linux CentOS 7中firewall防火墙详解和配置以及切换为iptables防火墙

官方文档介绍地址：


https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Security_Guide/sec-Using_Firewalls.html#sec-Introduction_to_firewalld1

<https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux/7/html/Security_Guide/sec-Using_Firewalls.html#sec-Introduction_to_firewalld1>

<>一、firewall介绍

CentOS 7中防火墙是一个非常的强大的功能，在CentOS 6.5中在iptables防火墙中进行了升级了。

1、官方介绍

The dynamic firewall daemon firewalld provides a dynamically managed firewall
with support for network “zones” to assign a level of trust to a network and
its associated connections and interfaces. It has support for IPv4 and IPv6
firewall settings. It supports Ethernet bridges and has a separation of runtime
and permanent configuration options. It also has an interface for services or
applications to add firewall rules directly.

2、什么是区域Zone：

网络区域定义了网络连接的可信等级。这是一个 一对多的关系，这意味着一次连接可以仅仅是一个区域的一部分，而一个区域可以用于很多连接。

3、哪个区域可用?

由firewalld 提供的区域按照从不信任到信任的顺序排序。

4、区域的分类?

Firewalls can be used to separate networks into different zones based on the
level of trust the user has decided to place on the devices and traffic within
that network. NetworkManager informs firewalld to which zone an interface
belongs. An interface’s assigned zone can be changed by NetworkManager or via
the firewall-config tool which can open the relevant NetworkManager window for
you.

The zone settings in /etc/firewalld/ are a range of preset settings which can
be quickly applied to a network interface. They are listed here with a brief
explanation:

drop 
Any incoming network packets are dropped, there is no reply. Only outgoing
network connections are possible.

block 
Any incoming network connections are rejected with an icmp-host-prohibited
message for IPv4 and icmp6-adm-prohibited for IPv6. Only network connections
initiated from within the system are possible.

public 
For use in public areas. You do not trust the other computers on the network
to not harm your computer. Only selected incoming connections are accepted.

external 
For use on external networks with masquerading enabled especially for
routers. You do not trust the other computers on the network to not harm your
computer. Only selected incoming connections are accepted.

dmz 
For computers in your demilitarized zone that are publicly-accessible with
limited access to your internal network. Only selected incoming connections are
accepted.

work 
For use in work areas. You mostly trust the other computers on networks to
not harm your computer. Only selected incoming connections are accepted.

home 
For use in home areas. You mostly trust the other computers on networks to
not harm your computer. Only selected incoming connections are accepted.

internal 
For use on internal networks. You mostly trust the other computers on the
networks to not harm your computer. Only selected incoming connections are
accepted.

trusted 
All network connections are accepted. 
It is possible to designate one of these zones to be the default zone. When
interface connections are added to NetworkManager, they are assigned to the
default zone. On installation, the default zone in firewalld is set to be the
public zone.

注：具体内容，请参见官方文档介绍！

<>二、firewall配置

The configuration for firewalld is stored in various XML files in 
/usr/lib/firewalld/ and /etc/firewalld/.

This allows a great deal of flexibility as the files can be edited, written
to, backed up, used as templates for other installations and so on.

注意：以下firewalld 的操作只有重启之后才有效：service firewalld restart 重启

1、系统配置目录
/usr/lib/firewalld/services
目录中存放定义好的网络服务和端口参数，系统参数，不能修改。



2、用户配置目录
/etc/firewalld/


3、如何自定义添加端口

用户可以通过修改配置文件的方式添加端口，也可以通过命令的方式添加端口，注意，修改的内容会在/etc/firewalld/目录下的配置文件中还体现。

* 3.1、命令的方式添加端口 firewall-cmd --permanent --add-port=9527/tcp
参数介绍：
1、firewall-cmd：是Linux提供的操作firewall的一个工具； 2、--permanent：表示设置为持久；
3、--add-port：标识添加的端口；
另外，firewall中有Zone的概念，可以将具体的端口制定到具体的zone配置文件中。

例如：添加8010端口
firewall-cmd --zone=public --permanent --add-port=8010/tcp
--zone=public：指定的zone为public；
 

*  
* 添加结果如下：


如果–zone=dmz 这样设置的话，会在dmz.xml文件中新增一条。

* 3.2、修改配置文件的方式添加端口 <?xml version="1.0" encoding="utf-8"?> <zone>
<short>Public</short> <description>For use in public areas.</description> <rule
family="ipv4"> <source address="122.10.70.234"/> <port protocol="udp"
port="514"/> <accept/> </rule> <rule family="ipv4"> <source
address="123.60.255.14"/> <port protocol="tcp" port="10050-10051"/> <accept/>
</rule> <rule family="ipv4"> <source address="192.249.87.114"/> 放通指定ip，指定端口、协议
<port protocol="tcp" port="80"/> <accept/> </rule> <rule family="ipv4">
放通任意ip访问服务器的9527端口 <port protocol="tcp" port="9527"/> <accept/> </rule> </zone>
<?xml version="1.0" encoding="utf-8"?> <zone> <short>Public</short>
<description>For use in public areas.</description> <rule family="ipv4">
<source address="122.10.70.234"/> <port protocol="udp" port="514"/> <accept/>
</rule> <rule family="ipv4"> <source address="123.60.255.14"/> <port
protocol="tcp" port="10050-10051"/> <accept/> </rule> <rule family="ipv4">
<source address="192.249.87.114"/> 放通指定ip，指定端口、协议 <port protocol="tcp"
port="80"/> <accept/> </rule> <rule family="ipv4"> 放通任意ip访问服务器的9527端口 <port
protocol="tcp" port="9527"/> <accept/> </rule> </zone>
上述的一个配置文件可以很好的看出：
1、添加需要的规则，开放通源ip为122.10.70.234，端口514，协议tcp；
2、开放通源ip为123.60.255.14，端口10050-10051，协议tcp；/3、开放通源ip为任意，端口9527，协议tcp；
<>三、firewall常用命令

1、重启、关闭、开启firewalld.service服务
service firewalld restart 重启 service firewalld start 开启 service firewalld stop
关闭
2、查看firewall服务状态
systemctl status firewall
3、查看firewall的状态
firewall-cmd --state


4、查看防火墙规则
firewall-cmd --list-all


<>四、CentOS切换为iptables防火墙

切换到iptables首先应该关掉默认的firewalld，然后安装iptables服务。

1、关闭firewall：
service firewalld stop systemctl disable firewalld.service #禁止firewall开机启动
2、安装iptables防火墙
yum install iptables-services #安装
3、编辑iptables防火墙配置
vi /etc/sysconfig/iptables #编辑防火墙配置文件
下边是一个完整的配置文件：
Firewall configuration written by system-config-firewall Manual customization
of this file is not recommended. *filter :INPUT ACCEPT [0:0] :FORWARD ACCEPT
[0:0] :OUTPUT ACCEPT [0:0] -A INPUT -m state --state ESTABLISHED,RELATED -j
ACCEPT -A INPUT -p icmp -j ACCEPT -A INPUT -i lo -j ACCEPT -A INPUT -m state
--state NEW -m tcp -p tcp --dport 22 -j ACCEPT -A INPUT -m state --state NEW -m
tcp -p tcp --dport 80 -j ACCEPT -A INPUT -m state --state NEW -m tcp -p tcp
--dport 3306 -j ACCEPT -A INPUT -j REJECT --reject-with icmp-host-prohibited -A
FORWARD -j REJECT --reject-with icmp-host-prohibited COMMIT
:wq! #保存退出
service iptables start #开启 systemctl enable iptables.service #设置防火墙开机启动
转载：https://blog.csdn.net/xlgen157387/article/details/52672988
<https://blog.csdn.net/xlgen157387/article/details/52672988> 

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