This is the preview of the Zemu cloud client for generating dynamic binary traces. It provides strace-like functionality for Linux/IoT binaries, as well as an instruction-level overlay for execution visualization in IDA Pro.

Zemu is a lightweight, high-speed, emulator for user space binaries. It has a similar use-case to QEMU user-mode emulation. However, whereas QEMU relies on native host syscall execution, Zemu emulates the syscalls as well. This gives Zemu the flexibility to emulate binaries designed to run multiple different platforms, regardless of the host system, as well as the ability to sandbox and modify exection on-the-fly. At the same time, it does not require full system virtualization, and thus scales well in terms of memory and configuration overhead.

This client script submits binaries to an Azure Function running Zemu, which automatically scales-out based on the total demand.

Zemu can run Linux and Windows binaries. Statically-linked malware binaries are our primary focus and the most well-tested.

• There is a 30 second time limit.
• Network requests are not allowed. Empty data is returned rather than a hard fail.
• Around 25% of the most used Linux syscalls are implemented. Mileage may vary with other syscalls.

• Continue to add more syscalls.
• Improved architecture support.
• A limited number of environments are supported, which are automatically selected based on the binary. We plan to add more environments and make them selectable. This is particularly important for dynamically-linked binaries.
• Incorporation of concolic execution, using fuzzing and symbolic exection, to explore malware binaries in-depth.

API keys are currently by invite-only (as of 10/02/2019). We will later release a portal to provide any vetted security researcher access to the API.

The client runs on any platform supporting Python.

Paste your API key into zemu.py. For example, replace:

API_KEY = os.environ.get(
    'ZEMU_API_KEY', 'PASTE_YOUR_API_KEY_HERE')

with your API key:

API_KEY = os.environ.get(
    'ZEMU_API_KEY', 'c929270f53a0c27162659c932746fbe3')

Note: By default, API keys limit the submission rate to 1 analysis per second.

The plugin requires IDA Pro 7.0 or above.

To install the plugin, copy ida-plugin/zemu_ida.py into the IDA Pro plugins directory. In Windows, for example, this directory is located at C:\Program Files\IDA 7.0\plugins. In Linux, the path is ~/.idapro/plugins. Once installed, the plugin is available under the View->Load Zemu Overlay... menu.

Python is required. Example usage and output:

The strace functionality provides output similar to the Linux utility. The first column indicates the calling thread (e.g. main, thread1, etc.), the second column indicates the return address post-syscall, followed by the syscall itself with arguments and return value.

$ python zemu.py strace testdata/static_elf_arm_helloworld

Zemu Copyright (c) 2019 Zeropoint Dynamics, LLC

Submitting.................done.
Queued. Awaiting results...done.

[main] [0x4b7ec] brk ( addr=0x0 ) -> 90000048
[main] [0x4b7ec] brk ( addr=0x90000d50 ) -> 90000d50
[main] [0x108d8] set_tls ( env=0x90000510 ) -> void
[main] [0x4b0ec] uname ( buf=0xff08fbe0 ) -> 0
[main] [0x55214] readlink ( pathname=0x719f8 ("/proc/self/exe"), buf=0xff08ed20, bufsiz=0x1000 ) -> 18
[main] [0x4b7ec] brk ( addr=0x90021d50 ) -> 90021d50
[main] [0x4b7ec] brk ( addr=0x90022000 ) -> 90022000
[main] [0x531fc] access ( pathname=0x71620 ("/etc/ld.so.nohwcap"), mode=0x0 ) -> -1
[main] [0x284ec] fstat64 ( fd=0x1, statbuf=0xff08fc80 ) -> 0
[main] [0x28820] write ( fd=0x1, buf=0x60b60 ("hello world!"), count=0xc ) -> c
[main] [0x28820] write ( fd=0x1, buf=0x90000fa8 ("
"), count=0x1 ) -> 1
[main] [0x27cd4] exit_group ( status=0x0 ) -> void

The overlay functionality provides JSON output containing information about the functions and instructions executed, as well as register and memory values at each instruction. First, generate the overlay file:

$ python zemu.py overlay testdata/static_elf_arm_helloworld > static_elf_arm_helloworld.overlay

Zemu Copyright (c) 2019 Zeropoint Dynamics, LLC

Submitting.................done.
Queued. Awaiting results...done.

Then, open the binary in IDA Pro and select View->Load Zemu Overlay... from the menu:

Select the overlay you just generated and press Open. The instructions executed in the run will now be highlighted, with comments added indicating register and memory values at the time of instruction execution (note that these values are from the first execution of the instruction). Functions that were executed will be now be prefixed with zmu_.

There are additional samples in the examples directory, generated from real malware interrogations.