1<?xml version="1.0" encoding="ISO-8859-1"?> 2<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> 3<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head><!-- 4 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 5 This file is generated from xml source: DO NOT EDIT 6 XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX 7 --> 8<title>SSL/TLS Strong Encryption: How-To - Apache HTTP Server</title> 9<link href="/style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" /> 10<link href="/style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" /> 11<link href="/style/css/manual-print.css" rel="stylesheet" media="print" type="text/css" /><link rel="stylesheet" type="text/css" href="/style/css/prettify.css" /> 12<script src="/style/scripts/prettify.js" type="text/javascript"> 13</script> 14 15<link href="/images/favicon.ico" rel="shortcut icon" /></head> 16<body id="manual-page"><div id="page-header"> 17<p class="menu"><a href="/mod/">Modules</a> | <a href="/mod/directives.html">Directives</a> | <a href="http://wiki.apache.org/httpd/FAQ">FAQ</a> | <a href="/glossary.html">Glossary</a> | <a href="/sitemap.html">Sitemap</a></p> 18<p class="apache">Apache HTTP Server Version 2.2</p> 19<img alt="" src="/images/feather.gif" /></div> 20<div class="up"><a href="./"><img title="<-" alt="<-" src="/images/left.gif" /></a></div> 21<div id="path"> 22<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 2.2</a> > <a href="./">SSL/TLS</a></div><div id="page-content"><div id="preamble"><h1>SSL/TLS Strong Encryption: How-To</h1> 23<div class="toplang"> 24<p><span>Available Languages: </span><a href="/en/ssl/ssl_howto.html" title="English"> en </a></p> 25</div> 26 27<blockquote> 28<p>The solution to this problem is trivial 29and is left as an exercise for the reader.</p> 30 31<p class="cite">-- <cite>Standard textbook cookie</cite></p> 32</blockquote> 33 34<p>How to solve particular security problems for an SSL-aware 35webserver is not always obvious because of the interactions between SSL, 36HTTP and Apache's way of processing requests. This chapter gives 37instructions on how to solve some typical situations. Treat it as a first 38step to find out the final solution, but always try to understand the 39stuff before you use it. Nothing is worse than using a security solution 40without knowing its restrictions and how it interacts with other systems.</p> 41</div> 42<div id="quickview"><ul id="toc"><li><img alt="" src="/images/down.gif" /> <a href="#ciphersuites">Cipher Suites and Enforcing Strong Security</a></li> 43<li><img alt="" src="/images/down.gif" /> <a href="#accesscontrol">Client Authentication and Access Control</a></li> 44</ul><ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div> 45<div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 46<div class="section"> 47<h2><a name="ciphersuites" id="ciphersuites">Cipher Suites and Enforcing Strong Security</a></h2> 48 49<ul> 50<li><a href="#realssl">How can I create a real SSLv2-only server?</a></li> 51<li><a href="#onlystrong">How can I create an SSL server which accepts strong encryption only?</a></li> 52<li><a href="#upgradeenc">How can I create an SSL server which accepts strong encryption only, but allows 53export browsers to upgrade to stronger encryption?</a></li> 54<li><a href="#strongurl">How can I create an SSL server which accepts all types of ciphers in general, but 55requires a strong cipher for access to a particular URL?</a></li> 56</ul> 57 58<h3><a name="realssl" id="realssl">How can I create a real SSLv2-only server?</a></h3> 59 60 <p>The following creates an SSL server which speaks only the SSLv2 protocol and 61 its ciphers.</p> 62 63 <div class="example"><h3>httpd.conf</h3><p><code> 64 SSLProtocol -all +SSLv2<br /> 65 SSLCipherSuite SSLv2:+HIGH:+MEDIUM:+LOW:+EXP<br /> 66 </code></p></div> 67 68 69<h3><a name="onlystrong" id="onlystrong">How can I create an SSL server which accepts strong encryption 70only?</a></h3> 71 72 <p>The following enables only the seven strongest ciphers:</p> 73 <div class="example"><h3>httpd.conf</h3><p><code> 74 SSLProtocol all<br /> 75 SSLCipherSuite HIGH:MEDIUM<br /> 76 </code></p></div> 77 78 79<h3><a name="upgradeenc" id="upgradeenc">How can I create an SSL server which accepts strong encryption 80only, but allows export browsers to upgrade to stronger encryption?</a></h3> 81 82 <p>This facility is called Server Gated Cryptography (SGC) and requires 83 a Global ID server certificate, signed by a special CA certificate 84 from Verisign. This enables strong encryption in 'export' versions of 85 browsers, which traditionally could not support it (because of US export 86 restrictions).</p> 87 <p>When a browser connects with an export cipher, the server sends its Global 88 ID certificate. The browser verifies this, and can then upgrade its 89 cipher suite before any HTTP communication takes place. The problem 90 lies in allowing browsers to upgrade in this fashion, but still requiring 91 strong encryption. In other words, we want browsers to either start a 92 connection with strong encryption, or to start with export ciphers but 93 upgrade to strong encryption before beginning HTTP communication.</p> 94 <p>This can be done as follows:</p> 95 <div class="example"><h3>httpd.conf</h3><p><code> 96 # allow all ciphers for the initial handshake,<br /> 97 # so export browsers can upgrade via SGC facility<br /> 98 SSLCipherSuite ALL:!ADH:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP:+eNULL<br /> 99 <br /> 100 <Directory /usr/local/apache2/htdocs><br /> 101 # but finally deny all browsers which haven't upgraded<br /> 102 SSLRequire %{SSL_CIPHER_USEKEYSIZE} >= 128<br /> 103 </Directory> 104 </code></p></div> 105 106 107<h3><a name="strongurl" id="strongurl">How can I create an SSL server which accepts all types of ciphers 108in general, but requires a strong ciphers for access to a particular 109URL?</a></h3> 110 111 <p>Obviously, a server-wide <code class="directive"><a href="/mod/mod_ssl.html#sslciphersuite">SSLCipherSuite</a></code> which restricts 112 ciphers to the strong variants, isn't the answer here. However, 113 <code class="module"><a href="/mod/mod_ssl.html">mod_ssl</a></code> can be reconfigured within <code>Location</code> 114 blocks, to give a per-directory solution, and can automatically force 115 a renegotiation of the SSL parameters to meet the new configuration. 116 This can be done as follows:</p> 117 <div class="example"><p><code> 118 # be liberal in general<br /> 119 SSLCipherSuite ALL:!ADH:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP:+eNULL<br /> 120 <br /> 121 <Location /strong/area><br /> 122 # but https://hostname/strong/area/ and below<br /> 123 # requires strong ciphers<br /> 124 SSLCipherSuite HIGH:MEDIUM<br /> 125 </Location> 126 </code></p></div> 127 128</div><div class="top"><a href="#page-header"><img alt="top" src="/images/up.gif" /></a></div> 129<div class="section"> 130<h2><a name="accesscontrol" id="accesscontrol">Client Authentication and Access Control</a></h2> 131 132<ul> 133<li><a href="#allclients">How can I force clients to authenticate using certificates?</a></li> 134<li><a href="#arbitraryclients">How can I force clients to authenticate using certificates for a 135 particular URL, but still allow arbitrary clients to access the rest of the server?</a></li> 136<li><a href="#certauthenticate">How can I allow only clients who have certificates to access a 137 particular URL, but allow all clients to access the rest of the server?</a></li> 138<li><a href="#intranet">How can I require HTTPS with strong ciphers, and either 139basic authentication or client certificates, for access to part of the 140Intranet website, for clients coming from the Internet?</a></li> 141</ul> 142 143<h3><a name="allclients" id="allclients">How can I force clients to authenticate using certificates?</a></h3> 144 145 146 <p>When you know all of your users (eg, as is often the case on a corporate 147 Intranet), you can require plain certificate authentication. All you 148 need to do is to create client certificates signed by your own CA 149 certificate (<code>ca.crt</code>) and then verify the clients against this 150 certificate.</p> 151 <div class="example"><h3>httpd.conf</h3><p><code> 152 # require a client certificate which has to be directly<br /> 153 # signed by our CA certificate in ca.crt<br /> 154 SSLVerifyClient require<br /> 155 SSLVerifyDepth 1<br /> 156 SSLCACertificateFile conf/ssl.crt/ca.crt 157 </code></p></div> 158 159 160<h3><a name="arbitraryclients" id="arbitraryclients">How can I force clients to authenticate using certificates for a 161 particular URL, but still allow arbitrary clients to access the rest of the server?</a></h3> 162 163 164<p>To force clients to authenticate using certificates for a particular URL, 165 you can use the per-directory reconfiguration features of <code class="module"><a href="/mod/mod_ssl.html">mod_ssl</a></code>:</p> 166 167 <div class="example"><h3>httpd.conf</h3><p><code> 168 SSLVerifyClient none<br /> 169 SSLCACertificateFile conf/ssl.crt/ca.crt<br /> 170 <br /> 171 <Location /secure/area><br /> 172 SSLVerifyClient require<br /> 173 SSLVerifyDepth 1<br /> 174 </Location><br /> 175 </code></p></div> 176 177 178<h3><a name="certauthenticate" id="certauthenticate">How can I allow only clients who have certificates to access a 179 particular URL, but allow all clients to access the rest of the server?</a></h3> 180 181 182 <p>The key to doing this is checking that part of the client certificate 183 matches what you expect. Usually this means checking all or part of the 184 Distinguished Name (DN), to see if it contains some known string. 185 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 186 <code class="directive"><a href="/mod/mod_ssl.html#sslrequire">SSLRequire</a></code>.</p> 187 188 <p>The <code class="module"><a href="/mod/mod_auth_basic.html">mod_auth_basic</a></code> method is generally required when 189 the certificates are completely arbitrary, or when their DNs have 190 no common fields (usually the organisation, etc.). In this case, 191 you should establish a password database containing <em>all</em> 192 clients allowed, as follows:</p> 193 194 <div class="example"><h3>httpd.conf</h3><pre> 195SSLCACertificateFile conf/ssl.crt/ca.crt 196SSLCACertificatePath conf/ssl.crt 197SSLVerifyClient none 198 199<Directory /usr/local/apache2/htdocs/secure/area> 200SSLVerifyClient require 201SSLVerifyDepth 5 202SSLOptions +FakeBasicAuth 203SSLRequireSSL 204AuthName "Snake Oil Authentication" 205AuthType Basic 206AuthBasicProvider file 207AuthUserFile /usr/local/apache2/conf/httpd.passwd 208Require valid-user 209</Directory></pre></div> 210 211 <p>The password used in this example is the DES encrypted string "password". 212 See the <code class="directive"><a href="/mod/mod_ssl.html#ssloptions">SSLOptions</a></code> docs for more 213 information.</p> 214 215 <div class="example"><h3>httpd.passwd</h3><pre> 216/C=DE/L=Munich/O=Snake Oil, Ltd./OU=Staff/CN=Foo:xxj31ZMTZzkVA 217/C=US/L=S.F./O=Snake Oil, Ltd./OU=CA/CN=Bar:xxj31ZMTZzkVA 218/C=US/L=L.A./O=Snake Oil, Ltd./OU=Dev/CN=Quux:xxj31ZMTZzkVA</pre></div> 219 220 <p>When your clients are all part of a common hierarchy, which is encoded 221 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> 222 223 224 <div class="example"><h3>httpd.conf</h3><pre> 225SSLVerifyClient none 226SSLCACertificateFile conf/ssl.crt/ca.crt 227SSLCACertificatePath conf/ssl.crt 228 229<Directory /usr/local/apache2/htdocs/secure/area> 230 SSLVerifyClient require 231 SSLVerifyDepth 5 232 SSLOptions +FakeBasicAuth 233 SSLRequireSSL 234 SSLRequire %{SSL_CLIENT_S_DN_O} eq "Snake Oil, Ltd." \ 235 and %{SSL_CLIENT_S_DN_OU} in {"Staff", "CA", "Dev"} 236</Directory></pre></div> 237 238 239<h3><a name="intranet" id="intranet">How can I require HTTPS with strong ciphers, and either basic 240authentication or client certificates, for access to part of the 241Intranet website, for clients coming from the Internet? I still want to allow 242plain HTTP access for clients on the Intranet.</a></h3> 243 244 245 <p>These examples presume that clients on the Intranet have IPs in the range 246 192.168.1.0/24, and that the part of the Intranet website you want to allow 247 internet access to is <code>/usr/local/apache2/htdocs/subarea</code>. 248 This configuration should remain outside of your HTTPS virtual host, so 249 that it applies to both HTTPS and HTTP.</p> 250 251 <div class="example"><h3>httpd.conf</h3><pre> 252SSLCACertificateFile conf/ssl.crt/company-ca.crt 253 254<Directory /usr/local/apache2/htdocs> 255# Outside the subarea only Intranet access is granted 256Order deny,allow 257Deny from all 258Allow from 192.168.1.0/24 259</Directory> 260 261<Directory /usr/local/apache2/htdocs/subarea> 262# Inside the subarea any Intranet access is allowed 263# but from the Internet only HTTPS + Strong-Cipher + Password 264# or the alternative HTTPS + Strong-Cipher + Client-Certificate 265 266# If HTTPS is used, make sure a strong cipher is used. 267# Additionally allow client certs as alternative to basic auth. 268SSLVerifyClient optional 269SSLVerifyDepth 1 270SSLOptions +FakeBasicAuth +StrictRequire 271SSLRequire %{SSL_CIPHER_USEKEYSIZE} >= 128 272 273# Force clients from the Internet to use HTTPS 274RewriteEngine on 275RewriteCond %{REMOTE_ADDR} !^192\.168\.1\.[0-9]+$ 276RewriteCond %{HTTPS} !=on 277RewriteRule .* - [F] 278 279# Allow Network Access and/or Basic Auth 280Satisfy any 281 282# Network Access Control 283Order deny,allow 284Deny from all 285Allow 192.168.1.0/24 286 287# HTTP Basic Authentication 288AuthType basic 289AuthName "Protected Intranet Area" 290AuthBasicProvider file 291AuthUserFile conf/protected.passwd 292Require valid-user 293</Directory></pre></div> 294 295</div></div> 296<div class="bottomlang"> 297<p><span>Available Languages: </span><a href="/en/ssl/ssl_howto.html" title="English"> en </a></p> 298</div><div class="top"><a href="#page-header"><img src="/images/up.gif" alt="top" /></a></div><div class="section"><h2><a id="comments_section" name="comments_section">Comments</a></h2><div class="warning"><strong>Notice:</strong><br />This is not a Q&A section. 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