From: Kees Cook <kees@kernel.org>
To: Samuel Thibault <samuel.thibault@aquilenet.fr>,
Kees Cook <keescook@chromium.org>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
Jiri Slaby <jirislaby@kernel.org>,
Simon Brand <simon.brand@postadigitale.de>,
linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org
Subject: Re: [PATCH v3 2/2] tty: Allow TIOCSTI to be disabled
Date: Tue, 27 Dec 2022 19:32:55 -0800 [thread overview]
Message-ID: <C95AF535-7A95-48BA-8921-1932C15A1931@kernel.org> (raw)
In-Reply-To: <20221227234000.jgosvixx7eahqb3z@begin>
On December 27, 2022 3:40:00 PM PST, Samuel Thibault <samuel.thibault@aquilenet.fr> wrote:
>Hello,
>
>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:
> [...]
>> +config LEGACY_TIOCSTI
>> + bool "Allow legacy TIOCSTI usage"
>> + default y
>> + help
>> + Historically the kernel has allowed TIOCSTI, which will push
>> + characters into a controlling TTY. This continues to be used
>> + as a malicious privilege escalation mechanism, and provides no
>> + meaningful real-world utility any more.
>
>Yes it does.
Can you send a patch to adjust this language?
Also, what does FreeBSD use for screen readers?
-Kees
--
Kees Cook
next prev parent reply other threads:[~2022-12-28 3:33 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-22 18:29 [PATCH v3 0/2] tty: Allow TIOCSTI to be disabled Kees Cook
2022-10-22 18:29 ` [PATCH v3 1/2] tty: Move sysctl setup into "core" tty logic Kees Cook
2022-10-22 18:29 ` [PATCH v3 2/2] tty: Allow TIOCSTI to be disabled Kees Cook
2022-11-15 13:17 ` Geert Uytterhoeven
2022-12-27 23:40 ` Samuel Thibault
2022-12-27 23:41 ` Samuel Thibault
2022-12-28 3:32 ` Kees Cook [this message]
2022-12-28 20:57 ` Samuel Thibault
2023-06-25 15:56 ` Samuel Thibault
2023-06-27 21:50 ` Samuel Thibault
2023-06-28 0:21 ` Paul Moore
2023-06-28 2:48 ` Kees Cook
2023-06-28 6:07 ` Samuel Thibault
2023-06-28 16:32 ` Kees Cook
2023-07-02 0:00 ` Samuel Thibault
2023-07-03 19:41 ` Kees Cook
2023-06-29 13:23 ` David Laight
2023-06-29 13:32 ` Samuel Thibault
2022-11-02 2:15 ` [PATCH v3 0/2] " Kees Cook
2022-11-02 2:29 ` Greg Kroah-Hartman
2022-11-02 2:46 ` Kees Cook
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