/ android

Monitoring Android network traffic

So I've found myself in need of some Android network sniffing. Well that's an easy one.

What we need

  • A device with Android >= 4.0 and tcpdump.
  • Or: An emulator with Android >= 4.0.
  • Android development tools.
  • WireShark.

Let's do it

This method is much easier done using an emulator, because these come with tcpdump preinstalled and grabbing the captured traffic out of an emulator is a piece of cake.

First of all we need to install WireShark.

On the emulator

  1. List your available virtual devices:
    emulator -list-avds
  2. Start an emulator with tcpdump:
    emulator -tcpdump {DUMP_FILE_LOCATION} -avd {AVD_NAME}
  3. Run your app and do your thing.
  4. Close the emulator.
  5. Start WireShark.
  6. Drag and drop your capture file into WireShark.
Example
C:\Users\Nitz>emulator -list-avds
Nexus_5X_API_22
Nexus_5X_API_22_64bit

C:\Users\Nitz>emulator -engine classic -tcpdump d:\dump.cap -avd Nexus_5X_API_22_64bit
emulator: WARNING: Classic qemu does not support SMP. The hw.cpu.ncore option from your config file is ignored.
emulator: device fd:1372

HAXM is working and emulator runs in fast virt mode
emulator: Listening for console connections on port: 5554
emulator: Serial number of this emulator (for ADB): emulator-5554
And the result:

On a real device

  1. First root your device. This will not be explained here of course.
  2. Assuming an ARM device, grab the latest tcpdump from here.
    If your device is x86, you may need to cross-compile manually. This is explained here and here.
  3. Push tcpdump into your rooted device:
    adb push tcpdump /system/xbin/
  4. Let's test:
    adb shell tcpdump -h
    Should result in something like this:
libpcap version 1.6.1
Usage: tcpdump [-aAbdDefhHIJKlLnNOpqRStuUvxX] [ -B size ] [ -c count ]
[ -C file_size ] [ -E algo:secret ] [ -F file ] [ -G seconds ]
[ -i interface ] [ -j tstamptype ] [ -M secret ]
[ -P in|out|inout ]
[ -r file ] [ -s snaplen ] [ -T type ] [ -V file ] [ -w file ]
[ -W filecount ] [ -y datalinktype ] [ -z command ]
[ -Z user ] [ expression ]
  1. Now let's start tcpdump for all available interfaces:
    adb shell tcpdump -i any -p -s 0 -w /sdcard/capture.pcap
  2. Press ctrl-c when done.
  3. Pull the captured traffic out of the device:
    adb pull /sdcard/capture.pcap .
  4. Run WireShark.
  5. Drag and drop the captured network file to WireShark.

What about SSL?

In order to parse SSL traffic we'd need to set up a MITM proxy. We've talked about this in this post.