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nitro

Virtual Machine Introspection for KVM.

This is the userland component named nitro. It will receive the events generated by KVM and display them.

Requirements

  • python 3
  • docopt
  • libvirt
  • ioctl-opt Python 3
  • cffi Python3 (optional)
  • libvmi (optional)
  • rekall (optional)

Setup

  • Setup a VM. Make sure to use the qemu:///system connection. Go to the tests folder to find a packer template and an import script if you don't have one already.

(Nitro only supports for now Windows XP x64 and Windows 7 x64, see the Note section below)

Usage

  • Make sure that you have loaded the modified kvm modules. (cd kvm-vmi && make modules && make reload)

  • Start the VM that you would like to monitor.

  • Wait for the desktop to be available on the VM.

  • Start Nitro with ./main.py <vm_name>.

"""Nitro.

Usage:
  main.py [options] <vm_name>

Options:
  -h --help     Show this screen
  --nobackend   Don't analyze events
  -o --output   Output file (stdout if not specified)

"""

Nitro monitors the given <vm_name> syscalls by activating a set of traps in KVM. The optional components listed above are needed only if you want to extract more information about the captured events. See the Backend section.

Here i will assume that you have installed only the required ones. Therefore you have to run Nitro with the option --nobackend.

It will run until the user sends a CTRL+C to stop it, in which case Nitro will unset the traps and write the captured events in a file named events.json.

By defaults, Nitro will print events to stdout. If this is not desired --out can be used to redirect output into a file.

An event should look like this output

  {
    "direction": "enter",
    "rax": "0x1005",
    "vcpu": 0,
    "type": "syscall",
    "cr3": "0x1b965000"
  },

A successful run should give the following output :

$ ./main.py --nobackend nitro_win7x64
Setting traps to False
Finding QEMU pid for domain nitro_win7x64
Detected 1 VCPUs
Setting traps to True
Start listening on VCPU 0
{'cr3': '0x6cdc000',
 'direction': 'exit',
 'rax': '0x3f',
 'type': 'syscall',
 'vcpu': 0}
{'cr3': '0x6cdc000',
 'direction': 'enter',
 'rax': '0x138',
 'type': 'syscall',
 'vcpu': 0}
{'cr3': '0x6cdc000',
 'direction': 'exit',
 'rax': '0x0',
 'type': 'syscall',
 'vcpu': 0}
{'cr3': '0x6cdc000',
 'direction': 'enter',
 'rax': '0x58',
 'type': 'syscall',
 'vcpu': 0}
{'cr3': '0x6cdc000',
 'direction': 'exit',
 'rax': '0x0',
 'type': 'syscall',
 'vcpu': 0}
{'cr3': '0x6cdc000',
 'direction': 'enter',
 'rax': '0x138',
 'type': 'syscall',
 'vcpu': 0}
{'cr3': '0x6cdc000',
 'direction': 'exit',
 'rax': '0x0',
 'type': 'syscall',
 'vcpu': 0}
{'cr3': '0x6cdc000',
 'direction': 'enter',
 'rax': '0x5f',
 'type': 'syscall',
 'vcpu': 0}
Setting traps to False

Backend

The Backend is supposed to analyze raw nitro events, and extract useful informations, such as:

  • process name
  • process PID
  • syscall name

Rekall

Rekall is used in symbols.py to extract the syscall table from the memory dump.

Unfortunately, Rekall is not available as a Debian package. For now you will have to install it system-wide with pip. (Python2)

$ sudo pip2 install --upgrade setuptools pip wheel
$ sudo pip2 install rekall

libvmi

  • Compile and install libvmi. See the install notes

  • Configure the file libvmi.conf, which is already provided in the repo

Configure the name of your vm that you want to monitor : (only Windows 7 x64 is supported here)

nitro_win7x64 {
    ostype      = "Windows";
    win_tasks   = 0x188;
    win_pdbase  = 0x28;
    win_pid     = 0x180;
    win_pname   = 0x2e0;
}

At least, the following keys are required :

  • win_tasks
  • win_pdbase
  • win_pid
  • win_pname

libvmi python wrapper

The python wrapper on top of Libvmi is based on CFFI and needs to be compiled.

$ python3 nitro/build_libvmi.py

Running Nitro with the Backend

If you have installed everything correctly, you can run Nitro : ./main.py nitro_win7x64

An event should now look like this:

  {
    "event": {
      "cr3": "0xbda6000",
      "direction": "enter",
      "type": "syscall",
      "vcpu": 0,
      "rax": "0x14"
    },
    "name": "nt!NtQueryValueKey",
    "process": {
      "name": "services.exe",
      "pid": 456
    }
  },