[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Passing script by fd on Linux and setuid scripts

From: Petr Skočík
Subject: Passing script by fd on Linux and setuid scripts
Date: Sun, 31 Jul 2016 22:10:39 +0200
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.2.0


The bash reference mentions that /dev/fd/* files are treated specially,
as filedescriptors, when used in conditionals.

However, they're not if they're passed as script arguments to the bash
binary (e.g., `bash /dev/fd/3`).

If they were, it would be possible to have a small setuid-root
indirection binary start bash scripts via filedescriptors, thereby
eliminating the race condition setuid-script vulnerability mentioned in
Gilles's answer at

(Whether the rest of the execution would be secure with setuid is
another question)

Running readlink on the actual /dev/fd/$something could then be used to
set $0.

I think it would make sense. What do you think?

Attached is a tentative patch that implements the above described

Best regards,
Petr Skocik

Attachment: passing-scripts-via-fds.patch
Description: Text Data

reply via email to

[Prev in Thread] Current Thread [Next in Thread]