o Centralize inter-process access control, introducing:

    int p_can(p1, p2, operation, privused)

  which allows specification of subject process, object process,
  inter-process operation, and an optional call-by-reference privused
  flag, allowing the caller to determine if privilege was required
  for the call to succeed.  This allows jail, kern.ps_showallprocs and
  regular credential-based interaction checks to occur in one block of
  code.  Possible operations are P_CAN_SEE, P_CAN_SCHED, P_CAN_KILL,
  and P_CAN_DEBUG.  p_can currently breaks out as a wrapper to a
  series of static function checks in kern_prot, which should not
  be invoked directly.

o Commented out capabilities entries are included for some checks.

o Update most inter-process authorization to make use of p_can() instead
  of manual checks, PRISON_CHECK(), P_TRESPASS(), and
  kern.ps_showallprocs.

o Modify suser{,_xxx} to use const arguments, as it no longer modifies
  process flags due to the disabling of ASU.

o Modify some checks/errors in procfs so that ENOENT is returned instead
  of ESRCH, further improving concealment of processes that should not
  be visible to other processes.  Also introduce new access checks to
  improve hiding of processes for procfs_lookup(), procfs_getattr(),
  procfs_readdir().  Correct a bug reported by bp concerning not
  handling the CREATE case in procfs_lookup().  Remove volatile flag in
  procfs that caused apparently spurious qualifier warnigns (approved by
  bde).

o Add comment noting that ktrace() has not been updated, as its access
  control checks are different from ptrace(), whereas they should
  probably be the same.  Further discussion should happen on this topic.

Reviewed by:	bde, green, phk, freebsd-security, others
Approved by:	bde
Obtained from:	TrustedBSD Project

1 files changed, 11 insertions, 10 deletions

diff --git a/sys/kern/kern_resource.c b/sys/kern/kern_resource.c
index 5af09c9..b3c2ec6 100644
--- a/sys/kern/kern_resource.c
+++ b/sys/kern/kern_resource.c
@@ -88,7 +88,7 @@ getpriority(curp, uap)
 			p = pfind(uap->who);
 		if (p == 0)
 			break;
-		if (!PRISON_CHECK(curp, p))
+		if (p_can(curp, p, P_CAN_SEE, NULL))
 			break;
 		low = p->p_nice;
 		break;
@@ -101,7 +101,7 @@ getpriority(curp, uap)
 		else if ((pg = pgfind(uap->who)) == NULL)
 			break;
 		LIST_FOREACH(p, &pg->pg_members, p_pglist) {
-			if ((PRISON_CHECK(curp, p) && p->p_nice < low))
+			if (!p_can(curp, p, P_CAN_SEE, NULL) && p->p_nice < low)
 				low = p->p_nice;
 		}
 		break;
@@ -111,7 +111,7 @@ getpriority(curp, uap)
 		if (uap->who == 0)
 			uap->who = curp->p_ucred->cr_uid;
 		LIST_FOREACH(p, &allproc, p_list)
-			if (PRISON_CHECK(curp, p) &&
+			if (!p_can(curp, p, P_CAN_SEE, NULL) &&
 			    p->p_ucred->cr_uid == uap->who &&
 			    p->p_nice < low)
 				low = p->p_nice;
@@ -151,7 +151,7 @@ setpriority(curp, uap)
 			p = pfind(uap->who);
 		if (p == 0)
 			break;
-		if (!PRISON_CHECK(curp, p))
+		if (p_can(curp, p, P_CAN_SEE, NULL))
 			break;
 		error = donice(curp, p, uap->prio);
 		found++;
@@ -165,7 +165,7 @@ setpriority(curp, uap)
 		else if ((pg = pgfind(uap->who)) == NULL)
 			break;
 		LIST_FOREACH(p, &pg->pg_members, p_pglist) {
-			if (PRISON_CHECK(curp, p)) {
+			if (!p_can(curp, p, P_CAN_SEE, NULL)) {
 				error = donice(curp, p, uap->prio);
 				found++;
 			}
@@ -178,7 +178,7 @@ setpriority(curp, uap)
 			uap->who = curp->p_ucred->cr_uid;
 		LIST_FOREACH(p, &allproc, p_list)
 			if (p->p_ucred->cr_uid == uap->who &&
-			    PRISON_CHECK(curp, p)) {
+			    !p_can(curp, p, P_CAN_SEE, NULL)) {
 				error = donice(curp, p, uap->prio);
 				found++;
 			}
@@ -197,9 +197,10 @@ donice(curp, chgp, n)
 	register struct proc *curp, *chgp;
 	register int n;
 {
+	int	error;
 
-	if (p_trespass(curp, chgp) != 0)
-		return (EPERM);
+	if ((error = p_can(curp, chgp, P_CAN_SCHED, NULL)))
+		return (error);
 	if (n > PRIO_MAX)
 		n = PRIO_MAX;
 	if (n < PRIO_MIN)
@@ -250,8 +251,8 @@ rtprio(curp, uap)
 	case RTP_LOOKUP:
 		return (copyout(&p->p_rtprio, uap->rtp, sizeof(struct rtprio)));
 	case RTP_SET:
-		if (p_trespass(curp, p) != 0)
-		        return (EPERM);
+		if ((error = p_can(curp, p, P_CAN_SCHED, NULL)))
+		        return (error);
 		/* disallow setting rtprio in most cases if not superuser */
 		if (suser(curp) != 0) {
 			/* can't set someone else's */