Security & Protection
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This document discusses protection and security in operating systems. It covers goals of protection like ensuring each object can only be accessed correctly by allowed processes. The principle of least privilege is introduced. Domain structure and access matrix models for protection are described. Access control matrix consists of subjects, objects, and access operations. Access control list and capability list are derivative and better forms. Security threats like intruders attempting to breach security are addressed. Categories of security violations like breach of confidentiality and methods of attacks are outlined. References from textbooks and websites on related topics are listed at the end.
Security & Protection
- 1. Protection & Security Organized By: V.A. V.A. CSED,TU
- 2. Disclaimer This is NOT A COPYRIGHT MATERIAL Content has been taken mainly from the following books: Operating Systems Concepts By Silberschatz & Galvin , Operating systems By D M Dhamdhere, System Programming By John J Donovan etc… VA. CSED,TU
- 3. Protection – Goals & Principle Each Object has a Unique Name and can be accessed through a well-defined set of Operations. Ensure that each Object is accessed correctly and only by those Processes that are allowed to do so. Guiding Principle – Principle of Least Privilege Programs, users and systems should be given just enough privileges to perform their tasks VA. CSED,TU
- 4. Domain Structure Access-right = <object-name, rights-set> where rights-set is a subset of all valid operations that can be performed on the object. Domain = Set of Access-Rights Domain can be realized in variety of ways: Each User, Each Process and Each Procedure. VA. CSED,TU
- 5. Access Matrix View Protection as a MATRIX (access matrix) Rows represent Domains Columns represent Objects Access (i, j) is the Set Of Operations that a process executing in Domaini can invoke on Objectj VA. CSED,TU
- 6. Access Control Matrix Access control matrix consists of triple parts such as subject, object, and access operation. A SUBJECT is an Active Entity in a computer system such as User, Program, Process and Thread. An OBJECT is a Passive Entity or System Resource such as File, Directory, Database Record and Printer. In Access Control Matrix’s schema, the Subjects and Objects are placed in a table. Each row represents a Subject and each column represents an Object. The data inside the table are Set Of Access Operations such as read, write, and execute. The access operations are responsible for interactions between subjects and objects. VA. CSED,TU
- 7. Access Matrix VA. CSED,TU
- 8. Use of Access Matrix If a Process in Domain Di tries to do “op” on object Oj, then “op” must be in the ACCESS MATRIX. Can be Expanded to DYNAMIC PROTECTION. Operations to ADD, DELETE access rights. Special Access Rights: Owner of Oi Copy op from Oi to Oj Control – Di can modify Dj access rights Transfer – Switch from domain Di to Dj VA. CSED,TU
- 9. Access Matrix – Showing Switch VA. CSED,TU
- 10. Role Based Access Control VA. CSED,TU
- 11. Sample Access Matrix The Derivative forms of access control matrix such as Access Control List (ACL) and Capability List (C-list) are better applied. VA. CSED,TU
- 12. Access Control List VA. CSED,TU
- 13. ACL When we look for Insurance Data we can write: VA. CSED,TU
- 14. C-List VA. CSED,TU
- 15. C-List When we look for Alice’s C-list we can write: VA. CSED,TU
- 16. ACL vs CL VA. CSED,TU
- 17. Security Security must consider External Environment of the System and protect the system resources Intruders (crackers) attempt to breach security THREAT is potential security violation ATTACK is attempt to breach security Attack can be accidental or malicious Easier to protect against accidental than malicious misuse VA. CSED,TU
- 18. Security Violations Categories Breach of confidentiality Breach of integrity Breach of availability Theft of service Denial of service Methods Masquerading (breach authentication) Replay attack Message modification Man-in-the-middle attack Session hijacking VA. CSED,TU
- 19. Security Attacks VA. CSED,TU
- 20. Reference List Operating Systems Concepts By Silberschatz & Galvin, Operating systems By D M Dhamdhere, System Programming By John J Donovan, www.os-book.com www.cs.jhu.edu/~yairamir/cs418/os2/sld001.htm http://gaia.ecs.csus.edu/~zhangd/oscal/pscheduling.html http://www.edugrid.ac.in/iiitmk/os/os_module03.htm http://williamstallings.com/OS/Animations.html etc… VA. CSED,TU