Date: Thu, 14 Jun 2018 20:12:59 +0200 From: Jakub Wilk <jwilk@...lk.net> To: oss-security@...ts.openwall.com Subject: Re: Are `su user' and/or `sudo -u user sh' considered dangerous? * Georgi Guninski <guninski@...inski.com>, 2018-06-13, 12:54: >>Is there POC for relatively new distros? >debian 8 and 9 are vulnerable to su - hostile: >https://j.ludost.net/blog/archives/2018/06/13/ancient_su_-_hostile_vulnerability_in_debian_8_and_9/index.html (Please fix unescaped "<" and "&" characters on that page.) For Debian this bug is tracked here: https://bugs.debian.org/628843 >what about the second potential vulnerability: reading root's tty after >the session is closed with something like tee(1) ? The list of nasty things you can do when you get your hands on the tty fd is probably very long... >several sources suggest disabling TIOCSTI or using setsid(), are they >enough? setsid() defeats TIOCSTI (while breaking other things like job control...); it doesn't stop other attacks that don't require controlling terminal. Until su is fixed to allocate new pty, I recommend running it under a standalone terminal emulator, such as screen or tmux. This has also an advantage that it's possible to tell that the invoked program actually terminated, instead of just pretending to terminate and faking root shell UI. -- Jakub Wilk
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