Messages in this thread | | | Date | Wed, 28 Dec 2022 21:57:26 +0100 | From | Samuel Thibault <> | Subject | Re: [PATCH v3 2/2] tty: Allow TIOCSTI to be disabled |
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Hello,
Kees Cook, le mar. 27 déc. 2022 19:32:55 -0800, a ecrit: > On December 27, 2022 3:40:00 PM PST, Samuel Thibault <samuel.thibault@aquilenet.fr> wrote: > >Kees Cook, le sam. 22 oct. 2022 11:29:49 -0700, a ecrit: > >> TIOCSTI continues its long history of being used in privilege escalation > >> attacks[1]. Prior attempts to provide a mechanism to disable this have > >> devolved into discussions around creating full-blown LSMs to provide > >> arbitrary ioctl filtering, which is hugely over-engineered -- only > >> TIOCSTI is being used this way. 3 years ago OpenBSD entirely removed > >> TIOCSTI[2], Android has had it filtered for longer[3], and the tools that > >> had historically used TIOCSTI either do not need it, are not commonly > >> built with it, or have had its use removed. > > > >No. The Brltty screen reader entirely relies on TIOCSTI to be able to > >support input from various Braille devices. Please make sure to keep > >TIOCSTI enabled by default, otherwise some people would just completely > >lose their usual way of simply typing on Linux. > > Yup, it remains default enabled:
Yes, but thining of it, very soon people in various security-sensitive distributions will disable it, as they should indeed. And people who need to use their Braille device on such distributions will get stuck.
Can we perhaps just introduce a CAP_TIOCSTI that the brltty daemon would be able to use? We could even make it only allow TIOCSTI on the linux console (tty->ops == con_ops).
> Also, what does FreeBSD use for screen readers?
FreeBSD provides poor support for that, people have to use a patched screen tool to somehow access the console (but only after login).
Samuel
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