Chapter 24 Database Security Copyright 2011 Pearson Education Inc Publishing as Pearson Addison Wesley Introduction to Database Security Issues Threats to databases Loss of integrity Loss of availability Loss of confidentiality To protect databases against these types of threats four kinds of countermeasures can be implemented Access control Inference control Flow control Encryption Copyright 2011 Ramez Elmasri and Shamkant Navathe Introduction to Database Security Issues A DBMS typically includes a database security and authorization subsystem that is responsible for ensuring the security portions of a database against unauthorized access Two types of database security mechanisms Discretionary security mechanisms Mandatory security mechanisms Copyright 2011 Ramez Elmasri and Shamkant Navathe Introduction to Database Security Issues The security mechanism of a DBMS must include provisions for restricting access to the database as a whole This function is called access control and is handled by creating user accounts and passwords to control login process by the DBMS Copyright 2011 Ramez Elmasri and Shamkant Navathe Introduction to Database Security Issues Another security issue is data encryption which is used to protect sensitive data such as credit card numbers that is being transmitted via some type communication network The data is encoded using some encoding algorithm An unauthorized user who access encoded data will have difficulty deciphering it but authorized users are given decoding or decrypting algorithms or keys to decipher data Copyright 2011 Ramez Elmasri and Shamkant Navathe 1 2 Database Security and the DBA The database administrator DBA is the central authority for managing a database system The DBA s responsibilities include granting privileges to users who need to use the system classifying users and data in accordance with the policy of the organization The DBA is responsible for the overall security of the database system Copyright 2011 Ramez Elmasri and Shamkant Navathe 1 2 Database Security and the DBA 2 The DBA has a DBA account in the DBMS Sometimes these are called a system or superuser account These accounts provide powerful capabilities such as 1 Account creation 2 Privilege granting 3 Privilege revocation 4 Security level assignment Action 1 is access control whereas 2 and 3 are discretionary authorization and 4 is used to control mandatory authorization Copyright 2011 Ramez Elmasri and Shamkant Navathe 1 3 Access Protection User Accounts and Database Audits Whenever a person or group of persons need to access a database system the individual or group must first apply for a user account The DBA will then create a new account id and password for the user if he she deems there is a legitimate need to access the database The user must log in to the DBMS by entering account id and password whenever database access is needed Copyright 2011 Ramez Elmasri and Shamkant Navathe 1 3 Access Protection User Accounts and Database Audits 2 The database system must also keep track of all operations on the database that are applied by a certain user throughout each login session To keep a record of all updates applied to the database and of the particular user who applied each update we can modify system log which includes an entry for each operation applied to the database that may be required for recovery from a transaction failure or system crash Copyright 2011 Ramez Elmasri and Shamkant Navathe 1 3 Access Protection User Accounts and Database Audits 3 If any tampering with the database is suspected a database audit is performed A database audit consists of reviewing the log to examine all accesses and operations applied to the database during a certain time period A database log that is used mainly for security purposes is sometimes called an audit trail Copyright 2011 Ramez Elmasri and Shamkant Navathe Discretionary Access Control Based on Granting and Revoking Privileges The typical method of enforcing discretionary access control in a database system is based on the granting and revoking privileges Copyright 2011 Ramez Elmasri and Shamkant Navathe 2 1Types of Discretionary Privileges The account level At this level the DBA specifies the particular privileges that each account holds independently of the relations in the database The relation level or table level At this level the DBA can control the privilege to access each individual relation or view in the database Copyright 2011 Ramez Elmasri and Shamkant Navathe 2 1Types of Discretionary Privileges 2 The privileges at the account level apply to the capabilities provided to the account itself and can include the CREATE SCHEMA or CREATE TABLE privilege to create a schema or base relation the CREATE VIEW privilege the ALTER privilege to apply schema changes such adding or removing attributes from relations the DROP privilege to delete relations or views the MODIFY privilege to insert delete or update tuples and the SELECT privilege to retrieve information from the database by using a SELECT query Copyright 2011 Ramez Elmasri and Shamkant Navathe 2 1Types of Discretionary Privileges 3 The second level of privileges applies to the relation level This includes base relations and virtual view relations The granting and revoking of privileges generally follow an authorization model for discretionary privileges known as the access matrix model where The rows of a matrix M represents subjects users accounts programs The columns represent objects relations records columns views operations Each position M i j in the matrix represents the types of privileges read write update that subject i holds on object j Copyright 2011 Ramez Elmasri and Shamkant Navathe 2 1Types of Discretionary Privileges 4 To control the granting and revoking of relation privileges each relation R in a database is assigned and owner account which is typically the account that was used when the relation was created in the first place The owner of a relation is given all privileges on that relation In SQL2 the DBA can assign and owner to a whole schema by creating the schema and associating the appropriate authorization identifier with that schema using the CREATE SCHEMA command The owner account holder can pass privileges on any of the owned relation to other users by granting privileges to their accounts Copyright 2011 Ramez Elmasri and Shamkant Navathe 2 1Types of Discretionary Privileges 5 In SQL the following types of privileges can be
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