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FreeBSD-SA-24:02.tty                                        Security Advisory
                                                          The FreeBSD Project

Topic:          jail(2) information leak

Category:       core
Module:         jail
Announced:      2024-02-14
Credits:        Pawel Jakub Dawidek
Affects:        All supported versions of FreeBSD.
Corrected:      2024-02-12 16:25:54 UTC (stable/14, 14.0-STABLE)
                2024-02-14 06:05:46 UTC (releng/14.0, 14.0-RELEASE-p5)
                2024-02-12 16:27:37 UTC (stable/13, 13.2-STABLE)
                2024-02-14 06:06:01 UTC (releng/13.2, 13.2-RELEASE-p10)
CVE Name:       CVE-2024-25941

For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit <URL:https://security.FreeBSD.org/>.

I.   Background

The jail(2) system call allows a system administrator to lock a process
and all of its descendants inside an environment with a very limited
ability to affect the system outside that environment, even for
processes with superuser privileges.  It is an extension of, but
far more powerful than, the traditional UNIX chroot(2) system call.

tty(4) is a general terminal device.

II.  Problem Description

The jail(2) system call has not limited a visiblity of allocated TTYs
(the kern.ttys sysctl).  This gives rise to an information leak about
processes outside the current jail.

III. Impact

Attacker can get information about TTYs allocated on the host or in other
jails.  Effectively, the information printed by "pstat -t" may be leaked.

IV.  Workaround

No workaround is available.

V.   Solution

Upgrade your vulnerable system to a supported FreeBSD stable or
release / security branch (releng) dated after the correction date
and reboot.

Perform one of the following:

1) To update your vulnerable system via a binary patch:

Systems running a RELEASE version of FreeBSD on the amd64 or arm64 platforms,
or the i386 platform on FreeBSD 13, can be updated via the freebsd-update(8)
utility:

# freebsd-update fetch
# freebsd-update install
# shutdown -r +10min "Rebooting for a security update"

2) To update your vulnerable system via a source code patch:

The following patches have been verified to apply to the applicable
FreeBSD release branches.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

# fetch https://security.FreeBSD.org/patches/SA-24:02/tty.patch
# fetch https://security.FreeBSD.org/patches/SA-24:02/tty.patch.asc
# gpg --verify tty.patch.asc

b) Apply the patch.  Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch

c) Recompile your kernel as described in
<URL:https://www.FreeBSD.org/handbook/kernelconfig.html> and reboot the
system.

VI.  Correction details

This issue is corrected as of the corresponding Git commit hash in the
following stable and release branches:

Branch/path                             Hash                     Revision
- -------------------------------------------------------------------------
stable/14/                              215bb03edc54    stable/14-n266676
releng/14.0/                            4d354159d150  releng/14.0-n265407
stable/13/                              9bff7ec98354    stable/13-n257418
releng/13.2/                            17257e6e9a23  releng/13.2-n254658
- -------------------------------------------------------------------------

Run the following command to see which files were modified by a
particular commit:

# git show --stat <commit hash>

Or visit the following URL, replacing NNNNNN with the hash:

<URL:https://cgit.freebsd.org/src/commit/?id=NNNNNN>

To determine the commit count in a working tree (for comparison against
nNNNNNN in the table above), run:

# git rev-list --count --first-parent HEAD

VII. References

<URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2024-25941>

The latest revision of this advisory is available at
<URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-24:02.tty.asc>
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