CGI: Introduction
VBScript and JavaScript CGI
Coral-Mini Server
Apache, with the release of 2.2.18, made a small change. Quoting from the change log: "Added shebang check for '! so that .vbs scripts work as CGI." Hidden in that statement is the ability not only to run VBScripts as CGI but also JavaScripts. A more profound implication is the ability to create dynamic web sites using Apache alone, removing the bloat of PHP and MySQL. This tutorial revisits the mini-server series and updates the basic Apache server to include the new Apache 2.2.21 core, and the control architecture from The Uniform Server Coral-8 series.
This new mini-server, Coral-Mini, is used for running the examples for this tutorial. These examples provide an introduction to CGI scripting. They are written in VBScript and JavaScript. Before we look at CGI scripting, we will explore the mini-server architecture.
Coral-Mini Server Specification
Coral-Mini Server has the following specification:
- Server is portable and can be installed on a USB memory stick.
- Server core uses Apache 2.2.21
- Serves by default HTML pages.
- Dynamic web pages implemented using either VBScript or JavaScript
- Capability to use .htaccess files for configuration
- Capability to include external pages.
- Uses a file-based database.
- Underlying technology used is hidden.
- The server logs all web requests and errors.
- Includes only the minimum modules to meet specification.
Download
Download the Coral-Mini server from SourceForge Project Page and save the file coral_mini_server.exe to any folder of your choice.
Extract the files
Double click on coral_mini_server.exe, which starts the extraction process. No need to change the folder destination. Click extract; this creates a new folder MiniServer which contains four files and four folders.
Files:
- Start_Coral_Mini.exe - Double click to start the server
- Stop_Coral_Mini.exe - Double click to stop the server
- tutorial.bat - Displays this tutorial in the default browser
- READ_ME.txt - Provides information for changing ports.
Folders:
- apache2 - Apache server files and configuration
- control - File to start and stop server
- docs - Tutorial and working scripts from tutorial. Licenses for server.
- www - Root folder. Apache serves files from this folder.
Test
Testing is straight forward.
- Start the server by double clicking on Start_Coral_Mini.exe This automatically configures the server paths.
- Start a web browser.
- Type http://localhost:8081/ into the browser address bar.
- The default page index.html is displayed.
- Stop the server by double clicking on Stop_Coral_Mini.exe
Apache modules
Apache comes with a vast array of modules. A full list and description can be found in the Apache Docs. Modules used in the Coral-Mini server are listed below. Note that the core module is part of the main binary (program) and loaded by default.
Key modules are highlighted in bold. These are loaded using Apache's configuration file httpd.conf.
| Module Name | Description |
|---|---|
| core | Core Apache HTTP Server features that are always available; included in the binary (program). |
| mpm_winnt.c | WinNT MPM is part of the Windows Apache core. A Multi-Processing Module (MPM), it is the default for Windows NT operating systems. It uses a single control process which launches a single child process which in turn creates threads to handle requests. (This is the reason you will see two Apache processes in task manager). |
| authz_host_module | Group authorizations based on host (name or IP address). Required to restrict access to folders, etc. |
| mod_dir | Provides for "trailing slash" redirects and serving directory index files. (Optional, but nice to have. Otherwise a user needs to type index.html on entry to a folder or for initial web site access. It prevents this error message: The requested URL / was not found on this server.) |
| mod_log_config | Logging of the requests made to the server. (Not required for server operation however extremely useful to see what the server is doing.) |
| mod_mime | Associates the requested file name extension with the file's behavior (handlers and filters) and content (mime-type, language, character set and encoding) Note that without this module, the file will be served as plain text. The DefaultType is text/plain |
| mod_rewrite | Provides rewriting of requested URLs on the fly. Allows masking of file extensions; for example, a request for index.htm results in page index.vbs being run on the server and the result returned as index.htm |
| mod_cgi | Provides an interface for running CGI scripts. Scripts that require running are targeted using the AddHandler directive. This directive associates file extensions with CGI scripts. |
Configuring Apache
When Apache is started, it is supplied with the location and name of a configuration file. This overrides the default location compiled into the program. It's common practice to name the file httpd.conf and place it in a sub-folder named conf. Coral-Mini uses this convention.
Coral-Mini server uses this configuration file: MiniServer\apache2\conf\httpd.conf
Note: Apache’s example configuration file contains a lot of detailed information. I personally find this confusing and have removed this detail.
| httpd.conf located in folder: *\MiniServer\apache2\conf | Comments |
|---|---|
|
# File name: http.conf |
General information. A reminder what the configuration is for. |
|
#======================================================= |
Lists all modules to be loaded. Note: For some modules the order is important. Order of priority is from bottom to top; hence if a module is dependent on another it should come first in the list. |
|
# ======================================== |
These settings are common to the main server. Most settings in this section have defaults. However I like to see what I am using, hence list them regardless.
|
|
# ======================================== |
Most settings in this section have defaults. However again I like to see what I am using, hence list them regardless. |
|
# ======================================== |
Each directory to which Apache has access can be configured with respect to which services and features are allowed and/or disabled in that directory (including its sub-directories). Apache has access to all folders and files on the drive where it is installed, hence the first Directory directive is very restrictive:
The only way to enable access is to target each folder in turn and open it up as required. Second Directory directive targets folder www which contains your web site.
The AccessFileName directive defines the file name to use for secondary configuration files. By convention the name is .htaccess Access to these files is restricted using the Files directive. The regex also prevents .htpasswd files from being viewed by Web clients. |
|
# ======================================== |
In conjunction with the mime_module, the directive TypesConfig is used to specify a file which maps extensions onto MIME types. Note that without the module and this file, served pages will be in plain text. |
|
# ======================================== |
This sets up the appropriate log format (what details are logged) and specifies the log file name and location. Note: debug eats disk space hence warn is a reasonable setting. |
Configuring Apache CGI - Overview
The following provides a general overview of how to configuring Apache to run CGI scripts. In order to run CGI programs, Apache requires configuration directives to permit CGI execution.
Note: All three methods require the mod_cgi module to be enabled as shown below:
LoadModule cgi_module modules/mod_cgi.so
You can select one of the following methods to permit CGI execution.
Method 1: ScriptAlias
The ScriptAlias directive tells Apache that a particular directory is set aside for CGI programs. Apache now assumes every file in this directory is a CGI program. When a page from this folder is requested, Apache will attempt to execute it using the appropriate program.
The ScriptAlias directive looks like:
ScriptAlias /cgi-bin "C:/UniServer/cgi-bin/"
The directive defines a URL prefix (cgi-bin) that is mapped to a particular folder (directory). ScriptAlias informs Apache that everything under that URL prefix will be considered a CGI program.
For example, if the URL http://localhost/cgi-bin/test.pl is requested, Apache will attempt to execute the perl file C:/UniServer/cgi-bin/test.pl and return the output.
Similarly, if the URL http://localhost/cgi-bin/test.vbs is requested, Apache will attempt to execute the VBScript file C:/UniServer/cgi-bin/test.vbs and return the output.
Method 2: Folders
On hosted sites, for security reasons, CGI programs are restricted to ScriptAlias'ed folders. However you can run CGI programs from any folder. As an alternative to ScriptAlias you can use the Options directive (inside your main server configuration file) to specify that CGI execution is permitted in a particular directory.
<Directory "C:/UniServer/www/somedir/"> Options ExecCGI </Directory>
The Options ExecCGI directive informs Apache to permit the execution of CGI files.
Method 3: .htaccess
Using .htaccess files allow you to set configuration directives on a per-directory basis. Apache looks for this file in a folder from which it is serving and applies the directives found. To enable the use of .htaccess files, edit the Apache configuration files as follows:
Change or add the AllowOverride directive in a specific folder directive; for example, www as shown below:
<Directory "C:/UniServer/www/"> Options Indexes Includes AllowOverride All </Directory>
If not already included, add the following block of code to prevent .htaccess and .htpasswd files from being viewed by Web clients:
<Files ~ "^\.ht">
Order allow,deny
Deny from all
Satisfy All
</Files>
With the above directives in-place you can now use .htacces files. Create an .htaccess file in the folder where you want to run CGI scripts and add the following line:
Options +ExecCGI Options +FollowSymlinks
This tells Apache that execution of CGI programs is permitted in this folder.
Note: All of The Uniform Servers have been pre-configured to allow the use of .htaccess files.
AddHandler
Using either of the above methods, Apache will attempt to execute every file as a CGI script. This includes files such as css and images. Clearly these are not CGI scripts and would produce errors when executed. To avoid this you need to inform the server what files are genuine CGI scripts by using the AddHandler directive.
AddHandler cgi-script .cgi .pl .vbs
The above AddHandler directive informs the server to treat all files with a cgi, pl or vbs extension as CGI programs.
Test folder and .htaccess
The tutorial examples require a test folder and .htaccess file.
- In folder MiniServer\www create a new folder vbs_test in which you will put your tutorial scripts.
- Inside this folder create a new .htaccess file with the following content:
| Note: | .htaccess content |
| If you have problems creating the .htaccess file, copy the one from folder www.
Edit the file: Delete all lines and add the three lines shown on right and save. |
AddHandler cgi-script .vbs Options +ExecCGI Options +FollowSymlinks |
Summary
The above has shown how to configure Apache to run CGI scripts.
Running VBScripts requires an .htaccess file placed in the directory containing the scripts. This file enables script execution and has the following content:
AddHandler cgi-script .vbs Options +ExecCGI Options +FollowSymlinks
Although tutorial examples specifically refer to the Coral-Mini Server they can be run on any of The Uniform Servers that contain Apache 2.2.18 or above. Just create the test folder and add the .htaccess file as described above.
Where to next
The next page details how to format a VBScript for running as a CGI script.