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

6 files changed, 38 insertions, 21 deletions

diff --git a/sys/fs/procfs/procfs_dbregs.c b/sys/fs/procfs/procfs_dbregs.c
index 158c3f4..c7ad130 100644
--- a/sys/fs/procfs/procfs_dbregs.c
+++ b/sys/fs/procfs/procfs_dbregs.c
@@ -62,7 +62,7 @@ procfs_dodbregs(curp, p, pfs, uio)
 	char *kv;
 	int kl;
 
-	if (p_trespass(curp, p))
+	if (p_can(curp, p, P_CAN_DEBUG, NULL))
 		return (EPERM);
 	kl = sizeof(r);
 	kv = (char *) &r;
diff --git a/sys/fs/procfs/procfs_fpregs.c b/sys/fs/procfs/procfs_fpregs.c
index 353b52b..69dd527 100644
--- a/sys/fs/procfs/procfs_fpregs.c
+++ b/sys/fs/procfs/procfs_fpregs.c
@@ -59,7 +59,7 @@ procfs_dofpregs(curp, p, pfs, uio)
 	char *kv;
 	int kl;
 
-	if (p_trespass(curp, p))
+	if (p_can(curp, p, P_CAN_DEBUG, NULL))
 		return EPERM;
 	kl = sizeof(r);
 	kv = (char *) &r;
diff --git a/sys/fs/procfs/procfs_mem.c b/sys/fs/procfs/procfs_mem.c
index b7eed85..6f2c8cb 100644
--- a/sys/fs/procfs/procfs_mem.c
+++ b/sys/fs/procfs/procfs_mem.c
@@ -256,7 +256,7 @@ procfs_domem(curp, p, pfs, uio)
  	 * All in all, quite yucky.
  	 */
  
- 	if (p_trespass(curp, p) &&
+ 	if (p_can(curp, p, P_CAN_DEBUG, NULL) &&
 	    !(uio->uio_rw == UIO_READ &&
 	      procfs_kmemaccess(curp)))
  		return EPERM;
diff --git a/sys/fs/procfs/procfs_regs.c b/sys/fs/procfs/procfs_regs.c
index 88f85d3..c2b6d4b 100644
--- a/sys/fs/procfs/procfs_regs.c
+++ b/sys/fs/procfs/procfs_regs.c
@@ -60,7 +60,7 @@ procfs_doregs(curp, p, pfs, uio)
 	char *kv;
 	int kl;
 
-	if (p_trespass(curp, p))
+	if (p_can(curp, p, P_CAN_DEBUG, NULL))
 		return EPERM;
 	kl = sizeof(r);
 	kv = (char *) &r;
diff --git a/sys/fs/procfs/procfs_status.c b/sys/fs/procfs/procfs_status.c
index 03149e9..c1adc60 100644
--- a/sys/fs/procfs/procfs_status.c
+++ b/sys/fs/procfs/procfs_status.c
@@ -183,7 +183,7 @@ procfs_docmdline(curp, p, pfs, uio)
 	 * Linux behaviour is to return zero-length in this case.
 	 */
 
-	if (p->p_args && (ps_argsopen ||!p_trespass(curp, p))) {
+	if (p->p_args && (ps_argsopen || !p_can(curp, p, P_CAN_SEE, NULL))) {
 		bp = p->p_args->ar_args;
 		buflen = p->p_args->ar_length;
 		buf = 0;
diff --git a/sys/fs/procfs/procfs_vnops.c b/sys/fs/procfs/procfs_vnops.c
index 35b3afb..df8e3ca 100644
--- a/sys/fs/procfs/procfs_vnops.c
+++ b/sys/fs/procfs/procfs_vnops.c
@@ -137,7 +137,7 @@ procfs_open(ap)
 	p2 = PFIND(pfs->pfs_pid);
 	if (p2 == NULL)
 		return (ENOENT);
-	if (pfs->pfs_pid && !PRISON_CHECK(ap->a_p, p2))
+	if (pfs->pfs_pid && p_can(ap->a_p, p2, P_CAN_SEE, NULL))
 		return (ENOENT);
 
 	switch (pfs->pfs_type) {
@@ -147,7 +147,7 @@ procfs_open(ap)
 			return (EBUSY);
 
 		p1 = ap->a_p;
-		if (p_trespass(p1, p2) &&
+		if (p_can(p1, p2, P_CAN_DEBUG, NULL) &&
 		    !procfs_kmemaccess(p1))
 			return (EPERM);
 
@@ -239,8 +239,11 @@ procfs_ioctl(ap)
 		return ENOTTY;
 	}
 
-	if (p_trespass(p, procp))
-		return EPERM;
+	if ((error = p_can(p, procp, P_CAN_DEBUG, NULL))) {
+		if (error == ESRCH)
+			error = ENOENT;
+		return (error);
+	}
 
 	switch (ap->a_command) {
 	case PIOCBIS:
@@ -417,6 +420,9 @@ procfs_getattr(ap)
 		if (procp == 0 || procp->p_cred == NULL ||
 		    procp->p_ucred == NULL)
 			return (ENOENT);
+
+		if (p_can(ap->a_p, procp, P_CAN_SEE, NULL))
+			return (ENOENT);
 	}
 
 	error = 0;
@@ -612,16 +618,23 @@ procfs_access(ap)
 		struct proc *a_p;
 	} */ *ap;
 {
+	struct pfsnode *pfs = VTOPFS(ap->a_vp);
+	struct proc *procp;
 	struct vattr *vap;
 	struct vattr vattr;
 	int error;
 
-	/*
-	 * If you're the super-user,
-	 * you always get access.
-	 */
-	if (ap->a_cred->cr_uid == 0)
-		return (0);
+	switch (pfs->pfs_type) {
+	case Proot:
+       	case Pcurproc:
+		break;
+	default:
+		procp = PFIND(pfs->pfs_pid);
+		if (procp == NULL)
+			return (ENOENT);
+		if (p_can(ap->a_p, procp, P_CAN_SEE, NULL))
+			return (ENOENT);
+        }
 
 	vap = &vattr;
 	error = VOP_GETATTR(ap->a_vp, vap, ap->a_cred, ap->a_p);
@@ -674,7 +687,7 @@ procfs_lookup(ap)
 	struct vnode **vpp = ap->a_vpp;
 	struct vnode *dvp = ap->a_dvp;
 	char *pname = cnp->cn_nameptr;
-	/* struct proc *curp = cnp->cn_proc; */
+	struct proc *curp = cnp->cn_proc;
 	struct proc_target *pt;
 	pid_t pid;
 	struct pfsnode *pfs;
@@ -683,7 +696,8 @@ procfs_lookup(ap)
 
 	*vpp = NULL;
 
-	if (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME)
+	if (cnp->cn_nameiop == DELETE || cnp->cn_nameiop == RENAME ||
+	    cnp->cn_nameiop == CREATE)
 		return (EROFS);
 
 	if (cnp->cn_namelen == 1 && *pname == '.') {
@@ -710,6 +724,9 @@ procfs_lookup(ap)
 		if (p == 0)
 			break;
 
+		if (p_can(curp, p, P_CAN_SEE, NULL))
+			break;
+
 		return (procfs_allocvp(dvp->v_mount, vpp, pid, Pproc));
 
 	case Pproc:
@@ -803,7 +820,7 @@ procfs_readdir(ap)
 		p = PFIND(pfs->pfs_pid);
 		if (p == NULL)
 			break;
-		if (!PRISON_CHECK(curproc, p))
+		if (p_can(curproc, p, P_CAN_SEE, NULL))
 			break;
 
 		for (pt = &proc_targets[i];
@@ -838,7 +855,7 @@ procfs_readdir(ap)
 		int doingzomb = 0;
 #endif
 		int pcnt = 0;
-		volatile struct proc *p = allproc.lh_first;
+		struct proc *p = allproc.lh_first;
 
 		for (; p && uio->uio_resid >= delen; i++, pcnt++) {
 			bzero((char *) dp, delen);
@@ -866,11 +883,11 @@ procfs_readdir(ap)
 					p = p->p_list.le_next;
 					if (!p)
 						goto done;
-					if (!PRISON_CHECK(curproc, p))
+					if (p_can(curproc, p, P_CAN_SEE, NULL))
 						continue;
 					pcnt++;
 				}
-				while (!PRISON_CHECK(curproc, p)) {
+				while (p_can(curproc, p, P_CAN_SEE, NULL)) {
 					p = p->p_list.le_next;
 					if (!p)
 						goto done;