Browse Prior Art Database

Unauthorized Key Zero

IP.com Disclosure Number: IPCOM000052749D
Original Publication Date: 1981-Jul-01
Included in the Prior Art Database: 2005-Feb-11
Document File: 1 page(s) / 11K

Publishing Venue

IBM

Related People

Russell, TT: AUTHOR

Abstract

IBM System/370 protection key 0 is sometimes considered to convey too much storage referencing authority for many paths within operating system programs. This can lead to the existence of operating system integrity exposures.

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 98% of the total text.

Page 1 of 1

Unauthorized Key Zero

IBM System/370 protection key 0 is sometimes considered to convey too much storage referencing authority for many paths within operating system programs. This can lead to the existence of operating system integrity exposures.

This article describes a new hardware mode called ""unauthorinazed key zero'' (UKZ) which can be implemented with a new bit in the System/ 370 PSW (program status word) and two new privileged instructions, Unauthorize-Key-Zero (UKZ) and Authorize-Key-Zero (AKZ). The UKZ instruction would remove the authority of a program running under PSW key 0 to access, except fetch of non- fetch-protected storage, storage blocks with keys 1 through 15. AKZ would restore that authority, so that key zero has its current authority to access storage blocks protected by any key 0 through 15. Thus, the UKZ instruction would set and the AKZ instruction would reset the new bit in the PSW, so that the hardware would know which mode of key zero operation is in effect. Programs running with any other key (i.e., 1 through 15) would operate the same as in current System/37O.

UKZ instructions can then be selectively inserted in the paths of system control programs for which references, with the exception of fetches of non-fetch- protected storage, to storage blocks having keys other than key 0 are erroneous. If such an erroneous reference occurs while in UKZ mode, the normal System/370 protection exception is generated and a potential operating sy...