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本实验包含了：

• 简单的Oracle Redaction演示
• 针对指定用户的Redaction

实验环境

假设有一个19c多租户数据库，PDB名为orclpdb1。

我们将在orclpdb1中建立2个用户：

• redact_user: redact管理员
• schema_user: schema用户

基础实验

首先进入数据库orclpdb1，创建用户redact_user：

alter session set container=orclpdb1;
create user redact_user identified by oracle;
grant connect, resource, unlimited tablespace to redact_user;
grant select on Sys.redaction_policies to redact_user;
grant select on Sys.redaction_columns to redact_user;
grant execute on dbms_redact to redact_user;

然后再创建一个普通用户schema_user：

alter session set container=orclpdb1;
create user schema_user identified by oracle;
grant connect, resource, unlimited tablespace to schema_user;

以schema_user用户登录，并创建表和插入数据：

connect schema_user/oracle@orclpdb1
CREATE TABLE "EMPLOYEES" ("EMPLOYEE_ID" NUMBER(6,0), "FIRST_NAME" VARCHAR2(20), "LAST_NAME" VARCHAR2(25), "SOCIAL_SECURITY" VARCHAR2(11), "SALARY" NUMBER(4,0));
insert into EMPLOYEES (EMPLOYEE_ID,FIRST_NAME,LAST_NAME,SOCIAL_SECURITY,SALARY) values (100,'Steven','King','247-85-9056',7000);
insert into EMPLOYEES (EMPLOYEE_ID,FIRST_NAME,LAST_NAME,SOCIAL_SECURITY,SALARY) values (101,'Neena','Kochhar','334-08-6578',5000);
commit;

以redact_user登入，定义redact策略：

connect redact_user/oracle@orclpdb1BEGIN
DBMS_REDACT.ADD_POLICY (object_schema          => 'SCHEMA_USER',object_name            => 'EMPLOYEES',policy_name            => 'redact_policy',column_name            => 'SOCIAL_SECURITY',function_type          => DBMS_REDACT.RANDOM,expression             => '1=1',enable                 => TRUE);
END;
/

注意，此时redact_user对于schema_user中的表是没有读取权限的：

SQL> show user
USER is "REDACT_USER"
SQL> select * from schema_user.employees;
select * from schema_user.employees*
ERROR at line 1:
ORA-00942: table or view does not exist

此时schema_user查看SOCIAL_SECURITY列，策略生效：

SQL> connect schema_user/oracle@orclpdb1
Connected.
SQL> select social_security from employees;SOCIAL_SECU
-----------
z8e.SQ<Y#@m
qP/uDj(&yX7

赋予redact_user对表的读取权限：

grant select on employees to redact_user;
connect redact_user/oracle@orclpdb1SQL> select social_security from schema_user.employees;SOCIAL_SECU
-----------
Q*NCEmtLY2V
E,8FG0#gM4@

可以看到，目前redact策略对redact_user也是生效的。

扩展实验

在此实验中，我们将实现选择性的redaction。即redact policy仅对schema_user生效。

这时通过redact expresion实现的。

查看DBMS_REDACT的帮助。其语法为：

DBMS_REDACT.ADD_POLICY (object_schema                IN    VARCHAR2 := NULL,object_name                  IN    VARCHAR2,policy_name                  IN    VARCHAR2,column_name                  IN    VARCHAR2 := NULL,function_type                IN    BINARY_INTEGER := DBMS_REDACT.FULL,function_parameters          IN    VARCHAR2 := NULL,expression                   IN    VARCHAR2,enable                       IN    BOOLEAN := TRUE,regexp_pattern               IN    VARCHAR2 := NULL,regexp_replace_string        IN    VARCHAR2 := NULL,regexp_position              IN    BINARY_INTEGER := 1,regexp_occurrence            IN    BINARY_INTEGER := 0,regexp_match_parameter       IN    VARCHAR2 := NULL,policy_description           IN    VARCHAR2 := NULL,column_description           IN    VARCHAR2 := NULL);

其expression参数的作用为：

Default boolean expression for the table or view. If this expression is used, then redaction takes place only if this policy expression evaluates to TRUE.

现在要做的就是修改策略：

connect redact_user/oracle@orclpdb1BEGIN
DBMS_REDACT.ALTER_POLICY (object_schema          => 'SCHEMA_USER',object_name            => 'EMPLOYEES',policy_name            => 'redact_policy',column_name            => 'SOCIAL_SECURITY',action                 => DBMS_REDACT.MODIFY_EXPRESSION,expression             => 'SYS_CONTEXT ( ''USERENV'',''SESSION_USER'' ) =''SCHEMA_USER'''
);
END;
/

现在不同的用户查看的结果就不一样了：

SQL> connect redact_user/oracle@orclpdb1
Connected.
SQL> select social_security from schema_user.employees;SOCIAL_SECU
-----------
247-85-9056
334-08-6578SQL> connect schema_user/oracle@orclpdb1
Connected.
SQL> select social_security from schema_user.employees;SOCIAL_SECU
-----------
9NbODS\?AVj
PAOj4FtYXIW

清理

connect redact_user/oracle@orclpdb1BEGIN
DBMS_REDACT.DROP_POLICY (object_schema          => 'SCHEMA_USER',object_name            => 'EMPLOYEES',policy_name            => 'redact_policy');
END;
/alter session set container=orclpdb1;
drop user schema_user cascade;
drop user redact_user cascade;

Redaction 策略是否可以复用

再来回顾下ADD_POLICY过程的参数：

```sql
DBMS_REDACT.ADD_POLICY (object_schema                IN    VARCHAR2 := NULL,object_name                  IN    VARCHAR2,policy_name                  IN    VARCHAR2,column_name                  IN    VARCHAR2 := NULL,function_type                IN    BINARY_INTEGER := DBMS_REDACT.FULL,function_parameters          IN    VARCHAR2 := NULL,expression                   IN    VARCHAR2,enable                       IN    BOOLEAN := TRUE,regexp_pattern               IN    VARCHAR2 := NULL,regexp_replace_string        IN    VARCHAR2 := NULL,regexp_position              IN    BINARY_INTEGER := 1,regexp_occurrence            IN    BINARY_INTEGER := 0,regexp_match_parameter       IN    VARCHAR2 := NULL,policy_description           IN    VARCHAR2 := NULL,column_description           IN    VARCHAR2 := NULL);

可以看到，由于参数的粒度比较细，唯一可以的是expression，其作用为：

表或视图的默认布尔表达式。 如果使用此表达式，则仅当此策略表达式的计算结果为 TRUE 时才会发生编辑。

如果真的需要有2列，其策略完全一样，基于以上过程再封装也比较简单。

参考

• Redaction Management in Oracle SQL Developer