Date: Tue, 12 Jun 2018 13:38:36 +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>, 2018-06-12, 13:17: >https://j.ludost.net/blog/archives/2018/06/12/are_su_user_andor_sudo_-u_user_sh_considered_dangerous/index.html > >Per vague memory I discussed half of this with some linux crowd and >they said "won't fix" long ago. > >`su user' and `sudo -u user sh' give the user the fd of root's tty and >it is readable and writable. After closing the session, the user can >keep it and on root's tty potentially do: > >1. inject keypresses via ioctl() >and/or >2. read the output of root's tty, probably with some analogue of >tee(1). > >Is this really a concern? This class of vulnerabilities has been known since at least 2005: https://bugzilla.redhat.com/show_bug.cgi?id=173008 (CVE-2005-4890) It was last discussed on oss-security in 2017: http://seclists.org/oss-sec/2017/q2/412 >Any workarounds? For sudo, there's the "use_pty" flag. (It's not enabled by default.) -- Jakub Wilk
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