jenkins-metasploit
95 lines
67 KiB
HTML
95 lines
67 KiB
HTML
<!DOCTYPE html><html lang="en-US"><head><meta charset="UTF-8"><meta http-equiv="X-UA-Compatible" content="IE=Edge"><link rel="shortcut icon" href="/assets/images/favicon.png" type="image/x-icon"><link rel="stylesheet" href="/assets/css/just-the-docs-default.css"> <script async src="https://www.googletagmanager.com/gtag/js?id=UA-4622520-7"></script> <script> window.dataLayer = window.dataLayer || []; function gtag(){dataLayer.push(arguments);} gtag('js', new Date()); gtag('config', 'UA-4622520-7', { 'anonymize_ip': true }); </script> <script type="text/javascript" src="/assets/js/vendor/lunr.min.js"></script> <script src="https://cdn.jsdelivr.net/npm/mermaid@10.8.0/dist/mermaid.min.js"></script> <script type="text/javascript" src="/assets/js/just-the-docs.js"></script><meta name="viewport" content="width=device-width, initial-scale=1"><title>JavaScript Obfuscation | Metasploit Documentation Penetration Testing Software, Pen Testing Security</title><meta name="generator" content="Jekyll 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href="/docs/pentesting/metasploit-guide-mssql.html" class="nav-list-link">MSSQL</a><li class="nav-list-item active"><a href="/docs/pentesting/metasploit-guide-ldap.html" class="nav-list-link">LDAP</a><li class="nav-list-item active"><a href="#" class="nav-list-expander"><svg viewBox="0 0 24 24"><use xlink:href="#svg-arrow-right"></use></svg></a><a href="/docs/pentesting/active-directory/" class="nav-list-link">Active Directory</a><ul class="nav-list"><li class="nav-list-item active"><a href="#" class="nav-list-expander"><svg viewBox="0 0 24 24"><use xlink:href="#svg-arrow-right"></use></svg></a><a href="/docs/pentesting/active-directory/ad-certificates/" class="nav-list-link">AD CS</a><ul class="nav-list"><li class="nav-list-item active"><a href="/docs/pentesting/active-directory/ad-certificates/overview.html" class="nav-list-link">Overview</a><li class="nav-list-item active"><a href="/docs/pentesting/active-directory/ad-certificates/attacking-ad-cs-esc-vulnerabilities.html" class="nav-list-link">Attacking AD CS ESC Vulnerabilities Using Metasploit</a><li class="nav-list-item active"><a href="/docs/pentesting/active-directory/ad-certificates/ldap_esc_vulnerable_cert_finder.html" class="nav-list-link">Vulnerable cert finder</a><li class="nav-list-item active"><a href="/docs/pentesting/active-directory/ad-certificates/ad_cs_cert_template.html" class="nav-list-link">Manage certificate templates</a><li class="nav-list-item active"><a href="/docs/pentesting/active-directory/ad-certificates/icpr_cert.html" class="nav-list-link">Request certificates</a></ul><li class="nav-list-item active"><a href="#" class="nav-list-expander"><svg viewBox="0 0 24 24"><use xlink:href="#svg-arrow-right"></use></svg></a><a href="/docs/pentesting/active-directory/kerberos/" class="nav-list-link">Kerberos</a><ul class="nav-list"><li class="nav-list-item active"><a href="/docs/pentesting/active-directory/kerberos/overview.html" class="nav-list-link">Overview</a><li class="nav-list-item active"><a href="/docs/pentesting/active-directory/kerberos/service_authentication.html" class="nav-list-link">Authenticating to SMB/WinRM/etc</a><li class="nav-list-item active"><a href="/docs/pentesting/active-directory/kerberos/kerberos_login.html" class="nav-list-link">Kerberos login enumeration and bruteforcing</a><li class="nav-list-item active"><a href="/docs/pentesting/active-directory/kerberos/get_ticket.html" class="nav-list-link">Get Ticket granting tickets and service tickets</a><li class="nav-list-item active"><a href="/docs/pentesting/active-directory/kerberos/ticket_converter.html" class="nav-list-link">Converting kirbi and ccache files</a><li class="nav-list-item active"><a href="/docs/pentesting/active-directory/kerberos/forge_ticket.html" class="nav-list-link">Forging tickets</a><li class="nav-list-item active"><a href="/docs/pentesting/active-directory/kerberos/inspect_ticket.html" class="nav-list-link">Inspecting tickets</a><li class="nav-list-item active"><a href="/docs/pentesting/active-directory/kerberos/kerberoasting.html" class="nav-list-link">Kerberoasting</a><li class="nav-list-item active"><a href="/docs/pentesting/active-directory/kerberos/keytab.html" class="nav-list-link">Keytab support and decrypting wireshark traffic</a><li class="nav-list-item active"><a href="/docs/pentesting/active-directory/kerberos/rbcd.html" class="nav-list-link">Resource-based constrained delegation (RBCD)</a><li class="nav-list-item active"><a href="/docs/pentesting/active-directory/kerberos/unconstrained_delegation.html" class="nav-list-link">Unconstrained delegation</a></ul></ul></ul><li class="nav-list-item active"><a href="#" class="nav-list-expander"><svg viewBox="0 0 24 24"><use xlink:href="#svg-arrow-right"></use></svg></a><a href="/docs/using-metasploit/" class="nav-list-link">Using Metasploit</a><ul class="nav-list"><li class="nav-list-item active"><a href="#" class="nav-list-expander"><svg viewBox="0 0 24 24"><use xlink:href="#svg-arrow-right"></use></svg></a><a href="/docs/using-metasploit/getting-started/" class="nav-list-link">Getting Started</a><ul class="nav-list"><li class="nav-list-item active"><a href="/docs/using-metasploit/getting-started/nightly-installers.html" class="nav-list-link">Nightly Installers</a><li class="nav-list-item active"><a href="/docs/using-metasploit/getting-started/reporting-a-bug.html" class="nav-list-link">Reporting a Bug</a></ul><li class="nav-list-item active"><a href="#" class="nav-list-expander"><svg viewBox="0 0 24 24"><use xlink:href="#svg-arrow-right"></use></svg></a><a href="/docs/using-metasploit/basics/" class="nav-list-link">Basics</a><ul class="nav-list"><li class="nav-list-item active"><a href="/docs/using-metasploit/basics/using-metasploit.html" class="nav-list-link">Running modules</a><li class="nav-list-item active"><a href="/docs/using-metasploit/basics/how-to-use-a-metasploit-module-appropriately.html" class="nav-list-link">How to use a Metasploit module appropriately</a><li class="nav-list-item active"><a href="/docs/using-metasploit/basics/how-payloads-work.html" class="nav-list-link">How payloads work</a><li class="nav-list-item active"><a href="/docs/using-metasploit/basics/module-documentation.html" class="nav-list-link">Module Documentation</a><li class="nav-list-item active"><a href="/docs/using-metasploit/basics/how-to-use-a-reverse-shell-in-metasploit.html" class="nav-list-link">How to use a reverse shell in Metasploit</a><li class="nav-list-item active"><a href="/docs/using-metasploit/basics/how-to-use-msfvenom.html" class="nav-list-link">How to use msfvenom</a><li class="nav-list-item active"><a href="/docs/using-metasploit/basics/managing-sessions.html" class="nav-list-link">Managing Sessions</a></ul><li class="nav-list-item active"><a href="#" class="nav-list-expander"><svg viewBox="0 0 24 24"><use xlink:href="#svg-arrow-right"></use></svg></a><a href="/docs/using-metasploit/intermediate/" class="nav-list-link">Intermediate</a><ul class="nav-list"><li class="nav-list-item active"><a href="/docs/using-metasploit/intermediate/metasploit-database-support.html" class="nav-list-link">Database Support</a><li class="nav-list-item active"><a href="/docs/using-metasploit/intermediate/evading-anti-virus.html" class="nav-list-link">Evading Anti Virus</a><li class="nav-list-item active"><a href="/docs/using-metasploit/intermediate/exploit-ranking.html" class="nav-list-link">Exploit Ranking</a><li class="nav-list-item active"><a href="/docs/using-metasploit/intermediate/hashes-and-password-cracking.html" class="nav-list-link">Hashes and Password Cracking</a><li class="nav-list-item active"><a href="/docs/using-metasploit/intermediate/how-to-use-plugins.html" class="nav-list-link">Metasploit Plugins</a><li class="nav-list-item active"><a href="/docs/using-metasploit/intermediate/payload-uuid.html" class="nav-list-link">Payload UUID</a><li class="nav-list-item active"><a href="/docs/using-metasploit/intermediate/pivoting-in-metasploit.html" class="nav-list-link">Pivoting in Metasploit</a><li class="nav-list-item active"><a href="/docs/using-metasploit/intermediate/running-private-modules.html" class="nav-list-link">Running Private Modules</a></ul><li class="nav-list-item active"><a href="#" class="nav-list-expander"><svg viewBox="0 0 24 24"><use xlink:href="#svg-arrow-right"></use></svg></a><a href="/docs/using-metasploit/advanced/" class="nav-list-link">Advanced</a><ul class="nav-list"><li class="nav-list-item active"><a href="/docs/using-metasploit/advanced/how-to-configure-dns.html" class="nav-list-link">How to Configure DNS</a><li class="nav-list-item active"><a href="/docs/using-metasploit/advanced/metasploit-web-service.html" class="nav-list-link">Metasploit Web Service</a><li class="nav-list-item active"><a href="#" class="nav-list-expander"><svg viewBox="0 0 24 24"><use xlink:href="#svg-arrow-right"></use></svg></a><a href="/docs/using-metasploit/advanced/meterpreter/" class="nav-list-link">Meterpreter</a><ul class="nav-list"><li class="nav-list-item active"><a href="/docs/using-metasploit/advanced/meterpreter/meterpreter.html" class="nav-list-link">Overview</a><li class="nav-list-item active"><a href="/docs/using-metasploit/advanced/meterpreter/meterpreter-configuration.html" class="nav-list-link">Configuration</a><li class="nav-list-item active"><a href="/docs/using-metasploit/advanced/meterpreter/debugging-dead-meterpreter-sessions.html" class="nav-list-link">Debugging Dead Meterpreter Sessions</a><li class="nav-list-item active"><a href="/docs/using-metasploit/advanced/meterpreter/meterpreter-debugging-meterpreter-sessions.html" class="nav-list-link">Debugging Meterpreter Sessions</a><li class="nav-list-item active"><a href="/docs/using-metasploit/advanced/meterpreter/meterpreter-executebof-command.html" class="nav-list-link">ExecuteBof Command</a><li class="nav-list-item active"><a href="/docs/using-metasploit/advanced/meterpreter/meterpreter-http-communication.html" class="nav-list-link">HTTP Communication</a><li class="nav-list-item active"><a href="/docs/using-metasploit/advanced/meterpreter/how-to-get-started-with-writing-a-meterpreter-script.html" class="nav-list-link">How to get started with writing a Meterpreter script</a><li class="nav-list-item active"><a href="/docs/using-metasploit/advanced/meterpreter/meterpreter-paranoid-mode.html" class="nav-list-link">Paranoid Mode</a><li class="nav-list-item active"><a href="/docs/using-metasploit/advanced/meterpreter/powershell-extension.html" class="nav-list-link">Powershell Extension</a><li class="nav-list-item active"><a href="/docs/using-metasploit/advanced/meterpreter/python-extension.html" class="nav-list-link">Python Extension</a><li class="nav-list-item active"><a href="/docs/using-metasploit/advanced/meterpreter/meterpreter-reg-command.html" class="nav-list-link">Reg Command</a><li class="nav-list-item active"><a href="/docs/using-metasploit/advanced/meterpreter/meterpreter-reliable-network-communication.html" class="nav-list-link">Reliable Network Communication</a><li class="nav-list-item active"><a href="/docs/using-metasploit/advanced/meterpreter/meterpreter-sleep-control.html" class="nav-list-link">Sleep Control</a><li class="nav-list-item active"><a href="/docs/using-metasploit/advanced/meterpreter/meterpreter-stageless-mode.html" class="nav-list-link">Stageless Mode</a><li class="nav-list-item active"><a href="/docs/using-metasploit/advanced/meterpreter/the-ins-and-outs-of-http-and-https-communications-in-meterpreter-and-metasploit-stagers.html" class="nav-list-link">The ins and outs of HTTP and HTTPS communications in Meterpreter and Metasploit Stagers</a><li class="nav-list-item active"><a href="/docs/using-metasploit/advanced/meterpreter/meterpreter-timeout-control.html" class="nav-list-link">Timeout Control</a><li class="nav-list-item active"><a href="/docs/using-metasploit/advanced/meterpreter/meterpreter-transport-control.html" class="nav-list-link">Transport Control</a><li class="nav-list-item active"><a href="/docs/using-metasploit/advanced/meterpreter/meterpreter-unicode-support.html" class="nav-list-link">Unicode Support</a><li class="nav-list-item active"><a href="/docs/using-metasploit/advanced/meterpreter/meterpreter-wishlist.html" class="nav-list-link">Wishlist</a></ul><li class="nav-list-item active"><a href="#" class="nav-list-expander"><svg viewBox="0 0 24 24"><use xlink:href="#svg-arrow-right"></use></svg></a><a href="/docs/using-metasploit/advanced/RPC/" class="nav-list-link">RPC</a><ul class="nav-list"><li class="nav-list-item active"><a href="/docs/using-metasploit/advanced/RPC/how-to-use-metasploit-json-rpc.html" class="nav-list-link">How to use Metasploit JSON RPC</a><li class="nav-list-item active"><a href="/docs/using-metasploit/advanced/RPC/how-to-use-metasploit-messagepack-rpc.html" class="nav-list-link">How to use Metasploit Messagepack RPC</a></ul></ul><li class="nav-list-item active"><a href="#" class="nav-list-expander"><svg viewBox="0 0 24 24"><use xlink:href="#svg-arrow-right"></use></svg></a><a href="/docs/using-metasploit/other/" class="nav-list-link">Other</a><ul class="nav-list"><li class="nav-list-item active"><a href="/docs/using-metasploit/other/how-to-use-metasploit-mcp-server.html" class="nav-list-link">How to use Metasploit MCP Server</a><li class="nav-list-item active"><a href="/docs/using-metasploit/other/how-to-use-metasploit-with-ngrok.html" class="nav-list-link">How to use Metasploit with ngrok</a><li class="nav-list-item active"><a href="/docs/using-metasploit/other/how-to-use-the-favorite-command.html" class="nav-list-link">How to use the Favorite command</a><li class="nav-list-item active"><a href="/docs/using-metasploit/other/information-about-unmet-browser-exploit-requirements.html" class="nav-list-link">Information About Unmet Browser Exploit Requirements</a><li class="nav-list-item active"><a href="#" class="nav-list-expander"><svg viewBox="0 0 24 24"><use xlink:href="#svg-arrow-right"></use></svg></a><a href="/docs/using-metasploit/other/oracle-support/" class="nav-list-link">Oracle Support</a><ul class="nav-list"><li class="nav-list-item active"><a href="/docs/using-metasploit/other/oracle-support/how-to-get-oracle-support-working-with-kali-linux.html" class="nav-list-link">How to get Oracle Support working with Kali Linux</a><li class="nav-list-item active"><a href="/docs/using-metasploit/other/oracle-support/oracle-usage.html" class="nav-list-link">Oracle Usage</a></ul><li class="nav-list-item active"><a href="/docs/using-metasploit/other/why-cve-is-not-available.html" class="nav-list-link">Why CVE is not available</a></ul></ul><li class="nav-list-item active"><a href="#" class="nav-list-expander"><svg viewBox="0 0 24 24"><use xlink:href="#svg-arrow-right"></use></svg></a><a href="/docs/development/" class="nav-list-link active">Development</a><ul class="nav-list"><li class="nav-list-item active"><a href="#" class="nav-list-expander"><svg viewBox="0 0 24 24"><use xlink:href="#svg-arrow-right"></use></svg></a><a href="/docs/development/get-started/" class="nav-list-link">Get Started</a><ul class="nav-list"><li class="nav-list-item active"><a href="/docs/development/get-started/contributing-to-metasploit.html" class="nav-list-link">Contributing to Metasploit</a><li class="nav-list-item active"><a href="/docs/development/get-started/creating-your-first-pr.html" class="nav-list-link">Creating Your First PR</a><li class="nav-list-item active"><a href="/docs/development/get-started/setting-up-a-metasploit-development-environment.html" class="nav-list-link">Setting Up a Metasploit Development Environment</a><li class="nav-list-item active"><a href="/docs/development/get-started/sanitizing-pcaps.html" class="nav-list-link">Sanitizing PCAPs</a><li class="nav-list-item active"><a href="#" 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href="/docs/development/get-started/navigating-and-understanding-metasploits-codebase.html" class="nav-list-link">Navigating the codebase</a></ul><li class="nav-list-item active"><a href="#" class="nav-list-expander"><svg viewBox="0 0 24 24"><use xlink:href="#svg-arrow-right"></use></svg></a><a href="/docs/development/developing-modules/" class="nav-list-link active">Developing Modules</a><ul class="nav-list"><li class="nav-list-item active"><a href="#" class="nav-list-expander"><svg viewBox="0 0 24 24"><use xlink:href="#svg-arrow-right"></use></svg></a><a href="/docs/development/developing-modules/guides/" class="nav-list-link">Guides</a><ul class="nav-list"><li class="nav-list-item active"><a href="#" class="nav-list-expander"><svg viewBox="0 0 24 24"><use xlink:href="#svg-arrow-right"></use></svg></a><a href="/docs/development/developing-modules/guides/scanners/" class="nav-list-link">Scanners</a><ul class="nav-list"><li class="nav-list-item active"><a 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class="nav-list-link">ReflectiveDLL Injection</a><li class="nav-list-item active"><a href="/docs/development/developing-modules/libraries/how-to-do-reporting-or-store-data-in-module-development.html" class="nav-list-link">Reporting and Storing Data</a><li class="nav-list-item active"><a href="/docs/development/developing-modules/libraries/how-to-use-the-seh-mixin-to-exploit-an-exception-handler.html" class="nav-list-link">SEH Exploitation</a><li class="nav-list-item active"><a href="#" class="nav-list-expander"><svg viewBox="0 0 24 24"><use xlink:href="#svg-arrow-right"></use></svg></a><a href="/docs/development/developing-modules/libraries/smb_library/" class="nav-list-link">SMB Library</a><ul class="nav-list"><li class="nav-list-item active"><a href="/docs/development/developing-modules/libraries/smb_library/guidelines-for-writing-modules-with-smb.html" class="nav-list-link">Guidelines for Writing Modules with SMB</a><li class="nav-list-item active"><a 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class="breadcrumb-nav-list-item"> <span>JavaScript Obfuscation</span></ol></nav><div id="main-content" class="main-content" role="main"><p>Stealth is an important feature to think about during exploit development. If your exploit gets caught all the time, it doesn’t matter how awesome or how technically challenging your exploit is, it is most likely not very usable in a real penetration test. Browser exploits in particular, heavily rely on JavaScript to trigger vulnerabilities, therefore a lot of antivirus or signature-based intrusion detection/prevention systems will scan the JavaScript and flag specific lines as malicious. The following code used to be considered as MS12-063 by multiple <a href="https://www.virustotal.com/en/file/90fdf2beab48cf3c269f70d8c9cf7736f3442430ea023d06b65ff073f724870e/analysis/1388888489/">antivirus vendors</a> even though it is not necessarily harmful or malicious, we’ll use this as an example throughout the wiki:</p><div class="language-javascript highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="kd">var</span> <span class="nx">arrr</span> <span class="o">=</span> <span class="k">new</span> <span class="nc">Array</span><span class="p">();</span>
|
||
<span class="nx">arrr</span><span class="p">[</span><span class="mi">0</span><span class="p">]</span> <span class="o">=</span> <span class="nx">windows</span><span class="p">.</span><span class="nb">document</span><span class="p">.</span><span class="nf">createElement</span><span class="p">(</span><span class="dl">"</span><span class="s2">img</span><span class="dl">"</span><span class="p">);</span>
|
||
<span class="nx">arrr</span><span class="p">[</span><span class="mi">0</span><span class="p">][</span><span class="dl">"</span><span class="s2">src</span><span class="dl">"</span><span class="p">]</span> <span class="o">=</span> <span class="dl">"</span><span class="s2">a</span><span class="dl">"</span><span class="p">;</span>
|
||
</code></pre></div></div><p>To avoid getting flagged, there are some common evasive tricks we can try. For example, you can manually modify the code a little bit to make it not recognizable by any signatures. Or if the antivirus relies on cached webpages to scan for exploits, it is possible to make the browser not cache your exploit so you stay undetected. Or in this case, you can obfuscate your code, which is what this writeup will focus on.</p><p>In Metasploit, there are three common ways to obfuscate your JavaScript. The first one is simply by using the <code class="language-plaintext highlighter-rouge">rand_text_alpha</code> method (in <a href="https://github.com/rapid7/rex-text/blob/3bb11cb5c9997096a82a4e160fcb31c152385a9a/lib/rex/text/rand.rb#L127-L132">Rex</a>) to randomize your variables. The second one is by using the <a href="https://github.com/rapid7/rex-exploitation/blob/f3058a0737ba89fd116f99a8381a409bba6a53fa/lib/rex/exploitation/obfuscatejs.rb">ObfuscateJS</a> class. And the third option is the <a href="https://github.com/rapid7/rex-exploitation/blob/f3058a0737ba89fd116f99a8381a409bba6a53fa/lib/rex/exploitation/jsobfu.rb">JSObfu</a> class.</p><h2 id="the-rand_text_alpha-trick"> <a href="#the-rand_text_alpha-trick" class="anchor-heading" aria-labelledby="the-rand_text_alpha-trick"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> The rand_text_alpha trick</h2><p>Using <code class="language-plaintext highlighter-rouge">rand_text_alpha</code> is the most basic form of evasion, but also the least effective. If this is your choice, you should randomize whatever can be randomized without breaking the code.</p><p>By using the above MS12-063, here’s how you would use <code class="language-plaintext highlighter-rouge">rand_text_alpha</code>:</p><div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="c1"># Randomizes the array variable</span>
|
||
<span class="c1"># Max size = 6, Min = 3</span>
|
||
<span class="n">var_array</span> <span class="o">=</span> <span class="n">rand_text_alpha</span><span class="p">(</span><span class="nb">rand</span><span class="p">(</span><span class="mi">6</span><span class="p">)</span> <span class="o">+</span> <span class="mi">3</span><span class="p">)</span>
|
||
|
||
<span class="c1"># Randomizes the src value</span>
|
||
<span class="n">val_src</span> <span class="o">=</span> <span class="n">rand_text_alpha</span><span class="p">(</span><span class="mi">1</span><span class="p">)</span>
|
||
|
||
<span class="n">js</span> <span class="o">=</span> <span class="sx">%Q|
|
||
var </span><span class="si">#{</span><span class="n">var_array</span><span class="si">}</span><span class="sx"> = new Array();
|
||
</span><span class="si">#{</span><span class="n">var_array</span><span class="si">}</span><span class="sx">[0] = windows.document.createElement("img");
|
||
</span><span class="si">#{</span><span class="n">var_array</span><span class="si">}</span><span class="sx">[0]["src"] = "</span><span class="si">#{</span><span class="n">val_src</span><span class="si">}</span><span class="sx">";
|
||
|</span>
|
||
</code></pre></div></div><h2 id="the-obfuscatejs-class"> <a href="#the-obfuscatejs-class" class="anchor-heading" aria-labelledby="the-obfuscatejs-class"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> The ObfuscateJS class</h2><p>The ObfuscateJS class is like the <code class="language-plaintext highlighter-rouge">rand_text_alpha</code> technique on steroids, but even better. It allows you to replace symbol names such as variables, methods, classes, and namespaces. It can also obfuscate strings by either randomly using <code class="language-plaintext highlighter-rouge">fromCharCode</code> or <code class="language-plaintext highlighter-rouge">unescape</code>. And lastly, it can strip JavaScript comments, which is handy because exploits often are hard to understand and read so you need comments to remember why something is written in a specific way, but you don’t want to show or leak those comments in a pentest.</p><p>To use ObfuscateJS, let’s use the MS12-063 example again to demonstrate. If you feel like following the steps yourself without writing a module, what you can do is go ahead and run <code class="language-plaintext highlighter-rouge">msfconsole</code>, and then switch to irb, like this:</p><div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>$ ./msfconsole -q
|
||
msf > irb
|
||
[*] Starting IRB shell...
|
||
|
||
>>
|
||
</code></pre></div></div><p>And then you are ready to go.</p><p>The first thing you do with ObfuscateJS is you need to initialize it with the JavaScript you want to obfuscate, so in this case, begin like the following:</p><div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">js</span> <span class="o">=</span> <span class="sx">%Q|
|
||
var arrr = new Array();
|
||
arrr[0] = windows.document.createElement("img");
|
||
arrr[0]["src"] = "a";
|
||
|</span>
|
||
|
||
<span class="n">obfu</span> <span class="o">=</span> <span class="o">::</span><span class="no">Rex</span><span class="o">::</span><span class="no">Exploitation</span><span class="o">::</span><span class="no">ObfuscateJS</span><span class="p">.</span><span class="nf">new</span><span class="p">(</span><span class="n">js</span><span class="p">)</span>
|
||
</code></pre></div></div><p><code class="language-plaintext highlighter-rouge">obfu</code> should return a <a href="https://github.com/rapid7/rex-exploitation/blob/f3058a0737ba89fd116f99a8381a409bba6a53fa/lib/rex/exploitation/obfuscatejs.rb">Rex::Exploitation::ObfuscateJS</a> object. It allows you to do a lot of things, you can really just call <code class="language-plaintext highlighter-rouge">methods</code>, or look at the source to see what methods are available (with additional API documentation). But for demo purposes, we’ll showcase the most common one: the <code class="language-plaintext highlighter-rouge">obfuscate</code> method.</p><p>To actually obfuscate, you need to call the <code class="language-plaintext highlighter-rouge">obfuscate</code> method. This method accepts a symbols argument that allows you to manually specify what symbol names (variables, methods, classes, etc) to obfuscate, it should be in a hash like this:</p><div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="p">{</span>
|
||
<span class="s1">'Variables'</span> <span class="o">=></span> <span class="p">[</span> <span class="s1">'var1'</span><span class="p">,</span> <span class="o">...</span> <span class="p">],</span>
|
||
<span class="s1">'Methods'</span> <span class="o">=></span> <span class="p">[</span> <span class="s1">'method1'</span><span class="p">,</span> <span class="o">...</span> <span class="p">],</span>
|
||
<span class="s1">'Namespaces'</span> <span class="o">=></span> <span class="p">[</span> <span class="s1">'n'</span><span class="p">,</span> <span class="o">...</span> <span class="p">],</span>
|
||
<span class="s1">'Classes'</span> <span class="o">=></span> <span class="p">[</span> <span class="p">{</span> <span class="s1">'Namespace'</span> <span class="o">=></span> <span class="s1">'n'</span><span class="p">,</span> <span class="s1">'Class'</span> <span class="o">=></span> <span class="s1">'y'</span><span class="p">},</span> <span class="o">...</span> <span class="p">]</span>
|
||
<span class="p">}</span>
|
||
</code></pre></div></div><p>So if I want to obfuscate the variable <code class="language-plaintext highlighter-rouge">arrr</code>, and I want to obfuscate the src string, here’s how:</p><div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>>> obfu.obfuscate('Symbols' => {'Variables'=>['arrr']}, 'Strings' => true)
|
||
=> "\nvar QqLFS = new Array();\nQqLFS[0] = windows.document.createElement(unescape(String.fromCharCode( 37, 54, 071, 045, 0x36, 0144, 37, 066, 067 )));\nQqLFS[0][String.fromCharCode( 115, 0x72, 0143 )] = unescape(String.fromCharCode( 045, 0x36, 0x31 ));\n"
|
||
</code></pre></div></div><p>In some cases, you might actually want to know the obfuscated version of a symbol name. One scenario is calling a JavaScript function from an element’s event handler, such as this:</p><div class="language-html highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nt"><html></span>
|
||
<span class="nt"><head></span>
|
||
<span class="nt"><script></span>
|
||
<span class="kd">function</span> <span class="nf">test</span><span class="p">()</span> <span class="p">{</span>
|
||
<span class="nf">alert</span><span class="p">(</span><span class="dl">"</span><span class="s2">hello, world!</span><span class="dl">"</span><span class="p">);</span>
|
||
<span class="p">}</span>
|
||
<span class="nt"></script></span>
|
||
<span class="nt"></head></span>
|
||
<span class="nt"><body</span> <span class="na">onload=</span><span class="s">"test();"</span><span class="nt">></span>
|
||
<span class="nt"></body></span>
|
||
<span class="nt"></html></span>
|
||
</code></pre></div></div><p>The obfuscated version would look like the following:</p><div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="n">js</span> <span class="o">=</span> <span class="sx">%Q|
|
||
function test() {
|
||
alert("hello, world!");
|
||
}
|
||
|</span>
|
||
|
||
<span class="n">obfu</span> <span class="o">=</span> <span class="o">::</span><span class="no">Rex</span><span class="o">::</span><span class="no">Exploitation</span><span class="o">::</span><span class="no">ObfuscateJS</span><span class="p">.</span><span class="nf">new</span><span class="p">(</span><span class="n">js</span><span class="p">)</span>
|
||
<span class="n">obfu</span><span class="p">.</span><span class="nf">obfuscate</span><span class="p">(</span><span class="s1">'Symbols'</span> <span class="o">=></span> <span class="p">{</span><span class="s1">'Methods'</span><span class="o">=></span><span class="p">[</span><span class="s1">'test'</span><span class="p">]},</span> <span class="s1">'Strings'</span> <span class="o">=></span> <span class="kp">true</span><span class="p">)</span>
|
||
|
||
<span class="n">html</span> <span class="o">=</span> <span class="sx">%Q|
|
||
<html>
|
||
<head>
|
||
<script>
|
||
</span><span class="si">#{</span><span class="n">js</span><span class="si">}</span><span class="sx">
|
||
</script>
|
||
</head>
|
||
<body onload="</span><span class="si">#{</span><span class="n">obfu</span><span class="p">.</span><span class="nf">sym</span><span class="p">(</span><span class="s1">'test'</span><span class="p">)</span><span class="si">}</span><span class="sx">();">
|
||
</body>
|
||
</html>
|
||
|</span>
|
||
|
||
<span class="nb">puts</span> <span class="n">html</span>
|
||
</code></pre></div></div><h2 id="the-jsobfu-class"> <a href="#the-jsobfu-class" class="anchor-heading" aria-labelledby="the-jsobfu-class"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> The JSObfu class</h2><p>The JSObfu class used to be ObfuscateJS’ cousin, but it has been completely rewritten since September 2014, and packaged as a <a href="https://rubygems.org/gems/jsobfu">gem</a>. The obfuscation is more complex and you can actually tell it to obfuscate multiple times. You also no longer have to manually specify what symbol names to change, it just knows.</p><p><strong>Trying JSObfu in Rex</strong></p><p>Let’s get back to irb again to demonstrate how easy it is to use JSObfu:</p><div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>$ ./msfconsole -q
|
||
msf > irb
|
||
[*] Starting IRB shell...
|
||
|
||
>>
|
||
</code></pre></div></div><p>This time we’ll do a “hello world” example:</p><div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>>> js = ::Rex::Exploitation::JSObfu.new %Q|alert('hello, world!');|
|
||
=> alert('hello, world!');
|
||
>> js.obfuscate
|
||
=> nil
|
||
</code></pre></div></div><p>And here’s the output:</p><div class="language-javascript highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nb">window</span><span class="p">[(</span><span class="nf">function </span><span class="p">()</span> <span class="p">{</span> <span class="kd">var</span> <span class="nx">_d</span><span class="o">=</span><span class="dl">"</span><span class="s2">t</span><span class="dl">"</span><span class="p">,</span><span class="nx">y</span><span class="o">=</span><span class="dl">"</span><span class="s2">ler</span><span class="dl">"</span><span class="p">,</span><span class="nx">N</span><span class="o">=</span><span class="dl">"</span><span class="s2">a</span><span class="dl">"</span><span class="p">;</span> <span class="k">return</span> <span class="nx">N</span><span class="o">+</span><span class="nx">y</span><span class="o">+</span><span class="nx">_d</span> <span class="p">})()]((</span><span class="nf">function </span><span class="p">()</span> <span class="p">{</span> <span class="kd">var</span> <span class="nx">f</span><span class="o">=</span><span class="dl">'</span><span class="s1">d!</span><span class="dl">'</span><span class="p">,</span><span class="nx">B</span><span class="o">=</span><span class="dl">'</span><span class="s1">orl</span><span class="dl">'</span><span class="p">,</span><span class="nx">Q2</span><span class="o">=</span><span class="dl">'</span><span class="s1">h</span><span class="dl">'</span><span class="p">,</span><span class="nx">m</span><span class="o">=</span><span class="dl">'</span><span class="s1">ello, w</span><span class="dl">'</span><span class="p">;</span> <span class="k">return</span> <span class="nx">Q2</span><span class="o">+</span><span class="nx">m</span><span class="o">+</span><span class="nx">B</span><span class="o">+</span><span class="nx">f</span> <span class="p">})());</span>
|
||
</code></pre></div></div><p>Like ObfuscateJS, if you need to get the randomized version of a symbol name, you can still do that. We’ll demonstrate this with the following example:</p><div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="o">>></span> <span class="n">js</span> <span class="o">=</span> <span class="o">::</span><span class="no">Rex</span><span class="o">::</span><span class="no">Exploitation</span><span class="o">::</span><span class="no">JSObfu</span><span class="p">.</span><span class="nf">new</span> <span class="sx">%Q|function test() { alert("hello"); }|</span>
|
||
<span class="o">=></span> <span class="n">function</span> <span class="nb">test</span><span class="p">()</span> <span class="p">{</span>
|
||
<span class="n">alert</span><span class="p">(</span><span class="s2">"hello"</span><span class="p">);</span>
|
||
<span class="p">}</span>
|
||
<span class="o">>></span> <span class="n">js</span><span class="p">.</span><span class="nf">obfuscate</span>
|
||
</code></pre></div></div><p>Say we want to know the randomized version of the method name “test”:</p><div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="o">>></span> <span class="nb">puts</span> <span class="n">js</span><span class="p">.</span><span class="nf">sym</span><span class="p">(</span><span class="s2">"test"</span><span class="p">)</span>
|
||
<span class="n">_</span>
|
||
</code></pre></div></div><p>OK, double check right quick:</p><div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>>> puts js
|
||
function _(){window[(function () { var N="t",r="r",i="ale"; return i+r+N })()](String.fromCharCode(0150,0x65,0154,0x6c,0x6f));}
|
||
</code></pre></div></div><p>Yup, that looks good to me.</p><p>And finally, let’s try to obfuscate a few times to see how that goes:</p><div class="language-plaintext highlighter-rouge"><div class="highlight"><pre class="highlight"><code>>> js = ::Rex::Exploitation::JSObfu.new %Q|alert('hello, world!');|
|
||
=> alert('hello, world!');
|
||
>> js.obfuscate(:iterations=>3)
|
||
=> window[String[((function(){var s=(function () { var r="e"; return r })(),Q=(function () { var I="d",dG="o"; return dG+I })(),c=String.fromCharCode(0x66,114),w=(function () { var i="C",v="r",f="omCh",j="a"; return f+j+v+i })();return c+w+Q+s;})())](('Urx'.length*((0x1*(01*(1*020+5)+1)+3)*'u'.length+('SGgdrAJ'.length-7))+(('Iac'.length*'XLR'.length+2)*'qm'.length+0)),(('l'.length*((function () { var vZ='k'; return vZ })()[((function () { var E="h",t="t",O="leng"; return O+t+E })())]*(0x12*1+0)+'xE'.length)+'h'.length)*(function () { var Z='uA',J='tR',D='x'; return D+J+Z })()[((function () { var m="th",o="g",U="l",Y="en"; return U+Y+o+m })())]+'lLc'.length),('mQ'.length*(02*023+2)+('Tt'.length*'OEzGiMVf'.length+5)),(String.fromCharCode(0x48,0131)[((function () { var i="gth",r="len"; return r+i })())]*('E'.length*0x21+19)+(0x1*'XlhgGJ'.length+4)),(String.fromCharCode(0x69)[((function () { var L="th",Q="n",$="l",I="g",x="e"; return $+x+Q+I+L })())]*('QC'.length*0x2b+3)+(01*26+1)))]((function(){var C=String[((function () { var w="rCode",j="mCha",A="fr",B="o"; return A+B+j+w })())]((6*0x10+15),('riHey'.length*('NHnex'.length*0x4+2)+4),(01*95+13),(1*('Z'.length*(0x1*(01*(0x3*6+5)+1)+18)+12)+46),(0x1*(01*013+6)+16)),JQ=String[((function () { var NO="ode",T="rC",HT="fromCha"; return HT+T+NO })())](('J'.length*0x54+17),(0x2*051+26),('TFJAGR'.length*('ymYaSJtR'.length*'gv'.length+0)+12),(01*0155+2),(0xe*'FBc'.length+2),(0x1*22+10),(3*(01*043+1)+11)),g=(function(){var N=(function () { var s='h'; return s })();return N;})();return g+JQ+C;})());
|
||
</code></pre></div></div><p><strong>Using JSObfu for module development</strong></p><p>When you are writing a module, you should not call Rex directly like the above examples. Instead, you should be using the <code class="language-plaintext highlighter-rouge">#js_obfuscate</code> method found in <a href="https://github.com/rapid7/rex-exploitation/blob/f3058a0737ba89fd116f99a8381a409bba6a53fa/lib/rex/exploitation/jsobfu.rb">JSObfu mixin</a>. When you’re using JavaScript in your module, always do write it like this:</p><div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="c1"># This returns a Rex::Exploitation::JSObfu object</span>
|
||
<span class="n">js</span> <span class="o">=</span> <span class="n">js_obfuscate</span><span class="p">(</span><span class="n">your_code</span><span class="p">)</span>
|
||
</code></pre></div></div><p>Note that by default, even though your module is calling the #js_obfuscate method, obfuscation will not kick in unless the user sets the JsObfuscate datastore option. This option is an OptInt, which allows you to set the number of times to obfuscate (default is 0).</p><hr><footer><p><a href="#top" id="back-to-top">Back to top</a></p><p class="text-small text-grey-dk-000 mb-0"> <a href="https://github.com/rapid7/metasploit-framework/tree/master/docs/metasploit-framework.wiki/How-to-obfuscate-JavaScript-in-Metasploit.md" id="edit-this-page">Edit this page on GitHub</a></p></footer></div></div><div class="search-overlay"></div></div><script type="text/javascript" src="/assets/js/toggle_mode.js"></script> <script> var config = { theme: 'default', logLevel: 'fatal', securityLevel: 'strict', startOnLoad: true, arrowMarkerAbsolute: false, er: { diagramPadding: 20, layoutDirection: 'TB', minEntityWidth: 100, minEntityHeight: 75, entityPadding: 15, stroke: 'gray', fill: 'honeydew', fontSize: 12, useMaxWidth: true, }, flowchart:{ diagramPadding: 8, htmlLabels: true, curve: 'basis', }, sequence: { diagramMarginX: 50, diagramMarginY: 10, actorMargin: 50, width: 150, height: 65, boxMargin: 10, boxTextMargin: 5, noteMargin: 10, messageMargin: 35, messageAlign: 'center', mirrorActors: true, bottomMarginAdj: 1, useMaxWidth: true, rightAngles: false, showSequenceNumbers: false, }, gantt: { titleTopMargin: 25, barHeight: 20, barGap: 4, topPadding: 50, leftPadding: 75, fontSize: 11, gridLineStartPadding: 35, fontFamily: '\'Open Sans\', sans-serif', numberSectionStyles: 4, axisFormat: '%Y-%m-%d', topAxis: false, }, }; mermaid.initialize(config); window.mermaid.init(undefined, document.querySelectorAll('.language-mermaid')); </script>
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