| Oracle® Database Security Guide 10g Release 1 (10.1) Part Number B10773-01 |
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| Oracle® Database Security Guide 10g Release 1 (10.1) Part Number B10773-01 |
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View PDF |
Authorization includes primarily two processes:
This chapter introduces the basic concepts and mechanisms for placing or removing such limitations on users, individually or in groups, in the following sections:
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How Privileges Are Acquired and Used |
Introduction to Privileges, |
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How Roles Are Acquired, Used, and Restricted |
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How and Why Resource Limits Are Applied to Users |
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How Profiles Are Determined and Used |
| See Also:
Chapter 10, "Administering User Privileges, Roles, and Profiles", discusses how to configure and administer privileges, roles, and profiles for users, including DBAs and application programmers. |
A privilege is a right to execute a particular type of SQL statement or to access another user's object. Some examples of privileges include the right to:
You grant privileges to users so these users can accomplish tasks required for their jobs. You should grant a privilege only to a user who absolutely requires that privilege to accomplish necessary work. Excessive granting of unnecessary privileges can compromise security. A user can receive a privilege in two different ways:
SCOTT the privilege to insert records into the employees table.employees table to the role named clerk, which in turn you can grant to users scott and brian.Because roles allow for easier and better management of privileges, you should normally grant privileges to roles and not to specific users.
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There are six major categories of privileges, some with significant subcategories:
A system privilege is the right to perform a particular action, or to perform an action on any schema objects of a particular type. For example, the privileges to create tablespaces and to delete the rows of any table in a database are system privileges. There are over 100 distinct system privileges to manage, as described in the following subsections:
You can grant or revoke system privileges to users and roles. If you grant system privileges to roles, then you can use the roles to manage system privileges. For example, roles permit privileges to be made selectively available.
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Note: In general, you grant system privileges only to administrative personnel and application developers. End users normally do not require and should not have the associated capabilities. |
Use either of the following to grant or revoke system privileges to users and roles:
GRANT and REVOKE
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Only two types of users can grant system privileges to other users or revoke such privileges from them:
ADMIN OPTIONGRANT ANY PRIVILEGEA schema object privilege is a privilege or right to perform a particular action on a specific schema object.
Different object privileges are available for different types of schema objects. The privilege to delete rows from the departments table is an example of an object privilege.
Some schema objects, such as clusters, indexes, triggers, and database links, do not have associated object privileges. Their use is controlled with system privileges. For example, to alter a cluster, a user must own the cluster or have the ALTER ANY CLUSTER system privilege.
The following subsections discuss granting and revoking such privileges:
Object privileges that apply to specific schema objects are discussed in the following sections:
Schema object privileges can be granted to and revoked from users and roles. If you grant object privileges to roles, you can make the privileges selectively available. Object privileges for users and roles can be granted or revoked using the following:
GRANT and REVOKE, respectivelySee Also:
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A user automatically has all object privileges for schema objects contained in his or her schema. A user can grant any object privilege on any schema object he or she owns to any other user or role. A user with the GRANT ANY OBJECT PRIVILEGE can grant or revoke any specified object privilege to another user with or without the GRANT OPTION of the GRANT statement. Otherwise, the grantee can use the privilege, but cannot grant it to other users.
For example, assume user SCOTT has a table named t2:
SQL>GRANT grant any object privilege TO U1; SQL> connect u1/u1 Connected. SQL> GRANT select on scott.t2 \TO U2; SQL> SELECT GRANTEE, OWNER, GRANTOR, PRIVILEGE, GRANTABLE FROM DBA_TAB_PRIVS WHERE TABLE_NAME = 'employees'; GRANTEE OWNER ------------------------------ ------------------------------ GRANTOR PRIVILEGE GRA ------------------------------ ---------------------------------------- --- U2 SCOTT SCOTT SELECT NO
A schema object and its synonym are equivalent with respect to privileges. That is, the object privileges granted for a table, view, sequence, procedure, function, or package apply whether referencing the base object by name or using a synonym.
For example, assume there is a table jward.emp with a synonym named jward.employee, and the user jward issues the following statement:
GRANT SELECT ON emp TO swilliams;
The user swilliams can query jward.emp by referencing the table by name or using the synonym jward.employee:
SELECT * FROM jward.emp; SELECT * FROM jward.employee;
If you grant object privileges on a table, view, sequence, procedure, function, or package to a synonym for the object, the effect is the same as if no synonym were used. For example, if jward wanted to grant the SELECT privilege for the emp table to swilliams, jward could issue either of the following statements:
GRANT SELECT ON emp TO swilliams; GRANT SELECT ON employee TO swilliams;
If a synonym is dropped, all grants for the underlying schema object remain in effect, even if the privileges were granted by specifying the dropped synonym.
Schema object privileges for tables enable table security at the DML or DDL level of operation, as discussed in the following subsections:
You can grant privileges to use the DELETE, INSERT, SELECT, and UPDATE DML operations on a table or view. Grant these privileges only to users and roles that need to query or manipulate a table's data.
You can restrict INSERT and UPDATE privileges for a table to specific columns of the table. With selective INSERT, a privileged user can insert a row with values for the selected columns. All other columns receive NULL or the column's default value. With selective UPDATE, a user can update only specific column values of a row. Selective INSERT and UPDATE privileges are used to restrict a user's access to sensitive data.
For example, if you do not want data entry users to alter the salary column of the employees table, selective INSERT or UPDATE privileges can be granted that exclude the salary column. Alternatively, a view that excludes the salary column could satisfy this need for additional security.
| See Also:
Oracle Database SQL Reference for more information about these DML operations |
The ALTER, INDEX, and REFERENCES privileges allow DDL operations to be performed on a table. Because these privileges allow other users to alter or create dependencies on a table, you should grant privileges conservatively. A user attempting to perform a DDL operation on a table may need additional system or object privileges. For example, to create a trigger on a table, the user requires both the ALTER TABLE object privilege for the table and the CREATE TRIGGER system privilege.
As with the INSERT and UPDATE privileges, the REFERENCES privilege can be granted on specific columns of a table. The REFERENCES privilege enables the grantee to use the table on which the grant is made as a parent key to any foreign keys that the grantee wishes to create in his or her own tables. This action is controlled with a special privilege because the presence of foreign keys restricts the data manipulation and table alterations that can be done to the parent key. A column-specific REFERENCES privilege restricts the grantee to using the named columns (which, of course, must include at least one primary or unique key of the parent table).
| See Also:
"Data Integrity" in Oracle Database Concepts for more information about primary keys, unique keys, and integrity constraints |
A view is a presentation of data selected from one or more tables (possibly including other views). A view shows the structure of the underlying tables as well as the selected data, and can be thought of as the result of a stored query. The view contains no actual data but rather derives what it shows from the tables and views on which it is based. A view can be queried, and the data it represents can be changed. Data in a view can be updated or deleted, and new data inserted. These operations directly alter the tables on which the view is based and are subject to the integrity constraints and triggers of the base tables.
Data Manipulation Language (DML) object privileges for tables can be applied similarly to views. Schema object privileges for a view allow various DML operations, which as noted affect the base tables from which the view is derived. These privileges are discussed in the following subsections:
To create a view, you must meet the following requirements:
GRANT OPTION clause or appropriate system privileges with the ADMIN OPTION clause. If you have not, grantees cannot access your view.
To use a view, you require appropriate privileges only for the view itself. You do not require privileges on base objects underlying the view.
Views add two more levels of security for tables, column-level security and value-based security:
employees table to show only the employee_id, last_name, and manager_id columns:
CREATE VIEW employees_manager AS SELECT last_name, employee_id, manager_id FROM employees;
WHERE clause in the definition of a view displays only selected rows of base tables. Consider the following two examples:
CREATE VIEW lowsal AS SELECT * FROM employees WHERE salary < 10000;
The LOWSAL view allows access to all rows of the employees table that have a salary value less than 10000. Notice that all columns of the employees table are accessible in the LOWSAL view.
CREATE VIEW own_salary AS SELECT last_name, salary FROM employees WHERE last_name = USER;
In the own_salary view, only the rows with an last_name that matches the current user of the view are accessible. The own_salary view uses the user pseudocolumn, whose values always refer to the current user. This view combines both column-level security and value-based security.
EXECUTE is the only schema object privilege for procedures, including standalone procedures and functions as well as packages. Grant this privilege only to users who need to execute a procedure or to compile another procedure that calls a desired procedure. To create and manage secure and effective use of procedure privileges, you need to understand the following subsections:
A user with the EXECUTE object privilege for a specific procedure can execute the procedure or compile a program unit that references the procedure. No runtime privilege check is made when the procedure is called. A user with the EXECUTE ANY PROCEDURE system privilege can execute any procedure in the database.
Privileges to execute procedures can be granted to a user through roles.
A procedure's owner, called the "definer," must have all the necessary object privileges for referenced objects. If the owner grants to another user the right to use that procedure, the owner's object privileges for the objects referenced by the procedure apply to that user's exercise of the procedure. These are termed "definer's rights."
The user of a procedure who is not its owner is termed the "invoker." Additional privileges on referenced objects are required for invoker's rights procedures, but not for definer's rights procedures.
A user of a definer's rights procedure requires only the privilege to execute the procedure and no privileges on the underlying objects that the procedure accesses, because a definer's rights procedure operates under the security domain of the user who owns the procedure, regardless of who is executing it. The procedure's owner must have all the necessary object privileges for referenced objects. Fewer privileges have to be granted to users of a definer's rights procedure, resulting in tighter control of database access.
You can use definer's rights procedures to control access to private database objects and add a level of database security. By writing a definer's rights procedure and granting only EXECUTE privilege to a user, the user can be forced to access the referenced objects only through the procedure.
At runtime, the privileges of the owner of a definer's rights stored procedure are always checked before the procedure is executed. If a necessary privilege on a referenced object has been revoked from the owner of a definer's rights procedure, then the procedure cannot be executed by the owner or any other user.
| See Also:
"Triggers" in Oracle Database Concepts |
An invoker's rights procedure executes with all of the invoker's privileges. Roles are enabled unless the invoker's rights procedure was called directly or indirectly by a definer's rights procedure. A user of an invoker's rights procedure needs privileges (either directly or through a role) on objects that the procedure accesses through external references that are resolved in the invoker's schema.
The invoker needs privileges at runtime to access program references embedded in DML statements or dynamic SQL statements, because they are effectively recompiled at runtime.
For all other external references, such as direct PL/SQL function calls, the owner's privileges are checked at compile time, and no runtime check is made. Therefore, the user of an invoker's rights procedure needs no privileges on external references outside DML or dynamic SQL statements. Alternatively, the developer of an invoker's rights procedure only needs to grant privileges on the procedure itself, not on all objects directly referenced by the invoker's rights procedure.
Many packages provided by Oracle, such as most of the DBMS_* packages, run with invoker's rights--they do not run as the owner (SYS) but rather as the current user. However, some exceptions exist such as the DBMS_RLS package.
You can create a software bundle that consists of multiple program units, some with definer's rights and others with invoker's rights, and restrict the program entry points (controlled step-in). A user who has the privilege to execute an entry-point procedure can also execute internal program units indirectly, but cannot directly call the internal programs.
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To create a procedure, a user must have the CREATE PROCEDURE or CREATE ANY PROCEDURE system privilege. To alter a procedure, that is, to manually recompile a procedure, a user must own the procedure or have the ALTER ANY PROCEDURE system privilege.
The user who owns the procedure also must have privileges for schema objects referenced in the procedure body. To create a procedure, you must have been explicitly granted the necessary privileges (system or object) on all objects referenced by the procedure. You cannot have obtained the required privileges through roles. This includes the EXECUTE privilege for any procedures that are called inside the procedure being created.
Triggers also require that privileges to referenced objects be granted explicitly to the trigger owner. Anonymous PL/SQL blocks can use any privilege, whether the privilege is granted explicitly or through a role.
A user with the EXECUTE object privilege for a package can execute any public procedure or function in the package and access or modify the value of any public package variable. Specific EXECUTE privileges cannot be granted for a package's constructs. Therefore, you may find it useful to consider two alternatives for establishing security when developing procedures, functions, and packages for a database application. These alternatives are described in the following examples.
This example shows four procedures created in the bodies of two packages.
CREATE PACKAGE BODY hire_fire AS PROCEDURE hire(...) IS BEGIN INSERT INTO employees . . . END hire; PROCEDURE fire(...) IS BEGIN DELETE FROM employees . . . END fire; END hire_fire; CREATE PACKAGE BODY raise_bonus AS PROCEDURE give_raise(...) IS BEGIN UPDATE employees SET salary = . . . END give_raise; PROCEDURE give_bonus(...) IS BEGIN UPDATE employees SET bonus = . . . END give_bonus; END raise_bonus;
Access to execute the procedures is given by granting the EXECUTE privilege for the package, using the following statements:
GRANT EXECUTE ON hire_fire TO big_bosses; GRANT EXECUTE ON raise_bonus TO little_bosses;
Granting EXECUTE privilege granted for a package provides uniform access to all package objects.
This example shows four procedure definitions within the body of a single package. Two additional standalone procedures and a package are created specifically to provide access to the procedures defined in the main package.
CREATE PACKAGE BODY employee_changes AS PROCEDURE change_salary(...) IS BEGIN ... END; PROCEDURE change_bonus(...) IS BEGIN ... END; PROCEDURE insert_employee(...) IS BEGIN ... END; PROCEDURE delete_employee(...) IS BEGIN ... END; END employee_changes; CREATE PROCEDURE hire BEGIN employee_changes.insert_employee(...) END hire; CREATE PROCEDURE fire BEGIN employee_changes.delete_employee(...) END fire; PACKAGE raise_bonus IS PROCEDURE give_raise(...) AS BEGIN employee_changes.change_salary(...) END give_raise; PROCEDURE give_bonus(...) BEGIN employee_changes.change_bonus(...) END give_bonus;
Using this method, the procedures that actually do the work (the procedures in the employee_changes package) are defined in a single package and can share declared global variables, cursors, on so on. By declaring top-level procedures hire and fire, and an additional package raise_bonus, you can grant selective EXECUTE privileges on procedures in the main package:
GRANT EXECUTE ON hire, fire TO big_bosses; GRANT EXECUTE ON raise_bonus TO little_bosses;
The following subsections describe the use of privileges for types, methods, and objects:
Oracle defines system privileges shown in Table 5-1 for named types (object types, VARRAYs, and nested tables):
The CONNECT and RESOURCE roles include the CREATE TYPE system privilege. The DBA role includes all of these privileges.
The only object privilege that applies to named types is EXECUTE. If the EXECUTE privilege exists on a named type, a user can use the named type to:
The EXECUTE privilege permits a user to invoke the type's methods, including the type constructor. This is similar to EXECUTE privilege on a stored PL/SQL procedure.
Method execution is the same as any other stored PL/SQL procedure.
To create a type, you must meet the following requirements:
CREATE TYPE system privilege to create a type in your schema or the CREATE ANY TYPE system privilege to create a type in another user's schema. These privileges can be acquired explicitly or through a role.EXECUTE object privileges to access all other types referenced within the definition of the type, or have been granted the EXECUTE ANY TYPE system privilege. The owner cannot have obtained the required privileges through roles.EXECUTE privileges to the referenced types with the GRANT OPTION or the EXECUTE ANY TYPE system privilege with the ADMIN OPTION. If not, the type owner has insufficient privileges to grant access on the type to other users.To create a table using types, you must meet the requirements for creating a table and these additional requirements:
EXECUTE object privileges to access all types referenced by the table, or have been granted the EXECUTE ANY TYPE system privilege. The owner cannot have obtained the required privileges through roles.EXECUTE privileges to the referenced types with the GRANT OPTION or the EXECUTE ANY TYPE system privilege with the ADMIN OPTION. If not, the table owner has insufficient privileges to grant access on the type to other users.
Assume that three users exist with the CONNECT and RESOURCE roles:
User1 performs the following DDL in his schema:
CREATE TYPE type1 AS OBJECT ( attr1 NUMBER); CREATE TYPE type2 AS OBJECT ( attr2 NUMBER); GRANT EXECUTE ON type1 TO user2; GRANT EXECUTE ON type2 TO user2 WITH GRANT OPTION;
User2 performs the following DDL in his schema:
CREATE TABLE tab1 OF user1.type1; CREATE TYPE type3 AS OBJECT ( attr3 user1.type2); CREATE TABLE tab2 ( col1 user1.type2);
The following statements succeed because user2 has EXECUTE privilege on user1's TYPE2 with the GRANT OPTION:
GRANT EXECUTE ON type3 TO user3; GRANT SELECT on tab2 TO user3;
However, the following grant fails because user2 does not have EXECUTE privilege on user1's TYPE1 with the GRANT OPTION:
GRANT SELECT ON tab1 TO user3;
User3 can successfully perform the following statements:
CREATE TYPE type4 AS OBJECT ( attr4 user2.type3); CREATE TABLE tab3 OF type4;
Existing column-level and table-level privileges for DML statements apply to both column objects and row objects. Oracle defines the privileges shown in Table 5-2 for object tables:
Similar table privileges and column privileges apply to column objects. Retrieving instances does not in itself reveal type information. However, clients must access named type information in order to interpret the type instance images. When a client requests such type information, Oracle checks for EXECUTE privilege on the type.
Consider the following schema:
CREATE TYPE emp_type ( eno NUMBER, ename CHAR(31), eaddr addr_t); CREATE TABLE emp OF emp_t;
and the following two queries:
SELECT VALUE(emp) FROM emp; SELECT eno, ename FROM emp;
For either query, Oracle checks the user's SELECT privilege for the emp table. For the first query, the user needs to obtain the emp_type type information to interpret the data. When the query accesses the emp_type type, Oracle checks the user's EXECUTE privilege.
Execution of the second query, however, does not involve named types, so Oracle does not check type privileges.
Additionally, using the schema from the previous section, user3 can perform the following queries:
SELECT tab1.col1.attr2 FROM user2.tab1 tab1; SELECT attr4.attr3.attr2 FROM tab3;
Note that in both SELECT statements, user3 does not have explicit privileges on the underlying types, but the statement succeeds because the type and table owners have the necessary privileges with the GRANT OPTION.
Oracle checks privileges on the following events, and returns an error if the client does not have the privilege for the action:
REF value causes Oracle to check SELECT privilege on the containing object table.UPDATE privilege on the destination object table.INSERT privilege on the destination object table.DELETE privilege on the destination table.EXECUTE privilege on the object.Modifying an object's attributes in a client 3GL application causes Oracle to update the entire object. Hence, the user needs UPDATE privilege on the object table. UPDATE privilege on only certain columns of the object table is not sufficient, even if the application only modifies attributes corresponding to those columns. Therefore, Oracle does not support column level privileges for object tables.
As with stored objects such as procedures and tables, types being referenced by other objects are called dependencies. There are some special issues for types depended upon by tables. Because a table contains data that relies on the type definition for access, any change to the type causes all stored data to become inaccessible. Changes that can cause this effect are when necessary privileges required by the type are revoked or the type or dependent types are dropped. If either of these actions occur, then the table becomes invalid and cannot be accessed.
A table that is invalid because of missing privileges can automatically become valid and accessible if the required privileges are granted again. A table that is invalid because a dependent type has been dropped can never be accessed again, and the only permissible action is to drop the table.
Because of the severe effects which revoking a privilege on a type or dropping a type can cause, the SQL statements REVOKE and DROP TYPE by default implement a restrict semantics. This means that if the named type in either statement has table or type dependents, then an error is received and the statement aborts. However, if the FORCE clause for either statement is used, the statement always succeeds, and if there are depended-upon tables, they are invalidated.
| See Also:
Oracle Database Reference for details about using the |
Managing and controlling privileges is made easier by using roles, which are named groups of related privileges that you grant, as a group, to users or other roles. Within a database, each role name must be unique, different from all usernames and all other role names. Unlike schema objects, roles are not contained in any schema. Therefore, a user who creates a role can be dropped with no effect on the role.
Roles are designed to ease the administration of end-user system and schema object privileges, and are often maintained in Oracle Internet Directory. However, roles are not meant to be used by application developers, because the privileges to access schema objects within stored programmatic constructs need to be granted directly.
The effective management of roles is discussed in the following subsections:
These following properties of roles enable easier privilege management within a database:
Database administrators often create roles for a database application. The DBA grants a secure application role all privileges necessary to run the application. The DBA then grants the secure application role to other roles or users. An application can have several different roles, each granted a different set of privileges that allow for more or less data access while using the application.
The DBA can create a role with a password to prevent unauthorized use of the privileges granted to the role. Typically, an application is designed so that when it starts, it enables the proper role. As a result, an application user does not need to know the password for an application's role.
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In general, you create a role to serve one of two purposes:
Figure 5-1 and the sections that follow describe the two uses of roles.
Text description of the illustration cncpt082.gif
You grant an application role all privileges necessary to run a given database application. Then, you grant the secure application role to other roles or to specific users. An application can have several different roles, with each role assigned a different set of privileges that allow for more or less data access while using the application.
You create a user role for a group of database users with common privilege requirements. You manage user privileges by granting secure application roles and privileges to the user role and then granting the user role to appropriate users.
System or schema object privileges can be granted to a role, and any role can be granted to any database user or to another role (but not to itself). However, a role cannot be granted circularly, that is, a role X cannot be granted to role Y if role Y has previously been granted to role X.
To provide selective availability of privileges, Oracle allows database applications and users to enable and disable roles. Each role granted to a user is, at any given time, either enabled or disabled. A user's security domain includes the privileges of all roles currently enabled for the user and excludes the privileges of any roles currently disabled for the user.
A role granted to a role is called an indirectly granted role. It can be explicitly enabled or disabled for a user. However, whenever you enable a role that contains other roles, you implicitly enable all indirectly granted roles of the directly granted role.
You grant roles to (or revoke roles from) users or other roles by using either of the following methods:
Privileges are granted to and revoked from roles using the same options. Roles can also be granted to and revoked from users using the operating system that executes Oracle, or through network services.
| See Also:
For more information about
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Any user with the GRANT ANY ROLE system privilege can grant or revoke any role except a global role to or from other users or roles of the database. You should grant this system privilege conservatively because it is very powerful.
Any user granted a role with the ADMIN OPTION can grant or revoke that role to or from other users or roles of the database. This option allows administrative powers for roles on a selective basis.
| See Also:
Oracle Database Administrator's Guide for information about global roles |
Each role and user has its own unique security domain. A role's security domain includes the privileges granted to the role plus those privileges granted to any roles that are granted to the role.
A user's security domain includes privileges on all schema objects in the corresponding schema, the privileges granted to the user, and the privileges of roles granted to the user that are currently enabled. (A role can be simultaneously enabled for one user and disabled for another.) A user's security domain also includes the privileges and roles granted to the user group PUBLIC.
The use of roles in a PL/SQL block depends on whether it is an anonymous block or a named block (stored procedure, function, or trigger), and whether it executes with definer's rights or invoker's rights.
All roles are disabled in any named PL/SQL block (stored procedure, function, or trigger) that executes with definer's rights. Roles are not used for privilege checking and you cannot set roles within a definer's rights procedure.
The SESSION_ROLES view shows all roles that are currently enabled. If a named PL/SQL block that executes with definer's rights queries SESSION_ROLES, the query does not return any rows.
Named PL/SQL blocks that execute with invoker's rights and anonymous PL/SQL blocks are executed based on privileges granted through enabled roles. Current roles are used for privilege checking within an invoker's rights PL/SQL block, and you can use dynamic SQL to set a role in the session.
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A user requires one or more privileges to successfully execute a data definition language (DDL) statement, depending on the statement. For example, to create a table, the user must have the CREATE TABLE or CREATE ANY TABLE system privilege. To create a view of another user's table, the creator requires the CREATE VIEW or CREATE ANY VIEW system privilege and either the SELECT object privilege for the table or the SELECT ANY TABLE system privilege.
Oracle avoids the dependencies on privileges received by way of roles by restricting the use of specific privileges in certain DDL statements. The following rules outline these privilege restrictions concerning DDL statements:
CREATE TABLE, CREATE VIEW and CREATE PROCEDURE privileges.ALTER and INDEX privileges for a table.Exception: The REFERENCES object privilege for a table cannot be used to define a table's foreign key if the privilege is received through a role.
The following example further clarifies the permitted and restricted uses of privileges received through roles:
Assume that a user is:
CREATE VIEW system privilegeSELECT object privilege for the employees table, but the user is indirectly granted the SELECT object privilege for the employees tableSELECT object privilege for the departments tableGiven these directly and indirectly granted privileges:
SELECT statements on both the employees and departments tables.CREATE VIEW and SELECT privilege for the employees table through a role, the user cannot create a usable view on the employees table, because the SELECT object privilege for the employees table was granted through a role. Any views created will produce errors when accessed.departments table, because the user has the CREATE VIEW privilege through a role and the SELECT privilege for the departments table directly.The following roles are defined automatically for Oracle databases:
These roles are provided for backward compatibility to earlier versions of Oracle and can be modified in the same manner as any other role in an Oracle database.
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Note: Each installation should create its own roles and assign only those privileges that are needed. For example, it is unwise to grant CONNECT if all that is needed is CREATE SESSION, since CONNECT includes several additional privileges: see Table 10-1, " Predefined Roles", in Chapter 10, "Administering User Privileges, Roles, and Profiles". Creating its own roles gives an organization detailed control of the privileges it assigns, and protects it in case Oracle were to change or remove roles that it defines. |
In some environments, you can administer database security using the operating system. The operating system can be used to manage the granting (and revoking) of database roles and to manage their password authentication. This capability is not available on all operating systems.
| See Also:
Your operating system specific Oracle documentation for details on managing roles through the operating system |
When you use roles in a distributed database environment, you must ensure that all needed roles are set as the default roles for a distributed (remote) session. Those roles cannot be enabled when you connect to a remote database from within a local database session. For example, you cannot execute a remote procedure that attempts to enable a role at the remote site.
Oracle provides secure application roles, which are roles that can only be enabled by authorized PL/SQL packages. This mechanism restricts the enabling of such roles to the invoking application.
Security is strengthened when passwords are not embedded in application source code or stored in a table. Instead, a secure application role can be created, specifying which PL/SQL package is authorized to enable the role. Package identity is used to determine whether privileges are sufficient to enable the roles. Before enabling the role, the application can perform authentication and customized authorization, such as checking whether the user has connected through a proxy.
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Note: Because of the restriction that users cannot change security domain inside definer's right procedures, secure application roles can only be enabled inside invoker's right procedures. |
Secure application roles are created by using the statement CREATE ROLE ... IDENTIFIED USING. Here is an example:
CREATE ROLE admin_role IDENTIFIED USING hr.admin;
This statement indicates the following:
admin_role to be created is a secure application role.hr.admin.You must have the system privilege CREATE ROLE to execute this statement.
When such a role is assigned to a user, it becomes a default role for that user, automatically enabled at login without resorting to the package. A user with a default role does not have to be authenticated in any way to use the role; for example, the password for the role is not requested or required.
To restrict the role solely to the use specified by the IDENTIFIED USING clause, you can take either of the following actions:
Roles that are enabled inside an Invoker's Right procedure remain in effect even after the procedure exits. Therefore, you can have a dedicated procedure that deals with enabling the role for the rest of the session to use.
You can set limits on the amount of various system resources available to each user as part of that user's security domain. By doing so, you can prevent the uncontrolled consumption of valuable system resources such as CPU time.
This resource limit feature is very useful in large, multiuser systems, where system resources are very expensive. Excessive consumption of these resources by one or more users can detrimentally affect the other users of the database. In single-user or small-scale multiuser database systems, the system resource feature is not as important, because users' consumption of system resources is less likely to have detrimental impact.
You manage a user's resource limits by means of the Database Resource Manager. You can set password management preferences using profiles, either set individually or using a default profile for many users. Each Oracle database can have an unlimited number of profiles. Oracle allows the security administrator to enable or disable the enforcement of profile resource limits universally.
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Setting resource limits causes a slight performance degradation when users create sessions, because Oracle loads all resource limit data for each user upon each connection to the database.
| See Also:
Oracle Database Administrator's Guide for information about security administrators. |
Resource limits and profiles are discussed in the following sections:
Oracle can limit the use of several types of system resources, including CPU time and logical reads. In general, you can control each of these resources at the session level, the call level, or both, as discussed in the following subsections:
Each time a user connects to a database, a session is created. Each session consumes CPU time and memory on the computer that executes Oracle. You can set several resource limits at the session level.
If a user exceeds a session-level resource limit, Oracle terminates (rolls back) the current statement and returns a message indicating the session limit has been reached. At this point, all previous statements in the current transaction are intact, and the only operations the user can perform are COMMIT, ROLLBACK, or disconnect (in this case, the current transaction is committed). All other operations produce an error. Even after the transaction is committed or rolled back, the user can accomplish no more work during the current session.
Each time a SQL statement is executed, several steps are taken to process the statement. During this processing, several calls are made to the database as part of the different execution phases. To prevent any one call from using the system excessively, Oracle lets you set several resource limits at the call level.
If a user exceeds a call-level resource limit, Oracle halts the processing of the statement, rolls back the statement, and returns an error. However, all previous statements of the current transaction remain intact, and the user's session remains connected.
When SQL statements and other types of calls are made to Oracle, an amount of CPU time is necessary to process the call. Average calls require a small amount of CPU time. However, a SQL statement involving a large amount of data or a runaway query can potentially consume a large amount of CPU time, reducing CPU time available for other processing.
To prevent uncontrolled use of CPU time, you can limit the CPU time for each call and the total amount of CPU time used for Oracle calls during a session. The limits are set and measured in CPU one-hundredth seconds (0.01 seconds) used by a call or a session.
Input/output (I/O) is one of the most expensive operations in a database system. SQL statements that are I/O intensive can monopolize memory and disk use and cause other database operations to compete for these resources.
To prevent single sources of excessive I/O, Oracle let you limit the logical data block reads for each call and for each session. Logical data block reads include data block reads from both memory and disk. The limits are set and measured in number of block reads performed by a call or during a session.
Oracle also provides for limiting several other resources at the session level:
In general, the word "profile" refers to a collection of attributes that apply to a user, enabling a single point of reference for any of multiple users that share the those exact attributes. User profiles in Oracle Internet Directory contain a wide range of attributes pertinent to directory usage and authentication for each user. Similarly, profiles in Oracle Label Security contain attributes useful in label security user administration and operations management. Profile attributes can include restrictions on system resources, but for that purpose the Database Resource Manager is preferred.
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Before creating profiles and setting the resource limits associated with them, you should determine appropriate values for each resource limit. You can base these values on the type of operations a typical user performs. For example, if one class of user does not normally perform a high number of logical data block reads, then set the LOGICAL_READS_PER_SESSION and LOGICAL_READS_PER_CALL limits conservatively.
Usually, the best way to determine the appropriate resource limit values for a given user profile is to gather historical information about each type of resource usage. For example, the database or security administrator can use the AUDIT SESSION clause to gather information about the limits CONNECT_TIME, LOGICAL_READS_PER_SESSION, and LOGICAL_READS_PER_CALL.
You can gather statistics for other limits using the Monitor feature of Oracle Enterprise Manager (or SQL*Plus), specifically the Statistics monitor.
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