Openvpn基于LDAP认证下进行包过滤（控制访问权限）

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1 说明

方案：采用minimal_pf.so模块和包过滤

此方法同样适用于基本认证。

参考资料：
http://backreference.org/2010/06/18/openvpns-built-in-packet-filter/

http://732233048.blog.51cto.com/9323668/1713088

https://blog.51cto.com/5766902/2132706?source=dra

2 安装openvpn及设置LDAP认证

详细步骤参考本站 openvpn部署之部署基于ad域认证访问内网

3 控制访问权限

3.1 创建及编辑minimal_pf.c模块

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[root@openvpn ~]# cd /etc/openvpn/

[root@openvpn openvpn]# vim minimal_pf.so

键入以下内容（内容固定）

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/* minimal_pf.c 
 * ultra-minimal OpenVPN plugin to enable internal packet filter */
#include <stdio.h>
#include <stdlib.h>
 
#include "include/openvpn-plugin.h"
 
/* dummy context, as we need no state */
struct plugin_context {
  int dummy;
};
 
/* Initialization function */
OPENVPN_EXPORT openvpn_plugin_handle_t openvpn_plugin_open_v1 (unsigned int *type_mask, const char *argv[], const char *envp[]) {
  struct plugin_context *context;
  /* Allocate our context */
  context = (struct plugin_context *) calloc (1, sizeof (struct plugin_context));
 
  /* Which callbacks to intercept. */
  *type_mask = OPENVPN_PLUGIN_MASK (OPENVPN_PLUGIN_ENABLE_PF);
 
  return (openvpn_plugin_handle_t) context;
}
 
/* Worker function */
OPENVPN_EXPORT int openvpn_plugin_func_v2 (openvpn_plugin_handle_t handle,
            const int type,
            const char *argv[],
            const char *envp[],
            void *per_client_context,
            struct openvpn_plugin_string_list **return_list) {
   
  if (type == OPENVPN_PLUGIN_ENABLE_PF) {
    return OPENVPN_PLUGIN_FUNC_SUCCESS;
  } else {
    /* should not happen! */
    return OPENVPN_PLUGIN_FUNC_ERROR;
  }
}
 
/* Cleanup function */
OPENVPN_EXPORT void openvpn_plugin_close_v1 (openvpn_plugin_handle_t handle) {
  struct plugin_context *context = (struct plugin_context *) handle;
  free (context);
}

3.2 构建插件

下载并解压OpenVPN源码压缩包（严格来说，只需要openvpn-plugin.h）

openvpn源码安装包：openvpn-2.3.11.tar.gz ，解压文件，复制include目录到/etc/openvpn`

并使用以下命令构建插件：

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INCLUDE="-I/etc/openvpn"         # CHANGE THIS!!!!
CC_FLAGS="-O2 -Wall -g"
NAME=minimal_pf
gcc $CC_FLAGS -fPIC -c $INCLUDE $NAME.c && \
gcc $CC_FLAGS -fPIC -shared -Wl,-soname,$NAME.so -o $NAME.so $NAME.o -lc

3.3 创建包过滤文件

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mkdir /etc/openvpn/ccd

cd /etc/openvpn/ccd

创建以用户名.pf命名的文件，输入以下内容。

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vi client1.pf             #客户client1，只对10.10.1.0网段有权限
[CLIENTS ACCEPT]
[SUBNETS DROP]
+10.10.1.0/24
[END]


vi client.pf              #客户client，对所有内网服务器都有权限
[CLIENTS ACCEPT]
[SUBNETS ACCEPT]
[END]

3.3.1 包过滤文件补充

包过滤文件格式：

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[CLIENTS DROP|ACCEPT]
{+|-}common_name1
{+|-}common_name2
 . . .
[SUBNETS DROP|ACCEPT]
{+|-}subnet1
{+|-}subnet2
 . . .
[END]


过滤文件语法：
CLIENTS部分用于定义common name；
SUBNETS部分用于定义IP地址、IP网段；
DROP|ACCEPT用于设置默认规则，就是没有明确指明的common name，那么他们将会使用；
{+|-}用于设置是否允许，如果是“+”，那么表示允许，如果是“-”则表示不允许；
[END]表示策略文件的结束


cat client10.pf
[CLIENTS ACCEPT]
[SUBNETS ACCEPT]
-192.168.9.7
+192.168.9.0/24
[END]

注意事项：

创建过滤文件时，允许访问的地址写到上面，禁止访问的地址写在后面。如果先禁止访问网段，在允许访问网段IP地址，依然受限。

例如：
图1

3.4 创建客户端连接脚本

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cd /etc/openvpn

vim client-connect.sh
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#!/bin/sh
 
# /etc/openvpn/client-connect.sh: sample client-connect script using pf rule files
 
# rules template file
template="/etc/openvpn/ccd/${common_name}.pf"
 
# create the file OpenVPN wants with the rules for this client
if [ -f "$template" ] && [ ! -z "$pf_file" ]; then
  cp -- "$template" "$pf_file"
else
  # if anything is not as expected, fail
  exit 1
fi

3.5 修改openvpn配置文件

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vim /etc/openvpn/server.conf
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ca /etc/openvpn/easy-rsa/keys/ca.crt
cert /etc/openvpn/easy-rsa/keys/server.crt
key /etc/openvpn/easy-rsa/keys/server.key
dh /etc/openvpn/easy-rsa/keys/dh2048.pem
server 10.8.0.0 255.255.255.0
ifconfig-pool-persist ipp.txt
;server-bridge 10.8.0.4 255.255.255.0 10.8.0.50 10.8.0.100
;push "redirect-gateway def1 bypass-dhcp"
;push "redirect-gateway"
;push "dhcp-option DNS 172.20.20.10"
;push "dhcp-option DNS 202.102.224.68"
;push "route 0.0.0.0 0.0.0.0"
push "route 172.20.20.0 255.255.255.0"
push "route 172.20.22.0 255.255.255.0"
push "route 172.20.10.0 255.255.255.0"
push "route 172.20.19.0 255.255.255.0"
push "route 10.224.255.224 255.255.255.224"
;push "route 172.20.18.0 255.255.255.0"
;push "route 172.20.17.0 255.255.255.0"
;push "dhcp-option DNS 172.20.20.10"
;push "dhcp-option DNS 202.102.224.68"
client-to-client
duplicate-cn
keepalive 10 120
#tls-auth /etc/openvpn/easy-rsa/ta.key 0
comp-lzo
max-clients 10
persist-key
persist-tun
status openvpn-status.log
log        /var/log/openvpn.log
log-append /var/log/openvpn-append.log
verb 3
plugin /usr/lib64/openvpn/plugin/lib/openvpn-auth-ldap.so "/etc/openvpn/auth/ldap.conf"
client-cert-not-required
username-as-common-name                     # 添加    
client-config-dir /etc/openvpn/ccd          #添加
plugin /etc/openvpn/minimal_pf.so           #添加                        
client-connect /etc/openvpn/client-connect.sh       #添加
script-security 3

例子：

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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.
port 1194

# TCP or UDP server?
# ;proto tcp
# proto udp
proto tcp

# "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 /etc/openvpn/server/ca.crt 
cert /etc/openvpn/server/server.crt
key /etc/openvpn/server/server.key  
# This file should be kept secret

# Diffie hellman parameters.
# Generate your own with:
#   openssl dhparam -out dh2048.pem 2048
# dh dh2048.pem
dh /etc/openvpn/server/dh.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.
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 logs/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"
push "route 192.168.0.0 255.255.255.0"
push "route 192.168.1.0 255.255.255.0"
# 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 114.114.114.114"

# 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.
# Note that v2.4 client/server will automatically
# negotiate AES-256-GCM in TLS mode.
# See also the ncp-cipher option in the manpage
cipher AES-256-CBC

# Enable compression on the VPN link and push the
# option to the client (v2.4+ only, for earlier
# versions see below)
;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
max-clients 30

# 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 logs/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
log logs/openvpn.log
log-append logs/openvpn-append.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

# Notify the client that when the server restarts so it
# can automatically reconnect.
# explicit-exit-notify 1

### LDAP认证
plugin /usr/lib64/openvpn/plugin/lib/openvpn-auth-ldap.so "/etc/openvpn/auth/ldap.conf"
# 关闭证书认证;不请求客户的CA证书，使用User/Pass验证
client-cert-not-required 

### 增加权限配置，包过滤规则(添加如下5项)
#添加,否则报错WARNING: External program may not be called unless '--script-security 2' or higher is enabled. See --help text or man page for detailed info.
script-security 3
#使用客户提供的UserName作为Common Name
username-as-common-name               
client-config-dir /etc/openvpn/ccd
plugin /etc/openvpn/include/minimal_pf.so                       
client-connect /etc/openvpn/include/client-connect.sh

3.6 重启openvpn服务器

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/etc/init.d/openvpn restart

配置完成。

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