SSHd的认证方式改为pam_mysql产生的问题，在线等待求解

Question

因为某些需求，想把ssh的用户认证从系统用户改为通过某个mysql的数据表进行认证。随后进行下列动作：
1.下载pam_mysql，make，cp pam_mysql.so /lib/security/.
2.修改/etc/pam.d/sshd文件如下：
#%PAM-1.0
auth       required     pam_mysql.so user=test passwd=123456 host=192.168.210.2 db=users table=users usercolumn=username passwdcolumn=password crypt=0 sqllog=0
word crypt=0 sqllog=0
account    required     pam_mysql.so user=test passwd=123456 host=192.168.210.2 db=users table=users usercolumn=username passwdcolumn=password crypt=0 sqllog=0
#auth       sufficient     pam_stack.so service=system-auth
auth       sufficient   pam_unix_auth.so
#account    sufficient     pam_stack.so service=system-auth
account    sufficient   pam_unix_acct.so
auth       required     pam_nologin.so
password   required     pam_stack.so service=system-auth
session    required     pam_stack.so service=system-auth
session    required     pam_limits.so
session    optional     pam_console.so
3.打开mysql并建立数据库users和表users，执行
GRANT ALL ON users.* TO mysql@"%" IDENTIFIED bY "123456";  
insert into users values(NULL,'tester','123456');
4.此时用ssh client连接server，使用用户tester，密码123456，无法登陆
5.查看log，log显示：
Mar 17 13:55:23 game sshd[2567]: Illegal user tester from 192.168.1.92
Mar 17 13:55:26 game sshd[2567]: pam_sm_authenticate called.
Mar 17 13:55:26 game sshd[2567]: dbuser changed.
Mar 17 13:55:26 game sshd[2567]: dbpasswd changed.
Mar 17 13:55:26 game sshd[2567]: host changed.
Mar 17 13:55:26 game sshd[2567]: database changed.
Mar 17 13:55:26 game sshd[2567]: table changed.
Mar 17 13:55:26 game sshd[2567]: usercolumn changed.
Mar 17 13:55:26 game sshd[2567]: passwdcolumn changed.
Mar 17 13:55:26 game sshd[2567]: crypt changed.
Mar 17 13:55:26 game sshd[2567]: sqllog changed.
Mar 17 13:55:26 game sshd[2567]: db_connect  called.
Mar 17 13:55:26 game sshd[2567]: returning 0 .
Mar 17 13:55:26 game sshd[2567]: db_checkpasswd called.
Mar 17 13:55:26 game sshd[2567]: pam_mysql: where clause =
Mar 17 13:55:26 game sshd[2567]: SELECT password FROM cts_players WHERE login_id='NOUSER'
Mar 17 13:55:26 game sshd[2567]: pam_mysql: select returned more than one result
Mar 17 13:55:26 game sshd[2567]: returning 7 after db_checkpasswd.
Mar 17 13:55:28 game sshd[2567]: Failed password for illegal user tester from 192.168.1.92 port 1599 ssh2
6.如果在系统用户中添加tester用户之后，pam_mysql的验证能够通过

哪位老大能帮忙解释一下，为什么pam_mysql认证的用户一定要是一个系统用户而不能仅仅是mysql的users里面的一条数据呢？

Answer 1

自己定一下！急