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  • Committer: Teddy Hogeborn
  • Date: 2015-05-23 20:18:34 UTC
  • mto: This revision was merged to the branch mainline in revision 756.
  • Revision ID: teddy@recompile.se-20150523201834-e89ex4ito93yni8x
mandos: Use multiprocessing module to run checkers.

For a long time, the Mandos server has occasionally logged the message
"ERROR: Child process vanished".  This was never a fatal error, but it
has been annoying and slightly worrying, since a definite cause was
not found.  One potential cause could be the "multiprocessing" and
"subprocess" modules conflicting w.r.t. SIGCHLD.  To avoid this,
change the running of checkers from using subprocess.Popen
asynchronously to instead first create a multiprocessing.Process()
(which is asynchronous) calling a function, and have that function
then call subprocess.call() (which is synchronous).  In this way, the
only thing using any asynchronous subprocesses is the multiprocessing
module.

This makes it necessary to change one small thing in the D-Bus API,
since the subprocesses.call() function does not expose the raw wait(2)
status value.

DBUS-API (CheckerCompleted): Change the second value provided by this
                             D-Bus signal from the raw wait(2) status
                             to the actual terminating signal number.
mandos (subprocess_call_pipe): New function to be called by
                               multiprocessing.Process (starting a
                               separate process).
(Client.last_checker signal): New attribute for signal which
                              terminated last checker.  Like
                              last_checker_status, only not accessible
                              via D-Bus.
(Client.checker_callback): Take new "connection" argument and use it
                           to get returncode; set last_checker_signal.
                           Return False so gobject does not call this
                           callback again.
(Client.start_checker): Start checker using a multiprocessing.Process
                        instead of a subprocess.Popen.
(ClientDBus.checker_callback): Take new "connection" argument.        Call
                               Client.checker_callback early to have
                               it set last_checker_status and
                               last_checker_signal; use those.  Change
                               second value provided to D-Bus signal
                               CheckerCompleted to use
                               last_checker_signal if checker was
                               terminated by signal.
mandos-monitor: Update to reflect DBus API change.
(MandosClientWidget.checker_completed): Take "signal" instead of
                                        "condition" argument.  Use it
                                        accordingly.  Remove dead code
                                        (os.WCOREDUMP case).

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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">
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<!ENTITY TIMESTAMP "2010-09-25">
 
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<!ENTITY TIMESTAMP "2015-01-25">
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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>2010</year>
 
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      <year>2011</year>
 
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      <year>2012</year>
 
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      <year>2013</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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      <sbr/>
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      <arg><option>--debug</option></arg>
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      <sbr/>
 
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      <arg><option>--debuglevel
 
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      <replaceable>LEVEL</replaceable></option></arg>
 
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      <sbr/>
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      <arg><option>--no-dbus</option></arg>
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      <sbr/>
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      <arg><option>--no-ipv6</option></arg>
 
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      <sbr/>
 
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      <arg><option>--no-restore</option></arg>
 
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      <sbr/>
 
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      <arg><option>--statedir
 
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      <replaceable>DIRECTORY</replaceable></option></arg>
 
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      <sbr/>
 
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      <arg><option>--socket
 
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      <replaceable>FD</replaceable></option></arg>
 
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      <sbr/>
 
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      <arg><option>--foreground</option></arg>
 
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      <sbr/>
 
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      <arg><option>--no-zeroconf</option></arg>
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    </cmdsynopsis>
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    <cmdsynopsis>
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      <command>&COMMANDNAME;</command>
112
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    <para>
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      <command>&COMMANDNAME;</command> is a server daemon which
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      handles incoming request for passwords for a pre-defined list of
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      client host computers.  The Mandos server uses Zeroconf to
116
 
      announce itself on the local network, and uses TLS to
117
 
      communicate securely with and to authenticate the clients.  The
118
 
      Mandos server uses IPv6 to allow Mandos clients to use IPv6
119
 
      link-local addresses, since the clients will probably not have
120
 
      any other addresses configured (see <xref linkend="overview"/>).
121
 
      Any authenticated client is then given the stored pre-encrypted
122
 
      password for that specific client.
 
134
      client host computers. For an introduction, see
 
135
      <citerefentry><refentrytitle>intro</refentrytitle>
 
136
      <manvolnum>8mandos</manvolnum></citerefentry>. The Mandos server
 
137
      uses Zeroconf to announce itself on the local network, and uses
 
138
      TLS to communicate securely with and to authenticate the
 
139
      clients.  The Mandos server uses IPv6 to allow Mandos clients to
 
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      use IPv6 link-local addresses, since the clients will probably
 
141
      not have any other addresses configured (see <xref
 
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      linkend="overview"/>).  Any authenticated client is then given
 
143
      the stored pre-encrypted password for that specific client.
123
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    </para>
124
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  </refsect1>
125
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      </varlistentry>
195
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      <varlistentry>
 
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        <term><option>--debuglevel
 
219
        <replaceable>LEVEL</replaceable></option></term>
 
220
        <listitem>
 
221
          <para>
 
222
            Set the debugging log level.
 
223
            <replaceable>LEVEL</replaceable> is a string, one of
 
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            <quote><literal>CRITICAL</literal></quote>,
 
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            <quote><literal>ERROR</literal></quote>,
 
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            <quote><literal>WARNING</literal></quote>,
 
227
            <quote><literal>INFO</literal></quote>, or
 
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            <quote><literal>DEBUG</literal></quote>, in order of
 
229
            increasing verbosity.  The default level is
 
230
            <quote><literal>WARNING</literal></quote>.
 
231
          </para>
 
232
        </listitem>
 
233
      </varlistentry>
 
234
      
 
235
      <varlistentry>
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        <term><option>--priority <replaceable>
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        PRIORITY</replaceable></option></term>
199
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        <listitem>
200
 
          <xi:include href="mandos-options.xml" xpointer="priority"/>
 
239
          <xi:include href="mandos-options.xml"
 
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                      xpointer="priority_compat"/>
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        </listitem>
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      </varlistentry>
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          <xi:include href="mandos-options.xml" xpointer="ipv6"/>
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        </listitem>
252
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      </varlistentry>
 
293
      
 
294
      <varlistentry>
 
295
        <term><option>--no-restore</option></term>
 
296
        <listitem>
 
297
          <xi:include href="mandos-options.xml" xpointer="restore"/>
 
298
          <para>
 
299
            See also <xref linkend="persistent_state"/>.
 
300
          </para>
 
301
        </listitem>
 
302
      </varlistentry>
 
303
      
 
304
      <varlistentry>
 
305
        <term><option>--statedir
 
306
        <replaceable>DIRECTORY</replaceable></option></term>
 
307
        <listitem>
 
308
          <xi:include href="mandos-options.xml" xpointer="statedir"/>
 
309
        </listitem>
 
310
      </varlistentry>
 
311
      
 
312
      <varlistentry>
 
313
        <term><option>--socket
 
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        <replaceable>FD</replaceable></option></term>
 
315
        <listitem>
 
316
          <xi:include href="mandos-options.xml" xpointer="socket"/>
 
317
        </listitem>
 
318
      </varlistentry>
 
319
      
 
320
      <varlistentry>
 
321
        <term><option>--foreground</option></term>
 
322
        <listitem>
 
323
          <xi:include href="mandos-options.xml"
 
324
                      xpointer="foreground"/>
 
325
        </listitem>
 
326
      </varlistentry>
 
327
      
 
328
      <varlistentry>
 
329
        <term><option>--no-zeroconf</option></term>
 
330
        <listitem>
 
331
          <xi:include href="mandos-options.xml" xpointer="zeroconf"/>
 
332
        </listitem>
 
333
      </varlistentry>
 
334
      
253
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    </variablelist>
254
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  </refsect1>
255
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329
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      for some time, the client is assumed to be compromised and is no
330
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      longer eligible to receive the encrypted password.  (Manual
331
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      intervention is required to re-enable a client.)  The timeout,
332
 
      checker program, and interval between checks can be configured
333
 
      both globally and per client; see <citerefentry>
334
 
      <refentrytitle>mandos-clients.conf</refentrytitle>
335
 
      <manvolnum>5</manvolnum></citerefentry>.  A client successfully
336
 
      receiving its password will also be treated as a successful
337
 
      checker run.
 
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      extended timeout, checker program, and interval between checks
 
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      can be configured both globally and per client; see
 
416
      <citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>
 
417
      <manvolnum>5</manvolnum></citerefentry>.
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    </para>
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  </refsect1>
340
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362
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    <title>LOGGING</title>
363
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    <para>
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      The server will send log message with various severity levels to
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      <filename>/dev/log</filename>.  With the
 
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      <filename class="devicefile">/dev/log</filename>.  With the
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      <option>--debug</option> option, it will log even more messages,
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      and also show them on the console.
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    </para>
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  </refsect1>
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451
  <refsect1 id="persistent_state">
 
452
    <title>PERSISTENT STATE</title>
 
453
    <para>
 
454
      Client settings, initially read from
 
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      <filename>clients.conf</filename>, are persistent across
 
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      restarts, and run-time changes will override settings in
 
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      <filename>clients.conf</filename>.  However, if a setting is
 
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      <emphasis>changed</emphasis> (or a client added, or removed) in
 
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      <filename>clients.conf</filename>, this will take precedence.
 
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    </para>
 
461
  </refsect1>
 
462
  
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  <refsect1 id="dbus_interface">
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    <title>D-BUS INTERFACE</title>
373
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    <para>
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        </listitem>
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      </varlistentry>
437
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      <varlistentry>
438
 
        <term><filename>/var/run/mandos.pid</filename></term>
 
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        <term><filename>/run/mandos.pid</filename></term>
439
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        <listitem>
440
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          <para>
441
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            The file containing the process id of the
442
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            <command>&COMMANDNAME;</command> process started last.
 
535
            <emphasis >Note:</emphasis> If the <filename
 
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            class="directory">/run</filename> directory does not
 
537
            exist, <filename>/var/run/mandos.pid</filename> will be
 
538
            used instead.
 
539
          </para>
 
540
        </listitem>
 
541
      </varlistentry>
 
542
      <varlistentry>
 
543
        <term><filename class="devicefile">/dev/log</filename></term>
 
544
      </varlistentry>
 
545
      <varlistentry>
 
546
        <term><filename
 
547
        class="directory">/var/lib/mandos</filename></term>
 
548
        <listitem>
 
549
          <para>
 
550
            Directory where persistent state will be saved.  Change
 
551
            this with the <option>--statedir</option> option.  See
 
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            also the <option>--no-restore</option> option.
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          </para>
444
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        </listitem>
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      </varlistentry>
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      backtrace.  This could be considered a feature.
474
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    </para>
475
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    <para>
476
 
      Currently, if a client is disabled due to having timed out, the
477
 
      server does not record this fact onto permanent storage.  This
478
 
      has some security implications, see <xref linkend="clients"/>.
479
 
    </para>
480
 
    <para>
481
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      There is no fine-grained control over logging and debug output.
482
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    </para>
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    <para>
484
 
      Debug mode is conflated with running in the foreground.
485
 
    </para>
486
 
    <para>
487
 
      The console log messages do not show a time stamp.
488
 
    </para>
489
 
    <para>
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      This server does not check the expire time of clients’ OpenPGP
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      keys.
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    </para>
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    <informalexample>
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      <para>
507
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        Run the server in debug mode, read configuration files from
508
 
        the <filename>~/mandos</filename> directory, and use the
509
 
        Zeroconf service name <quote>Test</quote> to not collide with
510
 
        any other official Mandos server on this host:
 
607
        the <filename class="directory">~/mandos</filename> directory,
 
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        and use the Zeroconf service name <quote>Test</quote> to not
 
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        collide with any other official Mandos server on this host:
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      </para>
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      <para>
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        compromised if they are gone for too long.
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      </para>
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      <para>
565
 
        If a client is compromised, its downtime should be duly noted
566
 
        by the server which would therefore disable the client.  But
567
 
        if the server was ever restarted, it would re-read its client
568
 
        list from its configuration file and again regard all clients
569
 
        therein as enabled, and hence eligible to receive their
570
 
        passwords.  Therefore, be careful when restarting servers if
571
 
        it is suspected that a client has, in fact, been compromised
572
 
        by parties who may now be running a fake Mandos client with
573
 
        the keys from the non-encrypted initial <acronym>RAM</acronym>
574
 
        image of the client host.  What should be done in that case
575
 
        (if restarting the server program really is necessary) is to
576
 
        stop the server program, edit the configuration file to omit
577
 
        any suspect clients, and restart the server program.
578
 
      </para>
579
 
      <para>
580
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        For more details on client-side security, see
581
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        <citerefentry><refentrytitle>mandos-client</refentrytitle>
582
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        <manvolnum>8mandos</manvolnum></citerefentry>.
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  <refsect1 id="see_also">
588
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    <title>SEE ALSO</title>
589
673
    <para>
590
 
      <citerefentry>
591
 
        <refentrytitle>mandos-clients.conf</refentrytitle>
592
 
        <manvolnum>5</manvolnum></citerefentry>, <citerefentry>
593
 
        <refentrytitle>mandos.conf</refentrytitle>
594
 
        <manvolnum>5</manvolnum></citerefentry>, <citerefentry>
595
 
        <refentrytitle>mandos-client</refentrytitle>
596
 
        <manvolnum>8mandos</manvolnum></citerefentry>, <citerefentry>
597
 
        <refentrytitle>sh</refentrytitle><manvolnum>1</manvolnum>
598
 
      </citerefentry>
 
674
      <citerefentry><refentrytitle>intro</refentrytitle>
 
675
      <manvolnum>8mandos</manvolnum></citerefentry>,
 
676
      <citerefentry><refentrytitle>mandos-clients.conf</refentrytitle>
 
677
      <manvolnum>5</manvolnum></citerefentry>,
 
678
      <citerefentry><refentrytitle>mandos.conf</refentrytitle>
 
679
      <manvolnum>5</manvolnum></citerefentry>,
 
680
      <citerefentry><refentrytitle>mandos-client</refentrytitle>
 
681
      <manvolnum>8mandos</manvolnum></citerefentry>,
 
682
      <citerefentry><refentrytitle>sh</refentrytitle>
 
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      <manvolnum>1</manvolnum></citerefentry>
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    </para>
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    <variablelist>
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      <varlistentry>
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      </varlistentry>
623
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      <varlistentry>
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709
        <term>
625
 
          <ulink url="http://www.gnu.org/software/gnutls/"
626
 
          >GnuTLS</ulink>
 
710
          <ulink url="http://gnutls.org/">GnuTLS</ulink>
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        </term>
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      <listitem>
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        <para>
667
751
      </varlistentry>
668
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      <varlistentry>
669
753
        <term>
670
 
          RFC 4346: <citetitle>The Transport Layer Security (TLS)
671
 
          Protocol Version 1.1</citetitle>
 
754
          RFC 5246: <citetitle>The Transport Layer Security (TLS)
 
755
          Protocol Version 1.2</citetitle>
672
756
        </term>
673
757
      <listitem>
674
758
        <para>
675
 
          TLS 1.1 is the protocol implemented by GnuTLS.
 
759
          TLS 1.2 is the protocol implemented by GnuTLS.
676
760
        </para>
677
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      </listitem>
678
762
      </varlistentry>
688
772
      </varlistentry>
689
773
      <varlistentry>
690
774
        <term>
691
 
          RFC 5081: <citetitle>Using OpenPGP Keys for Transport Layer
692
 
          Security</citetitle>
 
775
          RFC 6091: <citetitle>Using OpenPGP Keys for Transport Layer
 
776
          Security (TLS) Authentication</citetitle>
693
777
        </term>
694
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      <listitem>
695
779
        <para>