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  • Committer: Teddy Hogeborn
  • Date: 2015-07-01 20:01:26 UTC
  • mto: (237.7.307 trunk)
  • mto: This revision was merged to the branch mainline in revision 325.
  • Revision ID: teddy@recompile.se-20150701200126-qb3f6c3jcas2f4og
mandos-client: Try to start a plugin to add and remove a local route.

* debian/mandos-client.README.Debian: Add setting of environment
                                      variable MANDOSPLUGINHELPERDIR
                                      to command line testing
                                      mandos-client.
* mandos-client.c (raise_privileges): Moved to top of file.
                  (raise_privileges_permanently): - '' -
                  (lower_privileges): - '' -
                  (lower_privileges_permanently): - '' -
  (add_remove_local_route, add_local_route, remove_local_route): New.
  (start_mandos_communication): Set SOCK_CLOEXEC flag on socket.  Run
                                the above functions to add (and
                                remove) local route, if the conditions
                                indicates it could help.
  (run_network_hooks): Use O_DIRECTORY, O_PATH, and O_CLOEXEC flags
                       when opening network hook directory. Do
                       TEMP_FAILURE_RETRY around opening of /dev/null
                       and network hook executables.  Move redirecting
                       of stdout and stderr to as late as possible
                       before fexecve().
  (main): Use O_DIRECTORY and O_PATH when opening temporary directory.
* plugins.d/mandos-client.xml (ENVIRONMENT): Document usage of the
                                             MANDOSPLUGINHELPERDIR
                                             environment variable.

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plugins.d/mandos-client.xml
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<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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        "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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<!ENTITY COMMANDNAME "mandos-client">
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<!ENTITY TIMESTAMP "2009-01-04">
 
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<!ENTITY TIMESTAMP "2015-06-29">
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<!ENTITY % common SYSTEM "../common.ent">
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%common;
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]>
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        <firstname>Björn</firstname>
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        <surname>Påhlsson</surname>
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        <address>
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          <email>belorn@fukt.bsnet.se</email>
 
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          <email>belorn@recompile.se</email>
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        </address>
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      </author>
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      <author>
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        <firstname>Teddy</firstname>
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        <surname>Hogeborn</surname>
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        <address>
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          <email>teddy@fukt.bsnet.se</email>
 
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          <email>teddy@recompile.se</email>
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        </address>
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      </author>
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    </authorgroup>
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    <copyright>
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      <year>2008</year>
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      <year>2009</year>
 
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      <year>2012</year>
 
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      <year>2013</year>
 
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      <year>2014</year>
 
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      <year>2015</year>
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      <holder>Teddy Hogeborn</holder>
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      <holder>Björn Påhlsson</holder>
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    </copyright>
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        ><replaceable>PORT</replaceable></option></arg>
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      </group>
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      <sbr/>
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      <group>
 
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      <group rep='repeat'>
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        <arg choice="plain"><option>--interface
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        <replaceable>NAME</replaceable></option></arg>
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        <arg choice="plain"><option>-i
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        <replaceable>NAME</replaceable></option></arg>
 
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        <replaceable>NAME</replaceable><arg rep='repeat'
 
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        >,<replaceable>NAME</replaceable></arg></option></arg>
 
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        <arg choice="plain"><option>-i <replaceable>NAME</replaceable
 
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        ><arg rep='repeat'>,<replaceable>NAME</replaceable></arg
 
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        ></option></arg>
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      </group>
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      <sbr/>
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      <group>
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      </arg>
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      <sbr/>
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      <arg>
 
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        <option>--delay <replaceable>SECONDS</replaceable></option>
 
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      </arg>
 
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      <sbr/>
 
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      <arg>
 
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        <option>--retry <replaceable>SECONDS</replaceable></option>
 
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      </arg>
 
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      <sbr/>
 
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      <arg>
 
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        <option>--network-hook-dir
 
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        <replaceable>DIR</replaceable></option>
 
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      </arg>
 
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      <sbr/>
 
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      <arg>
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        <option>--debug</option>
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      </arg>
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    </cmdsynopsis>
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      <command>&COMMANDNAME;</command> is a client program that
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      communicates with <citerefentry><refentrytitle
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      >mandos</refentrytitle><manvolnum>8</manvolnum></citerefentry>
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      to get a password.  It uses IPv6 link-local addresses to get
126
 
      network connectivity, Zeroconf to find servers, and TLS with an
127
 
      OpenPGP key to ensure authenticity and confidentiality.  It
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      keeps running, trying all servers on the network, until it
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      receives a satisfactory reply or a TERM signal is received.
 
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      to get a password.  In slightly more detail, this client program
 
145
      brings up network interfaces, uses the interfaces’ IPv6
 
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      link-local addresses to get network connectivity, uses Zeroconf
 
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      to find servers on the local network, and communicates with
 
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      servers using TLS with an OpenPGP key to ensure authenticity and
 
149
      confidentiality.  This client program keeps running, trying all
 
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      servers on the network, until it receives a satisfactory reply
 
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      or a TERM signal.  After all servers have been tried, all
 
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      servers are periodically retried.  If no servers are found it
 
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      will wait indefinitely for new servers to appear.
 
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    </para>
 
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    <para>
 
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      The network interfaces are selected like this: If any interfaces
 
157
      are specified using the <option>--interface</option> option,
 
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      those interface are used.  Otherwise,
 
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      <command>&COMMANDNAME;</command> will use all interfaces that
 
160
      are not loopback interfaces, are not point-to-point interfaces,
 
161
      are capable of broadcasting and do not have the NOARP flag (see
 
162
      <citerefentry><refentrytitle>netdevice</refentrytitle>
 
163
      <manvolnum>7</manvolnum></citerefentry>).  (If the
 
164
      <option>--connect</option> option is used, point-to-point
 
165
      interfaces and non-broadcast interfaces are accepted.)  If any
 
166
      used interfaces are not up and running, they are first taken up
 
167
      (and later taken down again on program exit).
 
168
    </para>
 
169
    <para>
 
170
      Before network interfaces are selected, all <quote>network
 
171
      hooks</quote> are run; see <xref linkend="network-hooks"/>.
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    </para>
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    <para>
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      This program is not meant to be run directly; it is really meant
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            assumed to separate the address from the port number.
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          </para>
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          <para>
182
 
            This option is normally only useful for testing and
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            debugging.
 
224
            Normally, Zeroconf would be used to locate Mandos servers,
 
225
            in which case this option would only be used when testing
 
226
            and debugging.
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          </para>
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        </listitem>
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      </varlistentry>
187
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      <varlistentry>
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        <term><option>--interface=
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        <replaceable>NAME</replaceable></option></term>
 
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        <term><option>--interface=<replaceable
 
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        >NAME</replaceable><arg rep='repeat'>,<replaceable
 
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        >NAME</replaceable></arg></option></term>
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        <term><option>-i
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        <replaceable>NAME</replaceable></option></term>
 
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        <replaceable>NAME</replaceable><arg rep='repeat'>,<replaceable
 
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        >NAME</replaceable></arg></option></term>
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        <listitem>
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          <para>
195
 
            Network interface that will be brought up and scanned for
196
 
            Mandos servers to connect to.  The default it
197
 
            <quote><literal>eth0</literal></quote>.
198
 
          </para>
199
 
          <para>
200
 
            If the <option>--connect</option> option is used, this
201
 
            specifies the interface to use to connect to the address
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            given.
 
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            Comma separated list of network interfaces that will be
 
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            brought up and scanned for Mandos servers to connect to.
 
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            The default is the empty string, which will automatically
 
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            use all appropriate interfaces.
 
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          </para>
 
245
          <para>
 
246
            If the <option>--connect</option> option is used, and
 
247
            exactly one interface name is specified (except
 
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            <quote><literal>none</literal></quote>), this specifies
 
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            the interface to use to connect to the address given.
 
250
          </para>
 
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          <para>
 
252
            Note that since this program will normally run in the
 
253
            initial RAM disk environment, the interface must be an
 
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            interface which exists at that stage.  Thus, the interface
 
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            can normally not be a pseudo-interface such as
 
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            <quote>br0</quote> or <quote>tun0</quote>; such interfaces
 
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            will not exist until much later in the boot process, and
 
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            can not be used by this program, unless created by a
 
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            <quote>network hook</quote> — see <xref
 
260
            linkend="network-hooks"/>.
 
261
          </para>
 
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          <para>
 
263
            <replaceable>NAME</replaceable> can be the string
 
264
            <quote><literal>none</literal></quote>; this will make
 
265
            <command>&COMMANDNAME;</command> only bring up interfaces
 
266
            specified <emphasis>before</emphasis> this string.  This
 
267
            is not recommended, and only meant for advanced users.
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          </para>
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        </listitem>
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      </varlistentry>
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          </para>
252
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        </listitem>
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      </varlistentry>
 
319
 
 
320
      <varlistentry>
 
321
        <term><option>--delay=<replaceable
 
322
        >SECONDS</replaceable></option></term>
 
323
        <listitem>
 
324
          <para>
 
325
            After bringing a network interface up, the program waits
 
326
            for the interface to arrive in a <quote>running</quote>
 
327
            state before proceeding.  During this time, the kernel log
 
328
            level will be lowered to reduce clutter on the system
 
329
            console, alleviating any other plugins which might be
 
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            using the system console.  This option sets the upper
 
331
            limit of seconds to wait.  The default is 2.5 seconds.
 
332
          </para>
 
333
        </listitem>
 
334
      </varlistentry>
 
335
 
 
336
      <varlistentry>
 
337
        <term><option>--retry=<replaceable
 
338
        >SECONDS</replaceable></option></term>
 
339
        <listitem>
 
340
          <para>
 
341
            All Mandos servers are tried repeatedly until a password
 
342
            is received.  This value specifies, in seconds, how long
 
343
            between each successive try <emphasis>for the same
 
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            server</emphasis>.  The default is 10 seconds.
 
345
          </para>
 
346
        </listitem>
 
347
      </varlistentry>
 
348
 
 
349
      <varlistentry>
 
350
        <term><option>--network-hook-dir=<replaceable
 
351
        >DIR</replaceable></option></term>
 
352
        <listitem>
 
353
          <para>
 
354
            Network hook directory.  The default directory is
 
355
            <quote><filename class="directory"
 
356
            >/lib/mandos/network-hooks.d</filename></quote>.
 
357
          </para>
 
358
        </listitem>
 
359
      </varlistentry>
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      <varlistentry>
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        <term><option>--debug</option></term>
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      <refentrytitle>plugin-runner</refentrytitle>
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      <manvolnum>8mandos</manvolnum></citerefentry>) is used to run
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      both this program and others in in parallel,
320
 
      <emphasis>one</emphasis> of which will prompt for passwords on
321
 
      the system console.
 
426
      <emphasis>one</emphasis> of which (<citerefentry>
 
427
      <refentrytitle>password-prompt</refentrytitle>
 
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      <manvolnum>8mandos</manvolnum></citerefentry>) will prompt for
 
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      passwords on the system console.
322
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    </para>
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  </refsect1>
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      server could be found and the password received from it could be
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      successfully decrypted and output on standard output.  The
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      program will exit with a non-zero exit status only if a critical
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      error occurs.  Otherwise, it will forever connect to new
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      <application>Mandos</application> servers as they appear, trying
334
 
      to get a decryptable password and print it.
 
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      error occurs.  Otherwise, it will forever connect to any
 
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      discovered <application>Mandos</application> servers, trying to
 
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      get a decryptable password and print it.
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    </para>
336
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  </refsect1>
337
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338
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  <refsect1 id="environment">
339
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    <title>ENVIRONMENT</title>
 
448
    <variablelist>
 
449
      <varlistentry>
 
450
        <term><envar>MANDOSPLUGINHELPERDIR</envar></term>
 
451
        <listitem>
 
452
          <para>
 
453
            This environment variable will be assumed to contain the
 
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            directory containing any helper executables.  The use and
 
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            nature of these helper executables, if any, is
 
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            purposefully not documented.
 
457
        </para>
 
458
        </listitem>
 
459
      </varlistentry>
 
460
    </variablelist>
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    <para>
341
 
      This program does not use any environment variables, not even
342
 
      the ones provided by <citerefentry><refentrytitle
 
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      This program does not use any other environment variables, not
 
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      even the ones provided by <citerefentry><refentrytitle
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      >cryptsetup</refentrytitle><manvolnum>8</manvolnum>
344
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    </citerefentry>.
345
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    </para>
346
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  </refsect1>
347
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469
  <refsect1 id="network-hooks">
 
470
    <title>NETWORK HOOKS</title>
 
471
    <para>
 
472
      If a network interface like a bridge or tunnel is required to
 
473
      find a Mandos server, this requires the interface to be up and
 
474
      running before <command>&COMMANDNAME;</command> starts looking
 
475
      for Mandos servers.  This can be accomplished by creating a
 
476
      <quote>network hook</quote> program, and placing it in a special
 
477
      directory.
 
478
    </para>
 
479
    <para>
 
480
      Before the network is used (and again before program exit), any
 
481
      runnable programs found in the network hook directory are run
 
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      with the argument <quote><literal>start</literal></quote> or
 
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      <quote><literal>stop</literal></quote>.  This should bring up or
 
484
      down, respectively, any network interface which
 
485
      <command>&COMMANDNAME;</command> should use.
 
486
    </para>
 
487
    <refsect2 id="hook-requirements">
 
488
      <title>REQUIREMENTS</title>
 
489
      <para>
 
490
        A network hook must be an executable file, and its name must
 
491
        consist entirely of upper and lower case letters, digits,
 
492
        underscores, periods, and hyphens.
 
493
      </para>
 
494
      <para>
 
495
        A network hook will receive one argument, which can be one of
 
496
        the following:
 
497
      </para>
 
498
      <variablelist>
 
499
        <varlistentry>
 
500
          <term><literal>start</literal></term>
 
501
          <listitem>
 
502
            <para>
 
503
              This should make the network hook create (if necessary)
 
504
              and bring up a network interface.
 
505
            </para>
 
506
          </listitem>
 
507
        </varlistentry>
 
508
        <varlistentry>
 
509
          <term><literal>stop</literal></term>
 
510
          <listitem>
 
511
            <para>
 
512
              This should make the network hook take down a network
 
513
              interface, and delete it if it did not exist previously.
 
514
            </para>
 
515
          </listitem>
 
516
        </varlistentry>
 
517
        <varlistentry>
 
518
          <term><literal>files</literal></term>
 
519
          <listitem>
 
520
            <para>
 
521
              This should make the network hook print, <emphasis>one
 
522
              file per line</emphasis>, all the files needed for it to
 
523
              run.  (These files will be copied into the initial RAM
 
524
              filesystem.)  Typical use is for a network hook which is
 
525
              a shell script to print its needed binaries.
 
526
            </para>
 
527
            <para>
 
528
              It is not necessary to print any non-executable files
 
529
              already in the network hook directory, these will be
 
530
              copied implicitly if they otherwise satisfy the name
 
531
              requirements.
 
532
            </para>
 
533
          </listitem>
 
534
        </varlistentry>
 
535
        <varlistentry>
 
536
          <term><literal>modules</literal></term>
 
537
          <listitem>
 
538
            <para>
 
539
              This should make the network hook print, <emphasis>on
 
540
              separate lines</emphasis>, all the kernel modules needed
 
541
              for it to run.  (These modules will be copied into the
 
542
              initial RAM filesystem.)  For instance, a tunnel
 
543
              interface needs the
 
544
              <quote><literal>tun</literal></quote> module.
 
545
            </para>
 
546
          </listitem>
 
547
        </varlistentry>
 
548
      </variablelist>
 
549
      <para>
 
550
        The network hook will be provided with a number of environment
 
551
        variables:
 
552
      </para>
 
553
      <variablelist>
 
554
        <varlistentry>
 
555
          <term><envar>MANDOSNETHOOKDIR</envar></term>
 
556
          <listitem>
 
557
            <para>
 
558
              The network hook directory, specified to
 
559
              <command>&COMMANDNAME;</command> by the
 
560
              <option>--network-hook-dir</option> option.  Note: this
 
561
              should <emphasis>always</emphasis> be used by the
 
562
              network hook to refer to itself or any files in the hook
 
563
              directory it may require.
 
564
            </para>
 
565
          </listitem>
 
566
        </varlistentry>
 
567
        <varlistentry>
 
568
          <term><envar>DEVICE</envar></term>
 
569
          <listitem>
 
570
            <para>
 
571
              The network interfaces, as specified to
 
572
              <command>&COMMANDNAME;</command> by the
 
573
              <option>--interface</option> option, combined to one
 
574
              string and separated by commas.  If this is set, and
 
575
              does not contain the interface a hook will bring up,
 
576
              there is no reason for a hook to continue.
 
577
            </para>
 
578
          </listitem>
 
579
        </varlistentry>
 
580
        <varlistentry>
 
581
          <term><envar>MODE</envar></term>
 
582
          <listitem>
 
583
            <para>
 
584
              This will be the same as the first argument;
 
585
              i.e. <quote><literal>start</literal></quote>,
 
586
              <quote><literal>stop</literal></quote>,
 
587
              <quote><literal>files</literal></quote>, or
 
588
              <quote><literal>modules</literal></quote>.
 
589
            </para>
 
590
          </listitem>
 
591
        </varlistentry>
 
592
        <varlistentry>
 
593
          <term><envar>VERBOSITY</envar></term>
 
594
          <listitem>
 
595
            <para>
 
596
              This will be the <quote><literal>1</literal></quote> if
 
597
              the <option>--debug</option> option is passed to
 
598
              <command>&COMMANDNAME;</command>, otherwise
 
599
              <quote><literal>0</literal></quote>.
 
600
            </para>
 
601
          </listitem>
 
602
        </varlistentry>
 
603
        <varlistentry>
 
604
          <term><envar>DELAY</envar></term>
 
605
          <listitem>
 
606
            <para>
 
607
              This will be the same as the <option>--delay</option>
 
608
              option passed to <command>&COMMANDNAME;</command>.  Is
 
609
              only set if <envar>MODE</envar> is
 
610
              <quote><literal>start</literal></quote> or
 
611
              <quote><literal>stop</literal></quote>.
 
612
            </para>
 
613
          </listitem>
 
614
        </varlistentry>
 
615
        <varlistentry>
 
616
          <term><envar>CONNECT</envar></term>
 
617
          <listitem>
 
618
            <para>
 
619
              This will be the same as the <option>--connect</option>
 
620
              option passed to <command>&COMMANDNAME;</command>.  Is
 
621
              only set if <option>--connect</option> is passed and
 
622
              <envar>MODE</envar> is
 
623
              <quote><literal>start</literal></quote> or
 
624
              <quote><literal>stop</literal></quote>.
 
625
            </para>
 
626
          </listitem>
 
627
        </varlistentry>
 
628
      </variablelist>
 
629
      <para>
 
630
        A hook may not read from standard input, and should be
 
631
        restrictive in printing to standard output or standard error
 
632
        unless <varname>VERBOSITY</varname> is
 
633
        <quote><literal>1</literal></quote>.
 
634
      </para>
 
635
    </refsect2>
 
636
  </refsect1>
 
637
  
348
638
  <refsect1 id="files">
349
639
    <title>FILES</title>
350
640
    <variablelist>
362
652
          </para>
363
653
        </listitem>
364
654
      </varlistentry>
 
655
      <varlistentry>
 
656
        <term><filename
 
657
        class="directory">/lib/mandos/network-hooks.d</filename></term>
 
658
        <listitem>
 
659
          <para>
 
660
            Directory where network hooks are located.  Change this
 
661
            with the <option>--network-hook-dir</option> option.  See
 
662
            <xref linkend="network-hooks"/>.
 
663
          </para>
 
664
        </listitem>
 
665
      </varlistentry>
365
666
    </variablelist>
366
667
  </refsect1>
367
668
  
381
682
    </para>
382
683
    <informalexample>
383
684
      <para>
384
 
        Normal invocation needs no options, if the network interface
385
 
        is <quote>eth0</quote>:
 
685
        Normal invocation needs no options, if the network interfaces
 
686
        can be automatically determined:
386
687
      </para>
387
688
      <para>
388
689
        <userinput>&COMMANDNAME;</userinput>
390
691
    </informalexample>
391
692
    <informalexample>
392
693
      <para>
393
 
        Search for Mandos servers (and connect to them) using another
394
 
        interface:
 
694
        Search for Mandos servers (and connect to them) using one
 
695
        specific interface:
395
696
      </para>
396
697
      <para>
397
698
        <!-- do not wrap this line -->
412
713
    <informalexample>
413
714
      <para>
414
715
        Run in debug mode, with a custom key, and do not use Zeroconf
415
 
        to locate a server; connect directly to the IPv6 address
416
 
        <quote><systemitem class="ipaddress"
417
 
        >2001:db8:f983:bd0b:30de:ae4a:71f2:f672</systemitem></quote>,
418
 
        port 4711, using interface eth2:
 
716
        to locate a server; connect directly to the IPv6 link-local
 
717
        address <quote><systemitem class="ipaddress"
 
718
        >fe80::aede:48ff:fe71:f6f2</systemitem></quote>, port 4711,
 
719
        using interface eth2:
419
720
      </para>
420
721
      <para>
421
722
 
422
723
<!-- do not wrap this line -->
423
 
<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt --connect 2001:db8:f983:bd0b:30de:ae4a:71f2:f672:4711 --interface eth2</userinput>
 
724
<userinput>&COMMANDNAME; --debug --pubkey keydir/pubkey.txt --seckey keydir/seckey.txt --connect fe80::aede:48ff:fe71:f6f2:4711 --interface eth2</userinput>
424
725
 
425
726
      </para>
426
727
    </informalexample>
461
762
    <para>
462
763
      It will also help if the checker program on the server is
463
764
      configured to request something from the client which can not be
464
 
      spoofed by someone else on the network, unlike unencrypted
465
 
      <acronym>ICMP</acronym> echo (<quote>ping</quote>) replies.
 
765
      spoofed by someone else on the network, like SSH server key
 
766
      fingerprints, and unlike unencrypted <acronym>ICMP</acronym>
 
767
      echo (<quote>ping</quote>) replies.
466
768
    </para>
467
769
    <para>
468
770
      <emphasis>Note</emphasis>: This makes it completely insecure to
476
778
  <refsect1 id="see_also">
477
779
    <title>SEE ALSO</title>
478
780
    <para>
 
781
      <citerefentry><refentrytitle>intro</refentrytitle>
 
782
      <manvolnum>8mandos</manvolnum></citerefentry>,
479
783
      <citerefentry><refentrytitle>cryptsetup</refentrytitle>
480
784
      <manvolnum>8</manvolnum></citerefentry>,
481
785
      <citerefentry><refentrytitle>crypttab</refentrytitle>
559
863
              <para>
560
864
                This client uses IPv6 link-local addresses, which are
561
865
                immediately usable since a link-local addresses is
562
 
                automatically assigned to a network interfaces when it
 
866
                automatically assigned to a network interface when it
563
867
                is brought up.
564
868
              </para>
565
869
            </listitem>