Access Control: Difference between revisions

Latest revision as of 00:43, 8 September 2005

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.

Operating Systems

access control for files and processes, ring management, IO-management, memory, processors s.o. as deep as the hardware permits it
matrix is often used to manage this
not usable for large organizations, because the administration becomes to difficult for humans

Do it by groups and/or roles !

Groups and Roles

every user fits into one or some categories
rights have to be defined for these categories
user gets role and fits in group

What is the difference ?

There‘s no final definition.

Access Control Lists

just one column of the access control matrix stored for every resource
not very performant
difficult to administrate

Unix

simple list: owner, group, world for user – not for programs
indirect method for programs: SUID and SGID
or by user dummy

Win NT

more attributes (take ownership, change permission, delete)
arrangement in domains with trust between them

Capabilities

just one row of the access control matrix stored for every resource
some experimental implementatios in the 70s
today a comeback in the form of public key certificates

Win 2k/XP

used combined with ACL
group policies
active directory

Understands

Granularity	control access at the right level file access ↔ database file different systems, different access controls
Sandboxing	access to a restricted environment
Proof-Carrying-Code	tests the behaviour of a program
Object Request Brokers	controlling calls for several objects/resources

Problems

problem if any level doesn’t controll access
"Every system has at least one bug – Windows much more."
"The most serious bug is sitting in front of the monitor."
smashing the stack
bypassing denied permissions
trojans
structural defects in operating systems (Windows user has to be admin for installation)

Background

Decisions were made one time, consequences work eternally, but environment changes very rapidly.

Sometimes, also a developer uses the easier way to reach a goal.

Sometimes it‘s just user friendly.

@@ Line 1: / Line 1: @@
-It has to be controled on every IT System, who and what has access to which resource.
+Who and what has access to which resource has to be controled on every IT System.
+==Introduction==
-'''Contents:'''
-*[[Access Control by Hardware]]
+Controlled are issues like
-*[[Access Control by Operating System]]
-*[[General Problems]]
+*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.
+==Operating Systems==
+*access control for files and processes, ring management, IO-management, memory, processors s.o. as deep as the hardware permits it
+*matrix is often used to manage this
+*not usable for large organizations, because the administration becomes to difficult for humans
+Do it by groups and/or roles !
+===Groups and Roles===
+*every user fits into one or some categories
+*rights have to be defined for these categories
+*user gets role and fits in group
+What is the difference ?
+There‘s no final definition.
+===Access Control Lists===
+*just one column of the access control matrix stored for every resource
+*not very performant
+*difficult to administrate
+====Unix====
+*simple list: owner, group, world     for user – not for programs
+*indirect method for programs: SUID and SGID
+*or by user dummy
+====Win NT====
+*more attributes (take ownership, change permission, delete)
+*arrangement in domains with trust between them
+===Capabilities===
+*just one row of the access control matrix stored for every resource
+*some experimental implementatios in the 70s
+*today a comeback in the form of public key certificates
+====Win 2k/XP====
+*used combined with ACL
+*group policies
+*active directory
+===Understands===
+{|border="0" cellspacing="0" cellpadding="5"
+|valign="top" |Granularity
+|
+*control access at the right level
+*file access ↔ database file
+*different systems, different access controls
+|-
+|Sandboxing
+|access to a restricted environment
+|-
+|Proof-Carrying-Code
+|tests the behaviour of a program
+|-
+|Object Request Brokers
+|controlling calls for several objects/resources
+|}
+==Problems==
+*problem if any level doesn’t controll access
+*"Every system has at least one bug – Windows much more."
+*"The most serious bug is sitting in front of the monitor."
+*smashing the stack
+*bypassing denied permissions
+*trojans
+*structural defects in operating systems (Windows user has to be admin for installation)
+===Background===
+Decisions were made one time, consequences work eternally, but environment changes very rapidly.
+Sometimes, also a developer uses the easier way to reach a goal.
+Sometimes it‘s just user friendly.