openvpn组网技术原理及设置过程（centos服务器/安卓客户端/linux客户端） - ToB企服应用市场:ToB评测及商务社交产业平台

#!/bin/sh
# A Sample OpenVPN-aware firewall.
# eth0 is connected to the internet.
# eth1 is connected to a private subnet.
# Change this subnet to correspond to your private
# ethernet subnet. Home will use HOME_NET/24 and
# Office will use OFFICE_NET/24.
PRIVATE=10.8.0.0/24
# Loopback address
LOOP=127.0.0.1
# Delete old iptables rules
# and temporarily block all traffic.
iptables -P OUTPUT DROP
iptables -P INPUT DROP
iptables -P FORWARD DROP
# 这条是删除原有的防火墙规则，删除的是filter表的规则，filter表的规则部分是作用在INPUT链上的
iptables -F
# Set default policies 重新设置链的默认策略
iptables -P OUTPUT ACCEPT
iptables -P INPUT DROP
iptables -P FORWARD DROP
# Prevent external packets from using loopback addr 这里是避免外部发来的数据包的源地址和目的
# 地址是回环地址，从而错误的递交给本地的进程。这应该是避免攻击的一些手段
iptables -A INPUT -i eth0 -s $LOOP -j DROP
iptables -A FORWARD -i eth0 -s $LOOP -j DROP
iptables -A INPUT -i eth0 -d $LOOP -j DROP
iptables -A FORWARD -i eth0 -d $LOOP -j DROP
# Anything coming from the Internet should have a real Internet address
# 这里是对一些有可能是错误发送的包进行丢弃
iptables -A FORWARD -i eth0 -s 192.168.0.0/16 -j DROP
iptables -A FORWARD -i eth0 -s 172.16.0.0/12 -j DROP
iptables -A FORWARD -i eth0 -s 10.0.0.0/8 -j DROP
iptables -A INPUT -i eth0 -s 192.168.0.0/16 -j DROP
iptables -A INPUT -i eth0 -s 172.16.0.0/12 -j DROP
iptables -A INPUT -i eth0 -s 10.0.0.0/8 -j DROP
# Block outgoing NetBios (if you have windows machines running
# on the private subnet). This will not affect any NetBios
# traffic that flows over the VPN tunnel, but it will stop
# local windows machines from broadcasting themselves to
# the internet.
# 这里是对windows的一些服务端口进行屏蔽，我们是linux不用管
iptables -A FORWARD -p tcp --sport 137:139 -o eth0 -j DROP
iptables -A FORWARD -p udp --sport 137:139 -o eth0 -j DROP
iptables -A OUTPUT -p tcp --sport 137:139 -o eth0 -j DROP
iptables -A OUTPUT -p udp --sport 137:139 -o eth0 -j DROP
# Check source address validity on packets going out to internet
#iptables -A FORWARD -s ! $PRIVATE -i eth1 -j DROP
#iptables -A FORWARD -m iprange ! --src-range 10.0.0.0-10.0.0.255 -i eth1 -j DROP
# Allow local loopback 这里是对回环地址放行
iptables -A INPUT -s $LOOP -j ACCEPT
iptables -A INPUT -d $LOOP -j ACCEPT
# Allow incoming pings (can be disabled) 这里是对icmp协议放行，也就是能响应ping命令
iptables -A INPUT -p icmp --icmp-type echo-request -j ACCEPT
# Allow services such as www and ssh (can be disabled) 这里是对常用的服务端口入栈放行
iptables -A INPUT -p tcp --dport http -j ACCEPT
iptables -A INPUT -p tcp --dport ssh -j ACCEPT
iptables -A INPUT -p tcp --dport 6679 -j ACCEPT
# Allow incoming OpenVPN packets
# Duplicate the line below for each
# OpenVPN tunnel, changing --dport n
# to match the OpenVPN UDP port.
#
# In OpenVPN, the port number is
# controlled by the --port n option.
# If you put this option in the config
# file, you can remove the leading '--'
#
# If you taking the stateful firewall
# approach (see the OpenVPN HOWTO),
# then comment out the line below.
# 这里是自己想要放行的端口和协议数据，有其他端口可以自行添加
iptables -A INPUT -p udp --dport 1194 -j ACCEPT
iptables -A INPUT -p udp --dport 9981 -j ACCEPT
iptables -A INPUT -p tcp --dport 9981 -j ACCEPT
iptables -A INPUT -p tcp --dport 6379 -j ACCEPT
iptables -A INPUT -p udp --dport 6379 -j ACCEPT
iptables -A INPUT -p udp --dport 6680 -j ACCEPT
iptables -A INPUT -p tcp --dport 6680 -j ACCEPT
iptables -A INPUT -p tcp --dport 1723 -j ACCEPT
# Allow packets from TUN/TAP devices.
# When OpenVPN is run in a secure mode,
# it will authenticate packets prior
# to their arriving on a tun or tap
# interface. Therefore, it is not
# necessary to add any filters here,
# unless you want to restrict the
# type of packets which can flow over
# the tunnel.
# 这里主要是对tun+网卡和tap+网卡的入栈和转发数据包放行，+号应该表示的是一个通配符
iptables -A INPUT -i tun+ -j ACCEPT
iptables -A FORWARD -i tun+ -j ACCEPT
iptables -A INPUT -i tap+ -j ACCEPT
iptables -A FORWARD -i tap+ -j ACCEPT
# Allow packets from private subnets 这里是对eth1网卡的入栈和转发数据包放行
iptables -A INPUT -i eth1 -j ACCEPT
iptables -A FORWARD -i eth1 -j ACCEPT
# Keep state of connections from local machine and private subnets
# 这里是放行状态为NEW的出栈数据包
iptables -A OUTPUT -m state --state NEW -o eth0 -j ACCEPT
# 这里放行已经建立连接和关联的入栈数据包
iptables -A INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
# 这里放行需要转发的包，有这两条，本机才能作为NAT代理客户端访问互联网
iptables -A FORWARD -m state --state NEW -o eth0 -j ACCEPT
iptables -A FORWARD -m state --state ESTABLISHED,RELATED -j ACCEPT
# Masquerade local subnet
# 对于需要通过openvpn服务端访问外网的客户端节点，这个防火墙配置是必需的，也是最重要的配置
# 这个防火墙的配置是将路由后的源IP地址是10.8.0.0/24，输出网卡是eth0的数据包的源ip地址进行修改，改成本机的ip地址，这样响应数据包才能正确的给我们转发回来
iptables -t nat -A POSTROUTING -s $PRIVATE -o eth0 -j MASQUERADE

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PRIVATE=10.8.0.0/24
# 清空原有INPUT链的防火墙规则
iptables -F
# 放行所有输出包
iptables -P OUTPUT ACCEPT
# 放行所有输入包
iptables -P INPUT ACCEPT
# 放行所有需要转发的包
iptables -P FORWARD ACCEPT
# 对于需要通过openvpn服务端访问外网的客户端节点，这个防火墙配置是必需的，也是最重要的配置
# 这个防火墙的配置是将路由后的源IP地址是10.8.0.0/24，输出网卡是eth0的数据包的源ip地址进行修改，改成本机的ip地址，这样响应数据包才能正确的给我们转发回来
iptables -t nat -A POSTROUTING -s $PRIVATE -o eth0 -j MASQUERADE

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#################################################
# Sample OpenVPN 2.0 config file for #
# multi-client server. #
# #
# This file is for the server side #
# of a many-clients <-> one-server #
# OpenVPN configuration. #
# #
# OpenVPN also supports #
# single-machine <-> single-machine #
# configurations (See the Examples page #
# on the web site for more info). #
# #
# This config should work on Windows #
# or Linux/BSD systems. Remember on #
# Windows to quote pathnames and use #
# double backslashes, e.g.: #
# "C:\\Program Files\\OpenVPN\\config\\foo.key" #
# #
# Comments are preceded with '#' or ';' #
#################################################
# Which local IP address should OpenVPN
# listen on? (optional)
;local a.b.c.d
# Which TCP/UDP port should OpenVPN listen on?
# If you want to run multiple OpenVPN instances
# on the same machine, use a different port
# number for each one. You will need to
# open up this port on your firewall.
# 这个是监听端口
port 6379
# TCP or UDP server?
# 使用的协议，推荐使用udp协议，速度会快两三倍
proto tcp
;proto udp
# "dev tun" will create a routed IP tunnel,
# "dev tap" will create an ethernet tunnel.
# Use "dev tap0" if you are ethernet bridging
# and have precreated a tap0 virtual interface
# and bridged it with your ethernet interface.
# If you want to control access policies
# over the VPN, you must create firewall
# rules for the the TUN/TAP interface.
# On non-Windows systems, you can give
# an explicit unit number, such as tun0.
# On Windows, use "dev-node" for this.
# On most systems, the VPN will not function
# unless you partially or fully disable
# the firewall for the TUN/TAP interface.
# 这里我们就使用tun，tap是以太网桥接方式，没有深究
;dev tap
dev tun
# Windows needs the TAP-Win32 adapter name
# from the Network Connections panel if you
# have more than one. On XP SP2 or higher,
# you may need to selectively disable the
# Windows firewall for the TAP adapter.
# Non-Windows systems usually don't need this.
;dev-node MyTap
# SSL/TLS root certificate (ca), certificate
# (cert), and private key (key). Each client
# and the server must have their own cert and
# key file. The server and all clients will
# use the same ca file.
#
# See the "easy-rsa" directory for a series
# of scripts for generating RSA certificates
# and private keys. Remember to use
# a unique Common Name for the server
# and each of the client certificates.
#
# Any X509 key management system can be used.
# OpenVPN can also use a PKCS #12 formatted key file
# (see "pkcs12" directive in man page).
# 这里配置ca证书，服务端证书，服务端密钥
ca ./crt/ca.crt
cert ./crt/server.crt
key ./crt/server.key # This file should be kept secret
# Diffie hellman parameters.
# Generate your own with:
# openssl dhparam -out dh2048.pem 2048
# 都告诉你了，直接使用命令openssl dhparam -out dh2048.pem 2048生成，具体作用可以自行谷歌
dh ./crt/dh2048.pem
# Network topology
# Should be subnet (addressing via IP)
# unless Windows clients v2.0.9 and lower have to
# be supported (then net30, i.e. a /30 per client)
# Defaults to net30 (not recommended)
;topology subnet
# Configure server mode and supply a VPN subnet
# for OpenVPN to draw client addresses from.
# The server will take 10.8.0.1 for itself,
# the rest will be made available to clients.
# Each client will be able to reach the server
# on 10.8.0.1. Comment this line out if you are
# ethernet bridging. See the man page for more info.
# 这里配置openvpn网络，包括ip和子网掩码，我们就用默认的
server 10.8.0.0 255.255.255.0
# Maintain a record of client <-> virtual IP address
# associations in this file. If OpenVPN goes down or
# is restarted, reconnecting clients can be assigned
# the same virtual IP address from the pool that was
# previously assigned.
# 这里是为了保证同一个客户端多次连接后分配给相同的局域网ip地址
ifconfig-pool-persist ipp.txt
# Configure server mode for ethernet bridging.
# You must first use your OS's bridging capability
# to bridge the TAP interface with the ethernet
# NIC interface. Then you must manually set the
# IP/netmask on the bridge interface, here we
# assume 10.8.0.4/255.255.255.0. Finally we
# must set aside an IP range in this subnet
# (start=10.8.0.50 end=10.8.0.100) to allocate
# to connecting clients. Leave this line commented
# out unless you are ethernet bridging.
;server-bridge 10.8.0.4 255.255.255.0 10.8.0.50 10.8.0.100
# Configure server mode for ethernet bridging
# using a DHCP-proxy, where clients talk
# to the OpenVPN server-side DHCP server
# to receive their IP address allocation
# and DNS server addresses. You must first use
# your OS's bridging capability to bridge the TAP
# interface with the ethernet NIC interface.
# Note: this mode only works on clients (such as
# Windows), where the client-side TAP adapter is
# bound to a DHCP client.
;server-bridge
# Push routes to the client to allow it
# to reach other private subnets behind
# the server. Remember that these
# private subnets will also need
# to know to route the OpenVPN client
# address pool (10.8.0.0/255.255.255.0)
# back to the OpenVPN server.
;push "route 192.168.10.0 255.255.255.0"
;push "route 192.168.20.0 255.255.255.0"
# To assign specific IP addresses to specific
# clients or if a connecting client has a private
# subnet behind it that should also have VPN access,
# use the subdirectory "ccd" for client-specific
# configuration files (see man page for more info).
# EXAMPLE: Suppose the client
# having the certificate common name "Thelonious"
# also has a small subnet behind his connecting
# machine, such as 192.168.40.128/255.255.255.248.
# First, uncomment out these lines:
;client-config-dir ccd
;route 192.168.40.128 255.255.255.248
# Then create a file ccd/Thelonious with this line:
# iroute 192.168.40.128 255.255.255.248
# This will allow Thelonious' private subnet to
# access the VPN. This example will only work
# if you are routing, not bridging, i.e. you are
# using "dev tun" and "server" directives.
# EXAMPLE: Suppose you want to give
# Thelonious a fixed VPN IP address of 10.9.0.1.
# First uncomment out these lines:
;client-config-dir ccd
;route 10.9.0.0 255.255.255.252
# Then add this line to ccd/Thelonious:
# ifconfig-push 10.9.0.1 10.9.0.2
# Suppose that you want to enable different
# firewall access policies for different groups
# of clients. There are two methods:
# (1) Run multiple OpenVPN daemons, one for each
# group, and firewall the TUN/TAP interface
# for each group/daemon appropriately.
# (2) (Advanced) Create a script to dynamically
# modify the firewall in response to access
# from different clients. See man
# page for more info on learn-address script.
;learn-address ./script
# If enabled, this directive will configure
# all clients to redirect their default
# network gateway through the VPN, causing
# all IP traffic such as web browsing and
# and DNS lookups to go through the VPN
# (The OpenVPN server machine may need to NAT
# or bridge the TUN/TAP interface to the internet
# in order for this to work properly).
# 这里是将客户端的所有流量定向到服务器端，也就是让客户端修改自己的路由表
# 把服务器端的局域网ip地址作为网关，在上面的《三、路由表在openvpn组网中的作用》中有提到
push "redirect-gateway def1 bypass-dhcp"
# Certain Windows-specific network settings
# can be pushed to clients, such as DNS
# or WINS server addresses. CAVEAT:
# http://openvpn.net/faq.html#dhcpcaveats
# The addresses below refer to the public
# DNS servers provided by opendns.com.
# 这里是给客户端推送DNS服务器地址，如果没有这个推送，客户端还是会用本地默认的DNS地址，有可能导致
# DNS解析失败，这个我是使用命令查看服务器本地的DNS服务器：cat /etc/resolv.conf
# 你也可以使用其他的DNS服务器，只要客户端能正确解析出域名
push "dhcp-option DNS 100.100.2.136"
push "dhcp-option DNS 100.100.2.138"
# Uncomment this directive to allow different
# clients to be able to "see" each other.
# By default, clients will only see the server.
# To force clients to only see the server, you
# will also need to appropriately firewall the
# server's TUN/TAP interface.
# 这里是配置让接入到服务器的多个客户端彼此能看到对方，即能正常通信
client-to-client
# Uncomment this directive if multiple clients
# might connect with the same certificate/key
# files or common names. This is recommended
# only for testing purposes. For production use,
# each client should have its own certificate/key
# pair.
#
# IF YOU HAVE NOT GENERATED INDIVIDUAL
# CERTIFICATE/KEY PAIRS FOR EACH CLIENT,
# EACH HAVING ITS OWN UNIQUE "COMMON NAME",
# UNCOMMENT THIS LINE OUT.
# 这里允许使用同一个证书的多个客户端登录
duplicate-cn
# The keepalive directive causes ping-like
# messages to be sent back and forth over
# the link so that each side knows when
# the other side has gone down.
# Ping every 10 seconds, assume that remote
# peer is down if no ping received during
# a 120 second time period.
keepalive 10 120
# For extra security beyond that provided
# by SSL/TLS, create an "HMAC firewall"
# to help block DoS attacks and UDP port flooding.
#
# Generate with:
# openvpn --genkey --secret ta.key
#
# The server and each client must have
# a copy of this key.
# The second parameter should be '0'
# on the server and '1' on the clients.
# 这里的ta.key文件也是根据命令openvpn --genkey --secret ta.key直接生成
tls-auth ./crt/ta.key 0 # This file is secret
# Select a cryptographic cipher.
# This config item must be copied to
# the client config file as well.
# Note that v2.4 client/server will automatically
# negotiate AES-256-GCM in TLS mode.
# See also the ncp-cipher option in the manpage
# 这里是指定对称加密算法，服务端和客户的配置要一样
cipher AES-256-GCM
# Enable compression on the VPN link and push the
# option to the client (v2.4+ only, for earlier
# versions see below)
# 这里是允许压缩，并且把这个压缩配置推送给了客户端，客户端可以不用配置
compress lz4-v2
push "compress lz4-v2"
# For compression compatible with older clients use comp-lzo
# If you enable it here, you must also
# enable it in the client config file.
;comp-lzo
# The maximum number of concurrently connected
# clients we want to allow.
;max-clients 100
# It's a good idea to reduce the OpenVPN
# daemon's privileges after initialization.
#
# You can uncomment this out on
# non-Windows systems.
# 这里设置openvpn允许使用的角色和用户组
user root
group root
# The persist options will try to avoid
# accessing certain resources on restart
# that may no longer be accessible because
# of the privilege downgrade.
# 这里不是很懂，直接保持原样，没有这个有时候会报错
persist-key
persist-tun
# Output a short status file showing
# current connections, truncated
# and rewritten every minute.
# 这里是每分钟记录客户端的状态
status openvpn-status.log
# By default, log messages will go to the syslog (or
# on Windows, if running as a service, they will go to
# the "\Program Files\OpenVPN\log" directory).
# Use log or log-append to override this default.
# "log" will truncate the log file on OpenVPN startup,
# while "log-append" will append to it. Use one
# or the other (but not both).
# 这里是日志输出文件，log是每次启动覆盖之前的日志，log-append会往后追加，不要同时配置两个
log ./openvpn.log
;log-append ./openvpn.log
# Set the appropriate level of log
# file verbosity.
#
# 0 is silent, except for fatal errors
# 4 is reasonable for general usage
# 5 and 6 can help to debug connection problems
# 9 is extremely verbose
# 这里是日志输出等级，数字越高，日志越详细
verb 3
# Silence repeating messages. At most 20
# sequential messages of the same message
# category will be output to the log.
;mute 20
# Notify the client that when the server restarts so it
# can automatically reconnect.
;explicit-exit-notify 1

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##############################################
# Sample client-side OpenVPN 2.0 config file #
# for connecting to multi-client server. #
# #
# This configuration can be used by multiple #
# clients, however each client should have #
# its own cert and key files. #
# #
# On Windows, you might want to rename this #
# file so it has a .ovpn extension #
##############################################
# Specify that we are a client and that we
# will be pulling certain config file directives
# from the server.
# 这里需要指明是客户端才行
client
# Use the same setting as you are using on
# the server.
# On most systems, the VPN will not function
# unless you partially or fully disable
# the firewall for the TUN/TAP interface.
# 这里跟服务端的配置一样
;dev tap
dev tun
# Windows needs the TAP-Win32 adapter name
# from the Network Connections panel
# if you have more than one. On XP SP2,
# you may need to disable the firewall
# for the TAP adapter.
;dev-node MyTap
# Are we connecting to a TCP or
# UDP server? Use the same setting as
# on the server.
# 这里是使用协议，必须跟服务端一致
proto tcp
;proto udp
# The hostname/IP and port of the server.
# You can have multiple remote entries
# to load balance between the servers.
# 这里填服务器端的IP端口
remote 1.1.1.1 6679
#remote my-server-2 1194
# Choose a random host from the remote
# list for load-balancing. Otherwise
# try hosts in the order specified.
;remote-random
# Keep trying indefinitely to resolve the
# host name of the OpenVPN server. Very useful
# on machines which are not permanently connected
# to the internet such as laptops.
# 这里就用默认的配置
resolv-retry infinite
# Most clients don't need to bind to
# a specific local port number.
# 这里指明通信绑定的端口，一般都不指定，系统随机分配
nobind
# Downgrade privileges after initialization (non-Windows only)
;user nobody
;group nobody
# Try to preserve some state across restarts.
# 这里不是很懂用来干嘛的，看注释是重启的时候维持一些状态，我们就使用默认配置
persist-key
persist-tun
# If you are connecting through an
# HTTP proxy to reach the actual OpenVPN
# server, put the proxy server/IP and
# port number here. See the man page
# if your proxy server requires
# authentication.
;http-proxy-retry # retry on connection failures
;http-proxy [proxy server] [proxy port #]
# Wireless networks often produce a lot
# of duplicate packets. Set this flag
# to silence duplicate packet warnings.
;mute-replay-warnings
# SSL/TLS parms.
# See the server config file for more
# description. It's best to use
# a separate .crt/.key file pair
# for each client. A single ca
# file can be used for all clients.
# 这里就配置ssl通信用的ca证书，客户端证书，客户端私钥，可以指定路径，默认是当前目录
ca ca.crt
cert client.crt
key client.key
# Verify server certificate by checking that the
# certicate has the correct key usage set.
# This is an important precaution to protect against
# a potential attack discussed here:
# http://openvpn.net/howto.html#mitm
#
# To use this feature, you will need to generate
# your server certificates with the keyUsage set to
# digitalSignature, keyEncipherment
# and the extendedKeyUsage to
# serverAuth
# EasyRSA can do this for you.
# 这里需要注更改默认的配置，默认是打开的，因为我制作的服务端证书没有它指定的几个信息，我就不做校验了，当然你也可以按他的指示重新制作服务端证书，这个是为了避免潜在的攻击的
#remote-cert-tls server
# If a tls-auth key is used on the server
# then every client must also have the key.
# 这里配置tls认证key，这个就是服务器使用的ta.key，两端是同一个文件
tls-auth ta.key 1
# Select a cryptographic cipher.
# If the cipher option is used on the server
# then you must also specify it here.
# Note that v2.4 client/server will automatically
# negotiate AES-256-GCM in TLS mode.
# See also the ncp-cipher option in the manpage
# 加密算法，跟服务端要一致，但是我发现服务端配置的是AES-256-GCM，这里配置的是AES-256-CBC，也一样能正常加解密，比较奇怪，可能最终协商一致就可以
cipher AES-256-CBC
# Enable compression on the VPN link.
# Don't enable this unless it is also
# enabled in the server config file.
#comp-lzo
# Set log file verbosity.
# 日志等级
verb 3
# Silence repeating messages
;mute 20
# 服务端已经配置，这里不需要重新配置
;redirect-gateway autolocal

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