• Linux下OpenVPN服务安装记

    2011年12月9日、2011年12月30日更新iptables和启动脚本的描述。2012年11月8日更新网络传输优化配置。

    操作系统是CentOS,运行在XEN架构的VPS上面。

    环境配置

    首先,检测VPS是否支持TUN(via):

    cat /dev/net/tun

    返回“cat: /dev/net/tun: File descriptor in bad state”说明支持TUN。

    检测iptables_nat模块支持:

    iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE

    如果返回信息为:iptables: Unknown error 4294967295 说明支持模块。

    安装LZO库:

    wget http://www.oberhumer.com/opensource/lzo/download/lzo-2.05.tar.gz
    tar zxvf lzo-2.05.tar.gz
    cd lzo-2.05
    ./configure
    make
    make install

    安装OpenSSL开发库:

    yum install -y openssl-devel

    服务端安装配置

    然后,在服务器端下载OpenVPN源代码(下载页面),目前最新版本为2.2.0:

    wget http://swupdate.openvpn.net/community/releases/openvpn-2.2.0.tar.gz

    解压编译安装:

    tar zxf openvpn-2.2.0.tar.gz
    cd openvpn-2.2.0
    ./configure --prefix=/usr/local/openvpn
    make
    make install

    复制服务端样例配置文件:

    cp sample-config-files/server.conf /usr/local/openvpn/etc/server.conf

    编辑配置文件为,比如我的以下内容,采用UDP协议监听53端口:

    #################################################
    # 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.
    port 53

    # TCP or UDP server?
    ;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.
    ;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).
    ca /usr/local/openvpn/etc/2.0/keys/ca.crt
    cert /usr/local/openvpn/etc/2.0/keys/server.crt
    key /usr/local/openvpn/etc/2.0/keys/server.key  # This file should be kept secret

    # Diffie hellman parameters.
    # Generate your own with:
    #   openssl dhparam -out dh1024.pem 1024
    # Substitute 2048 for 1024 if you are using
    # 2048 bit keys.
    dh /usr/local/openvpn/etc/2.0/keys/dh1024.pem

    # 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.
    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.
    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).
    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.
    ;push "dhcp-option DNS 208.67.222.222"
    ;push "dhcp-option DNS 208.67.220.220"
    push "dhcp-option DNS 8.8.8.8"
    push "dhcp-option DNS 8.8.4.4"

    # 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.
    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.
    ;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.
    ;tls-auth ta.key 0 # This file is secret

    # Select a cryptographic cipher.
    # This config item must be copied to
    # the client config file as well.
    ;cipher BF-CBC        # Blowfish (default)
    ;cipher AES-128-CBC   # AES
    ;cipher DES-EDE3-CBC  # Triple-DES

    # Enable compression on the VPN link.
    # 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.
    user nobody
    group nobody

    # The persist options will try to avoid
    # accessing certain resources on restart
    # that may no longer be accessible because
    # of the privilege downgrade.
    persist-key
    persist-tun

    # Output a short status file showing
    # current connections, truncated
    # and rewritten every minute.
    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).
    ;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
    verb 3

    # Silence repeating messages.  At most 20
    # sequential messages of the same message
    # category will be output to the log.
    ;mute 20

    复制密钥制作工具:

    cp easy-rsa/ -r /usr/local/openvpn/etc

    下面开始制作密钥。

    cd /usr/local/openvpn/etc/2.0
    source ./vars #可以先修改vars文件内容
    ./clean-all
    ./build-ca

    在这里,我将Common Name那一行填为“server”。

    生成服务器密钥,其中的“server”是上一步的Common Name:

    ./build-key-server server

    生成客户端密钥,客户端名字这里为“client”:

    ./build-key client

    其中的“Common Name”也应该设为客户端的名字,即这里的“client”。

    如果想要多个客户端密钥,则对应运行“./build-key client1”“./build-key client2”等等,同时其中的“Common Name”也对应改为“client1”“client2”。

    生成Diffie Hellman参数:

    ./build-dh

    将生成的各种密钥打包:

    tar zcf keys.tar.gz keys/

    然后可以通过SFTP或者FTP传送到客户端,即本地。

    启动和关闭OpenVPN服务端

    源代码目录中的“sample-scripts”目录里面有一个openvpn.init可以很方便地控制OpenVPN的启动和关闭。

    首先将它拷贝到自己的目录,改名为openvpn.sh,然后编辑里面的内容。

    把openvpn_locations=在第一个引号后面加上/usr/local/openvpn/sbin/openvpn,后面加上空格以区分原有内容

    work=一行的后面的内容删除,改为/usr/local/openvpn/etc

    #echo 1 > /proc/sys/net/ipv4/ip_forward前面的#删掉

    在“start)”中“# Run startup script, if defined”前加上:

    iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE

    iptables -t nat -A POSTROUTING -s 10.8.0.0/24 -j SNAT --to-source 你的VPS的IP #这样一般可以解决常见问题2的现象

    在“stop)”中“# Run shutdown script, if defined”前加上:

    iptables -t nat -D POSTROUTING -s 10.8.0.0/24 -o eth0 -j MASQUERADE

    iptables -t nat -D POSTROUTING -s 10.8.0.0/24 -j SNAT --to-source 你的VPS的IP

    这样就启动脚本就可以方便地控制iptables和相关的网络转发啦。可以用以下命令启动和关闭OpenVPN:

    ./openvpn.sh start

    ./openvpn.sh stop

    客户端安装配置

    下载地址:http://swupdate.openvpn.net/community/releases/openvpn-2.2.0-install.exe。然后安装。

    安装完毕后,点击“开始”——OpenVPN——Utilities——Add a new TAP-Win32 virtual ethernet adapter,增加虚拟网卡,以后就不用执行这步了。

    然后在OpenVPN安装目录下建立config文件夹,从服务器上把源代码目录中,sample-config-files中的client.conf下载,并命名为my.ovpn,复制到刚刚建立的config文件夹中。接着编辑my.ovpn的内容,样例如下:

    ##############################################
    # 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.
    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.
    ;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.
    ;proto tcp
    proto udp

    # The hostname/IP and port of the server.
    # You can have multiple remote entries
    # to load balance between the servers.
    remote 服务器的IP 端口
    ;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.
    resolv-retry infinite

    # Most clients don't need to bind to
    # a specific local port number.
    nobind

    # Downgrade privileges after initialization (non-Windows only)
    ;user nobody
    ;group nobody

    # Try to preserve some state across restarts.
    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.
    ca server.crt
    cert client.crt
    key client.key

    # Verify server certificate by checking
    # that the certicate has the nsCertType
    # field set to "server".  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 nsCertType
    # field set to "server".  The build-key-server
    # script in the easy-rsa folder will do this.
    ns-cert-type server

    # If a tls-auth key is used on the server
    # then every client must also have the key.
    ;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.
    ;cipher x

    # 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.
    verb 3

    # Silence repeating messages
    ;mute 20

    把key.tar.gz解压缩,将里面的server.crt、client.crt、client.key三个文件复制到config目录下。

    然后,点击“开始”——OpenVPN——右击“OpenVPN GUI”,以管理员身份运行。右击托盘中的OpenVPN图标,选择“my”,选择“Connect”,稍等片刻就OK了。

    网络优化配置

    OpenVPN官方有一篇优化文章,但是针对LAN。另外还有一篇优化文章,比较有用。总结而言,就是在server.conf中加上(根据ipv4v4或ipv6自选):

    #Tweak for ipv4
    mssfix 1472

    #Tweak for ipv6
    #mssfix 1432

    客户端配置文件加上:

    #Tweak
    rcvbuf 65536

    常见问题1:无法链接OpenVPN服务器,确认是系统iptables挡住了。

    编辑/etc/sysconfig/iptables

    在适当位置加上:

    -A INPUT -p udp -m udp --dport 53 -j ACCEPT

    -A INPUT -p tcp -m tcp --dport 53 -j ACCEPT

    常见问题2:如果确认OpenVPN已经正常运行且正常连接情况下,如果无法连接外网,但可以连接内网,则可能是iptables问题。

    停止OpenVPN:

    /etc/init.d/openvpn stop

    编辑/etc/sysconfig/iptables

    在适当位置加上:

    -A INPUT -i tun+ -j ACCEPT

    -A OUTPUT -o tun+ -j ACCEPT

    -A FORWARD -i tun+ -o eth0 -j ACCEPT

    重启iptables:service iptables restart

    启动openvpn:

    /etc/init.d/openvpn start

    如果还有其它问题,请实际情况实际分析。

    分类: 所谓技术 | 标签: