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解决目标主机showmount -e信息泄露(CVE-1999-0554)

article 2024/9/30 17:54:24

企业中，一般都会使用NFS网络文件系统。最近在项目上做等保测评的工作中，发现了一个“目标主机showmount -e信息泄露(CVE-1999-0554)“的问题。最终采取的解决措施如下：

1. 问题现状

目前，我有三台主机，分别为主机a，主机b和主机c，其中主机a为服务器，部署了nfs，只允许主机b使用，然而主机c可以通过showmount -e命令来浏览主机a的目录清单。

#主机a的nfs服务配置文件，其中10.28.7.210是主机b的IP地址
[root@a ~]# cat /etc/exports
/data  10.28.7.210/32(rw,sync)

#主机b使用showmount -e命令可以查看到的信息
[root@b ~]# showmount -e 10.28.7.253
Export list for 10.28.7.253:
/data 10.28.7.210/32
[root@b ~]# ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 10.28.7.210  netmask 255.255.255.0  broadcast 10.28.7.255

#主机c也可以使用showmount -e命令查看nfs服务器上共享出来的目录信息
[root@c ~]# showmount -e 10.28.7.253 
Export list for 10.28.7.253:
/data 10.28.7.210/32
[root@c ~]# ifconfig
eth0      Link encap:Ethernet  HWaddr 00:0C:29:62:18:E8  
          inet addr:10.28.7.252  Bcast:10.28.7.255  Mask:255.255.255.0

2. 解决方法

在NFS服务器上的/etc/hosts.allow和/etc/hosts.deny文件添加以下内容即可解决该问题。

编辑/etc/hosts.allow文件

[root@a ~]# cat /etc/hosts.allow
#
# hosts.allow    This file contains access rules which are used to
#        allow or deny connections to network services that
#        either use the tcp_wrappers library or that have been
#        started through a tcp_wrappers-enabled xinetd.
#
#        See 'man 5 hosts_options' and 'man 5 hosts_access'
#        for information on rule syntax.
#        See 'man tcpd' for information on tcp_wrappers
#
#
mountd:10.28.7.210    #<==添加客户端IP地址，相当于白名单

编辑/etc/hosts.deny文件

[root@a ~]# cat /etc/hosts.deny 
#
# hosts.deny    This file contains access rules which are used to
#        deny connections to network services that either use
#        the tcp_wrappers library or that have been
#        started through a tcp_wrappers-enabled xinetd.
#
#        The rules in this file can also be set up in
#        /etc/hosts.allow with a 'deny' option instead.
#
#        See 'man 5 hosts_options' and 'man 5 hosts_access'
#        for information on rule syntax.
#        See 'man tcpd' for information on tcp_wrappers
#
#
mountd:all    #<==添加该行，相当于黑名单

在以上两个文件中添加对应内容之后，不需要重启nfs服务，即可生效

3. 结果测试

#主机c使用showmount -e命令，无法查看相关信息
[root@c ~]# showmount -e 10.28.7.253 
rpc mount export: RPC: Authentication error; why = Failed (unspecified error)
[root@c ~]# ifconfig
eth0      Link encap:Ethernet  HWaddr 00:0C:29:62:18:E8  
          inet addr:10.28.7.252  Bcast:10.28.7.255  Mask:255.255.255.

#主机b使用正常
[root@b ~]# showmount -e 10.28.7.253
Export list for 10.28.7.253:
/data 10.28.7.210/32
[root@b ~]# ifconfig
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 10.28.7.210  netmask 255.255.255.0  broadcast 10.28.7.255

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