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Asked: 2026-05-19T09:12:29+00:00

What is the common practice to sanitize a filename from an outside source (e.g.:

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What is the common practice to sanitize a filename from an outside source (e.g.: xml file) before using it within a subprocess (shell=False)?

Update:
Before sending some parsed strings around I would like to make some basic security checks. The given example uses mpg123 (a command line audioplayer) in remote mode to play a sound file.

filename = child.find("filename").text # e.g.: filename = "sound.mp3"
pid = subprocess.Popen(["mpg123"],"-R"], stdin=subprocess.PIPE, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
command = "L "+filename+"\n"  
pid.stdin.write(command.encode())
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1 Answer

  1. Editorial Team

    Filenames doesn’t need to be sanitized unless you are using a shell or executing anything. Pythons open() will not execute any commands in the filename given.

    For security checks, to avoid overwriting files, you use the permission system of your OS, and make sure that the user under which the program is running only can overwrite and access files it should be able to overwrite and access.

    It’s generally not a good idea to let any program that takes input from the net or another process to accept absolute path names. In this case it should only be allowed to specify files under a defined music folder. I don’t think the mp3 player can cause damage by giving it the wrong file, but you can crash it, at least, and that would be annoying.

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