RUSTSEC-2021-0071

On Windows in versions of grep-cli prior to 0.1.6, it's possible for some of the routines to execute arbitrary executables. In particular, a quirk of the Windows process execution API is that it will automatically consider the current directory before other directories when resolving relative binary names. Therefore, if you use grep-cli to read decompressed files in an untrusted directory with that directory as the CWD, a malicious actor to could put, e.g., a gz.exe binary in that directory and grep-cli will use the malicious actor's version of gz.exe instead of the system's.

This is also technically possible on Unix as well, but only if the PATH variable contains .. Conventionally, they do not.

A DecompressionReader has been fixed to automatically resolve binary names using PATH, instead of relying on the Windows API to do it.

If you use grep-cli's CommandReader with a std::process::Command value on Windows, then it is recommended to either construct the Command with an absolute binary name, or use grep-cli's new resolve_binary helper function.

To be clear, grep-cli 0.1.6 mitigates this issue in two ways:

• A DecompressionReader will resolve decompression programs to absolute paths automatically using the PATH environment variable, instead of relying on Windows APIs to do it (which would result in the undesirable behavior of checking the CWD for a program first).
• A new function, resolve_binary, was added to help users of this crate mitigate this behavior when they need to create their own std::process::Command. For example, ripgrep uses grep_cli::resolve_binary on the argument given to its --pre flag.

While the first mitigation fixes this issue for sensible values of PATH when doing decompression search, the second mitigation is imperfect. The more fundamental issue is that std::process::Command is itself vulnerable to this.