Configure and manage custom HTTP error pages

The configuration of customized error pages is done by uploading a zip file containing all required files to the Submenu – Error Pages.

• The HTML files need to be organized and named in a special form so that Airlock Gateway can use them as error pages.
• If the HTML code of the error pages refers to images, style sheets, or other external files that are added to the archive, the corresponding HTTP links must be relative. All additional files have to be included in the zip file.

• It is possible to configure error pages globally for all virtual hosts or to configure specific error pages for certain virtual hosts:
• Airlock Gateway will prioritize error pages that are specific to the corresponding virtual host.
• If there is no host-specific error page, the version of the global error page is used, if configured. If none is configured, Airlock Gateway uses its generic error page.

Error pages generated by back-end applications may leak internal information about a system's setup and configuration (e.g. platform, system paths, stack traces, or deployed frameworks). Such information is valuable for potential attackers.
To prevent information leakage by default, Airlock Gateway replaces error pages generated by back-ends or ICAP services used in Back-end View.

If you disable error page replacement or configure replacement rules accordingly, the error pages of the back-ends will be displayed instead.

A zip file with a clean and correctly named set of custom error pages can be downloaded using the Download customization template button.

Error pages must be named as follows:

400.html
401.html
403.html
404.html
429.html
500.html
502.html
503.html
maintenance.html  

• The zip file containing the error pages needs to be of the following form:
• The global error pages are on the top level of the archive i.e. not in a sub-directory.
• If there are virtual-host-specific error pages, there needs to be a directory that is named like the virtual host, e.g. www.webapp.virtinc.com.
• The archive can contain image files, style sheets, etc. in the top-level or the corresponding virtual host directory.

It is possible to add a colon-separated port number, e.g. www.webapp.virtinc.com:443. This allows configuring different error pages for HTTP and HTTPS. Note that some operating systems do not support colon-separated filenames.

The following screenshot shows an uploaded example zip file with global and virtual-hosts-specific error pages:

• The virtual host www.webapp.virtinc.com contains its own complete set of error pages and a specific logo they refer to.
• The virtual host www.other.webapp.virtinc.com, on the other hand, has its own error page only for error 400 and uses the global ones for other error codes.
• All other virtual hosts use the global error pages plus a maintenance page that are on the top level. A default CSS stylesheet and a favicon icon is also available in this example.

1. If custom error pages are activated, click the Download button to download them in a zip file and use them as a starting point for modification. Alternatively, click Download customization templates to start with a clean set of error page templates.
2. Make your changes and upload your custom error pages in a zip file using the Upload button.
3. Activate the configuration with the Activate button.

Uploading a new error-page zip file will replace all current files. Therefore, the error-page zip file must contain all required files.

Custom error pages are part of the Airlock Gateway configuration and can be restored from older configuration files if available.

• To manage error pages, see Submenu – Error Pages.
• For error page replacement, see Section – Error page replacement.