This document provides an overview of access control and database security. It discusses different access control models including discretionary access control, mandatory access control, role-based access control, and attribute-based access control. It also covers access control elements, functions, and examples of how access control is implemented in UNIX and Windows systems. The document then discusses database security topics like relational databases, SQL, database access controls, and statistical database security and inference problems. It concludes with sections on database encryption and homomorphic encryption.

1. ‫أكاديمية الحكومة اإللكترونية الفلسطينية‬
The Palestinian eGovernment Academy
www.egovacademy.ps
Security Tutorial
Sessions 11
PalGov © 2011 1

2. About
This tutorial is part of the PalGov project, funded by the TEMPUS IV program of the
Commission of the European Communities, grant agreement 511159-TEMPUS-1-
2010-1-PS-TEMPUS-JPHES. The project website: www.egovacademy.ps
Project Consortium:
Birzeit University, Palestine
University of Trento, Italy
(Coordinator )
Palestine Polytechnic University, Palestine Vrije Universiteit Brussel, Belgium
Palestine Technical University, Palestine
Université de Savoie, France
Ministry of Telecom and IT, Palestine
University of Namur, Belgium
Ministry of Interior, Palestine
TrueTrust, UK
Ministry of Local Government, Palestine
Coordinator:
Dr. Mustafa Jarrar
Birzeit University, P.O.Box 14- Birzeit, Palestine
Telfax:+972 2 2982935 mjarrar@birzeit.eduPalGov © 2011
2

3. © Copyright Notes
Everyone is encouraged to use this material, or part of it, but should properly
cite the project (logo and website), and the author of that part.
No part of this tutorial may be reproduced or modified in any form or by any
means, without prior written permission from the project, who have the full
copyrights on the material.
Attribution-NonCommercial-ShareAlike
CC-BY-NC-SA
This license lets others remix, tweak, and build upon your work non-
commercially, as long as they credit you and license their new creations
under the identical terms.
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4. Tutorial 5:
Information Security
Session 11: Access Control
Session 9 Outline:
• Access Control
• Overview of Database Security
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5. Tutorial 5: Session 11: Access Control
This session will contribute to the following
ILOs:
• A: Knowledge and Understanding
• a2: Defines security standards and policies.
• B: Intellectual Skills
• b3: Design end-to-end secure and available systems.
• D: General and Transferable Skills
• d2: Systems configurations.
• d3: Analysis and identification skills.
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6. Access Control
• “The prevention of unauthorized use of a
resource, including the prevention of use of
a resource in an unauthorized manner“ [1]
• Central element of computer security
• Systems have users and groups
– Authenticate to system
– Assigned access rights to certain resources on
system
– Logging and auditing is very important (why?)
1. Computer Security: Principles and Practice, by William Stallings and Lawrie Brown. Published by Pearson/Prentice Hall, © 2008.
ISBN: 0-13-600424-5.
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7. Access Control Principles
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8. Different Access Control Policies
• Discretionary access control (DAC):
– an entity might have access rights that permit another
entity to access some resource (done by its own volition).
• Mandatory access control (MAC):
– may not enable another entity to access that resource.
• Role-based access control (RBAC):
– based on the roles.
– ABAC: Administrative RBACK .
(See [2] The ARBAC97 model for role-based administration of roles for more details)
• Attribute Based Access Control (ABAC):
– Generalisation of RBAC to use any attributes
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9. Access Control Requirements
• Separation of duty between different entities
• Reliable input with validation
• Fine specifications.
• Coarse specifications
• Least restrictive privilege
• Open /closed policies
• Admin policies
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10. Access Control Elements
• A subject is an entity that can access objects
– A process representing user/application
– Ex. (Owner, group, world in unix/linux systems)
• Object - access controlled resource
– E.G. Files, directories, records, programs etc
– Number/type depend on environment
• Access rights are actions in which subjects
accesses objects
– E.G. Read, write, execute, delete, create,
search…etc.
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11. Discretionary Access Control
• Uses access matrix
– Rows : lists subjects in one dimension.
– Columns: lists objects in anther dimension
– Content of cells specifies access rights
(actions) of the specified subject to that
object
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12. Access Control Model
Access Control Model [1]
1. Computer Security: Principles and Practice, by William Stallings and Lawrie Brown. Published by Pearson/Prentice Hall, © 2008.
ISBN: 0-13-600424-5.
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13. Different Functions of Access Control
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14. Domains of Protection
• Each object can be associated with access
rights / actions
• In access matrix view
– Each row defines a protection domain
– But not necessarily just a user
– May be a limited subset of user’s rights
– Applied to a more restricted process
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15. Example: UNIX File
• UNIX files are administered using inodes
– May have several names for same inode
– Control structure with key info on file
– Have inode table / list for all files on a disk
• Directories considered as a hierarchical tree
– May contain files or other directories
– Are a file of names and inode numbers
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16. UNIX File Access Control (chmod command)
• Chmod 742
• r w x r_ _ _ w _
U G O
– r : read
– w : write
– x : execute
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17. UNIX File Access Control (SetUID) and (SetGID)
• Unix super-user
– access control restrictions does not apply …
• Directory sticky bit
– For directories, it limits rename/move/delete to
owner
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18. UNIX Access Control Lists
• Can specify any number of additional users
/ groups and permissions
• Modern UNIX systems support Access
Control Lists
• Group perms also set max ACL perms
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19. Mandatory Access Control (MAC(
• Based on comparing security labels
– Depends on resource sensitivity
• Needs security clearance
• Person with MAC level on a resource may not
enable other entities to use or even reach this
resource
– Example military reasons.
– Or for financial data.
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20. Mac Features and Attributes
• Appropriate for extremely secure systems good
• For egov. Critical data applications.
• Mac attributes.
• Security label can be changed by only
administrators, not data owners.
• Objects are assigned security level that
reflects its relative sensitivity, confidentiality,
and protection value.
• Users can read from a lower classification
than the one they are granted.
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21. Mac Features and Attributes (cont)
• All users can write to a higher classification.
• All users are given read/write access to objects
only of the same classification.
• Access is authorized or restricted to objects
based on different parameters like:
• time of day depending on the labeling on the
resource and the user's credentials.
• security characteristics of the HTTP client
(originating IP address or domain, etc.)
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22. MS Windows Vista Example (MAC)
• It is called Mandatory Integrity Control (MIC) in
Windows Vista.
• Model, which ensures integrity by controlling
writes and deletions.
• Label on Subjects: When a user logs on,
Windows Vista assigns an integrity SID to the
users access token. (Included in the SID is an integrity label that
determines the level of access the token (and thus the user) can achieve.)
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23. MS Windows Vista Example (MAC)
• Label on Objects: Objects are also assigned an
integrity SID, which is stored in the system access
control list (SACL) of the objects security descriptor.
The label in the SID specifies the integrity level of the
object. (such as files, pipes, processes, threads, registry keys, services, etc.)
• Access Control Policy: To write to or delete an object,
the integrity level of subject must be equal to or
greater than the object’s level.
• Vista checks MAC first, if passed, it then checks DAC
(e.g. access control list).
• MAC provides a layer of access control in addition
to DAC; it does not replace DAC.
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24. Windows VISTA Integrity Levels :
• Windows Vista defines six integrity levels (IL): Low,
Medium, High, and System.
• Un-trusted.
• Low: everyone (i.e. world).
• Medium: standard users, authenticated users.
• High: local service, network service, elevated users.
• System: system services.
• Trusted Installer.
Usually, child processes inherit the integrity level of their parents, unless the
executable program running in the child process has a lower integrity level.
For example, all the downloaded executables will run with Low integrity
level because the labels of the executable programs are marked as Low
when they are downloaded from the Internet.
• Default levels: Objects that lack an integrity label are treated as medium
by the operating system. This prevents low integrity code from modifying unlabeled
objects PalGov © 2011 24

25. Role-Based Access Control
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26. Role-Based Access Control
R1 R2 R3 Rn
U1 X
U2 X
U3 X X X
U4 X
X X
Un
Objects
R1 R2 Rn F1 F2 D1 D2 Pi
R1 control owner
Owner
read
control
R2 control Write stop
Rn seek
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27. Role-Based Access Control
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28. NIST RBAC Model
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29. Case Study: RBACK for your ORG
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30. ABAC
• More general model than RBAC, where
permissions are assigned to any attribute,
not just a user’s role, e.g
– If Age .GT. 18 then grant access to ID
WEBSITE
– If Level of Assurance .GE.2 then grant read
access to database.
– If Level of Assurance .GE. 3 then grant update
access to database
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31. Tutorial 5:
Information Security
Session 9: Access Control
Session 9 Outline:
• Access Control
• Overview of Database Security
PalGov © 2011 31

32. Overview of Database Security
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33. Relational Databases
• Have multiple tables linked by identifiers/keys
• Constructed from tables of data
• Use a query language (PL/SQL) to access data
items meeting specified criteria, add, delete,
change…
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34. A Relational Database Example
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35. Elements of Relational Databases
• Primary key
• Foreign key
• Tuple / row / record
• Relation / table / file
• Attribute / column / field
• View / virtual table
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36. Structured Query Language (SQL)
• Structure query language (SQL)
– Standardized language to define, manipulate,
and query data in a relational database
– Originally developed by IBM in the mid-1970s
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37. Database Access Control
• DBMS provide access control for database
• Assume have authenticated user
• DBMS provides specific access rights to portions
of the database
• Can support a range of policies:
– centralized / decentralized administration
– ownership-based administration
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38. SQL Access Controls
• Two commands:
– GRANT { privileges | role } [ON table] TO { user |
role | PUBLIC } [IDENTIFIED BY password]
[WITH GRANT OPTION]
• e.g. GRANT SELECT ON ANY TABLE TO ricflair
– REVOKE { privileges | role } [ON table] FROM {
user | role | PUBLIC }
• e.g. REVOKE SELECT ON ANY TABLE FROM ricflair
• Typical access rights are:
– SELECT, INSERT, UPDATE, DELETE,
REFERENCES
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39. Role-Based Access Control
• Role-based access control works well for
DBMS
• Categories of database users:
– Administrator
– Application owner
– End user
• DB RBAC must manage roles and their
users (RBAC on Microsoft's SQL server)
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40. Inference Case
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41. Statistical Databases
• Provides statistical data like averages and
counts.
• Two types:
– Pure statistical database
– Ordinary database with statistical access
• Some users have normal access, others statistical
• We should allow statistical results without
accessing individual entries.
• Inference is a security problem
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42. Statistical Database Security
• A statistical query is a query that produces a
value calculated over a query set
• One can Use A logical formula over the
values of attributes
– E.G. (Sex=male) AND ((major=cs) OR (major=ee))
• Query set X(C) of characteristic formula C, is
the set of records matching C
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43. Statistical Database Example [1]
1. Computer Security: Principles and Practice, by William Stallings and Lawrie Brown. Published by Pearson/Prentice Hall, © 2008.
ISBN: 0-13-600424-5.
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44. Solving Inference Problems
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45. Database Encryption
• Databases are valuable resources and can be
protected by multiple layers of security:
– firewalls,
– authentication,
– O/S access control systems,
– DB access control systems,
– and database encryption
• Can encrypt
– Entire database -
– Individual fields -
– Records (rows) or columns (attributes)
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46. Database Encryption
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47. Homomorphic Encryption (1)
• With normal Database encryption transfer
– Servers that power a cloud can't do any work on it that way.
• With homomorphic encryption, a company
could encrypt its entire database of e-mails
and upload it to a cloud.
– It is possible to analyze data without decrypting it.
– The key is to encrypt the data in such a way that
performing a mathematical operation on the
encrypted information and then decrypting the
result produces the same answer as performing
an analogous operation on the unencrypted data.
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48. Homomorphic Encryption (2)
• The correspondence between the
operations on unencrypted data and the
operations to be performed on encrypted
data is known as a homomorphism.
– "In principle," says Gentry, an IBM researcher,
"something like this could be used to secure
operations over the Internet.“ [2]
[2] (http://www.technologyreview.com/computing/37197/)
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49. Bibliography
1. Computer Security: Principles and
Practice, by William Stallings and Lawrie
Brown. Published by Pearson/Prentice
Hall, © 2008. ISBN: 0-13-600424-5.
2. Homomorphic Encryption Making cloud
computing more secure
(http://www.technologyreview.com/computing/37197/),
accessed 20/1/2012.
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50. Summary
• In this session we discussed the
following:
– Introduced access control principles
• subjects, objects, access rights
– Discretionary access controls
• access matrix, access control lists (ACLs),
capability tickets
• UNIX traditional and ACL mechanisms
– Role-based access control and ABACK
– Overview of Database Security/Control
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51. Thanks
Radwan Tahboub
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