CentOS Linux 安装IPSec+L2TP

第二层隧道协议L2TP(Layer 2 Tunneling Protocol)是一种工业标准的Internet隧道协议，它使用UDP的1701端口进行通信。L2TP本身并没有任何加密，但是我们可以使用IPSec对L2TP包进行加密。L2TP VPN比PPTP VPN搭建复杂一些。

环境说明：

[root@l2tp_server ~]# cat /etc/redhat-release
CentOS release 6.9 (Final)
[root@l2tp_server ~]# uname -r
2.6.-696.10..el6.x86_64

1、需要先添加epel源：

rpm -ivh https://mirrors.aliyun.com/epel/epel-release-latest-6.noarch.rpm

yum -y install openswan ppp xl2tpd        ##openswan是Linux系统上IPsec的一个实现 官网：http://www.openswan.org/

安装一些依赖包：

yum -y install make gcc gmp-devel bison flex lsof

2、配置IPsec

编辑配置文件/etc/ipsec.conf，只需要将最下面的"YOUR_SERVER_IP"改成你的公网IP即可：

[root@l2tp_server ~]# vim /etc/ipsec.conf 

# /etc/ipsec.conf - Libreswan IPsec configuration file

# This file:  /etc/ipsec.conf
#
# Enable when using this configuration file with openswan instead of libreswan
#version
#
# Manual:     ipsec.conf.

# basic configuration
config setup
    # which IPsec stack to use, "netkey" (the default), "klips" or "mast".
    # For MacOSX use "bsd"
    protostack=netkey
    #
    # Normally, pluto logs via syslog. If you want to log to a file,
    # specify below or to disable logging, eg for embedded systems, use
    # the file name /dev/null
    # Note: SElinux policies might prevent pluto writing to a log file at
    #       an unusual location.
    logfile=/var/log/pluto.log
    #
    # The interfaces= line is only required for the klips/mast stack
    #interfaces="%defaultroute"
    #interfaces="ipsec0=eth0 ipsec1=ppp0"
    #
    # If you want to limit listening on a single IP - not required for
    # normal operation
    #listen=127.0.0.1
    #
    # Do not set debug options to debug configuration issues!
    #
    # plutodebug / klipsdebug = "all", "none" or a combation from below:
    # "raw crypt parsing emitting control kernel pfkey natt x509 dpd
    #  private".
    # Note: "crypt" is not included with "all", as it can show confidential
    #       information. It must be specifically specified
    # examples:
    # plutodebug="control parsing"
    # plutodebug="all crypt"
    # Again: only enable plutodebug or klipsdebug when asked by a developer
    #plutodebug=none
    #klipsdebug=none
    #
    # Enable core dumps (might require system changes, like ulimit -C)
    # This is required for abrtd to work properly
    # Note: SElinux policies might prevent pluto writing the core at
    #       unusual locations
    dumpdir=/var/run/pluto/
    #
    # NAT-TRAVERSAL support
    # exclude networks used on server side by adding %v4:!a.b.c./
    # It seems that T-Mobile in the US and Rogers/Fido in Canada are
    # using / as "private" address space on their wireless networks.
    # This range has never been announced via BGP (at least upto )
    virtual_private=%v4:10.0.0.0/,%v4:192.168.1.0/,%v4:172.16.0.0/,%v6:fd00::/,%v6:fe80::/
# For example connections, see your distribution's documentation directory,
# or https://libreswan.org/wiki/
#
# There is also a lot of information in the manual page, "man ipsec.conf"
#
# It is best to add your IPsec connections as separate files in /etc/ipsec.d/
include /etc/ipsec.d/*.conf
conn L2TP-PSK-NAT
   rightsubnet=vhost:%priv
   also=L2TP-PSK-noNAT

conn L2TP-PSK-noNAT
   authby=secret
   pfs=no
   auto=add
   keyingtries=5
   rekey=no
   ikelifetime=8h
   keylife=1h
   type=transport
   left=YOUR_SERVER_IP
   leftprotoport=17/1701
   right=%any
   rightprotoport=17/%any

3、设置预共享密钥PSK

[root@l2tp_server ~]# vim /etc/ipsec.secrets
YOUR_SERVER_IP.ADDRESS %any: PSK "YourSharedSecret"

4、修改包转发设置

[root@l2tp_server ~]# for each in /proc/sys/net/ipv4/conf/*; do echo 0 > $each/accept_redirects; echo 0 > $each/send_redirects; done
[root@l2tp_server ~]# echo 1 >/proc/sys/net/core/xfrm_larval_drop

修改内核设置，使其支持转发，编辑/etc/sysctl.conf文件：

[root@l2tp_server ~]# sed -i 's/net.ipv4.ip_forward = 0/net.ipv4.ip_forward = 1/' /etc/sysctl.conf
[root@l2tp_server ~]# sysctl -p

5、启动IPsec

/etc/init.d/ipsec start

查看系统IPSec安装和启动的正确性：

[root@l2tp_server ~]# ipsec verify

Verifying installed system and configuration files

Version check and ipsec on-path [OK]
Libreswan 3.15 (netkey) on 2.6.32-696.10.1.el6.x86_64
Checking for IPsec support in kernel [OK]
NETKEY: Testing XFRM related proc values
ICMP default/send_redirects [OK]
ICMP default/accept_redirects [OK]
XFRM larval drop [OK]
Pluto ipsec.conf syntax [OK]
Hardware random device [N/A]
Two or more interfaces found, checking IP forwarding [OK]
Checking rp_filter [ENABLED]
/proc/sys/net/ipv4/conf/default/rp_filter [ENABLED]
/proc/sys/net/ipv4/conf/lo/rp_filter [ENABLED]
/proc/sys/net/ipv4/conf/eth0/rp_filter [ENABLED]
/proc/sys/net/ipv4/conf/ppp0/rp_filter [ENABLED]
rp_filter is not fully aware of IPsec and should be disabled
Checking that pluto is running [OK]
Pluto listening for IKE on udp 500 [OK]
Pluto listening for IKE/NAT-T on udp 4500 [OK]
Pluto ipsec.secret syntax [OK]
Checking 'ip' command [OK]
Checking 'iptables' command [OK]
Checking 'prelink' command does not interfere with FIPSChecking for obsolete ipsec.conf options [OK]
Opportunistic Encryption [DISABLED]

没有FAILD报错就可以/

6、安装L2TP(xl2tpd和rp-l2tp)  xl2tpd是由Xelerance Corporation维护的l2tpd应用。但是xl2tpd没有l2tp-control，需要从rp-l2tp这个里面提取。所以要装这两个软件包。

yum -y install libpcap-devel ppp policycoreutils    #依赖软件

安装xl2tpd和rp-l2tp：

[root@localhost ~]# cd /usr/local/src/

[root@localhost src]# wget http://sourceforge.net/projects/rp-l2tp/files/rp-l2tp/0.4/rp-l2tp-0.4.tar.gz

[root@localhost src]# tar -zxvf rp-l2tp-0.4.tar.gz
[root@localhost src]# cd rp-l2tp-0.4

[root@localhost rp-l2tp-0.4]# ./configure  && make 
[root@localhost rp-l2tp-0.4]# cp handlers/l2tp-control /usr/local/sbin/
[root@localhost rp-l2tp-0.4]# mkdir /var/run/xl2tpd/
[root@localhost rp-l2tp-0.4]# ln -s /usr/local/sbin/l2tp-control /var/run/xl2tpd/l2tp-control
##安装xl2tpd
[root@localhost ~]# cd /usr/local/src
[root@localhost src]# wget https://github.com/xelerance/xl2tpd/archive/v1.3.10.1.tar.gz
[root@localhost src]# tar xf v1.3.10.1.tar.gz && cd xl2tpd-1.3.10.1 && make && make install

7、编辑xl2tpd配置文件

[root@localhost ~]# mkdir /etc/xl2tpd/
[root@localhost ~]# vim /etc/xl2tpd/xl2tpd.conf

;
; This is a minimal sample xl2tpd configuration file for use
; with L2TP over IPsec.
;
; The idea is to provide an L2TP daemon to which remote Windows L2TP/IPsec
; clients connect. In this example, the internal (protected) network
; is 192.168.1.0/.  A special IP range within this network is reserved
; for the remote clients: 192.168.1.128/
; (i.e. 192.168.1.128 ... 192.168.1.254)
;
; The listen-addr parameter can be used if you want to bind the L2TP daemon
; to a specific IP address instead of to all interfaces. For instance,
; you could bind it to the interface of the internal LAN (e.g. 192.168.1.98
; in the example below). Yet another IP address (local ip, e.g. 192.168.1.99)
; will be used by xl2tpd as its address on pppX interfaces.

[global]
ipsec saref = yes
; listen-addr = 192.168.1.98
;
; requires openswan-2.5. or higher - Also does not yet work in combination
; with kernel mode l2tp as present in linux 2.6.+
; ipsec saref = yes
; Use refinfo of  if using an SAref kernel patch based on openswan 2.6. or
;  when using any of the SAref kernel patches for kernels up to 2.6..
; saref refinfo =
;
; force userspace = yes
;
; debug tunnel = yes

[lns default]
ip range = 192.168.20.2-192.168.20.220
local ip = 192.168.20.1
require chap = yes
refuse pap = yes
require authentication = yes
name = LinuxVPNserver
ppp debug = yes
pppoptfile = /etc/ppp/options.xl2tpd
length bit = yes

8、配置PPP

[root@localhost ~]# vim /etc/ppp/options.xl2tpd

require-mschap-v2
ms-dns 8.8.8.8
auth
mtu
mru
crtscts
hide-password
modem
lock
name l2tpd
proxyarp
lcp-echo-interval
lcp-echo-failure 

9、设置拨号用户名和密码

[root@localhost ~]# vim /etc/ppp/chap-secrets

   # Secrets for authentication using CHAP
   # client        server  secret                  IP addresses
       test        l2tpd                     *

10、以debug方式启动l2tp，查看有无错误：

[root@localhost ~]# xl2tpd -D
xl2tpd[]: Enabling IPsec SAref processing for L2TP transport mode SAs
xl2tpd[]: IPsec SAref does not work with L2TP kernel mode yet, enabling force userspace=yes
xl2tpd[]: setsockopt recvref[]: Protocol not available
xl2tpd[]: Not looking for kernel support.
xl2tpd[]: xl2tpd version xl2tpd-1.3.10.1 started on localhost.localdomain PID:
xl2tpd[]: Written by Mark Spencer, Copyright (C) , Adtran, Inc.
xl2tpd[]: Forked by Scott Balmos and David Stipp, (C)
xl2tpd[]: Inherited by Jeff McAdams, (C)
xl2tpd[]: Forked again by Xelerance (www.xelerance.com) (C) -
xl2tpd[]: Listening on IP address 0.0.0.0, port 

11、加入开机自启动

[root@localhost ~]# echo -e "/usr/local/sbin/xl2tpd\n/etc/init.d/ipsec restart\necho 1 >/proc/sys/net/core/xfrm_larval_drop"  >> /etc/rc.local 
[root@localhost ~]# echo  "for each in /proc/sys/net/ipv4/conf/*; do echo 0 > $each/accept_redirects; echo 0 > $each/send_redirects; done" >> /etc/rc.local 

12、添加iptables转发规则，如果服务端是在内网的话，需要在路由器上做1701端口的映射，以及添加到对应VPN网段的路由

iptables --table nat --append POSTROUTING --jump MASQUERADE
/etc/init.d/iptables save
/etc/init.d/iptables restart

13、Windows端连接配置：

14、Win 10 连接vpn 输入用户名密码后没有反应的解决办法

单击开始—>运行，键入regedit,点击确定找到下面的注册表项 HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Rasman\Parameters

在编辑菜单上，单击新建DWORD值

在名称框中键入“ProhibitIpSec”

在数值数据框中，键入1、然后确定’

继续找到下面的注册表项

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\PolicyAgent

新建一个DWORD类型的键AssumeUDPEncapsulationContextOnSendRule值为2

然后重启计算机。