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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 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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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class="breadcrumb-nav-list-item"> <span>C Obfuscation</span></ol></nav><div id="main-content" class="main-content" role="main"><h1 id="how-to-use-metasploitframeworkobfuscationcrandomizer"> <a href="#how-to-use-metasploitframeworkobfuscationcrandomizer" class="anchor-heading" aria-labelledby="how-to-use-metasploitframeworkobfuscationcrandomizer"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> How to use Metasploit::Framework::Obfuscation::CRandomizer</h1><h2 id="what-is-crandomizer"> <a href="#what-is-crandomizer" class="anchor-heading" aria-labelledby="what-is-crandomizer"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> What is CRandomizer</h2><p>CRandomizer is an obfuscation feature in Metasploit Framework that allows you to randomize C code. It is done by injecting random statements such as native API calls, custom fake function calls, or other routines, etc. The CRandomizer is also supported by Metasploit Frameworks code compiling API, which allows you to build a custom application that is unique (in terms of checksums), also harder to reverse-engineer.</p><p>The randomness of the modification is based on a weight, an arbitrary number from 0 - 100. The higher the number, the more random the code gets.</p><h2 id="components"> <a href="#components" class="anchor-heading" aria-labelledby="components"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> Components</h2><p>CRandomizer relies on Metasm to be able to parse C code. The following components are built to parse and modify the source code.</p><h2 id="code-factory"> <a href="#code-factory" class="anchor-heading" aria-labelledby="code-factory"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> Code Factory</h2><p>Also known as <code class="language-plaintext highlighter-rouge">Metasploit::Framework::Obfuscation::CRandomizer::CodeFactory</code>.</p><p>The <code class="language-plaintext highlighter-rouge">CodeFactory</code> module is used to make the random stubs that will get injected later in the source code. Currently, the things this class is capable of making include small stubs like if statements, a switch, fake functions, and Windows API calls, etc. Each stub tends to be small, and considered as benign by most AVs.</p><p>Every class in CodeFactory, except for Base, FakeFunction, and FakeFunctionCollection, is a stub candidate that gets randomly selected and used in the source code.</p><p>If a stub requires a native API call, then the class can specify <code class="language-plaintext highlighter-rouge">@dep</code> to set that dependency. If the source code does not support the API call, then the next stub candidate is used (or until one is found).</p><p>For example, the <code class="language-plaintext highlighter-rouge">CRandomizer::CodeFactory::OutputDebugString</code> class is used to generate a fake OutputDebugString call, and the dependency is set as <code class="language-plaintext highlighter-rouge">['OutputDebugString']</code>. If the source code includes the Windows.h header, the CRandomizer knows it is okay to inject OutputDebugString. If not, CRandomizer will not use it.</p><h2 id="modifier"> <a href="#modifier" class="anchor-heading" aria-labelledby="modifier"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> Modifier</h2><p>Also known as <code class="language-plaintext highlighter-rouge">Metasploit::Framework::Obfuscation::CRandomizer::Modifier</code>.</p><p>The Modifier class decides how something should be modified, and actually modifies the source code, for example: a function, different if statements, loops, nested blocks, etc.</p><p>While the modifier walks through the source, it will randomly inject extra code (provided by the CodeFactory class) at each statement, until there are no more functions to modify.</p><h2 id="parser"> <a href="#parser" class="anchor-heading" aria-labelledby="parser"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> Parser</h2><p>Also known as <code class="language-plaintext highlighter-rouge">Metasploit::Framework::Obfuscation::CRandomizer::Parser</code>.</p><p>The main purpose of the Parser class is to convert the source code into a parsable format using Metasm, and then pass the functions to the Modifier class to process.</p><h2 id="utility"> <a href="#utility" class="anchor-heading" aria-labelledby="utility"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> Utility</h2><p>The Utility class provides quick-to-use methods that any CRandomizer classes could use.</p><h1 id="code-example"> <a href="#code-example" class="anchor-heading" aria-labelledby="code-example"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> Code Example</h1><h2 id="creating-a-new-stub"> <a href="#creating-a-new-stub" class="anchor-heading" aria-labelledby="creating-a-new-stub"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> Creating a new stub</h2><p>First, add a new file under the code_factory with an arbitrary file name. For example: hello.rb. In this example, lets create a new stub that will printf() “Hello World”. Your stub should be written as a class under the CodeFactory namespace, and make sure to inherit the Base class. Like this:</p><div class="language-ruby highlighter-rouge"><div class="highlight"><pre class="highlight"><code><span class="nb">require</span> <span class="s1">'metasploit/framework/obfuscation/crandomizer/code_factory/base'</span>
<span class="k">module</span> <span class="nn">Metasploit</span>
<span class="k">module</span> <span class="nn">Framework</span>
<span class="k">module</span> <span class="nn">Obfuscation</span>
<span class="k">module</span> <span class="nn">CRandomizer</span>
<span class="k">module</span> <span class="nn">CodeFactory</span>
<span class="k">class</span> <span class="nc">Printf</span> <span class="o">&lt;</span> <span class="no">Base</span>
<span class="k">def</span> <span class="nf">initialize</span>
<span class="k">super</span>
<span class="vi">@dep</span> <span class="o">=</span> <span class="p">[</span><span class="s1">'printf'</span><span class="p">]</span>
<span class="k">end</span>
<span class="k">def</span> <span class="nf">stub</span>
<span class="sx">%Q|
int printf(const char*);
void stub() {
printf("Hello World");
}|</span>
<span class="k">end</span>
<span class="k">end</span>
<span class="k">end</span>
<span class="k">end</span>
<span class="k">end</span>
<span class="k">end</span>
<span class="k">end</span>
</code></pre></div></div><p>Notice a couple of things:</p><ul><li>Every class should have its own <code class="language-plaintext highlighter-rouge">stub</code> method. And this <code class="language-plaintext highlighter-rouge">stub</code> method should return a string that contains the code you wish to inject. In addition, your code should be written as a function so that Metasm knows how to pick it up, hence the printf is in a <code class="language-plaintext highlighter-rouge">void stub()</code> function.<li>If your stub requires a native API (in this case, we are using <code class="language-plaintext highlighter-rouge">printf</code>), then you must add this function name in the <code class="language-plaintext highlighter-rouge">@dep</code> instance variable, which is an array.<li>Please keep in mind that your stub should remain simple and small, and not unique. For example, avoid:<ul><li>Allocate a huge chunk of memory<li>Avoid marking or allocating executable memory<li>Loops<li>Load referenced section, resource, or .data<li>Anti-debugging functions from the Windows API<li>Lots of function calls<li>Unique strings<li>APIs that access the Windows registry or the file system<li>XOR<li>Shellcode<li>Any other suspicious code patterns that are unique to malware.</ul></ul><h2 id="randomizing-source-code"> <a href="#randomizing-source-code" class="anchor-heading" aria-labelledby="randomizing-source-code"><svg viewBox="0 0 16 16" aria-hidden="true"><use xlink:href="#svg-link"></use></svg></a> Randomizing source code</h2><p>Please refer to tools/exploit/random_compile_c.rb for example.</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-use-Metasploit-Framework-Obfuscation-CRandomizer.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>