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<manualpage metafile="ssl_howto.xml.meta">
<parentdocument href="./">SSL/TLS</parentdocument>

  <title>SSL/TLS Strong Encryption: How-To</title>

<summary>

<p>This documented is intended to get you started, and get a few things
working. You are strongly encouraged to read the rest of the SSL
documentation, and arrive at a deeper understanding of the material,
before progressing to the advanced techniques.</p>
</summary>

<section id="configexample">
<title>Basic Configuration Example</title>

<p>Your SSL configuration will need to contain, at minimum, the
following directives.</p>

<highlight language="config">
LoadModule ssl_module modules/mod_ssl.so

Listen 443
&lt;VirtualHost *:443&gt;
    ServerName www.example.com
    SSLEngine on
    SSLCertificateFile /path/to/www.example.com.cert
    SSLCertificateKeyFile /path/to/www.example.com.key
&lt;/VirtualHost&gt;
</highlight>

</section>

<section id="ciphersuites">
<title>Cipher Suites and Enforcing Strong Security</title>
<ul>
<li><a href="#onlystrong">How can I create an SSL server which accepts strong encryption only?</a></li>
<li><a href="#strongurl">How can I create an SSL server which accepts all types of ciphers in general, but
requires a strong cipher for access to a particular URL?</a></li>
</ul>

<section id="onlystrong">
<title>How can I create an SSL server which accepts strong encryption
only?</title>
    <p>The following enables only the strongest ciphers:</p>
    <highlight language="config">
      SSLCipherSuite HIGH:!aNULL:!MD5
    </highlight>

    <p>While with the following configuration you specify a preference
    for specific speed-optimized ciphers (which will be selected by
    mod_ssl, provided that they are supported by the client):</p>

    <highlight language="config">
SSLCipherSuite RC4-SHA:AES128-SHA:HIGH:!aNULL:!MD5
SSLHonorCipherOrder on
    </highlight>
</section>

<section id="strongurl">
<title>How can I create an SSL server which accepts all types of ciphers
in general, but requires a strong ciphers for access to a particular
URL?</title>
    <p>Obviously, a server-wide <directive
    module="mod_ssl">SSLCipherSuite</directive> which restricts
    ciphers to the strong variants, isn't the answer here. However,
    <module>mod_ssl</module> can be reconfigured within <code>Location</code>
    blocks, to give a per-directory solution, and can automatically force
    a renegotiation of the SSL parameters to meet the new configuration.
    This can be done as follows:</p>
    <highlight language="config">
# be liberal in general
SSLCipherSuite ALL:!aNULL:RC4+RSA:+HIGH:+MEDIUM:+LOW:+EXP:+eNULL

&lt;Location /strong/area&gt;
# but https://hostname/strong/area/ and below
# requires strong ciphers
SSLCipherSuite HIGH:!aNULL:!MD5
&lt;/Location&gt;
    </highlight>
</section>
</section>
<!-- /ciphersuites -->

<section id="accesscontrol">
<title>Client Authentication and Access Control</title>
<ul>
<li><a href="#allclients">How can I force clients to authenticate using certificates?</a></li>
<li><a href="#arbitraryclients">How can I force clients to authenticate using certificates for a
        particular URL, but still allow arbitrary clients to access the rest of the server?</a></li>
<li><a href="#certauthenticate">How can I allow only clients who have certificates to access a
        particular URL, but allow all clients to access the rest of the server?</a></li>
<li><a href="#intranet">How can I require HTTPS with strong ciphers, and either
basic authentication or client certificates, for access to part of the
Intranet website, for clients coming from the Internet?</a></li>
</ul>

<section id="allclients">
<title>How can I force clients to authenticate using certificates?</title>

    <p>When you know all of your users (eg, as is often the case on a corporate
    Intranet), you can require plain certificate authentication. All you
    need to do is to create client certificates signed by your own CA
    certificate (<code>ca.crt</code>) and then verify the clients against this
    certificate.</p>
    <highlight language="config">
# require a client certificate which has to be directly
# signed by our CA certificate in ca.crt
SSLVerifyClient require
SSLVerifyDepth 1
SSLCACertificateFile conf/ssl.crt/ca.crt
    </highlight>
</section>

<section id="arbitraryclients">
<title>How can I force clients to authenticate using certificates for a
  particular URL, but still allow arbitrary clients to access the rest of the server?</title>

    <p>To force clients to authenticate using certificates for a particular URL,
    you can use the per-directory reconfiguration features of
    <module>mod_ssl</module>:</p>

    <highlight language="config">
SSLVerifyClient none
SSLCACertificateFile conf/ssl.crt/ca.crt

&lt;Location /secure/area&gt;
SSLVerifyClient require
SSLVerifyDepth 1
&lt;/Location&gt;
    </highlight>
</section>

<section id="certauthenticate">
<title>How can I allow only clients who have certificates to access a
  particular URL, but allow all clients to access the rest of the server?</title>

    <p>The key to doing this is checking that part of the client certificate
    matches what you expect. Usually this means checking all or part of the
    Distinguished Name (DN), to see if it contains some known string.
    There are two ways to do this, using either <module>mod_auth_basic</module> or
    <directive module="mod_ssl">SSLRequire</directive>.</p>

    <p>The <module>mod_auth_basic</module> method is generally required when
    the certificates are completely arbitrary, or when their DNs have
    no common fields (usually the organisation, etc.). In this case,
    you should establish a password database containing <em>all</em>
    clients allowed, as follows:</p>

    <highlight language="config">
SSLVerifyClient      none
SSLCACertificateFile conf/ssl.crt/ca.crt
SSLCACertificatePath conf/ssl.crt

&lt;Directory /usr/local/apache2/htdocs/secure/area&gt;
    SSLVerifyClient      require
    SSLVerifyDepth       5
    SSLOptions           +FakeBasicAuth
    SSLRequireSSL
    AuthName             "Snake Oil Authentication"
    AuthType             Basic
    AuthBasicProvider    file
    AuthUserFile         /usr/local/apache2/conf/httpd.passwd
    Require              valid-user
&lt;/Directory&gt;
    </highlight>

    <p>The password used in this example is the DES encrypted string "password".
    See the <directive module="mod_ssl">SSLOptions</directive> docs for more
    information.</p>

    <example><title>httpd.passwd</title><pre>
/C=DE/L=Munich/O=Snake Oil, Ltd./OU=Staff/CN=Foo:xxj31ZMTZzkVA
/C=US/L=S.F./O=Snake Oil, Ltd./OU=CA/CN=Bar:xxj31ZMTZzkVA
/C=US/L=L.A./O=Snake Oil, Ltd./OU=Dev/CN=Quux:xxj31ZMTZzkVA</pre>
    </example>

    <p>When your clients are all part of a common hierarchy, which is encoded
    into the DN, you can match them more easily using <directive module="mod_ssl"
    >SSLRequire</directive>, as follows:</p>


    <highlight language="config">
SSLVerifyClient      none
SSLCACertificateFile conf/ssl.crt/ca.crt
SSLCACertificatePath conf/ssl.crt

&lt;Directory /usr/local/apache2/htdocs/secure/area&gt;
  SSLVerifyClient      require
  SSLVerifyDepth       5
  SSLOptions           +FakeBasicAuth
  SSLRequireSSL
  SSLRequire       %{SSL_CLIENT_S_DN_O}  eq "Snake Oil, Ltd." \
               and %{SSL_CLIENT_S_DN_OU} in {"Staff", "CA", "Dev"}
&lt;/Directory&gt;
    </highlight>
</section>

<section id="intranet">
<title>How can I require HTTPS with strong ciphers, and either basic
authentication or client certificates, for access to part of the
Intranet website, for clients coming from the Internet? I still want to allow
plain HTTP access for clients on the Intranet.</title>

   <p>These examples presume that clients on the Intranet have IPs in the range
   192.168.1.0/24, and that the part of the Intranet website you want to allow
   internet access to is <code>/usr/local/apache2/htdocs/subarea</code>.
   This configuration should remain outside of your HTTPS virtual host, so
   that it applies to both HTTPS and HTTP.</p>

    <highlight language="config">
SSLCACertificateFile conf/ssl.crt/company-ca.crt

&lt;Directory /usr/local/apache2/htdocs&gt;
    #   Outside the subarea only Intranet access is granted
    Require              ip 192.168.1.0/24
&lt;/Directory&gt;

&lt;Directory /usr/local/apache2/htdocs/subarea&gt;
    #   Inside the subarea any Intranet access is allowed
    #   but from the Internet only HTTPS + Strong-Cipher + Password
    #   or the alternative HTTPS + Strong-Cipher + Client-Certificate
    
    #   If HTTPS is used, make sure a strong cipher is used.
    #   Additionally allow client certs as alternative to basic auth.
    SSLVerifyClient      optional
    SSLVerifyDepth       1
    SSLOptions           +FakeBasicAuth +StrictRequire
    SSLRequire           %{SSL_CIPHER_USEKEYSIZE} &gt;= 128
    
    #   Force clients from the Internet to use HTTPS
    RewriteEngine        on
    RewriteCond          %{REMOTE_ADDR} !^192\.168\.1\.[0-9]+$
    RewriteCond          %{HTTPS} !=on
    RewriteRule          . - [F]
    
    #   Allow Network Access and/or Basic Auth
    Satisfy              any
    
    #   Network Access Control
    Require              ip 192.168.1.0/24
    
    #   HTTP Basic Authentication
    AuthType             basic
    AuthName             "Protected Intranet Area"
    AuthBasicProvider    file
    AuthUserFile         conf/protected.passwd
    Require              valid-user
&lt;/Directory&gt;
    </highlight>
</section>
</section>
<!-- /access control -->

<section id="logging">
    <title>Logging</title>

    <p><module>mod_ssl</module> can log extremely verbose debugging information
    to the error log, when its <directive module="core">LogLevel</directive> is
    set to the higher trace levels. On the other hand, on a very busy server,
    level <code>info</code> may already be too much. Remember that you can
    configure the <directive module="core">LogLevel</directive> per module to
    suite your needs.</p>
</section>

</manualpage>

