Access Control

Who and what has access to which resource has to be controled on every IT System.

Introduction

Controlled are issues like

• access to files
• access to memory
• execution of programs
• sharing data with other principals

Access is controlled at different levels:

• application
• middleware
• operating system
• hardware

The complexity of administering Access Control is growing complexity.

Hardware Protection

Protection Problem: preventing one process from interfering with another

Confinement Problem: preventing programs communicating outwards through other than authorized channels (e.g. memory overwriting)

Intel 80x86 (Pentium) Processors

8088/8086:	any running program controlled the whole machine
80286:	protected segment addressing and rings, operating systems could run proper
80386:	built-in virtual memory and large memory segments, treated as a 32-bit flat-address machine

Rings

• process in ring 0 (kernel) manages privilege level of other processes
• ring 1, 2 usually system processes (e.g. win32 subsys, virtual DOS)
• ring 3 user programs
• gates between rings for executing code at an other level

Other Procssors

Acorn Risc Machine (ARM)

• most commonly licensed to third-party vendors of embedded systems
• 32-bit processor
• separate banks of registers for user and system processes
• hardware protection can be customized

Security Processors

• hardware security support for cryptography and access control
• authorized state
• password covered memory access

s.o.

Problems

problem if any level doesn’t controll access