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Avi Lumelsky edited this page Apr 10, 2023 · 1 revision

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Sandbox Examples

To understand how to trace your process and create custom profiles for modules or applications, please see Tracing Processes

Docker examples

We have a Zero-To-One with Docker that goes through Tracing and Compiling an eBPF sandbox for an app.

Secure Import Examples

Simple Usage

Advanced Usage

Interactive Examples

How pickle can be exploited in your 3rd party packages:

import pickle
class Demo:
    def __reduce__(self):
        return (eval, ("__import__('os').system('echo Exploited!')",))

pickle.dumps(Demo())
b"\x80\x04\x95F\x00\x00\x00\x00\x00\x00\x00\x8c\x08builtins\x94\x8c\x04eval\x94\x93\x94\x8c*__import__('os').system('echo Exploited!')\x94\x85\x94R\x94."
pickle.loads(b"\x80\x04\x95F\x00\x00\x00\x00\x00\x00\x00\x8c\x08builtins\x94\x8c\x04eval\x94\x93\x94\x8c*__import__('os').system('echo Exploited!')\x94\x85\x94R\x94.")
Exploited!
0

With secimport, you can control such action to do whatever you want:

import secimport
pickle = secimport.secure_import("pickle")
pickle.loads(b"\x80\x04\x95F\x00\x00\x00\x00\x00\x00\x00\x8c\x08builtins\x94\x8c\x04eval\x94\x93\x94\x8c*__import__('os').system('echo Exploited!')\x94\x85\x94R\x94.")

[1]    28027 killed     ipython

A log file is automatically created, containing everything you need to know:

$ less /tmp/.secimport/sandbox_pickle.log

  @posix_spawn from /Users/avilumelsky/Downloads/Python-3.10.0/Lib/threading.py
    DETECTED SHELL:
        depth=8
        sandboxed_depth=0
        sandboxed_module=/Users/avilumelsky/Downloads/Python-3.10.0/Lib/pickle.py

    TERMINATING SHELL:
        libsystem_kernel.dylib`__posix_spawn+0xa
        ...
                libsystem_kernel.dylib`__posix_spawn+0xa
                libsystem_c.dylib`system+0x18b
                python.exe`os_system+0xb3
    KILLED
:



Creating a YAML policy file

For a full tutorial, see YAML Profiles Usage

# An example yaml template for a sandbox.

modules:
  requests:
    destructive: true
    syscall_allowlist:
      - write
      - ioctl
      - stat64
  fastapi:
    destructive: true
    syscall_allowlist:
      - bind
      - fchmod
      - stat64
  uvicorn:
    destructive: true
    syscall_allowlist:
      - getpeername
      - getpgrp
      - stat64



Blocking New Processes Example

Python 3.10.0 (default, May  2 2022, 21:43:20) [Clang 13.0.0 (clang-1300.0.27.3)] on darwin
Type "help", "copyright", "credits" or "license" for more information.

# Let's import subprocess module, limiting it's syscall access.
import secimport
subprocess = secimport.secure_import("subprocess")

# Let's import os
import os
os.system("ps")
  PID TTY           TIME CMD
 2022 ttys000    0:00.61 /bin/zsh -l
50092 ttys001    0:04.66 /bin/zsh -l
75860 ttys001    0:00.13 python
0
# It worked as expected, returning exit code 0.


# Now, let's try to invoke the same logic using a different module, "subprocess", that was imported using secure_import:
subprocess.check_call('ps')
[1]    75860 killed     python

# Damn! That's cool.

When using secure_import, the following files are created:

  • The dtrace/bpftrace sandbox code for the module is saved under:
    • /tmp/.secimport/sandbox_subprocess.bt:
      • when using bpftrace
    • /tmp/.secimport/sandbox_subprocess.d
      • when using dtrace
  • The log file for this module is under
    • /tmp/.secimport/sandbox_subprocess.log: 
      ...

(OPENING SHELL using posix_spawn): (pid 75860) (thread 344676) (user 501) (python module: <stdin>) (probe mod=, name=entry, prov=syscall func=posix_spawn) /bin/sh
    #posix_spawn,

(TOUCHING FILESYSTEM): write(140339021606912) from thread 344676
            libsystem_kernel.dylib`__fork+0xb
            _posixsubprocess.cpython-310-darwin.so`do_fork_exec+0x29
            _posixsubprocess.cpython-310-darwin.so`subprocess_fork_exec+0x71f
            python.exe`cfunction_call+0x86
killing...
killed.



Shell Blocking Example

You can try it yourself with docker, locally.

./docker/build.sh
./docker/run.sh
root@d57458518cbf:/workspace$ ./run_sandbox.sh
🚀 Starting secimport sandbox with bpftrace backend, the sandbox should kill the python process...
WARNING: Addrspace is not set
  PID TTY          TIME CMD
    1 pts/0    00:00:00 sh
   10 pts/0    00:00:00 bash
   18 pts/0    00:00:00 bash
   19 pts/0    00:00:00 bpftrace
   23 pts/0    00:00:00 python
   24 pts/0    00:00:00 sh
   25 pts/0    00:00:00 sh
   26 pts/0    00:00:00 pkill
   27 pts/0    00:00:00 ps


🛑 The process was killed, as expected.
🚀 The sandbox bpftrace code is at sandbox.bt
🚀 The sandbox log is at sandbox.log.

The following code will open a new bash shell using os.system. In this sandbox we disallow such behavior, by disabling the fork/exec/spawn syscalls.

# example.py - Executes code upon import;
import os;

os.system('Hello World!');
from secimport import secure_import

example = secure_import('example', allow_shells=False)

Let's run the and see what happens:

(root) sh-3.2#  export PYTHONPATH=$(pwd):$(pwd)/examples:$(pwd):$PYTHONPATH
(root) sh-3.2#  python examples/production.py
Successfully compiled dtrace profile:  /tmp/.secimport/sandbox_example.d
Killed: 9
  • We imported example with limited capabilities.
  • If a syscall like spawn/exec/fork/forkexec will be executed
    • The process will be killed with -9 signal.

Network Blocking Example

import requests
requests.get('https://google.com')
<Response [200]>


from secimport import secure_import
requests = secure_import('requests', allow_networking=False)

# The next call should kill the process,
# because we disallowed networking for the requests module.
requests.get('https://google.com')
[1]    86664 killed
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