<?xml version="1.0" encoding="UTF-8"?>
<chapter id="HDRWQ355">
  <title>Managing Server Encryption Keys</title>

  <para>This chapter explains how to maintain your cell's server encryption keys, which are vital for secure communications in
  AFS.</para>

  <sect1 id="HDRWQ356">
    <title>Summary of Instructions</title>

    <para>This chapter explains how to perform the following tasks by using the indicated commands:</para>

    <informaltable frame="none">
      <tgroup cols="2">
        <colspec colwidth="70*" />

        <colspec colwidth="30*" />

        <tbody>
          <row>
            <entry>Add a new server encryption key</entry>

            <entry><emphasis role="bold">bos addkey</emphasis> and <emphasis role="bold">kas setpassword</emphasis></entry>
          </row>

          <row>
            <entry>Inspect key checksums in the Authentication Database</entry>

            <entry><emphasis role="bold">kas examine</emphasis></entry>
          </row>

          <row>
            <entry>Inspect key checksums in the <emphasis role="bold">KeyFile</emphasis></entry>

            <entry><emphasis role="bold">bos listkeys</emphasis></entry>
          </row>

          <row>
            <entry>Remove an old server encryption key</entry>

            <entry><emphasis role="bold">bos removekey</emphasis></entry>
          </row>
        </tbody>
      </tgroup>
    </informaltable>
  </sect1>

  <sect1 id="HDRWQ358">
    <title>About Server Encryption Keys</title>

    <indexterm>
      <primary>server encryption key</primary>

      <secondary>defined</secondary>
    </indexterm>

    <indexterm>
      <primary>AFS</primary>

      <secondary>server encryption key</secondary>

      <see>server encryption key</see>
    </indexterm>

    <para>An encryption key is a string of octal numbers used to encrypt and decrypt packets of information. In AFS, a server
    encryption key is the key used to protect information being transferred between AFS server processes and between them and their
    clients. A server encryption key is essentially a password for a server process and like a user password is stored in the
    Authentication Database.</para>

    <para>Maintaining your cell's server encryption keys properly is the most basic way to protect the information in your AFS
    filespace from access by unauthorized users.</para>

    <sect2 id="Header_412">
      <title>Keys and Mutual Authentication: A Review</title>

      <indexterm>
        <primary>mutual authentication</primary>

        <secondary>server encryption key's role</secondary>
      </indexterm>

      <indexterm>
        <primary>server encryption key</primary>

        <secondary>role in mutual authentication</secondary>
      </indexterm>

      <indexterm>
        <primary>Ticket Granting Service</primary>
      </indexterm>

      <indexterm>
        <primary>TGS</primary>
      </indexterm>

      <indexterm>
        <primary>server ticket</primary>
      </indexterm>

      <indexterm>
        <primary>session key</primary>
      </indexterm>

      <para>Server encryption keys play a central role in the mutual authentication between client and server processes in AFS. For
      a more detailed description of mutual authentication, see <link linkend="HDRWQ75">A More Detailed Look at Mutual
      Authentication</link>.</para>

      <para>When a client wants to contact an AFS server, it first contacts the Ticket Granting Service (TGS) module of the
      Authentication Server. After verifying the client's identity (based indirectly on the password of the human user whom the
      client represents), the TGS gives the client a server ticket. This ticket is encrypted with the server's encryption key. (The
      TGS also invents a second encryption key, called the session key, to be used only for a single episode of communication
      between server and client. The server ticket and session key, together with other pieces of information, are collectively
      referred to as a token.)</para>

      <para>The client cannot read the server ticket or token because it does not know the server encryption key. However, the
      client sends it to the AFS server along with service requests, because the ticket proves to the AFS server processes that it
      has already authenticated with the TGS. AFS servers trust the TGS to grant tickets only to valid clients. The fact that the
      client possesses a ticket encrypted with the server's encryption key proves to the server that the client is valid. On the
      other hand, the client assumes that only a genuine AFS server knows the server encryption key needed to decrypt the ticket.
      The server's ability to decrypt the ticket and understand its contents proves to the client that the server is
      legitimate.</para>
    </sect2>

    <sect2 id="Header_413">
      <title>Maintaining AFS Server Encryption Keys</title>

      <para>As you maintain your cell's server encryption keys, keep the following in mind. <itemizedlist>
          <listitem>
            <para>Change the key frequently to enhance your cell's security. Changing the key at least once a month is strongly
            recommended.</para>

            <indexterm>
              <primary>server encryption key</primary>

              <secondary>changing frequently</secondary>
            </indexterm>
          </listitem>

          <listitem>
            <para>The AFS server encryption key currently in use is stored in two places. When you add a new key, you must make
            changes in both places and make them in the correct order, as instructed in <link linkend="HDRWQ362">Adding Server
            Encryption Keys</link>. Failure to follow the instructions can seriously impair cell functioning, as clients and servers
            become unable to communicate. The two storage sites for the current server encryption key are the following:
            <orderedlist>
                <listitem>
                  <para>The file <emphasis role="bold">/usr/afs/etc/KeyFile</emphasis> on the local disk of every file server
                  machine. The file can list more than one key, each with an associated numerical identifier, the key version number
                  or kvno. A client token records the key version number of the key used to seal it, and the server process
                  retrieves the appropriate key from this file when the client presents the token.</para>

                  <indexterm>
                    <primary>key version number</primary>

                    <secondary>defined</secondary>
                  </indexterm>

                  <indexterm>
                    <primary>kvno</primary>

                    <secondary></secondary>

                    <see>key version number</see>
                  </indexterm>

                  <indexterm>
                    <primary>KeyFile file</primary>

                    <secondary>storage site for server encryption keys</secondary>
                  </indexterm>

                  <indexterm>
                    <primary>files</primary>

                    <secondary>/usr/afs/etc/KeyFile</secondary>
                  </indexterm>

                  <indexterm>
                    <primary>server encryption key</primary>

                    <secondary>KeyFile file</secondary>
                  </indexterm>
                </listitem>

                <listitem>
                  <para>The <emphasis role="bold">afs</emphasis> entry in the Authentication Database. The current server encryption
                  key is in the entry's password field, just like an individual user's scrambled password. The Authentication
                  Server's Ticket Granting Service (TGS) uses this key to encrypt the tokens it gives to clients. There is only a
                  single key in the entry, because the TGS never needs to read existing tokens, but only to generate new ones by
                  using the current key.</para>

                  <indexterm>
                    <primary>server encryption key</primary>

                    <secondary>Authentication Database</secondary>
                  </indexterm>

                  <indexterm>
                    <primary>Authentication Database</primary>

                    <secondary>site for AFS server encryption key</secondary>
                  </indexterm>

                  <indexterm>
                    <primary>Authentication Database</primary>

                    <secondary>afs entry</secondary>
                  </indexterm>
                </listitem>
              </orderedlist></para>

            <para>For instructions on creating the initial <emphasis role="bold">afs</emphasis> entry and <emphasis
            role="bold">KeyFile</emphasis> files as you install your cell's first server machine, see the OpenAFS Quick
            Beginnings.</para>
          </listitem>

          <listitem>
            <para>At any specific time, the tokens that the Authentication Server's Ticket Granting Service gives to clients are
            sealed with only one of the server encryption keys, namely the one stored in the <emphasis role="bold">afs</emphasis>
            entry in the Authentication Database.</para>
          </listitem>

          <listitem>
            <para>When you add a new server encryption key, you cannot immediately remove the former key from the <emphasis
            role="bold">/usr/afs/etc/KeyFile</emphasis> file on the local disk of every AFS server machine. Any time that you add a
            new key, it is likely that some clients still have valid, unexpired tokens sealed with the previous key. The more
            frequently you change the server encryption key, the more such tickets there are likely to be. To be able to grant
            service appropriately to clients with such tokens, an AFS server process must still be able to access the server
            encryption key used to seal it.</para>

            <para>You can safely delete an old server encryption key only when it is certain that no clients have tokens sealed with
            that key. In general, wait a period of time at least as long as the maximum token lifetime in your cell. By default, the
            maximum token lifetime for users is 25 hours (except for users whose Authentication Database entries were created by
            using the 3.0 version of AFS, for whom the default is 100 hours). You can use the <emphasis
            role="bold">-lifetime</emphasis> argument to the <emphasis role="bold">kas setfields</emphasis> command to change this
            default.</para>

            <para>Instructions for removing obsolete keys appear in <link linkend="HDRWQ368">Removing Server Encryption
            Keys</link>.</para>
          </listitem>

          <listitem>
            <para>You create a new AFS server encryption key in much the same way regular users change their passwords, by providing
            a character string that is converted into an encryption key automatically. See <link linkend="HDRWQ362">Adding Server
            Encryption Keys</link>.</para>

            <indexterm>
              <primary>server encryption key</primary>

              <secondary>password-like nature</secondary>
            </indexterm>
          </listitem>

          <listitem>
            <para>In addition to using server encryption keys when communicating with clients, the server processes use them to
            protect communications with other server processes. Therefore, all server machines in your cell must have the same
            version of the <emphasis role="bold">KeyFile</emphasis> file. The easiest way to maintain consistency (if you run the
            United States edition of AFS) is to use the Update Server to distribute the contents of the system control machine's
            <emphasis role="bold">/usr/afs/etc</emphasis> directory to all of the other server machines. There are two implications:
            <itemizedlist>
                <listitem>
                  <para>You must run the <emphasis role="bold">upserver</emphasis> process on the system control machine and an
                  <emphasis role="bold">upclientetc</emphasis> process on all other server machines that references the system
                  control machine. The OpenAFS Quick Beginnings explains how to install both processes. For instructions on
                  verifying that the Update Server processes are running, see <link linkend="HDRWQ158">Displaying Process Status and
                  Information from the BosConfig File</link>.</para>

                  <indexterm>
                    <primary>Update Server</primary>

                    <secondary>distributor of KeyFile file</secondary>
                  </indexterm>
                </listitem>

                <listitem>
                  <para>Change the <emphasis role="bold">KeyFile</emphasis> file only on the system control machine (except in the
                  types of emergencies discussed in <link linkend="HDRWQ370">Handling Server Encryption Key Emergencies</link>). Any
                  changes you make on other server machines are overwritten the next time the <emphasis
                  role="bold">upclientetc</emphasis> process retrieves the contents of the system control machine's <emphasis
                  role="bold">/usr/afs/etc</emphasis> directory. By default, this happens every five minutes.</para>

                  <indexterm>
                    <primary>system control machine</primary>

                    <secondary>source for common KeyFile file</secondary>
                  </indexterm>
                </listitem>
              </itemizedlist></para>

            <para>If you run the international edition of AFS, do not use the Update Server to distribute the contents of the
            <emphasis role="bold">/usr/afs/etc</emphasis> directory, particularly the <emphasis role="bold">KeyFile</emphasis> file.
            The data in the file is too sensitive for transfer in unencrypted form, and because of United States government exports
            regulations the international edition of AFS does not include the necessary encryption routines in a form that the
            Update Server can use. You must instead modify the file on each server machine individually, taking care to enter the
            same key on every server machine.</para>
          </listitem>

          <listitem>
            <para>Never edit the <emphasis role="bold">KeyFile</emphasis> directly with a text editor. Instead, always use the
            appropriate <emphasis role="bold">bos</emphasis> commands as instructed in <link linkend="HDRWQ362">Adding Server
            Encryption Keys</link> and <link linkend="HDRWQ368">Removing Server Encryption Keys</link>.</para>
          </listitem>
        </itemizedlist></para>
    </sect2>
  </sect1>

  <sect1 id="HDRWQ359">
    <title>Displaying Server Encryption Keys</title>

    <para>To display the server encryption keys in the <emphasis role="bold">/usr/afs/etc/KeyFile</emphasis> file on any file server
    machine, use the <emphasis role="bold">bos listkeys</emphasis> command. Use the <emphasis role="bold">kas examine</emphasis>
    command to display the key in the Authentication Database's <emphasis role="bold">afs</emphasis> entry.</para>

    <indexterm>
      <primary>checksum</primary>
    </indexterm>

    <indexterm>
      <primary>server encryption key</primary>

      <secondary>checksum displayed</secondary>
    </indexterm>

    <para>By default the commands do not display the actual string of octal digits that constitute a key, but rather a checksum, a
    decimal number derived by encrypting a constant with the key. This prevents unauthorized users from easily accessing the actual
    key, which they can then use to falsify or eavesdrop on protected communications. The <emphasis role="bold">bos
    listkeys</emphasis> and <emphasis role="bold">kas examine</emphasis> commands generate the same checksum for a given key, so
    displaying checksums rather than actual keys is generally sufficient. If you suspect that the keys differ in a way that the
    checksums are not revealing, then you are probably experiencing authentication problems throughout your cell. The easiest
    solution is to create a new server encryption key following the instructions in <link linkend="HDRWQ362">Adding Server
    Encryption Keys</link> or <link linkend="HDRWQ370">Handling Server Encryption Key Emergencies</link>. Another common reason to
    issue the <emphasis role="bold">bos listkeys</emphasis> command is to display the key version numbers currently in use, in
    preparation for choosing the next one; here, the checksum is sufficient because the key itself is irrelevant.</para>

    <para>If it is important to display the actual octal digits, include the <emphasis role="bold">-showkey</emphasis> argument to
    both the <emphasis role="bold">bos listkeys</emphasis> and <emphasis role="bold">kas examine</emphasis> commands.</para>

    <indexterm>
      <primary>KeyFile file</primary>

      <secondary>displaying</secondary>
    </indexterm>

    <indexterm>
      <primary>displaying</primary>

      <secondary>KeyFile file</secondary>
    </indexterm>

    <indexterm>
      <primary>server encryption key</primary>

      <secondary>displaying from KeyFile file</secondary>
    </indexterm>

    <indexterm>
      <primary>displaying</primary>

      <secondary>server encryption keys in KeyFile file</secondary>
    </indexterm>

    <indexterm>
      <primary>commands</primary>

      <secondary>bos listkeys</secondary>
    </indexterm>

    <indexterm>
      <primary>bos commands</primary>

      <secondary>listkeys</secondary>
    </indexterm>

    <sect2 id="HDRWQ360">
      <title>To display the KeyFile file</title>

      <orderedlist>
        <listitem>
          <para>Verify that you are authenticated as a user listed in the <emphasis role="bold">/usr/afs/etc/UserList</emphasis>
          file. If necessary, issue the <emphasis role="bold">bos listusers</emphasis> command, which is fully described in <link
          linkend="HDRWQ593">To display the users in the UserList file</link>. <programlisting>
   % <emphasis role="bold">bos listusers</emphasis> &lt;<replaceable>machine name</replaceable>&gt;
</programlisting></para>
        </listitem>

        <listitem>
          <para>Issue the <emphasis role="bold">bos listkeys</emphasis> command to display the contents of one machine's <emphasis
          role="bold">/usr/afs/etc/KeyFile</emphasis> file. <programlisting>
   % <emphasis role="bold">bos listkeys</emphasis> &lt;<replaceable>machine name</replaceable>&gt; [<emphasis role="bold">-showkey</emphasis>]
</programlisting></para>

          <para>where <variablelist>
              <varlistentry>
                <term><emphasis role="bold">listk</emphasis></term>

                <listitem>
                  <para>Is the shortest acceptable abbreviation of <emphasis role="bold">listkeys</emphasis>.</para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><emphasis role="bold">machine name</emphasis></term>

                <listitem>
                  <para>Names a file server machine. In the normal case, it is acceptable to name any machine, because correct cell
                  functioning requires that the <emphasis role="bold">KeyFile</emphasis> file be the same on all of them.</para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><emphasis role="bold">-showkey</emphasis></term>

                <listitem>
                  <para>Displays the octal digits that constitute each key.</para>
                </listitem>
              </varlistentry>
            </variablelist></para>
        </listitem>
      </orderedlist>

      <para>In the following example, the output displays a checksum for each server encryption key rather than the actual octal
      digits. The penultimate line indicates when an administrator last changed the file, and the final line confirms that the
      output is complete.</para>

      <programlisting>
   % <emphasis role="bold">bos listkeys fs1.abc.com</emphasis>
   key 0 has cksum 972037177
   key 1 has cksum 2825165022
   Keys last changed on Wed Jan 13 11:20:29 1999. 
   All done.
</programlisting>

      <indexterm>
        <primary>Authentication Database</primary>

        <secondary>server encryption key</secondary>

        <tertiary>displaying</tertiary>
      </indexterm>

      <indexterm>
        <primary>displaying</primary>

        <secondary>server encryption key from Authentication Database</secondary>
      </indexterm>

      <indexterm>
        <primary>afs entry in Authentication Database</primary>

        <secondary>displaying</secondary>
      </indexterm>

      <indexterm>
        <primary>server encryption key</primary>

        <secondary>displaying from Authentication Database</secondary>
      </indexterm>

      <indexterm>
        <primary>commands</primary>

        <secondary>kas examine</secondary>
      </indexterm>

      <indexterm>
        <primary>kas commands</primary>

        <secondary>examine, to inspect afs key</secondary>
      </indexterm>
    </sect2>

    <sect2 id="HDRWQ361">
      <title>To display the afs key from the Authentication Database</title>

      <orderedlist>
        <listitem>
          <para>Issue the <emphasis role="bold">kas examine</emphasis> command to display the <emphasis role="bold">afs</emphasis>
          entry in the Authentication Database.</para>

          <para>The Authentication Server performs its own authentication rather than accepting your existing AFS token. By default,
          it authenticates your local (UNIX) identity, which possibly does not correspond to an AFS-privileged administrator.
          Include the <emphasis role="bold">-admin</emphasis> argument to name an identity that has the
          <computeroutput>ADMIN</computeroutput> flag on its Authentication Database entry. To verify that an entry has the flag,
          issue the <emphasis role="bold">kas examine</emphasis> command as described in <link linkend="HDRWQ590">To check if the
          ADMIN flag is set</link>.</para>

          <programlisting>
   % <emphasis role="bold">kas examine afs</emphasis> [<emphasis role="bold">-showkey</emphasis>]  \
                 <emphasis role="bold">-admin</emphasis>  &lt;<replaceable>admin principal to use for authentication</replaceable>&gt;  
   Administrator's (admin_user) password: &lt;<replaceable>admin_password</replaceable>&gt;
</programlisting>

          <para>where <variablelist>
              <varlistentry>
                <term><emphasis role="bold">e</emphasis></term>

                <listitem>
                  <para>Is the shortest acceptable abbreviation of <emphasis role="bold">examine</emphasis>.</para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><emphasis role="bold">afs</emphasis></term>

                <listitem>
                  <para>Designates the <emphasis role="bold">afs</emphasis> entry.</para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><emphasis role="bold">-showkey</emphasis></term>

                <listitem>
                  <para>Displays the octal digits that constitute the key.</para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><emphasis role="bold">-admin</emphasis></term>

                <listitem>
                  <para>Names an administrative account with the <computeroutput>ADMIN</computeroutput> flag on its Authentication
                  Database entry, such as <emphasis role="bold">admin</emphasis>. The password prompt echoes it as admin_user. Enter
                  the appropriate password as admin_password.</para>
                </listitem>
              </varlistentry>
            </variablelist></para>
        </listitem>
      </orderedlist>

      <para>In the following example, the <emphasis role="bold">admin</emphasis> user displays the <emphasis
      role="bold">afs</emphasis> entry without using the <emphasis role="bold">-showkey</emphasis> flag. The second line shows the
      key version number in parentheses and the key's checksum. The line that begins with the string <computeroutput>last
      mod</computeroutput> reports the date on which the indicated administrator changed the key. There is no necessary relationship
      between this date and the date reported by the <emphasis role="bold">bos listkeys</emphasis> command, because the latter date
      changes for any type of change to the <emphasis role="bold">KeyFile</emphasis> file, not just a key addition. For a
      description of the other lines in the output from the <emphasis role="bold">kas examine</emphasis> command, see its reference
      page in the OpenAFS Administration Reference.</para>

      <programlisting>
   % <emphasis role="bold">kas examine afs  -admin admin</emphasis>
   Administrator's (admin) password: &lt;<replaceable>admin_password</replaceable>&gt;
   User data for afs
    key (1) cksum is 2825165022, last cpw: no date
    password will never expire.
    An unlimited number of unsuccessful authentications is permitted.
    entry expires on never. Max ticket lifetime 100.00 hours.
    last mod on Wed Jan 13 11:21:36 1999 by admin
    permit password reuse
</programlisting>
    </sect2>
  </sect1>

  <sect1 id="HDRWQ362">
    <title>Adding Server Encryption Keys</title>

    <indexterm>
      <primary>adding</primary>

      <secondary>server encryption key to KeyFile file</secondary>
    </indexterm>

    <indexterm>
      <primary>defining</primary>

      <secondary>server encryption key</secondary>
    </indexterm>

    <indexterm>
      <primary>creating</primary>

      <secondary>server encryption key</secondary>
    </indexterm>

    <indexterm>
      <primary>server encryption key</primary>

      <secondary>adding to KeyFile file</secondary>
    </indexterm>

    <indexterm>
      <primary>KeyFile file</primary>

      <secondary>adding server encryption key</secondary>
    </indexterm>

    <indexterm>
      <primary>Authentication Database</primary>

      <secondary>server encryption key</secondary>

      <tertiary>setting</tertiary>
    </indexterm>

    <indexterm>
      <primary>defining</primary>

      <secondary>server encryption key in Authentication Database</secondary>
    </indexterm>

    <indexterm>
      <primary>afs entry in Authentication Database</primary>

      <secondary>setting server encryption key</secondary>
    </indexterm>

    <indexterm>
      <primary>server encryption key</primary>

      <secondary>setting in Authentication Database</secondary>
    </indexterm>

    <para>As noted, AFS records server encryption keys in two separate places: <orderedlist>
        <listitem>
          <para>In the file <emphasis role="bold">/usr/afs/etc/KeyFile</emphasis> on the local disk of each server machine, for use
          by the AFS server processes running on the machine</para>
        </listitem>

        <listitem>
          <para>In the <emphasis role="bold">afs</emphasis> entry in the Authentication Database, for use by the Ticket Granting
          Service (TGS) when creating tokens</para>
        </listitem>
      </orderedlist></para>

    <para>To ensure that server processes and the TGS share the same AFS server encryption key, execute all the steps in this
    section without interruption.</para>

    <para>The following instructions include a step in which you restart the database server processes (the Authentication, Backup,
    Protection, and Volume Location Server processes) on all database server machines. As a database server process starts, it reads
    in the server encryption key that has the highest key version number in the <emphasis role="bold">KeyFile</emphasis> file and
    uses it to protect the messages that it sends for synchronizing the database and maintaining quorum. It uses the same key
    throughout its lifetime, which can be for an extended period, even if you remove the key from the <emphasis
    role="bold">KeyFile</emphasis> file. However, if one of the peer database server processes restarts and the others do not,
    quorum and database synchronization break down because the processes are no longer using the same key: the restarted process is
    using the key that currently has the highest key version number, and the other processes are still using the key they read in
    when they originally started. To avoid this problem, it is safest to restart all of the database server processes when adding a
    new key.</para>

    <para>After adding a new key, you can remove obsolete keys from the <emphasis role="bold">KeyFile</emphasis> file to prevent it
    from becoming cluttered. However, you must take care not to remove keys that client or server processes are still using. For
    discussion and instructions, see <link linkend="HDRWQ368">Removing Server Encryption Keys</link>.</para>

    <sect2 id="HDRWQ363">
      <title>To add a new server encryption key</title>

      <orderedlist>
        <listitem>
          <para>Verify that you are authenticated as a user listed in the <emphasis role="bold">/usr/afs/etc/UserList</emphasis>
          file. If necessary, issue the <emphasis role="bold">bos listusers</emphasis> command, which is fully described in <link
          linkend="HDRWQ593">To display the users in the UserList file</link>. <programlisting>
   % <emphasis role="bold">bos listusers</emphasis> &lt;<replaceable>machine name</replaceable>&gt;
</programlisting></para>
        </listitem>

        <listitem>
          <para><anchor id="LIWQ364" />Issue the <emphasis role="bold">bos listkeys</emphasis> command to display the key version
          numbers that are already in use, as a first step in choosing the key version number for the new key. <programlisting>
   % <emphasis role="bold">bos listkeys</emphasis> &lt;<replaceable>machine name</replaceable>&gt;
</programlisting></para>

          <para>where <variablelist>
              <varlistentry>
                <term><emphasis role="bold">listk</emphasis></term>

                <listitem>
                  <para>Is the shortest acceptable abbreviation of <emphasis role="bold">listkeys</emphasis>.</para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><emphasis role="bold">machine name</emphasis></term>

                <listitem>
                  <para>Names any file server machine.</para>
                </listitem>
              </varlistentry>
            </variablelist></para>
        </listitem>

        <listitem>
          <para><anchor id="LIWQ365" />Choose a key version number for the new key, based on the output from Step <link
          linkend="LIWQ364">2</link> and the following requirements: <itemizedlist>
              <listitem>
                <para>A key version number must be an integer between 0 (zero) and 255 to comply with Kerberos standards. It is
                simplest if you keep your key version numbers in sequence by choosing a key version number one greater than the
                largest existing one.</para>
              </listitem>

              <listitem>
                <para>Do not reuse a key version number currently found in the <emphasis role="bold">KeyFile</emphasis> file,
                particularly if it is also the one in the Authentication Database <emphasis role="bold">afs</emphasis> entry. Client
                processes possibly still have tickets sealed with the key that originally had that key version number, but the
                server processes start using the new key marked with that key version number. Because the keys do not match, the
                server processes refuse requests from clients who hold legitimate tokens.</para>
              </listitem>
            </itemizedlist></para>

          <indexterm>
            <primary>bos commands</primary>

            <secondary>addkey</secondary>

            <tertiary>basic instructions</tertiary>
          </indexterm>

          <indexterm>
            <primary>commands</primary>

            <secondary>bos addkey</secondary>
          </indexterm>
        </listitem>

        <listitem>
          <para><anchor id="LIWQ366" />Issue the <emphasis role="bold">bos addkey</emphasis> command to create a new AFS server
          encryption key in the <emphasis role="bold">KeyFile</emphasis> file.</para>

          <para>If you run the United States edition of AFS and use the Update Server to distribute the contents of the system
          control machine's <emphasis role="bold">/usr/afs/etc</emphasis> directory, substitute the system control machine for the
          machine name argument. (If you have forgotten which machine is the system control machine, see <link linkend="HDRWQ96">To
          locate the system control machine</link>.)</para>

          <para>If you run the international edition of AFS or do not use the Update Server, repeat the <emphasis role="bold">bos
          addkey</emphasis> command, substituting each server machine in your cell for the machine name argument in turn.</para>

          <para>To avoid visible echoing of the string that corresponds to the new key, omit the <emphasis
          role="bold">-key</emphasis> argument from the command line; instead enter the string at the prompts that appear when you
          omit it, as shown in the following syntax specification.</para>

          <programlisting>
   % <emphasis role="bold">bos addkey  -server</emphasis> &lt;<replaceable>machine name</replaceable>&gt; <emphasis role="bold">-kvno</emphasis> &lt;<replaceable>key version number</replaceable>&gt;
   input key: &lt;<replaceable>afs_password</replaceable>&gt;
   Retype input key: &lt;<replaceable>afs_password</replaceable>&gt;
</programlisting>

          <para>where <variablelist>
              <varlistentry>
                <term><emphasis role="bold">addk</emphasis></term>

                <listitem>
                  <para>Is the shortest acceptable abbreviation of <emphasis role="bold">addkey</emphasis>.</para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><emphasis role="bold">-server</emphasis></term>

                <listitem>
                  <para>Names the cell's system control machine if you are using the Update Server, or each server machine in turn
                  if you are not.</para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><emphasis role="bold">-kvno</emphasis></term>

                <listitem>
                  <para>Specifies the new key's key version number as an integer from the range 0 (zero) through 255.</para>

                  <para>Remember the number. You need to use it again in Step <link linkend="LIWQ367">6</link>. If you are using the
                  international edition of AFS, be sure to type the same number each time you issue this command.</para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><emphasis role="bold">afs_password</emphasis></term>

                <listitem>
                  <para>Is a character string similar to a user password, of any length from one to about 1,000 characters. To
                  improve security, include nonalphabetic characters and make the string as long as is practical (you need to type
                  it only in this step and in Step <link linkend="LIWQ367">6</link>). If you are using the international edition of
                  AFS, be sure to type the same string each time you issue this command.</para>

                  <para>Do not enter an octal string directly. The BOS Server scrambles the character string into an octal string
                  appropriate for use as an encryption key before recording it in the <emphasis role="bold">KeyFile</emphasis>
                  file.</para>
                </listitem>
              </varlistentry>
            </variablelist></para>
        </listitem>

        <listitem>
          <para>If you are using the Update Server, wait for a few minutes while the Update Server distributes the new <emphasis
          role="bold">KeyFile</emphasis> file to all server machines. The maximum necessary waiting period is the largest value
          provided for the <emphasis role="bold">-t</emphasis> argument to the <emphasis role="bold">upclientetc</emphasis>
          process's initialization command used on any of the server machines; the default time is five minutes.</para>

          <para>To be certain that all machines have the same <emphasis role="bold">KeyFile</emphasis> file, issue the <emphasis
          role="bold">bos listkeys</emphasis> command for every file server machine and verify that the checksum for the new key is
          the same on all machines.</para>

          <programlisting>
   % <emphasis role="bold">bos listkeys</emphasis> &lt;<replaceable>machine name</replaceable>&gt;
</programlisting>

          <para>If you are not using the Update Server, try to complete Step <link linkend="LIWQ366">4</link> within five
          minutes.</para>

          <indexterm>
            <primary>kas commands</primary>

            <secondary>setpassword</secondary>
          </indexterm>

          <indexterm>
            <primary>commands</primary>

            <secondary>kas setpassword</secondary>
          </indexterm>
        </listitem>

        <listitem>
          <para><anchor id="LIWQ367" />Issue the <emphasis role="bold">kas setpassword</emphasis> command to enter the same key in
          the <emphasis role="bold">afs</emphasis> entry in the Authentication Database.</para>

          <para>The Authentication Server performs its own authentication rather than accepting your existing AFS token. By default,
          it authenticates your local (UNIX) identity, which possibly does not correspond to an AFS-privileged administrator.
          Include the <emphasis role="bold">-admin</emphasis> argument to name an identity that has the
          <computeroutput>ADMIN</computeroutput> flag on its Authentication Database entry. To verify that an entry has the flag,
          issue the <emphasis role="bold">kas examine</emphasis> command as described in <link linkend="HDRWQ590">To check if the
          ADMIN flag is set</link>.</para>

          <programlisting>
   % <emphasis role="bold">kas setpassword -name afs -kvno</emphasis> &lt;<replaceable>kvno</replaceable>&gt;  \
                     <emphasis role="bold">-admin</emphasis>  &lt;<replaceable>admin principal to use for authentication</replaceable>&gt;  
   Administrator's (admin_user) password: &lt;<replaceable>admin_password</replaceable>&gt;
   new_password: afs_password
   Verifying, please re-enter new_password: &lt;<replaceable>admin_password</replaceable>&gt;
</programlisting>

          <para>where <variablelist>
              <varlistentry>
                <term><emphasis role="bold">sp</emphasis></term>

                <listitem>
                  <para>Is an acceptable alias for <emphasis role="bold">setpassword</emphasis> (<emphasis
                  role="bold">setp</emphasis> is the shortest acceptable abbreviation).</para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><emphasis role="bold">-name afs</emphasis></term>

                <listitem>
                  <para>Creates the new key in the <emphasis role="bold">afs</emphasis> entry.</para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><emphasis role="bold">-kvno</emphasis></term>

                <listitem>
                  <para>Specifies the same key version number as in Step <link linkend="LIWQ366">4</link>.</para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><emphasis role="bold">-admin</emphasis></term>

                <listitem>
                  <para>Names an administrative account with the <computeroutput>ADMIN</computeroutput> flag on its Authentication
                  Database entry, such as <emphasis role="bold">admin</emphasis>. The password prompt echoes it as admin_user. Enter
                  the appropriate password as admin_password.</para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><emphasis role="bold">afs_password</emphasis></term>

                <listitem>
                  <para>Is the same character string you entered in Step <link linkend="LIWQ366">4</link>.</para>
                </listitem>
              </varlistentry>
            </variablelist></para>
        </listitem>

        <listitem>
          <para><emphasis role="bold">(Optional.)</emphasis> If you want to verify that the keys you just created in the <emphasis
          role="bold">KeyFile</emphasis> file and the Authentication Database <emphasis role="bold">afs</emphasis> entry are
          identical and have the same key version number, follow the instructions in <link linkend="HDRWQ359">Displaying Server
          Encryption Keys</link>.</para>
        </listitem>

        <listitem>
          <para>Issue the <emphasis role="bold">bos restart</emphasis> command to restart the database server processes on all
          database server machines. This forces them to start using the key in the <emphasis role="bold">KeyFile</emphasis> file
          that currently has the highest key version number.</para>

          <para>Repeat this command in quick succession for each database server machine, starting with the machine that has the
          lowest IP address.</para>

          <programlisting>
   % <emphasis role="bold">bos restart</emphasis>  &lt;<replaceable>machine name</replaceable>&gt; <emphasis role="bold">buserver kaserver ptserver vlserver</emphasis>
</programlisting>

          <para>where <variablelist>
              <varlistentry>
                <term><emphasis role="bold">res</emphasis></term>

                <listitem>
                  <para>Is the shortest acceptable abbreviation of <emphasis role="bold">restart</emphasis>.</para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><emphasis role="bold">machine name</emphasis></term>

                <listitem>
                  <para>Names each database server machine in turn.</para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><emphasis role="bold">buserver kaserver ptserver vlserver</emphasis></term>

                <listitem>
                  <para>Designates the Backup Server, Authentication Server, Protection Server, and Volume Location (VL) Server,
                  respectively.</para>
                </listitem>
              </varlistentry>
            </variablelist></para>
        </listitem>
      </orderedlist>
    </sect2>
  </sect1>

  <sect1 id="HDRWQ368">
    <title>Removing Server Encryption Keys</title>

    <indexterm>
      <primary>removing</primary>

      <secondary>server encryption key from KeyFile file</secondary>
    </indexterm>

    <indexterm>
      <primary>server encryption key</primary>

      <secondary>removing from KeyFile file</secondary>
    </indexterm>

    <indexterm>
      <primary>KeyFile file</primary>

      <secondary>removing server encryption key</secondary>
    </indexterm>

    <para>You can periodically remove old keys from the <emphasis role="bold">/usr/afs/etc/KeyFile</emphasis> file to keep it to a
    reasonable size. To avoid disturbing cell functioning, do not remove an old key until all tokens sealed with the key and held by
    users or client processes have expired. After adding a new key, wait to remove old keys at least as long as the longest token
    lifetime you use in your cell. For Authentication Database user entries created under AFS version 3.1 or higher, the default
    token lifetime is 25 hours; for entries created under AFS version 3.0, it is 100 hours.</para>

    <para>There is no command for removing the key from the <emphasis role="bold">afs</emphasis> entry in the Authentication
    Database, because the key field in that entry must never be empty. Use the <emphasis role="bold">kas setpassword</emphasis>
    command to replace the <emphasis role="bold">afs</emphasis> key, but only as part of the complete procedure detailed in <link
    linkend="HDRWQ363">To add a new server encryption key</link>.</para>

    <para>Never remove from the <emphasis role="bold">KeyFile</emphasis> file the key that is currently in the <emphasis
    role="bold">afs</emphasis> entry in the Authentication Database. AFS server processes become unable to decrypt the tickets that
    clients present to them.</para>

    <sect2 id="HDRWQ369">
      <title>To remove a key from the KeyFile file</title>

      <orderedlist>
        <listitem>
          <para>Verify that you are authenticated as a user listed in the <emphasis role="bold">/usr/afs/etc/UserList</emphasis>
          file. If necessary, issue the <emphasis role="bold">bos listusers</emphasis> command, which is fully described in <link
          linkend="HDRWQ593">To display the users in the UserList file</link>. <programlisting>
   % <emphasis role="bold">bos listusers</emphasis> &lt;<replaceable>machine name</replaceable>&gt;
</programlisting></para>
        </listitem>

        <listitem>
          <para>Issue the <emphasis role="bold">bos listkeys</emphasis> command to display the key version number of each key you
          want to remove. The output also reveals whether it has been at least 25 hours since a new key was placed in the <emphasis
          role="bold">KeyFile</emphasis> file. For complete instructions for the <emphasis role="bold">bos listkeys</emphasis>
          command, see <link linkend="HDRWQ360">To display the KeyFile file</link>. <programlisting>
   % <emphasis role="bold">bos listkeys</emphasis> &lt;<replaceable>machine name</replaceable>&gt;
</programlisting></para>
        </listitem>

        <listitem>
          <para>Issue the <emphasis role="bold">kas examine</emphasis> command to verify that the key currently in the
          Authentication Database's <emphasis role="bold">afs</emphasis> entry does not have the same key version number as any of
          the keys you are removing from the <emphasis role="bold">KeyFile</emphasis> file. For detailed instructions for the
          <emphasis role="bold">kas examine</emphasis> command, see <link linkend="HDRWQ361">To display the afs key from the
          Authentication Database</link>. <programlisting>
   % <emphasis role="bold">kas examine afs  -admin</emphasis> &lt;<replaceable>admin principal to use for authentication</replaceable>&gt;  
   Administrator's (admin_user) password: &lt;<replaceable>admin_password</replaceable>&gt;
</programlisting></para>

          <indexterm>
            <primary>commands</primary>

            <secondary>bos removekey</secondary>
          </indexterm>

          <indexterm>
            <primary>bos commands</primary>

            <secondary>removekey</secondary>
          </indexterm>
        </listitem>

        <listitem>
          <para>Issue the <emphasis role="bold">bos removekey</emphasis> command to remove one or more server encryption keys from
          the <emphasis role="bold">KeyFile</emphasis> file.</para>

          <para>If you run the United States edition of AFS and use the Update Server to distribute the contents of the system
          control machine's <emphasis role="bold">/usr/afs/etc</emphasis> directory, substitute the system control machine for the
          machine name argument. (If you have forgotten which machine is the system control machine, see <link linkend="HDRWQ96">To
          locate the system control machine</link>.)</para>

          <para>If you run the international edition of AFS or do not use the Update Server, repeat the <emphasis role="bold">bos
          removekey</emphasis> command, substituting each server machine in your cell for the machine name argument in turn.</para>

          <programlisting>
   % <emphasis role="bold">bos removekey</emphasis> &lt;<replaceable>machine name</replaceable>&gt; &lt;<replaceable>key version number</replaceable>&gt;
</programlisting>

          <para>where <variablelist>
              <varlistentry>
                <term><emphasis role="bold">removek</emphasis></term>

                <listitem>
                  <para>Is the shortest acceptable abbreviation of <emphasis role="bold">removekey</emphasis>.</para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><emphasis role="bold">machine name</emphasis></term>

                <listitem>
                  <para>Names the cell's system control machine if you are using the Update Server, or each server machine in turn
                  if you are not.</para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><emphasis role="bold">key version number</emphasis></term>

                <listitem>
                  <para>Specifies the key version number of each key to remove.</para>
                </listitem>
              </varlistentry>
            </variablelist></para>
        </listitem>
      </orderedlist>
    </sect2>
  </sect1>

  <sect1 id="HDRWQ370">
    <title>Handling Server Encryption Key Emergencies</title>

    <indexterm>
      <primary>emergency</primary>

      <secondary>server encryption keys mismatched</secondary>
    </indexterm>

    <indexterm>
      <primary>server encryption key</primary>

      <secondary>emergency need to replace</secondary>
    </indexterm>

    <indexterm>
      <primary>mutual authentication</primary>

      <secondary>failure due to mismatched keys</secondary>
    </indexterm>

    <indexterm>
      <primary>Ubik</primary>

      <secondary>failure due to mismatched server encryption keys</secondary>
    </indexterm>

    <indexterm>
      <primary>handling</primary>

      <secondary>server encryption key emergency</secondary>
    </indexterm>

    <para>In rare circumstances, the AFS server processes can become unable to decrypt the server tickets that clients or peer
    server processes are presenting. Activity in your cell can come to a halt, because the server processes believe that the tickets
    are forged or expired, and refuse to execute any actions. This can happen on one machine or several; the effect is more serious
    when more machines are involved.</para>

    <para>One common cause of server encryption key problems is that the client's ticket is encrypted with a key that the server
    process does not know. Usually this means that the <emphasis role="bold">/usr/afs/etc/KeyFile</emphasis> on the server machine
    does not include the key in the <emphasis role="bold">afs</emphasis> Authentication Database entry, which the Authentication
    Server's Ticket Granting Service (TGS) module is using to encrypt server tickets.</para>

    <para>Another possibility is that the <emphasis role="bold">KeyFile</emphasis> files on different machines do not contain the
    same keys. In this case, communications among server processes themselves become impossible. For instance, AFS's replicated
    database mechanism (Ubik) breaks down if the instances of a database server process on the different database server machines
    are not using the same key.</para>

    <para>The appearance of the following error message when you direct a <emphasis role="bold">bos</emphasis> command to a file
    server machine in the local cell is one possible symptom of server encryption key mismatch. (Note, however, that you can also
    get this message if you forget to include the <emphasis role="bold">-cell</emphasis> argument when directing the <emphasis
    role="bold">bos</emphasis> command to a file server machine in a foreign cell.)</para>

    <programlisting>
   bos: failed to contact host's bosserver (security object was passed a bad ticket).
</programlisting>

    <para>The solution to server encryption key emergencies is to put a new AFS server encryption key in both the Authentication
    Database and the <emphasis role="bold">KeyFile</emphasis> file on every server machine, so that the TGS and all server processes
    again share the same key.</para>

    <para>Handling key emergencies requires some unusual actions. The reasons for these actions are explained in the following
    sections; the actual procedures appear in the subsequent instructions.</para>

    <sect2 id="HDRWQ371">
      <title>Prevent Mutual Authentication</title>

      <para>It is necessary to prevent the server processes from trying to mutually authenticate with you as you deal with a key
      emergency, because they possibly cannot decrypt your token. When you do not mutually authenticate, the server processes assign
      you the identity <emphasis role="bold">anonymous</emphasis>. To prevent mutual authentication, use the <emphasis
      role="bold">unlog</emphasis> command to discard your tokens and include the <emphasis role="bold">-noauth</emphasis> flag on
      every command where it is available.</para>
    </sect2>

    <sect2 id="Header_423">
      <title>Disable Authorization Checking by Hand</title>

      <para>Because the server processes recognize you as the user <emphasis role="bold">anonymous</emphasis> when you do not
      mutually authenticate, you must turn off authorization checking. Only with authorization checking disabled do the server
      processes allow the <emphasis role="bold">anonymous</emphasis> user to perform privileged actions such as key creation.</para>

      <para>In an emergency, disable authorization checking by creating the file <emphasis
      role="bold">/usr/afs/local/NoAuth</emphasis> by hand. In normal circumstances, use the <emphasis role="bold">bos
      setauth</emphasis> command instead.</para>
    </sect2>

    <sect2 id="Header_424">
      <title>Work Quickly on Each Machine</title>

      <para>Disabling authorization checking is a serious security exposure, because server processes on the affected machine
      perform any action for anyone. Disable authorization checking only for as long as necessary, completing all steps in an
      uninterrupted session and as quickly as possible.</para>
    </sect2>

    <sect2 id="Header_425">
      <title>Work at the Console</title>

      <para>Working at the console of each server machine on which you disable authorization checking ensures that no one else logs
      onto the console while you are working there. It does not prevent others from connecting to the machine remotely (using the
      <emphasis role="bold">telnet</emphasis> program, for example), which is why it is important to work quickly. The only way to
      ensure complete security is to disable network traffic, which is not a viable option in many environments. You can improve
      security in general by limiting the number of people who can connect remotely to your server machines at any time, as
      recommended in <link linkend="HDRWQ74">Improving Security in Your Cell</link>.</para>
    </sect2>

    <sect2 id="HDRWQ372">
      <title>Change Individual KeyFile Files</title>

      <para>If you use the Update Server to distribute the contents of the <emphasis role="bold">/usr/afs/etc</emphasis> directory,
      an emergency is the only time when it is appropriate to change the <emphasis role="bold">KeyFile</emphasis> file on individual
      machines instead. Updating each machine's file is necessary because mismatched keys can prevent the system control machine's
      <emphasis role="bold">upserver</emphasis> process from mutually authenticating with <emphasis
      role="bold">upclientetc</emphasis> processes on other server machines, in which case the <emphasis
      role="bold">upserver</emphasis> process refuses to distribute its <emphasis role="bold">KeyFile</emphasis> file to
      them.</para>

      <para>Even if it appears that the Update Server is working correctly, the only way to verify that is to change the key on the
      system control machine and wait the standard delay period to see if the <emphasis role="bold">upclientetc</emphasis> processes
      retrieve the key. During an emergency, it does not usually make sense to wait the standard delay period. It is more efficient
      simply to update the file on each server machine separately. Also, even if the Update Server can distribute the file
      correctly, other processes can have trouble because of mismatched keys. The following instructions add the new key file on the
      system control machine first. If the Update Server is working, then it is distributing the same change as you are making on
      each server machine individually.</para>

      <para>If your cell does not use the Update Server, or uses the international edition of AFS, you always change keys on server
      machines individually. The following instructions are also appropriate for you.</para>
    </sect2>

    <sect2 id="Header_427">
      <title>Two Component Procedures</title>

      <para>There are two subprocedures used frequently in the following instructions: disabling authorization checking and
      reenabling it. For the sake of clarity, the procedures are detailed here; the instructions refer to them as necessary.</para>

      <sect3 id="HDRWQ373">
        <title>Disabling Authorization Checking in an Emergency</title>

        <orderedlist>
          <listitem>
            <para>Become the local superuser <emphasis role="bold">root</emphasis> on the machine, if you are not already, by
            issuing the <emphasis role="bold">su</emphasis> command. <programlisting>
   % <emphasis role="bold">su root</emphasis>
   Password: &lt;<replaceable>root_password</replaceable>&gt;
</programlisting></para>

            <indexterm>
              <primary>NoAuth file</primary>

              <secondary>creating in emergencies</secondary>
            </indexterm>
          </listitem>

          <listitem>
            <para><anchor id="LIWQ374" />Create the file <emphasis role="bold">/usr/afs/local/NoAuth</emphasis> to disable
            authorization checking. <programlisting>
   # <emphasis role="bold">touch /usr/afs/local/NoAuth</emphasis>
</programlisting></para>

            <indexterm>
              <primary>unlog command</primary>

              <secondary>when handling key emergency</secondary>
            </indexterm>
          </listitem>

          <listitem>
            <para>Discard your tokens, in case they were sealed with an incompatible key, which can prevent some commands from
            executing. <programlisting>
   # <emphasis role="bold">unlog</emphasis>
</programlisting></para>
          </listitem>
        </orderedlist>
      </sect3>

      <sect3 id="HDRWQ375">
        <title>Reenabling Authorization Checking in an Emergency</title>

        <orderedlist>
          <listitem>
            <para>Become the local superuser <emphasis role="bold">root</emphasis> on the machine, if you are not already, by
            issuing the <emphasis role="bold">su</emphasis> command. <programlisting>
   % <emphasis role="bold">su root</emphasis>
   Password: &lt;<replaceable>root_password</replaceable>&gt;
</programlisting></para>
          </listitem>

          <listitem>
            <para>Remove the <emphasis role="bold">/usr/afs/local/NoAuth</emphasis> file. <programlisting>
   # <emphasis role="bold">rm /usr/afs/local/NoAuth</emphasis>
</programlisting></para>

            <indexterm>
              <primary>klog command</primary>

              <secondary>when handling key emergency</secondary>
            </indexterm>
          </listitem>

          <listitem>
            <para>Authenticate as an administrative identity that belongs to the <emphasis
            role="bold">system:administrators</emphasis> group and is listed in the <emphasis
            role="bold">/usr/afs/etc/UserList</emphasis> file. <programlisting>
   # <emphasis role="bold">klog</emphasis> &lt;<replaceable>admin_user</replaceable>&gt;
   Password: &lt;<replaceable>admin_password</replaceable>&gt;
</programlisting></para>
          </listitem>

          <listitem>
            <para>If appropriate, log out from the console (or close the remote connection you are using), after issuing the
            <emphasis role="bold">unlog</emphasis> command to destroy your tokens.</para>
          </listitem>
        </orderedlist>
      </sect3>
    </sect2>

    <sect2 id="Header_430">
      <title>To create a new server encryption key in emergencies</title>

      <orderedlist>
        <listitem>
          <para><anchor id="LIWQ376" /><emphasis role="bold">On the system control machine</emphasis>, disable authorization
          checking as instructed in <link linkend="HDRWQ373">Disabling Authorization Checking in an Emergency</link>.</para>
        </listitem>

        <listitem>
          <para><anchor id="LIWQ377" />Issue the <emphasis role="bold">bos listkeys</emphasis> command to display the key version
          numbers already in use in the <emphasis role="bold">KeyFile</emphasis> file, as a first step in choosing the new key's key
          version number. <programlisting>
   # <emphasis role="bold">bos listkeys</emphasis> &lt;<replaceable>machine name</replaceable>&gt; <emphasis role="bold">-noauth</emphasis>
</programlisting></para>

          <para>where <variablelist>
              <varlistentry>
                <term><emphasis role="bold">listk</emphasis></term>

                <listitem>
                  <para>Is the shortest acceptable abbreviation of <emphasis role="bold">listkeys</emphasis>.</para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><emphasis role="bold">machine name</emphasis></term>

                <listitem>
                  <para>Specifies a file server machine.</para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><emphasis role="bold">-noauth</emphasis></term>

                <listitem>
                  <para>Bypasses mutual authentication with the BOS Server. Include it in case the key emergency is preventing
                  successful mutual authentication.</para>
                </listitem>
              </varlistentry>
            </variablelist></para>
        </listitem>

        <listitem>
          <para><anchor id="LIWQ378" />Choose a key version number for the new key, based on what you learned in Step <link
          linkend="LIWQ377">2</link> plus the following requirements: <itemizedlist>
              <listitem>
                <para>It is best to keep your key version numbers in sequence by choosing a key version number one greater than the
                largest existing one.</para>
              </listitem>

              <listitem>
                <para>Key version numbers must be integers between 0 and 255 to comply with Kerberos standards.</para>
              </listitem>

              <listitem>
                <para>Do not reuse a key version number currently listed in the <emphasis role="bold">KeyFile</emphasis>
                file.</para>
              </listitem>
            </itemizedlist></para>

          <indexterm>
            <primary>bos commands</primary>

            <secondary>addkey</secondary>

            <tertiary>when handling key emergency</tertiary>
          </indexterm>
        </listitem>

        <listitem>
          <para><anchor id="LIWQ379" /><emphasis role="bold">On the system control machine</emphasis>, issue the <emphasis
          role="bold">bos addkey</emphasis> command to create a new AFS server encryption key in the <emphasis
          role="bold">KeyFile</emphasis> file. <programlisting>
   # <emphasis role="bold">bos addkey</emphasis> &lt;<replaceable>machine name</replaceable>&gt; <emphasis role="bold">-kvno</emphasis> &lt;<replaceable>key version number</replaceable>&gt; <emphasis
                role="bold">-noauth</emphasis>
   input key: &lt;<replaceable>afs_password</replaceable>&gt;
   Retype input key: &lt;<replaceable>afs_password</replaceable>&gt;
</programlisting></para>

          <para>where <variablelist>
              <varlistentry>
                <term><emphasis role="bold">addk</emphasis></term>

                <listitem>
                  <para>Is the shortest acceptable abbreviation of <emphasis role="bold">addkey</emphasis>.</para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><emphasis role="bold">machine name</emphasis></term>

                <listitem>
                  <para>Names the file server machine on which to define the new key in the <emphasis role="bold">KeyFile</emphasis>
                  file.</para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><emphasis role="bold">-kvno</emphasis></term>

                <listitem>
                  <para>Specifies the key version number you chose in Step <link linkend="LIWQ378">3</link>, an integer in the range
                  0 (zero) through 255. You must specify the same number in Steps <link linkend="LIWQ382">7</link>, <link
                  linkend="LIWQ383">8</link>, and <link linkend="LIWQ386">13</link>.</para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><emphasis role="bold">-noauth</emphasis></term>

                <listitem>
                  <para>Bypasses mutual authentication with the BOS Server. Include it in case the key emergency is preventing
                  successful mutual authentication.</para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><emphasis role="bold">afs_password</emphasis></term>

                <listitem>
                  <para>Is a character string similar to a user password, of any length from one to about 1,000 characters. To
                  improve security, make the string as long as is practical, and include nonalphabetic characters.</para>

                  <para>Do not type an octal string directly. The BOS Server scrambles the character string into an octal string
                  appropriate for use as an encryption key before recording it in the <emphasis role="bold">KeyFile</emphasis>
                  file.</para>

                  <para>Remember the string. You need to use it again in Steps <link linkend="LIWQ382">7</link>, <link
                  linkend="LIWQ383">8</link>, and <link linkend="LIWQ386">13</link>.</para>
                </listitem>
              </varlistentry>
            </variablelist></para>
        </listitem>

        <listitem>
          <para><anchor id="LIWQ380" /><emphasis role="bold">On every database server machine in your cell</emphasis> (other than
          the system control machine), disable authorization checking as instructed in <link linkend="HDRWQ373">Disabling
          Authorization Checking in an Emergency</link>. Do not repeat the procedure on the system control machine, if it is a
          database server machine, because you already disabled authorization checking in Step <link linkend="LIWQ376">1</link>. (If
          you need to learn which machines are database server machines, use the <emphasis role="bold">bos listhosts</emphasis>
          command as described in <link linkend="HDRWQ95">To locate database server machines</link>.)</para>
        </listitem>

        <listitem>
          <para><anchor id="LIWQ381" />Wait at least 90 seconds after finishing Step <link linkend="LIWQ380">5</link>, to allow each
          of the database server processes (the Authentication, Backup, Protection and Volume Location Servers) to finish electing a
          new sync site. Then issue the <emphasis role="bold">udebug</emphasis> command to verify that the election worked properly.
          Issue the following commands, substituting each database server machine's name for server machine in turn. Include the
          system control machine if it is a database server machine. <programlisting>
   # <emphasis role="bold">udebug</emphasis> &lt;<replaceable>server machine</replaceable>&gt; <emphasis role="bold">buserver</emphasis>
   # <emphasis role="bold">udebug</emphasis> &lt;<replaceable>server machine</replaceable>&gt; <emphasis role="bold">kaserver</emphasis>
   # <emphasis role="bold">udebug</emphasis> &lt;<replaceable>server machine</replaceable>&gt; <emphasis role="bold">ptserver</emphasis>
   # <emphasis role="bold">udebug</emphasis> &lt;<replaceable>server machine</replaceable>&gt; <emphasis role="bold">vlserver</emphasis>
</programlisting></para>

          <para>For each process, the output from all of the database server machines must agree on which one is the sync site for
          the process. It is not, however, necessary that the same machine serves as the sync site for each of the four processes.
          For each process, the output from only one machine must include the following string:</para>

          <programlisting>
   I am sync site ...
</programlisting>

          <para>The output on the other machines instead includes the following line</para>

          <programlisting>
   I am not sync site
</programlisting>

          <para>and a subsequent line that begins with the string <computeroutput>Sync host</computeroutput> and specifies the IP
          address of the machine claiming to be the sync site.</para>

          <para>If the output does not meet these requirements or seems abnormal in another way, contact AFS Product Support for
          assistance.</para>
        </listitem>

        <listitem>
          <para><anchor id="LIWQ382" /><emphasis role="bold">On every database server machine in your cell</emphasis> (other than
          the system control machine), issue the <emphasis role="bold">bos addkey</emphasis> command described in Step <link
          linkend="LIWQ379">4</link>. Be sure to use the same values for afs_password and kvno as you used in that step.</para>

          <indexterm>
            <primary>kas commands</primary>

            <secondary>setpassword , when handling key emergency</secondary>
          </indexterm>
        </listitem>

        <listitem>
          <para><anchor id="LIWQ383" />Issue the <emphasis role="bold">kas setpassword</emphasis> command to define the new key in
          the Authentication Database's <emphasis role="bold">afs</emphasis> entry. It must match the key you created in Step <link
          linkend="LIWQ379">4</link> and Step <link linkend="LIWQ382">7</link>. <programlisting>
   # <emphasis role="bold">kas setpassword  -name afs</emphasis>  <emphasis role="bold">-kvno</emphasis> &lt;<replaceable>key version number</replaceable>&gt; <emphasis
                role="bold">-noauth</emphasis>
   new_password: &lt;<replaceable>afs_password</replaceable>&gt;
   Verifying, please re-enter new_password: &lt;<replaceable>afs_password</replaceable>&gt;
</programlisting></para>

          <para>where <variablelist>
              <varlistentry>
                <term><emphasis role="bold">sp</emphasis></term>

                <listitem>
                  <para>Is an acceptable alias for <emphasis role="bold">setpassword</emphasis> (<emphasis
                  role="bold">setp</emphasis> is the shortest acceptable abbreviation).</para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><emphasis role="bold">-kvno</emphasis></term>

                <listitem>
                  <para>Is the same key version number you specified in Step <link linkend="LIWQ379">4</link>.</para>
                </listitem>
              </varlistentry>

              <varlistentry>
                <term><emphasis role="bold">afs_password</emphasis></term>

                <listitem>
                  <para>Is the same character string you specified as afs_password in Step <link linkend="LIWQ379">4</link>. It does
                  not echo visibly.</para>
                </listitem>
              </varlistentry>
            </variablelist></para>
        </listitem>

        <listitem>
          <para><anchor id="LIWQ384" /><emphasis role="bold">On every database server machine in your cell</emphasis> (including the
          system control machine if it is a database server machine), reenable authorization checking as instructed in <link
          linkend="HDRWQ375">Reenabling Authorization Checking in an Emergency</link>. If the system control machine is not a
          database server machine, do not perform this procedure until Step <link linkend="LIWQ385">11</link>.</para>
        </listitem>

        <listitem>
          <para>Repeat Step <link linkend="LIWQ381">6</link> to verify that each database server process has properly elected a sync
          site after being restarted in Step <link linkend="LIWQ384">9</link>.</para>
        </listitem>

        <listitem>
          <para><anchor id="LIWQ385" /><emphasis role="bold">On the system control machine</emphasis> (if it is not a database
          server machine), reenable authorization checking as instructed in <link linkend="HDRWQ375">Reenabling Authorization
          Checking in an Emergency</link>. If it is a database server machine, you already performed the procedure in Step <link
          linkend="LIWQ384">9</link>.</para>
        </listitem>

        <listitem>
          <para><emphasis role="bold">On all remaining (simple) file server machines</emphasis>, disable authorization checking as
          instructed in <link linkend="HDRWQ373">Disabling Authorization Checking in an Emergency</link>.</para>
        </listitem>

        <listitem>
          <para><anchor id="LIWQ386" /><emphasis role="bold">On all remaining (simple) file server machines</emphasis>, issue the
          <emphasis role="bold">bos addkey</emphasis> command described in Step <link linkend="LIWQ379">4</link>. Be sure to use the
          same values for afs_password and kvno as you used in that step.</para>
        </listitem>

        <listitem>
          <para><emphasis role="bold">On all remaining (simple) file server machines</emphasis>, reenable authorization checking as
          instructed in <link linkend="HDRWQ375">Reenabling Authorization Checking in an Emergency</link>.</para>
        </listitem>
      </orderedlist>
    </sect2>
  </sect1>
</chapter>