监听器也有安全？Sure！在缺省的情况下，任意用户不需要使用任何密码即通过lsnrctl 工具对Oracle Listener进行操作或关闭，从
而造成任意新的会话都将无法建立连接。在Oracle 9i 中Oracle监听器允许任何一个人利用lsnrctl从远程发起对监听器的管理。也容易导致数
据库受到损坏。
1. 未设定密码情形下停止监听
[oracle@test ~]$ lsnrctl stop listener_demo92 -->停止监听，可以看出不需要任何密码即可停止
LSNRCTL for Linux: Version 9.2.0.8.0 - Production on 26-JUN-2011 08:22:26
Copyright (c) 1991, 2006, Oracle Corporation. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=test)(PORT=1521)))
The command completed successfully
2.重新启动监听并设置密码
[oracle@test ~]$ lsnrctl
LSNRCTL for Linux: Version 9.2.0.8.0 - Production on 26-JUN-2011 08:24:09
Copyright (c) 1991, 2006, Oracle Corporation. All rights reserved.
Welcome to LSNRCTL, type "help" for information.
LSNRCTL> set current_listener listener_demo92 -->设置当前监听器
Current Listener is listener_demo92
LSNRCTL> start -->启动过程也不需要任何密码,启动的详细信息省略
LSNRCTL> change_password -->使用change_password来设置密码
Old password:
New password:
Reenter new password:
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=test)(PORT=1521)))
Password changed for listener_demo92
The command completed successfully
LSNRCTL> save_config -->注意此处的save_config失败
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=test)(PORT=1521)))
TNS-01169: The listener has not recognized the password
LSNRCTL> set password -->输入新设定的密码验证
Password:
The command completed successfully
LSNRCTL> save_config -->再次save_config成功
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=test)(PORT=1521)))
Saved listener_demo92 configuration parameters.
Listener Parameter File /oracle/92/network/admin/listener.ora
Old Parameter File /oracle/92/network/admin/listener.bak
The command completed successfully
-->增加密码之后可以看到listener.ora文件中有一条新增的记录，即密码选项(注：尽管使用了密码管理方式,仍然可以无需密码启动监听)
[oracle@test admin]$ more listener.ora
#----ADDED BY TNSLSNR 26-JUN-2011 05:12:48---
PASSWORDS_listener_demo92 =
#--------------------------------------------
3. 尝试未使用密码的情况下停止监听
[oracle@test ~]$ lsnrctl stop listener_demo92
LSNRCTL for Linux: Version 9.2.0.8.0 - Production on 26-JUN-2011 06:09:51
Copyright (c) 1991, 2006, Oracle Corporation. All rights reserved.
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=test)(PORT=1521)))
TNS-01169: The listener has not recognized the password -->收到错误信息，需要使用密码认证
4.使用密码来停止监听
[oracle@test ~]$ lsnrctl
LSNRCTL> set current_listener listener_demo92
Current Listener is listener_demo92
LSNRCTL> stop
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=test)(PORT=1521)))
TNS-01169: The listener has not recognized the password
LSNRCTL> set password
Password:
The command completed successfully
LSNRCTL> stop
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=test)(PORT=1521)))
The command completed successfully
LSNRCTL> status
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=test)(PORT=1521)))
TNS-12541: TNS:no listener
TNS-12560: TNS:protocol adapter error
TNS-00511: No listener
Linux Error: 111: Connection refused
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=IPC)(KEY=EXTPROC)))
TNS-12541: TNS:no listener
TNS-12560: TNS:protocol adapter error
TNS-00511: No listener
Linux Error: 2: No such file or directory
5. save_config失败的问题
-->在 Oracle 9i中，使用save_config命令将会失败
LSNRCTL> save_config
Connecting to (DESCRIPTION=(ADDRESS=(PROTOCOL=TCP)(HOST=
TNS-01169: The listener has not recognized the password
-->应该先使用set password之后再save_config，则保存配置成功。
LSNRCTL> set password
Password:
The command completed successfully
/*在Oracle 10g 中不会出现类似的问题，因为在10g中可以使用基于操作系统验证方式。listener将检测到如果用户属于dba组的成员，
将会被授予改变密码，保存配置以及停止监听等权限。 */
6. 配置listener.ora中ADMIN_RESTRICTIONS参数
参数作用：
当在listener.ora文件中设置了ADMIN_RESTRICTIONS参数后，在监听器运行时，不允许执行任何管理任何，同时set命令将不可用
，不论是在服务器本地还是从远程执行都不行。此时对于监听的设置仅仅通过手工修改listener.ora文件，要使修改生效，只能
使用lsnrctl reload命令或lsnrctl stop/start命令重新载入一次监听器配置信息。
修改方法：
在listener.ora文件中手动加入下面这样一行
ADMIN_RESTRICTIONS_<监听器名> = ON