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Date: Mon, 10 Feb 2025 18:09:09 -0800
To: cygwin AT cygwin DOT com
Subject: Re: Potential Argument Injection Issue in Cygwin's Command Line
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On 2025-02-10 12:32, Brian Inglis via Cygwin wrote:
> One can avoid any issues by running Cygwin programs only from other Cygwin programs, and Windows programs only from other Windows programs.

Microsoft has provided a documented algorithm, which is implemented in the ShellAPI function CommandLineToArgvW, and in the CRT module that prepares arguments for the main or wmain functions of Microsoft Visual C/C++ programs.

I believe that the algorithm is sound in that it can round-trip any argv[] vector to string, and then back to recover an identical argv[].

(Am I correct?)

If that is the case, there is no reason why a POSIX layer on Windows would not use that algorithm, since it meets its requirements for passing an argv[] from one process to another, and is compatible with recommendations from the OS vendor, with a reference implementation (for the parsing direction) present in every Windows (ShellAPI).

What I've noticed in Cygwin is that it destroys the command line! When you call GetCommandLineW in a Cygwin process, you get an empty line. I recently posted here about this. That means you cannot ignore the arguments given in main() and just do it yourself.

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