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| author | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 15:01:30 +0000 |
|---|---|---|
| committer | Daniel Baumann <daniel.baumann@progress-linux.org> | 2024-04-07 15:01:30 +0000 |
| commit | 6beeb1b708550be0d4a53b272283e17e5e35fe17 (patch) | |
| tree | 1ce8673d4aaa948e5554000101f46536a1e4cc29 /docs/manual/ssl/ssl_faq.html.en | |
| parent | Initial commit. (diff) | |
| download | apache2-3d46059c28a1d66e6e1aeb209491f1324c913a25.tar.xz apache2-3d46059c28a1d66e6e1aeb209491f1324c913a25.zip | |
Adding upstream version 2.4.57.upstream/2.4.57
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
Diffstat (limited to 'docs/manual/ssl/ssl_faq.html.en')
| -rw-r--r-- | docs/manual/ssl/ssl_faq.html.en | 935 |
1 files changed, 935 insertions, 0 deletions
diff --git a/docs/manual/ssl/ssl_faq.html.en b/docs/manual/ssl/ssl_faq.html.en new file mode 100644 index 0000000..a95b4e1 --- /dev/null +++ b/docs/manual/ssl/ssl_faq.html.en @@ -0,0 +1,935 @@ +<?xml version="1.0" encoding="UTF-8"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> +<html xmlns="http://www.w3.org/1999/xhtml" lang="en" xml:lang="en"><head> +<meta content="text/html; charset=UTF-8" http-equiv="Content-Type" /> +<!-- + XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX + This file is generated from xml source: DO NOT EDIT + XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX + --> +<title>SSL/TLS Strong Encryption: FAQ - Apache HTTP Server Version 2.4</title> +<link href="../style/css/manual.css" rel="stylesheet" media="all" type="text/css" title="Main stylesheet" /> +<link href="../style/css/manual-loose-100pc.css" rel="alternate stylesheet" media="all" type="text/css" title="No Sidebar - Default font size" /> +<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" /> +<script src="../style/scripts/prettify.min.js" type="text/javascript"> +</script> + +<link href="../images/favicon.ico" rel="shortcut icon" /></head> +<body id="manual-page"><div id="page-header"> +<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> +<p class="apache">Apache HTTP Server Version 2.4</p> +<img alt="" src="../images/feather.png" /></div> +<div class="up"><a href="./"><img title="<-" alt="<-" src="../images/left.gif" /></a></div> +<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 2.4</a> > <a href="./">SSL/TLS</a></div><div id="page-content"><div id="preamble"><h1>SSL/TLS Strong Encryption: FAQ</h1> +<div class="toplang"> +<p><span>Available Languages: </span><a href="../en/ssl/ssl_faq.html" title="English"> en </a> | +<a href="../fr/ssl/ssl_faq.html" hreflang="fr" rel="alternate" title="Français"> fr </a></p> +</div> + +<blockquote> +<p>The wise man doesn't give the right answers, +he poses the right questions.</p> +<p class="cite">-- <cite>Claude Levi-Strauss</cite></p> + +</blockquote> +</div> +<div id="quickview"><a href="https://www.apache.org/foundation/contributing.html" class="badge"><img src="https://www.apache.org/images/SupportApache-small.png" alt="Support Apache!" /></a><ul id="toc"><li><img alt="" src="../images/down.gif" /> <a href="#installation">Installation</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#aboutconfig">Configuration</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#aboutcerts">Certificates</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#aboutssl">The SSL Protocol</a></li> +<li><img alt="" src="../images/down.gif" /> <a href="#support">mod_ssl Support</a></li> +</ul><h3>See also</h3><ul class="seealso"><li><a href="#comments_section">Comments</a></li></ul></div> +<div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="section"> +<h2><a name="installation" id="installation">Installation</a></h2> +<ul> +<li><a href="#mutex">Why do I get permission errors related to +SSLMutex when I start Apache?</a></li> +<li><a href="#entropy">Why does mod_ssl stop with the error "Failed to +generate temporary 512 bit RSA private key" when I start Apache?</a></li> +</ul> + +<h3><a name="mutex" id="mutex">Why do I get permission errors related to + SSLMutex when I start Apache?</a></h3> + <p>Errors such as ``<code>mod_ssl: Child could not open + SSLMutex lockfile /opt/apache/logs/ssl_mutex.18332 (System error follows) + [...] System: Permission denied (errno: 13)</code>'' are usually + caused by overly restrictive permissions on the <em>parent</em> directories. + Make sure that all parent directories (here <code>/opt</code>, + <code>/opt/apache</code> and <code>/opt/apache/logs</code>) have the x-bit + set for, at minimum, the UID under which Apache's children are running (see + the <code class="directive"><a href="../mod/mod_unixd.html#user">User</a></code> directive).</p> + + +<h3><a name="entropy" id="entropy">Why does mod_ssl stop with the error + "Failed to generate temporary 512 bit RSA private key" when I start + Apache?</a></h3> + <p>Cryptographic software needs a source of unpredictable data + to work correctly. Many open source operating systems provide + a "randomness device" that serves this purpose (usually named + <code>/dev/random</code>). On other systems, applications have to + seed the OpenSSL Pseudo Random Number Generator (PRNG) manually with + appropriate data before generating keys or performing public key + encryption. As of version 0.9.5, the OpenSSL functions that need + randomness report an error if the PRNG has not been seeded with + at least 128 bits of randomness.</p> + <p>To prevent this error, <code class="module"><a href="../mod/mod_ssl.html">mod_ssl</a></code> has to provide + enough entropy to the PRNG to allow it to work correctly. This can + be done via the <code class="directive"><a href="../mod/mod_ssl.html#sslrandomseed">SSLRandomSeed</a></code> + directive.</p> + +</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="section"> +<h2><a name="aboutconfig" id="aboutconfig">Configuration</a></h2> +<ul> +<li><a href="#parallel">Is it possible to provide HTTP and HTTPS from +the same server?</a></li> +<li><a href="#ports">Which port does HTTPS use?</a></li> +<li><a href="#httpstest">How do I speak HTTPS manually for testing +purposes?</a></li> +<li><a href="#hang">Why does the connection hang when I connect to my +SSL-aware Apache server?</a></li> +<li><a href="#refused">Why do I get ``Connection Refused'' errors, when +trying to access my newly installed Apache+mod_ssl server via HTTPS?</a></li> +<li><a href="#envvars">Why are the <code>SSL_XXX</code> variables not +available to my CGI & SSI scripts?</a></li> +<li><a href="#relative">How can I switch between HTTP and HTTPS in +relative hyperlinks?</a></li> +</ul> + +<h3><a name="parallel" id="parallel">Is it possible to provide HTTP and HTTPS + from the same server?</a></h3> + <p>Yes. HTTP and HTTPS use different server ports (HTTP binds to + port 80, HTTPS to port 443), so there is no direct conflict between + them. You can either run two separate server instances bound to + these ports, or use Apache's elegant virtual hosting facility to + create two virtual servers, both served by the same instance of Apache + - one responding over HTTP to requests on port 80, and the other + responding over HTTPS to requests on port 443.</p> + + +<h3><a name="ports" id="ports">Which port does HTTPS use?</a></h3> +<p>You can run HTTPS on any port, but the standards specify port 443, which + is where any HTTPS compliant browser will look by default. You can force + your browser to look on a different port by specifying it in the URL. For + example, if your server is set up to serve pages over HTTPS on port 8080, + you can access them at <code>https://example.com:8080/</code></p> + + +<h3><a name="httpstest" id="httpstest">How do I speak HTTPS manually for testing purposes?</a></h3> + <p>While you usually just use</p> + + <div class="example"><p><code>$ telnet localhost 80<br /> + GET / HTTP/1.0</code></p></div> + + <p>for simple testing of Apache via HTTP, it's not so easy for + HTTPS because of the SSL protocol between TCP and HTTP. With the + help of OpenSSL's <code>s_client</code> command, however, you can + do a similar check via HTTPS:</p> + + <div class="example"><p><code>$ openssl s_client -connect localhost:443 -state -debug<br /> + GET / HTTP/1.0</code></p></div> + + <p>Before the actual HTTP response you will receive detailed + information about the SSL handshake. For a more general command + line client which directly understands both HTTP and HTTPS, can + perform GET and POST operations, can use a proxy, supports byte + ranges, etc. you should have a look at the nifty + <a href="http://curl.haxx.se/">cURL</a> tool. Using this, you can + check that Apache is responding correctly to requests via HTTP and + HTTPS as follows:</p> + + <div class="example"><p><code>$ curl http://localhost/<br /> + $ curl https://localhost/</code></p></div> + + +<h3><a name="hang" id="hang">Why does the connection hang when I connect + to my SSL-aware Apache server?</a></h3> + +<p>This can happen when you try to connect to a HTTPS server (or virtual + server) via HTTP (eg, using <code>http://example.com/</code> instead of + <code>https://example.com</code>). It can also happen when trying to + connect via HTTPS to a HTTP server (eg, using + <code>https://example.com/</code> on a server which doesn't support HTTPS, + or which supports it on a non-standard port). Make sure that you're + connecting to a (virtual) server that supports SSL.</p> + +<h3><a name="refused" id="refused">Why do I get ``Connection Refused'' messages, + when trying to access my newly installed Apache+mod_ssl server via HTTPS?</a></h3> +<p> + This error can be caused by an incorrect configuration. + Please make sure that your <code class="directive"><a href="../mod/mpm_common.html#listen">Listen</a></code> directives match your + <code class="directive"><a href="../mod/core.html#virtualhost"><VirtualHost></a></code> + directives. If all else fails, please start afresh, using the default + configuration provided by <code class="module"><a href="../mod/mod_ssl.html">mod_ssl</a></code>.</p> + + +<h3><a name="envvars" id="envvars">Why are the <code>SSL_XXX</code> variables + not available to my CGI & SSI scripts?</a></h3> +<p>Please make sure you have ``<code>SSLOptions +StdEnvVars</code>'' + enabled for the context of your CGI/SSI requests.</p> + + +<h3><a name="relative" id="relative">How can I switch between HTTP and HTTPS in relative + hyperlinks?</a></h3> + +<p>Usually, to switch between HTTP and HTTPS, you have to use + fully-qualified hyperlinks (because you have to change the URL + scheme). Using <code class="module"><a href="../mod/mod_rewrite.html">mod_rewrite</a></code> however, you can + manipulate relative hyperlinks, to achieve the same effect.</p> + <pre class="prettyprint lang-config">RewriteEngine on +RewriteRule "^/(.*)_SSL$" "https://%{SERVER_NAME}/$1" [R,L] +RewriteRule "^/(.*)_NOSSL$" "http://%{SERVER_NAME}/$1" [R,L]</pre> + + + <p>This rewrite ruleset lets you use hyperlinks of the form + <code><a href="document.html_SSL"></code>, to switch to HTTPS + in a relative link. (Replace SSL with NOSSL to switch to HTTP.)</p> + +</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="section"> +<h2><a name="aboutcerts" id="aboutcerts">Certificates</a></h2> +<ul> +<li><a href="#keyscerts">What are RSA Private Keys, CSRs and +Certificates?</a></li> +<li><a href="#startup">Is there a difference on startup between +a non-SSL-aware Apache and an SSL-aware Apache?</a></li> +<li><a href="#selfcert">How do I create a self-signed SSL +Certificate for testing purposes?</a></li> +<li><a href="#realcert">How do I create a real SSL Certificate?</a></li> +<li><a href="#ownca">How do I create and use my own Certificate +Authority (CA)?</a></li> +<li><a href="#passphrase">How can I change the pass-phrase on my private +key file?</a></li> +<li><a href="#removepassphrase">How can I get rid of the pass-phrase +dialog at Apache startup time?</a></li> +<li><a href="#verify">How do I verify that a private key matches its +Certificate?</a></li> +<li><a href="#pemder">How can I convert a certificate from PEM to DER +format?</a></li> +<li><a href="#gid">Why do browsers complain that they cannot +verify my server certificate?</a></li> +</ul> + +<h3><a name="keyscerts" id="keyscerts">What are RSA Private Keys, CSRs and Certificates?</a></h3> +<p>An RSA private key file is a digital file that you can use to decrypt + messages sent to you. It has a public component which you distribute (via + your Certificate file) which allows people to encrypt those messages to + you.</p> + <p>A Certificate Signing Request (CSR) is a digital file which contains + your public key and your name. You send the CSR to a Certifying Authority + (CA), who will convert it into a real Certificate, by signing it.</p> + <p>A Certificate contains your + RSA public key, your name, the name of the CA, and is digitally signed by + the CA. Browsers that know the CA can verify the signature on that + Certificate, thereby obtaining your RSA public key. That enables them to + send messages which only you can decrypt.</p> + <p>See the <a href="ssl_intro.html">Introduction</a> chapter for a general + description of the SSL protocol.</p> + + +<h3><a name="startup" id="startup">Is there a difference on startup between + a non-SSL-aware Apache and an SSL-aware Apache?</a></h3> +<p>Yes. In general, starting Apache with + <code class="module"><a href="../mod/mod_ssl.html">mod_ssl</a></code> built-in is just like starting Apache + without it. However, if you have a passphrase on your SSL private + key file, a startup dialog will pop up which asks you to enter the + pass phrase.</p> + + <p>Having to manually enter the passphrase when starting the server + can be problematic - for example, when starting the server from the + system boot scripts. In this case, you can follow the steps + <a href="#removepassphrase">below</a> to remove the passphrase from + your private key. Bear in mind that doing so brings additional security + risks - proceed with caution!</p> + + +<h3><a name="selfcert" id="selfcert">How do I create a self-signed SSL +Certificate for testing purposes?</a></h3> + <ol> + <li>Make sure OpenSSL is installed and in your <code>PATH</code>.<br /> + <br /> + </li> + <li>Run the following command, to create <code>server.key</code> and + <code>server.crt</code> files:<br /> + <code><strong>$ openssl req -new -x509 -nodes -out server.crt + -keyout server.key</strong></code><br /> + These can be used as follows in your <code>httpd.conf</code> + file: + <pre class="prettyprint lang-config">SSLCertificateFile "/path/to/this/server.crt" +SSLCertificateKeyFile "/path/to/this/server.key"</pre> + + </li> + <li>It is important that you are aware that this + <code>server.key</code> does <em>not</em> have any passphrase. + To add a passphrase to the key, you should run the following + command, and enter & verify the passphrase as requested.<br /> + <p><code><strong>$ openssl rsa -des3 -in server.key -out + server.key.new</strong></code><br /> + <code><strong>$ mv server.key.new server.key</strong></code><br /></p> + Please backup the <code>server.key</code> file, and the passphrase + you entered, in a secure location. + </li> + </ol> + + +<h3><a name="realcert" id="realcert">How do I create a real SSL Certificate?</a></h3> +<p>Here is a step-by-step description:</p> + <ol> + <li>Make sure OpenSSL is installed and in your <code>PATH</code>. + <br /> + <br /> + </li> + <li>Create a RSA private key for your Apache server + (will be Triple-DES encrypted and PEM formatted):<br /> + <br /> + <code><strong>$ openssl genrsa -des3 -out server.key 2048</strong></code><br /> + <br /> + Please backup this <code>server.key</code> file and the + pass-phrase you entered in a secure location. + You can see the details of this RSA private key by using the command:<br /> + + <br /> + <code><strong>$ openssl rsa -noout -text -in server.key</strong></code><br /> + <br /> + If necessary, you can also create a decrypted PEM version (not + recommended) of this RSA private key with:<br /> + <br /> + <code><strong>$ openssl rsa -in server.key -out server.key.unsecure</strong></code><br /> + <br /> + + </li> + <li>Create a Certificate Signing Request (CSR) with the server RSA private + key (output will be PEM formatted):<br /> + <br /> + <code><strong>$ openssl req -new -key server.key -out server.csr</strong></code><br /> + <br /> + Make sure you enter the FQDN ("Fully Qualified Domain Name") of the + server when OpenSSL prompts you for the "CommonName", i.e. when you + generate a CSR for a website which will be later accessed via + <code>https://www.foo.dom/</code>, enter "www.foo.dom" here. + You can see the details of this CSR by using<br /> + + <br /> + <code><strong>$ openssl req -noout -text -in server.csr</strong></code><br /> + <br /> + </li> + <li>You now have to send this Certificate Signing Request (CSR) to + a Certifying Authority (CA) to be signed. Once the CSR has been + signed, you will have a real Certificate, which can be used by + Apache. You can have a CSR signed by a commercial CA, or you can + create your own CA to sign it.<br /> + Commercial CAs usually ask you to post the CSR into a web form, + pay for the signing, and then send a signed Certificate, which + you can store in a server.crt file.<br /> + + For details on how to create your own CA, and use this to sign + a CSR, see <a href="#ownca">below</a>.<br /> + + Once your CSR has been signed, you can see the details of the + Certificate as follows:<br /> + <br /> + <code><strong>$ openssl x509 -noout -text -in server.crt</strong></code><br /> + + </li> + <li>You should now have two files: <code>server.key</code> and + <code>server.crt</code>. These can be used as follows in your + <code>httpd.conf</code> file: + <pre class="prettyprint lang-config">SSLCertificateFile "/path/to/this/server.crt" +SSLCertificateKeyFile "/path/to/this/server.key"</pre> + + The <code>server.csr</code> file is no longer needed. + </li> + + </ol> + + +<h3><a name="ownca" id="ownca">How do I create and use my own Certificate Authority (CA)?</a></h3> + <p>The short answer is to use the <code>CA.sh</code> or <code>CA.pl</code> + script provided by OpenSSL. Unless you have a good reason not to, + you should use these for preference. If you cannot, you can create a + self-signed certificate as follows:</p> + + <ol> + <li>Create a RSA private key for your server + (will be Triple-DES encrypted and PEM formatted):<br /> + <br /> + <code><strong>$ openssl genrsa -des3 -out server.key 2048</strong></code><br /> + <br /> + Please backup this <code>server.key</code> file and the + pass-phrase you entered in a secure location. + You can see the details of this RSA private key by using the + command:<br /> + <br /> + <code><strong>$ openssl rsa -noout -text -in server.key</strong></code><br /> + <br /> + If necessary, you can also create a decrypted PEM version (not + recommended) of this RSA private key with:<br /> + <br /> + <code><strong>$ openssl rsa -in server.key -out server.key.unsecure</strong></code><br /> + <br /> + </li> + <li>Create a self-signed certificate (X509 structure) + with the RSA key you just created (output will be PEM formatted):<br /> + <br /> + <code><strong>$ openssl req -new -x509 -nodes -sha1 -days 365 + -key server.key -out server.crt -extensions usr_cert</strong></code><br /> + <br /> + This signs the server CSR and results in a <code>server.crt</code> file.<br /> + You can see the details of this Certificate using:<br /> + <br /> + <code><strong>$ openssl x509 -noout -text -in server.crt</strong></code><br /> + <br /> + </li> + </ol> + + +<h3><a name="passphrase" id="passphrase">How can I change the pass-phrase on my private key file?</a></h3> +<p>You simply have to read it with the old pass-phrase and write it again, + specifying the new pass-phrase. You can accomplish this with the following + commands:</p> + + + <p><code><strong>$ openssl rsa -des3 -in server.key -out server.key.new</strong></code><br /> + <code><strong>$ mv server.key.new server.key</strong></code><br /></p> + + <p>The first time you're asked for a PEM pass-phrase, you should + enter the old pass-phrase. After that, you'll be asked again to + enter a pass-phrase - this time, use the new pass-phrase. If you + are asked to verify the pass-phrase, you'll need to enter the new + pass-phrase a second time.</p> + + +<h3><a name="removepassphrase" id="removepassphrase">How can I get rid of the pass-phrase dialog at Apache startup time?</a></h3> +<p>The reason this dialog pops up at startup and every re-start + is that the RSA private key inside your server.key file is stored in + encrypted format for security reasons. The pass-phrase is needed to decrypt + this file, so it can be read and parsed. Removing the pass-phrase + removes a layer of security from your server - proceed with caution!</p> + <ol> + <li>Remove the encryption from the RSA private key (while + keeping a backup copy of the original file):<br /> + <br /> + <code><strong>$ cp server.key server.key.org</strong></code><br /> + <code><strong>$ openssl rsa -in server.key.org -out server.key</strong></code><br /> + + <br /> + </li> + <li>Make sure the server.key file is only readable by root:<br /> + <br /> + <code><strong>$ chmod 400 server.key</strong></code><br /> + <br /> + </li> + </ol> + + <p>Now <code>server.key</code> contains an unencrypted copy of the key. + If you point your server at this file, it will not prompt you for a + pass-phrase. HOWEVER, if anyone gets this key they will be able to + impersonate you on the net. PLEASE make sure that the permissions on this + file are such that only root or the web server user can read it + (preferably get your web server to start as root but run as another + user, and have the key readable only by root).</p> + + <p>As an alternative approach you can use the ``<code>SSLPassPhraseDialog + exec:/path/to/program</code>'' facility. Bear in mind that this is + neither more nor less secure, of course.</p> + + +<h3><a name="verify" id="verify">How do I verify that a private key matches its Certificate?</a></h3> +<p>A private key contains a series of numbers. Two of these numbers form + the "public key", the others are part of the "private key". The "public + key" bits are included when you generate a CSR, and subsequently form + part of the associated Certificate.</p> + <p>To check that the public key in your Certificate matches the public + portion of your private key, you simply need to compare these numbers. + To view the Certificate and the key run the commands:</p> + + <p><code><strong>$ openssl x509 -noout -text -in server.crt</strong></code><br /> + <code><strong>$ openssl rsa -noout -text -in server.key</strong></code></p> + + <p>The `modulus' and the `public exponent' portions in the key and the + Certificate must match. As the public exponent is usually 65537 + and it's difficult to visually check that the long modulus numbers + are the same, you can use the following approach:</p> + + <p><code><strong>$ openssl x509 -noout -modulus -in server.crt | openssl md5</strong></code><br /> + <code><strong>$ openssl rsa -noout -modulus -in server.key | openssl md5</strong></code></p> + + <p>This leaves you with two rather shorter numbers to compare. It is, + in theory, possible that these numbers may be the same, without the + modulus numbers being the same, but the chances of this are + overwhelmingly remote.</p> + <p>Should you wish to check to which key or certificate a particular + CSR belongs you can perform the same calculation on the CSR as + follows:</p> + + <p><code><strong>$ openssl req -noout -modulus -in server.csr | openssl md5</strong></code></p> + + +<h3><a name="pemder" id="pemder">How can I convert a certificate from PEM to DER format?</a></h3> +<p>The default certificate format for OpenSSL is PEM, which is simply + Base64 encoded DER, with header and footer lines. For some applications + (e.g. Microsoft Internet Explorer) you need the certificate in plain DER + format. You can convert a PEM file <code>cert.pem</code> into the + corresponding DER file <code>cert.der</code> using the following command: + <code><strong>$ openssl x509 -in cert.pem -out cert.der -outform DER</strong></code></p> + + +<h3><a name="gid" id="gid">Why do browsers complain that they cannot verify my server certificate?</a></h3> + + <p>One reason this might happen is because your server certificate is signed + by an intermediate CA. Various CAs, such as Verisign or Thawte, have started + signing certificates not with their root certificate but with intermediate + certificates.</p> + + <p>Intermediate CA certificates lie between the root CA certificate (which is + installed in the browsers) and the server certificate (which you installed + on the server). In order for the browser to be able to traverse and verify + the trust chain from the server certificate to the root certificate it + needs need to be given the intermediate certificates. The CAs should + be able to provide you such intermediate certificate packages that can be + installed on the server.</p> + + <p>You need to include those intermediate certificates with the + <code class="directive"><a href="../mod/mod_ssl.html#sslcertificatechainfile">SSLCertificateChainFile</a></code> + directive.</p> + +</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="section"> +<h2><a name="aboutssl" id="aboutssl">The SSL Protocol</a></h2> +<ul> +<li><a href="#random">Why do I get lots of random SSL protocol +errors under heavy server load?</a></li> +<li><a href="#load">Why does my webserver have a higher load, now +that it serves SSL encrypted traffic?</a></li> +<li><a href="#establishing">Why do HTTPS connections to my server +sometimes take up to 30 seconds to establish a connection?</a></li> +<li><a href="#ciphers">What SSL Ciphers are supported by mod_ssl?</a></li> +<li><a href="#adh">Why do I get ``no shared cipher'' errors, when +trying to use Anonymous Diffie-Hellman (ADH) ciphers?</a></li> +<li><a href="#sharedciphers">Why do I get a 'no shared ciphers' +error when connecting to my newly installed server?</a></li> +<li><a href="#vhosts">Why can't I use SSL with name-based/non-IP-based +virtual hosts?</a></li> +<li><a href="#vhosts2">Is it possible to use Name-Based Virtual +Hosting to identify different SSL virtual hosts?</a></li> +<li><a href="#comp">How do I get SSL compression working?</a></li> +<li><a href="#lockicon">When I use Basic Authentication over HTTPS +the lock icon in Netscape browsers stays unlocked when the dialog pops up. +Does this mean the username/password is being sent unencrypted?</a></li> +<li><a href="#msie">Why do I get I/O errors when connecting via +HTTPS to an Apache+mod_ssl server with Microsoft Internet Explorer +(MSIE)?</a></li> +<li><a href="#srp">How do I enable TLS-SRP?</a></li> +<li><a href="#javadh">Why do I get handshake failures with Java-based clients when using a certificate with more than 1024 bits?</a></li> +</ul> + +<h3><a name="random" id="random">Why do I get lots of random SSL protocol +errors under heavy server load?</a></h3> +<p>There can be a number of reasons for this, but the main one + is problems with the SSL session Cache specified by the + <code class="directive"><a href="../mod/mod_ssl.html#sslsessioncache">SSLSessionCache</a></code> directive. The DBM session + cache is the most likely source of the problem, so using the SHM session cache (or + no cache at all) may help.</p> + + +<h3><a name="load" id="load">Why does my webserver have a higher load, now +that it serves SSL encrypted traffic?</a></h3> +<p>SSL uses strong cryptographic encryption, which necessitates a lot of + number crunching. When you request a webpage via HTTPS, everything (even + the images) is encrypted before it is transferred. So increased HTTPS + traffic leads to load increases.</p> + + +<h3><a name="establishing" id="establishing">Why do HTTPS connections to my server +sometimes take up to 30 seconds to establish a connection?</a></h3> +<p>This is usually caused by a <code>/dev/random</code> device for + <code class="directive"><a href="../mod/mod_ssl.html#sslrandomseed">SSLRandomSeed</a></code> which blocks the + read(2) call until enough entropy is available to service the + request. More information is available in the reference + manual for the <code class="directive"><a href="../mod/mod_ssl.html#sslrandomseed">SSLRandomSeed</a></code> + directive.</p> + + +<h3><a name="ciphers" id="ciphers">What SSL Ciphers are supported by mod_ssl?</a></h3> +<p>Usually, any SSL ciphers supported by the version of OpenSSL in use, + are also supported by <code class="module"><a href="../mod/mod_ssl.html">mod_ssl</a></code>. Which ciphers are + available can depend on the way you built OpenSSL. Typically, at + least the following ciphers are supported:</p> + + <ol> + <li>RC4 with SHA1</li> + <li>AES with SHA1</li> + <li>Triple-DES with SHA1</li> + </ol> + + <p>To determine the actual list of ciphers available, you should run + the following:</p> + <div class="example"><p><code>$ openssl ciphers -v</code></p></div> + + +<h3><a name="adh" id="adh">Why do I get ``no shared cipher'' errors, when +trying to use Anonymous Diffie-Hellman (ADH) ciphers?</a></h3> +<p>By default, OpenSSL does <em>not</em> allow ADH ciphers, for security + reasons. Please be sure you are aware of the potential side-effects + if you choose to enable these ciphers.</p> + <p>In order to use Anonymous Diffie-Hellman (ADH) ciphers, you must + build OpenSSL with ``<code>-DSSL_ALLOW_ADH</code>'', and then add + ``<code>ADH</code>'' into your <code class="directive"><a href="../mod/mod_ssl.html#sslciphersuite">SSLCipherSuite</a></code>.</p> + + +<h3><a name="sharedciphers" id="sharedciphers">Why do I get a 'no shared ciphers' +error when connecting to my newly installed server?</a></h3> +<p>Either you have made a mistake with your + <code class="directive"><a href="../mod/mod_ssl.html#sslciphersuite">SSLCipherSuite</a></code> + directive (compare it with the pre-configured example in + <code>extra/httpd-ssl.conf</code>) or you chose to use DSA/DH + algorithms instead of RSA when you generated your private key + and ignored or overlooked the warnings. If you have chosen + DSA/DH, then your server cannot communicate using RSA-based SSL + ciphers (at least until you configure an additional RSA-based + certificate/key pair). Modern browsers like NS or IE can only + communicate over SSL using RSA ciphers. The result is the + "no shared ciphers" error. To fix this, regenerate your server + certificate/key pair, using the RSA algorithm.</p> + + +<h3><a name="vhosts" id="vhosts">Why can't I use SSL with name-based/non-IP-based virtual hosts?</a></h3> +<p>The reason is very technical, and a somewhat "chicken and egg" problem. + The SSL protocol layer stays below the HTTP protocol layer and + encapsulates HTTP. When an SSL connection (HTTPS) is established + Apache/mod_ssl has to negotiate the SSL protocol parameters with the + client. For this, mod_ssl has to consult the configuration of the virtual + server (for instance it has to look for the cipher suite, the server + certificate, etc.). But in order to go to the correct virtual server + Apache has to know the <code>Host</code> HTTP header field. To do this, the + HTTP request header has to be read. This cannot be done before the SSL + handshake is finished, but the information is needed in order to + complete the SSL handshake phase. See the next question for how to + circumvent this issue.</p> + + <p>Note that if you have a wildcard SSL certificate, or a + certificate that has multiple hostnames on it using subjectAltName + fields, you can use SSL on name-based virtual hosts without further + workarounds.</p> + + +<h3><a name="vhosts2" id="vhosts2">Is it possible to use Name-Based +Virtual Hosting to identify different SSL virtual hosts?</a></h3> + <p>Name-Based Virtual Hosting is a very popular method of identifying + different virtual hosts. It allows you to use the same IP address and + the same port number for many different sites. When people move on to + SSL, it seems natural to assume that the same method can be used to have + lots of different SSL virtual hosts on the same server.</p> + + <p>It is possible, but only if using a 2.2.12 or later web server, + built with 0.9.8j or later OpenSSL. This is because it requires a + feature that only the most recent revisions of the SSL + specification added, called Server Name Indication (SNI).</p> + + <p>Note that if you have a wildcard SSL certificate, or a + certificate that has multiple hostnames on it using subjectAltName + fields, you can use SSL on name-based virtual hosts without further + workarounds.</p> + + <p>The reason is that the SSL protocol is a separate layer which + encapsulates the HTTP protocol. So the SSL session is a separate + transaction, that takes place before the HTTP session has begun. + The server receives an SSL request on IP address X and port Y + (usually 443). Since the SSL request did not contain any Host: + field, the server had no way to decide which SSL virtual host to use. + Usually, it just used the first one it found which matched the + port and IP address specified.</p> + + <p>If you are using a version of the web server and OpenSSL that + support SNI, though, and the client's browser also supports SNI, + then the hostname is included in the original SSL request, and the + web server can select the correct SSL virtual host.</p> + + <p>You can, of course, use Name-Based Virtual Hosting to identify many + non-SSL virtual hosts (all on port 80, for example) and then + have a single SSL virtual host (on port 443). But if you do this, + you must make sure to put the non-SSL port number on the NameVirtualHost + directive, e.g.</p> + + <pre class="prettyprint lang-config">NameVirtualHost 192.168.1.1:80</pre> + + + <p>Other workaround solutions include: </p> + + <p>Using separate IP addresses for different SSL hosts. + Using different port numbers for different SSL hosts.</p> + + +<h3><a name="comp" id="comp">How do I get SSL compression working?</a></h3> +<p>Although SSL compression negotiation was defined in the specification +of SSLv2 and TLS, it took until May 2004 for RFC 3749 to define DEFLATE as +a negotiable standard compression method. +</p> +<p>OpenSSL 0.9.8 started to support this by default when compiled with the +<code>zlib</code> option. If both the client and the server support compression, +it will be used. However, most clients still try to initially connect with an +SSLv2 Hello. As SSLv2 did not include an array of preferred compression algorithms +in its handshake, compression cannot be negotiated with these clients. +If the client disables support for SSLv2, either an SSLv3 or TLS Hello +may be sent, depending on which SSL library is used, and compression may +be set up. You can verify whether clients make use of SSL compression by +logging the <code>%{SSL_COMPRESS_METHOD}x</code> variable. +</p> + + +<h3><a name="lockicon" id="lockicon">When I use Basic Authentication over HTTPS +the lock icon in Netscape browsers stays unlocked when the dialog pops up. +Does this mean the username/password is being sent unencrypted?</a></h3> +<p>No, the username/password is transmitted encrypted. The icon in + Netscape browsers is not actually synchronized with the SSL/TLS layer. + It only toggles to the locked state when the first part of the actual + webpage data is transferred, which may confuse people. The Basic + Authentication facility is part of the HTTP layer, which is above + the SSL/TLS layer in HTTPS. Before any HTTP data communication takes + place in HTTPS, the SSL/TLS layer has already completed its handshake + phase, and switched to encrypted communication. So don't be + confused by this icon.</p> + + +<h3><a name="msie" id="msie">Why do I get I/O errors when connecting via +HTTPS to an Apache+mod_ssl server with older versions of Microsoft Internet +Explorer (MSIE)?</a></h3> +<p>The first reason is that the SSL implementation in some MSIE versions has + some subtle bugs related to the HTTP keep-alive facility and the SSL close + notify alerts on socket connection close. Additionally the interaction + between SSL and HTTP/1.1 features are problematic in some MSIE versions. + You can work around these problems by forcing Apache not to use HTTP/1.1, + keep-alive connections or send the SSL close notify messages to MSIE clients. + This can be done by using the following directive in your SSL-aware + virtual host section:</p> + <pre class="prettyprint lang-config">SetEnvIf User-Agent "MSIE [2-5]" \ + nokeepalive ssl-unclean-shutdown \ + downgrade-1.0 force-response-1.0</pre> + + <p>Further, some MSIE versions have problems with particular ciphers. + Unfortunately, it is not possible to implement a MSIE-specific + workaround for this, because the ciphers are needed as early as the + SSL handshake phase. So a MSIE-specific + <code class="directive"><a href="../mod/mod_setenvif.html#setenvif">SetEnvIf</a></code> won't solve these + problems. Instead, you will have to make more drastic + adjustments to the global parameters. Before you decide to do + this, make sure your clients really have problems. If not, do not + make these changes - they will affect <em>all</em> your clients, MSIE + or otherwise.</p> + + +<h3><a name="srp" id="srp">How do I enable TLS-SRP?</a></h3> + <p>TLS-SRP (Secure Remote Password key exchange for TLS, specified in RFC 5054) + can supplement or replace certificates in authenticating an SSL connection. + To use TLS-SRP, set the + <code class="directive"><a href="../mod/mod_ssl.html#sslsrpverifierfile">SSLSRPVerifierFile</a></code> directive to + point to an OpenSSL SRP verifier file. To create the verifier file, use the + <code>openssl</code> tool:</p> + <div class="example"><p><code> + openssl srp -srpvfile passwd.srpv -add username + </code></p></div> + <p>After creating this file, specify it in the SSL server configuration:</p> + <div class="example"><p><code> + SSLSRPVerifierFile /path/to/passwd.srpv + </code></p></div> + <p>To force clients to use non-certificate TLS-SRP cipher suites, use the + following directive:</p> + <div class="example"><p><code> + SSLCipherSuite "!DSS:!aRSA:SRP" + </code></p></div> + + +<h3><a name="javadh" id="javadh">Why do I get handshake failures with Java-based clients when using a certificate with more than 1024 bits?</a></h3> + <p>Beginning with version 2.4.7, + <code class="module"><a href="../mod/mod_ssl.html">mod_ssl</a></code> will use DH parameters which include primes + with lengths of more than 1024 bits. Java 7 and earlier limit their + support for DH prime sizes to a maximum of 1024 bits, however.</p> + + <p>If your Java-based client aborts with exceptions such as + <code>java.lang.RuntimeException: Could not generate DH keypair</code> and + <code>java.security.InvalidAlgorithmParameterException: Prime size must be + multiple of 64, and can only range from 512 to 1024 (inclusive)</code>, + and httpd logs <code>tlsv1 alert internal error (SSL alert number 80)</code> + (at <code class="directive"><a href="../mod/core.html#loglevel">LogLevel</a></code> <code>info</code> + or higher), you can either rearrange mod_ssl's cipher list with + <code class="directive"><a href="../mod/mod_ssl.html#sslciphersuite">SSLCipherSuite</a></code> + (possibly in conjunction with <code class="directive"><a href="../mod/mod_ssl.html#sslhonorcipherorder">SSLHonorCipherOrder</a></code>), + or you can use custom DH parameters with a 1024-bit prime, which + will always have precedence over any of the built-in DH parameters.</p> + + <p>To generate custom DH parameters, use the <code>openssl dhparam 1024</code> + command. Alternatively, you can use the following standard 1024-bit DH + parameters from <a href="http://www.ietf.org/rfc/rfc2409.txt">RFC 2409</a>, + section 6.2:</p> + <div class="example"><pre>-----BEGIN DH PARAMETERS----- +MIGHAoGBAP//////////yQ/aoiFowjTExmKLgNwc0SkCTgiKZ8x0Agu+pjsTmyJR +Sgh5jjQE3e+VGbPNOkMbMCsKbfJfFDdP4TVtbVHCReSFtXZiXn7G9ExC6aY37WsL +/1y29Aa37e44a/taiZ+lrp8kEXxLH+ZJKGZR7OZTgf//////////AgEC +-----END DH PARAMETERS-----</pre></div> + <p>Add the custom parameters including the "BEGIN DH PARAMETERS" and + "END DH PARAMETERS" lines to the end of the first certificate file + you have configured using the + <code class="directive"><a href="../mod/mod_ssl.html#sslcertificatefile">SSLCertificateFile</a></code> directive.</p> + + +</div><div class="top"><a href="#page-header"><img alt="top" src="../images/up.gif" /></a></div> +<div class="section"> +<h2><a name="support" id="support">mod_ssl Support</a></h2> +<ul> +<li><a href="#resources">What information resources are available in +case of mod_ssl problems?</a></li> +<li><a href="#contact">What support contacts are available in case of +mod_ssl problems?</a></li> +<li><a href="#reportdetails">What information should I +provide when writing a bug report?</a></li> +<li><a href="#coredumphelp">I had a core dump, can you help me?</a></li> +<li><a href="#backtrace">How do I get a backtrace, to help find the reason +for my core dump?</a></li> +</ul> + +<h3><a name="resources" id="resources">What information resources are available in case of mod_ssl problems?</a></h3> +<p>The following information resources are available. + In case of problems you should search here first.</p> + + <dl> + <dt>Answers in the User Manual's F.A.Q. List (this)</dt> + <dd><a href="http://httpd.apache.org/docs/2.4/ssl/ssl_faq.html"> + http://httpd.apache.org/docs/2.4/ssl/ssl_faq.html</a><br /> + First check the F.A.Q. (this text). If your problem is a common + one, it may have been answered several times before, and been included + in this doc. + </dd> + </dl> + + +<h3><a name="contact" id="contact">What support contacts are available in case +of mod_ssl problems?</a></h3> + <p>The following lists all support possibilities for mod_ssl, in order of + preference. Please go through these possibilities + <em>in this order</em> - don't just pick the one you like the look of. </p> + <ol> + + <li><em>Send a Problem Report to the Apache httpd Users Support Mailing List</em><br /> + <a href="mailto:users@httpd.apache.org"> + users@httpd.apache.org</a><br /> + This is the second way of submitting your problem report. Again, you must + subscribe to the list first, but you can then easily discuss your problem + with the whole Apache httpd user community. + </li> + + <li><em>Write a Problem Report in the Bug Database</em><br /> + <a href="http://httpd.apache.org/bug_report.html"> + http://httpd.apache.org/bug_report.html</a><br /> + This is the last way of submitting your problem report. You should only + do this if you've already posted to the mailing lists, and had no success. + Please follow the instructions on the above page <em>carefully</em>. + </li> + </ol> + + +<h3><a name="reportdetails" id="reportdetails">What information should I +provide when writing a bug report?</a></h3> +<p>You should always provide at least the following information:</p> + + <dl> + <dt>Apache httpd and OpenSSL version information</dt> + <dd>The Apache version can be determined + by running <code>httpd -v</code>. The OpenSSL version can be + determined by running <code>openssl version</code>. Alternatively, if + you have Lynx installed, you can run the command <code>lynx -mime_header + http://localhost/ | grep Server</code> to gather this information in a + single step. + </dd> + + <dt>The details on how you built and installed Apache httpd and OpenSSL</dt> + <dd>For this you can provide a logfile of your terminal session which shows + the configuration and install steps. If this is not possible, you + should at least provide the <code class="program"><a href="../programs/configure.html">configure</a></code> command line you used. + </dd> + + <dt>In case of core dumps please include a Backtrace</dt> + <dd>If your Apache httpd dumps its core, please attach + a stack-frame ``backtrace'' (see <a href="#backtrace">below</a> + for information on how to get this). This information is required + in order to find a reason for your core dump. + </dd> + + <dt>A detailed description of your problem</dt> + <dd>Don't laugh, we really mean it! Many problem reports don't + include a description of what the actual problem is. Without this, + it's very difficult for anyone to help you. So, it's in your own + interest (you want the problem be solved, don't you?) to include as + much detail as possible, please. Of course, you should still include + all the essentials above too. + </dd> + </dl> + + +<h3><a name="coredumphelp" id="coredumphelp">I had a core dump, can you help me?</a></h3> +<p>In general no, at least not unless you provide more details about the code + location where Apache dumped core. What is usually always required in + order to help you is a backtrace (see next question). Without this + information it is mostly impossible to find the problem and help you in + fixing it.</p> + + +<h3><a name="backtrace" id="backtrace">How do I get a backtrace, to help find +the reason for my core dump?</a></h3> +<p>Following are the steps you will need to complete, to get a backtrace:</p> + <ol> + <li>Make sure you have debugging symbols available, at least + in Apache. On platforms where you use GCC/GDB, you will have to build + Apache+mod_ssl with ``<code>OPTIM="-g -ggdb3"</code>'' to get this. On + other platforms at least ``<code>OPTIM="-g"</code>'' is needed. + </li> + + <li>Start the server and try to reproduce the core-dump. For this you may + want to use a directive like ``<code>CoreDumpDirectory /tmp</code>'' to + make sure that the core-dump file can be written. This should result + in a <code>/tmp/core</code> or <code>/tmp/httpd.core</code> file. If you + don't get one of these, try running your server under a non-root UID. + Many modern kernels do not allow a process to dump core after it has + done a <code>setuid()</code> (unless it does an <code>exec()</code>) for + security reasons (there can be privileged information left over in + memory). If necessary, you can run <code>/path/to/httpd -X</code> + manually to force Apache to not fork. + </li> + + <li>Analyze the core-dump. For this, run <code>gdb /path/to/httpd + /tmp/httpd.core</code> or a similar command. In GDB, all you + have to do then is to enter <code>bt</code>, and voila, you get the + backtrace. For other debuggers consult your local debugger manual. + </li> + </ol> + +</div></div> +<div class="bottomlang"> +<p><span>Available Languages: </span><a href="../en/ssl/ssl_faq.html" title="English"> en </a> | +<a href="../fr/ssl/ssl_faq.html" hreflang="fr" rel="alternate" title="Français"> fr </a></p> +</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. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed by our moderators if they are either implemented or considered invalid/off-topic. 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