arbitrary input from stdin to shell

Posted by python_noob on Stack Overflow See other posts from Stack Overflow or by python_noob
Published on 2012-07-04T21:14:13Z Indexed on 2012/07/04 21:15 UTC
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So I have this existing command that accepts a single argument, but I need something that accepts the argument over stdin instead.

A shell script wrapper like the following works, but as I will be allowing untrusted users to pass arbitrary strings on stdin, I'm wondering if there's potential for someone to execute arbitary commands on the shell.

#!/bin/sh
$CMD "`cat`"

Obviously if $CMD has a vulnerability in the way it processes the argument there's nothing I can do, so I'm concerned stuff like this:

  • Somehow allow the user to escape the double quotes and pass input into argument #2 of $CMD
  • Somehow cause another arbitary command to run

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