前言

以前连接回公司,经常都是使用 OpenVPN、PPTP、L2TP 什么的,感觉不是很难用,但也说不上很好用。但是因为大家都知道的原因,在 iOS 上 OpenVPN 基本上无法正常下载,这对于公司员工来说就比较麻烦了,因为并不是每个人都需要科学上网的。后来无意中发现了 OpenConnect VPN Server,感觉还不错,后来就用到公司网络上了。使用过一段时间,就考虑把家里的 OpenWrt 也装一个,这样外出的时候连回家里管理 NAS 也方便些,便有了此文。

前期准备

  1. 首先,你得有个刷了 OpenWrt 的路由器,版本Chaos Calmer 15.05
  2. 自己配置好 DDNS 等服务器。
  3. (可选)花钱或者免费弄一个服务器 SSL/TLS 证书

开工

安装 ocserv 和 ddns

我是命令行粉丝,所以大部分工作在 Terminal 下完成。

opkg update
opkg install luci-app-ocserv
opkg install luci-app-ddns



装好后的效果如下:安装 Web 界面的ocserv和ddns,其实装ddns并不是为了真正的动态域名,而是ocserv的脚本会检测系统中是否有ddns,如果有的话,ocserv的配置脚本会自动把动态域名设置为true,如果喜欢自己改脚本的,也可以不装ddns,这样可以解决点空间。

修改配置文件

安装好后,系统会自动生成以下 7 个文件:

/etc/ocserv/ca.pem
/etc/ocserv/ca-key.pem
/etc/ocserv/server-cert.pem
/etc/ocserv/server-key.pem
/etc/ocserv/ocserv.conf.template
/etc/ocserv/pki/ca.tmpl
/etc/ocserv/pki/server.tmpl


一般来说 CA 相关的可以不用管,如果你找了如 StartSSL 签了免费的证书的话,用他们签名过的公私钥替换server-cert.pem和server-key.pem就好了。其中ca.pem是服务器的 CA 证书,ca-key.pem是私钥,server-cert.pem是服务器证书,server-key.pem是服务器私钥。

接下来修改模板文件ocserv.conf.template,这个可以在命令行中用 Vim 操作,也可以在 Web 界面来操作,比如:


以下为使用「证书」方式来进行身份验证的,所以直接忽略系统默认的plain认证方式,如果使用该方式可以参考文章最后的参考文献。最终的配置文件如下:

 
 
# User authentication method. Could be set multiple times and in that case 
# all should succeed. 
# Options: certificate, pam. 
auth = "certificate" 
#auth = "pam" 
# The gid-min option is used by auto-select-group option, in order to 
# select the minimum group ID. 
#auth = "pam[gid-min=1000]" 
# The plain option requires specifying a password file which contains 
# entries of the following format. 
# "username:groupname:encoded-password" 
# One entry must be listed per line, and 'ocpasswd' can be used 
# to generate password entries. 
#auth = "|AUTH|" 
# A banner to be displayed on clients 
#banner = "Welcome to OpenWRT" 
#isolate-workers = true 
# When the server has a dynamic DNS address (that may change), 
# should set that to true to ask the client to resolve again on 
# reconnects. 
listen-host-is-dyndns = |DYNDNS|
# Use listen-host to limit to specific IPs or to the IPs of a provided 
# hostname. 
#listen-host = [IP|HOSTNAME] 
# Limit the number of clients. Unset or set to zero for unlimited. 
#max-clients = 1024 
max-clients = |MAX_CLIENTS|
# Limit the number of client connections to one every X milliseconds 
# (X is the provided value). Set to zero for no limit. 
rate-limit-ms = 100 
# Limit the number of identical clients (i.e., users connecting 
# multiple times). Unset or set to zero for unlimited. 
max-same-clients = |MAX_SAME|
# TCP and UDP port number 
tcp-port = |PORT|
|UDP|udp-port = |PORT|
# Stats report time. The number of seconds after which each 
# worker process will report its usage statistics (number of 
# bytes transferred etc). This is useful when accounting like 
# radius is in use. 
#stats-report-time = 360 
# Keepalive in seconds 
keepalive = 32400 
# Dead peer detection in seconds. 
dpd = |DPD|
# Dead peer detection for mobile clients. The needs to 
# be much higher to prevent such clients being awaken too 
# often by the DPD messages, and save battery. 
# (clients that send the X-AnyConnect-Identifier-DeviceType) 
#mobile-dpd = 1800 
# MTU discovery (DPD must be enabled) 
try-mtu-discovery = false 
# The key and the certificates of the server 
# The key may be a file, or any URL supported by GnuTLS (e.g., 
# tpmkey:uuid=xxxxxxx-xxxx-xxxx-xxxx-xxxxxxxx;storage=user 
# or pkcs11:object=my-vpn-key;object-type=private) 
# 
# There may be multiple certificate and key pairs and each key 
# should correspond to the preceding certificate. 
server-cert = /etc/ocserv/server-cert.pem
server-key = /etc/ocserv/server-key.pem
# Diffie-Hellman parameters. Only needed if you require support 
# for the DHE ciphersuites (by default this server supports ECDHE). 
# Can be generated using: 
# certtool --generate-dh-params --outfile /path/to/dh.pem 
#dh-params = /path/to/dh.pem 
# If you have a certificate from a CA that provides an OCSP 
# service you may provide a fresh OCSP status response within 
# the TLS handshake. That will prevent the client from connecting 
# independently on the OCSP server. 
# You can update this response periodically using: 
# ocsptool --ask --load-cert=your_cert --load-issuer=your_ca --outfile response 
# Make sure that you replace the following file in an atomic way. 
#ocsp-response = /path/to/ocsp.der 
# In case PKCS #11 or TPM keys are used the PINs should be available 
# in files. The srk-pin-file is applicable to TPM keys only, and is the 
# storage root key. 
#pin-file = /path/to/pin.txt 
#srk-pin-file = /path/to/srkpin.txt 
# The Certificate Authority that will be used to verify 
# client certificates (public keys) if certificate authentication 
# is set. 
ca-cert = /etc/ocserv/ca.pem
# The object identifier that will be used to read the user ID in the client 
# certificate. The object identifier should be part of the certificate's DN 
# Useful OIDs are: 
#  CN = 2.5.4.3, UID = 0.9.2342.19200300.100.1.1 
cert-user-oid = 2.5.4.3 
# The object identifier that will be used to read the user group in the 
# client  certificate. The object identifier should be part of the certificate's 
# DN. Useful OIDs are: 
#  OU (organizational unit) = 2.5.4.11 
#cert-group-oid = 2.5.4.11 
# The revocation list of the certificates issued by the 'ca-cert' above. 
#crl = /etc/ocserv/crl.pem 
# Uncomment this to enable compression negotiation (LZS, LZ4). 
|COMPRESSION|compression = true 
# GnuTLS priority string 
tls-priorities = "NORMAL:%SERVER_PRECEDENCE:%COMPAT:-VERS-SSL3.0" 
# To enforce perfect forward secrecy (PFS) on the main channel. 
#tls-priorities = "NORMAL:%SERVER_PRECEDENCE:%COMPAT:-VERS-SSL3.0:-RSA" 
# The time (in seconds) that a client is allowed to stay connected prior 
# to authentication 
auth-timeout = 40 
# The time (in seconds) that a client is allowed to stay idle (no traffic) 
# before being disconnected. Unset to disable. 
#idle-timeout = 1200 
# The time (in seconds) that a mobile client is allowed to stay idle (no 
# traffic) before being disconnected. Unset to disable. 
#mobile-idle-timeout = 2400 
# The time (in seconds) that a client is not allowed to reconnect after 
# a failed authentication attempt. 
min-reauth-time = 360 
# Banning clients in ocserv works with a point system. IP addresses 
# that get a score over that configured number are banned for 
# min-reauth-time seconds. By default a wrong password attempt is 10 points, 
# a KKDCP POST is 1 point, and a connection is 1 point. Note that 
# due to difference processes being involved the count of points 
# will not be real-time precise. 
# 
# Score banning cannot be reliably used when receiving proxied connections 
# locally from an HTTP server (i.e., when listen-clear-file is used). 
# 
# Set to zero to disable. 
max-ban-score = 50 
# The time (in seconds) that all score kept for a client is reset. 
ban-reset-time = 300 
# In case you'd like to change the default points. 
#ban-points-wrong-password = 10 
#ban-points-connection = 1 
#ban-points-kkdcp = 1 
# Cookie timeout (in seconds) 
# which he can reconnect. That cookie will be invalided if not 
# used within this timeout value. On a user disconnection, that 
# cookie will also be active for this time amount prior to be 
# invalid. That should allow a reasonable amount of time for roaming 
# between different networks. 
cookie-timeout = 300 
# Whether roaming is allowed, i.e., if true a cookie is 
# restricted to a single IP address and cannot be re-used 
# from a different IP. 
deny-roaming = false 
# ReKey time (in seconds) 
# ocserv will ask the client to refresh keys periodically once 
# this amount of seconds is elapsed. Set to zero to disable. 
rekey-time = 172800 
# ReKey method 
# Valid options: ssl, new-tunnel 
#  ssl: Will perform an efficient rehandshake on the channel allowing 
#       a seamless connection during rekey. 
#  new-tunnel: Will instruct the client to discard and re-establish the channel. 
#       Use this option only if the connecting clients have issues with the ssl 
#       option. 
rekey-method = ssl
# Script to call when a client connects and obtains an IP 
# Parameters are passed on the environment. 
# REASON, USERNAME, GROUPNAME, HOSTNAME (the hostname selected by client), 
# DEVICE, IP_REAL (the real IP of the client), IP_LOCAL (the local IP 
# in the P-t-P connection), IP_REMOTE (the VPN IP of the client), 
# ID (a unique numeric ID); REASON may be "connect" or "disconnect". 
# These scripts are not needed if you have setup an interface for all vpns+ 
# devices. 
#connect-script = /usr/bin/ocserv-script 
#disconnect-script = /usr/bin/ocserv-script 
# UTMP 
use-utmp = false 
# Whether to enable support for the occtl tool (i.e., either through D-BUS, 
# or via a unix socket). 
use-occtl = true 
# socket file used for IPC with occtl. You only need to set that, 
# if you use more than a single servers. 
occtl-socket-file = /var/run/occtl.socket
# PID file. It can be overriden in the command line. 
pid-file = /var/run/ocserv.pid
# The default server directory. Does not require any devices present. 
chroot-dir = /var/lib/ocserv
# socket file used for IPC, will be appended with .PID 
# It must be accessible within the chroot environment (if any) 
#socket-file = /var/run/ocserv-socket 
socket-file = ocserv-socket
# The user the worker processes will be run as. It should be 
# unique (no other services run as this user). 
run-as-user = ocserv
run-as-group = ocserv
# Set the protocol-defined priority (SO_PRIORITY) for packets to 
# be sent. That is a number from 0 to 6 with 0 being the lowest 
# priority. Alternatively this can be used to set the IP Type- 
# Of-Service, by setting it to a hexadecimal number (e.g., 0x20). 
# This can be set per user/group or globally. 
#net-priority = 3 
# Set the VPN worker process into a specific cgroup. This is Linux 
# specific and can be set per user/group or globally. 
#cgroup = "cpuset,cpu:test" 
# 
# Network settings 
# 
# The name of the tun device 
device = vpns
# Whether the generated IPs will be predictable, i.e., IP stays the 
# same for the same user when possible. 
predictable-ips = |PREDICTABLE_IPS|
# The default domain to be advertised 
|ENABLE_DEFAULT_DOMAIN|default-domain = |DEFAULT_DOMAIN|
# The pool of addresses that leases will be given from. 
ipv4-network = |IPV4ADDR|
ipv4-netmask = |NETMASK|
# The advertized DNS server. Use multiple lines for 
# multiple servers. 
# dns = fc00::4be0 
#dns = 192.168.1.2 
# The NBNS server (if any) 
#nbns = 192.168.1.3 
# The IPv6 subnet that leases will be given from. 
|ENABLE_IPV6|ipv6-network = |IPV6ADDR|
|ENABLE_IPV6|ipv6-prefix = |IPV6PREFIX|
# The domains over which the provided DNS should be used. Use 
# multiple lines for multiple domains. 
#split-dns = example.com 
# Prior to leasing any IP from the pool ping it to verify that 
# it is not in use by another (unrelated to this server) host. 
ping-leases = false 
# Unset to assign the default MTU of the device 
# mtu = 
# Unset to enable bandwidth restrictions (in bytes/sec). The 
# setting here is global, but can also be set per user or per group. 
#rx-data-per-sec = 40000 
#tx-data-per-sec = 40000 
# The number of packets (of MTU size) that are available in 
# the output buffer. The default is low to improve latency. 
# Setting it higher will improve throughput. 
#output-buffer = 10 
# Routes to be forwarded to the client. If you need the 
# client to forward routes to the server, you may use the 
# config-per-user/group or even connect and disconnect scripts. 
# 
# To set the server as the default gateway for the client just 
# comment out all routes from the server. 
#route = 192.168.1.0/255.255.255.0 
#route = 192.168.5.0/255.255.255.0 
#route = fef4:db8:1000:1001::/64 
# Configuration files that will be applied per user connection or 
# per group. Each file name on these directories must match the username 
# or the groupname. 
# The options allowed in the configuration files are dns, nbns, 
#  ipv?-network, ipv4-netmask, ipv6-prefix, rx/tx-per-sec, iroute, route, 
#  net-priority and cgroup. 
# 
# Note that the 'iroute' option allows to add routes on the server 
# based on a user or group. The syntax depends on the input accepted 
# by the commands route-add-cmd and route-del-cmd (see below). 
config-per-user = /etc/ocserv/config-per-user/
config-per-group = /etc/ocserv/config-per-group/
# When config-per-xxx is specified and there is no group or user that 
# matches, then utilize the following configuration. 
#default-user-config = /etc/ocserv/defaults/user.conf 
#default-group-config = /etc/ocserv/defaults/group.conf 
# Groups that a client is allowed to select from. 
# A client may belong in multiple groups, and in certain use-cases 
# it is needed to switch between them. For these cases the client can 
# select prior to authentication. Add multiple entries for multiple groups. 
#select-group = group1 
#select-group = group2[My group 2] 
#select-group = tost[The tost group] 
# The name of the group that if selected it would allow to use 
# the assigned by default group. 
#default-select-group = DEFAULT 
# Instead of specifying manually all the allowed groups, you may instruct 
# ocserv to scan all available groups and include the full list. That 
# option is only functional on plain authentication. 
#auto-select-group = true 
# The system command to use to setup a route. %{R} will be replaced with the 
# route/mask and %{D} with the (tun) device. 
# 
# The following example is from linux systems. %{R} should be something 
# like 192.168.2.0/24 
route-add-cmd = "/sbin/route add -net %{R} dev %{D}" 
route-del-cmd = "/sbin/route del -net %{R} dev %{D}" 
# This option allows to forward a proxy. The special strings '%{U}' 
# and '%{G}', if present will be replaced by the username and group name. 
#proxy-url = http://example.com/ 
#proxy-url = http://example.com/%{U}/%{G}/hello 
# 
# The following options are for (experimental) AnyConnect client 
# compatibility. 
# Client profile xml. A sample file exists in doc/profile.xml. 
# This file must be accessible from inside the worker's chroot. 
# It is not used by the openconnect client. 
#user-profile = profile.xml 
# Binary files that may be downloaded by the CISCO client. Must 
# be within any chroot environment. 
#binary-files = /path/to/binaries 
# Unless set to false it is required for clients to present their 
# certificate even if they are authenticating via a previously granted 
# cookie and complete their authentication in the same TCP connection. 
# Legacy CISCO clients do not do that, and thus this option should be 
# set for them. 
cisco-client-compat = |CISCO_COMPAT|
#Advanced options 
# Option to allow sending arbitrary custom headers to the client after 
# authentication and prior to VPN tunnel establishment. 
#custom-header = "X-My-Header: hi there" 

主要的改动点:

  1. 认证方式修改为 certificate
  2. 禁用 banner
  3. 打开 ca-cert
  4. 将 cert-user-oid 修改为 CN (2.5.4.3) 识别

当ocserv服务启动的时候,会自动生成/var/etc/ocserv.conf文件作为最终的配置文件。

设置路由表、转发规则和端口映射

修改完配置文件以后,我们还需要设置路由表。因为我不需要 OpenWrt 代理所有流量,仅仅需要可以访问到内网,所以我只做了一个路由表,就是我的内网网段,如下图:


接下来添加自定义防火墙,或修改 firewall 文件/etc/firewall.user,增加如下内容:

iptables -A input_rule -i vpns+ -j ACCEPT
iptables -A forwarding_rule -i vpns+ -j ACCEPT
iptables -A forwarding_rule -o vpns+ -j ACCEPT
iptables -A output_rule -o vpns+ -j ACCEPT

添加防火墙规则后重启服务。


最后 在防火墙-添加通信规则,ocserv安装后默认使用4443端口,如图:

启动 ocserv 服务

/etc/init.d/ocserv enable
/etc/init.d/ocserv start

				
				
				
				
				
				
这个命令很简单,另外,也可以在 luci 中选择Enable server来打开ocserv服务。然而,在你重启后,ocserv服务从来就没有自动启动过!!!所以,我们还得做些 tweaking。


在/etc/rc.local文件的exit前面增加两行:

/etc/init.d/ocserv restart
sleep 5

同时创建一个/root/ocservup.sh脚本,防止ocserv进程意外被杀:


#!/bin/sh 
killall -0 ocserv 2> /dev/null
if [ $? != 0 ]
then 
logger \"$0: Starting ocserv ...\" 
/usr/sbin/ocserv -c /var/etc/ocserv.conf
else
logger \"$0: ocserv already running: $(pidof ocserv)\"
fi

记得执行chmod +x /root/ocservup.sh给该脚本添加可执行属性。然后把该脚本添加到crontab中:


3 */2 * * * /root/ocservup.sh

至此,整个配置完成,可以重启试试。


参考文献