metasploit-payloads/c/meterpreter

Native C meterpreter >

Building - Windows

As of commit a2888b1b4862819c9aae81bf46d8c92d8164c598, Windows Meterpreter is built with Visual Studio 2013 Express for Desktop or any paid version of Visual Studio 2013. Earlier toolsets on Windows are no longer supported -- this includes Visual Studio 2012. Make sure that the version that you download is Visual Studio Express 2013 for Windows Desktop -- dependng on your operating system, if you get the wrong version of VS2013, the installer will complain about needing "a more recent version of Windows." If you are using a dedicated build machine, your best bet is to uninstall Visual Studio 2012 if your only project is Meterpreter.

Visual Studio 2013 requires .NET 4.5.1 in order to run, and as a result isn't compatible with Windows XP due to the fact that .NET 4.5 will not run on Windows XP. However, this does not mean that Metepreter itself will not run on Windows XP, it just means that it's not possible to build it on Windows XP.

Windows Meterpreter has the following repositories set up as submodule dependencies:

• Reflective DLL Injection

For Meterpreter to build correctly, these submodules must be initialised and updated, like so:

$ git clone https://github.com/rapid7/metasploit-payloads
$ cd metasploit-payloads
$ git submodule init && git submodule update

At this point the dependencies will be ready to use and Meterpreter should be ready to build.

• OpenSSL

Occasionally, new versions of OpenSSL are released and need to be incorporated into the Meterpreter build. See the README under source/openssl/lib for build instructions. You will also need to refresh the header files from the source tarball as well. TODO: This entire process appears automatable given a proper build environment.

An example of updating OpenSSL is detailed in Pull Request #86.

Running the Build

Open up a Visual Studio command prompt by selecting Developer Command Prompt for VS2013 from the Start menu. Alternatively you can run vcvars32.bat from an existing command line prompt, just make sure it's the VS2013 one if you have multiple versions of VS installed on your machine.

Once you have your environment variables set up, change to the root folder where the meterpreter source is located. From here you can:

• Build the x86 version by running: make x86
• Build the x64 version by running: make x64
• Build both x86 and x64 versions by running: make

The compiled binaries are written to the output/x86 and output/x64 folders.

If you are not a Rapid7 employee, make sure you build the source using the debug or release configurations when inside Visual Studio. If you attempt to build r7_debug or r7_release you will get compiler errors due to missing libraries.

If you build the source from the command line the toolset will choose the most appropriate build configuration for you and hence calling make should "Just Work™".

If you are a Rapid7 employee you will need the PSSDK source in order to build the extra components using the r7_* build configurations.

If submodule dependencies are not found on the file system, the script should display an error message like so:

Meterpreter's submodule dependencies can't be found.
From your git console, please run:
  $ git submodule init && git submodule update

Testing

There is currently no automated testing for meterpreter, but we're working on it.

Once you've made changes and compiled a new .dll or .so, copy the contents of the output/ directory into your Metasploit Framework's data/meterpreter/ directory.

If you made any changes to metsrv.dll ensure that all extensions still load and function properly.

Creating Extensions

Creating extensions isn't complicated, but it's not simple either. In an attempt make the set up a little easier on the Meterpreter side, a new project called ext_server_bare has been created which is just the shell of a project which can be used as the starting point for your code. To use this as a template to create your own project, you can follow these steps.

Note: All paths listed here are relative to the root meterpreter folder where this document resides.

Pick a name for your extension, make sure it's something meaningful and short. For the sake of example, we'll create a new extension called splat. Once you have a cool an meaningful name, you can get your project going by doing the following:

1. Create a new folder called workspace/ext_server_splat.
2. Copy workspace/ext_server_bare/ext_server_bare.vcxproj to workspace/ext_server_splat/ext_server_splat.vcxproj
3. Open workspace/ext_server_splat/ext_server_splat.vcxproj with a text editor and..
   • Replace all instances of BARE with SPLAT.
   • Replace all instances of bare with splat.
   • Search for the ProjectGuid property in the document. It looks like <ProjectGuid>{D3F39324-040D-4B1F-ADA9-762F16A120E6}</ProjectGuid>. When found, generate a new GUID for your project either using guidgen.exe or an online tool, and replace this GUID with your new GUID. Make sure you keep the curly braces.
4. Create a new folder called source/extensions/splat.
5. Copy source/extensions/bare/bare.c to source/extensions/splat/splat.c
6. Copy source/extensions/bare/bare.h to source/extensions/splat/splat.h
7. Open workspace/meterpreter.sln in Visual Studio 2013.
8. Right-click on the solution item called Solution 'meterpreter' and select Add, then Existing Project....
9. Browse to your new project's location at workspace/ext_server_splat and select ext_server_splat.vcxproj.
10. The solution should automagically pick up your project configurations and wire them in where appropriate.
11. Right-click, again, on the solution item and select Configuration Manager.
12. In the resulting window, iterate through all combinations Active Solution Configuration and Active Solution Platform and make sure that:
    • Configuration matches with all the other extensions in each case.
    • Platform matches with all the other extensions in each case.
    • Build is checked in each case.
    • Deploy is NOT checked in each case.
13. Modify the contents of splat.c and splat.h so that the file header commands are up to date, and that all references to bare have been removed.

At this point you're ready to start adding your extension's functionality.

Things to Remember

• Your extension is set up to build both 32 and 64 bit versions. Make sure you're mindful of this when you are writing your code. All of the usual pitfalls apply when dealing with things like pointer sizes, value trunction, etc.
• Make sure your extension builds correctly from the command line using make.
• The outputs of your builds, when successful, are copied to output/x64 and output/x86.

Good luck!