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From sl...@apache.org
Subject cvs commit: httpd-2.0/docs/manual/mod mod_ssl.xml perchild.xml worker.xml
Date Sun, 10 Mar 2002 04:34:21 GMT
slive       02/03/09 20:34:21

  Added:       docs/manual/mod mod_ssl.xml perchild.xml worker.xml
  Log:
  Another few xml files.  Only one or two left to go.
  
  Revision  Changes    Path
  1.1                  httpd-2.0/docs/manual/mod/mod_ssl.xml
  
  Index: mod_ssl.xml
  ===================================================================
  <?xml version="1.0"?>
  <!DOCTYPE modulesynopsis SYSTEM "../style/modulesynopsis.dtd">
  <?xml-stylesheet type="text/xsl" href="../style/manual.xsl"?>
  <modulesynopsis>
  
  <name>mod_ssl</name>
  <description>Strong cryptography using the Secure Sockets
  Layer (SSL) and Transport Layer Security (TLS) protocols</description>
  <status>Extension</status>
  <sourcefile>mod_ssl.c</sourcefile>
  <identifier>ssl_module</identifier>
  
  <summary>
  <p>This module provides SSL v2/v3 and TLS v1 support for the Apache
  HTTP Server.  It was contributed by Ralf S. Engeschall based on his
  mod_ssl project and originally derived from work by Ben Laurie.</p>
  
  <p>This module relies on <a href="http://www.openssl.org/">OpenSSL</a>
  to provide the cryptography engine.</p>
  
  <p>Further details, discussion, and examples are provided in the
  <a href="../ssl/">SSL documentation</a>.</p>
  </summary>
  
  <section id="ToC25"><title>Environment Variables</title>
  
  <p>This module provides a lot of SSL information as additional environment
  variables to the SSI and CGI namespace. The generated variables are listed in
  the table below. For backward compatibility the information can
  be made available under different names, too. Look in the <a
  href="../ssl/ssl_compat.html">Compatibility</a> chapter for details on the
  compatibility variables.</p>
  
  <div align="center">
  <a name="table4"></a>
  <table width="600" cellspacing="0" cellpadding="1" border="0" summary="">
  <caption align="bottom" id="sf">SSI/CGI Environment Variables</caption>
  <tr><td bgcolor="#cccccc">
  <table width="598" cellpadding="5" cellspacing="0" border="0" summary="">
  <tr><td valign="top" align="center" bgcolor="#ffffff">
  <table border="0" cellspacing="0" cellpadding="2" width="598" summary="">
  <tr id="H">
   <td><strong>Variable Name:</strong></td>
   <td><strong>Value Type:</strong></td>
   <td><strong>Description:</strong></td>
  </tr>
  <tr id="D"><td><code>HTTPS</code></td>                         <td>flag</td>      <td>HTTPS is being used.</td></tr>
  <tr id="H"><td><code>SSL_PROTOCOL</code></td>                  <td>string</td>    <td>The SSL protocol version (SSLv2, SSLv3, TLSv1)</td></tr>
  <tr id="H"><td><code>SSL_SESSION_ID</code></td>                <td>string</td>    <td>The hex-encoded SSL session id</td></tr>
  <tr id="D"><td><code>SSL_CIPHER</code></td>                    <td>string</td>    <td>The cipher specification name</td></tr>
  <tr id="D"><td><code>SSL_CIPHER_EXPORT</code></td>             <td>string</td>    <td><code>true</code> if cipher is an export cipher</td></tr>
  <tr id="H"><td><code>SSL_CIPHER_USEKEYSIZE</code></td>         <td>number</td>    <td>Number of cipher bits (actually used)</td></tr>
  <tr id="D"><td><code>SSL_CIPHER_ALGKEYSIZE</code></td>         <td>number</td>    <td>Number of cipher bits (possible)</td></tr>
  <tr id="H"><td><code>SSL_VERSION_INTERFACE</code></td>         <td>string</td>    <td>The mod_ssl program version</td></tr>
  <tr id="D"><td><code>SSL_VERSION_LIBRARY</code></td>           <td>string</td>    <td>The OpenSSL program version</td></tr>
  <tr id="H"><td><code>SSL_CLIENT_M_VERSION</code></td>          <td>string</td>    <td>The version of the client certificate</td></tr>
  <tr id="D"><td><code>SSL_CLIENT_M_SERIAL</code></td>           <td>string</td>    <td>The serial of the client certificate</td></tr>
  <tr id="H"><td><code>SSL_CLIENT_S_DN</code></td>               <td>string</td>    <td>Subject DN in client's certificate</td></tr>
  <tr id="D"><td><code>SSL_CLIENT_S_DN_</code><em>x509</em></td> <td>string</td>    <td>Component of client's Subject DN</td></tr>
  <tr id="H"><td><code>SSL_CLIENT_I_DN</code></td>               <td>string</td>    <td>Issuer DN of client's certificate</td></tr>
  <tr id="D"><td><code>SSL_CLIENT_I_DN_</code><em>x509</em></td> <td>string</td>    <td>Component of client's Issuer DN</td></tr>
  <tr id="H"><td><code>SSL_CLIENT_V_START</code></td>            <td>string</td>    <td>Validity of client's certificate (start time)</td></tr>
  <tr id="D"><td><code>SSL_CLIENT_V_END</code></td>              <td>string</td>    <td>Validity of client's certificate (end time)</td></tr>
  <tr id="H"><td><code>SSL_CLIENT_A_SIG</code></td>              <td>string</td>    <td>Algorithm used for the signature of client's certificate</td></tr>
  <tr id="D"><td><code>SSL_CLIENT_A_KEY</code></td>              <td>string</td>    <td>Algorithm used for the public key of client's certificate</td></tr>
  <tr id="H"><td><code>SSL_CLIENT_CERT</code></td>               <td>string</td>    <td>PEM-encoded client certificate</td></tr>
  <tr id="D"><td><code>SSL_CLIENT_CERT_CHAIN</code><em>n</em></td> <td>string</td>    <td>PEM-encoded certificates in client certificate chain</td></tr>
  <tr id="H"><td><code>SSL_CLIENT_VERIFY</code></td>             <td>string</td>    <td><code>NONE</code>, <code>SUCCESS</code>, <code>GENEROUS</code> or <code>FAILED:</code><em>reason</em></td></tr>
  <tr id="D"><td><code>SSL_SERVER_M_VERSION</code></td>          <td>string</td>    <td>The version of the server certificate</td></tr>
  <tr id="H"><td><code>SSL_SERVER_M_SERIAL</code></td>           <td>string</td>    <td>The serial of the server certificate</td></tr>
  <tr id="D"><td><code>SSL_SERVER_S_DN</code></td>               <td>string</td>    <td>Subject DN in server's certificate</td></tr>
  <tr id="H"><td><code>SSL_SERVER_S_DN_</code><em>x509</em></td> <td>string</td>    <td>Component of server's Subject DN</td></tr>
  <tr id="D"><td><code>SSL_SERVER_I_DN</code></td>               <td>string</td>    <td>Issuer DN of server's certificate</td></tr>
  <tr id="H"><td><code>SSL_SERVER_I_DN_</code><em>x509</em></td> <td>string</td>    <td>Component of server's Issuer DN</td></tr>
  <tr id="D"><td><code>SSL_SERVER_V_START</code></td>            <td>string</td>    <td>Validity of server's certificate (start time)</td></tr>
  <tr id="H"><td><code>SSL_SERVER_V_END</code></td>              <td>string</td>    <td>Validity of server's certificate (end time)</td></tr>
  <tr id="D"><td><code>SSL_SERVER_A_SIG</code></td>              <td>string</td>    <td>Algorithm used for the signature of server's certificate</td></tr>
  <tr id="H"><td><code>SSL_SERVER_A_KEY</code></td>              <td>string</td>    <td>Algorithm used for the public key of server's certificate</td></tr>
  <tr id="D"><td><code>SSL_SERVER_CERT</code></td>               <td>string</td>    <td>PEM-encoded server certificate</td></tr>
  </table>
  [ where <em>x509</em> is a component of a X.509 DN:
    <code>C,ST,L,O,OU,CN,T,I,G,S,D,UID,Email</code> ]
  </td>
  </tr></table>
  </td></tr></table>
  </div>
  </section>
  
  <section id="ToC26"><title>Custom Log Formats</title>
  
  <p>When <module>mod_ssl</module> is built into Apache or at least
  loaded (under DSO situation) additional functions exist for the <a
  href="../mod_log_config.html#formats">Custom Log Format</a> of 
  <module>mod_log_config</module>. First there is an
  additional ``<code>%{</code><em>varname</em><code>}x</code>''
  eXtension format function which can be used to expand any variables
  provided by any module, especially those provided by mod_ssl which can
  you find in the above table.</p>
  <p>
  For backward compatibility there is additionally a special
  ``<code>%{</code><em>name</em><code>}c</code>'' cryptography format function
  provided. Information about this function is provided in the <a
  href="../ssl/ssl_compat.html">Compatibility</a> chapter.</p>
  <p>
  Example:</p>
  <example>
  CustomLog logs/ssl_request_log \
            "%t %h %{SSL_PROTOCOL}x %{SSL_CIPHER}x \"%r\" %b"
  </example>
  </section>
  
  <directivesynopsis>
  <name>SSLPassPhraseDialog</name>
  <description>Type of pass phrase dialog for encrypted private 
  keys</description>
  <syntax>SSLPassPhraseDialog <em>type</em></syntax>
  <default>SSLPassPhraseDialog builtin</default>
  <contextlist><context>server config</context></contextlist>
  
  <usage>
  <p>
  When Apache starts up it has to read the various Certificate (see
  <directive module="mod_ssl">SSLCertificateFile</directive>) and
  Private Key (see <directive
  module="mod_ssl">SSLCertificateKeyFile</directive>) files of the
  SSL-enabled virtual servers. Because for security reasons the Private
  Key files are usually encrypted, mod_ssl needs to query the
  administrator for a Pass Phrase in order to decrypt those files. This
  query can be done in two ways which can be configured by
  <em>type</em>:</p>
  <ul>
  <li><code>builtin</code>
      <p>
      This is the default where an interactive terminal dialog occurs at startup
      time just before Apache detaches from the terminal. Here the administrator
      has to manually enter the Pass Phrase for each encrypted Private Key file.
      Because a lot of SSL-enabled virtual hosts can be configured, the
      following reuse-scheme is used to minimize the dialog: When a Private Key
      file is encrypted, all known Pass Phrases (at the beginning there are
      none, of course) are tried. If one of those known Pass Phrases succeeds no
      dialog pops up for this particular Private Key file. If none succeeded,
      another Pass Phrase is queried on the terminal and remembered for the next
      round (where it perhaps can be reused).</p>
      <p>
      This scheme allows mod_ssl to be maximally flexible (because for N encrypted
      Private Key files you <em>can</em> use N different Pass Phrases - but then
      you have to enter all of them, of course) while minimizing the terminal
      dialog (i.e. when you use a single Pass Phrase for all N Private Key files
      this Pass Phrase is queried only once).</p></li>
  
  <li><code>exec:/path/to/program</code>
      <p>
      Here an external program is configured which is called at startup for each
      encrypted Private Key file. It is called with two arguments (the first is
      of the form ``<code>servername:portnumber</code>'', the second is either
      ``<code>RSA</code>'' or ``<code>DSA</code>''), which indicate for which
      server and algorithm it has to print the corresponding Pass Phrase to
      <code>stdout</code>. The intent is that this external program first runs
      security checks to make sure that the system is not compromised by an
      attacker, and only when these checks were passed successfully it provides
      the Pass Phrase.</p>
      <p>
      Both these security checks, and the way the Pass Phrase is determined, can
      be as complex as you like. Mod_ssl just defines the interface: an
      executable program which provides the Pass Phrase on <code>stdout</code>.
      Nothing more or less! So, if you're really paranoid about security, here
      is your interface. Anything else has to be left as an exercise to the
      administrator, because local security requirements are so different.</p>
      <p>
      The reuse-algorithm above is used here, too. In other words: The external
      program is called only once per unique Pass Phrase.</p></li>
  </ul>
  <p>
  Example:</p>
  <example>
  SSLPassPhraseDialog exec:/usr/local/apache/sbin/pp-filter
  </example>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>SSLMutex</name>
  <description>Semaphore for internal mutual exclusion of 
  operations</description>
  <syntax>SSLMutex <em>type</em></syntax>
  <default>SSLMutex none</default>
  <contextlist><context>server config</context></contextlist>
  
  <usage>
  <p>
  This configures the SSL engine's semaphore (aka. lock) which is used for mutual
  exclusion of operations which have to be done in a synchronized way between the
  pre-forked Apache server processes. This directive can only be used in the
  global server context because it's only useful to have one global mutex.</p>
  <p>
  The following Mutex <em>types</em> are available:</p>
  <ul>
  <li><code>none</code>
      <p>
      This is the default where no Mutex is used at all. Use it at your own
      risk. But because currently the Mutex is mainly used for synchronizing
      write access to the SSL Session Cache you can live without it as long
      as you accept a sometimes garbled Session Cache. So it's not recommended
      to leave this the default. Instead configure a real Mutex.</p></li>
  <li><code>file:/path/to/mutex</code>
      <p>
      This is the portable and (under Unix) always provided Mutex variant where
      a physical (lock-)file is used as the Mutex. Always use a local disk
      filesystem for <code>/path/to/mutex</code> and never a file residing on a
      NFS- or AFS-filesystem. Note: Internally, the Process ID (PID) of the
      Apache parent process is automatically appended to
      <code>/path/to/mutex</code> to make it unique, so you don't have to worry
      about conflicts yourself. Notice that this type of mutex is not available
      under the Win32 environment. There you <em>have</em> to use the semaphore
      mutex.</p></li>
  <li><code>sem</code>
      <p>
      This is the most elegant but also most non-portable Mutex variant where a
      SysV IPC Semaphore (under Unix) and a Windows Mutex (under Win32) is used
      when possible. It is only available when the underlying platform
      supports it.</p></li>
  </ul>
  <example><title>Example</title>
  SSLMutex file:/usr/local/apache/logs/ssl_mutex
  </example>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>SSLRandomSeed</name>
  <description>Pseudo Random Number Generator (PRNG) seeding 
  source</description>
  <syntax>SSLRandomSeed <em>context</em> <em>source</em> 
  [<em>bytes</em>]</syntax>
  <contextlist><context>server config</context></contextlist>
  
  <usage>
  <p>
  This configures one or more sources for seeding the Pseudo Random Number
  Generator (PRNG) in OpenSSL at startup time (<em>context</em> is
  <code>startup</code>) and/or just before a new SSL connection is established
  (<em>context</em> is <code>connect</code>). This directive can only be used
  in the global server context because the PRNG is a global facility.</p>
  <p>
  The following <em>source</em> variants are available:</p>
  <ul>
  <li><code>builtin</code>
      <p> This is the always available builtin seeding source. It's usage
      consumes minimum CPU cycles under runtime and hence can be always used
      without drawbacks. The source used for seeding the PRNG contains of the
      current time, the current process id and (when applicable) a randomly
      choosen 1KB extract of the inter-process scoreboard structure of Apache.
      The drawback is that this is not really a strong source and at startup
      time (where the scoreboard is still not available) this source just
      produces a few bytes of entropy. So you should always, at least for the
      startup, use an additional seeding source.</p></li>
  <li><code>file:/path/to/source</code>
      <p>
      This variant uses an external file <code>/path/to/source</code> as the
      source for seeding the PRNG. When <em>bytes</em> is specified, only the
      first <em>bytes</em> number of bytes of the file form the entropy (and
      <em>bytes</em> is given to <code>/path/to/source</code> as the first
      argument). When <em>bytes</em> is not specified the whole file forms the
      entropy (and <code>0</code> is given to <code>/path/to/source</code> as
      the first argument). Use this especially at startup time, for instance
      with an available <code>/dev/random</code> and/or
      <code>/dev/urandom</code> devices (which usually exist on modern Unix
      derivates like FreeBSD and Linux).</p>
      <p>
      <em>But be careful</em>: Usually <code>/dev/random</code> provides only as
      much entropy data as it actually has, i.e. when you request 512 bytes of
      entropy, but the device currently has only 100 bytes available two things
      can happen: On some platforms you receive only the 100 bytes while on
      other platforms the read blocks until enough bytes are available (which
      can take a long time). Here using an existing <code>/dev/urandom</code> is
      better, because it never blocks and actually gives the amount of requested
      data. The drawback is just that the quality of the received data may not
      be the best.</p>
      <p>
      On some platforms like FreeBSD one can even control how the entropy is
      actually generated, i.e. by which system interrupts. More details one can
      find under <em>rndcontrol(8)</em> on those platforms. Alternatively, when
      your system lacks such a random device, you can use tool
      like <a href="http://www.lothar.com/tech/crypto/">EGD</a>
      (Entropy Gathering Daemon) and run it's client program with the
      <code>exec:/path/to/program/</code> variant (see below) or use
      <code>egd:/path/to/egd-socket</code> (see below).</p></li>
  
  <li><code>exec:/path/to/program</code>
      <p>
      This variant uses an external executable
      <code>/path/to/program</code> as the source for seeding the
      PRNG. When <em>bytes</em> is specified, only the first
      <em>bytes</em> number of bytes of its <code>stdout</code> contents
      form the entropy. When <em>bytes</em> is not specified, the
      entirety of the data produced on <code>stdout</code> form the
      entropy. Use this only at startup time when you need a very strong
      seeding with the help of an external program (for instance as in
      the example above with the <code>truerand</code> utility you can
      find in the mod_ssl distribution which is based on the AT&amp;T
      <em>truerand</em> library). Using this in the connection context
      slows down the server too dramatically, of course.  So usually you
      should avoid using external programs in that context.</p></li>
  <li><code>egd:/path/to/egd-socket</code> (Unix only)
      <p>
      This variant uses the Unix domain socket of the
      external Entropy Gathering Daemon (EGD) (see <a
      href="http://www.lothar.com/tech/crypto/">http://www.lothar.com/tech
      /crypto/</a>) to seed the PRNG. Use this if no random device exists
      on your platform.</p></li>
  </ul>
  <example><title>Example</title>
  SSLRandomSeed startup builtin<br />
  SSLRandomSeed startup file:/dev/random<br />
  SSLRandomSeed startup file:/dev/urandom 1024<br />
  SSLRandomSeed startup exec:/usr/local/bin/truerand 16<br />
  SSLRandomSeed connect builtin<br />
  SSLRandomSeed connect file:/dev/random<br />
  SSLRandomSeed connect file:/dev/urandom 1024<br />
  </example>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>SSLSessionCache</name>
  <description>Type of the global/inter-process SSL Session 
  Cache</description>
  <syntax>SSLSessionCache <em>type</em></syntax>
  <default>SSLSessionCache none</default>
  <contextlist><context>server config</context></contextlist>
  
  <usage>
  <p>
  This configures the storage type of the global/inter-process SSL Session
  Cache. This cache is an optional facility which speeds up parallel request
  processing. For requests to the same server process (via HTTP keep-alive),
  OpenSSL already caches the SSL session information locally. But because modern
  clients request inlined images and other data via parallel requests (usually
  up to four parallel requests are common) those requests are served by
  <em>different</em> pre-forked server processes. Here an inter-process cache
  helps to avoid unneccessary session handshakes.</p>
  <p>
  The following two storage <em>type</em>s are currently supported:</p>
  <ul>
  <li><code>none</code>
      <p>
      This is the default and just disables the global/inter-process Session
      Cache. There is no drawback in functionality, but a noticeable speed
      penalty can be observed.</p></li>
  <li><code>dbm:/path/to/datafile</code>
      <p>
      This makes use of a DBM hashfile on the local disk to synchronize the
      local OpenSSL memory caches of the server processes. The slight increase
      in I/O on the server results in a visible request speedup for your
      clients, so this type of storage is generally recommended.</p></li>
  <li><code>shm:/path/to/datafile</code>[<code>(</code><em>size</em><code>)</code>]
      <p>
      This makes use of a high-performance hash table (approx. <em>size</em> bytes
      in size) inside a shared memory segment in RAM (established via
      <code>/path/to/datafile</code>) to synchronize the local OpenSSL memory
      caches of the server processes. This storage type is not available on all
      platforms. See the mod_ssl <code>INSTALL</code> document for details on
      how to build Apache+EAPI with shared memory support.</p></li>
  </ul>
  <example><title>Examples</title>
  SSLSessionCache dbm:/usr/local/apache/logs/ssl_gcache_data<br />
  SSLSessionCache shm:/usr/local/apache/logs/ssl_gcache_data(512000)
  </example>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>SSLSessionCacheTimeout</name>
  <description>Number of seconds before an SSL session expires
  in the Session Cache</description>
  <syntax>SSLSessionCacheTimeout <em>seconds</em></syntax>
  <default>SSLSessionCacheTimeout 300</default>
  <contextlist><context>server config</context>
  <context>virtual host</context></contextlist>
  
  <usage>
  <p>
  This directive sets the timeout in seconds for the information stored in the
  global/inter-process SSL Session Cache and the OpenSSL internal memory cache.
  It can be set as low as 15 for testing, but should be set to higher
  values like 300 in real life.</p>
  <example><title>Example</title>
  SSLSessionCacheTimeout 600
  </example>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>SSLEngine</name>
  <description>SSL Engine Operation Switch</description>
  <syntax>SSLEngine on|off</syntax>
  <default>SSLEngine off</default>
  <contextlist><context>server config</context>
  <context>virtual host</context></contextlist>
  
  <usage>
  <p>
  This directive toggles the usage of the SSL/TLS Protocol Engine. This
  is usually used inside a <directive module="core"
  type="section">VirtualHost</directive> section to enable SSL/TLS for a
  particular virtual host. By default the SSL/TLS Protocol Engine is
  disabled for both the main server and all configured virtual hosts.</p>
  <example><title>Example</title>
  &lt;VirtualHost _default_:443&gt;<br />
  SSLEngine on<br />
  ...<br />
  &lt;/VirtualHost&gt;
  </example>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>SSLProtocol</name>
  <description>Configure usable SSL protocol flavors</description>
  <syntax>SSLProtocol [+|-]<em>protocol</em> ...</syntax>
  <default>SSLProtocol all</default>
  <contextlist><context>server config</context>
  <context>virtual host</context></contextlist>
  <override>Options</override>
  
  <usage><!-- XXX Why does this have an override and not .htaccess context? -->
  <p>
  This directive can be used to control the SSL protocol flavors mod_ssl should
  use when establishing its server environment. Clients then can only connect
  with one of the provided protocols.</p>
  <p>
  The available (case-insensitive) <em>protocol</em>s are:</p>
  <ul>
  <li><code>SSLv2</code>
      <p>
      This is the Secure Sockets Layer (SSL) protocol, version 2.0. It is the
      original SSL protocol as designed by Netscape Corporation.</p></li>
  
  <li><code>SSLv3</code>
      <p>
      This is the Secure Sockets Layer (SSL) protocol, version 3.0. It is the
      successor to SSLv2 and the currently (as of February 1999) de-facto
      standardized SSL protocol from Netscape Corporation. It's supported by
      almost all popular browsers.</p></li>
  
  <li><code>TLSv1</code>
      <p>
      This is the Transport Layer Security (TLS) protocol, version 1.0. It is the
      successor to SSLv3 and currently (as of February 1999) still under
      construction by the Internet Engineering Task Force (IETF). It's still
      not supported by any popular browsers.</p></li>
  
  <li><code>All</code>
      <p>
      This is a shortcut for ``<code>+SSLv2 +SSLv3 +TLSv1</code>'' and a
      convinient way for enabling all protocols except one when used in
      combination with the minus sign on a protocol as the example above 
      shows.</p></li>
  </ul>
  <example><title>Example</title>
  #   enable SSLv3 and TLSv1, but not SSLv2<br />
  SSLProtocol all -SSLv2
  </example>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>SSLCipherSuite</name>
  <description>Cipher Suite available for negotiation in SSL 
  handshake</description>
  <syntax>SSLCipherSuite <em>cipher-spec</em></syntax>
  <default>SSLCipherSuite ALL:!ADH:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP</default>
  <contextlist><context>server config</context>
  <context>virtual host</context>
  <context>directory</context>
  <context>.htaccess</context></contextlist>
  <override>AuthConfig</override>
  
  <usage>
  <p>
  This complex directive uses a colon-separated <em>cipher-spec</em> string
  consisting of OpenSSL cipher specifications to configure the Cipher Suite the
  client is permitted to negotiate in the SSL handshake phase. Notice that this
  directive can be used both in per-server and per-directory context. In
  per-server context it applies to the standard SSL handshake when a connection
  is established. In per-directory context it forces a SSL renegotation with the
  reconfigured Cipher Suite after the HTTP request was read but before the HTTP
  response is sent.</p>
  <p>
  An SSL cipher specification in <em>cipher-spec</em> is composed of 4 major
  attributes plus a few extra minor ones:</p>
  <ul>
  <li><em>Key Exchange Algorithm</em>:<br />
      RSA or Diffie-Hellman variants.
  </li>
  <li><em>Authentication Algorithm</em>:<br />
      RSA, Diffie-Hellman, DSS or none.
  </li>
  <li><em>Cipher/Encryption Algorithm</em>:<br />
      DES, Triple-DES, RC4, RC2, IDEA or none.
  </li>
  <li><em>MAC Digest Algorithm</em>:<br />
      MD5, SHA or SHA1.
  </li>
  </ul>
  <p>An SSL cipher can also be an export cipher and is either a SSLv2 or SSLv3/TLSv1
  cipher (here TLSv1 is equivalent to SSLv3). To specify which ciphers to use,
  one can either specify all the Ciphers, one at a time, or use aliases to
  specify the preference and order for the ciphers (see <a href="#table1">Table
  1</a>).</p>
  
  <div align="center">
  <a name="table1"></a>
  <table width="600" cellspacing="0" cellpadding="1" border="0" summary="">
  <caption align="bottom" id="sf">Table 1: OpenSSL Cipher Specification Tags</caption>
  <tr><td bgcolor="#cccccc">
  <table width="598" cellpadding="5" cellspacing="0" border="0" summary="">
  <tr><td valign="top" align="center" bgcolor="#ffffff">
  <table border="0" cellspacing="0" cellpadding="2" width="598" summary="">
  <tr id="D"><td><strong>Tag</strong></td> <td><strong>Description</strong></td></tr>
  <tr id="H"><td colspan="2"><em>Key Exchange Algorithm:</em></td></tr>
  <tr id="D"><td><code>kRSA</code></td>   <td>RSA key exchange</td></tr>
  <tr id="H"><td><code>kDHr</code></td>   <td>Diffie-Hellman key exchange with RSA key</td></tr>
  <tr id="D"><td><code>kDHd</code></td>   <td>Diffie-Hellman key exchange with DSA key</td></tr>
  <tr id="H"><td><code>kEDH</code></td>   <td>Ephemeral (temp.key) Diffie-Hellman key exchange (no cert)</td>   </tr>
  <tr id="H"><td colspan="2"><em>Authentication Algorithm:</em></td></tr>
  <tr id="D"><td><code>aNULL</code></td>  <td>No authentication</td></tr>
  <tr id="H"><td><code>aRSA</code></td>   <td>RSA authentication</td></tr>
  <tr id="D"><td><code>aDSS</code></td>   <td>DSS authentication</td> </tr>
  <tr id="H"><td><code>aDH</code></td>    <td>Diffie-Hellman authentication</td></tr>
  <tr id="D"><td colspan="2"><em>Cipher Encoding Algorithm:</em></td></tr>
  <tr id="H"><td><code>eNULL</code></td>  <td>No encoding</td>         </tr>
  <tr id="D"><td><code>DES</code></td>    <td>DES encoding</td>        </tr>
  <tr id="H"><td><code>3DES</code></td>   <td>Triple-DES encoding</td> </tr>
  <tr id="D"><td><code>RC4</code></td>    <td>RC4 encoding</td>       </tr>
  <tr id="H"><td><code>RC2</code></td>    <td>RC2 encoding</td>       </tr>
  <tr id="D"><td><code>IDEA</code></td>   <td>IDEA encoding</td>       </tr>
  <tr id="H"><td colspan="2"><em>MAC Digest Algorithm</em>:</td></tr>
  <tr id="D"><td><code>MD5</code></td>    <td>MD5 hash function</td></tr>
  <tr id="H"><td><code>SHA1</code></td>   <td>SHA1 hash function</td></tr>
  <tr id="D"><td><code>SHA</code></td>    <td>SHA hash function</td> </tr>
  <tr id="H"><td colspan="2"><em>Aliases:</em></td></tr>
  <tr id="D"><td><code>SSLv2</code></td>  <td>all SSL version 2.0 ciphers</td></tr>
  <tr id="H"><td><code>SSLv3</code></td>  <td>all SSL version 3.0 ciphers</td> </tr>
  <tr id="D"><td><code>TLSv1</code></td>  <td>all TLS version 1.0 ciphers</td> </tr>
  <tr id="H"><td><code>EXP</code></td>    <td>all export ciphers</td>  </tr>
  <tr id="D"><td><code>EXPORT40</code></td> <td>all 40-bit export ciphers only</td>  </tr>
  <tr id="H"><td><code>EXPORT56</code></td> <td>all 56-bit export ciphers only</td>  </tr>
  <tr id="D"><td><code>LOW</code></td>    <td>all low strength ciphers (no export, single DES)</td></tr>
  <tr id="H"><td><code>MEDIUM</code></td> <td>all ciphers with 128 bit encryption</td> </tr>
  <tr id="D"><td><code>HIGH</code></td>   <td>all ciphers using Triple-DES</td>     </tr>
  <tr id="H"><td><code>RSA</code></td>    <td>all ciphers using RSA key exchange</td> </tr>
  <tr id="D"><td><code>DH</code></td>     <td>all ciphers using Diffie-Hellman key exchange</td> </tr>
  <tr id="H"><td><code>EDH</code></td>    <td>all ciphers using Ephemeral Diffie-Hellman key exchange</td> </tr>
  <tr id="D"><td><code>ADH</code></td>    <td>all ciphers using Anonymous Diffie-Hellman key exchange</td> </tr>
  <tr id="H"><td><code>DSS</code></td>    <td>all ciphers using DSS authentication</td> </tr>
  <tr id="D"><td><code>NULL</code></td>   <td>all ciphers using no encryption</td> </tr>
  </table>
  </td>
  </tr></table>
  </td></tr></table>
  </div>
  <p>
  Now where this becomes interesting is that these can be put together
  to specify the order and ciphers you wish to use. To speed this up
  there are also aliases (<code>SSLv2, SSLv3, TLSv1, EXP, LOW, MEDIUM,
  HIGH</code>) for certain groups of ciphers. These tags can be joined
  together with prefixes to form the <em>cipher-spec</em>. Available
  prefixes are:</p>
  <ul>
  <li>none: add cipher to list</li>
  <li><code>+</code>: add ciphers to list and pull them to current location in list</li>
  <li><code>-</code>: remove cipher from list (can be added later again)</li>
  <li><code>!</code>: kill cipher from list completely (can <strong>not</strong> be added later again)</li>
  </ul>
  <p>A simpler way to look at all of this is to use the ``<code>openssl ciphers
  -v</code>'' command which provides a nice way to successively create the
  correct <em>cipher-spec</em> string. The default <em>cipher-spec</em> string
  is ``<code>ALL:!ADH:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP</code>'' which
  means the following: first, remove from consideration any ciphers that do not
  authenticate, i.e. for SSL only the Anonymous Diffie-Hellman ciphers. Next,
  use ciphers using RC4 and RSA. Next include the high, medium and then the low
  security ciphers. Finally <em>pull</em> all SSLv2 and export ciphers to the
  end of the list.</p>
  <example>
  <pre>
  $ openssl ciphers -v 'ALL:!ADH:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP'
  NULL-SHA                SSLv3 Kx=RSA      Au=RSA  Enc=None      Mac=SHA1
  NULL-MD5                SSLv3 Kx=RSA      Au=RSA  Enc=None      Mac=MD5
  EDH-RSA-DES-CBC3-SHA    SSLv3 Kx=DH       Au=RSA  Enc=3DES(168) Mac=SHA1
  ...                     ...               ...     ...           ...
  EXP-RC4-MD5             SSLv3 Kx=RSA(512) Au=RSA  Enc=RC4(40)   Mac=MD5  export
  EXP-RC2-CBC-MD5         SSLv2 Kx=RSA(512) Au=RSA  Enc=RC2(40)   Mac=MD5  export
  EXP-RC4-MD5             SSLv2 Kx=RSA(512) Au=RSA  Enc=RC4(40)   Mac=MD5  export
  </pre>
  </example>
  <p>The complete list of particular RSA &amp; DH ciphers for SSL is given in <a
  href="#table2">Table 2</a>.</p>
  <example><title>Example</title>
  SSLCipherSuite RSA:!EXP:!NULL:+HIGH:+MEDIUM:-LOW
  </example>
  <div align="center">
  <a name="table2"></a>
  <table width="600" cellspacing="0" cellpadding="1" border="0" summary="">
  <caption align="bottom" id="sf">Table 2: Particular SSL Ciphers</caption>
  <tr><td bgcolor="#cccccc">
  <table width="598" cellpadding="5" cellspacing="0" border="0" summary="">
  <tr><td valign="top" align="center" bgcolor="#ffffff">
  <table border="0" cellspacing="0" cellpadding="2" width="598" summary="">
  <tr id="D"><td><strong>Cipher-Tag</strong></td> <td><strong>Protocol</strong></td> <td><strong>Key Ex.</strong></td> <td><strong>Auth.</strong></td> <td><strong>Enc.</strong></td> <td><strong>MAC</strong></td> <td><strong>Type</strong></td> </tr>
  <tr id="H"><td colspan="7"><em>RSA Ciphers:</em></td></tr>
  <tr id="D"><td><code>DES-CBC3-SHA</code></td> <td>SSLv3</td> <td>RSA</td> <td>RSA</td> <td>3DES(168)</td> <td>SHA1</td> <td>&nbsp;</td> </tr>
  <tr id="H"><td><code>DES-CBC3-MD5</code></td> <td>SSLv2</td> <td>RSA</td> <td>RSA</td> <td>3DES(168)</td> <td>MD5</td> <td>&nbsp; </td> </tr>
  <tr id="D"><td><code>IDEA-CBC-SHA</code></td> <td>SSLv3</td> <td>RSA</td> <td>RSA</td> <td>IDEA(128)</td> <td>SHA1</td> <td>&nbsp;</td> </tr>
  <tr id="H"><td><code>RC4-SHA</code></td> <td>SSLv3</td> <td>RSA</td> <td>RSA</td> <td>RC4(128)</td> <td>SHA1</td> <td>&nbsp;</td> </tr>
  <tr id="D"><td><code>RC4-MD5</code></td> <td>SSLv3</td> <td>RSA</td> <td>RSA</td> <td>RC4(128)</td> <td>MD5</td> <td>&nbsp; </td> </tr>
  <tr id="H"><td><code>IDEA-CBC-MD5</code></td> <td>SSLv2</td> <td>RSA</td> <td>RSA</td> <td>IDEA(128)</td> <td>MD5</td> <td>&nbsp; </td> </tr>
  <tr id="D"><td><code>RC2-CBC-MD5</code></td> <td>SSLv2</td> <td>RSA</td> <td>RSA</td> <td>RC2(128)</td> <td>MD5</td> <td>&nbsp; </td> </tr>
  <tr id="H"><td><code>RC4-MD5</code></td> <td>SSLv2</td> <td>RSA</td> <td>RSA</td> <td>RC4(128)</td> <td>MD5</td> <td>&nbsp; </td> </tr>
  <tr id="D"><td><code>DES-CBC-SHA</code></td> <td>SSLv3</td> <td>RSA</td> <td>RSA</td> <td>DES(56)</td> <td>SHA1</td> <td>&nbsp;</td> </tr>
  <tr id="H"><td><code>RC4-64-MD5</code></td> <td>SSLv2</td> <td>RSA</td> <td>RSA</td> <td>RC4(64)</td> <td>MD5</td> <td>&nbsp; </td> </tr>
  <tr id="D"><td><code>DES-CBC-MD5</code></td> <td>SSLv2</td> <td>RSA</td> <td>RSA</td> <td>DES(56)</td> <td>MD5</td> <td>&nbsp; </td> </tr>
  <tr id="H"><td><code>EXP-DES-CBC-SHA</code></td> <td>SSLv3</td> <td>RSA(512)</td> <td>RSA</td> <td>DES(40)</td> <td>SHA1</td> <td> export</td> </tr>
  <tr id="D"><td><code>EXP-RC2-CBC-MD5</code></td> <td>SSLv3</td> <td>RSA(512)</td> <td>RSA</td> <td>RC2(40)</td> <td>MD5</td> <td>  export</td> </tr>
  <tr id="H"><td><code>EXP-RC4-MD5</code></td> <td>SSLv3</td> <td>RSA(512)</td> <td>RSA</td> <td>RC4(40)</td> <td>MD5</td> <td>  export</td> </tr>
  <tr id="D"><td><code>EXP-RC2-CBC-MD5</code></td> <td>SSLv2</td> <td>RSA(512)</td> <td>RSA</td> <td>RC2(40)</td> <td>MD5</td> <td>  export</td> </tr>
  <tr id="H"><td><code>EXP-RC4-MD5</code></td> <td>SSLv2</td> <td>RSA(512)</td> <td>RSA</td> <td>RC4(40)</td> <td>MD5</td> <td>  export</td> </tr>
  <tr id="D"><td><code>NULL-SHA</code></td> <td>SSLv3</td> <td>RSA</td> <td>RSA</td> <td>None</td> <td>SHA1</td> <td>&nbsp;</td> </tr>
  <tr id="H"><td><code>NULL-MD5</code></td> <td>SSLv3</td> <td>RSA</td> <td>RSA</td> <td>None</td> <td>MD5</td> <td>&nbsp; </td> </tr>
  <tr id="D"><td colspan="7"><em>Diffie-Hellman Ciphers:</em></td></tr>
  <tr id="H"><td><code>ADH-DES-CBC3-SHA</code></td> <td>SSLv3</td> <td>DH</td> <td>None</td> <td>3DES(168)</td> <td>SHA1</td> <td>&nbsp;</td> </tr>
  <tr id="D"><td><code>ADH-DES-CBC-SHA</code></td> <td>SSLv3</td> <td>DH</td> <td>None</td> <td>DES(56)</td> <td>SHA1</td> <td>&nbsp;</td> </tr>
  <tr id="H"><td><code>ADH-RC4-MD5</code></td> <td>SSLv3</td> <td>DH</td> <td>None</td> <td>RC4(128)</td> <td>MD5</td> <td>&nbsp; </td> </tr>
  <tr id="D"><td><code>EDH-RSA-DES-CBC3-SHA</code></td> <td>SSLv3</td> <td>DH</td> <td>RSA</td> <td>3DES(168)</td> <td>SHA1</td> <td>&nbsp;</td> </tr>
  <tr id="H"><td><code>EDH-DSS-DES-CBC3-SHA</code></td> <td>SSLv3</td> <td>DH</td> <td>DSS</td> <td>3DES(168)</td> <td>SHA1</td> <td>&nbsp;</td> </tr>
  <tr id="D"><td><code>EDH-RSA-DES-CBC-SHA</code></td> <td>SSLv3</td> <td>DH</td> <td>RSA</td> <td>DES(56)</td> <td>SHA1</td> <td>&nbsp;</td> </tr>
  <tr id="H"><td><code>EDH-DSS-DES-CBC-SHA</code></td> <td>SSLv3</td> <td>DH</td> <td>DSS</td> <td>DES(56)</td> <td>SHA1</td> <td>&nbsp;</td> </tr>
  <tr id="D"><td><code>EXP-EDH-RSA-DES-CBC-SHA</code></td> <td>SSLv3</td> <td>DH(512)</td> <td>RSA</td> <td>DES(40)</td> <td>SHA1</td> <td> export</td> </tr>
  <tr id="H"><td><code>EXP-EDH-DSS-DES-CBC-SHA</code></td> <td>SSLv3</td> <td>DH(512)</td> <td>DSS</td> <td>DES(40)</td> <td>SHA1</td> <td> export</td> </tr>
  <tr id="D"><td><code>EXP-ADH-DES-CBC-SHA</code></td> <td>SSLv3</td> <td>DH(512)</td> <td>None</td> <td>DES(40)</td> <td>SHA1</td> <td> export</td> </tr>
  <tr id="H"><td><code>EXP-ADH-RC4-MD5</code></td> <td>SSLv3</td> <td>DH(512)</td> <td>None</td> <td>RC4(40)</td> <td>MD5</td> <td>  export</td> </tr>
  </table>
  </td>
  </tr></table>
  </td></tr></table>
  </div>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>SSLCertificateFile</name>
  <description>Server PEM-encoded X.509 Certificate file</description>
  <syntax>SSLCertificateFile <em>file-path</em></syntax>
  <contextlist><context>server config</context>
  <context>virtual host</context></contextlist>
  
  <usage>
  <p>
  This directive points to the PEM-encoded Certificate file for the server and
  optionally also to the corresponding RSA or DSA Private Key file for it
  (contained in the same file). If the contained Private Key is encrypted the
  Pass Phrase dialog is forced at startup time. This directive can be used up to
  two times (referencing different filenames) when both a RSA and a DSA based
  server certificate is used in parallel.</p>
  <example><title>Example</title>
  SSLCertificateFile /usr/local/apache/conf/ssl.crt/server.crt
  </example>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>SSLCertificateKeyFile</name>
  <description>Server PEM-encoded Private Key file</description>
  <syntax>SSLCertificateKeyFile <em>file-path</em></syntax>
  <contextlist><context>server config</context>
  <context>virtual host</context></contextlist>
  
  <usage>
  <p>
  This directive points to the PEM-encoded Private Key file for the
  server. If the Private Key is not combined with the Certificate in the
  <directive>SSLCertificateFile</directive>, use this additional directive to
  point to the file with the stand-alone Private Key. When
  <directive>SSLCertificateFile</directive> is used and the file
  contains both the Certificate and the Private Key this directive need
  not be used. But we strongly discourage this practice.  Instead we
  recommend you to separate the Certificate and the Private Key. If the
  contained Private Key is encrypted, the Pass Phrase dialog is forced
  at startup time. This directive can be used up to two times
  (referencing different filenames) when both a RSA and a DSA based
  private key is used in parallel.</p>
  <example><title>Example</title>
  SSLCertificateKeyFile /usr/local/apache/conf/ssl.key/server.key
  </example>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>SSLCertificateChainFile</name>
  <description>File of PEM-encoded Server CA Certificates</description>
  <syntax>SSLCertificateChainFile <em>file-path</em></syntax>
  <contextlist><context>server config</context>
  <context>virtual host</context></contextlist>
  
  <usage>
  <p>
  This directive sets the optional <em>all-in-one</em> file where you can
  assemble the certificates of Certification Authorities (CA) which form the
  certificate chain of the server certificate. This starts with the issuing CA
  certificate of of the server certificate and can range up to the root CA
  certificate. Such a file is simply the concatenation of the various
  PEM-encoded CA Certificate files, usually in certificate chain order.</p>
  <p>
  This should be used alternatively and/or additionally to <directive
  module="mod_ssl">SSLCACertificatePath</directive> for explicitly
  constructing the server certificate chain which is sent to the browser
  in addition to the server certificate. It is especially useful to
  avoid conflicts with CA certificates when using client
  authentication. Because although placing a CA certificate of the
  server certificate chain into <directive
  module="mod_ssl">SSLCACertificatePath</directive> has the same effect
  for the certificate chain construction, it has the side-effect that
  client certificates issued by this same CA certificate are also
  accepted on client authentication. That's usually not one expect.</p>
  <p>
  But be careful: Providing the certificate chain works only if you are using a
  <em>single</em> (either RSA <em>or</em> DSA) based server certificate. If you are
  using a coupled RSA+DSA certificate pair, this will work only if actually both
  certificates use the <em>same</em> certificate chain. Else the browsers will be
  confused in this situation.</p>
  <example><title>Example</title>
  SSLCertificateChainFile /usr/local/apache/conf/ssl.crt/ca.crt
  </example>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>SSLCACertificatePath</name>
  <description>Directory of PEM-encoded CA Certificates for 
  Client Auth</description>
  <syntax>SSLCACertificatePath <em>directory-path</em></syntax>
  <contextlist><context>server config</context>
  <context>virtual host</context></contextlist>
  
  <usage>
  <p>
  This directive sets the directory where you keep the Certificates of
  Certification Authorities (CAs) whose clients you deal with. These are used to
  verify the client certificate on Client Authentication.</p>
  <p>
  The files in this directory have to be PEM-encoded and are accessed through
  hash filenames. So usually you can't just place the Certificate files
  there: you also have to create symbolic links named
  <em>hash-value</em><code>.N</code>. And you should always make sure this directory
  contains the appropriate symbolic links. Use the <code>Makefile</code> which
  comes with mod_ssl to accomplish this task.</p>
  <example><title>Example</title>
  SSLCACertificatePath /usr/local/apache/conf/ssl.crt/
  </example>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>SSLCACertificateFile</name>
  <description>File of concatenated PEM-encoded CA Certificates 
  for Client Auth</description>
  <syntax>SSLCACertificateFile <em>file-path</em></syntax>
  <contextlist><context>server config</context>
  <context>virtual host</context></contextlist>
  
  <usage>
  <p>
  This directive sets the <em>all-in-one</em> file where you can assemble the
  Certificates of Certification Authorities (CA) whose <em>clients</em> you deal
  with. These are used for Client Authentication. Such a file is simply the
  concatenation of the various PEM-encoded Certificate files, in order of
  preference. This can be used alternatively and/or additionally to 
  <directive module="mod_ssl">SSLCACertificatePath</directive>.</p>
  <example><title>Example</title>
  SSLCACertificateFile /usr/local/apache/conf/ssl.crt/ca-bundle-client.crt
  </example>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>SSLCARevocationPath</name>
  <description>Directory of PEM-encoded CA CRLs for 
  Client Auth</description>
  <syntax>SSLCARevocationPath <em>directory-path</em></syntax>
  <contextlist><context>server config</context>
  <context>virtual host</context></contextlist>
  
  <usage>
  <p>
  This directive sets the directory where you keep the Certificate Revocation
  Lists (CRL) of Certification Authorities (CAs) whose clients you deal with.
  These are used to revoke the client certificate on Client Authentication.</p>
  <p>
  The files in this directory have to be PEM-encoded and are accessed through
  hash filenames. So usually you have not only to place the CRL files there.
  Additionally you have to create symbolic links named
  <em>hash-value</em><code>.rN</code>. And you should always make sure this directory
  contains the appropriate symbolic links. Use the <code>Makefile</code> which
  comes with <module>mod_ssl</module> to accomplish this task.</p>
  <example><title>Example</title>
  SSLCARevocationPath /usr/local/apache/conf/ssl.crl/
  </example>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>SSLCARevocationFile</name>
  <description>File of concatenated PEM-encoded CA CRLs for 
  Client Auth</description>
  <syntax>SSLCARevocationFile <em>file-path</em></syntax>
  <contextlist><context>server config</context>
  <context>virtual host</context></contextlist>
  
  <usage>
  <p>
  This directive sets the <em>all-in-one</em> file where you can
  assemble the Certificate Revocation Lists (CRL) of Certification
  Authorities (CA) whose <em>clients</em> you deal with. These are used
  for Client Authentication.  Such a file is simply the concatenation of
  the various PEM-encoded CRL files, in order of preference. This can be
  used alternatively and/or additionally to <directive
  module="mod_ssl">SSLCARevocationPath</directive>.</p>
  <example><title>Example</title>
  SSLCARevocationFile /usr/local/apache/conf/ssl.crl/ca-bundle-client.crl
  </example>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>SSLVerifyClient</name>
  <description>Type of Client Certificate verification</description>
  <syntax>SSLVerifyClient <em>level</em></syntax>
  <default>SSLVerifyClient none</default>
  <contextlist><context>server config</context>
  <context>virtual host</context>
  <context>directory</context>
  <context>.htaccess</context></contextlist>
  <override>AuthConfig</override>
  
  <usage>
  <p>
  This directive sets the Certificate verification level for the Client
  Authentication. Notice that this directive can be used both in per-server and
  per-directory context. In per-server context it applies to the client
  authentication process used in the standard SSL handshake when a connection is
  established. In per-directory context it forces a SSL renegotation with the
  reconfigured client verification level after the HTTP request was read but
  before the HTTP response is sent.</p>
  <p>
  The following levels are available for <em>level</em>:</p>
  <ul>
  <li><strong>none</strong>:
       no client Certificate is required at all</li>
  <li><strong>optional</strong>:
       the client <em>may</em> present a valid Certificate</li>
  <li><strong>require</strong>:
       the client <em>has to</em> present a valid Certificate</li>
  <li><strong>optional_no_ca</strong>:
       the client may present a valid Certificate<br />
       but it need not to be (successfully) verifiable.</li>
  </ul>
  <p>In practice only levels <strong>none</strong> and
  <strong>require</strong> are really interesting, because level
  <strong>optional</strong> doesn't work with all browsers and level
  <strong>optional_no_ca</strong> is actually against the idea of
  authentication (but can be used to establish SSL test pages, etc.)</p>
  <example><title>Example</title>
  SSLVerifyClient require
  </example>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>SSLVerifyDepth</name>
  <description>Maximum depth of CA Certificates in Client 
  Certificate verification</description>
  <syntax>SSLVerifyDepth <em>number</em></syntax>
  <default>SSLVerifyDepth 1</default>
  <contextlist><context>server config</context>
  <context>virtual host</context>
  <context>directory</context>
  <context>.htaccess</context></contextlist>
  <override>AuthConfig</override>
  
  <usage>
  <p>
  This directive sets how deeply mod_ssl should verify before deciding that the
  clients don't have a valid certificate. Notice that this directive can be
  used both in per-server and per-directory context. In per-server context it
  applies to the client authentication process used in the standard SSL
  handshake when a connection is established. In per-directory context it forces
  a SSL renegotation with the reconfigured client verification depth after the
  HTTP request was read but before the HTTP response is sent.</p>
  <p>
  The depth actually is the maximum number of intermediate certificate issuers,
  i.e. the number of CA certificates which are max allowed to be followed while
  verifying the client certificate. A depth of 0 means that self-signed client
  certificates are accepted only, the default depth of 1 means the client
  certificate can be self-signed or has to be signed by a CA which is directly
  known to the server (i.e. the CA's certificate is under
  <directive module="mod_ssl">SSLCACertificatePath</directive>), etc.</p>
  <example><title>Example</title>
  SSLVerifyDepth 10
  </example>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>SSLLog</name>
  <description>Where to write the dedicated SSL engine logfile</description>
  <syntax>SSLLog <em>file-path</em></syntax>
  <contextlist><context>server config</context>
  <context>virtual host</context></contextlist>
  
  <usage>
  <p>
  This directive sets the name of the dedicated SSL protocol engine logfile.
  Error type messages are additionally duplicated to the general Apache error
  log file (directive <code>ErrorLog</code>). Put this somewhere where it cannot
  be used for symlink attacks on a real server (i.e. somewhere where only root
  can write). If the <em>file-path</em> does not begin with a slash
  ('<code>/</code>') then it is assumed to be relative to the <em>Server
  Root</em>. If <em>file-path</em> begins with a bar ('<code>|</code>') then the
  following string is assumed to be a path to an executable program to which a
  reliable pipe can be established. The directive should occur only once per
  virtual server config.</p>
  <example><title>Example</title>
  SSLLog /usr/local/apache/logs/ssl_engine_log
  </example>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>SSLLogLevel</name>
  <description>Logging level for the dedicated SSL engine 
  logfile</description>
  <syntax>SSLLogLevel <em>level</em></syntax>
  <default>SSLLogLevel none</default>
  <contextlist><context>server config</context>
  <context>virtual host</context></contextlist>
  
  <usage>
  <p>
  This directive sets the verbosity degree of the dedicated SSL protocol engine
  logfile. The <em>level</em> is one of the following (in ascending order where
  higher levels include lower levels):</p>
  <ul>
  <li><code>none</code><br />
      no dedicated SSL logging is done, but messages of level
      ``<code>error</code>'' are still written to the general Apache error
      logfile.
  </li>
  <li><code>error</code><br />
      log messages of error type only, i.e. messages which show fatal situations
      (processing is stopped). Those messages are also duplicated to the
      general Apache error logfile.
  </li>
  <li><code>warn</code><br />
      log also warning messages, i.e. messages which show non-fatal problems
      (processing is continued).
  </li>
  <li><code>info</code><br />
      log also informational messages, i.e. messages which show major
      processing steps.
  </li>
  <li><code>trace</code><br />
      log also trace messages, i.e. messages which show minor processing steps.
  </li>
  <li><code>debug</code><br />
      log also debugging messages, i.e. messages which show development and
      low-level I/O information.
  </li>
  </ul>
  <example><title>Example</title>
  SSLLogLevel warn
  </example>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>SSLOptions</name>
  <description>Configure various SSL engine run-time options</description>
  <syntax>SSLOptions [+|-]<em>option</em> ...</syntax>
  <contextlist><context>server config</context>
  <context>virtual host</context>
  <context>directory</context>
  <context>.htaccess</context></contextlist>
  <override>Options</override>
  
  <usage>
  <p>
  This directive can be used to control various run-time options on a
  per-directory basis. Normally, if multiple <code>SSLOptions</code>
  could apply to a directory, then the most specific one is taken
  completely; the options are not merged. However if <em>all</em> the
  options on the <code>SSLOptions</code> directive are preceded by a
  plus (<code>+</code>) or minus (<code>-</code>) symbol, the options
  are merged. Any options preceded by a <code>+</code> are added to the
  options currently in force, and any options preceded by a
  <code>-</code> are removed from the options currently in force.</p>
  <p>
  The available <em>option</em>s are:</p>
  <ul>
  <li><code>StdEnvVars</code>
      <p>
      When this option is enabled, the standard set of SSL related CGI/SSI
      environment variables are created. This per default is disabled for
      performance reasons, because the information extraction step is a
      rather expensive operation. So one usually enables this option for
      CGI and SSI requests only.</p>
  </li>
  <li><code>CompatEnvVars</code>
      <p>
      When this option is enabled, additional CGI/SSI environment variables are
      created for backward compatibility to other Apache SSL solutions. Look in
      the <a href="../ssl/ssl_compat.html">Compatibility</a> chapter for details
      on the particular variables generated.</p>
  </li>
  <li><code>ExportCertData</code>
      <p>
      When this option is enabled, additional CGI/SSI environment variables are
      created: <code>SSL_SERVER_CERT</code>, <code>SSL_CLIENT_CERT</code> and
      <code>SSL_CLIENT_CERT_CHAIN</code><em>n</em> (with <em>n</em> = 0,1,2,..).
      These contain the PEM-encoded X.509 Certificates of server and client for
      the current HTTPS connection and can be used by CGI scripts for deeper
      Certificate checking. Additionally all other certificates of the client
      certificate chain are provided, too. This bloats up the environment a
      little bit which is why you have to use this option to enable it on
      demand.</p>
  </li>
  <li><code>FakeBasicAuth</code>
      <p>
      When this option is enabled, the Subject Distinguished Name (DN) of the
      Client X509 Certificate is translated into a HTTP Basic Authorization
      username. This means that the standard Apache authentication methods can
      be used for access control. The user name is just the Subject of the
      Client's X509 Certificate (can be determined by running OpenSSL's
      <code>openssl x509</code> command: <code>openssl x509 -noout -subject -in
      </code><em>certificate</em><code>.crt</code>). Note that no password is
      obtained from the user. Every entry in the user file needs this password:
      ``<code>xxj31ZMTZzkVA</code>'', which is the DES-encrypted version of the
      word `<code>password</code>''. Those who live under MD5-based encryption
      (for instance under FreeBSD or BSD/OS, etc.) should use the following MD5
      hash of the same word: ``<code>$1$OXLyS...$Owx8s2/m9/gfkcRVXzgoE/</code>''.</p>
  </li>
  <li><code>StrictRequire</code>
      <p>
      This <em>forces</em> forbidden access when <code>SSLRequireSSL</code> or
      <code>SSLRequire</code> successfully decided that access should be
      forbidden. Usually the default is that in the case where a ``<code>Satisfy
      any</code>'' directive is used, and other access restrictions are passed,
      denial of access due to <code>SSLRequireSSL</code> or
      <code>SSLRequire</code> is overridden (because that's how the Apache
      <code>Satisfy</code> mechanism should work.) But for strict access restriction
      you can use <code>SSLRequireSSL</code> and/or <code>SSLRequire</code> in
      combination with an ``<code>SSLOptions +StrictRequire</code>''. Then an
      additional ``<code>Satisfy Any</code>'' has no chance once mod_ssl has
      decided to deny access.</p>
  </li>
  <li><code>OptRenegotiate</code>
      <p>
      This enables optimized SSL connection renegotiation handling when SSL
      directives are used in per-directory context. By default a strict
      scheme is enabled where <em>every</em> per-directory reconfiguration of
      SSL parameters causes a <em>full</em> SSL renegotiation handshake. When this
      option is used mod_ssl tries to avoid unnecessary handshakes by doing more
      granular (but still safe) parameter checks. Nevertheless these granular
      checks sometimes maybe not what the user expects, so enable this on a
      per-directory basis only, please.</p>
  </li>
  </ul>
  <example><title>Example</title>
  SSLOptions +FakeBasicAuth -StrictRequire<br />
  &lt;Files ~ "\.(cgi|shtml)$"&gt;<br />
      SSLOptions +StdEnvVars +CompatEnvVars -ExportCertData<br />
  &lt;Files&gt;
  </example>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>SSLRequireSSL</name>
  <description>Deny access when SSL is not used for the 
  HTTP request</description>
  <syntax>SSLRequireSSL</syntax>
  <contextlist><context>directory</context>
  <context>.htaccess</context></contextlist>
  <override>AuthConfig</override>
  
  <usage>
  <p><!-- XXX: I think the syntax is wrong -->
  This directive forbids access unless HTTP over SSL (i.e. HTTPS) is enabled for
  the current connection. This is very handy inside the SSL-enabled virtual
  host or directories for defending against configuration errors that expose
  stuff that should be protected. When this directive is present all requests
  are denied which are not using SSL.</p>
  <example><title>Example</title>
  SSLRequireSSL
  </example>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>SSLRequire</name>
  <description>Allow access only when an arbitrarily complex 
  boolean expression is true</description>
  <syntax>SSLRequire <em>expression</em></syntax>
  <contextlist><context>directory</context>
  <context>.htaccess</context></contextlist>
  <override>AuthConfig</override>
  
  <usage>
  <p>
  This directive specifies a general access requirement which has to be
  fulfilled in order to allow access. It's a very powerful directive because the
  requirement specification is an arbitrarily complex boolean expression
  containing any number of access checks.</p>
  <p>
  The <em>expression</em> must match the following syntax (given as a BNF
  grammar notation):</p>
  <blockquote>
  <pre>
  expr     ::= "<strong>true</strong>" | "<strong>false</strong>"
             | "<strong>!</strong>" expr
             | expr "<strong>&amp;&amp;</strong>" expr
             | expr "<strong>||</strong>" expr
             | "<strong>(</strong>" expr "<strong>)</strong>"
             | comp
  
  comp     ::= word "<strong>==</strong>" word | word "<strong>eq</strong>" word
             | word "<strong>!=</strong>" word | word "<strong>ne</strong>" word
             | word "<strong>&lt;</strong>"  word | word "<strong>lt</strong>" word
             | word "<strong>&lt;=</strong>" word | word "<strong>le</strong>" word
             | word "<strong>&gt;</strong>"  word | word "<strong>gt</strong>" word
             | word "<strong>&gt;=</strong>" word | word "<strong>ge</strong>" word
             | word "<strong>in</strong>" "<strong>{</strong>" wordlist "<strong>}</strong>"
             | word "<strong>=~</strong>" regex
             | word "<strong>!~</strong>" regex
  
  wordlist ::= word
             | wordlist "<strong>,</strong>" word
  
  word     ::= digit
             | cstring
             | variable
             | function
  
  digit    ::= [0-9]+
  cstring  ::= "..."
  variable ::= "<strong>%{</strong>" varname "<strong>}</strong>"
  function ::= funcname "<strong>(</strong>" funcargs "<strong>)</strong>"
  </pre>
  </blockquote>
  <p>while for <code>varname</code> any variable from <a
  href="#table3">Table 3</a> can be used. Finally for
  <code>funcname</code> the following functions are available:</p>
  <ul>
  <li><code>file(</code><em>filename</em><code>)</code>
      <p>
      This function takes one string argument and expands to the contents of the
      file. This is especially useful for matching this contents against a
      regular expression, etc.</p>
  </li>
  </ul>
  <p>Notice that <em>expression</em> is first parsed into an internal machine
  representation and then evaluated in a second step. Actually, in Global and
  Per-Server Class context <em>expression</em> is parsed at startup time and
  at runtime only the machine representation is executed. For Per-Directory
  context this is different: here <em>expression</em> has to be parsed and
  immediately executed for every request.</p>
  <example><title>Example</title>
  SSLRequire (    %{SSL_CIPHER} !~ m/^(EXP|NULL)-/ \<br />
              and %{SSL_CLIENT_S_DN_O} eq "Snake Oil, Ltd." \<br />
              and %{SSL_CLIENT_S_DN_OU} in {"Staff", "CA", "Dev"} \<br />
              and %{TIME_WDAY} &gt;= 1 and %{TIME_WDAY} &lt;= 5 \<br />
              and %{TIME_HOUR} &gt;= 8 and %{TIME_HOUR} &lt;= 20       ) \<br />
             or %{REMOTE_ADDR} =~ m/^192\.76\.162\.[0-9]+$/
  </example>
  <div align="center">
  <a name="table3"></a>
  <table width="600" cellspacing="0" cellpadding="1" border="0" summary="">
  <caption align="bottom" id="sf">Table 3: Available Variables for SSLRequire</caption>
  <tr><td bgcolor="#cccccc">
  <table width="598" cellpadding="5" cellspacing="0" border="0" summary="">
  <tr><td valign="top" align="center" bgcolor="#ffffff">
  <table summary=""><tr><td>
  <em>Standard CGI/1.0 and Apache variables:</em>
  <pre>
  HTTP_USER_AGENT        PATH_INFO             AUTH_TYPE
  HTTP_REFERER           QUERY_STRING          SERVER_SOFTWARE
  HTTP_COOKIE            REMOTE_HOST           API_VERSION
  HTTP_FORWARDED         REMOTE_IDENT          TIME_YEAR
  HTTP_HOST              IS_SUBREQ             TIME_MON
  HTTP_PROXY_CONNECTION  DOCUMENT_ROOT         TIME_DAY
  HTTP_ACCEPT            SERVER_ADMIN          TIME_HOUR
  HTTP:headername        SERVER_NAME           TIME_MIN
  THE_REQUEST            SERVER_PORT           TIME_SEC
  REQUEST_METHOD         SERVER_PROTOCOL       TIME_WDAY
  REQUEST_SCHEME         REMOTE_ADDR           TIME
  REQUEST_URI            REMOTE_USER           ENV:<strong>variablename</strong>
  REQUEST_FILENAME
  </pre>
  <em>SSL-related variables:</em>
  <pre>
  HTTPS                  SSL_CLIENT_M_VERSION   SSL_SERVER_M_VERSION
                         SSL_CLIENT_M_SERIAL    SSL_SERVER_M_SERIAL
  SSL_PROTOCOL           SSL_CLIENT_V_START     SSL_SERVER_V_START
  SSL_SESSION_ID         SSL_CLIENT_V_END       SSL_SERVER_V_END
  SSL_CIPHER             SSL_CLIENT_S_DN        SSL_SERVER_S_DN
  SSL_CIPHER_EXPORT      SSL_CLIENT_S_DN_C      SSL_SERVER_S_DN_C
  SSL_CIPHER_ALGKEYSIZE  SSL_CLIENT_S_DN_ST     SSL_SERVER_S_DN_ST
  SSL_CIPHER_USEKEYSIZE  SSL_CLIENT_S_DN_L      SSL_SERVER_S_DN_L
  SSL_VERSION_LIBRARY    SSL_CLIENT_S_DN_O      SSL_SERVER_S_DN_O
  SSL_VERSION_INTERFACE  SSL_CLIENT_S_DN_OU     SSL_SERVER_S_DN_OU
                         SSL_CLIENT_S_DN_CN     SSL_SERVER_S_DN_CN
                         SSL_CLIENT_S_DN_T      SSL_SERVER_S_DN_T
                         SSL_CLIENT_S_DN_I      SSL_SERVER_S_DN_I
                         SSL_CLIENT_S_DN_G      SSL_SERVER_S_DN_G
                         SSL_CLIENT_S_DN_S      SSL_SERVER_S_DN_S
                         SSL_CLIENT_S_DN_D      SSL_SERVER_S_DN_D
                         SSL_CLIENT_S_DN_UID    SSL_SERVER_S_DN_UID
                         SSL_CLIENT_S_DN_Email  SSL_SERVER_S_DN_Email
                         SSL_CLIENT_I_DN        SSL_SERVER_I_DN
                         SSL_CLIENT_I_DN_C      SSL_SERVER_I_DN_C
                         SSL_CLIENT_I_DN_ST     SSL_SERVER_I_DN_ST
                         SSL_CLIENT_I_DN_L      SSL_SERVER_I_DN_L
                         SSL_CLIENT_I_DN_O      SSL_SERVER_I_DN_O
                         SSL_CLIENT_I_DN_OU     SSL_SERVER_I_DN_OU
                         SSL_CLIENT_I_DN_CN     SSL_SERVER_I_DN_CN
                         SSL_CLIENT_I_DN_T      SSL_SERVER_I_DN_T
                         SSL_CLIENT_I_DN_I      SSL_SERVER_I_DN_I
                         SSL_CLIENT_I_DN_G      SSL_SERVER_I_DN_G
                         SSL_CLIENT_I_DN_S      SSL_SERVER_I_DN_S
                         SSL_CLIENT_I_DN_D      SSL_SERVER_I_DN_D
                         SSL_CLIENT_I_DN_UID    SSL_SERVER_I_DN_UID
                         SSL_CLIENT_I_DN_Email  SSL_SERVER_I_DN_Email
                         SSL_CLIENT_A_SIG       SSL_SERVER_A_SIG
                         SSL_CLIENT_A_KEY       SSL_SERVER_A_KEY
                         SSL_CLIENT_CERT        SSL_SERVER_CERT
                         SSL_CLIENT_CERT_CHAIN<strong>n</strong>
                         SSL_CLIENT_VERIFY
  </pre>
  </td></tr></table>
  </td>
  </tr></table>
  </td></tr></table>
  </div>
  </usage>
  </directivesynopsis>
  
  </modulesynopsis>
  
  
  
  1.1                  httpd-2.0/docs/manual/mod/perchild.xml
  
  Index: perchild.xml
  ===================================================================
  <?xml version="1.0"?>
  <!DOCTYPE modulesynopsis SYSTEM "../style/modulesynopsis.dtd">
  <?xml-stylesheet type="text/xsl" href="../style/manual.xsl"?>
  <modulesynopsis>
  
  <name>perchild</name>
  <description>Multi-Processing Module allowing for daemon processes
      serving requests to be assigned a variety of different
      userids</description>
  <status>MPM</status>
  <sourcefile>perchild.c</sourcefile>
  <identifier>mpm_perchild_module</identifier>
  
  <summary>
  <note type="warning">
  This MPM does not currently work on most platforms.  Work is ongoing to
  make it functional.
  </note>
  
      <p>This Multi-Processing Module (MPM) implements a hybrid
      multi-process, multi-threaded web server. A fixed number of
      processes create threads to handle requests. Fluctuations in
      load are handled by increasing or decreasing the number of
      threads in each process.</p>
  
      <p>A single control process launches the number of child processes
      indicated by the <directive
      module="mpm_common">NumServers</directive> directive at server
      startup. Each child process creates threads as specified in the
      <code>StartThreads</code> directive. The individual threads then
      listen for connections and serve them when they arrive.</p>
  
      <p>Apache always tries to maintain a pool of <em>spare</em> or
      idle server threads, which stand ready to serve incoming
      requests. In this way, clients do not need to wait for new
      threads to be created. For each child process, Apache assesses
      the number of idle threads and creates or destroys threads to
      keep this number within the boundaries specified by
      <code>MinSpareThreads</code> and <code>MaxSpareThreads</code>.
      Since this process is very self-regulating, it is rarely
      necessary to modify these directives from their default values.
      The maximum number of clients that may be served simultaneously
      is determined by multiplying the number of server processes
      that will be created (<code>NumServers</code>) by the maximum
      number of threads created in each process
      (<code>MaxThreadsPerChild</code>).</p>
  
      <p>While the parent process is usually started as root under
      Unix in order to bind to port 80, the child processes and
      threads are launched by Apache as a less-privileged user. The
      <code>User</code> and <code>Group</code> directives are used to
      set the privileges of the Apache child processes. The child
      processes must be able to read all the content that will be
      served, but should have as few privileges beyond that as
      possible. In addition, unless <a
      href="../suexec.html">suexec</a> is used, these directives also
      set the privileges which will be inherited by CGI scripts.</p>
  
      <p><code>MaxRequestsPerChild</code> controls how frequently the
      server recycles processes by killing old ones and launching new
      ones.</p>
  
      <p>See also: <a href="../bind.html">Setting which addresses and
      ports Apache uses</a>.</p>
  
      <p>In addition it adds the extra ability to specify that
      specific processes should serve requests under different
      userids. These processes can then be associated with specific
      virtual hosts.</p>
      <!-- XXX: This desperately needs more explanation. -->
  </summary>
  
  <directivesynopsis location="mpm_common">
  <name>CoreDumpDirectory</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common">
  <name>Group</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common">
  <name>PidFile</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common">
  <name>Listen</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common">
  <name>ListenBacklog</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common">
  <name>LockFile</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common">
  <name>MaxRequestsPerChild</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common">
  <name>MaxSpareThreads</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common">
  <name>MaxThreadsPerChild</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common">
  <name>MinSpareThreads</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common">
  <name>NumServers</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common">
  <name>ScoreBoardFile</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common">
  <name>SendBufferSize</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common">
  <name>StartThreads</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common">
  <name>User</name>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>AssignUserId</name>
  <syntax>AssignUserID <em>user_id</em> <em>group_id</em></syntax>
  <contextlist><context>virtual host</context></contextlist>
  
  <usage>
      <p>Tie a virtual host to a specific child process. Requests addressed to
  the virtual host where this directive appears will be served by the process
  running with the specified user and group id.</p>
  </usage>
  </directivesynopsis>
  
  <directivesynopsis>
  <name>ChildPerUserId</name>
  <syntax>ChildPerUserID <em>user_id</em>
  <em>group_id</em> <em>child_id</em></syntax>
  <contextlist><context>server config</context></contextlist>
  
  <usage>
      <p>Specify a user id and group id for a specific child process. The number of
  children if set by the <a href="mpm_common.html#numservers">NumServers</a>
  directive. For example, the default value for <a
  href="mpm_common.html#numservers">NumServers</a> is 5 and that means
  children ids 1,2,3,4 and 5 are available for assigment. If a child does not
  have an associated ChildPerUserID, it inherits the <a
  href="mpm_common.html#user">User</a> and <a
  href="mpm_common.html#group">Group</a> settings from the main server </p> 
  </usage>
  </directivesynopsis>
  
  </modulesynopsis>
  
  
  
  
  1.1                  httpd-2.0/docs/manual/mod/worker.xml
  
  Index: worker.xml
  ===================================================================
  <?xml version="1.0"?>
  <!DOCTYPE modulesynopsis SYSTEM "../style/modulesynopsis.dtd">
  <?xml-stylesheet type="text/xsl" href="../style/manual.xsl"?>
  <modulesynopsis>
  <name>worker</name>
  <description>Multi-Processing Module implementing a hybrid
      multi-threaded multi-process web server</description>
  <status>MPM</status>
  <sourcefile>worker.c</sourcefile>
  <identifier>mpm_worker_module</identifier>
  
  <summary>
      <p>This Multi-Processing Module (MPM) is the default for most
      unix-like operating systems. It implements a hybrid
      multi-process multi-threaded server. Each process has a fixed
      number of threads. The server adjusts to handle load by
      increasing or decreasing the number of processes.</p>
  
      <p>A single control process is responsible for launching child
      processes. Each child process creates a fixed number of threads
      as specified in the <code>ThreadsPerChild</code> directive. The
      individual threads then listen for connections and serve them
      when they arrive.</p>
  
      <p>Apache always tries to maintain a pool of <em>spare</em> or
      idle server threads, which stand ready to serve incoming
      requests. In this way, clients do not need to wait for a new
      threads or processes to be created before their requests can be
      served. Apache assesses the total number of idle threads in all
      processes, and forks or kills processes to keep this number
      within the boundaries specified by <code>MinSpareThreads</code>
      and <code>MaxSpareThreads</code>. Since this process is very
      self-regulating, it is rarely necessary to modify these
      directives from their default values. The maximum number of
      clients that may be served simultaneously is determined by
      multiplying the maximum number of server processes that will be
      created (<code>MaxClients</code>) by the number of threads
      created in each process (<code>ThreadsPerChild</code>).</p>
  
      <p>While the parent process is usually started as root under
      Unix in order to bind to port 80, the child processes and
      threads are launched by Apache as a less-privileged user. The
      <code>User</code> and <code>Group</code> directives are used to
      set the privileges of the Apache child processes. The child
      processes must be able to read all the content that will be
      served, but should have as few privileges beyond that as
      possible. In addition, unless <a
      href="../suexec.html">suexec</a> is used, these directives also
      set the privileges which will be inherited by CGI scripts.</p>
  
      <p><code>MaxRequestsPerChild</code> controls how frequently the
      server recycles processes by killing old ones and launching new
      ones.</p>
  
      <p>See also: <a href="../bind.html">Setting which addresses and
      ports Apache uses</a>.</p>
  </summary>
  
  <directivesynopsis location="mpm_common"><name>CoreDumpDirectory</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common"><name>Group</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common"><name>PidFile</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common"><name>Listen</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common"><name>ListenBacklog</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common"><name>LockFile</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common"><name>MaxClients</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common"><name>MaxRequestsPerChild</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common"><name>MaxSpareThreads</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common"><name>MinSpareThreads</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common"><name>ScoreBoardFile</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common"><name>SendBufferSize</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common"><name>ServerLimit</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common"><name>StartServers</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common"><name>ThreadLimit</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common"><name>ThreadsPerChild</name>
  </directivesynopsis>
  <directivesynopsis location="mpm_common"><name>User</name>
  </directivesynopsis>
  
  </modulesynopsis>
  
  

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