Tandem Computers and the Safeguard C2 Prank

The C2 Security Initiative

• In 1985, Tandem was working hard to achieve a C2 security rating under the Department of Defense's Orange Book guidelines (TCSEC).
• My primary responsibility was writing Tandem's first Security Administration Guide, translating the distributed Guardian OS environment's operational security for government evaluators.
• I worked closely on this project with Bill Lamb, who led the developer side of the C2 project and translated requirements into code via Tandem's Safeguard security software.

The April Fools' Day Black Hole

• Safeguard was retrofitted onto Guardian OS, which was originally built for high-speed open communication rather than strict cryptographic permissions.
• While writing the manual, I discovered that specific combinations of explicit GRANT and DENY commands could create a file descriptor state overriding standard owner privileges.
• For April Fools' Day, I used this logic gap to initialize an un-deletable file named APRLFOOL in everyone's home directory. The permission deadlock was so absolute that not even the directory owners could delete it.
• The stunt nearly got me fired as management panicked during the high-stakes audit. However, once resolved, the engineering team used the exploit to patch the Safeguard API leak, hardening the operating system.

Cupertino Culture & Watering Holes

• Tandem's presence dominated Cupertino, so much so that the local Chili's at Vallco Fashion Mall ran an endless skillet promotion spelled "NonStop Fajitas" in honor of Tandem's systems.
• Engineers from Tandem, Apple, and HP frequently gathered to debate systems over craft ale at the nearby Faultline Brewing Company or at the legendary Tied House on San Pedro Square in San Jose.