B607: start_process_with_partial_path

bandit.plugins.injection_shell.start_process_with_partial_path(context, config)

B607: Test for starting a process with a partial path

Python possesses many mechanisms to invoke an external executable. If the desired executable path is not fully qualified relative to the filesystem root then this may present a potential security risk.

In POSIX environments, the PATH environment variable is used to specify a set of standard locations that will be searched for the first matching named executable. While convenient, this behavior may allow a malicious actor to exert control over a system. If they are able to adjust the contents of the PATH variable, or manipulate the file system, then a bogus executable may be discovered in place of the desired one. This executable will be invoked with the user privileges of the Python process that spawned it, potentially a highly privileged user.

This test will scan the parameters of all configured Python methods, looking for paths that do not start at the filesystem root, that is, do not have a leading ‘/’ character.

Config Options:

This plugin test shares a configuration with others in the same family, namely shell_injection. This configuration is divided up into three sections, subprocess, shell and no_shell. They each list Python calls that spawn subprocesses, invoke commands within a shell, or invoke commands without a shell (by replacing the calling process) respectively.

This test will scan parameters of all methods in all sections. Note that methods are fully qualified and de-aliased prior to checking.

shell_injection:
    # Start a process using the subprocess module, or one of its
    wrappers.
    subprocess:
        - subprocess.Popen
        - subprocess.call

    # Start a process with a function vulnerable to shell injection.
    shell:
        - os.system
        - os.popen
        - popen2.Popen3
        - popen2.Popen4
        - commands.getoutput
        - commands.getstatusoutput
    # Start a process with a function that is not vulnerable to shell
    injection.
    no_shell:
        - os.execl
        - os.execle

Example:

>> Issue: Starting a process with a partial executable path
Severity: Low   Confidence: High
Location: ./examples/partial_path_process.py:3
2    from subprocess import Popen as pop
3    pop('gcc --version', shell=False)

See also

• https://security.openstack.org
• https://docs.python.org/2/library/os.html#process-management

New in version 0.13.0.