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| Oracle8 Administrator's Guide Release 8.0 A58397-01 |
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This chapter explains how to control the ability to execute system operations and access to schema objects using privileges and roles. The following topics are included:
See Also: For information about controlling access to a database, see Chapter 20.
For suggested general database security policies, see Chapter 19.
This chapter contains several references to Oracle Enterprise Manager. For more information about performing specific tasks using Enterprise Manager/GUI or Server Manager/LineMode, see the Oracle Enterprise Manager Administrator's Guide or Oracle Server Manager User's Guide.
This section describes Oracle user privileges, and includes the following topics:
A user privilege is a right to execute a particular type of SQL statement, or a right to access another user's object. Oracle also provides shortcuts for grouping privileges that are commonly granted or revoked together.
There are over 80 distinct system privileges. Each system privilege allows a user to perform a particular database operation or class of database operations. Table 21-1 lists all system privileges and the operations that they permit.
For security reasons, system privileges do not allow users to access the data dictionary. Hence, users with ANY privileges (such as UPDATE ANY TABLE, SELECT ANY TABLE or CREATE ANY INDEX) cannot access dictionary tables and views that have not been granted to PUBLIC.
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warning: System privileges can be very powerful, and should be cautiously granted to roles and trusted users of the database. Users with the ANY privilege cannot access the data dictionary. |
The dictionary protection mechanism prevents unauthorized users from accessing dictionary objects.
Access to dictionary objects is restricted to the users SYSDBA and SYSOPER. System privileges providing access to objects in other schemas do not give you access to dictionary objects. For example, the SELECT ANY TABLE privilege allows you to access views and tables in other schemas, but does not enable you to select dictionary objects (base tables, views, packages, and synonyms).
Also, attempting to connect with the SQL*Plus command connect SYS/password results in failure. However, the following two SQL*Plus commands are valid:
connect SYS/password as SYSDBA connect SYS/password as SYSOPER
Use the 07_DICTIONARY_ACCESSIBILITY parameter (default=TRUE) to revert the behavior to Oracle7 (and remove the restrictions on system privileges).
See Also: For details about the 07_DICTIONARY_ACCESSIBILITY parameter, see the Oracle8 Reference.
Users with explicit object privileges and the SYSDBA can access dictionary objects. If, however, you need access to dictionary objects and do not have explicit object privileges, you can be granted the following roles:
Enables users to SELECT all exported catalog views and tables granted to this role. Grant this role to users who must access all exported views and tables in the data dictionary.
Provides EXECUTE privilege on exported packages in the dictionary.
Enables users to delete records from the AUD$ table.
These roles enable database administrators to access certain objects in the dictionary while maintaining dictionary security.
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Note: SYSDBA should not grant any user the object privileges for non-exported objects in the dictionary; doing so may compromise the integrity of the database. |
See Also: For details about any exported table or view, see the Oracle8 Reference.
Each type of object has different privileges associated with it. Table 21-2 summarizes the object privileges available for each type of object.
Not all types of schema objects are included in Table 21-2. Many of the schema objects not listed here (such as clusters, indexes, triggers, and database links) are controlled exclusively using system privileges. For example, to alter a cluster, a user must own the cluster or have the ALTER ANY CLUSTER system privilege.
Table 21-3 lists the SQL statements permitted by the object privileges listed in Table 21-2.
The ALL and ALL PRIVILEGES shortcuts grant or revoke all available object privileges for a object. This shortcut is not a privilege, rather, it is a way of granting or revoking all object privileges with one word in GRANT and REVOKE statements. Note that if all object privileges are granted using the ALL shortcut, individual privileges can still be revoked.
Likewise, all individually granted privileges can be revoked using the ALL shortcut. However, if you REVOKE ALL, and revoking causes integrity constraints to be deleted (because they depend on a REFERENCES privilege that you are revoking), you must include the CASCADE CONSTRAINTS option in the REVOKE statement.
This section describes aspects of managing roles, and includes the following topics:
A role groups several privileges and roles, so that they can be granted and revoked simultaneously from users. Roles can be enabled and disabled per user.
See Also: For information about roles, see Oracle8 Concepts.
You can create a role using either the SQL command CREATE ROLE, or the Create Role property sheet of Enterprise Manager.
You must have the CREATE ROLE system privilege to create a role. Typically, only security administrators have this system privilege.
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Note: Immediately after creation, a role has no privileges associated with it. To associate privileges with a new role, you must grant privileges or other roles to the new role. |
The following statement creates the CLERK role, which is authorized by the database using the password BICENTENNIAL:
CREATE ROLE clerk IDENTIFIED BY bicentennial;
You must give each role you create a unique name among existing usernames and role names of the database. Roles are not contained in the schema of any user.
In a database that uses a multi-byte character set, Oracle Corporation recommends that each role name contain at least one single-byte character. If a role name contains only multi-byte characters, the encrypted role name/password combination is considerably less secure.
The roles listed in Table 21-4 are automatically defined for Oracle databases. These roles are provided for backward compatibility to earlier versions of Oracle. You can grant and revoke privileges and roles to these predefined roles, much the way you do with any role you define.
A database role can optionally require authorization when a user attempts to enable the role. Role authorization can be maintained by the database (using passwords), by the operating system, or by a network service.
To alter the authorization method for a role, you must have the ALTER ANY ROLE system privilege or have been granted the role with the ADMIN OPTION.
See Also: For more information about network roles, see Oracle8 Distributed Database Systems.
The use of a role can be protected by an associated password. If you are granted a role protected by a password, you can enable or disable the role only by supplying the proper password for the role in a SET ROLE command.
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Note: In a database that uses a multi-byte character set, passwords for roles must include only single-byte characters. Multi-byte characters are not accepted in passwords. |
See Also: For more information about valid passwords, see the Oracle8 Reference.
The following statement creates a role named ACCTS_REC and requires that the operating system authorize its use:
CREATE ROLE role IDENTIFIED EXTERNALLY;
Role authentication via the operating system is useful only when the operating system must be able to dynamically link operating system privileges with applications. When a user starts an application, the operating system grants an operating system privilege to the user. The granted operating system privilege corresponds to the role associated with the application. At this point, the application can enable the application role. When the application is terminated, the previously granted operating system privilege is revoked from the user's operating system account.
If a role is authorized by the operating system, you must configure information for each user at the operating system level. This operation is operating system dependent.
If roles are granted by the operating system, you do not need to have the operating system authorize them also; this is redundant.
See Also: For more information about roles granted by the operating system, see "Granting Roles Using the Operating System or Network".
If users connect to the database over SQL*Net, by default their roles cannot be authenticated by the operating system. This includes connections through a multi-threaded server, as this connection requires SQL*Net. This restriction is the default because a remote user could impersonate another operating system user over a network connection.
If you are not concerned with this security risk and want to use operating system role authentication for network clients, set the parameter REMOTE_OS_ROLES in the database's parameter file to TRUE. The change will take effect the next time you start the instance and mount the database. (The parameter is FALSE by default.)
A role can also be created without authorization. If a role is created without any protection, the role can be enabled or disabled by any grantee.
You can set and change the authorization method for a role using either the Alter Role property sheet of Enterprise Manager/GUI or the SQL command ALTER ROLE.
The following statement alters the CLERK role to be authorized externally:
ALTER ROLE clerk IDENTIFIED EXTERNALLY;
A user's list of default roles can be set and altered using either the Alter User dialog box of Enterprise Manager or the SQL command ALTER USER.
See Also: See "Altering Users" for more information about these options.
If the user's list of default roles is specified as ALL, every role granted to a user is automatically added to the user's list of default roles. Only subsequent modification of a user's default role list can remove newly granted roles from a user's list of default roles.
A user can enable as many roles as specified by the initialization parameter MAX_ENABLED_ROLES. All indirectly granted roles enabled as a result of enabling a primary role are included in this count. The database administrator can alter this limitation by modifying the value for this parameter. Higher values permit each user session to have more concurrently enabled roles. However, the larger the value for this parameter, the more memory space is required on behalf of each user session; this is because the PGA size is affected for each user session, and requires four bytes per role. Determine the highest number of roles that will be concurrently enabled by any one user and use this value for the MAX_ENABLED_ROLES parameter.
In some cases, it may be applicable to drop a role from the database. The security domains of all users and roles granted a dropped role are immediately changed to reflect the absence of the dropped role's privileges. All indirectly granted roles of the dropped role are also removed from affected security domains. Dropping a role automatically removes the role from all users' default role lists.
Because the creation of objects is not dependent on the privileges received via a role, tables and other objects are not dropped when a role is dropped.
To drop a role, you must have the DROP ANY ROLE system privilege or have been granted the role with the ADMIN OPTION.
You can drop a role using either the Drop menu item of Enterprise Manager or the SQL command DROP ROLE.
The following statement drops the role CLERK:
DROP ROLE clerk;
This section describes aspects of granting privileges and roles, and includes the following topics:
You can grant system privileges and roles to other roles and users using either the Grant System Privileges/Roles dialog box of Enterprise Manager or the SQL command GRANT.
To grant a system privilege or role, you must have the ADMIN OPTION for all system privileges and roles being granted. Also, any user with the GRANT ANY ROLE system privilege can grant any role in a database.
The following statement grants the system privilege and the ACCTS_PAY role to the user JWARD:
GRANT create session, accts_pay TO jward;
When a user creates a role, the role is automatically granted to the creator with the ADMIN OPTION. A grantee with the ADMIN option has several expanded capabilities:
In the following statement, the security administrator grants the NEW_DBA role to MICHAEL:
GRANT new_dba TO michael WITH ADMIN OPTION;
The user MICHAEL cannot only use all of the privileges implicit in the NEW_DBA role, but can grant, revoke, or drop the NEW_DBA role as deemed necessary. Because of these powerful capabilities, exercise caution when granting system privileges or roles with the ADMIN OPTION. Such privileges are usually reserved for a security administrator and rarely granted to other administrators or users of the system.
You can grant object privileges to roles and users using the Add Privilege to Role/User dialog box of Enterprise Manager or the SQL command GRANT.
To grant an object privilege, you must fulfill one of the following conditions:
The following statement grants the SELECT, INSERT, and DELETE object privileges for all columns of the EMP table to the users JFEE and TSMITH:
GRANT select, insert, delete ON emp TO jfee, tsmith;
To grant the INSERT object privilege for only the ENAME and JOB columns of the EMP table to the users JFEE and TSMITH, issue the following statement:
GRANT insert(ename, job) ON emp TO jfee, tsmith;
To grant all object privileges on the SALARY view to the user JFEE, use the ALL shortcut, as shown in the following example:
GRANT ALL ON salary TO jfee;
The user whose schema contains an object is automatically granted all associated object privileges with the GRANT OPTION. This special privilege allows the grantee several expanded privileges:
The GRANT OPTION is not valid when granting an object privilege to a role. Oracle prevents the propagation of object privileges via roles so that grantees of a role cannot propagate object privileges received by means of roles.
You can grant INSERT, UPDATE, or REFERENCES privileges on individual columns in a table.
Grant INSERT privilege on the ACCT_NO column of the ACCOUNTS table to SCOTT:
GRANT INSERT (acct_no) ON accounts TO scott;
This section describes aspects of revoking user privileges and roles, and includes the following topics:
You can revoke system privileges and/or roles using either the Revoke System Privileges/Roles dialog box of Enterprise Manager or the SQL command REVOKE.
Any user with the ADMIN OPTION for a system privilege or role can revoke the privilege or role from any other database user or role The grantor does not have to be the user that originally granted the privilege or role. Also, users with the GRANT ANY ROLE can revoke any role.
The following statement revokes the CREATE TABLE system privilege and the ACCTS_REC role from TSMITH:
REVOKE create table, accts_rec FROM tsmith;
You can revoke object privileges using Enterprise Manager or the SQL command REVOKE.
To revoke an object privilege, the revoker must be the original grantor of the object privilege being revoked.
For example, assuming you are the original grantor, to revoke the SELECT and INSERT privileges on the EMP table from the users JFEE and TSMITH, you would issue the following statement:
REVOKE select, insert ON emp FROM jfee, tsmith;
The following statement revokes all privileges (which were originally granted to the role HUMAN_RESOURCE) from the table DEPT:
REVOKE ALL ON dept FROM human_resources;
Although users can grant column selective INSERT, UPDATE, and REFERENCES privileges for tables and views, they cannot selectively revoke column specific privileges with a similar REVOKE statement. Instead, the grantor must first revoke the object privilege for all columns of a table or view, and then selectively re-grant the column specific privileges that should remain.
For example, assume that role HUMAN_RESOURCES has been granted the UPDATE privilege on the DEPTNO and DNAME columns of the table DEPT. To revoke the UPDATE privilege on just the DEPTNO column, you would issue the following two statements:
REVOKE UPDATE ON dept FROM human_resources; GRANT UPDATE (dname) ON dept TO human_resources;
The REVOKE statement revokes UPDATE privilege on all columns of the DEPT table from the role HUMAN_RESOURCES. The GRANT statement re-grants UPDATE privilege on the DNAME column to the role HUMAN_RESOURCES.
If the grantee of the REFERENCES object privilege has used the privilege to create a foreign key constraint (that currently exists), the grantor can only revoke the privilege by specifying the CASCADE CONSTRAINTS option in the REVOKE statement:
REVOKE REFERENCES ON dept FROM jward CASCADE CONSTRAINTS;
Any foreign key constraints currently defined that use the revoked REFERENCES privilege are dropped when the CASCADE CONSTRAINTS options is specified.
Depending on the type of privilege, there may be cascading effects when a privilege is revoked.
There are no cascading effects when revoking a system privilege related to DDL operations, regardless of whether the privilege was granted with or without the ADMIN OPTION. For example, assume the following:
Cascading effects can be observed when revoking a system privilege related to a DML operation. For example, if SELECT ANY TABLE is granted to a user, and that user has created any procedures, all procedures contained in the user's schema must be re-authorized before they can be used again.
Revoking an object privilege may have cascading effects that should be investigated before issuing a REVOKE statement.
Privileges and roles can also be granted to and revoked from the user group PUBLIC. Because PUBLIC is accessible to every database user, all privileges and roles granted to PUBLIC are accessible to every database user.
Security administrators and database users should only grant a privilege or role to PUBLIC if every database user requires the privilege or role. This recommendation reinforces the general rule that at any given time, each database user should only have the privileges required to accomplish the group's current tasks successfully.
Revoking a privilege from PUBLIC can cause significant cascading effects. If any privilege related to a DML operation is revoked from PUBLIC (for example, SELECT ANY TABLE, UPDATE ON emp), all procedures in the database, including functions and packages, must be reauthorized before they can be used again. Therefore, exercise caution when granting DML-related privileges to PUBLIC.
See Also: For more information about object dependencies, see "Managing Object Dependencies".
Depending on what is granted or revoked, a grant or revoke takes effect at different times:
This section describes aspects of granting roles via your operating system or network, and includes the following topics:
Instead of a security administrator explicitly granting and revoking database roles to and from users using GRANT and REVOKE statements, the operating system that operates Oracle can grant roles to users at connect time. Roles can be administered using the operating system and passed to Oracle when a user creates a session. As part of this mechanism, each user's default roles and the roles granted to a user with the ADMIN OPTION can be identified. Even if the operating system is used to authorize users for roles, all roles must be created in the database and privileges assigned to the role with GRANT statements.
Roles can also be granted through a network service. For information about network roles, see Oracle8 Distributed Database Systems.
The advantage of using the operating system to identify a user's database roles is that privilege management for an Oracle database can be externalized. The security facilities offered by the operating system control a user's privileges. This option may offer advantages of centralizing security for a number of system activities. For example, MVS Oracle administrators may want RACF groups to identify a database user's roles, UNIX Oracle administrators may want UNIX groups to identify a database user's roles, or VMS Oracle administrators may want to use rights identifiers to identify a database user's roles.
The main disadvantage of using the operating system to identify a user's database roles is that privilege management can only be performed at the role level. Individual privileges cannot be granted using the operating system, but can still be granted inside the database using GRANT statements.
A secondary disadvantage of using this feature is that by default users cannot connect to the database through the multi-threaded server, or any other network connection, if the operating system is managing roles. However, you can change this default; see "Using Network Connections with Operating System Role Management".
See Also: The features described in this section are available only on some operating systems. This information is operating system-dependent; see your operating system-specific Oracle documentation.
To operate a database so that it uses the operating system to identify each user's database roles when a session is created, set the initialization parameter OS_ROLES to TRUE (and restart the instance, if it is currently running). When a user attempts to create a session with the database, Oracle initializes the user's security domain using the database roles identified by the operating system.
To identify database roles for a user, each Oracle user's operating system account must have operating system identifiers (these may be called groups, rights identifiers, or other similar names) that indicate which database roles are to be available for the user. Role specification can also indicate which roles are the default roles of a user and which roles are available with the ADMIN OPTION. No matter which operating system is used, the role specification at the operating system level follows the format:
ORA_<ID>_<ROLE>[_[D][A]] where: ID
The definition of ID varies on different operating systems. For example, on VMS, ID is the instance identifier of the database; on MVS, it is the machine type; on UNIX, it is the system ID.
This optional character indicates that this role is to be a default role of the database user.
This optional character indicates that this role is to be granted to the user with the ADMIN OPTION. This allows the user to grant the role to other roles only. (Roles cannot be granted to users if the operating system is used to manage roles.)
For example, an operating system account might have the following roles identified in its profile:
ORA_PAYROLL_ROLE1 ORA_PAYROLL_ROLE2_A ORA_PAYROLL_ROLE3_D ORA_PAYROLL_ROLE4_DA
When the corresponding user connects to the PAYROLL instance of Oracle, ROLE3 and ROLE4 are defaults, while ROLE2 and ROLE4 are available with the ADMIN OPTION.
When you use operating system managed roles, it is important to note that database roles are being granted to an operating system user. Any database user to which the OS user is able to connect will have the authorized database roles enabled. For this reason, you should consider defining all Oracle users as IDENTIFIED EXTERNALLY if you are using OS_ROLES = TRUE, so that the database accounts are tied to the OS account that was granted privileges.
If OS_ROLES is set to TRUE, the operating system completely manages the grants and revokes of roles to users. Any previous grants of roles to users via GRANT statements do not apply; however, they are still listed in the data dictionary. Only the role grants made at the operating system level to users apply. Users can still grant privileges to roles and users.
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Note: If the operating system grants a role to a user with the ADMIN OPTION, the user can grant the role only to other roles. |
If OS_ROLES is set to TRUE, any role granted by the operating system can be dynamically enabled using the SET ROLE command. If the role was defined to require a password or operating system authorization, that still applies. However, any role not identified in a user's operating system account cannot be specified in a SET ROLE statement, even if a role has been granted using a GRANT statement when OS_ROLES = FALSE. (If you specify such a role, Oracle ignores it.)
When OS_ROLES = TRUE, a user can enable as many roles as specified by the parameter MAX_ENABLED_ROLES.
If you want to have the operating system manage roles, by default users cannot connect to the database through the multi-threaded server. This restriction is the default because a remote user could impersonate another operating system user over a non-secure connection.
If you are not concerned with this security risk and want to use operating system role management with the multi-threaded server, or any other network connection, set the parameter REMOTE_OS_ROLES in the database's parameter file to TRUE. The change will take effect the next time you start the instance and mount the database. (The parameter is FALSE by default.)
To list the grants made for objects, a user can query the following data dictionary views:
See Also: See the Oracle8 Reference for a detailed description of these data dictionary views.
For the following examples, assume the following statements are issued:
CREATE ROLE security_admin IDENTIFIED BY honcho; GRANT create profile, alter profile, drop profile, create role, drop any role, grant any role, audit any, audit system, create user, become user, alter user, drop user TO security_admin WITH ADMIN OPTION; GRANT SELECT, DELETE ON sys.aud$ TO security_admin; GRANT security_admin, create session TO swilliams; GRANT security_admin TO system_administrator; GRANT create session TO jward; GRANT SELECT, DELETE ON emp TO jward; GRANT INSERT (ename, job) ON emp TO swilliams, jward;
The following query indicates all system privilege grants made to roles and users:
SELECT * FROM sys.dba_sys_privs;
GRANTEE PRIVILEGE ADM -------------- --------------------------------- --- SECURITY_ADMIN ALTER PROFILE YES SECURITY_ADMIN ALTER USER YES SECURITY_ADMIN AUDIT ANY YES SECURITY_ADMIN AUDIT SYSTEM YES SECURITY_ADMIN BECOME USER YES SECURITY_ADMIN CREATE PROFILE YES SECURITY_ADMIN CREATE ROLE YES SECURITY_ADMIN CREATE USER YES SECURITY_ADMIN DROP ANY ROLE YES SECURITY_ADMIN DROP PROFILE YES SECURITY_ADMIN DROP USER YES SECURITY_ADMIN GRANT ANY ROLE YES SWILLIAMS CREATE SESSION NO JWARD CREATE SESSION NO
The following query returns all the roles granted to users and other roles:
SELECT * FROM sys.dba_role_privs;
GRANTEE GRANTED_ROLE ADM ------------------ ------------------------------------ --- SWILLIAMS SECURITY_ADMIN NO
The following query returns all object privileges (not including column specific privileges) granted to the specified user:
SELECT table_name, privilege, grantable FROM sys.dba_tab_privs WHERE grantee = 'JWARD';
TABLE_NAME PRIVILEGE GRANTABLE ----------- ------------ ---------- EMP SELECT NO EMP DELETE NO
To list all the column specific privileges that have been granted, use the following query:
SELECT grantee, table_name, column_name, privilege FROM sys.dba_col_privs;
GRANTEE TABLE_NAME COLUMN_NAME PRIVILEGE ----------- ------------ ------------- -------------- SWILLIAMS EMP ENAME INSERT SWILLIAMS EMP JOB INSERT JWARD EMP NAME INSERT JWARD EMP JOB INSERT
The following query lists all roles currently enabled for the issuer:
SELECT * FROM session_roles;
If SWILLIAMS has enabled the SECURITY_ADMIN role and issues this query, Oracle returns the following information:
ROLE ------------------------------ SECURITY_ADMIN
The following query lists all system privileges currently available in the issuer's security domain, both from explicit privilege grants and from enabled roles:
SELECT * FROM session_privs;
If SWILLIAMS has the SECURITY_ADMIN role enabled and issues this query, Oracle returns the following results:
PRIVILEGE ---------------------------------------- AUDIT SYSTEM CREATE SESSION CREATE USER BECOME USER ALTER USER DROP USER CREATE ROLE DROP ANY ROLE GRANT ANY ROLE AUDIT ANY CREATE PROFILE ALTER PROFILE DROP PROFILE
If the SECURITY_ADMIN role is disabled for SWILLIAMS, the first query would have returned no rows, while the second query would only return a row for the CREATE SESSION privilege grant.
The DBA_ROLES data dictionary view can be used to list all roles of a database and the authentication used for each role. For example, the following query lists all the roles in the database:
SELECT * FROM sys.dba_roles;
ROLE PASSWORD ---------------- -------- CONNECT NO RESOURCE NO DBA NO SECURITY_ADMIN YES
The ROLE_ROLE_PRIVS, ROLE_SYS_PRIVS, and ROLE_TAB_PRIVS data dictionary views contain information on the privilege domains of roles.
For example, the following query lists all the roles granted to the SYSTEM_ADMIN role:
SELECT granted_role, admin_option FROM role_role_privs WHERE role = 'SYSTEM_ADMIN'; GRANTED_ROLE ADM ---------------- ---- SECURITY_ADMIN NO
The following query lists all the system privileges granted to the SECURITY_ADMIN role:
SELECT * FROM role_sys_privs WHERE role = 'SECURITY_ADMIN';
ROLE PRIVILEGE ADM ----------------------- ----------------------------- --- SECURITY_ADMIN ALTER PROFILE YES SECURITY_ADMIN ALTER USER YES SECURITY_ADMIN AUDIT ANY YES SECURITY_ADMIN AUDIT SYSTEM YES SECURITY_ADMIN BECOME USER YES SECURITY_ADMIN CREATE PROFILE YES SECURITY_ADMIN CREATE ROLE YES SECURITY_ADMIN CREATE USER YES SECURITY_ADMIN DROP ANY ROLE YES SECURITY_ADMIN DROP PROFILE YES SECURITY_ADMIN DROP USER YES SECURITY_ADMIN GRANT ANY ROLE YES
The following query lists all the object privileges granted to the SECURITY_ADMIN role:
SELECT table_name, privilege FROM role_tab_privs WHERE role = 'SECURITY_ADMIN';
TABLE_NAME PRIVILEGE --------------------------- ---------------- AUD$ DELETE AUD$ SELECT
