secimport 0.1.0

A sandbox/supervisor for python modules.

secimport

A sandbox/supervisor for python modules.

secimport can be used to:

• Confine/Restrict specific python modules inside your production environment.
  • Open Source, 3rd party from unstrusted sources.
• Audit the flow of your python application at user-space/os/kernel level.
• Run an entire python application under unified configuration
  • Like seccomp and seccomp-bpf, without changing your code
  • Not limited to Linux kernels. Cross platform.

Requirements

• A python interpreter that was built with --with-dtrace.
  • See INSTALL.md.

Quick Start

For the full list of examples, see EXAMPLES.md.

Shell blocking

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

  os.system('Hello World!');

# production.py - Your production code
  from secimport import secure_import 

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

(root) sh-3.2#  export PYTHONPATH=$(pwd)/src:$(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

>>> 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, since networking is not allowed
>>> requests.get('https://google.com')
[1]    86664 killed

Python Shell Interactive 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.

• The dtrace profile for the module is saved under:
  • /tmp/.secimport/sandbox_subprocess.d:
• 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.
    

Useful References

• Examples
• F.A.Q
• Installation
• Mac OS Users - Disabling SIP for dtrace
• Tracing processes
  • Using dtrace
    • Tracing the syscalls of a process with pid 12345
      • dtrace -n 'syscall::: /pid == ($1)/ {@[pid,execname,probefunc]=count()}' 12345
    • Tracing the syscalls of a docker container with pid 12345
      • dtrace -n 'syscall::: /progenyof($1)/ {@[pid,execname,probefunc]=count()}' 12345
  • Using strace
    • A script to list all your application's syscalls using strace.
      I contributed it to firejail a few years ago:
    • https://github.com/netblue30/firejail/blob/master/contrib/syscalls.sh

    • wget "https://raw.githubusercontent.com/netblue30/firejail/c5d426b245b24d5bd432893f74baec04cb8b59ed/contrib/syscalls.sh" -O syscalls.sh
      
      chmod +x syscalls.sh
      
      ./syscalls.sh examples/http_request.py
      

• https://www.brendangregg.com/DTrace/DTrace-cheatsheet.pdf
  
  

TODO:

• Node support (dtrace hooks)
• Go support (dtrace hooks)
• Allow/Block list configuration
• Create a .yaml configuration per module in the code
  • Use secimport to compile that yml
  • Create a single dcript policy
  • Run an application with that policy using dtrace, without using secure_import