Linux nfs使用krb5的方式安全挂载

配置安全的网络nfs文件共享服务

由于本人是使用的rhce模拟考试环境来做的本题目，所以文中说到的实验脚本和评分脚本，以及krb5.keytab文件只有我本套环境独有，如果自己做练习可以不去使用实验脚本和评分脚本，直接进行配置服务并挂载就可以。

对此套环境有兴趣的朋友可以给我留言，看到必回复。

1、首先

服务端(server0)和客户端(desktop0)执行实验脚本

[root@server0 ~]# lab nfskrb5 setup
[root@desktop0 ~]# lab nfskrb5 setup

2、配置服务端(server0)

2.1 下载kerberos秘钥

[root@server0 ~]# wget -O /etc/krb5.keytab http://classroom.example.com/pub/keytabs/server0.keytab
--2019-04-16 22:51:45--  http://classroom.example.com/pub/keytabs/server0.keytab
Resolving classroom.example.com (classroom.example.com)... 172.25.254.254
Connecting to classroom.example.com (classroom.example.com)|172.25.254.254|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 1242 (1.2K)
Saving to: ‘/etc/krb5.keytab’

100%[==============================================================================>] 1,242       --.-K/s   in 0s      

2019-04-16 22:51:45 (130 MB/s) - ‘/etc/krb5.keytab’ saved [1242/1242]

2.2 修改nfs配置文件

[root@server0 ~]# vim /etc/sysconfig/nfs 
...
RPCNFSDARGS="-V 4.2"
...

使用4.2版本，nfs挂载的时候可以将selinux安全上下文同时导出

2.3 启动nfs-secure-server服务并设置开机自动启动

[root@server0 ~]# systemctl start nfs-secure-server
[root@server0 ~]# systemctl enable nfs-secure-server
ln -s '/usr/lib/systemd/system/nfs-secure-server.service' '/etc/systemd/system/nfs.target.wants/nfs-secure-server.service'
[root@server0 ~]#

2.4 创建共享文件夹并且将文件夹写入/etc/exportfs文件中

[root@server0 ~]# mkdir /securenfs
[root@server0 ~]# chown nfsnobody /securenfs/
[root@server0 ~]# ll -d !$
ll -d /securenfs/
drwxr-xr-x. 2 nfsnobody root 6 Apr 16 22:57 /securenfs/

[root@server0 ~]# vim /etc/exports
...
/securenfs desktop0(sec=krb5p,rw)
...

[root@server0 ~]# exportfs -r
[root@server0 ~]# exportfs 
/securenfs        desktop0.example.com

2.5 配置防火墙

[root@server0 ~]# firewall-cmd --permanent --add-service=nfs
success
[root@server0 ~]# firewall-cmd --reload
success
[root@server0 ~]# firewall-cmd --list-all
public (default, active)
  interfaces: eth0
  sources: 
  services: dhcpv6-client nfs ssh
  ports: 
  masquerade: no
  forward-ports: 
  icmp-blocks: 
  rich rules:

3、配置客户端(dekstop0)

3.1 下载秘钥文件

[root@desktop0 ~]# wget -O /etc/krb5.keytab http://classroom.example.com/pub/keytabs/desktop0.keytab

3.2 启动nfs-secure 服务并开机自启动

[root@desktop0 ~]# systemctl enable nfs-secure
ln -s '/usr/lib/systemd/system/nfs-secure.service' '/etc/systemd/system/nfs.target.wants/nfs-secure.service'
[root@desktop0 ~]# systemctl start nfs-secure

3.3 创建挂载点并设定开机自动挂载

[root@desktop0 ~]# mkdir /mnt/secureshare
[root@desktop0 ~]# vim /etc/fstab 

server0:/securenfs /mnt/secureshare     nfs     defaults,rw,v4.2,sec=krb5p      0       0

4、测试

4.1 在server0上建立测试文件

[root@server0 ~]# echo "Hello World" >> /securenfs/testfile.txt
临时更改该文件的selinux安全上下文，更改文件的拥有者和权限
[root@server0 ~]# chcon -t public_content_t /securenfs/testfile.txt 
[root@server0 ~]# chown ldapuser0:ldapuser0 /securenfs/testfile.txt 
[root@server0 ~]# chmod 644 /securenfs/testfile.txt 
[root@server0 ~]# ll -Z !$
ll -Z /securenfs/testfile.txt
-rw-r--r--. ldapuser0 ldapuser0 unconfined_u:object_r:public_content_t:s0 /securenfs/testfile.txt
[root@server0 ~]# 

4.2 desktop0查看该文件

因为前边加了-V 4.2的参数，所以public_content_t这个规则也被挂载过来来了

[root@desktop0 ~]# ll -Z /mnt/secureshare/testfile.txt 
-rw-r--r--. ldapuser0 ldapuser0 unconfined_u:object_r:public_content_t:s0 /mnt/secureshare/testfile.txt
[root@desktop0 ~]#

4.3用ldapuser0用户测试向该文件写入内容

[root@desktop0 ~]# ssh ldapuser0@localhost
ldapuser0@localhost's password: 
Creating home directory for ldapuser0.
[ldapuser0@desktop0 ~]$ echo "I'm write" >> /mnt/secureshare/testfile.txt 
[ldapuser0@desktop0 ~]$ cat !$
cat /mnt/secureshare/testfile.txt
Hello World
I'm write
[ldapuser0@desktop0 ~]$

用管理员用户写入无法写入该文件

[root@desktop0 ~]# echo "test" >> /mnt/secureshare/testfile.txt 
-bash: /mnt/secureshare/testfile.txt: Permission denied
[root@desktop0 ~]#

因为当前是用kerberos安全认证

5、提交评分脚本

[root@server0 ~]# lab nfskrb5 grade
Grading Kerberos NFS...
Checking correct krb5.keytab exists... PASS
Checking for correct RPCNFSDARGS... PASS
Checking nfs-secure-server service is started... PASS
Checking nfs-server service is enabled... PASS
Checking /securenfs directory exists... PASS
Checking for correct /etc/exports file... PASS
Checking if the server knows about the exported directory... PASS

Overall result: PASS
Congratulations! You've passed all requirements.
[root@desktop0 ~]# lab nfskrb5 grade
Grading exercise Kerberos NFS...
Checking correct krb5.keytab exists... PASS
Checking nfs-secure service is started... PASS
Checking nfs-secure service is enabled... PASS
Checking /mnt/secureshare directory exists...PASS
Checking for correct /etc/fstab entry for the secure export...PASS
Checking for mounted nfs share ...PASS

Overall result: PASS
Congratulations! You've passed all requirements