HTTPD - Apache2 Web Server
Apache is the most commonly used Web Server on Linux systems. Web Servers are used to serve Web Pages requested by client computers. Clients typically request and view Web Pages using Web Browser applications such as Firefox, Opera, or Mozilla.
Users enter a Uniform Resource Locator (URL) to point to a Web server by means of its Fully Qualified Domain Name (FQDN) and a path to the required resource. For example, to view the home page of the Ubuntu Web site a user will enter only the FQDN. To request specific information about paid support, a user will enter the FQDN followed by a path.
The most common protocol used to transfer Web pages is the Hyper Text Transfer Protocol (HTTP). Protocols such as Hyper Text Transfer Protocol over Secure Sockets Layer (HTTPS), and File Transfer Protocol (FTP), a protocol for uploading and downloading files, are also supported.
Apache Web Servers are often used in combination with the MySQL database engine, the HyperText Preprocessor (PHP) scripting language, and other popular scripting languages such as Python and Perl. This configuration is termed LAMP (Linux, Apache, MySQL and Perl/Python/PHP) and forms a powerful and robust platform for the development and deployment of Web-based applications.
- At a terminal prompt enter the following command:
sudo apt-get install apache2
apache2.conf. In addition, other configuration files may be added using the Include directive, and wildcards can be used to include many configuration files. Any directive may be placed in any of these configuration files. Changes to the main configuration files are only recognized by Apache2 when it is started or restarted.
The server also reads a file containing mime document types; the filename is set by the TypesConfig directive, and is
The default Apache2 configuration file is
/etc/apache2/apache2.conf. You can edit this file to configure the Apache2 server. You can configure the port number, document root, modules, log files, virtual hosts, etc.
- Apache2 ships with a virtual-host-friendly default configuration. That is, it is configured with a single default virtual host (using the VirtualHost directive) which can modified or used as-is if you have a single site, or used as a template for additional virtual hosts if you have multiple sites. If left alone, the default virtual host will serve as your default site, or the site users will see if the URL they enter does not match the ServerName directive of any of your custom sites. To modify the default virtual host, edit the file
/etc/apache2/sites-available/default. If you wish to configure a new virtual host or site, copy that file into the same directory with a name you choose. For example, sudo cp /etc/apache2/sites-available/default /etc/apache2/sites-available/mynewsite Edit the new file to configure the new site using some of the directives described below.
- The ServerAdmin directive specifies the email address to be advertised for the server's administrator. The default value is webmaster@localhost. This should be changed to an email address that is delivered to you (if you are the server's administrator). If your website has a problem, Apache2 will display an error message containing this email address to report the problem to. Find this directive in your site's configuration file in /etc/apache2/sites-available.
- The Listen directive specifies the port, and optionally the IP address, Apache2 should listen on. If the IP address is not specified, Apache2 will listen on all IP addresses assigned to the machine it runs on. The default value for the Listen directive is 80. Change this to 127.0.0.1:80 to cause Apache2 to listen only on your loopback interface so that it will not be available to the Internet, to (for example) 81 to change the port that it listens on, or leave it as is for normal operation. This directive can be found and changed in its own file,
- The ServerName directive is optional and specifies what FQDN your site should answer to. The default virtual host has no ServerName directive specified, so it will respond to all requests that do not match a ServerName directive in another virtual host. If you have just acquired the domain name ubunturocks.com and wish to host it on your Ubuntu server, the value of the ServerName directive in your virtual host configuration file should be ubunturocks.com. Add this directive to the new virtual host file you created earlier (
You may also want your site to respond to www.ubunturocks.com, since many users will assume the www prefix is appropriate. Use the ServerAlias directive for this. You may also use wildcards in the ServerAlias directive. For example, ServerAlias *.ubunturocks.com will cause your site to respond to any domain request ending in .ubunturocks.com.
- The DocumentRoot directive specifies where Apache should look for the files that make up the site. The default value is /var/www. No site is configured there, but if you uncomment the RedirectMatch directive in
/etc/apache2/apache2.confrequests will be redirected to /var/www/apache2-default where the default Apache2 site awaits. Change this value in your site's virtual host file, and remember to create that directory if necessary!
|The /etc/apache2/sites-available directory is not parsed by Apache2. Symbolic links in /etc/apache2/sites-enabled point to "available" sites. Use the a2ensite (Apache2 Enable Site) utility to create those symbolic links, like so: sudo a2ensite mynewsite where your site's configuration file is |
- The DirectoryIndex is the default page served by the server when a user requests an index of a directory by specifying a forward slash (/) at the end of the directory name.
For example, when a user requests the page http://www.example.com/this_directory/, he or she will get either the DirectoryIndex page if it exists, a server-generated directory list if it does not and the Indexes option is specified, or a Permission Denied page if neither is true. The server will try to find one of the files listed in the DirectoryIndex directive and will return the first one it finds. If it does not find any of these files and if Options Indexes is set for that directory, the server will generate and return a list, in HTML format, of the subdirectories and files in the directory. The default value, found in
/etc/apache2/apache2.confis " index.html index.cgi index.pl index.php index.xhtml". Thus, if Apache2 finds a file in a requested directory matching any of these names, the first will be displayed.
- The ErrorDocument directive allows you to specify a file for Apache to use for specific error events. For example, if a user requests a resource that does not exist, a 404 error will occur, and per Apache2's default configuration, the file
/usr/share/apache2/error/HTTP_NOT_FOUND.html.varwill be displayed. That file is not in the server's DocumentRoot, but there is an Alias directive in
/etc/apache2/apache2.confthat redirects requests to the /error directory to /usr/share/apache2/error/. To see a list of the default ErrorDocument directives, use this command: grep ErrorDocument /etc/apache2/apache2.conf
- By default, the server writes the transfer log to the file /var/log/apache2/access.log. You can change this on a per-site basis in your virtual host configuration files with the CustomLog directive, or omit it to accept the default, specified in
/etc/apache2/apache2.conf. You may also specify the file to which errors are logged, via the ErrorLog directive, whose default is
/var/log/apache2/error.log. These are kept separate from the transfer logs to aid in troubleshooting problems with your Apache2 server. You may also specify the LogLevel (the default value is "warn") and the LogFormat (see
/etc/apache2/apache2.conffor the default value).
- Some options are specified on a per-directory basis rather than per-server. Option is one of these directives. A Directory stanza is enclosed in XML-like tags, like so:
The Options directive within a Directory stanza accepts one or more of the following values (among others), separated by spaces:
- ExecCGI - Allow execution of CGI scripts. CGI scripts are not executed if this option is not chosen.
Most files should not be executed as CGI scripts. This would be very dangerous. CGI scripts should kept in a directory separate from and outside your DocumentRoot, and only this directory should have the ExecCGI option set. This is the default, and the default location for CGI scripts is /usr/lib/cgi-bin.
- Includes - Allow server-side includes. Server-side includes allow an HTML file to include other files. This is not a common option. See the Apache2 SSI Howto for mor information.
- IncludesNOEXEC - Allow server-side includes, but disable the #exec and #include commands in CGI scripts.
- Indexes - Display a formatted list of the directory's contents, if no DirectoryIndex (such as index.html) exists in the requested directory.
For security reasons, this should usually not be set, and certainly should not be set on your DocumentRoot directory. Enable this option carefully on a per-directory basis only if you are certain you want users to see the entire contents of the directory.
- Multiview - Support content-negotiated multiviews; this option is disabled by default for security reasons. See the Apache2 documentation on this option.
- SymLinksIfOwnerMatch - Only follow symbolic links if the target file or directory has the same owner as the link.
- ExecCGI - Allow execution of CGI scripts. CGI scripts are not executed if this option is not chosen.
Virtual Hosts Settings
The directives set for a virtual host only apply to that particular virtual host. If a directive is set server-wide and not defined within the virtual host settings, the default setting is used. For example, you can define a Webmaster email address and not define individual email addresses for each virtual host.
Set the DocumentRoot directive to the directory that contains the root document (such as index.html) for the virtual host. The default DocumentRoot is
The ServerAdmin directive within the VirtualHost stanza is the email address used in the footer of error pages if you choose to show a footer with an email address on the error pages.
LockFile - The LockFile directive sets the path to the lockfile used when the server is compiled with either USE_FCNTL_SERIALIZED_ACCEPT or USE_FLOCK_SERIALIZED_ACCEPT. It must be stored on the local disk. It should be left to the default value unless the logs directory is located on an NFS share. If this is the case, the default value should be changed to a location on the local disk and to a directory that is readable only by root.
PidFile - The PidFile directive sets the file in which the server records its process ID (pid). This file should only be readable by root. In most cases, it should be left to the default value.
User - The User directive sets the userid used by the server to answer requests. This setting determines the server's access. Any files inaccessible to this user will also be inaccessible to your website's visitors. The default value for User is www-data.
|Unless you know exactly what you are doing, do not set the User directive to root. Using root as the User will create large security holes for your Web server.|
sudo apt-get install libapache2-mod-auth-mysql
Once you install the module, the module will be available in the
/etc/apache2/mods-availabledirectory. You can use the a2enmod command to enable a module. You can use the a2dismod command to disable a module. Once you enable the module, the module will be available in the the
The mod_ssl module is available in apache2-common package. If you have installed this package, you can run the following command from a terminal prompt to enable the mod_ssl module:
sudo a2enmod ssl
Certificates and Security
Alternatively, you can create your own self-signed certificate. Note, however, that self-signed certificates should not be used in most production environments. Self-signed certificates are not automatically accepted by a user's browser. Users are prompted by the browser to accept the certificate and create the secure connection.
Once you have a self-signed certificate or a signed certificate from the CA of your choice, you need to install it on your secure server.
Types of Certificates
- Browsers (usually) automatically recognize the certificate and allow a secure connection to be made without prompting the user.
- When a CA issues a signed certificate, it is guaranteeing the identity of the organization that is providing the web pages to the browser.
You can generate a self-signed certificate for your secure server, but be aware that a self-signed certificate does not provide the same functionality as a CA-signed certificate. A self-signed certificate is not automatically recognized by most Web browsers, and a self-signed certificate does not provide any guarantee concerning the identity of the organization that is providing the website. A CA-signed certificate provides both of these important capabilities for a secure server. The process of getting a certificate from a CA is fairly easy. A quick overview is as follows:
- Create a private and public encryption key pair.
- Create a certificate request based on the public key. The certificate request contains information about your server and the company hosting it.
- Send the certificate request, along with documents proving your identity, to a CA. We cannot tell you which certificate authority to choose. Your decision may be based on your past experiences, or on the experiences of your friends or colleagues, or purely on monetary factors.
Once you have decided upon a CA, you need to follow the instructions they provide on how to obtain a certificate from them.
- When the CA is satisfied that you are indeed who you claim to be, they send you a digital certificate.
- Install this certificate on your secure server, and begin handling secure transactions.
Generating a Certificate Signing Request (CSR)
openssl genrsa -des3 -out server.key 1024
Generating RSA private key, 1024 bit long modulus .....................++++++ .................++++++ unable to write 'random state' e is 65537 (0x10001) Enter pass phrase for server.key:You can now enter your passphrase. For best security, it should at least contain eight characters. The minimum length when specifying -des3 is four characters. It should include numbers and/or punctuation and not be a word in a dictionary. Also remember that your passphrase is case-sensitive.
Re-type the passphrase to verify. Once you have re-typed it correctly, the server key is generated and stored in
|You can also run your secure web server without a passphrase. This is convenient because you will not need to enter the passphrase every time you start your secure web server. But it is highly insecure and a compromise of the key means a compromise of the server as well.|
openssl rsa -in server.key -out server.key.insecure
Once you run the above command, the insecure key will be stored in the
server.key.insecurefile. You can use this file to generate the CSR without passphrase.
To create the CSR, run the following command at a terminal prompt:
openssl req -new -key server.key -out server.csr
It will prompt you enter the passphrase. If you enter the correct passphrase, it will prompt you to enter Company Name, Site Name, Email Id, etc. Once you enter all these details, your CSR will be created and it will be stored in the
server.csrfile. You can submit this CSR file to a CA for processing. The CAN will use this CSR file and issue the certificate. On the other hand, you can create self-signed certificate using this CSR.
Creating a Self-Signed Certificate
openssl x509 -req -days 365 -in server.csr -signkey server.key -out server.crt
The above command will prompt you to enter the passphrase. Once you enter the correct passphrase, your certificate will be created and it will be stored in the
|If your secure server is to be used in a production environment, you probably need a CA-signed certificate. It is not recommended to use self-signed certificate.|
Installing the Certificate
server.keyand certificate file
server.crtor the certificate file issued by your CA by running following commands at a terminal prompt:
sudo cp server.crt /etc/ssl/certs sudo cp server.key /etc/ssl/private
You should add the following four lines to the
/etc/apache2/sites-available/defaultfile or the configuration file for your secure virtual host. You should place them in the VirtualHost section. They should be placed under the DocumentRoot line:
SSLEngine on SSLOptions +FakeBasicAuth +ExportCertData +CompatEnvVars +StrictRequire SSLCertificateFile /etc/ssl/certs/server.crt SSLCertificateKeyFile /etc/ssl/private/server.keyHTTPS should listen on port number 443. You should add the following line to the
Accessing the Server
sudo /etc/init.d/apache2 restart
|You should remember and enter the passphrase every time you start your secure web server.|