Application context can be used with fine-grained access control as part of Virtual Private Database (VPD) or by itself. Used alone, it enables application developers to define, set, and access application attributes by serving as a data cache. Such usage removes the repeated overhead of querying the database each time access to application attributes is needed.
This chapter discusses how to implement application context and fine-grained access control using the following sections:
Application context can be useful for the following purposes:
Enforcing fine-grained access control
Preserving user identity across multitier environments
Serving as a secure data cache for attributes needed by an application for fine-grained auditing or for use in PL/SQL conditional statements or loops
This cache saves the repeated overhead of querying the database each time such attributes are needed.
Serving as a holding area for attribute-value pairs that an application can define, modify, and access
Three types of application context are defined, differentiated by where the context data is stored and by how updates can be done:
Secure session-based application contexts, for which data is stored in the database user session (UGA) in a namespace specified by an SQL command (CREATE CONTEXT
).
Example: CREATE CONTEXT hr USING scott.package1
;
Data in this secure, session-private data cache can only be set by the PL/SQL package in that command. In this example, only scott.package1
can alter data in the hr
namespace.
Namespaces created in this way are maintained using the existing PL/SQL packages available in the DBMS_SESSION
package.
Session-based application contexts can be initialized either externally or globally, and either method stores the context information in the user session.
External initialization can come from an OCI interface, a job queue process, or a connected user database link.
Global initialization uses attributes and values from a centralized location, such as an LDAP directory.
See Also:
Note:
Theinit.ora
parameter _session_context_size
limits the total number of (namespace, attribute) pairs used by all application contexts in the user session UGA. This limit includes the client namespace CLIENTCONTEXT
, but excludes globally accessed context, which uses memory from the shared pool.
Users can change the value for _session_context_size
, the default value for which is 10,000.
A new attribute, SESSION_CONTEXT_SIZE
, which stores the number of sets of context information that are currently in the user session, is accessible as SELECT SYS_CONTEXT
('userenv', 'session_context_size') from dual;
The client session-based application context, using only the CLIENTCONTEXT
namespace, updatable by any OCI client or by the existing DBMS_SESSION API
for application context. No privilege or package security check is done.
The CLIENTCONTEXT
namespace enables a single application transaction to both change the user context information and use the same user session handle to service the new user request.
An OCI client uses the OCIAppCtx
API to set variable length data for the namespace, on the OCISessionHandle
. The OCI network single round-trip transport sends all the information to the server in one round trip. On the server side, the application context information can be queried using the SYS_CONTEXT
SQL function on the namespace.
A JDBC client uses the oracle.jdbc.internal.OracleConnection
API to achieve the same purposes.
See Also:
Managing Scalable Platforms in Oracle Call Interface Programmer's Guide for details regarding the OCIAppCtx API
Any user can set, clear, or collect the information in the CLIENTCONTEXT
namespace, because it is not protected by package-based security.
Nonsession-based (global) application contexts, for which data is stored in the shared area (SGA).
See Also:
How to Use Global Application ContextTable 15-1 summarizes the different types of application contexts.
Table 15-1 Types of Application Contexts
Application Context Type | Stored in UGA | Stored in SGA | Supports Connected User Database Links | Supports Centralized Storage of Users' Application Context | Supports Sessionless Multitier Applications |
---|---|---|---|---|---|
Application Context |
X |
-- |
-- |
-- |
-- |
Application Context Initialized Externally |
X |
-- |
X |
-- |
-- |
Application Context Initialized Globally |
X |
-- |
-- |
X |
-- |
CLIENTCONTEXT |
X |
-- |
X |
-- |
X |
Global Application Context |
-- |
X |
-- |
-- |
X |
See Also:
"Introduction to Application Context" for conceptual information about session-based application context
"Introduction to Global Application Context" for conceptual information about nonsession-based application context
"Using the CLIENT_IDENTIFIER Attribute to Preserve User Identity" for a discussion about using the CLIENT_IDENTIFIER
attribute of the predefined USERENV
application context
"Fine-Grained Auditing" for information about using application context with fine-grained auditing
The following sections explain secure and client session-based application context:
To use secure session-based application context, you must perform the following tasks:
Task 1: Create a PL/SQL Package that Sets the Secure Context for Your Application
Task 2: Create a Unique Secure Context and Associate It with the PL/SQL Package
Task 3: Set the Secure Context Before the User Retrieves Data
Begin by creating a PL/SQL package with functions that set the secure context for your application. This section presents the syntax and behavior of the SYS_CONTEXT
SQL function, followed by an example for creating the PL/SQL package.
Note:
A login trigger can be used because the user context (information such asEMPNO
, GROUP
, MANAGER
) should be set before the user accesses any data.The syntax for this function is:
SYS_CONTEXT ('namespace', 'attribute', [length])
This function returns the value of attribute
as defined in the package currently associated with the context namespace. It is evaluated once for each statement execution, and is treated like a constant during type checking for optimization. You can use the predefined namespace USERENV
to access primitive contexts such as userid and Globalization Support parameters.
See Also:
"Providing Access to Predefined Attributes Through the USERENV Namespace" for information about the USERENV
application context namespace and a complete list of its predefined attributes
Oracle Database SQL Reference for details about USERENV
predefined attributes
The following example creates the package App_security_context
.
CREATE OR REPLACE PACKAGE App_security_context IS PROCEDURE Set_empno; END; CREATE OR REPLACE PACKAGE BODY App_security_context IS PROCEDURE Set_empno IS Emp_id NUMBER; BEGIN SELECT Empno INTO Emp_id FROM Emp WHERE Ename = SYS_CONTEXT('USERENV', 'SESSION_USER'); DBMS_SESSION.SET_CONTEXT('app_context', 'empno', Emp_id); END; END;
See Also:
PL/SQL Packages and Types Reference for information about theDBMS_SESSION.SET_CONTEXT
procedure.Note:
This feature is applicable whenCOMPATIBLE
is set to either 8.0 or 8.1.During a session in which you expect a change in policy between executions of a given query, the query must use dynamic SQL. You must use dynamic SQL because static SQL and dynamic SQL parse statements differently.
Static SQL statements are parsed at compile time. They are not reparsed at execution for performance reasons.
Dynamic SQL statements are parsed every time they are executed.
Consider a situation in which policy A is in force when you compile a SQL statement, and then you switch to policy B and run the statement. With static SQL, policy A remains in force. The statement is parsed at compile time and not reparsed upon execution. With dynamic SQL, the statement is parsed upon execution, and so the switch to policy B takes effect.
For example, consider the following policy:
EMPLOYEE_NAME = SYS_CONTEXT ('USERENV', 'SESSION_USER')
The policy EMPLOYEE_NAME
matches the database user name. It is represented in the form of a SQL predicate: the predicate is basically a policy. If the predicate changes, then the statement must be reparsed in order to produce the correct result.
See Also:
"Automatic Reparse"If SYS_CONTEXT
is used inside a SQL function that is embedded in a parallel query, then the function picks up the application context.
Consider a user-defined function within a SQL statement, which sets the user ID to 5:
CREATE FUNCTION proc1 AS RETURN NUMBER; BEGIN IF SYS_CONTEXT ('hr', 'id') = 5 THEN RETURN 1; ELSE RETURN 2; END END;
Now consider the statement:
SELECT * FROM EMP WHERE proc1( ) = 1;
When this statement is run as a parallel query, the user session, which contains the application context information, is propagated to the parallel execution servers (query slave processes).
Session-based local application context can be accessed by SQL statements within a user session by using the SYS_CONTEXT
SQL function. When these SQL statements involve database links, then the SYS_CONTEXT
SQL function is executed at the database link's initiating site and captures the context information there (at the initiating site).
If remote PL/SQL procedure calls are executed over a database link, then any SYS_CONTEXT
function inside such a procedure is executed at the database link's destination site. In this case, only externally initialized application contexts are available at the database link destination site. For security reasons, only the externally initialized application context information is propagated to the destination site from the initiating database link site.
To perform this task, use the CREATE
CONTEXT
statement. Each context must have a unique attribute and belong to a namespace. That is, context names must be unique within the database, not just within a schema. Contexts are always owned by the SYS
schema.
For example:
CREATE CONTEXT order_entry USING App_security_context;
Here, order_entry
is the context namespace and App_security_context
is the trusted package that can set attributes in the context namespace.
After you have created the context, you can set or reset the context attributes by using the DBMS_SESSION.SET_CONTEXT
package. The values of the attributes you set remain either until you reset them or until the user ends the session.
You can only set the context attributes inside the trusted procedure you named in the CREATE
CONTEXT
statement. This prevents a malicious user from changing context attributes without proper attribute validation.
Alternatively, you can use the Oracle Policy Manager graphical user interface (GUI) to create a context and associate it with a PL/SQL package. Oracle Policy Manager, accessed from Oracle Enterprise Manager, enables you to apply policies to database objects and create application contexts. It also can be used to create and manage Oracle Label Security policies.
Always use an event trigger on login to pull session information into the context. This sets the security-limiting attributes of the user for the database to evaluate, and thus enables it to make the appropriate security decisions.
Other considerations come into play if you have a changing set of books, or if positions change constantly. In these cases, the new attribute values may not be picked up right away, and you must force a cursor reparse to pick them up.
This section provides the following examples that use secure session-based application context within a fine-grained access control function.
This example uses secure application context to implement a policy, in which customers can see only their own orders, and builds the application using the following steps:
Step 1: Create a PL/SQL Package To Set the Secure Context for the Application
Step 3: Access the Secure Application Context Inside the Package
The procedure in this example assumes a one-to-one relationship between users and customers. It finds the user customer number (Cust_num
) and caches the customer number in the application context. You can later refer to the cust_num
attribute of the order entry context (oe_ctx
) inside the security policy function.
Note that you could use a login trigger to set the initial context.
Create the package as follows:
Note:
You may need to set up the following data structures for the following examples to work:CREATE TABLE apps.customers (cust_no NUMBER(4), cust_name VARCHAR2(20)); CREATE TABLE scott.orders_tab (order_no NUMBER(4));
CREATE OR REPLACE PACKAGE apps.oe_ctx AS
PROCEDURE set_cust_num;
END;
CREATE OR REPLACE PACKAGE BODY apps.oe_ctx AS
PROCEDURE set_cust_num IS
custnum NUMBER;
BEGIN
SELECT cust_no INTO custnum FROM customers WHERE cust_name =
SYS_CONTEXT('USERENV', 'SESSION_USER');
/* SET cust_num attribute in 'order_entry' context */
DBMS_SESSION.SET_CONTEXT('order_entry', 'cust_num', custnum);
DBMS_SESSION.SET_CONTEXT('order_entry', 'cust_num', custnum);
END set_cust_num;
END;
Note:
This example does not treat error handling.You can access predefined attributes, such as session user, by using SYS_CONTEXT('USERENV',
session_primitive
)
.
For more information, see Table 14-1, "Key to Predefined Attributes in USERENV Namespace" and Oracle Database SQL Reference.
Create an application context by entering:
CREATE CONTEXT Order_entry USING apps.oe_ctx;
Alternatively, you can use Oracle Policy Manager to create an application context.
Access the secure application context inside the package that implements the security policy on the database object.
Note:
You may need to set up the following data structures for certain examples to work:CREATE OR REPLACE PACKAGE Oe_security AS FUNCTION Custnum_sec (D1 VARCHAR2, D2 VARCHAR2) RETURN VARCHAR2; END;
The package body appends a dynamic predicate to SELECT
statements on the ORDERS_TAB
table. This predicate limits the orders returned to those associated with the customer number of the user by accessing the cust_num
context attribute, instead of using a subquery to the customers table.
CREATE OR REPLACE PACKAGE BODY Oe_security AS
/* limits select statements based on customer number: */
FUNCTION Custnum_sec (D1 VARCHAR2, D2 VARCHAR2) RETURN VARCHAR2
IS
D_predicate VARCHAR2 (2000);
BEGIN
D_predicate := 'cust_no = SYS_CONTEXT(''order_entry'', ''cust_num'')';
RETURN D_predicate;
END Custnum_sec;
END Oe_security;
Note:
You may need to set up the following data structures for certain examples to work:CONNECT sys/xIcf1T9u AS sysdba; CREATE USER secusr IDENTIFIED BY secusr;
Create the policy as follows:
BEGIN DBMS_RLS.ADD_POLICY ('scott', 'orders_tab', 'oe_policy', 'secusr', 'oe_security.custnum_sec', 'select'); END;
This statement adds a policy named OE_POLICY
to the ORDERS_TAB
table for viewing in the SCOTT
schema. The SECUSR
.OE_SECURITY.CUSTNUM_SEC
function implements the policy, is stored in the SECUSR
schema, and applies to SELECT
statements only.
Now, any SELECT
statement by a customer on the ORDERS_TAB
table automatically returns only the orders of that particular customer. In other words, the dynamic predicate modifies the statement from:
SELECT * FROM Orders_tab;
to the following:
SELECT * FROM Orders_tab
WHERE Custno = SYS_CONTEXT('order_entry','cust_num');
Note the following with regard to this example:
In reality, you might have several predicates based on a user's position. For example, a sales representative would be able to see records only for his customers, and an order entry clerk would be able to see any customer order. You could expand the custnum_sec
function to return different predicates based on the user position context value.
The use of application context in a fine-grained access control package effectively gives you a bind variable in a parsed statement. For example:
SELECT * FROM Orders_tab WHERE Custno = SYS_CONTEXT('order_entry', 'cust_num')
This is fully parsed and optimized, but the evaluation of the CUST_NUM
attribute value of the user for the ORDER_ENTRY
context takes place at execution. This means that you get the benefit of an optimized statement that executes differently for each user who executes the statement.
You can set context attributes based on data from a database table or tables, or from a directory server using LDAP (Lightweight Directory Access Protocol).
Compare and contrast this example, which uses an application context within the dynamically generated predicate, with "How Fine-Grained Access Control Works", which uses a subquery in the predicate.
This example uses secure application context to control user access with a Human Resources application. Each task that you need to perform is described more fully in the sections that follow:
Step 2: Create the Secure Context and Associate It with the Package
Step 3: Create the Initialization Script for the Application
In this example, assume that the application context for the Human Resources application is assigned to the HR_CTX
namespace.
Note:
You may need to set up the following data structures for certain examples to work:DROP USER apps CASCADE; CREATE USER apps IDENTIFIED BY welcome1; CREATE OR REPLACE PACKAGE apps.hr_sec_ctx IS PROCEDURE set_resp_id (respid NUMBER); PROCEDURE set_org_id (orgid NUMBER); /* PROCEDURE validate_respid (respid NUMBER); */ /* PROCEDURE validate_org_id (orgid NUMBER); */ END hr_sec_ctx;
Create a PL/SQL package with a number of functions that set the secure context for the application. APPS
is the schema that owns this package.
CREATE OR REPLACE PACKAGE BODY apps.hr_sec_ctx IS /* function to set responsibility id */ PROCEDURE set_resp_id (respid NUMBER) IS BEGIN /* validate respid based on primitive and other context */ /* validate_respid (respid); */ /* set resp_id attribute under namespace 'hr_ctx'*/ DBMS_SESSION.SET_CONTEXT('hr_ctx', 'resp_id', respid); END set_resp_id; /* function to set organization id */ PROCEDURE set_org_id (orgid NUMBER) IS BEGIN /* validate organization ID */ /* validate_org_id(orgid); /* /* set org_id attribute under namespace 'hr_ctx' */ DBMS_SESSION.SET_CONTEXT('hr_ctx', 'org_id', orgid); END set_org_id; /* more functions to set other attributes for the HR application */ END hr_sec_ctx;
For example:
CREATE CONTEXT Hr_ctx USING apps.hr_sec_ctx;
Suppose that the execute privilege on the HR_SEC_CTX
package has been granted to the schema running the application. Part of the script will make calls to set various attributes of the HR_CTX
context. Here, we do not show how the context is determined. Normally, it is based on the primitive context or other derived context.
APPS.HR_SEC_CTX.SET_RESP_ID(1); APPS.HR_SEC_CTX.SET_ORG_ID(101);
The SYS_CONTEXT
function can be used for data access control based on this application context. For example, the base table HR_ORGANIZATION_UNIT
can be secured by a view that restricts access to rows based on the attribute ORG_ID
:
CREATE VIEW Hr_organization_secv AS SELECT * FROM hr_organization_unit WHERE Organization_id = SYS_CONTEXT('hr_ctx','org_id');
Note:
You may need to set up the following data structures for certain examples to work:CREATE TABLE hr_organization_unit (organization_id NUMBER);
This example illustrates use of the following security features in Oracle Database:
Application context (session-based)
Fine-grained access control
Encapsulation of privileges in stored procedures
In this example, we associate a security policy with the table called DIRECTORY
, which has the following columns:
Column | Description |
---|---|
EMPNO |
Identification number for each employee |
MGRID |
Employee identification number for the manager of each employee |
RANK |
Position of the employee in the corporate hierarchy |
Note:
You may need to set up the following data structures for certain examples to work:CREATE TABLE Payroll( Srate NUMBER, Orate NUMBER, Acctno NUMBER, Empno NUMBER, Name VARCHAR2(20)); CREATE TABLE Directory_u( Empno NUMBER, Mgrno NUMBER, Rank NUMBER); CREATE SEQUENCE Empno_seq; CREATE SEQUENCE Rank_seq;
The security policy associated with this table has two elements:
All users can find the MGRID
for a specific EMPNO
. To implement this, we create a definer's right package in the human resources schema (HR
) to perform SELECT
on the table.
Managers can update only those positions in the corporate hierarchy that are their direct subordinates. To do this, they must use only the designated application. You can implement this as follows:
Define fine-grained access control policies on the table based on EMPNO
and application context.
Set EMPNO
by using a login trigger.
Set the application context by using the designated package for processing the updates (event triggers and application context).
Note:
In this example, we grantUPDATE
privileges on the table to the PUBLIC
role, because fine-grained access control prevents an unauthorized user from wrongly modifying a given row.The following code implements this example as described:
CONNECT system/yJdg2U1v AS sysdba GRANT CONNECT,RESOURCE,UNLIMITED TABLESPACE,CREATE ANY CONTEXT, CREATE PROCEDURE, CREATE ANY TRIGGER TO HR IDENTIFIED BY HR; CONNECT hr/hr; CREATE TABLE Directory (Empno NUMBER(4) NOT NULL, Mgrno NUMBER(4) NOT NULL, Rank NUMBER(7,2) NOT NULL); CREATE TABLE Payroll (Empno NUMBER(4) NOT NULL, Name VARCHAR(30) NOT NULL ); /* seed the tables with a couple of managers: */ INSERT INTO Directory VALUES (1, 1, 1.0); INSERT INTO Payroll VALUES (1, 'KING'); INSERT INTO Directory VALUES (2, 1, 5); INSERT INTO Payroll VALUES (2, 'CLARK'); /* Create the sequence number for EMPNO: */ CREATE SEQUENCE Empno_seq START WITH 5; /* Create the sequence number for RANK: */ CREATE SEQUENCE Rank_seq START WITH 100; CREATE OR REPLACE CONTEXT Hr_app USING Hr.Hr0_pck; CREATE OR REPLACE CONTEXT Hr_sec USING Hr.Hr1_pck; CREATE OR REPLACE PACKAGE Hr0_pck IS PROCEDURE adjustrankby1(Empno NUMBER); END; CREATE OR REPLACE PACKAGE BODY Hr0_pck IS /* raise the rank of the empno by 1: */ PROCEDURE Adjustrankby1(Empno NUMBER) IS Stmt VARCHAR2(100); BEGIN /*Set context to indicate application state */ DBMS_SESSION.SET_CONTEXT('hr_app','adjstate',1); /* Now we can issue DML statement: */ Stmt := 'UPDATE Directory d SET Rank = Rank + 1 WHERE d.Empno = ' || Empno; EXECUTE IMMEDIATE STMT; /* Re-set application state: */ DBMS_SESSION.SET_CONTEXT('hr_app','adjstate',0); END; END; CREATE OR REPLACE PACKAGE hr1_pck IS PROCEDURE setid; END; / /* Based on userid, find EMPNO, and set it in application context */ CREATE or REPLACE PACKAGE BODY Hr1_pck IS PROCEDURE setid IS id NUMBER; BEGIN SELECT Empno INTO id FROM Payroll WHERE Name = SYS_CONTEXT('userenv','session_user') ; DBMS_SESSION.SET_CONTEXT('hr_sec','empno',id); DBMS_SESSION.SET_CONTEXT('hr_sec','appid',id); EXCEPTION /* For purposes of demonstration insert into payroll table / so that user can continue on and run example. */ WHEN NO_DATA_FOUND THEN INSERT INTO Payroll (Empno, Name) VALUES (Empno_seq.NEXTVAL, SYS_CONTEXT('userenv','session_user')); INSERT INTO Directory (Empno, Mgrno, Rank) VALUES (Empno_seq.CURRVAL, 2, Rank_seq.NEXTVAL); SELECT Empno INTO id FROM Payroll WHERE Name = sys_context('userenv','session_user') ; DBMS_SESSION.SET_CONTEXT('hr_sec','empno',id); DBMS_SESSION.SET_CONTEXT('hr_sec','appid',id); WHEN OTHERS THEN NULL; /* If this is to be fired by using a "logon" trigger, / you need to handle exceptions if you want the user to continue / logging into the database. */ END; END; GRANT EXECUTE ON Hr1_pck TO public; CONNECT system/yJdg2U1v AS sysdba CREATE OR REPLACE TRIGGER Databasetrigger AFTER LOGON ON DATABASE BEGIN hr.Hr1_pck.Setid; END; /* Creates the package for finding the MGRID for a particular EMPNO using definer's right (encapsulated privileges). Note that users are granted EXECUTE privileges only on this package, and not on the table (DIRECTORY) it is querying. */ CONNECT hr/hr CREATE OR REPLACE PACKAGE hr2_pck IS FUNCTION Findmgr(Empno NUMBER) RETURN NUMBER; END; CREATE OR REPLACE PACKAGE BODY hr2_pck IS /* insert a new employee record: */ FUNCTION findmgr(empno number) RETURN NUMBER IS Mgrid NUMBER; BEGIN SELECT mgrno INTO mgrid FROM directory WHERE mgrid = empno; RETURN mgrid; END; END; CREATE OR REPLACE FUNCTION secure_updates(ns varchar2,na varchar2) RETURN VARCHAR2 IS Results VARCHAR2(100); BEGIN /* Only allow updates when designated application has set the session state to indicate we are inside it. */ IF (sys_context('hr_app','adjstate') = 1) THEN results := 'mgrno = SYS_CONTEXT("hr_sec","empno")'; ELSE results := '1=2'; END IF; RETURN Results; END; /* Attaches fine-grained access policy to all update operations on hr.directory */ CONNECT system/yJdg2U1v AS sysdba; BEGIN DBMS_RLS.ADD_POLICY('hr','directory','secure_update','hr', 'secure_updates','update',TRUE,TRUE); END;
This feature lets you specify a special type of namespace that accepts initialization of attribute values from external resources and stores them in the local user session. Allowing secure application context to be initialized externally enhances performance and enables the automatic propagation of attributes from one session to another. Connected user database links are supported only by application contexts initialized from OCI-based external sources.
This section contains these topics:
Sometimes it is desirable to obtain default values from users. Initially, these default values may serve as hints or preferences, and then after validation become trusted contexts. Similarly, it may be more convenient for clients to initialize some default values, and then rely on a login event trigger or applications to validate the values.
For job queues, the job submission routine records the context being set at the time the job is submitted, and restores it when executing the batched job. To maintain the integrity of the context, job queues cannot bypass the designated PL/SQL package to set the context. Rather, externally initialized application context accepts initialization of context values from the job queue process.
Automatic propagation of context to a remote session may create security problems. Developers or administrators can effectively handle this type of context that takes default values from resources other than the designated PL/SQL procedure by using login triggers to reset the context when users log in.
In addition to using the designated trusted package, externally initialized secure application contexts can also accept initialization of attributes and values through external resources. Examples include an OCI interface, a job queue process, or a database link.
Externally initialized secure application context provides:
For remote sessions, automatic propagation of context values that are in the externally initialized secure context namespace
For job queues, restoration of context values that are in the externally initialized secure context namespace
For OCI interfaces, a mechanism to initialize context values that are in the externally initialized secure context namespace
Although this type of namespace can be initialized by any client program using OCI, there are login event triggers that can verify the values. It is up to the application to interpret and trust the values of the attributes.
Middle-tier servers can actually initialize secure context values on behalf of database users. Context attributes are propagated for the remote session at initialization time, and the remote database accepts the values if the namespace is externally initialized.
This feature uses a centralized location to store the secure application context of the user, enabling applications to set up a user context during initialization based upon user identity. In particular, it supports Oracle Label Security labels and privileges. This feature makes it much easier for the administrator to manage contexts for large numbers of users and databases.
For example, many organizations want to manage user information centrally, in an LDAP-based directory. Enterprise User Security, a feature of Oracle Advanced Security, supports centralized user and authorization management in Oracle Internet Directory. However, there may be additional attributes an application wishes to retrieve from LDAP to use for VPD enforcement, such as the user title, organization, or physical location.
This section contains these topics:
Secure session-based application context initialized globally uses the Lightweight Directory Access Protocol (LDAP), a standard, extensible, and efficient directory access protocol. The LDAP directory stores a list of users to which this application is assigned. An Oracle database server uses the directory service, typically Oracle Internet Directory, for authentication and authorization of enterprise users.
Note:
Enterprise User Security requires Oracle Advanced Security.
Third-party directories such as Microsoft Active Directory and Sun Microsystems iPlanet can also be used as the directory service.
The orclDBApplicationContext
LDAP object (a subclass of groupOfUniqueNames
) stores the application context values in the directory. The location of the application context object is described in Figure 15-1, which is based on the Human Resources example.
An internal C function is required to retrieve the orclDBApplicationContext
value, which returns a list of application context values to the RDBMS.
Note:
In this example, HR is the namespace, Title and Project are the attributes, and Manager and Promotion are the values.Figure 15-1 Location of Application Context in LDAP Directory Information Tree
The administrator configures Enterprise User Security, a feature of Oracle Advanced Security. Then, the administrator sets up the secure application context values for the user in the database and the directory.
When a global user (enterprise user) connects to the database, the Oracle Advanced Security Enterprise User Security feature performs authentication to verify the identity of the user connecting to the database. After authentication, the global user roles and application context are retrieved from the directory. When the user logs on to the database, the global roles and initial application context are already set up.
See Also:
Oracle Database Advanced Security Administrator's Guide for a detailed discussion of Enterprise User Security and how to configure this featureThe initial application context for a user, such as department name and title, can be set up and stored in the LDAP directory. The values are retrieved during user login so that the context is set properly. In addition, any information related to the user is retrieved and stored in the SYS_USER_DEFAULTS
application context namespace. The following example shows how this is done.
Create a secure application context in the database.
CREATE CONTEXT HR USING hrapps.hr_manage_pkg INITIALIZED GLOBALLY;
Create and add new entries in the LDAP directory.
An example of the entries added to the LDAP directory follows. These entries create an attribute named Title
with attribute value Manager
for the application (namespace) HR
, and assign user names user1
and user2
.
dn: cn=OracleDBAppContext,cn=myDomain,cn=OracleDBSecurity,cn=Products,cn=OracleC ontext,ou=Americas,o=oracle,c=US changetype: add cn: OracleDBAppContext objectclass: top objectclass: orclContainer dn: cn=HR,cn=OracleDBAppContext,cn=myDomain,cn=OracleDBSecurity,cn=Products,cn=O racleContext,ou=Americas,o=oracle,c=US changetype: add cn: HR objectclass: top objectclass: orclContainer dn: cn=Title,cn=HR,cn=OracleDBAppContext,cn=myDomain,cn=OracleDBSecurity,cn=Prod ucts,cn=OracleContext,ou=Americas,o=oracle,c=US changetype: add cn: Title objectclass: top objectclass: orclContainer dn: cn=Manager,cn=Title,cn=HR,cn=OracleDBAppContext,cn=myDomain,cn=OracleDBSecurity,cn=Products,cn=OracleContext,ou=Americas,o=oracle,c=US cn: Manager objectclass: top objectclass: groupofuniquenames objectclass: orclDBApplicationContext uniquemember: CN=user1,OU=Americas,O=Oracle,L=Redwoodshores,ST=CA,C=US uniquemember: CN=user2,OU=Americas,O=Oracle,L=Redwoodshores,ST=CA,C=US
If an LDAP inetOrgPerson
object entry exists for the user, then the connection will also retrieve all the attributes from inetOrgPerson
and assign them to the namespace SYS_LDAP_USER_DEFAULT
. The following is an example of an inetOrgPerson
entry:
dn: cn=user1,ou=Americas,O=oracle,L=redwoodshores,ST=CA,C=US changetype: add objectClass: top objectClass: person objectClass: organizationalPerson objectClass: inetOrgPerson cn: user1 sn: One givenName: User initials: UO title: manager, product development uid: uone mail: uone@us.oracle.com telephoneNumber: +1 650 123 4567 employeeNumber: 00001 employeeType: full time
Connect to the database.
When user1
connects to a database that belongs to the myDomain
domain, user1
will have his Title
set to Manager
. Any information related to user1
will be retrieved from the LDAP directory. The value can be obtained using the following syntax:
SYS_CONTEXT('namespace','attribute name')
For example:
DECLARE tmpstr1 VARCHAR2(30); tmpstr2 VARCHAR2(30); BEGIN tmpstr1 = SYS_CONTEXT('HR','TITLE); tmpstr2 = SYS_CONTEXT('SYS_LDAP_USER_DEFAULT','telephoneNumber'); DBMS_OUTPUT.PUT_LINE('Title is ' || tmpstr1); DBMS_OUTPUT.PUT_LINE('Telephone Number is ' || tmpstr2); END;
The output of this example is:
Title is Manager Telephone Number is +1 650 123 4567
The OCIAppCtx
API enables you to use client session-based application context. You can set or clear individual values for attributes in the CLIENTCONTEXT
namespace, or clear all their values, by following the examples in the subsections that follow:
For OCI, use a command of the following form:
err = OCIAppCtxSet((void *) session_handle,(dvoid *)"CLIENTCONTEXT",(ub4) 13, (dvoid *)attribute_name, length_of_attribute_name (dvoid *)attribute_value, length_of_attribute_value, errhp, OCI_DEFAULT);
where session_handle
represents the OCISessionHandle
, attribute_name
could be, for example, "responsibility", with a length of 14, and attribute_value
could be, for example, "manager", with a length of 7.
For JDBC, use a command of the following form:
public void setApplicationContext(String CLIENTCONTEXT, string attribute, string value) throws SQLException;
where attribute
represents the attribute whose value needs to be set, and value
is the value to be assigned to that attribute.
For OCI, set the value to NULL or to an empty string by using one of the following command forms:
(void) OCIAppCtxSet((void *) session_handle, (dvoid *)"CLIENTCONTEXT", 13, (dvoid *)attribute_name, length_of_attribute_name, (dvoid *)0, 0,errhp, OCI_DEFAULT);
or
(void) OCIAppCtxSet((void *) session_handle, (dvoid *)"CLIENTCONTEXT", 13 (dvoid *)attribute_name, length_of_attribute_name, (dvoid *)"", 0,errhp, OCI_DEFAULT);
For JDBC, use the following command:
public void setApplicationContext(String CLIENTCONTEXT, string attribute, string value) throws SQLException;
where attribute
represents the attribute whose value needs to be cleared and value
is either 0 or the null string ""
.
For OCI, use a command of the following form:
err = OCIAppCtxClearAll((void *) session_handle, (dvoid *)"CLIENTCONTEXT", 13,
errhp, OCI_DEFAULT);
For JDBC, use a command of the following form:
public void clearAllApplicationContext(String CLIENTCONTEXT) throws SQLException;
Global application context stores context information in the System Global Area (SGA) so that it can be used for applications that use a sessionless model, such as middle-tier applications in a three-tiered architecture. These applications cannot use session-based application context because users authenticate to the application and then it typically connects to the database as a single identity. Global application context uses the CLIENT_IDENTIFIER
USERENV
namespace attribute, set using the DBMS_SESSION
interface, to associate the database session with a particular user or group. The following sections explain how to use the DBMS_SESSION
interface to set the CLIENT_IDENTIFIER
and then provide examples:
Using the DBMS_SESSION Interface to Manage Application Context in Client Sessions
Examples: Global Application Context
See Also:
"Introduction to Global Application Context" for conceptual information about this featureThe DBMS_SESSION
interface for managing application context has a client identifier for each application context. In this way, application context can be managed globally, yet each client sees only his or her assigned application context. The following interfaces in DBMS_SESSION
enable the administrator to manage application context in client sessions:
SET_CONTEXT
CLEAR_CONTEXT
CLEAR_ALL_CONTEXT
(can also be used with session-based application context)
SET_IDENTIFIER
CLEAR_IDENTIFIER
The middle-tier application server can use SET_CONTEXT
to set application context for a specific client ID. Then, when assigning a database connection to process the client request, the application server needs to issue a SET_IDENTIFIER
to denote the ID of the application session. From then on, every time the client invokes SYS_CONTEXT
, only the context that was associated with the set identifier is returned.
See Also:
PL/SQL Packages and Types Reference for reference information and a complete description of the DBMS_SESSION
package
"Using CLIENT_IDENTIFIER Independent of Global Application Context" for information about setting this USERENV
namespace attribute with the DBMS_SESSION
interface
This section provides two examples that use global application context.
The following steps outline the global application context process:
Consider the application server, AppSvr
, that has assigned the client identifier 12345
to client SCOTT
. It then issues the following statement to indicate that, for this client identifier, there is an application context called RESPONSIBILITY
with a value of 13
in the HR
namespace.
DBMS_SESSION.SET_CONTEXT( 'HR', 'RESPONSIBILITY' , '13', 'SCOTT', '12345' );
Note that HR
must be a global context namespace created as follows:
CREATE CONTEXT hr USING hr.init ACCESSED GLOBALLY;
Then, the following command is issued to indicate the connecting client identity each time SCOTT
uses AppSvr
to connect to the database:
DBMS_SESSION.SET_IDENTIFIER('12345');
When there is a SYS_CONTEXT('HR','RESPONSIBILITY')
call within the database session, the database engine matches the client identifier 12345
to the global context, and returns the value 13
.
When exiting this database session, AppSvr
clears the client identifier by issuing:
DBMS_SESSION.CLEAR_IDENTIFIER( );
Note:
After a client identifier in a session is cleared, it takes on aNULL
value. This implies that subsequent SYS_CONTEXT
calls only retrieve application contexts with NULL
client identifiers, until the client identifier is set again using the SET_IDENTIFIER
interface.The following steps outline the global application context process for a lightweight user application:
The administrator creates the global context namespace by using the following statement:
CREATE CONTEXT hr USING hr.init ACCESSED GLOBALLY;
The HR
application server (AppSvr
) starts up and establishes multiple connections to the HR
database as the APPSMGR
user.
User SCOTT
logs in to the HR
application server.
AppSvr
authenticates SCOTT
to the application.
AppSvr
assigns a temporary session ID (or simply uses the application user ID), 12345
, for this connection.
The session ID is returned to the browser used by SCOTT
as part of a cookie or maintained by AppSvr
.
Note:
If the application generates a session ID for use as aCLIENT_IDENTIFIER
, then the session ID must be suitably random and protected over the network by encryption. If the session ID is not random, then a malicious user could guess the session ID and access the data of another user. If the session ID is not encrypted over the network, then a malicious user could retrieve the session ID and access the connection.AppSvr
initializes application context for this client by calling the HR.INIT
package, which issues the following statements:
DBMS_SESSION.SET_CONTEXT( 'hr', 'id', 'scott', 'APPSMGR', 12345 ); DBMS_SESSION.SET_CONTEXT( 'hr', 'dept', 'sales', 'APPSMGR', 12345 );
AppSvr
assigns a database connection to this session and initializes the session by issuing the following statement:
DBMS_SESSION.SET_IDENTIFIER( 12345 );
All SYS_CONTEXT
calls within this database session will return application context values belonging only to the client session. For example, SYS_CONTEXT('hr','id')
will return the value SCOTT
.
When done with the session, AppSvr
can issue the following statement to clean up the client identity:
DBMS_SESSION.CLEAR_IDENTIFIER ( );
Note that even if another database user (ADAMS
) had logged into the database, he cannot access the global context set by AppSvr
because AppSvr
has specified that only the application with logged in user APPSMGR
can see it. If AppSvr
has used the following, then any user session with client ID set to 12345
can see the global context.
DBMS_SESSION.SET_CONTEXT( 'hr', 'id', 'scott', NULL , 12345 ); DBMS_SESSION.SET_CONTEXT( 'hr', 'dept', 'sales', NULL , 12345 );
This approach enables different users to share the same context.
Note:
Users must be aware of the security implication of different settings of the global context.NULL
in the user name means that any user can access the global context. A NULL
client ID in the global context means that only a session with an uninitialized client ID can access the global context.Users can query the client identifier set in the session as follows:
SYS_CONTEXT('USERENV','CLIENT_IDENTIFIER')
The DBA can see which sessions have the client identifier set by querying the V$SESSION
view for the CLIENT_IDENTIFIER
and USERNAME
.
When users want to see the amount of global context area (in bytes) being used, they can use SYS_CONTEXT('USERENV','GLOBAL_CONTEXT_MEMORY')
.
See Also:
For more information about using theCLIENT_IDENTIFIER
predefined attribute of the USERENV
application context:
Fine-grained access control is based on dynamically modified statements. Suppose you want to associate the ORDERS_TAB
table with the following security policy: Customers can see only their own orders. The process is described in this section.
Create a function to add a predicate to a DML statement run by a user.
Note:
A predicate is theWHERE
clause (a selection criterion clause) based on one of the operators (=
, !=
, IS
, IS NOT
, >
, >=
, EXIST
, BETWEEN
, IN
, NOT IN
, and so on). For a complete list of operators, refer to the Oracle Database SQL Reference.In this case, you might create a function that adds the following predicate:
Cust_no = (SELECT Custno FROM Customers WHERE Custname = SYS_CONTEXT ('userenv','session_user'))
A user enters the following statement:
SELECT * FROM Orders_tab;
The Oracle Database server calls the function you created to implement the security policy.
The function dynamically modifies the statement entered by the user to read as follows:
SELECT * FROM Orders_tab WHERE Custno = ( SELECT Custno FROM Customers WHERE Custname = SYS_CONTEXT('userenv', 'session_user'))
The Oracle Database server runs the dynamically modified statement.
Upon execution, the function employs the user name returned by SYS_CONTEXT ('userenv','session_user')
to look up the corresponding customer and to limit the data returned from the ORDERS_TAB
table to that associated with that particular customer only.
See Also:
For more information on using fine-grained access control:A policy group is a set of security policies that belong to an application. You can designate an application context (known as a driving context) to indicate the policy group in effect. Then, when the table, view, or synonym column is accessed, the server looks up the driving context (which is also known as policy context) to determine the policy group in effect. It enforces all the associated policies which belong to that policy group.
This section contains the following topics:
In the Oracle Policy Manager tree structure, the Fine-Grained Access Control Policies folder contains the Policy Groups folder. The Policy Groups folder contains an icon for each policy group, as well as an icon for the SYS_DEFAULT
policy group.
By default, all policies belong to the SYS_DEFAULT
policy group. Policies defined in this group for a particular table, view, or synonym will always be executed along with the policy group specified by the driving context. The SYS_DEFAULT
policy group may or may not contain policies. If you attempt to drop the SYS_DEFAULT
policy group, then an error will be raised.
If, to the SYS_DEFAULT
policy group, you add policies associated with two or more objects, then each such object will have a separate SYS_DEFAULT
policy group associated with it. For example, the EMP
table in the SCOTT
schema has one SYS_DEFAULT
policy group, and the DEPT
table in the SCOTT
schema has a different SYS_DEFAULT
policy group associated with it. These are displayed in the tree structure as follows:
SYS_DEFAULT - policy1 (SCOTT/EMP) - policy3 (SCOTT/EMP) SYS_DEFAULT - policy2 (SCOTT/DEPT)
Note:
Policy groups with identical names are supported. When you select a particular policy group, its associated schema and object name are displayed in the property sheet on the right-hand side of the screen.When adding the policy to a table, view, or synonym, you can use the DBMS_RLS.ADD_GROUPED_POLICY
interface to specify the group to which the policy belongs. To specify which policies will be effective, you add a driving context using the DBMS_RLS.ADD_POLICY_CONTEXT
interface. If the driving context returns an unknown policy group, then an error is returned.
If the driving context is not defined, then all policies are executed. Likewise, if the driving context is NULL
, then policies from all policy groups are enforced. In this way, an application accessing the data cannot bypass the security setup module (which sets up application context) to avoid any applicable policies.
You can apply multiple driving contexts to the same table, view, or synonym, and each of them will be processed individually. In this way, you can configure multiple active sets of policies to be enforced.
Consider, for example, a hosting company that hosts Benefits and Financial applications, which share some database objects. Both applications are striped for hosting using a SUBSCRIBER
policy in the SYS_DEFAULT
policy group. Data access is partitioned first by subscriber ID, then by whether the user is accessing the Benefits or Financial applications (determined by a driving context). Suppose that Company A, which uses the hosting services, wants to apply a custom policy which relates only to its own data access. You could add an additional driving context (such as COMPANY A SPECIAL
) to ensure that the additional, special policy group is applied for data access for Company A only. You would not apply this under the SUBSCRIBER
policy, because the policy relates only to Company A, and it is more efficient to segregate the basic hosting policy from other policies.
To create policy groups, the administrator must do two things:
Set up a driving context to identify the effective policy group.
Add policies to policy groups as required.
The following example shows how to perform these tasks.
Note:
You need to set up the following data structures for the examples in this section to work:DROP USER finance CASCADE; CREATE USER finance IDENTIFIED BY welcome2; GRANT RESOURCE TO apps; DROP TABLE apps.benefit; CREATE TABLE apps.benefit (c NUMBER);
Begin by creating a namespace for the driving context. For example:
CREATE CONTEXT appsctx USING apps.apps_security_init;
Create the package that administers the driving context. For example:
CREATE OR REPLACE PACKAGE apps.apps_security_init IS PROCEDURE setctx (policy_group VARCHAR2); END; CREATE OR REPLACE PACKAGE BODY apps.apps_security_init AS PROCEDURE setctx ( policy_group varchar2 ) IS BEGIN REM Do some checking to determine the current application. REM You can check the proxy if using the proxy authentication feature. REM Then set the context to indicate the current application. . . . DBMS_SESSION.SET_CONTEXT('APPSCTX','ACTIVE_APPS', policy_group); END; END;
Define the driving context for the table APPS.BENEFIT
.
BEGIN DBMS_RLS.ADD_POLICY_CONTEXT('apps','benefit','APPSCTX','ACTIVE_APPS'); END;
Create a security function to return a predicate to divide the data by company.
CREATE OR REPLACE FUNCTION by_company (sch varchar2, tab varchar2) RETURN VARCHAR2 AS BEGIN RETURN 'COMPANY = SYS_CONTEXT(''ID'',''MY_COMPANY'')'; END;
Because policies in SYS_DEFAULT
are always executed (except for SYS
, or users with the EXEMPT ACCESS POLICY
system privilege), this security policy (named SECURITY_BY_COMPANY
), will always be enforced regardless of the application running. This achieves the universal security requirement on the table: namely, that each company should see its own data regardless of the application that is running. The function APPS.APPS_SECURITY_INIT.BY_COMPANY
returns the predicate to make sure that users can only see data related to their own company:
BEGIN DBMS_RLS.ADD_GROUPED_POLICY('apps','benefit','SYS_DEFAULT', 'security_by_company', 'apps','by_company'); END;
First, create the HR
group:
CREATE OR REPLACE FUNCTION hr.security_policy(sch varchar2, tab varchar2) RETURN VARCHAR2 AS BEGIN RETURN 'SYS_CONTEXT(''ID'',''TITLE'') = ''MANAGER'' '; END;
The following creates the policy group and adds a policy named HR_SECURITY
to the HR
policy group. The function HR.SECURITY_POLICY
returns the predicate to enforce security on the APPS.BENEFIT
table:
BEGIN DBMS_RLS.CREATE_POLICY_GROUP('apps','benefit','HR'); DBMS_RLS.ADD_GROUPED_POLICY('apps','benefit','HR', 'hr_security','hr','security_policy'); END;
Create the FINANCE
policy:
CREATE OR REPLACE FUNCTION finance.security_policy RETURN VARCHAR2 AS BEGIN RETURN ('SYS_CONTEXT(''ID'',''DEPT'') = ''FINANCE'' '); END;
Create a policy group named FINANCE
and add the FINANCE
policy to the FINANCE
group:
BEGIN DBMS_RLS.CREATE_POLICY_GROUP('apps','benefit','FINANCE'); DBMS_RLS.ADD_GROUPED_POLICY('apps','benefit','FINANCE', 'finance_security','finance', 'security_policy'); END;
As a result, when the database is accessed, the application initializes the driving context after authentication. For example, with the HR
application:
execute apps.security_init.setctx('HR');
The package implementing the driving context must correctly validate the application that is being used to connect to the database. Although the database always checks the call stack to ensure that the package implementing the driving context sets context attributes, inadequate validation can still occur within the package.
For example, in applications where database users or enterprise users are known to the database, the user needs the EXECUTE
privilege on the package that sets the driving context. Consider a user who knows that:
The BENEFITS
application allows more liberal access than the HR
application
The setctx
procedure (which sets the correct policy group within the driving context) does not perform any validation to determine which application is actually connecting. That is, the procedure does not check either the IP address of the incoming connection (for a three-tier system) or the proxy_user
attribute of the user session.
Such a user could pass to the driving context package an argument setting the context to the more liberal BENEFITS
policy group, and then access the HR
application instead. Because the setctx
does no further validation of the application, this user bypasses the normally more restrictive HR security policy.
By contrast, if you implement proxy authentication with VPD, then you can determine the identity of the middle tier (and the application) that is actually connecting to the database on behalf of a user. In this way, the correct policy will be applied for each application to mediate data access.
For example, a developer using the proxy authentication feature could determine that the application (the middle tier) connecting to the database is HRAPPSERVER
. The package that implements the driving context can thus verify whether the proxy_user
in the user session is HRAPPSERVER
. If so, then it can set the driving context to use the HR
policy group. If proxy_user
is not HRAPPSERVER
, then it can disallow access.
In this case, when the following query is executed
SELECT * FROM APPS.BENEFIT;
Oracle Database picks up policies from the default policy group (SYS_DEFAULT
) and active namespace HR
. The query is internally rewritten as follows:
SELECT * FROM APPS.BENEFIT WHERE COMPANY = SYS_CONTEXT('ID','MY_COMPANY') and SYS_CONTEXT('ID','TITLE') = 'MANAGER';
The DBMS_RLS
package enables you to administer security policies by using its procedures for adding, enabling, refreshing, or dropping policies, policy groups, or application contexts. You need to specify the table, view, or synonym to which you are adding a policy, as well as the data pertinent to that policy, such as the policy name. Such data also includes names for the policy group and the function implementing the policy. You can also specify the types of statements the policy controls (SELECT
, INSERT
, UPDATE
, DELETE
, CREATE INDEX
, or ALTER INDEX
). Table 15-2 lists the procedures in the DBMS_RLS
package.
Table 15-2 DBMS_RLS Procedures
Procedure | Purpose |
---|---|
For Handling Individual Policies |
|
To add a policy to a table, view, or synonym |
|
To enable (or disable) a policy you previously added to a table, view, or synonym |
|
To invalidate cursors associated with non-static policies |
|
To drop a policy from a table, view, or synonym |
|
For Handling Grouped Policies |
|
To create a policy group |
|
To drop a policy group |
|
To add a policy to the specified policy group |
|
To enable a policy within a group |
|
To reparse the SQL statements associated with a refreshed policy |
|
To disable a policy within a group |
|
To drop a policy which is a member of the specified group |
|
For Handling Application Context |
|
To add the context for the active application |
|
To drop the context for the application |
Alternatively, you can use Oracle Policy Manager to administer security policies.
See Also:
PL/SQL Packages and Types Reference for information about using the DBMS_RLS package and all of its procedures and parametersThe execution of policy functions can consume a significant amount of system resources. If you can minimize the number of times that policy functions must run, then you can optimize your database server performance. To avoid unnecessary policy function execution, you can choose from five different policy types, which enable you to precisely specify how and how often a policy predicate should change. You can enable these different types of policies, which are listed in Table 15-3, by setting the policy_type
parameter of the DBMS_RLS.ADD POLICY
procedure.
Table 15-3 DBMS_RLS.ADD_POLICY Policy Types At a Glance
Policy Types | When Policy Function Executes... | Usage Example | Shared Across Multiple Objects? |
---|---|---|---|
|
Once, then the predicate is cached in the SGAFoot 1 |
View replacement |
No |
|
Same as |
Hosting environments, such as data warehouses where the same predicate must be applied to multiple database objects |
Yes |
|
|
3-tier, session pooling applications where policies enforce two or more predicates for different users or groups |
No |
|
First time the object is reference in a database session Predicates are cached in the private session memory UGA so policy functions can be shared among objects. |
Same as |
Yes |
|
Policy function re-executes every time a policy-protected database object is accessed. |
Applications where policy predicates must be generated for each query, such as time-dependent policies where users are denied access to database objects at certain times during the day |
No |
Footnote 1 Each execution of the same cursor could produce a different row set even for the same predicate because the predicate may filter the data differently based on attributes such as SYS_CONTEXT
or SYSDATE
.
Static and context sensitive policies enable you to optimize server performance, because they do not run the policy function each time protected database objects are accessed. However, Oracle recommends that before you enable policies as either static or context-sensitive, you first test them as DYNAMIC
policy types, which run every time. Testing policy functions as DYNAMIC
policies first enables you to observe how the policy function affects each query, because nothing is cached. This ensures that the functions work properly before you enable them as static or context-sensitive policy types to optimize performance.
Dynamic policies are the system default. If you do not specify a policy type with the DBMS_RLS.ADD_POLICY
procedure, then by default your policy will be dynamic. You can specifically configure a policy to be dynamic by setting the policy_type
parameter of the DBMS_RLS.ADD_POLICY
procedure to DYNAMIC
. Refer to Example 15-1 for the syntax.
Example 15-1 Syntax for Enabling Policy Types with DBMS_RLS.ADD_POLICY
DBMS_RLS.ADD_POLICY (
.
.
.
policy_type => dbms_rls.POLICY_TYPE);
Note:
TheDBMS_RLS.ADD POLICY
policy_type
parameter is intended to replace the static_policy
parameter, which may be deprecated in future releases.See Also:
The following topics for a more detailed discussion of static and context-sensitive policies:In previous releases, policies were dynamic, which means that the database runs the policy function for each query or DML statement. In addition to dynamic policies, the current release of Oracle Database provides static and context-sensitive policies. These policy types provide a means to improve server performance, because they do not always rerun policy functions for each DML statement and can be shared across multiple database objects.
Note:
When using shared static and shared context-sensitive policies, ensure that the policy predicate does not contain attributes that are specific to a particular database object, such as a column name.Static policy predicates are cached in SGA, so policy functions do not rerun for each query, resulting in faster performance. When you specify a static policy, the same predicate is always enforced for all users in the instance. However, each execution of the same cursor could produce a different row set even for the same predicate, because the predicate may filter the data differently based on attributes such as SYS_CONTEXT
or SYSDATE
.
For example, suppose you enable a policy as either a STATIC
or SHARED_STATIC
policy type, which appends the following predicate to all queries made against policy protected database objects:
WHERE dept=SYS_CONTEXT ('HR_APP','deptno')
Although the predicate does not change for each query, it applies to the query based on session attributes of the SYS_CONTEXT
. In the case of the preceding example, the predicate would return only those rows where the department number matches the deptno
attribute of the SYS_CONTEXT
, which would be the department number of the user who is querying the policy-protected database object.
You can enable static policies by setting the policy_type
parameter of the DBMS_RLS.ADD_POLICY
procedure to either STATIC
or SHARED_STATIC
, depending on whether or not you want the policy to be shared across multiple objects. (Refer to Example 15-1 for the syntax.)
Static policies are ideal for environments where every query requires the same predicate and fast performance is essential, such as hosting environments. For these situations when the policy function appends the same predicate to every query, rerunning the policy function each time adds unnecessary overhead to the system. For example, consider a data warehouse that contains market research data for customer organizations that are competitors of each other. The warehouse must enforce the policy that each organization can see only their own market research, which is expressed by the predicate WHERE subscriber_id=SYS_CONTEXT('customer', 'cust_num')
. Using SYS_CONTEXT
for the application context enables the database to dynamically change the rows that are returned. There is no need to rerun the function, so the predicate can be cached in the SGA, thus conserving system resources and improving performance.
In contrast to static policies, context-sensitive policies do not always cache the predicate. With context-sensitive policies, the server assumes that the predicate will change after statement parse time. But if there is no change in local application context, the server does not rerun the policy function within the user session. If there has been a change in context, then the server reruns the policy function to ensure that it captures any changes to the predicate since the initial parsing. These policies are useful where different predicates should apply depending on which user is executing the query. For example, consider the case where managers should always have the predicate WHERE group=managers
and employees should always have the predicate WHERE empno=emp_id
.
Shared context-sensitive policies operate in the same way as regular context-sensitive policies, except they can be shared across multiple database objects. For this policy type, all objects can share the policy function from the UGA, where the predicate is cached until the local session context changes.
You can enable context-sensitive policies by setting the policy_type
parameter of the DBMS_RLS.ADD_POLICY
procedure to either CONTEXT_SENSITIVE
or SHARED_CONTEXT_SENSITIVE
. (Refer to Example 15-1 for the syntax.)
This type of policy is useful when a predicate need not change for a user session, but the policy must enforce two or more different predicates for different users or groups. For example, consider a SALES_HISTORY
table with a single policy, which states that analysts can see only their own products and regional employees can see only their own region. In this case, the server must rerun the policy function each time the type of user changes. The performance gain is realized when a user can log in and issue several DML statements against the protected object without causing the server to rerun the policy function.
Note:
For session pooling where multiple clients share a database session, the middle tier must reset the context during client switches.Column-level VPD, which can be applied to a table or a view, enables you to enforce security when a security-relevant column is referenced in a query, resulting in row-level security. Column-level VPD cannot be applied to a synonym.
It can be configured to produce two distinct behaviors as follows:
The following example shows a VPD policy in which sales department users should not see the salaries of people outside their own department (department number 30). The relevant columns for such a policy are SAL
and COMM
. First, the VPD policy function is created and then added by using the DBMS_RLS
PL/SQL package as shown in Example 15-2.
Example 15-2 Creating and Adding a Column-Level VPD Policy
*/Create a policy function which does not expose salaries of employees outside the sales department (department 30)/* CREATE OR REPLACE FUNCTION pf1 (oowner IN VARCHAR2, ojname IN VARCHAR2) RETURN VARCHAR2 AS con VARCHAR2 (200); BEGIN con := 'deptno=30'; RETURN (con); END pf1;
Then the policy is added with the DBMS_RLS
package as follows:
BEGIN DBMS_RLS.ADD_POLICY (object_schema=>'scott', object_name=>'emp', policy_name=>'sp', function_schema=>'pol_admin', policy_function=>'pf1', sec_relevant_cols=>'sal,comm'); END;
The different behaviors of column-level VPD are discussed in the following sections using Example 15-2 as a starting point for discussion.
The default behavior for column-level VPD is to restrict the number of rows returned for a query that references columns containing sensitive information. These security-relevant columns are specified with the sec_relevant_cols
parameter of the DBMS_RLS.ADD_POLICY
procedure.
For an example of column-level VPD default behavior, consider sales department users with SELECT
privilege on the emp
table, which is protected with the column-level VPD policy created in Example 15-2. When users run the following query:
SELECT ENAME, d.dname, JOB, SAL, COMM from emp e, dept d WHERE d.deptno = e.deptno;
the database returns a subset of rows as follows:
ENAME DNAME JOB SAL COMM -------------- -------------- ------------ ------------ ------------- ALLEN SALES SALESMAN 1600 300 WARD SALES SALESMAN 1250 500 MARTIN SALES SALESMAN 1250 1400 BLAKE SALES MANAGER 2850 TURNER SALES SALESMAN 1500 0 JAMES SALES CLERK 950
Only those rows are displayed in which the user should have access to all columns.
In contrast to the default behavior of column-level VPD, column-masking displays all rows, but returns sensitive column values as NULL
. To include column-masking in your policy, set the sec_relevant_cols_opt
parameter of the DBMS_RLS.ADD_POLICY
procedure to dbms_rls.ALL_ROWS
. Also set the default behavior parameter.
Example 15-3 shows column-level VPD column-masking. It uses the same VPD policy as Example 15-2 but with sec_relevant_cols_opt
specified as dbms_rls.ALL_ROWS
.
Example 15-3 Adding a Column-level VPD Policy with Column-masking Behavior
*/add the ALL_ROWS policy/* BEGIN DBMS_RLS.ADD_POLICY(object_schema=>'scott', object_name=>'emp', policy_name=>'sp', function_schema=>'pol_admin', policy_function=>'pf1', sec_relevant_cols=>'sal,comm', sec_relevant_cols_opt=>dbms_rls.ALL_ROWS); END;
Assume that a sales department user with SELECT
privilege on the emp table runs the following query:
SELECT ENAME, d.dname, JOB, SAL, COMM from emp e, dept d WHERE d.deptno = e.deptno;
The database returns all rows specified in the query, but with certain values masked because of the VPD policy:
ENAME DNAME JOB SAL COMM -------------- -------------- ------------ ------------ ------------- SMITH RESEARCH CLERK ALLEN SALES SALESMAN 1600 300 WARD SALES SALESMAN 1250 500 JONES RESEARCH MANAGER MARTIN SALES SALESMAN 1250 1400 BLAKE SALES MANAGER 2850 CLARK ACCOUNTING MANAGER SCOTT RESEARCH ANALYST KING ACCOUNTING PRESIDENT TURNER SALES SALESMAN 1500 0 ADAMS RESEARCH CLERK JAMES SALES CLERK 950 FORD RESEARCH ANALYST MILLER ACCOUNTING CLERK
Note that column-masking has returned all rows requested by the sales user query, but has made the SAL
and COMM
columns NULL
for employees outside the sales department.
Column-masking applies only to SELECT
statements.
Column-masking conditions generated by the policy function must be a simple Boolean expressions, unlike regular VPD predicates.
For applications that perform calculations, or do not expect NULL
values, use standard column-level VPD, specifying sec_relevant_cols
rather than column-masking.
Column-masking used with UPDATE AS SELECT
will update only the columns that users are allowed to see.
For some queries, column-masking may prevent some rows from displaying. For example:
SELECT * FROM employees WHERE salary = 10
This query may not return rows if the salary
column returns a NULL
value, because the column-masking option has been set.
See Also:
The chapter on theDBMS_RLS
package in PL/SQL Packages and Types Reference for a discussion of parameters and usage examples for the DBMS_RLS.ADD_POLICY
procedureVPD policies can be enforced for SELECT
, INSERT
, UPDATE
, INDEX
, and DELETE
statements. Specify any combination of these statement types with the DBMS_RLS.ADD_POLICY
procedure statement_types
parameter as follows:
DBMS_RLS.ADD_POLICY (
. . .
statement_types=>'SELECT,INDEX');
A user who has privileges to maintain an index can see all the row data even if the user does not have full table access under a regular query, such as SELECT
. For example, a user can create a function-based index that contains a user-defined function with column values as its arguments. During index creation, the server passes column values of every row into the user function, making the row data available to the user who creates the index. Administrators can enforce VPD policies on index maintenance operations by specifying INDEX
with the statement_types
parameter as shown in the previous section.
V$VPD_POLICY
allows one to perform a dynamic view in order to check what policies are being applied to a SQL statement. When debugging, in your attempt to find which policy corresponds to a particular SQL statement, you should use the following table.
Column Name | Type |
---|---|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
Two classes of users are exempt from VPD policies: the SYS
user is exempt by default, and any other user can be exempt if granted the EXEMPT ACCESS POLICY
system privilege. These two cases are discussed in the following sections.
The database user SYS
is always exempt from VPD or Oracle Label Security policy enforcement, regardless of the export mode, application, or utility that is used to extract data from the database. However, SYSDBA
actions can be audited.
The system privilege EXEMPT ACCESS POLICY
allows a user to be exempted from all fine-grained access control policies on any SELECT
or DML operation (INSERT
, UPDATE
, and DELETE
). This provides ease of use for administrative activities such as installation and import and export of the database through a non-SYS
schema.
Also, regardless of the utility or application that is being used, if a user is granted the EXEMPT ACCESS POLICY
privilege, then the user is exempt from VPD and Oracle Label Security policy enforcement. That is, the user will not have any VPD or Oracle Label Security policies applied to their data access.
Because EXEMPT ACCESS POLICY
negates the effect of fine-grained access control, this privilege should only be granted to users who have legitimate reasons for bypassing fine-grained access control enforcement. This privilege should not be granted WITH ADMIN OPTION
, so that users cannot pass on the EXEMPT ACCESS POLICY
privilege to other users, and thus propagate the ability to bypass fine-grained access control.
Note:
This feature is applicable whenCOMPATIBLE
is set to 9.0.1.Starting from Oracle9i, queries against objects enabled with fine-grained access control always run the policy function to make sure that the most current predicate is used for each policy. For example, in the case of a time-based policy function, in which queries are only allowed between 8:00 a.m. and 5:00 p.m., a cursor execution parsed at noon cause the policy function to run, ensuring that the policy is consulted again for the query.
Automatic reparse does not occur under the following conditions:
When you specify the STATIC_POLICY=TRUE
while adding the policy to indicate that the policy function always returns the same predicate.
When you set the _dynamic_rls_policies
parameter to FALSE
in the initialization parameters files. Typically, this parameter is set to FALSE
for users whose security policies do not return different predicates within a database session to reduce the execution overhead.
For deployment environments where the latest application context value is always the desired value, the _app_ctx_vers
parameter can be set to FALSE
in the initialization parameters file to reduce the overhead of application context scoping. By default, it is set to TRUE
and changes of value within a SQL statement are not visible. This default may change in the future, thus developers should be careful not to allow changes of application context values within a SQL statement using a user-defined function. In general, you should not depend on the sequence of SQL statement execution, which can yield inconsistent results depending on query plans.
See Also:
"Using Dynamic SQL with SYS_CONTEXT"By default, operations on the database use the most recent committed data available. The flashback query feature enables you to query the database as it was at some time in the past. To write an application that uses flashback query, you can use the AS OF
clause in SQL queries to specify either a time or a system change number (SCN) and then query against the committed data from the specified time. You can also use the DBMS_FLASHBACK
PL/SQL package, which requires more code, but enables you to perform multiple operations, all of which refer to the same past time.
Flashback queries return data as it stood at the time specified in the query. However, if you use flashback query against a database object that is protected with VPD policies, then the current policies are applied to the old data. Applying the current VPD policies to flashback query data is more secure because it reflects the most current business policy.
See Also:
Oracle Database Application Developer's Guide - Fundamentals for more information about the flashback query feature and how to write applications that use it
PL/SQL Packages and Types Reference for more information about the DBMS_FLASHBACK
PL/SQL package