The branch main has been updated by pjd: URL: https://cgit.FreeBSD.org/src/commit/?id=f1d0a0cbecf2c688061f35adea85bfb29c9ec893
commit f1d0a0cbecf2c688061f35adea85bfb29c9ec893 Author: Pawel Jakub Dawidek <[email protected]> AuthorDate: 2024-01-17 17:43:55 +0000 Commit: Pawel Jakub Dawidek <[email protected]> CommitDate: 2024-01-17 17:43:55 +0000 jail: Fix information leak. There is a lack of proper visibility checking in kern.ttys sysctl handler which leads to information leak about processes outside the current jail. This can be demonstrated with pstat -t: when called from within a jail, it will output all terminal devices including process groups and session leader process IDs: jail# pstat -t | grep pts/ | head LINE INQ CAN LIN LOW OUTQ USE LOW COL SESS PGID STATE pts/2 1920 0 0 192 1984 0 199 0 4132 27245 Oi pts/3 1920 0 0 192 1984 0 199 16 24890 33627 Oi pts/5 0 0 0 0 0 0 0 25 17758 0 G pts/16 0 0 0 0 0 0 0 0 52495 0 G pts/15 0 0 0 0 0 0 0 25 53446 0 G pts/17 0 0 0 0 0 0 0 6702 33230 0 G pts/19 0 0 0 0 0 0 0 14 1116 0 G pts/0 0 0 0 0 0 0 0 0 2241 0 G pts/23 0 0 0 0 0 0 0 20 15639 0 G pts/6 0 0 0 0 0 0 0 0 44062 93792 G jail# pstat -t | grep pts/ | wc -l 85 Devfs does the filtering correctly and we get only one entry: jail# ls /dev/pts/ 2 Approved by: mzaborski, secteam MFC after: 1 week Sponsored by: Fudo Security --- sys/kern/tty.c | 25 +++++++++++++++++++++---- 1 file changed, 21 insertions(+), 4 deletions(-) diff --git a/sys/kern/tty.c b/sys/kern/tty.c index 29bb092a50b0..ce72b250c526 100644 --- a/sys/kern/tty.c +++ b/sys/kern/tty.c @@ -1310,9 +1310,11 @@ static int sysctl_kern_ttys(SYSCTL_HANDLER_ARGS) { unsigned long lsize; + struct thread *td = curthread; struct xtty *xtlist, *xt; struct tty *tp; - int error; + struct proc *p; + int cansee, error; sx_slock(&tty_list_sx); lsize = tty_list_count * sizeof(struct xtty); @@ -1325,13 +1327,28 @@ sysctl_kern_ttys(SYSCTL_HANDLER_ARGS) TAILQ_FOREACH(tp, &tty_list, t_list) { tty_lock(tp); - tty_to_xtty(tp, xt); + if (tp->t_session != NULL) { + p = tp->t_session->s_leader; + PROC_LOCK(p); + cansee = (p_cansee(td, p) == 0); + PROC_UNLOCK(p); + } else { + cansee = !jailed(td->td_ucred); + } + if (cansee) { + tty_to_xtty(tp, xt); + xt++; + } tty_unlock(tp); - xt++; } sx_sunlock(&tty_list_sx); - error = SYSCTL_OUT(req, xtlist, lsize); + lsize = (xt - xtlist) * sizeof(struct xtty); + if (lsize > 0) { + error = SYSCTL_OUT(req, xtlist, lsize); + } else { + error = 0; + } free(xtlist, M_TTY); return (error); }
