33 The Apache HTTP Server #

Make sure the following requirements are met before trying to set up the Apache Web server:

Apache on SUSE Linux Enterprise Server is not installed by default. To install it with a standard, predefined configuration that runs “out of the box”, proceed as follows:

You can start Apache automatically at boot time or start it manually.

To make sure that Apache is automatically started during boot in the targets multi-user.target and graphical.target, execute the following command:

root # systemctl enable apache2

For more information about the systemd targets in SUSE Linux Enterprise Server and a description of the YaST Services Manager, refer to Section 14.4, “Managing services with YaST”.

To manually start Apache using the shell, run systemctl start apache2.

Now that the Web server is running, you can add your own documents, adjust the configuration according to your needs, or add functionality by installing modules.

This section gives an overview of the Apache configuration files. If you use YaST for configuration, you do not need to touch these files—however, the information might be useful for you if you want to switch to manual configuration later on.

Apache configuration files can be found in two different locations:

/etc/apache2/
     |
     |- charset.conv
     |- conf.d/
     |   |
     |   |- *.conf
     |
     |- default-server.conf
     |- errors.conf
     |- httpd.conf
     |- listen.conf
     |- magic
     |- mime.types
     |- mod_*.conf
     |- server-tuning.conf
     |- ssl.*
     |- ssl-global.conf
     |- sysconfig.d
     |   |
     |   |- global.conf
     |   |- include.conf
     |   |- loadmodule.conf . .
     |
     |- uid.conf
     |- vhosts.d
     |   |- *.conf

Configuring Apache manually involves editing plain text configuration files as user root.

33.2.2.1 Virtual Host Configuration #

 

The term virtual host refers to Apache's ability to serve multiple universal resource identifiers (URIs) from the same physical machine. This means that several domains, such as www.example.com and www.example.net, are run by a single Web server on one physical machine.

It is common practice to use virtual hosts to save administrative effort (only a single Web server needs to be maintained) and hardware expenses (each domain does not require a dedicated server). Virtual hosts can be name based, IP based, or port based.

To list all existing virtual hosts, use the command apache2ctl -S. This outputs a list showing the default server and all virtual hosts together with their IP addresses and listening ports. Furthermore, the list also contains an entry for each virtual host showing its location in the configuration files.

Virtual hosts can be configured via YaST as described in Section 33.2.3.1.4, “Virtual Hosts” or by manually editing a configuration file. By default, Apache in SUSE Linux Enterprise Server is prepared for one configuration file per virtual host in /etc/apache2/vhosts.d/. All files in this directory with the extension .conf are automatically included to the configuration. A basic template for a virtual host is provided in this directory (vhost.template or vhost-ssl.template for a virtual host with SSL support).

Tip: Always Create a Virtual Host Configuration

It is recommended to always create a virtual host configuration file, even if your Web server only hosts one domain. By doing so, you not only have the domain-specific configuration in one file, but you can always fall back to a working basic configuration by simply moving, deleting, or renaming the configuration file for the virtual host. For the same reason, you should also create separate configuration files for each virtual host.

When using name-based virtual hosts it is recommended to set up a default configuration that will be used when a domain name does not match a virtual host configuration. The default virtual host is the one whose configuration is loaded first. Since the order of the configuration files is determined by file name, start the file name of the default virtual host configuration with an underscore character (_) to make sure it is loaded first (for example: _default_vhost.conf).

The <VirtualHost></VirtualHost> block holds the information that applies to a particular domain. When Apache receives a client request for a defined virtual host, it uses the directives enclosed in this section. Almost all directives can be used in a virtual host context. See http://httpd.apache.org/docs/2.4/mod/quickreference.html for further information about Apache's configuration directives.

33.2.2.1.1 Name-Based Virtual Hosts #

 

With name-based virtual hosts, more than one Web site is served per IP address. Apache uses the host field in the HTTP header that is sent by the client to connect the request to a matching ServerName entry of one of the virtual host declarations. If no matching ServerName is found, the first specified virtual host is used as a default.

The first step is to create a <VirtualHost> block for each different name-based host that you want to serve. Inside each <VirtualHost> block, you will need at minimum a ServerName directive to designate which host is served and a DocumentRoot directive to show where in the file system the content for that host resides.

Example 33.1: Basic Examples of Name-Based VirtualHost Entries #

 

<VirtualHost *:80>
# This first-listed virtual host is also the default for *:80
ServerName www.example.com
ServerAlias example.com
DocumentRoot /srv/www/htdocs/domain
</VirtualHost>

<VirtualHost *:80>
ServerName other.example.com
DocumentRoot /srv/www/htdocs/otherdomain
</VirtualHost>

The opening VirtualHost tag takes the IP address (or fully qualified domain name) as an argument in a name-based virtual host configuration. A port number directive is optional.

The wild card * is also allowed as a substitute for the IP address. When using IPv6 addresses, the address must be included in square brackets.

Example 33.2: Name-Based VirtualHost Directives #

 

<VirtualHost 192.168.3.100:80>
  ...
</VirtualHost>

<VirtualHost 192.168.3.100>
  ...
</VirtualHost>

<VirtualHost *:80>
  ...
</VirtualHost>

<VirtualHost *>
  ...
</VirtualHost>

<VirtualHost [2002:c0a8:364::]>
  ...
</VirtualHost>

33.2.2.1.2 IP-Based Virtual Hosts #

 

This alternative virtual host configuration requires the setup of multiple IPs for a machine. One instance of Apache hosts several domains, each of which is assigned a different IP.

The physical server must have one IP address for each IP-based virtual host. If the machine does not have multiple network cards, virtual network interfaces (IP aliasing) can also be used.

The following example shows Apache running on a machine with the IP 192.168.3.100, hosting two domains on the additional IPs 192.168.3.101 and 192.168.3.102. A separate VirtualHost block is needed for every virtual server.

Example 33.3: IP-Based VirtualHost Directives #

 

<VirtualHost 192.168.3.101>
  ...
</VirtualHost>

<VirtualHost 192.168.3.102>
  ...
</VirtualHost>

Here, VirtualHost directives are only specified for interfaces other than 192.168.3.100. When a Listen directive is also configured for 192.168.3.100, a separate IP-based virtual host must be created to answer HTTP requests to that interface—otherwise the directives found in the default server configuration (/etc/apache2/default-server.conf) are applied.

33.2.2.1.3 Basic Virtual Host Configuration #

 

At least the following directives should be in each virtual host configuration to set up a virtual host. See /etc/apache2/vhosts.d/vhost.template for more options.

ServerName

The fully qualified domain name under which the host should be addressed.

DocumentRoot

Path to the directory from which Apache should serve files for this host. For security reasons, access to the entire file system is forbidden by default, so you must explicitly unlock this directory within a Directory container.

ServerAdmin

E-mail address of the server administrator. This address is, for example, shown on error pages Apache creates.

ErrorLog

The error log file for this virtual host. Although it is not necessary to create separate error log files for each virtual host, it is common practice to do so, because it makes the debugging of errors much easier. /var/log/apache2/ is the default directory for Apache's log files.

CustomLog

The access log file for this virtual host. Although it is not necessary to create separate access log files for each virtual host, it is common practice to do so, because it allows the separate analysis of access statistics for each host. /var/log/apache2/ is the default directory for Apache's log files.

As mentioned above, access to the whole file system is forbidden by default for security reasons. Therefore, explicitly unlock the directories in which you have placed the files Apache should serve—for example the DocumentRoot:

<Directory "/srv/www/www.example.com/htdocs">
  Require all granted
</Directory>

Note: Require all granted

In previous versions of Apache, the statement Require all granted was expressed as:

Order allow,deny
Allow from all

This old syntax is still supported by the mod_access_compat module.

The complete configuration file looks like this:

Example 33.4: Basic VirtualHost Configuration #

 

<VirtualHost 192.168.3.100>
  ServerName www.example.com
  DocumentRoot /srv/www/www.example.com/htdocs
  ServerAdmin webmaster@example.com
  ErrorLog /var/log/apache2/www.example.com_log
  CustomLog /var/log/apache2/www.example.com-access_log common
  <Directory "/srv/www/www.example.com/htdocs">
  Require all granted
  </Directory>
</VirtualHost>

To configure your Web server with YaST, start YaST and select Network Services › HTTP Server. When starting the module for the first time, the HTTP Server Wizard starts, prompting you to make a few basic decisions concerning administration of the server. After having finished the wizard, the HTTP Server Configuration dialog starts each time you call the HTTP Server module. For more information, see Section 33.2.3.2, “HTTP Server Configuration”.

33.2.3.1 HTTP Server Wizard #

 

The HTTP Server Wizard consists of five steps. In the last step of the dialog, you may enter the expert configuration mode to make even more specific settings.

33.2.3.1.1 Network Device Selection #

 

Here, specify the network interfaces and ports Apache uses to listen for incoming requests. You can select any combination of existing network interfaces and their respective IP addresses. Ports from all three ranges (well-known ports, registered ports, and dynamic or private ports) that are not reserved by other services can be used. The default setting is to listen on all network interfaces (IP addresses) on port 80.

Check Open Port In Firewall to open the ports in the firewall that the Web server listens on. This is necessary to make the Web server available on the network, which can be a LAN, WAN, or the public Internet. Keeping the port closed is only useful in test situations where no external access to the Web server is necessary. If you have multiple network interfaces, click Firewall Details to specify on which interface(s) the port(s) should be opened.

Click Next to continue with the configuration.

33.2.3.1.2 Modules #

 

The Modules configuration option allows for the activation or deactivation of the script languages that the Web server should support. For the activation or deactivation of other modules, refer to Section 33.2.3.2.2, “Server Modules”. Click Next to advance to the next dialog.

33.2.3.1.3 Default Host #

 

This option pertains to the default Web server. As explained in Section 33.2.2.1, “Virtual Host Configuration”, Apache can serve multiple virtual hosts from a single physical machine. The first declared virtual host in the configuration file is commonly called the default host. Each virtual host inherits the default host's configuration.

To edit the host settings (also called directives), select the appropriate entry in the table then click Edit. To add new directives, click Add. To delete a directive, select it and click Delete.

Figure 33.1: HTTP Server Wizard: Default Host #

 

Here is list of the default settings of the server:

Document Root

Path to the directory from which Apache serves files for this host. /srv/www/htdocs is the default location.

Alias

Using Alias directives, URLs can be mapped to physical file system locations. This means that a certain path even outside the Document Root in the file system can be accessed via a URL aliasing that path.

The default SUSE Linux Enterprise Server Alias /icons points to /usr/share/apache2/icons for the Apache icons displayed in the directory index view.

ScriptAlias

Similar to the Alias directive, the ScriptAlias directive maps a URL to a file system location. The difference is that ScriptAlias designates the target directory as a CGI location, meaning that CGI scripts should be executed in that location.

Directory

With Directory settings, you can enclose a group of configuration options that will only apply to the specified directory.

Access and display options for the directories /srv/www/htdocs, /usr/share/apache2/icons and /srv/www/cgi-bin are configured here. It should not be necessary to change the defaults.

Include

With include, additional configuration files can be specified. Two Include directives are already preconfigured: /etc/apache2/conf.d/ is the directory containing the configuration files that come with external modules. With this directive, all files in this directory ending in .conf are included. With the second directive, /etc/apache2/conf.d/apache2-manual.conf, the apache2-manual configuration file is included.

Server Name

This specifies the default URL used by clients to contact the Web server. Use a fully qualified domain name (FQDN) to reach the Web server at http://FQDN/ or its IP address. You cannot choose an arbitrary name here—the server must be “known” under this name.

Server Administrator E-Mail

E-mail address of the server administrator. This address is, for example, shown on error pages Apache creates.

After finishing with the Default Host step, click Next to continue with the configuration.

33.2.3.1.4 Virtual Hosts #

 

In this step, the wizard displays a list of already configured virtual hosts (see Section 33.2.2.1, “Virtual Host Configuration”). If you have not made manual changes prior to starting the YaST HTTP wizard, no virtual host is present.

To add a host, click Add to open a dialog in which to enter basic information about the host, such as Server Name, Server Contents Root (DocumentRoot), and the Administrator E-Mail. Server Resolution is used to determine how a host is identified (name based or IP based). Specify the name or IP address with Change Virtual Host ID

Clicking Next advances to the second part of the virtual host configuration dialog.

In part two of the virtual host configuration you can specify whether to enable CGI scripts and which directory to use for these scripts. It is also possible to enable SSL. If you do so, you must specify the path to the certificate as well. See Section 33.6.2, “Configuring Apache with SSL” for details on SSL and certificates. With the Directory Index option, you can specify which file to display when the client requests a directory (by default, index.html). Add one or more file names (space-separated) to change this. With Enable Public HTML, the content of the users public directories (~USER/public_html/) is made available on the server under http://www.example.com/~USER.

Important: Creating Virtual Hosts

It is not possible to add virtual hosts at will. If using name-based virtual hosts, each host name must be resolved on the network. If using IP-based virtual hosts, you can assign only one host to each IP address available.

33.2.3.1.5 Summary #

 

This is the final step of the wizard. Here, determine how and when the Apache server is started: when booting or manually. Also see a short summary of the configuration made so far. If you are satisfied with your settings, click Finish to complete configuration. To change something, click Back until you have reached the desired dialog. Clicking HTTP Server Expert Configuration opens the dialog described in Section 33.2.3.2, “HTTP Server Configuration”.

Figure 33.2: HTTP Server Wizard: Summary #

 

33.2.3.2 HTTP Server Configuration #

 

The HTTP Server Configuration dialog also lets you make even more adjustments to the configuration than the wizard (which only runs if you configure your Web server for the first time). It consists of four tabs described in the following. No configuration option you change here is effective immediately—you always must confirm your changes with Finish to make them effective. Clicking Abort leaves the configuration module and discards your changes.

33.2.3.2.1 Listen Ports and Addresses #

 

In HTTP Service, select whether Apache should be running (Enabled) or stopped (Disabled). In Listen on Ports, Add, Edit, or Delete addresses and ports on which the server should be available. The default is to listen on all interfaces on port 80. You should always check Open Port In Firewall, because otherwise the Web server is not reachable from outside. Keeping the port closed is only useful in test situations where no external access to the Web server is necessary. If you have multiple network interfaces, click Firewall Details to specify on which interface(s) the port(s) should be opened.

With Log Files, watch either the access log file or the error log file. This is useful if you want to test your configuration. The log file opens in a separate window from which you can also restart or reload the Web server. For details, see Section 33.3, “Starting and Stopping Apache”. These commands are effective immediately and their log messages are also displayed immediately.

Figure 33.3: HTTP Server Configuration: Listen Ports and Addresses #

 

33.2.3.2.2 Server Modules #

 

You can change the status (enabled or disabled) of Apache2 modules by clicking Toggle Status. Click Add Module to add a new module that is already installed but not yet listed. Learn more about modules in Section 33.4, “Installing, Activating, and Configuring Modules”.

Figure 33.4: HTTP Server Configuration: Server Modules #

 

33.2.3.2.3 Main Host or Hosts #

 

These dialogs are identical to the ones already described. Refer to Section 33.2.3.1.3, “Default Host” and Section 33.2.3.1.4, “Virtual Hosts”.

If you have done a default installation as described in Section 33.1.2, “Installation”, the following modules are already installed: all base and extension modules, the multiprocessing module Prefork MPM, and the external module mod_python.

You can install additional external modules by starting YaST and choosing Software › Software Management. Now choose View › Search and search for apache. Among other packages, the results list contains all available external Apache modules.

Activate or deactivate particular modules either manually or with YaST. In YaST, script language modules (PHP5, Perl, and Python) need to be enabled or disabled with the module configuration described in Section 33.2.3.1, “HTTP Server Wizard”. All other modules can be enabled or disabled as described in Section 33.2.3.2.2, “Server Modules”.

If you prefer to activate or deactivate the modules manually, use the commands a2enmod MODULE or a2dismod MODULE, respectively. a2enmod -l outputs a list of all currently active modules.

Important: Including Configuration Files for External Modules

If you have activated external modules manually, make sure to load their configuration files in all virtual host configurations. Configuration files for external modules are located under /etc/apache2/conf.d/ and are loaded in /etc/apache2/default-server.conf by default. For more fine-grained control you can comment out the inclusion in /etc/apache2/default-server.conf and add it to specific virtual hosts only. See /etc/apache2/vhosts.d/vhost.template for examples.

All base and extension modules are described in detail in the Apache documentation. Only a brief description of the most important modules is available here. Refer to http://httpd.apache.org/docs/2.4/mod/ to learn details about each module.

SUSE Linux Enterprise Server provides two different multiprocessing modules (MPMs) for use with Apache:

33.4.4.1 Prefork MPM #

 

The prefork MPM implements a non-threaded, preforking Web server. It makes the Web server behave similarly to Apache version 1.x. In this version it isolates each request and handles it by forking a separate child process. Thus problematic requests cannot affect others, avoiding a lockup of the Web server.

While providing stability with this process-based approach, the prefork MPM consumes more system resources than its counterpart, the worker MPM. The prefork MPM is considered the default MPM for Unix-based operating systems.

Important: MPMs in This Document

This document assumes Apache is used with the prefork MPM.

33.4.4.2 Worker MPM #

 

The worker MPM provides a multi-threaded Web server. A thread is a “lighter” form of a process. The advantage of a thread over a process is its lower resource consumption. Instead of only forking child processes, the worker MPM serves requests by using threads with server processes. The preforked child processes are multi-threaded. This approach makes Apache perform better by consuming fewer system resources than the prefork MPM.

One major disadvantage is the stability of the worker MPM: if a thread becomes corrupt, all threads of a process can be affected. In the worst case, this may result in a server crash. Especially when using the Common Gateway Interface (CGI) with Apache under heavy load, internal server errors might occur because of threads being unable to communicate with system resources. Another argument against using the worker MPM with Apache is that not all available Apache modules are thread-safe and thus cannot be used with the worker MPM.

Warning: Using PHP Modules with MPMs

Not all available PHP modules are thread-safe. Using the worker MPM with mod_php is strongly discouraged.

Find a list of all external modules shipped with SUSE Linux Enterprise Server here. Find the module's documentation in the listed directory.

Apache can be extended by advanced users by writing custom modules. To develop modules for Apache or compile third-party modules, the package apache2-devel is required along with the corresponding development tools. apache2-devel also contains the apxs2 tools, which are necessary for compiling additional modules for Apache.

apxs2 enables the compilation and installation of modules from source code (including the required changes to the configuration files), which creates dynamic shared objects (DSOs) that can be loaded into Apache at runtime.

The apxs2 binaries are located under /usr/sbin:

Install and activate a module from source code with the following commands:

cd /path/to/module/source
apxs2 -cia MODULE.c

where -c compiles the module, -i installs it, and -a activates it. Other options of apxs2 are described in the apxs2(1) man page.

In SUSE Linux Enterprise Server, the execution of CGI scripts is only allowed in the directory /srv/www/cgi-bin/. This location is already configured to execute CGI scripts. If you have created a virtual host configuration (see Section 33.2.2.1, “Virtual Host Configuration”) and want to place your scripts in a host-specific directory, you must unlock and configure this directory.

ScriptAlias /cgi-bin/ "/srv/www/www.example.com/cgi-bin/"1

<Directory "/srv/www/www.example.com/cgi-bin/">
 Options +ExecCGI2
 AddHandler cgi-script .cgi .pl3
 Require all granted4
</Directory>

CGI programming differs from "regular" programming in that the CGI programs and scripts must be preceded by a MIME-Type header such as Content-type: text/html. This header is sent to the client, so it understands what kind of content it receives. Secondly, the script's output must be something the client, usually a Web browser, understands—HTML usually, or plain text or images, for example.

A simple test script available under /usr/share/doc/packages/apache2/test-cgi is part of the Apache package. It outputs the content of some environment variables as plain text. Copy this script to either /srv/www/cgi-bin/ or the script directory of your virtual host (/srv/www/www.example.com/cgi-bin/) and name it test.cgi. Edit the file to have #!/bin/sh as the first line.

Files accessible by the Web server should be owned by the user root. For additional information see Section 33.8, “Avoiding Security Problems”. Because the Web server runs with a different user, the CGI scripts must be world-executable and world-readable. Change into the CGI directory and use the command chmod 755 test.cgi to apply the proper permissions.

Now call http://localhost/cgi-bin/test.cgi or http://www.example.com/cgi-bin/test.cgi. You should see the “CGI/1.0 test script report”.

If you do not see the output of the test program but an error message instead, check the following:

To use SSL/TLS with the Web server, you need to create an SSL certificate. This certificate is needed for the authorization between Web server and client, so that each party can clearly identify the other party. To ensure the integrity of the certificate, it must be signed by a party every user trusts.

There are three types of certificates you can create: a “dummy” certificate for testing purposes only, a self-signed certificate for a defined circle of users that trust you, and a certificate signed by an independent, publicly-known certificate authority (CA).

Creating a certificate is a two step process. First, a private key for the certificate authority is generated then the server certificate is signed with this key.

Tip: For More Information

To learn more about concepts and definitions of TLS/SSL, refer to https://httpd.apache.org/docs/2.4/ssl/ssl_intro.html.

33.6.1.1 Creating a “Dummy” Certificate #

 

To generate a dummy certificate, call the script /usr/bin/gensslcert. It creates or overwrites the files listed below. Use gensslcert's optional switches to fine-tune the certificate. Call /usr/bin/gensslcert -h for more information.

• /etc/apache2/ssl.crt/ca.crt

• /etc/apache2/ssl.crt/server.crt

• /etc/apache2/ssl.key/server.key

• /etc/apache2/ssl.csr/server.csr

A copy of ca.crt is also placed at /srv/www/htdocs/CA.crt for download.

Important: For Testing Purposes Only

A dummy certificate should never be used on a production system. Only use it for testing purposes.

33.6.1.2 Creating a Self-Signed Certificate #

 

If you are setting up a secure Web server for an intranet or for a defined circle of users, it is probably sufficient if you sign a certificate with your own certificate authority (CA). Note that visitors to such a site will see a warning like “this is an untrusted site”, as Web browsers do not recognize self-signed certificates.

Important: Self-Signed Certificates

Only use a self-signed certificate on a Web server that is accessed by people who know and trust you as a certificate authority. It is not recommended to use such a certificate for a public shop, for example.

First you need to generate a certificate signing request (CSR). You are going to use openssl, with PEM as the certificate format. During this step, you will be asked for a passphrase, and to answer several questions. Remember the passphrase you enter as you will need it in the future.

sudo openssl req -new > new.cert.csr
Generating a 1024 bit RSA private key
..++++++
.........++++++
writing new private key to 'privkey.pem'
Enter PEM pass phrase:1
Verifying - Enter PEM pass phrase:2
-----
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]:3
State or Province Name (full name) [Some-State]:4
Locality Name (eg, city) []:5
Organization Name (eg, company) [Internet Widgits Pty Ltd]:6
Organizational Unit Name (eg, section) []:7
Common Name (for example server FQDN, or YOUR name) []:8
Email Address []:9

Please enter the following 'extra' attributes
to be sent with your certificate request
A challenge password []:10
An optional company name []:11

1	Fill in your passphrase,
2	...fill it in once more (and remember it).
3	Fill in your 2 letter country code, such as GB or CZ.
4	Fill in the name of the state where you live.
5	Fill in the city name, such as Prague.
6	Fill in the name of the organization you work for.
7	Fill in your organization unit, or leave blank if you have none.
8	Fill in either the domain name of the server, or your first and last name.
9	Fill in your work e-mail address.
10	Leave the challenge password empty, otherwise you will need to enter it every time you restart the Apache Web server.
11	Fill in the optional company name, or leave blank.

Now you can generate the certificate. You are going to use openssl again, and the format of the certificate is the default PEM.

Procedure 33.3: Generating the Certificate #

 

1. Export the private part of the key to new.cert.key. You will be prompted for the passphrase you entered when creating the certificate signing request (CSR).

   sudo openssl rsa -in privkey.pem -out new.cert.key

2. Generate the public part of the certificate according to the information you filled out in the signing request. The -days option specifies the length of time before the certificate expires. You can revoke a certificate, or replace one before it expires.

   sudo openssl x509 -in new.cert.csr -out new.cert.cert -req \
   -signkey new.cert.key -days 365

3. Copy the certificate files to the relevant directories, so that the Apache server can read them. Make sure that the private key /etc/apache2/ssl.key/server.key is not world-readable, while the public PEM certificate /etc/apache2/ssl.crt/server.crt is.

   sudo cp new.cert.cert /etc/apache2/ssl.crt/server.crt
   sudo cp new.cert.key /etc/apache2/ssl.key/server.key

Tip: Public Certificate Location

The last step is to copy the public certificate file from /etc/apache2/ssl.crt/server.crt to a location where your users can access it to incorporate it into the list of known and trusted CAs in their Web browsers. Otherwise a browser complains that the certificate was issued by an unknown authority.

openssl req -new -newkey rsa:2048 -nodes -keyout newkey.pem -out newreq.pem

The default port for SSL and TLS requests on the Web server side is 443. There is no conflict between a “regular” Apache listening on port 80 and an SSL/TLS-enabled Apache listening on port 443. In fact, HTTP and HTTPS can be run with the same Apache instance. Usually separate virtual hosts are used to dispatch requests to port 80 and port 443 to separate virtual servers.

Important: Firewall Configuration

Do not forget to open the firewall for SSL-enabled Apache on port 443. This can be done with YaST as described in Section 16.4.1, “Configuring the Firewall with YaST”.

The SSL module is enabled by default in the global server configuration. In case it has been disabled on your host, activate it with the following command: a2enmod ssl. To finally enable SSL, the server needs to be started with the flag “SSL”. To do so, call a2enflag SSL (case-sensitive!). If you have chosen to encrypt your server certificate with a password, you should also increase the value for APACHE_TIMEOUT in /etc/sysconfig/apache2, so you have enough time to enter the passphrase when Apache starts. Restart the server to make these changes active. A reload is not sufficient.

The virtual host configuration directory contains a template /etc/apache2/vhosts.d/vhost-ssl.template with SSL-specific directives that are extensively documented. Refer to Section 33.2.2.1, “Virtual Host Configuration” for the general virtual host configuration.

To get started, copy the template to /etc/apache2/vhosts.d/MYSSL-HOST.conf and edit it. Adjusting the values for the following directives should be sufficient:

33.6.2.1 Name-Based Virtual Hosts and SSL #

 

By default it is not possible to run multiple SSL-enabled virtual hosts on a server with only one IP address. Name-based virtual hosting requires that Apache knows which server name has been requested. The problem with SSL connections is, that such a request can only be read after the SSL connection has already been established (by using the default virtual host). As a result, users will receive a warning message stating that the certificate does not match the server name.

SUSE Linux Enterprise Server comes with an extension to the SSL protocol called Server Name Indication (SNI) addresses this issue by sending the name of the virtual domain as part of the SSL negotiation. This enables the server to “switch” to the correct virtual domain early and present the browser the correct certificate.

SNI is enabled by default on SUSE Linux Enterprise Server. To enable Name-Based Virtual Hosts for SSL, configure the server as described in Section 33.2.2.1.1, “Name-Based Virtual Hosts” (note that you need to use port 443 rather than port 80 with SSL).

Important: SNI Browser Support

SNI must also be supported on the client side. However, SNI is supported by most browsers, except for certain older browsers. For more information, see https://en.wikipedia.org/wiki/Server_Name_Indication#Support.

To configure handling of non-SNI capable browsers, use the directive SSLStrictSNIVHostCheck. When set to on in the server configuration, non-SNI capable browser will be rejected for all virtual hosts. When set to on within a VirtualHost directive, access to this particular host will be rejected.

When set to off in the server configuration, the server will behave as if not having SNI support. SSL requests will be handled by the first virtual host defined (for port 443).

If there are vulnerabilities found in the Apache software, a security advisory will be issued by SUSE. It contains instructions for fixing the vulnerabilities, which in turn should be applied when possible. The SUSE security announcements are available from the following locations:

By default in SUSE Linux Enterprise Server, the DocumentRoot directory /srv/www/htdocs and the CGI directory /srv/www/cgi-bin belong to the user and group root. You should not change these permissions. If the directories are writable for all, any user can place files into them. These files might then be executed by Apache with the permissions of wwwrun, which may give the user unintended access to file system resources. Use subdirectories of /srv/www to place the DocumentRoot and CGI directories for your virtual hosts and make sure that directories and files belong to user and group root.

By default, access to the whole file system is denied in /etc/apache2/httpd.conf. You should never overwrite these directives, but specifically enable access to all directories Apache should be able to read. For details, see Section 33.2.2.1.3, “Basic Virtual Host Configuration”. In doing so, ensure that no critical files, such as password or system configuration files, can be read from the outside.

Interactive scripts in Perl, PHP, SSI, or any other programming language can essentially run arbitrary commands and therefore present a general security issue. Scripts that will be executed from the server should only be installed from sources the server administrator trusts—allowing users to run their own scripts is generally not a good idea. It is also recommended to do security audits for all scripts.

To make the administration of scripts as easy as possible, it is common practice to limit the execution of CGI scripts to specific directories instead of globally allowing them. The directives ScriptAlias and Option ExecCGI are used for configuration. The SUSE Linux Enterprise Server default configuration does not allow execution of CGI scripts from everywhere.

All CGI scripts run as the same user, so different scripts can potentially conflict with each other. The module suEXEC lets you run CGI scripts under a different user and group.

When enabling user directories (with mod_userdir or mod_rewrite) you should strongly consider not allowing .htaccess files, which would allow users to overwrite security settings. At least you should limit the user's engagement by using the directive AllowOverRide. In SUSE Linux Enterprise Server, .htaccess files are enabled by default, but the user is not allowed to overwrite any Option directives when using mod_userdir (see the /etc/apache2/mod_userdir.conf configuration file).

For a list of new features in Apache 2.4, refer to http://httpd.apache.org/docs/2.4/new_features_2_4.html. Information about upgrading from version 2.2 to 2.4 is available at http://httpd.apache.org/docs-2.4/upgrading.html.

More information about external Apache modules that are briefly described in Section 33.4.5, “External Modules” is available at the following locations:

More information about developing Apache modules or about getting involved in the Apache Web server project are available at the following locations:

If you experience difficulties specific to Apache in SUSE Linux Enterprise Server, take a look at the Technical Information Search at https://www.suse.com/support. The history of Apache is provided at https://httpd.apache.org/ABOUT_APACHE.html. This page also explains why the server is called Apache.