南通考试院:如何使用触发器实现数据库级守护,防止DDL操作

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如何使用触发器实现数据库级守护,防止DDL操作

--对于重要对象,实施DDL拒绝,防止create,drop,truncate,alter等重要操作

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不管是有意还是无意的,你可能会遇到数据库中重要的数据表等对象被drop掉的情况,这可能会给我们带来巨大的损失.

通过触发器,我们可以实现对于表等对象的数据库级守护,禁止用户drop操作.

以下是一个简单的范例,供参考:

REM this script can be used to monitor a objectREM deny any drop operation on it.CREATE OR REPLACE TRIGGER trg_dropdeny   BEFORE DROP ON DATABASEBEGIN   IF LOWER (ora_dict_obj_name ()) = 'test'   THEN      raise_application_error (num      => -20000,                               msg      =>    '你疯了,想删除表 '                                           || ora_dict_obj_name ()                                           || ' ?!!!!!'                                           || '你完了,警察已在途中.....'                              );   END IF;END;/                        

测试效果:

SQL> connect scott/tigerConnected.SQL> create table test as select * from dba_users;Table created.SQL> connect / as sysdbaConnected.SQL> create or replace trigger trg_dropdeny  2     before drop on database     3  begin  4        if lower(ora_dict_obj_name()) = 'test'          5        then  6        raise_application_error(  7           num => -20000,  8           msg => '你疯了,想删除表 ' || ora_dict_obj_name() || ' ?!!!!!' ||'你完了,警察已在途中.....');  9        end if; 10     end; 11  /Trigger created.SQL> connect scott/tigerConnected.SQL> drop table test;drop table test*ERROR at line 1:ORA-00604: error occurred at recursive SQL level 1ORA-20000: 你疯了,想删除表 TEST ?!!!!!你完了,警察已在途中.....ORA-06512: at line 4  

Oracle从Oracle8i开始,允许实施DDL事件trigger,可是实现对于DDL的监视及控制,以下是一个进一步的例子:

create or replace trigger ddl_denybefore create or alter or drop or truncate on databasedeclare  l_errmsg varchar2(100):= 'You have no permission to this operation';begin  if ora_sysevent = 'CREATE' then     raise_application_error(-20001, ora_dict_obj_owner || '.' || ora_dict_obj_name || ' ' || l_errmsg);  elsif ora_sysevent = 'ALTER' then    raise_application_error(-20001, ora_dict_obj_owner || '.' || ora_dict_obj_name || ' ' || l_errmsg);  elsif ora_sysevent = 'DROP' then    raise_application_error(-20001, ora_dict_obj_owner || '.' || ora_dict_obj_name || ' ' || l_errmsg);  elsif ora_sysevent = 'TRUNCATE' then    raise_application_error(-20001, ora_dict_obj_owner || '.' || ora_dict_obj_name || ' ' || l_errmsg);  end if;exception  when no_data_found then    null;end;/                      

我们看一下效果:

[oracle@jumper tools]$ sqlplus "/ as sysdba"

SQL*Plus: Release 9.2.0.4.0 - Production on Sun Oct 31 11:38:25 2004

Copyright (c) 1982, 2002, Oracle Corporation. All rights reserved.

Connected to:
Oracle9i Enterprise Edition Release 9.2.0.4.0 - Production
With the Partitioning option
JServer Release 9.2.0.4.0 - Production

SQL> set echo on
SQL> @ddlt
SQL> create or replace trigger ddl_deny
2 before create or alter or drop or truncate on database
3 declare
4 l_errmsg varchar2(100):= 'You have no permission to this operation';
5 begin
6 if ora_sysevent = 'CREATE' then
7 raise_application_error(-20001, ora_dict_obj_owner || '.' || ora_dict_obj_name || ' ' || l_errmsg);
8 elsif ora_sysevent = 'ALTER' then
9 raise_application_error(-20001, ora_dict_obj_owner || '.' || ora_dict_obj_name || ' ' || l_errmsg);
10 elsif ora_sysevent = 'DROP' then
11 raise_application_error(-20001, ora_dict_obj_owner || '.' || ora_dict_obj_name || ' ' || l_errmsg);
12 elsif ora_sysevent = 'TRUNCATE' then
13 raise_application_error(-20001, ora_dict_obj_owner || '.' || ora_dict_obj_name || ' ' || l_errmsg);
14 end if;
15
16 exception
17 when no_data_found then
18 null;
19 end;
20 /

Trigger created.

SQL>
SQL>
SQL> connect scott/tiger
Connected.
SQL> create table t as select * from test;
create table t as select * from test
*
ERROR at line 1:
ORA-00604: error occurred at recursive SQL level 1
ORA-20001: SCOTT.T You have no permission to this operation
ORA-06512: at line 5

SQL> alter table test add (id number);
alter table test add (id number)
*
ERROR at line 1:
ORA-00604: error occurred at recursive SQL level 1
ORA-20001: SCOTT.TEST You have no permission to this operation
ORA-06512: at line 7

SQL> drop table test;
drop table test
*
ERROR at line 1:
ORA-00604: error occurred at recursive SQL level 1
ORA-20001: SCOTT.TEST You have no permission to this operation
ORA-06512: at line 9

SQL> truncate table test;
truncate table test
*
ERROR at line 1:
ORA-00604: error occurred at recursive SQL level 1
ORA-20001: SCOTT.TEST You have no permission to this operation
ORA-06512: at line 11

                         

我们可以看到,ddl语句都被禁止了,如果你不是禁止,可以选择把执行这些操作的用户及时间记录到另外的临时表中.以备查询.