FreeBSD Security Advisory FreeBSD-SA-21:05.jail_chdir
24 February, 2021 by firstname.lastname@example.org | freebsd
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA512 ============================================================================= FreeBSD-SA-21:05.jail_chdir Security Advisory The FreeBSD Project Topic: jail_attach(2) relies on the caller to change the cwd Category: core Module: jail Announced: 2021-02-24 Credits: Mateusz Guzik Affects: All supported versions of FreeBSD. Corrected: 2021-02-22 05:49:40 UTC (stable/13, 13.0-STABLE) 2021-02-22 18:25:23 UTC (releng/13.0, 13.0-BETA3-p1) 2021-02-22 19:03:43 UTC (stable/12, 12.2-STABLE) 2021-02-24 01:43:47 UTC (releng/12.2, 12.2-RELEASE-p4) 2021-02-22 19:08:27 UTC (stable/11, 11.4-STABLE) 2021-02-24 01:41:46 UTC (releng/11.4, 11.4-RELEASE-p8) CVE Name: CVE-2020-25582 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. The jail_attach(2) system call, which was introduced in FreeBSD 5 before 5.1-RELEASE, allows a non-jailed process to permanently move into an existing jail. The ptrace(2) system call provides tracing and debugging facilities by allowing one process (the tracing process) to watch and control another (the traced process). II. Problem Description When a process, such as jexec(8) or killall(1), calls jail_attach(2) to enter a jail, the jailed root can attach to it using ptrace(2) before the current working directory is changed. III. Impact A process with superuser privileges running inside a jail could change the root directory outside of the jail, thereby gaining full read and writing access to all files and directories in the system. IV. Workaround No workaround is available, but systems that are not running jails with untrusted root users are not vulnerable. 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 i386 or amd64 platforms 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. [FreeBSD 13.x] # fetch https://security.FreeBSD.org/patches/SA-21:05/jail_chdir.13.patch # fetch https://security.FreeBSD.org/patches/SA-21:05/jail_chdir.13.patch.asc # gpg --verify jail_chdir.13.patch.asc [FreeBSD 11.x, FreeBSD 12.x] # fetch https://security.FreeBSD.org/patches/SA-21:05/jail_chdir.patch # fetch https://security.FreeBSD.org/patches/SA-21:05/jail_chdir.patch.asc # gpg --verify jail_chdir.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 The following list contains the correction revision numbers for each affected branch. Branch/path Revision - ------------------------------------------------------------------------- stable/13/ 5dbb407145c8128753fa30b695bc266dc671e433 releng/13.0/ f3f042d850baaeda1bed19e00c2b3b578644b7e9 stable/12/ r369334 releng/12.2/ r369354 stable/11/ r369335 releng/11.4/ r369348 - ------------------------------------------------------------------------- [FreeBSD 13.x] To see which files were modified by a particular revision, run the following command in a checked out git repository, replacing NNNNNN with the revision hash: # git show --stat NNNNNN Or visit the following URL, replace NNNNNN with the revision hash: <URL:https://cgit.freebsd.org/src/commit/?id=NNNNNN> [FreeBSD 11.x, FreeBSD 12.x] To see which files were modified by a particular revision, run the following command, replacing NNNNNN with the revision number, on a machine with Subversion installed: # svn diff -cNNNNNN --summarize svn://svn.freebsd.org/base Or visit the following URL, replacing NNNNNN with the revision number: <URL:https://svnweb.freebsd.org/base?view=revision&revision=NNNNNN> VII. References <URL:https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-25582> The latest revision of this advisory is available at <URL:https://security.FreeBSD.org/advisories/FreeBSD-SA-21:05.jail_chdir.asc> -----BEGIN PGP SIGNATURE----- iQIzBAEBCgAdFiEE/A6HiuWv54gCjWNV05eS9J6n5cIFAmA15dYACgkQ05eS9J6n 5cKj/xAAjbGc0bV3Ua8PuIFoDk7ADnwNotFV9PlXknWpeM4fXVVrt5EDncMfgHdw XeKHOjzKNocOCtDioDhOcev9hhLeiYJjGHKrOQeKv34hJoufd6Wr0nvLgv/IVlMr iZRVndvG1eBlnkwzlbx0xh1OY9zhffqjEiVkQNxXZV0iz/P2ndG0wP7N/bTG2QW3 1mZmp4Fh9AsbjLPVGyutoLZXiypuroGPLQZrth3n7Cz8HklwyPzoAgPOYx7mMW3D x1Th6kYIEx1aCe+ZBsgOuPsKeZ4SSB5o1w2F5y+mor/rslgQJAppNakBMmyDkSEI UhEqLGNA469P0qonCHhGY83wfkuUedFTuWLrdnh97J7yr+WIn1ik1/jBXxv3+1kS bKivBd/oj6hEFULE7r6T/UVomJjU+dPPBm+ewljJFVib+3zIQsbxauLdqUuqWlob QUkQc4mu7fjVSAMyVbYVrjBAgwQJit0KfX+JSbEcLndmPv1RCK8wnxIf0zbmV2m/ DMg9QGqwfcJkba6Y/JCAFZcl+HUCfEGUqZ7pEqGuwsp3wnMwO7Qg9IAEmDt8i2lf 6kaqAatJ5Reo/D+j6KJFvGCajnEfD0n+jDx8cdJFNY2Zzbo3/lRGd8dque5OEbTA O0UZu2hRv5YMIagMf57WWzGrF+ACtgYbath710IKfVUfP/OiCIM= =/d5L -----END PGP SIGNATURE----- _______________________________________________ email@example.com mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-announce To unsubscribe, send any mail to "firstname.lastname@example.org"