Analyze your first scenario

Now that we have a first scenario, it is time to take a look at it.

The analyze page

If you followed the guide this far, you should have landed on the scenario's Analyze page. To find this page again:

  1. Click on the Scenario Manager tab.
  2. Locate your scenario in the table.
  3. To the right are multiple buttons, each corresponding to a page we have seen so far.
  4. Click on Analyze.

On this Analyze page are multiple buttons. You can:

  • Start or Stop the Reven server for this scenario.
  • Start the Analysis GUI named Axion.
  • Open up the Jupyter interface for Python scripting.

NOTE: As the latter two options require a Reven server, they will start it up automatically if it is not already running for this scenario.

The analysis GUI Axion

  1. Click on Start Axion. Note this will automatically start the scenario's Reven server as well.

    Start Axion

  2. Click on Show in browser to open the Analysis GUI.

The GUI opens up and various widgets show you the content of the trace. By default, the GUI points at the beginning of the trace, and since we started recording manually, you are probably looking at some system code.

Moreover, if this is the first time your start Axion, the GUI Tutorial has popped up. If not, start it manually:

  1. Click on the Tutorial button located on the toolbar.

    Start Tutorial

  2. Follow the tutorial up to the end: you will learn about all widgets and the basics of trace navigation.

  3. Close the tutorial.

Once this is done, there are a few things we can start looking at in our trace. Note there might be slight differences depending on whether the guest you recorded is a Windows or Linux VM.

Finding the entry point

We want to skip the system code and jump straight at the program's entry point.

  1. Start a Symbol call search on the binary hostname and symbol wmain:
    1. Start typing hostname in the binary path field.
    2. Use the autocomplete to select the full binary path.
    3. Move to the symbol name field, start typing main.
    4. Select the proper entry point (wmain on Windows)
    5. Press Enter to start the search
    6. Go to the next result by pressing F4.
  2. Bring up the Calltree widget: you can now start exploring the binary's trace.

Linking the printed string to its source

NOTE: On Linux traces and especially at the beginning of a program, your are likely to see calls such as init+0x56 where you would expect libc calls: this is the library loader dynamically finding the destination the first time a call to a particular library function is made. This gets better when more and more calls are resolved.

  1. Try to find the function call responsible for printing the hostname on the command line:

    1. In the Calltree widget, unfold the calls made by the main function and children. You are looking for a function name containing put or print.

    2. To check a candidate that could print what you want, double-click on it.

    3. Look at the registers to see the call's arguments. You can double-click on a register value to open up a memory view at the register's address.

      Print hostname

    4. If you see the hostname in the memory view, you have find your output buffer.

  2. Try to see where this buffer is coming from:

    1. Open up the memory history on the output buffer but checking Show access history of selection.

      Open memory history

    2. The closest access that occurred before the point in time we are at will be selected. Double-click on the closest Write access to see where this address was written to last.

      Memory access

    3. Look at the current symbol, and the Calltree or the Backtrace: you traveled back to when the hostname was fetched.

Python API

We can also use the Python API to get information from a trace.

  1. Go back to the scenario's Analyze page.
  2. Click on Open Python
  3. The Welcome page of the esReven My Notebooks app is displayed. From there, depending on your Jupyter Lab and Reven Python API fluency, you can head to the Getting started Knowledge Base module to learn or be reminded the basics, or you can directly create your own Jupyter notebook.

You can learn more about the integration with JupyterLab here.

What's next

This quick start guide is now over. At this point, there are multiple things you can do:

  • Read more about Managing VMs, especially the Need to Know section for more details about certain steps we took during this guide.
  • Use the registered VM to record new scenarios with your own binaries:
    • Use the Select files to make available on the VM step to push new files
    • On the recording screen, click on Insert Scenario CDROM to mount the CD-ROM on the guest.
  • Take a look at pre-recorded scenarios you can download, import into your Reven installation and analyze.
©2019-2023 eShard