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<p class="menu"><a href="/mod/">Modules</a> | <a href="/mod/directives.html">Directives</a> | <a href="/faq/">FAQ</a> | <a href="/glossary.html">Glossary</a> | <a href="/sitemap.html">Sitemap</a></p>
<p class="apache">Apache HTTP Server Version 2.5</p>
<div id="path">
<a href="http://www.apache.org/">Apache</a> > <a href="http://httpd.apache.org/">HTTP Server</a> > <a href="http://httpd.apache.org/docs/">Documentation</a> > <a href="../">Version 2.5</a> > <a href="./">SSL/TLS</a></div><div id="page-content"><div id="preamble"><h1>SSL/TLS Strong Encryption: How-To</h1>
<div class="toplang">
<p><span>Available Languages: </span><a href="/en/ssl/ssl_howto.html" title="English"> en </a> |
<a href="/fr/ssl/ssl_howto.html" hreflang="fr" rel="alternate" title="Fran�ais"> fr </a></p>
</div>
<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>
</div>
<div id="quickview"><ul id="toc"><li><img alt="" src="/images/down.gif" /> <a href="#configexample">Basic Configuration Example</a></li>
<li><img alt="" src="/images/down.gif" /> <a href="#ciphersuites">Cipher Suites and Enforcing Strong Security</a></li>
<li><img alt="" src="/images/down.gif" /> <a href="#accesscontrol">Client Authentication and Access Control</a></li>
</ul></div>
<div class="section">
<h2><a name="configexample" id="configexample">Basic Configuration Example</a></h2>
<p>Your SSL configuration will need to contain, at minimum, the
following directives.</p>
<div class="example"><p><code>
Listen 443<br />
<VirtualHost *:443><br />
<span class="indent">
ServerName www.example.com<br />
SSLEngine on<br />
</span>
</VirtualHost>
</code></p></div>
<div class="section">
<h2><a name="ciphersuites" id="ciphersuites">Cipher Suites and Enforcing Strong Security</a></h2>
<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>
<h3><a name="onlystrong" id="onlystrong">How can I create an SSL server which accepts strong encryption
only?</a></h3>
<p>The following enables only the strongest ciphers:</p>
SSLCipherSuite HIGH:!aNULL:!MD5<br />
</code></p></div>
<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>
SSLCipherSuite RC4-SHA:AES128-SHA:HIGH:!aNULL:!MD5<br />
SSLHonorCipherOrder on
</code></p></div>
<h3><a name="strongurl" id="strongurl">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?</a></h3>
<p>Obviously, a server-wide <code class="directive"><a href="/mod/mod_ssl.html#sslciphersuite">SSLCipherSuite</a></code> which restricts
ciphers to the strong variants, isn't the answer here. However,
<code class="module"><a href="/mod/mod_ssl.html">mod_ssl</a></code> 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>
<div class="example"><p><code>
# be liberal in general<br />
SSLCipherSuite ALL:!aNULL:RC4+RSA:+HIGH:+MEDIUM:+LOW:+EXP:+eNULL<br />
<br />
# but https://hostname/strong/area/ and below<br />
# requires strong ciphers<br />
SSLCipherSuite HIGH:!aNULL:!MD5<br />
</Location>
</code></p></div>
<div class="section">
<h2><a name="accesscontrol" id="accesscontrol">Client Authentication and Access Control</a></h2>
<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>
<h3><a name="allclients" id="allclients">How can I force clients to authenticate using certificates?</a></h3>
<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.</p>
# require a client certificate which has to be directly<br />
# signed by our CA certificate in ca.crt<br />
SSLVerifyClient require<br />
SSLVerifyDepth 1<br />
</code></p></div>
<h3><a name="arbitraryclients" id="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></h3>
<p>To force clients to authenticate using certificates for a particular URL,
you can use the per-directory reconfiguration features of
SSLVerifyClient none<br />
<br />
SSLVerifyClient require<br />
SSLVerifyDepth 1<br />
</Location><br />
</code></p></div>
<h3><a name="certauthenticate" id="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></h3>
<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 <code class="module"><a href="/mod/mod_auth_basic.html">mod_auth_basic</a></code> or
<p>The <code class="module"><a href="/mod/mod_auth_basic.html">mod_auth_basic</a></code> 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>
SSLVerifyClient none
SSLVerifyClient require
SSLVerifyDepth 5
SSLOptions +FakeBasicAuth
SSLRequireSSL
AuthName "Snake Oil Authentication"
AuthType Basic
AuthBasicProvider file
Require valid-user
</Directory></pre></div>
<p>The password used in this example is the DES encrypted string "password".
See the <code class="directive"><a href="/mod/mod_ssl.html#ssloptions">SSLOptions</a></code> docs for more
information.</p>
<p>When your clients are all part of a common hierarchy, which is encoded
into the DN, you can match them more easily using <code class="directive"><a href="/mod/mod_ssl.html#sslrequire">SSLRequire</a></code>, as follows:</p>
SSLVerifyClient none
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"}
</Directory></pre></div>
<h3><a name="intranet" id="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? I still want to allow
plain HTTP access for clients on the Intranet.</a></h3>
<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
This configuration should remain outside of your HTTPS virtual host, so
that it applies to both HTTPS and HTTP.</p>
# Outside the subarea only Intranet access is granted
Order deny,allow
Deny from all
Allow from 192.168.1.0/24
</Directory>
# 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} >= 128
# Force clients from the Internet to use HTTPS
RewriteEngine on
RewriteCond %{REMOTE_ADDR} !^192\.168\.1\.[0-9]+$
RewriteCond %{HTTPS} !=on
RewriteRule . - [F]
Satisfy any
# Network Access Control
Order deny,allow
Deny from all
Allow 192.168.1.0/24
# HTTP Basic Authentication
AuthType basic
AuthName "Protected Intranet Area"
AuthBasicProvider file
AuthUserFile conf/protected.passwd
Require valid-user
</Directory></pre></div>
<div class="section">
<h2><a name="logging" id="logging">Logging</a></h2>
<p><code class="module"><a href="/mod/mod_ssl.html">mod_ssl</a></code> can log extremely verbose debugging information
to the error log, when its <code class="directive"><a href="/mod/core.html#loglevel">LogLevel</a></code> 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 <code class="directive"><a href="/mod/core.html#loglevel">LogLevel</a></code> per module to
suite your needs.</p>
</div></div>
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