI server tool +such as <a href="s6-ipcserver.html">s6-ipcserver</a>. + <li> It checks that the remote end of the connection fits the +accepted criteria defined by the database contained in <em>rulesdir</em> +or <em>rulesfile</em>. If the database tells it to reject the connection, +the program exits 1. </li> + <li> It sets up a few additional environment variables. </li> + <li> It executes into <em>prog...</em>, +unless the first matching rule in the rule database +includes instructions to override <em>prog...</em>. </li> +</ul> + +<h2> Environment variables </h2> + +<p> +s6-ipcserver-access expects to inherit some environment variables from +its parent: +</p> + +<ul> + <li> PROTO: normally IPC, but could be anything else, like UNIX. </li> + <li> ${PROTO}REMOTEEUID: the effective UID of the client program connecting to the socket. </li> + <li> ${PROTO}REMOTEEGID: the effective GID of the client program connecting to the socket. </li> +</ul> + +<p> + Additionally, it exports the following variables before executing into +<em>prog...</em>: +</p> + +<ul> + <li> ${PROTO}LOCALPATH: set to the local "address" of the socket, as +reported by the +<a href="http://pubs.opengroup.org/onlinepubs/9699919799/functions/getsockname.html">getsockname()</a> +system call, truncated to 99 characters max. </li> +</ul> + +<p> + Also, the access rules database can instruct s6-ipcserver-access to set +up, or unset, more environment variables, depending on the client address. +</p> + +<h2> Options </h2> + +<ul> + <li> <tt>-v <em>verbosity</em></tt> : be more or less verbose, i.e. +print more or less information to stderr: + <ul> + <li> 0: only log error messages. </li> + <li> 1: only log error and warning messages, and accepted connections. +This is the default. </li> + <li> 2: also log rejected connections and more warning messages. </li> + </ul> </li> + <li> <tt>-E</tt> : no environment. All environment variables potentially +set by s6-ipcserver-access, as well as those set by +<a href="s6-ipcserver.html">s6-ipcserver</a>, will be unset instead. </li> + <li> <tt>-e</tt> : set up environment variables normally. +This is the default. </li> + <li> <tt>-l <em>localname</em></tt> : use <em>localname</em> +as the value for the ${PROTO}LOCALPATH environment variable, instead of +looking it up via getsockname(). </li> + <li> <tt>-i <em>rulesdir</em></tt> : check client credentials +against a filesystem-based database in the <em>rulesdir</em> directory. </li> + <li> <tt>-x <em>rulesfile</em></tt> : check client credentials +against a <a href="http://en.wikipedia.org/wiki/Cdb_(software)">cdb</a> +database in the <em>rulesfile</em> file. <tt>-i</tt> and <tt>-x</tt> are +mutually exclusive. If none of those options is given, no credential checking will be +performed, and a warning will be emitted on every connection if +<em>verbosity</em> is 2 or more. </li> +</ul> + +<h2> Access rule checking </h2> + +<p> + s6-ipcserver-access checks its client connection against +a ruleset. This ruleset can be implemented: +</p> + +<ul> + <li> either in the filesystem as an arborescence of directories and files, +if the <tt>-i</tt> option has been given. This option is the most flexible +one: the directory format is simple enough for scripts to understand and +modify it, and the ruleset can be changed dynamically. This is practical, +for instance, for roaming users. </li> +<li> or in a <a href="http://en.wikipedia.org/wiki/Cdb_(software)">CDB +file</a>, if the <tt>-x</tt> option has been given. This option is the most +efficient one if the ruleset is static enough: a lot less system calls are +needed to perform searches in a CDB than in the filesystem. </li> +</ul> + +<p> + The exact format of the ruleset is described on the +<a href="s6-accessrules-cdb-from-fs.html">s6-accessrules-cdb-from-fs</a> page. +</p> + +<p> +s6-ipcserver-access first reads the client UID <em>uid</em> and +GID <em>gid</em> from the +${PROTO}REMOTEEUID and ${PROTO}REMOTEEGID environment variables, and checks +them with the +<a href="libs6net/accessrules.html#uidgid">s6net_accessrules_keycheck_uidgid()</a> +function. In other words, it tries to match: + +<ul> + <li> <tt>uid/</tt><em>uid</em> </li> + <li> <tt>gid/</tt><em>gid</em> </li> + <li> <tt>uid/default</tt> </li> +</ul> + +<p> + in that order. If no S6NET_ACCESSRULES_ALLOW result can be obtained, +the connection is denied. +</p> + +<h2> Environment and executable modifications </h2> + +<p> + s6-ipcserver-access interprets non-empty <tt>env</tt> subdirectories +and <tt>exec</tt> files +it finds in the first matching rule of the ruleset, as explained +in the <a href="s6-accessrules-cdb-from-fs.html">s6-accessrules-cdb-from-fs</a> +page. +</p> + +<ul> + <li> An <tt>env</tt> subdirectory is interpreted as if the +<a href="http://skarnet.org/software/s6/s6-envdir.html">s6-envdir</a> +command had been called before executing <em>prog</em>: the environment +is modified according to the contents of <tt>env</tt>. </li> + <li> An <tt>exec</tt> file containing <em>newprog</em> completely +bypasses the rest of s6-ipcserver-access' command line. After +environment modifications, if any, s6-ipcserver-access execs into +<tt><a href="http://skarnet.org/software/execline/execlineb.html">execlineb</a> -c <em>newprog</em></tt>. </li> +</ul> + +</body> +</html> |