B609: linux_commands_wildcard_injection

B609: Test for use of wildcard injection

Python provides a number of methods that emulate the behavior of standard Linux command line utilities. Like their Linux counterparts, these commands may take a wildcard “*” character in place of a file system path. This is interpreted to mean “any and all files or folders” and can be used to build partially qualified paths, such as “/home/user/*”.

The use of partially qualified paths may result in unintended consequences if an unexpected file or symlink is placed into the path location given. This becomes particularly dangerous when combined with commands used to manipulate file permissions or copy data off of a system.

This test plugin looks for usage of the following commands in conjunction with wild card parameters:

  • ‘chown’
  • ‘chmod’
  • ‘tar’
  • ‘rsync’

As well as any method configured in the shell or subprocess injection test configurations.

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: Possible wildcard injection in call: subprocess.Popen
   Severity: High   Confidence: Medium
   Location: ./examples/wildcard-injection.py:8
7    o.popen2('/bin/chmod *')
8    subp.Popen('/bin/chown *', shell=True)
9

>> Issue: subprocess call - check for execution of untrusted input.
   Severity: Low   Confidence: High
   Location: ./examples/wildcard-injection.py:11
10   # Not vulnerable to wildcard injection
11   subp.Popen('/bin/rsync *')
12   subp.Popen("/bin/chmod *")

See also

New in version 0.9.0.