EnGarde Secure Linux Professional 1.2

Marketed as an office security product, EnGarde Secure Linux is a small office server distribution with a number of security features. These include a secure mail server, a secure web server supporting virtual hosts, a file server, DNS capabilities and a small office firewall.

With web administration capabilities and services for Microsoft client OSes, EnGarde offers a powerful setup in an easy-to-use box, and it accomplishes most of this using free software.

These days, one of the biggest things I look for with Linux distributions is how well they have solved the installation process. The installation of EnGarde was quite easy to accomplish. The text-based installer is much like the old Red Hat installations used to be. During the installation, you select what type of machine you would like to build (you can, of course, build combinations). You can choose from a firewall, a network intrusion detection system (using Snort), a database server (running MySQL), a secure mail (SMTP, POP, IMAP) server, a VPN appliance, a DNS server or a secure web server. The proper components and only the proper components are installed, meaning you have a trimmed-up system on the network installed with a reasonable set of defaults.

Configuration is done via the WebTool interface, though you can always access the system via the command line. X is not installed. After your initial reboot, you configure a few parameters on the host via a web browser, and then reboot again. From there you can configure various server parameters, including the certificates for your secure web or mail servers, firewall parameters, or the like.

The WebTool UI is also an easy-to-use system interface, allowing you to check on your system, control services and view system parameters. As an example, you can control access to the SSH dæmon via the UI, controlling the addresses, users and groups who can connect. System logs and backups also can be controlled from the WebTool interface.

Several server components that can be installed and managed using EnGarde Secure Linux are worth noting. One of the features of the secure e-mail server is SquirrelMail, a web-based e-mail solution. SquirrelMail can provide a well-sized workgroup or user base with a feature-rich and platform-independent e-mail solution that is managed on a secure platform. The WebTool UI can be used to configure the e-mail system, including the SSL enhanced POP3 and IMAP servers and the Postfix SMTP server.

An additional component is BIND 8.2.5 used as a DNS server. This can provide a rich set of DNS features, including split and dynamic DNS, all of which are configurable by the WebTool UI. Furthermore, the web server, along with virtual hosts and SSL certificates, is managed by the WebTool UI, giving users a powerful interface for a complete server. Lastly, the UI can be used to configure the firewall and port redirection rules, but at this time this feature isn't as mature as it could be.

As part of the default installation, EnGarde installs a number of components that many administrators wind up installing later. The first is the OpenWall patch, which provides a non-executable stack. This works well to prevent a number of the common buffer-overflow exploits typically seen, but it doesn't stop exploits such as heap exploits, format string attacks or configuration problems.

Secondly, the Tripwire host-based intrusion detection system is installed in the base installation. Tripwire builds a database and monitors files for changes, keeping track of several characteristics for each file. This method goes well beyond the MD5 sums and dates monitored by the RPM tool in verify mode, and it provides a rigorous monitor of your host's filesystem.

Lastly, the LIDS access control system is installed with the default kernel. You can also boot a standard kernel lacking the LIDS system, should you need to. LIDS provides a way to minimize the impact any attacker could cause.

Best practices are also in play, as you would expect. Connections via FTP are disabled by default, Telnet is not installed, and SSH connections are controlled via private key authentication. The UI generates and downloads a private SSH key that you can then use with your SSH client to connect to the EnGarde server.

Commercial Guardian Digital customers are allowed to use the Guardian Digital Secure Network to keep their system current. As new packages are released you can install them via the UI, making it easy to stay up-to-date with the patches as they're released.

One concern I typically have with an automatic update system is lost configurations or the use of a new one. As an example, OpenSSH moved from /etc/sshd_config to /etc/ssh/sshd_config as its dæmon configuration file. During an update it's not clear if the configuration file is being respected or not, so when something breaks you're left to fix it via the CLI. This can, of course, break the UI interaction and spiral downward quickly if you're not careful. Still, Guardian seems to have managed this pretty well; I was able to update my OpenSSH installation using this mechanism without any errors or loss of connectivity.