DATABASE SECURITY - Database Design and Development: An Essential Guide for IT Professionals - page 502

Department Employee

PRIVILEGE Record Record

Read
Update
Insert
Delete

Y
N
N
N

Y
N
Y
N

Authorization Rule
Subject: Samantha Jenkins

Samantha Jenkins
(password JNK271)

Will Rogers
(password WRG346) PRIVILEGE

Read
Update
Insert
Delete

Y
N
Y
N

Y
N
N
N

Authorization Rule
Object: Employee Record

Figure 16-6 Implementation of authorization rules.

rization table for either subjects or users. On the other hand, an authorization table
for objects can also do the job. A DBMS may implement authorization rules through
either of the two tables or both.
Figure 16-6 presents both options for implementing authorization rules. Note
how you can derive the same rule authorizing Samantha Jenkins to access the
EMPLOYEE table with read and insert privileges.

Enforcing Authorization Rules We have authorization rules in an authorization
matrix or in the form of authorization tables for users or objects. How are the rules
enforced by the DBMS? A highly protected privilege module with unconstrained
access to the entire database exists to enforce the authorization rules. This is the
arbiter or security enforcer module, although it might not go by those names in
every DBMS. The primary function of the arbiter is to interrupt and examine every
database operation, check against the authorization matrix, and either allow or deny
the operation.
The arbiter module goes through a sequence of interrogations to determine the
action to be taken about an operation. Figure 16-7 provides a sample interrogation
list.
Suppose after going through the interrogation sequence, the arbiter has to deny
a database operation. What are the possible courses of action? Naturally, the
particular course of action to be adopted depends on a number of factors and the
circumstances. Here are some basic options provided in DBMSs:

• If the sensitivity of the attempted violation is high, terminate the transaction
and lock the workstation.
• For lesser violations, send appropriate message to user.
• Record attempted security breaches in the log file.