Definer and Invoker Rights(转)

在Oracle8i以前，所有已编译存储对象(包括packages, procedures, functions, triggers, and views)只能以定义者(Definer)身份解析运行；从Oracle8i开始，Oracle引入调用者(invoker)权限，使得对象可以以调用者身份和权限执行。

定义者(Definer)指编译存储对象的所有者.
调用者(Invoker)指拥有当前会话权限的模式，这可能和当前登录用户相同或不同(alter session set current_schema 可以改变调用者Schema).

TOM在他的《Expert One on One》的第23章曾经详细介绍这一特性，本文引用Tom的一个例子用于说明Definer and Invoker权限。

1.以Eygle用户(definer)创建2个过程

 $ sqlplus eygle/eygle

SQL*Plus: Release 9.2.0.4.0 - Production on Sun Dec 11 11:39:27 2005

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

Connected to:
Oracle9i Enterprise Edition Release 9.2.0.4.0 - 64bit Production
With the Partitioning option
JServer Release 9.2.0.4.0 - Production

SQL> create or replace procedure definer_proc
  2  as
  3  begin
  4      for x in
  5      ( select sys_context( 'userenv', 'current_user' ) current_user,
  6               sys_context( 'userenv', 'session_user' ) session_user,
  7               sys_context( 'userenv', 'current_schema' ) current_schema
  8          from dual )
  9      loop
 10          dbms_output.put_line( 'Current User:   ' || x.current_user );
 11          dbms_output.put_line( 'Session User:   ' || x.session_user );
 12          dbms_output.put_line( 'Current Schema: ' || x.current_schema );
 13      end loop;
 14  end;
 15  /

Procedure created.

SQL> 
SQL> grant execute on definer_proc to test;

Grant succeeded.

SQL> 
SQL> create or replace procedure invoker_proc
  2  AUTHID CURRENT_USER
  3  as
  4  begin
  5      for x in
  6      ( select sys_context( 'userenv', 'current_user' ) current_user,
  7               sys_context( 'userenv', 'session_user' ) session_user,
  8               sys_context( 'userenv', 'current_schema' ) current_schema
  9          from dual )
 10      loop
 11          dbms_output.put_line( 'Current User:   ' || x.current_user );
 12          dbms_output.put_line( 'Session User:   ' || x.session_user );
 13          dbms_output.put_line( 'Current Schema: ' || x.current_schema );
 14      end loop;
 15  end;
 16  /

Procedure created.

SQL> 
SQL> grant execute on invoker_proc to test;

Grant succeeded.

注意invoker权限的本质是引入了AUTHID CURRENT_USER子句，通过此句Oracle得以使用invoker身份编译执行对象。

2.以test用户(invoker)身份执行

SQL> connect test/test
Connected.
SQL> 
SQL> set serveroutput on
SQL> exec eygle.definer_proc
Current User:   EYGLE
Session User:   TEST
Current Schema: EYGLE

PL/SQL procedure successfully completed.

SQL> exec eygle.invoker_proc
Current User:   TEST
Session User:   TEST
Current Schema: TEST

PL/SQL procedure successfully completed.

注意只有使用invoker者权限执行时，Schema才转换为TEST.

SQL> alter session set current_schema = system;

Session altered.

SQL> exec eygle.definer_proc
Current User:   EYGLE
Session User:   TEST
Current Schema: EYGLE

PL/SQL procedure successfully completed.

SQL> exec eygle.invoker_proc
Current User:   TEST
Session User:   TEST
Current Schema: SYSTEM

PL/SQL procedure successfully completed.

SQL> 

通过alter session set current_schema方式修改当前模式之后，我们看到仍然是仅当使用invoker权限执行时，Schmea方切换为SYSTEM.