问题

1. 在CentOS/RHEL上，Active Directory 用户使用 SSSD 通过 SSH 登录时，报错：

"Permission Denied, Please Try Again"
“权限被拒绝，请重试”：

# ssh [hostname] -l [username]@[DOMAINNAME].com
The authenticity of host '[hostname] ([IP ADDRESS])' can't be established.
RSA key fingerprint is 4f:3b:ba:b2:b7:6e:d0:b7:dd:a6:4b:32:ac:e3:58:63.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '[hostname],[IP ADDRESS]' (RSA) to the list of known hosts.
[username]<@DOMAINNAME>.com@[hostname]'s password:
Permission denied, please try again.
[username]<@DOMAINNAME>.com@[hostname]'s password:

2. 验证用户名和密码是否正确：

$ su - [username]
# su - [username]@[DOMAINNAME].com

3. 在/var/log/secure历史记录中可以看到认证失败：

Apr 3 23:20:24 [hostname] sshd[323944]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=ittwhxh1n62.na.admworld.com user=[username]
Apr 3 23:20:24 [hostname] sshd[323944]: pam_tally2(sshd:auth): user [username] (1494516080) tally 11, deny 5 <<<<<<<<<<<<<
Apr 3 23:20:26 [hostname] sshd[323944]: Failed password for [username] from [IP ADDRESS] port 51803 ssh2
Apr 3 23:20:34 [hostname] sshd[323944]: pam_tally2(sshd:auth): user [username] (1494516080) tally 12, deny 5 <<<<<<<<<<<<<
Apr 3 23:20:37 [hostname] sshd[323944]: Failed password for [username] from [IP ADDRESS] port 51803 ssh2
Apr 3 23:20:40 [hostname] sshd[323944]: PAM 1 more authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=ittwhxh1n62.na.admworld.com user=[username]
Apr 3 23:24:37 [hostname] sshd[338364]: pam_unix(sshd:auth): authentication failure; logname= uid=0 euid=0 tty=ssh ruser= rhost=ittwhxh1n62.na.admworld.com user=[username]
Apr 3 23:24:37 [hostname] sshd[338364]: pam_tally2(sshd:auth): user [username] (1494516080) tally 13, deny 5 <<<<<<<<<<<<<
Apr 3 23:24:39 [hostname] sshd[338364]: Failed password for [username] from [IP ADDRESS] port 51893 ssh2

根本原因

一个或者多个配置文件的问题： system-auth-ac 和 password-auth-ac ，sssd 模块在下面的配置文件中被注释：

$ grep sss /etc/pam.d/system-auth-ac 
# auth sufficient pam_sss.so use_first_pass
# account [default=bad success=ok user_unknown=ignore] pam_sss.so
# password sufficient pam_sss.so use_authtok
# session optional pam_sss.so

$  grep sss /etc/pam.d/password-auth-ac 
# auth sufficient pam_sss.so use_first_pass
# account [default=bad success=ok user_unknown=ignore] pam_sss.so
# password sufficient pam_sss.so use_authtok
# session optional pam_sss.so

pam_tally2 模块与 sssd 模块冲突：

$ cat etc/pam.d/sshd
#%PAM-1.0
auth required pam_sepermit.so
auth include password-auth
##auth required pam_tally2.so deny=5 onerr=fail serialize >>>>
#auth required pam_tally2.so deny=5 onerr=fail lock_time=600 serialize
# EXADATA ACCESS CONTROL via /etc/exadata/security/exadata-access.conf
account required pam_nologin.so
account include password-auth
account required pam_tally2.so
password include password-auth
pam_selinux.so close should be the first session rule
session required pam_selinux.so close
session required pam_loginuid.so
pam_selinux.so open should only be followed by sessions to be executed in the user context
session required pam_selinux.so open env_params
session required pam_namespace.so
session optional pam_keyinit.so force revoke
session include password-auth
session required pam_limits.so

# cat /etc/pam.d/login
auth required pam_tally2.so deny=5 onerr=fail serialize

# cat/etc/pam.d/login
account required pam_tally2.so

解决方案

注意：当心删除 /pam.d/ 目录下的所有备份文件。

1. 在 /etc/pam.d/* 目录下的所有身份验证文件中注释 pam_tally2 行。

2. 注释掉原因部分中提到的行，[启用 sssd 模块] 如下。

$ grep sss /etc/pam.d/system-auth-ac 
auth sufficient pam_sss.so use_first_pass
account [default=bad success=ok user_unknown=ignore] pam_sss.so
password sufficient pam_sss.so use_authtok
session optional pam_sss.so

$ grep sss /etc/pam.d/password-auth-ac
auth sufficient pam_sss.so use_first_pass
account [default=bad success=ok user_unknown=ignore] pam_sss.so
password sufficient pam_sss.so use_authtok
session optional pam_sss.so