Linux 安全配置杂文

SSH 配置

vim /etc/ssh/sshd_config <<VIM > /dev/null 2>&1

:s/#LoginGraceTime 2m/LoginGraceTime 2m/

:s/#PermitRootLogin yes/PermitRootLogin no/

:s/#MaxAuthTries 6/MaxAuthTries 3/

:%s$#AuthorizedKeysFile$AuthorizedKeysFile /dev/null$

:%s/GSSAPIAuthentication yes/GSSAPIAuthentication no/

:%s/GSSAPICleanupCredentials yes/GSSAPICleanupCredentials no/

:wq

VIM

禁止证书登陆 AuthorizedKeysFile /dev/null

http://netkiller.github.com/

锁定用户禁止登陆

passwd -l bin

passwd -l daemon

passwd -l adm

passwd -l lp

passwd -l sync

passwd -l shutdown

passwd -l halt

passwd -l mail

passwd -l uucp

passwd -l operator

passwd -l games

passwd -l gopher

passwd -l ftp

passwd -l nobody

passwd -l vcsa

passwd -l saslauth

passwd -l postfix

检查可以登陆的用户与有密码的用户

Java代码  

1. #!/bin/bash  
2.   
3. function section(){  
4.     local title=$1  
5.     echo "=================================================="  
6.     echo " $title "  
7.     echo "=================================================="  
8. }  
9.   
10. section "Check login user"  
11. grep -v nologin /etc/passwd  
12.   
13. section "Check login password"  
14. grep '\$' /etc/shadow  
15.   
16. section "Check SSH authorized_keys file"  
17. for key in $(ls -1 /home)   
18. do   
19.     if [ -e $key/.ssh/authorized_keys ]; then   
20.         echo "$key : $key/.ssh/authorized_keys"  
21.     else  
22.         echo "$key : "  
23.     fi  
24. done  

 http://netkiller.github.com/

55.2.1. pam_tally2.so

此模块的功能是，登陆错误输入密码3次，5分钟后自动解禁，在未解禁期间输入正确密码也无法登陆。

在配置文件 /etc/pam.d/sshd 顶端加入

auth required pam_tally2.so deny=3 onerr=fail unlock_time=300
			

查看失败次数

# pam_tally2
Login           Failures Latest failure     From
root               14    07/12/13 15:44:37  192.168.6.2
neo                 8    07/12/13 15:45:36  192.168.6.2
			

重置计数器

# pam_tally2 -r -u root
Login           Failures Latest failure     From
root               14    07/12/13 15:44:37  192.168.6.2

# pam_tally2 -r -u neo
Login           Failures Latest failure     From
neo                 8    07/12/13 15:45:36  192.168.6.2
			

pam_tally2 计数器日志保存在 /var/log/tallylog 注意，这是二进制格式的文件

例 55.1. /etc/pam.d/sshd

# cat  /etc/pam.d/sshd
#%PAM-1.0
auth required pam_tally2.so deny=3 onerr=fail unlock_time=300

auth	   required	pam_sepermit.so
auth       include      password-auth
account    required     pam_nologin.so
account    include      password-auth
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    optional     pam_keyinit.so force revoke
session    include      password-auth
				

http://netkiller.github.com/

以上配置root用户不受限制, 如果需要限制root用户，参考下面

auth required pam_tally2.so deny=3 unlock_time=5 even_deny_root root_unlock_time=1800

55.2.2. pam_listfile.so

用户登陆限制

将下面一行添加到 /etc/pam.d/sshd 中，这里采用白名单方式，你也可以采用黑名单方式

auth       required     pam_listfile.so item=user sense=allow file=/etc/ssh/whitelist onerr=fail
			

将允许登陆的用户添加到 /etc/ssh/whitelist，除此之外的用户将不能通过ssh登陆到你的系统

# cat /etc/ssh/whitelist
neo
www
			

例 55.2. /etc/pam.d/sshd - pam_listfile.so

# cat /etc/pam.d/sshd
#%PAM-1.0
auth       required     pam_listfile.so item=user sense=allow file=/etc/ssh/whitelist onerr=fail
auth       required     pam_tally2.so deny=3 onerr=fail unlock_time=300

auth	   required	pam_sepermit.so
auth       include      password-auth
account    required     pam_nologin.so
account    include      password-auth
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    optional     pam_keyinit.so force revoke
session    include      password-auth
				

sense=allow 白名单方式, sense=deny 黑名单方式

auth       required     pam_listfile.so item=user sense=deny file=/etc/ssh/blacklist onerr=fail

延伸阅读：http://netkiller.github.com/