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<chapter id="sso">
  <title>Single Sign On</title>

  <para>Cockpit can use Kerberos for Single Sign On authentication, where users are
    automatically authenticated if they have a valid Kerberos ticket.</para>

  <section id="sso-server">
    <title>Server Requirements</title>

    <para>To authenticate users, the server that Cockpit is running on must be
      joined to a domain. This can usually be accomplished using the
      <ulink url="https://freedesktop.org/software/realmd/docs/realm.html"><code>realm join example.com</code></ulink>
      command.</para>

    <para>The domain must be resolvable by DNS. For instance, the SRV records of the
      kerberos server should be resolvable:</para>

<programlisting>
$ host -t SRV  _kerberos._udp.example.com
_kerberos._udp.example.com has SRV record 0 100 88 dc.example.com
</programlisting>

    <para>The server running Cockpit should have a fully qualified name that ends with
      the domain name.</para>

    <para>There must be a valid Kerberos host key for the server in the <code>/etc/krb5.keytab</code>
      file. Alternatively, if you would like to use a different keytab, you can do so
      by placing it in <code>/etc/cockpit/krb5.keytab</code>, or below <code>$XDG_CONFIG_DIRS</code>
      if set (see <ulink url="./cockpit.conf.5.html">cockpit.conf</ulink>). It may be necessary to
      create a kerberos service principal and update the keytab if it is not present.
      Depending on your domain type different service names are required:</para>

    <variablelist>
      <varlistentry>
        <term>Active Directory</term>
        <listitem><para><code>HOST/server.example.com@EXAMPLE.COM</code></para></listitem>
      </varlistentry>
      <varlistentry>
        <term>IPA and MIT</term>
        <listitem><para><code>HTTP/server.example.com@EXAMPLE.COM</code></para></listitem>
      </varlistentry>
    </variablelist>

    <para>When joining an IPA domain with Cockpit and the <code>ipa</code> command line tool is
      available, both the service principal name and a <code>/etc/cockpit/krb5.keytab</code> get
      created automatically, so that Kerberos based single sign on into Cockpit works out of the
      box. If you want/need to do this by hand or in a script, first create or modify the
      <code>HTTP/</code> service principal:</para>

<programlisting>
$ sudo ipa service-add --ok-as-delegate=true --ok-to-auth-as-delegate=true \
    HTTP/server.example.com@EXAMPLE.COM
# or, if it already exists, just enable delegation:
$ sudo ipa service-mod --ok-as-delegate=true --ok-to-auth-as-delegate=true \
    HTTP/server.example.com@EXAMPLE.COM
</programlisting>

    <para>Then generate a key for that principal:</para>

<programlisting>
$ sudo ipa-getkeytab -p HTTP/server.example.com@EXAMPLE.COM -k /etc/cockpit/krb5.keytab
</programlisting>

    <para>The following command can be used to list the <code>/etc/cockpit/krb5.keytab</code>:</para>

<programlisting>
$ sudo klist -k /etc/cockpit/krb5.keytab
</programlisting>

    <para>Lastly accounts from the domain must be resolvable to unix accounts on the server
      running Cockpit. For example:</para>

<programlisting>
$ getent passwd user@example.com
user@example.com:*:381001109:381000513:User Name:/home/user:/bin/sh
</programlisting>

    <para>If you wish to delegate your kerberos credentials to Cockpit, and allow Cockpit
      to then connect to other machines using those credentials, you should enable delegation
      for the hosts running Cockpit, and in some cases the <code>HTTP</code> service as well.
      When joining an IPA domain, this is enabled by default.</para>

    <para>Domain admins (usually the <code>admins@example.com</code> group) should normally
      also be able to administer any joined machine. Enable sudo access for that group
      with the following command on the IPA server, for version 4.7.1 and later:</para>

<programlisting>
ipa-advise enable-admins-sudo | sh -ex
</programlisting>

    <para>On earlier FreeIPA versions, run these commands instead, as a domain admin on
      any joined machine:</para>

<programlisting>
ipa sudorule-add --hostcat=all --cmdcat=all All
ipa sudorule-add-user --groups=admins All
</programlisting>

    <para>Note that this does not change security properties; domain admins can give this
      privilege to themselves, so it is safe to enable by default.</para>
  </section>

  <section id="sso-client">
    <title>Client Requirements</title>

    <para>The client side, where your web browser is running, should have a valid kerberos
      ticket in the current user session. A command like this will get one:</para>

<programlisting>
$ kinit user@EXAMPLE.COM
Password for user@EXAMPLE.COM:
</programlisting>

    <para>In addition your browser must be usually be configured to allow kerberos
      authentication for the domain.</para>

    <variablelist>
      <varlistentry>
        <term>Mozilla Firefox</term>
        <listitem><para>Go to <code>about:config</code> and set the
          <code>network.negotiate-auth.trusted-uris</code> setting to your domain name
          preceded by a dot, ie: <code>.example.com</code></para></listitem>
      </varlistentry>
      <varlistentry>
        <term>Google Chrome</term>
        <listitem><para>
          On Linux: create the file
          <code>/etc/opt/chrome/policies/managed/example-com.json</code>
          with the contents:
<programlisting>
{
  "AuthServerWhitelist": "*example.com"
}
</programlisting>
          and restart the browser. On other platforms, exit your browser
          completely, and start it with a command line like this:
          <code>google-chrome --auth-server-whitelist=*example.com</code>
          </para></listitem>
      </varlistentry>
    </variablelist>

    <para>Use a fully qualified server name (with the domain name at the end) to access
      Cockpit in your web browser.</para>

    <para>If you wish to connect from one server to another in Cockpit using kerberos SSO,
      then you have to explicitly enable all sorts of things. For starters, make sure that
      delegated credentials are allowed by your domain (see above). Next when requesting your
      kerberos ticket make sure that forwardable tickets are requested:</para>

<programlisting>
$ kinit -f user@EXAMPLE.COM
Password for user@EXAMPLE.COM:
</programlisting>

    <para>Make sure that the forwardable flag <code>F</code> is present in your ticket:</para>

<programlisting>
$ klist -f
Ticket cache: KEYRING:persistent:1000:1000
Default principal: user@EXAMPLE.COM

Valid starting       Expires              Service principal
18.03.2017 05:39:23  19.03.2017 05:39:20  krbtgt/EXAMPLE.COM@EXAMPLE.COM
	Flags: FIA
</programlisting>

    <para>Lastly configure your browser to allow delegated, forwardable kerberos
      credentials to be sent to Cockpit:</para>

    <variablelist>
      <varlistentry>
        <term>Mozilla Firefox</term>
        <listitem><para>Go to <code>about:config</code> and set the
          <code>network.negotiate-auth.delegation-uris</code> setting to your domain name
          preceded by a dot, ie: <code>.example.com</code></para></listitem>
      </varlistentry>
      <varlistentry>
        <term>Google Chrome</term>
        <listitem><para>
          On Linux: create the file
          <code>/etc/opt/chrome/policies/managed/example-com.json</code>
          with the contents:
<programlisting>
{
  "AuthServerWhitelist": "*example.com",
  "AuthNegotiateDelegateWhitelist": "*example.com"
}
</programlisting>
          and restart the browser. On other platforms, exit your browser
          completely, and start it with a command line like this:
          <code>google-chrome --auth-server-whitelist=*example.com --auth-negotiate-delegate-whitelist=*example.com</code>
          </para></listitem>
      </varlistentry>
    </variablelist>

  </section>

</chapter>
