Introduce p_canwait() and MAC Framework and MAC Policy entry points

mac_check_proc_wait(), which control the ability to wait4() specific
processes.  This permits MAC policies to limit information flow from
children that have changed label, although has to be handled carefully
due to common programming expectations regarding the behavior of
wait4().  The cr_seeotheruids() check in p_canwait() is #if 0'd for
this reason.

The mac_stub and mac_test policies are updated to reflect these new
entry points.

Sponsored by:	SPAWAR, SPARTA
Obtained from:	TrustedBSD Project

10 files changed, 76 insertions, 0 deletions

diff --git a/sys/kern/kern_exit.c b/sys/kern/kern_exit.c
index e27e9b0..8b31e35 100644
--- a/sys/kern/kern_exit.c
+++ b/sys/kern/kern_exit.c
@@ -597,6 +597,10 @@ loop:
 			PROC_UNLOCK(p);
 			continue;
 		}
+		if (p_canwait(td, p)) {
+			PROC_UNLOCK(p);
+			continue;
+		}
 
 		/*
 		 * This special case handles a kthread spawned by linux_clone
diff --git a/sys/kern/kern_prot.c b/sys/kern/kern_prot.c
index 56ec0dd..ebe4b18 100644
--- a/sys/kern/kern_prot.c
+++ b/sys/kern/kern_prot.c
@@ -1800,6 +1800,37 @@ cr_canseesocket(struct ucred *cred, struct socket *so)
 	return (0);
 }
 
+/*-
+ * Determine whether td can wait for the exit of p.
+ * Returns: 0 for permitted, an errno value otherwise
+ * Locks: Sufficient locks to protect various components of td and p
+ *        must be held.  td must be curthread, and a lock must
+ *        be held for p.
+ * References: td and p must be valid for the lifetime of the call
+
+ */
+int
+p_canwait(struct thread *td, struct proc *p)
+{
+	int error;
+
+	KASSERT(td == curthread, ("%s: td not curthread", __func__));
+	PROC_LOCK_ASSERT(p, MA_OWNED);
+	if ((error = prison_check(td->td_ucred, p->p_ucred)))
+		return (error);
+#ifdef MAC
+	if ((error = mac_check_proc_wait(td->td_ucred, p)))
+		return (error);
+#endif
+#if 0
+	/* XXXMAC: This could have odd effects on some shells. */
+	if ((error = cr_seeotheruids(td->td_ucred, p->p_ucred)))
+		return (error);
+#endif
+
+	return (0);
+}
+
 /*
  * Allocate a zeroed cred structure.
  * MPSAFE
diff --git a/sys/security/mac/mac_framework.h b/sys/security/mac/mac_framework.h
index f72733d..8e5037a 100644
--- a/sys/security/mac/mac_framework.h
+++ b/sys/security/mac/mac_framework.h
@@ -351,6 +351,7 @@ int	mac_check_proc_setresgid(struct proc *proc, struct ucred *cred,
 	    gid_t rgid, gid_t egid, gid_t sgid);
 int	mac_check_proc_signal(struct ucred *cred, struct proc *proc,
 	    int signum);
+int	mac_check_proc_wait(struct ucred *cred, struct proc *proc);
 int	mac_check_socket_accept(struct ucred *cred, struct socket *so);
 int	mac_check_socket_bind(struct ucred *cred, struct socket *so,
 	    struct sockaddr *sockaddr);
diff --git a/sys/security/mac/mac_policy.h b/sys/security/mac/mac_policy.h
index 402d622..e519cb3 100644
--- a/sys/security/mac/mac_policy.h
+++ b/sys/security/mac/mac_policy.h
@@ -424,6 +424,8 @@ struct mac_policy_ops {
 		    gid_t egid, gid_t sgid);
 	int	(*mpo_check_proc_signal)(struct ucred *cred,
 		    struct proc *proc, int signum);
+	int	(*mpo_check_proc_wait)(struct ucred *cred,
+		    struct proc *proc);
 	int	(*mpo_check_socket_accept)(struct ucred *cred,
 		    struct socket *so, struct label *socketlabel);
 	int	(*mpo_check_socket_bind)(struct ucred *cred,
diff --git a/sys/security/mac/mac_process.c b/sys/security/mac/mac_process.c
index 8dda7b1..436c55b 100644
--- a/sys/security/mac/mac_process.c
+++ b/sys/security/mac/mac_process.c
@@ -650,3 +650,18 @@ mac_check_proc_setresgid(struct proc *proc, struct ucred *cred, gid_t rgid,
 	MAC_CHECK(check_proc_setresgid, cred, rgid, egid, sgid);
 	return (error);
 }
+
+int
+mac_check_proc_wait(struct ucred *cred, struct proc *proc)
+{
+	int error;
+
+	PROC_LOCK_ASSERT(proc, MA_OWNED);
+
+	if (!mac_enforce_process)
+		return (0);
+
+	MAC_CHECK(check_proc_wait, cred, proc);
+
+	return (error);
+}
diff --git a/sys/security/mac_stub/mac_stub.c b/sys/security/mac_stub/mac_stub.c
index 9a7f567..64a06d9 100644
--- a/sys/security/mac_stub/mac_stub.c
+++ b/sys/security/mac_stub/mac_stub.c
@@ -842,6 +842,13 @@ stub_check_proc_signal(struct ucred *cred, struct proc *proc, int signum)
 }
 
 static int
+stub_check_proc_wait(struct ucred *cred, struct proc *proc)
+{
+
+	return (0);
+}
+
+static int
 stub_check_proc_setuid(struct ucred *cred, uid_t uid)
 {
 
@@ -1456,6 +1463,7 @@ static struct mac_policy_ops mac_stub_ops =
 	.mpo_check_proc_setresuid = stub_check_proc_setresuid,
 	.mpo_check_proc_setresgid = stub_check_proc_setresgid,
 	.mpo_check_proc_signal = stub_check_proc_signal,
+	.mpo_check_proc_wait = stub_check_proc_wait,
 	.mpo_check_socket_accept = stub_check_socket_accept,
 	.mpo_check_socket_bind = stub_check_socket_bind,
 	.mpo_check_socket_connect = stub_check_socket_connect,
diff --git a/sys/security/mac_test/mac_test.c b/sys/security/mac_test/mac_test.c
index 1ce97a3..b2fa853 100644
--- a/sys/security/mac_test/mac_test.c
+++ b/sys/security/mac_test/mac_test.c
@@ -1791,6 +1791,16 @@ mac_test_check_proc_setresgid(struct ucred *cred, gid_t rgid, gid_t egid,
 }
 
 static int
+mac_test_check_proc_wait(struct ucred *cred, struct proc *proc)
+{
+
+	ASSERT_CRED_LABEL(cred->cr_label);
+	ASSERT_CRED_LABEL(proc->p_ucred->cr_label);
+
+	return (0);
+}
+
+static int
 mac_test_check_socket_accept(struct ucred *cred, struct socket *socket,
     struct label *socketlabel)
 {
@@ -2506,6 +2516,7 @@ static struct mac_policy_ops mac_test_ops =
 	.mpo_check_proc_setresuid = mac_test_check_proc_setresuid,
 	.mpo_check_proc_setresgid = mac_test_check_proc_setresgid,
 	.mpo_check_proc_signal = mac_test_check_proc_signal,
+	.mpo_check_proc_wait = mac_test_check_proc_wait,
 	.mpo_check_socket_accept = mac_test_check_socket_accept,
 	.mpo_check_socket_bind = mac_test_check_socket_bind,
 	.mpo_check_socket_connect = mac_test_check_socket_connect,
diff --git a/sys/sys/mac.h b/sys/sys/mac.h
index f72733d..8e5037a 100644
--- a/sys/sys/mac.h
+++ b/sys/sys/mac.h
@@ -351,6 +351,7 @@ int	mac_check_proc_setresgid(struct proc *proc, struct ucred *cred,
 	    gid_t rgid, gid_t egid, gid_t sgid);
 int	mac_check_proc_signal(struct ucred *cred, struct proc *proc,
 	    int signum);
+int	mac_check_proc_wait(struct ucred *cred, struct proc *proc);
 int	mac_check_socket_accept(struct ucred *cred, struct socket *so);
 int	mac_check_socket_bind(struct ucred *cred, struct socket *so,
 	    struct sockaddr *sockaddr);
diff --git a/sys/sys/mac_policy.h b/sys/sys/mac_policy.h
index 402d622..e519cb3 100644
--- a/sys/sys/mac_policy.h
+++ b/sys/sys/mac_policy.h
@@ -424,6 +424,8 @@ struct mac_policy_ops {
 		    gid_t egid, gid_t sgid);
 	int	(*mpo_check_proc_signal)(struct ucred *cred,
 		    struct proc *proc, int signum);
+	int	(*mpo_check_proc_wait)(struct ucred *cred,
+		    struct proc *proc);
 	int	(*mpo_check_socket_accept)(struct ucred *cred,
 		    struct socket *so, struct label *socketlabel);
 	int	(*mpo_check_socket_bind)(struct ucred *cred,
diff --git a/sys/sys/proc.h b/sys/sys/proc.h
index 1af6b71..7a151bb 100644
--- a/sys/sys/proc.h
+++ b/sys/sys/proc.h
@@ -851,6 +851,7 @@ int	p_candebug(struct thread *td, struct proc *p);
 int	p_cansee(struct thread *td, struct proc *p);
 int	p_cansched(struct thread *td, struct proc *p);
 int	p_cansignal(struct thread *td, struct proc *p, int signum);
+int	p_canwait(struct thread *td, struct proc *p);
 struct	pargs *pargs_alloc(int len);
 void	pargs_drop(struct pargs *pa);
 void	pargs_free(struct pargs *pa);