Creating an SSL cert
From: http://slacksite.com/apache/certificate.html
Generating an SSL Certificate with Apache+mod_sslGenerating an SSL Certificate with Apache+mod_ssl
Introduction
This document is intended to be a quick guide to generating and installing an SSL certificate on an Apache web server with the mod_ssl module. While this is not an overly difficult process, it does involve running several long commands with numerous options. This document should be all that you need to walk you through the process of generating the certificate and installing it in your web server.
This document does not attempt to discuss compiling or installing Apache and mod_ssl. For detailed instructions on that topic, please see "Building Apache with mod_ssl and Other Modules". This document also does not attempt to discuss detailed configuration of SSL hosts in Apache. Details will be provided on setting up a basic SSL virtual host that should work in nearly all standard circumstances. Ralf Engelschall, the author of mod_ssl, maintains excellent documentation at http://www.modssl.org/docs. For information on more advanced configurations or special situations, please refer to the full documentation. In addition, the openssl toolkit provides fairly extensive man pages, which are also available in HTML format at http://www.openssl.org/docs/
Brief SSL Primer
This section will serve as a very brief introduction to SSL, the Secure Socket Layer. Cryptography is a very extensive topic which literally fills volumes of texts. The following is an extremely simplified view of how SSL is implemented and what part the certificate plays in the entire process. There may be some small inaccuracies in an effort to present the information in the easiest possible format.
Normal web traffic is sent unencrypted over the Internet. That is, anyone with access to the right tools can snoop all of that traffic. Obviously, this can lead to problems, especially where security and privacy is necessary, such as in credit card data and bank transactions. The Secure Socket Layer is used to encrypt the data stream between the web server and the web client (the browser).
SSL makes use of what is known as asymmetric cryptography, commonly referred to as public key cryptography (PKI). With public key cryptography, two keys are created, one public, one private. Anything encrypted with either key can only be decrypted with its corresponding key. Thus if a message or data stream were encrypted with the server's private key, it can be decrypted only using its corresponding public key, ensuring that the data only could have come from the server.
If SSL utilizes public key cryptography to encrypt the data stream traveling over the Internet, why is a certificate necessary? The technical answer to that question is that a certificate is not really necessary--the data is secure and cannot easily be decrypted by a third party. However, certificates do serve a crucial role in the communication process. The certificate, signed by a trusted Certificate Authority (CA), ensures that the certificate holder is really who he claims to be. Without a trusted signed certificate, your data may be encrypted, however, the party you are communicating with may not be whom you think. Without certificates, impersonation attacks would be much more common.
Generating a Private Key and CSR
The openssl toolkit is used to generate an RSA Private Key and CSR (Certificate
Signing Request). It can also be used to generate self-signed certificates which
can be used for testing purposes or internal usage. The utility used to do all of
these tasks is known simply as openssl
. It should be installed in the
/usr/local/ssl/bin
directory. You may want to add this directory
to your PATH
, or copy or link the openssl utility to a directory that
is already in your PATH
so that you do not have to type the full path
to the executable. The examples below will assume that openssl
is in
a location that is accessible to you without using the full path to the command.
The first step is to create your RSA Private Key. This key is a 1024 bit RSA key
which is encrypted using Triple-DES and stored in a PEM format so that it is
readable as ASCII text. We will use several files as random seed enhancers
which will help to make the key more secure. Text files that have been compressed
with a utility such as gzip
are good choices. The key is generated
using the following command, where file1:file2:etc
represents the
random compressed files.
$ openssl genrsa -des3 -rand file1:file2:file3:file4:file5 -out server.key 1024
The command will prompt you for a pass-phrase and then store the key in the file
server.key
. It is critical that the pass-phrase
be secure and not forgotten. If either the key is lost, or the pass-phrase
is forgotten, the certificate will be useless! It cannot be
stressed enough how important the private key is to the certificate. If the
private key and pass-phrase are compromised, the certificate will have to be
revoked, costing you the price of the certificate all over again if you have paid
an authority for the certificate. It may be a wise idea to back this file up to
secure media, such as tape or diskette.
One unfortunate side-effect of the pass-phrased private key is that Apache will ask for the pass-phrase each time the web server is started. Obviously this is not necessarily convenient as someone will not always be around to type in the pass-phrase, such as after a reboot or crash. mod_ssl includes the ability to use an external program in place of the built-in pass-phrase dialog, however, this is not necessarily the most secure option either. It is possible to remove the Triple-DES encryption from the key, thereby no longer needing to type in a pass-phrase. If the private key is no longer encrypted, it is critical that this file only be readable by the root user! If your system is ever compromised and a third party obtains your unencrypted private key, the corresponding certificate will need to be revoked. With that being said, use the following command to remove the pass-phrase from the key:
$ openssl rsa -in server.key -out server.pem
Once the private key is generated a Certificate Signing Request can be generated. The CSR is then used in one of two ways. Ideally, the CSR will be sent to a Certificate Authority, such as Thawte or Verisign who will verify the identity of the requestor and issue a signed certificate. The second option is to self-sign the CSR, which will be demonstrated in the next section.
During the generation of the CSR, you will be prompted for several pieces of
information. These are the X.509 attributes of the certificate. One of the
prompts will be for "Common Name (e.g., YOUR name)
". It is important that
this field be filled in with the fully qualified domain name of the server to be
protected by SSL. If the website to be protected will be
https://www.server.com
, then enter www.server.com
at this
prompt. The command to generate the CSR is as follows:
$ openssl req -new -key server.key -out server.csr
A sample CSR generation session is shown below, with sample responses shown in bold:
$ openssl req -new -key server.key -out server.csr Using configuration from /usr/local/ssl/openssl.cnf Enter PEM pass phrase:Enter pass phrase here You are about to be asked to enter information that will be incorporated into your certificate request. What you are about to enter is what is called a Distinguished Name or a DN. There are quite a few fields but you can leave some blank For some fields there will be a default value, If you enter '.', the field will be left blank. ----- Country Name (2 letter code) [AU]:US State or Province Name (full name) [Some-State]:New Hampshire Locality Name (eg, city) []:Nashua Organization Name (eg, company) [Internet Widgits Pty Ltd]:Domain.com, Inc. Organizational Unit Name (eg, section) []:. Common Name (eg, YOUR name) []:www.domain.com Email Address []:webmaster@domain.com Please enter the following 'extra' attributes to be sent with your certificate request A challenge password []: An optional company name []:
Generating a Self-Signed Certificate
At this point you will need to generate a self-signed certificate because you either don't plan on having your certificate signed by a CA, or you wish to test your new SSL implementation while the CA is signing your certificate. In my experience dealing with Thawte, it can take up to a week or more before receiving your signed certificate. The time it takes to receive the certificate will vary based on how quickly they receive your required documentation. This temporary certificate will generate an error in the client browser to the effect that the signing certificate authority is unknown and not trusted.
To generate a temporary certificate which is good for 60 days, issue the following command:
$ openssl x509 -req -days 60 -in server.csr -signkey server.key -out server.crt
Installing the Private Key and Certificate
When Apache with mod_ssl is installed, it creates several directories in the Apache
config directory. The location of this directory will differ depending on how Apache
was compiled. If using my instructions on compiling Apache, the config directory is
/usr/local/apache/etc
. The directories mod_ssl creates include
ssl.crt
, ssl.csr
, and ssl.key
. These are
good locations to store server certificates, CSRs, and private keys, respectively. If
there will be multiple SSL enabled hosts on one server, it may be good practice to name
the files with the fully qualified domain name of the SSL enabled host.
When adding SSL enabled virtualhosts to the web server, I prefer to keep all of the SSL
virtualhosts in a separate file. This insures that all SSL hosts can be easily found in
one location and helps to keep the httpd.conf
file from growing too
large. The SSL virtualhosts will be kept in a file called ssl.conf
. In order
for Apache to recognize and parse this file, it must be included in the
httpd.conf
file with the following directive:
Include /usr/local/apache/etc/ssl.conf
Configuring SSL Enabled Virtual Hosts
Extensive examples of SSL configurations for a virtualhost are included as part of the
/usr/local/apache/etc/httpd.conf.default
file installed with mod_ssl. Please
refer to this file and to the mod_ssl documentation for more detailed information on
configuration options. A basic SSL enabled virtualhost will appear as follows in the
ssl.conf file:
# SSL Virtual Hosts <IfDefine SSL> <VirtualHost _default_:443> ServerAdmin webmaster@domain.com DocumentRoot /usr/local/apache/share/htdocs ServerName www.domain.com ScriptAlias /cgi-bin/ /usr/local/apache/share/htdocs/cgi-bin/ SSLEngine on SSLCertificateFile /usr/local/apache/etc/ssl.crt/server.crt SSLCertificateKeyFile /usr/local/apache/etc/ssl.key/server.pem SetEnvIf User-Agent ".*MSIE.*" nokeepalive ssl-unclean-shutdown CustomLog /usr/local/apache/var/log/ssl_request_log \ "%t %h %{SSL_PROTOCOL}x %{SSL_CIPHER}x \"%r\" %b" </VirtualHost> </IfDefine>
This will create an SSL virtualhost named www.domain.com, which is accessed via port 443
(the standard port for https) on the default IP address of the web server. It is possible
to add as many additional virtualhosts as there are IP addresses that the web server
listens to. Simply add additional virtualhost blocks inside of the
<IfDefine SSL>
and </IfDefine>
tags.
Due to the nature of the SSL encryption of the HTTP traffic, it is NOT
possible to have name-based (HTTP1.1) SSL virtual hosts. To create a new SSL
virtualhost on a different IP address, simply replace _default_
with the
IP address of the virtualhost.
After adding the virtualhost to the ssl.conf
file, Apache must be killed and
restarted in order for it to recognize the new virtualhost. Unfortunately, this is one of
the rare instances where a simple HUP
signal will not work. After restarting
the server, depending on whether the encrypted or unencrypted key was used, Apache will
prompt you for the pass-phrase(s) of the SSL virtualhost(s). Enter the pass-phrase(s) and
the web server will start.
Now, point your favorite browser to the new virtualhost you just created, remembering to use https:// instead of http://, and you should be greeted with a warning dialog if you are using the self-signed certificate. Acknowledge the dialog and the page will continue to load, protected by SSL. The status bar of your browser should be graced by the 'lock' icon, which signifies the page is protected via SSL. This is all there is to it!