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  • Committer: teddy at recompile
  • Date: 2020-04-05 21:30:59 UTC
  • mto: This revision was merged to the branch mainline in revision 398.
  • Revision ID: teddy@recompile.se-20200405213059-fb2a61ckqynrmatk
Fix file descriptor leak in mandos-client

When the local network has Mandos servers announcing themselves using
real, globally reachable, IPv6 addresses (i.e. not link-local
addresses), but there is no router on the local network providing IPv6
RA (Router Advertisement) packets, the client cannot reach the server
by normal means, since the client only has a link-local IPv6 address,
and has no usable route to reach the server's global IPv6 address.
(This is not a common situation, and usually only happens when the
router itself reboots and runs a Mandos client, since it cannot then
give RA packets to itself.)  The client code has a solution for
this, which consists of adding a temporary local route to reach the
address of the server during communication, and removing this
temporary route afterwards.

This solution with a temporary route works, but has a file descriptor
leak; it leaks one file descriptor for each addition and for each
removal of a route.  If one server requiring an added route is present
on the network, but no servers gives a password, making the client
retry after the default ten seconds, and we furthermore assume a
default 1024 open files limit, the client runs out of file descriptors
after about 90 minutes, after which time the client process will be
useless and fail to retrieve any passwords, necessitating manual
password entry via the keyboard.

Fix this by eliminating the file descriptor leak in the client.

* plugins.d/mandos-client.c (add_delete_local_route): Do
  close(devnull) also in parent process, also if fork() fails, and on
  any failure in child process.

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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 "password-prompt">
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<!ENTITY TIMESTAMP "2009-01-04">
 
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<!ENTITY TIMESTAMP "2019-07-27">
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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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      <year>2014</year>
 
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      <year>2015</year>
 
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      <year>2016</year>
 
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      <year>2017</year>
 
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      <year>2018</year>
 
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      <year>2019</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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        >PREFIX</replaceable></arg>
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      </group>
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      <sbr/>
 
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      <arg choice="opt">
 
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        <option>--prompt <replaceable>PROMPT</replaceable></option>
 
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      </arg>
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      <arg choice="opt"><option>--debug</option></arg>
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    </cmdsynopsis>
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    <cmdsynopsis>
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      wrapper, although actual use of that function is not guaranteed
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      or implied.
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    </para>
 
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    <para>
 
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      This program tries to detect if a Plymouth daemon
 
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      (<citerefentry><refentrytitle
 
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      >plymouthd</refentrytitle><manvolnum>8</manvolnum></citerefentry>)
 
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      is running, by looking for a
 
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      <filename>/run/plymouth/pid</filename> file or a process named
 
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      <quote><literal>plymouthd</literal></quote>.  If it is detected,
 
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      this process will immediately exit without doing anything.
 
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    </para>
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  </refsect1>
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  <refsect1 id="options">
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      </varlistentry>
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      <varlistentry>
 
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        <term><option>--prompt=<replaceable
 
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        >PROMPT</replaceable></option></term>
 
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        <listitem>
 
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          <para>
 
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            The password prompt.  Using this option will make this
 
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            program ignore the <envar>CRYPTTAB_SOURCE</envar> and
 
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            <envar>CRYPTTAB_NAME</envar> environment variables.
 
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          </para>
 
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        </listitem>
 
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      </varlistentry>
 
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      <varlistentry>
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        <term><option>--debug</option></term>
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        <listitem>
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          <para>
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    <title>ENVIRONMENT</title>
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    <variablelist>
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      <varlistentry>
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        <term><envar>cryptsource</envar></term>
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        <term><envar>crypttarget</envar></term>
 
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        <term><envar>CRYPTTAB_SOURCE</envar></term>
 
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        <term><envar>CRYPTTAB_NAME</envar></term>
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        <listitem>
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          <para>
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            If set, these environment variables will be assumed to
 
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            If set, and if the <option>--prompt</option> option is not
 
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            used, these environment variables will be assumed to
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            contain the source device name and the target device
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            mapper name, respectively, and will be shown as part of
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            the prompt.
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        <para>
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          These variables will normally be inherited from
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          <citerefentry><refentrytitle>plugin-runner</refentrytitle>
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          <manvolnum>8mandos</manvolnum></citerefentry>, which will
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          normally have inherited them from
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          <filename>/scripts/local-top/cryptroot</filename> in the
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          initial <acronym>RAM</acronym> disk environment, which will
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          have set them from parsing kernel arguments and
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          <filename>/conf/conf.d/cryptroot</filename> (also in the
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          initial RAM disk environment), which in turn will have been
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          created when the initial RAM disk image was created by
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          <filename
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          >/usr/share/initramfs-tools/hooks/cryptroot</filename>, by
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          extracting the information of the root file system from
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          <filename >/etc/crypttab</filename>.
 
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          <manvolnum>8mandos</manvolnum></citerefentry>, which might
 
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          have in turn inherited them from its calling process.
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        </para>
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        <para>
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          This behavior is meant to exactly mirror the behavior of
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          <command>askpass</command>, the default password prompter.
 
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          <command>askpass</command>, the default password prompter
 
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          from initramfs-tools.
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        </para>
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        </listitem>
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      </varlistentry>
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  <refsect1 id="bugs">
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    <title>BUGS</title>
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    <para>
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      None are known at this time.
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    </para>
 
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    <xi:include href="../bugs.xml"/>
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  </refsect1>
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  <refsect1 id="example">
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  <refsect1 id="see_also">
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    <title>SEE ALSO</title>
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    <para>
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      <citerefentry><refentrytitle>crypttab</refentrytitle>
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      <manvolnum>5</manvolnum></citerefentry>
 
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      <citerefentry><refentrytitle>intro</refentrytitle>
 
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      <manvolnum>8mandos</manvolnum></citerefentry>,
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      <citerefentry><refentrytitle>mandos-client</refentrytitle>
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      <manvolnum>8mandos</manvolnum></citerefentry>
 
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      <manvolnum>8mandos</manvolnum></citerefentry>,
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      <citerefentry><refentrytitle>plugin-runner</refentrytitle>
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      <manvolnum>8mandos</manvolnum></citerefentry>,
 
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      <citerefentry><refentrytitle>plymouthd</refentrytitle>
 
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      <manvolnum>8</manvolnum></citerefentry>
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    </para>
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  </refsect1>
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</refentry>