Messages in this thread | | | Date | Tue, 11 Oct 2022 14:12:21 -0700 | Subject | Re: Possibility to disable icotl TIOCSTI | From | Randy Dunlap <> |
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On 10/6/22 11:48, Simon Brand wrote: > Hello, > > in the past there have been attempts to restrict the TIOCSTI ioctl. [0, 1] > None of them are present in the current kernel. > Since those tries there have been some security issues (sandbox > escapes in flatpak (CVE-2019-10063) [2] and snap (CVE 2019-7303) [3], > runuser [4], su [5]). > > I ask to merge the patches from linux-hardening [6, 7] so users can > opt out of this behavior. These patches provide the > `SECURITY_TIOCSTI_RESTRICT` Kconfig (default no) and a > `tiocsti_restrict` sysctl.
Please send to the hardening mailing list and/or hardening maintainer.
> Escapes can be reproduced easiliy (on archlinux) via a python script: > ``` > import fcntl > import termios > with open("/dev/tty", "w") as fd: > for c in "id\n": > fcntl.ioctl(fd, termios.TIOCSTI, c) > ``` > Now run as root: > # su user > $ python3 /path/to/script.py ; exit > uid=0(root) ... > > At least to me, this result was not expected. > > I asked it before on kernelnewbies mailing list. [8] > Please set me in CC, because I have not subscribed to this list. > > Best and thank you, > Simon > > [0] https://lkml.kernel.org/lkml/CAG48ez1NBnrsPnHN6D9nbOJP6+Q6zEV9vfx9q7ME4Eti-vRmhQ@mail.gmail.com/T/ > [1] https://lkml.kernel.org/lkml/20170420174100.GA16822@mail.hallyn.com/T/ > [2] https://github.com/flatpak/flatpak/issues/2782 > [3] https://wiki.ubuntu.com/SecurityTeam/KnowledgeBase/SnapIoctlTIOCSTI > [4] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=815922 > [5] https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=628843 > [6] https://github.com/anthraxx/linux-hardened/commit/d0e49deb1a39dc64e7c7db3340579 > [7] https://github.com/anthraxx/linux-hardened/commit/ea8f20602a993c90125bf08da3989 > [8] https://www.spinics.net/lists/newbies/msg64019.html
-- ~Randy
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