Implement mac_check_system_sysctl(), a MAC Framework entry point to

permit MAC policies to augment the security protections on sysctl()
operations.  This is not really a wonderful entry point, as we
only have access to the MIB of the target sysctl entry, rather than
the more useful entry name, but this is sufficient for policies
like Biba that wish to use their notions of privilege or integrity
to prevent inappropriate sysctl modification.  Affects MAC kernels
only.  Since SYSCTL_LOCK isn't in sysctl.h, just kern_sysctl.c,
we can't assert the SYSCTL subsystem lockin the MAC Framework.

Approved by:	re
Obtained from:	TrustedBSD Project
Sponsored by:	DARPA, Network Associates Laboratories

14 files changed, 277 insertions, 0 deletions

diff --git a/sys/kern/kern_mac.c b/sys/kern/kern_mac.c
index 00ecd04..c9ec6a1 100644
--- a/sys/kern/kern_mac.c
+++ b/sys/kern/kern_mac.c
@@ -151,6 +151,11 @@ SYSCTL_INT(_security_mac, OID_AUTO, enforce_socket, CTLFLAG_RW,
     &mac_enforce_socket, 0, "Enforce MAC policy on socket operations");
 TUNABLE_INT("security.mac.enforce_socket", &mac_enforce_socket);
 
+static int	mac_enforce_sysctl = 1;
+SYSCTL_INT(_security_mac, OID_AUTO, enforce_sysctl, CTLFLAG_RW,
+    &mac_enforce_sysctl, 0, "Enforce MAC policy on sysctl operations");
+TUNABLE_INT("security.mac.enforce_sysctl", &mac_enforce_sysctl);
+
 static int     mac_enforce_vm = 1;
 SYSCTL_INT(_security_mac, OID_AUTO, enforce_vm, CTLFLAG_RW,
     &mac_enforce_vm, 0, "Enforce MAC policy on vm operations");
@@ -912,6 +917,10 @@ mac_policy_register(struct mac_policy_conf *mpc)
 			mpc->mpc_ops->mpo_check_system_swapon =
 			    mpe->mpe_function;
 			break;
+		case MAC_CHECK_SYSTEM_SYSCTL:
+			mpc->mpc_ops->mpo_check_system_sysctl =
+			    mpe->mpe_function;
+			break;
 		case MAC_CHECK_VNODE_ACCESS:
 			mpc->mpc_ops->mpo_check_vnode_access =
 			    mpe->mpe_function;
@@ -3034,6 +3043,25 @@ mac_check_system_swapon(struct ucred *cred, struct vnode *vp)
 }
 
 int
+mac_check_system_sysctl(struct ucred *cred, int *name, u_int namelen,
+    void *old, size_t *oldlenp, int inkernel, void *new, size_t newlen)
+{
+	int error;
+
+	/*
+	 * XXXMAC: We're very much like to assert the SYSCTL_LOCK here,
+	 * but since it's not exported from kern_sysctl.c, we can't.
+	 */
+	if (!mac_enforce_sysctl)
+		return (0);
+
+	MAC_CHECK(check_system_sysctl, cred, name, namelen, old, oldlenp,
+	    inkernel, new, newlen);
+
+	return (error);
+}
+
+int
 mac_ioctl_ifnet_get(struct ucred *cred, struct ifreq *ifr,
     struct ifnet *ifnet)
 {
diff --git a/sys/kern/kern_sysctl.c b/sys/kern/kern_sysctl.c
index b229701..984e022 100644
--- a/sys/kern/kern_sysctl.c
+++ b/sys/kern/kern_sysctl.c
@@ -41,11 +41,13 @@
  */
 
 #include "opt_compat.h"
+#include "opt_mac.h"
 
 #include <sys/param.h>
 #include <sys/systm.h>
 #include <sys/kernel.h>
 #include <sys/sysctl.h>
+#include <sys/mac.h>
 #include <sys/malloc.h>
 #include <sys/proc.h>
 #include <sys/lock.h>
@@ -1238,6 +1240,15 @@ userland_sysctl(struct thread *td, int *name, u_int namelen, void *old,
 
 	SYSCTL_LOCK();
 
+#ifdef MAC
+	error = mac_check_system_sysctl(td->td_ucred, name, namelen, old,
+	    oldlenp, inkernel, new, newlen);
+	if (error) {
+		SYSCTL_UNLOCK();
+		return (error);
+	}
+#endif
+
 	do {
 	    req2 = req;
 	    error = sysctl_root(0, name, namelen, &req2);
diff --git a/sys/security/mac/mac_framework.c b/sys/security/mac/mac_framework.c
index 00ecd04..c9ec6a1 100644
--- a/sys/security/mac/mac_framework.c
+++ b/sys/security/mac/mac_framework.c
@@ -151,6 +151,11 @@ SYSCTL_INT(_security_mac, OID_AUTO, enforce_socket, CTLFLAG_RW,
     &mac_enforce_socket, 0, "Enforce MAC policy on socket operations");
 TUNABLE_INT("security.mac.enforce_socket", &mac_enforce_socket);
 
+static int	mac_enforce_sysctl = 1;
+SYSCTL_INT(_security_mac, OID_AUTO, enforce_sysctl, CTLFLAG_RW,
+    &mac_enforce_sysctl, 0, "Enforce MAC policy on sysctl operations");
+TUNABLE_INT("security.mac.enforce_sysctl", &mac_enforce_sysctl);
+
 static int     mac_enforce_vm = 1;
 SYSCTL_INT(_security_mac, OID_AUTO, enforce_vm, CTLFLAG_RW,
     &mac_enforce_vm, 0, "Enforce MAC policy on vm operations");
@@ -912,6 +917,10 @@ mac_policy_register(struct mac_policy_conf *mpc)
 			mpc->mpc_ops->mpo_check_system_swapon =
 			    mpe->mpe_function;
 			break;
+		case MAC_CHECK_SYSTEM_SYSCTL:
+			mpc->mpc_ops->mpo_check_system_sysctl =
+			    mpe->mpe_function;
+			break;
 		case MAC_CHECK_VNODE_ACCESS:
 			mpc->mpc_ops->mpo_check_vnode_access =
 			    mpe->mpe_function;
@@ -3034,6 +3043,25 @@ mac_check_system_swapon(struct ucred *cred, struct vnode *vp)
 }
 
 int
+mac_check_system_sysctl(struct ucred *cred, int *name, u_int namelen,
+    void *old, size_t *oldlenp, int inkernel, void *new, size_t newlen)
+{
+	int error;
+
+	/*
+	 * XXXMAC: We're very much like to assert the SYSCTL_LOCK here,
+	 * but since it's not exported from kern_sysctl.c, we can't.
+	 */
+	if (!mac_enforce_sysctl)
+		return (0);
+
+	MAC_CHECK(check_system_sysctl, cred, name, namelen, old, oldlenp,
+	    inkernel, new, newlen);
+
+	return (error);
+}
+
+int
 mac_ioctl_ifnet_get(struct ucred *cred, struct ifreq *ifr,
     struct ifnet *ifnet)
 {
diff --git a/sys/security/mac/mac_framework.h b/sys/security/mac/mac_framework.h
index e43139d..0e07753 100644
--- a/sys/security/mac/mac_framework.h
+++ b/sys/security/mac/mac_framework.h
@@ -299,6 +299,9 @@ int	mac_check_socket_send(struct ucred *cred, struct socket *so);
 int	mac_check_socket_visible(struct ucred *cred, struct socket *so);
 int	mac_check_system_reboot(struct ucred *cred, int howto);
 int	mac_check_system_swapon(struct ucred *cred, struct vnode *vp);
+int	mac_check_system_sysctl(struct ucred *cred, int *name,
+	    u_int namelen, void *old, size_t *oldlenp, int inkernel,
+	    void *new, size_t newlen);
 int	mac_check_vnode_access(struct ucred *cred, struct vnode *vp,
 	    int flags);
 int	mac_check_vnode_chdir(struct ucred *cred, struct vnode *dvp);
diff --git a/sys/security/mac/mac_internal.h b/sys/security/mac/mac_internal.h
index 00ecd04..c9ec6a1 100644
--- a/sys/security/mac/mac_internal.h
+++ b/sys/security/mac/mac_internal.h
@@ -151,6 +151,11 @@ SYSCTL_INT(_security_mac, OID_AUTO, enforce_socket, CTLFLAG_RW,
     &mac_enforce_socket, 0, "Enforce MAC policy on socket operations");
 TUNABLE_INT("security.mac.enforce_socket", &mac_enforce_socket);
 
+static int	mac_enforce_sysctl = 1;
+SYSCTL_INT(_security_mac, OID_AUTO, enforce_sysctl, CTLFLAG_RW,
+    &mac_enforce_sysctl, 0, "Enforce MAC policy on sysctl operations");
+TUNABLE_INT("security.mac.enforce_sysctl", &mac_enforce_sysctl);
+
 static int     mac_enforce_vm = 1;
 SYSCTL_INT(_security_mac, OID_AUTO, enforce_vm, CTLFLAG_RW,
     &mac_enforce_vm, 0, "Enforce MAC policy on vm operations");
@@ -912,6 +917,10 @@ mac_policy_register(struct mac_policy_conf *mpc)
 			mpc->mpc_ops->mpo_check_system_swapon =
 			    mpe->mpe_function;
 			break;
+		case MAC_CHECK_SYSTEM_SYSCTL:
+			mpc->mpc_ops->mpo_check_system_sysctl =
+			    mpe->mpe_function;
+			break;
 		case MAC_CHECK_VNODE_ACCESS:
 			mpc->mpc_ops->mpo_check_vnode_access =
 			    mpe->mpe_function;
@@ -3034,6 +3043,25 @@ mac_check_system_swapon(struct ucred *cred, struct vnode *vp)
 }
 
 int
+mac_check_system_sysctl(struct ucred *cred, int *name, u_int namelen,
+    void *old, size_t *oldlenp, int inkernel, void *new, size_t newlen)
+{
+	int error;
+
+	/*
+	 * XXXMAC: We're very much like to assert the SYSCTL_LOCK here,
+	 * but since it's not exported from kern_sysctl.c, we can't.
+	 */
+	if (!mac_enforce_sysctl)
+		return (0);
+
+	MAC_CHECK(check_system_sysctl, cred, name, namelen, old, oldlenp,
+	    inkernel, new, newlen);
+
+	return (error);
+}
+
+int
 mac_ioctl_ifnet_get(struct ucred *cred, struct ifreq *ifr,
     struct ifnet *ifnet)
 {
diff --git a/sys/security/mac/mac_net.c b/sys/security/mac/mac_net.c
index 00ecd04..c9ec6a1 100644
--- a/sys/security/mac/mac_net.c
+++ b/sys/security/mac/mac_net.c
@@ -151,6 +151,11 @@ SYSCTL_INT(_security_mac, OID_AUTO, enforce_socket, CTLFLAG_RW,
     &mac_enforce_socket, 0, "Enforce MAC policy on socket operations");
 TUNABLE_INT("security.mac.enforce_socket", &mac_enforce_socket);
 
+static int	mac_enforce_sysctl = 1;
+SYSCTL_INT(_security_mac, OID_AUTO, enforce_sysctl, CTLFLAG_RW,
+    &mac_enforce_sysctl, 0, "Enforce MAC policy on sysctl operations");
+TUNABLE_INT("security.mac.enforce_sysctl", &mac_enforce_sysctl);
+
 static int     mac_enforce_vm = 1;
 SYSCTL_INT(_security_mac, OID_AUTO, enforce_vm, CTLFLAG_RW,
     &mac_enforce_vm, 0, "Enforce MAC policy on vm operations");
@@ -912,6 +917,10 @@ mac_policy_register(struct mac_policy_conf *mpc)
 			mpc->mpc_ops->mpo_check_system_swapon =
 			    mpe->mpe_function;
 			break;
+		case MAC_CHECK_SYSTEM_SYSCTL:
+			mpc->mpc_ops->mpo_check_system_sysctl =
+			    mpe->mpe_function;
+			break;
 		case MAC_CHECK_VNODE_ACCESS:
 			mpc->mpc_ops->mpo_check_vnode_access =
 			    mpe->mpe_function;
@@ -3034,6 +3043,25 @@ mac_check_system_swapon(struct ucred *cred, struct vnode *vp)
 }
 
 int
+mac_check_system_sysctl(struct ucred *cred, int *name, u_int namelen,
+    void *old, size_t *oldlenp, int inkernel, void *new, size_t newlen)
+{
+	int error;
+
+	/*
+	 * XXXMAC: We're very much like to assert the SYSCTL_LOCK here,
+	 * but since it's not exported from kern_sysctl.c, we can't.
+	 */
+	if (!mac_enforce_sysctl)
+		return (0);
+
+	MAC_CHECK(check_system_sysctl, cred, name, namelen, old, oldlenp,
+	    inkernel, new, newlen);
+
+	return (error);
+}
+
+int
 mac_ioctl_ifnet_get(struct ucred *cred, struct ifreq *ifr,
     struct ifnet *ifnet)
 {
diff --git a/sys/security/mac/mac_pipe.c b/sys/security/mac/mac_pipe.c
index 00ecd04..c9ec6a1 100644
--- a/sys/security/mac/mac_pipe.c
+++ b/sys/security/mac/mac_pipe.c
@@ -151,6 +151,11 @@ SYSCTL_INT(_security_mac, OID_AUTO, enforce_socket, CTLFLAG_RW,
     &mac_enforce_socket, 0, "Enforce MAC policy on socket operations");
 TUNABLE_INT("security.mac.enforce_socket", &mac_enforce_socket);
 
+static int	mac_enforce_sysctl = 1;
+SYSCTL_INT(_security_mac, OID_AUTO, enforce_sysctl, CTLFLAG_RW,
+    &mac_enforce_sysctl, 0, "Enforce MAC policy on sysctl operations");
+TUNABLE_INT("security.mac.enforce_sysctl", &mac_enforce_sysctl);
+
 static int     mac_enforce_vm = 1;
 SYSCTL_INT(_security_mac, OID_AUTO, enforce_vm, CTLFLAG_RW,
     &mac_enforce_vm, 0, "Enforce MAC policy on vm operations");
@@ -912,6 +917,10 @@ mac_policy_register(struct mac_policy_conf *mpc)
 			mpc->mpc_ops->mpo_check_system_swapon =
 			    mpe->mpe_function;
 			break;
+		case MAC_CHECK_SYSTEM_SYSCTL:
+			mpc->mpc_ops->mpo_check_system_sysctl =
+			    mpe->mpe_function;
+			break;
 		case MAC_CHECK_VNODE_ACCESS:
 			mpc->mpc_ops->mpo_check_vnode_access =
 			    mpe->mpe_function;
@@ -3034,6 +3043,25 @@ mac_check_system_swapon(struct ucred *cred, struct vnode *vp)
 }
 
 int
+mac_check_system_sysctl(struct ucred *cred, int *name, u_int namelen,
+    void *old, size_t *oldlenp, int inkernel, void *new, size_t newlen)
+{
+	int error;
+
+	/*
+	 * XXXMAC: We're very much like to assert the SYSCTL_LOCK here,
+	 * but since it's not exported from kern_sysctl.c, we can't.
+	 */
+	if (!mac_enforce_sysctl)
+		return (0);
+
+	MAC_CHECK(check_system_sysctl, cred, name, namelen, old, oldlenp,
+	    inkernel, new, newlen);
+
+	return (error);
+}
+
+int
 mac_ioctl_ifnet_get(struct ucred *cred, struct ifreq *ifr,
     struct ifnet *ifnet)
 {
diff --git a/sys/security/mac/mac_policy.h b/sys/security/mac/mac_policy.h
index d92bcf7..6485743 100644
--- a/sys/security/mac/mac_policy.h
+++ b/sys/security/mac/mac_policy.h
@@ -313,6 +313,9 @@ struct mac_policy_ops {
 	int	(*mpo_check_system_reboot)(struct ucred *cred, int howto);
 	int	(*mpo_check_system_swapon)(struct ucred *cred,
 		    struct vnode *vp, struct label *label);
+	int	(*mpo_check_system_sysctl)(struct ucred *cred, int *name,
+		    u_int namelen, void *old, size_t *oldlenp, int inkernel,
+		    void *new, size_t newlen);
 	int	(*mpo_check_vnode_access)(struct ucred *cred,
 		    struct vnode *vp, struct label *label, int flags);
 	int	(*mpo_check_vnode_chdir)(struct ucred *cred,
@@ -505,6 +508,7 @@ enum mac_op_constant {
 	MAC_CHECK_SOCKET_VISIBLE,
 	MAC_CHECK_SYSTEM_REBOOT,
 	MAC_CHECK_SYSTEM_SWAPON,
+	MAC_CHECK_SYSTEM_SYSCTL,
 	MAC_CHECK_VNODE_ACCESS,
 	MAC_CHECK_VNODE_CHDIR,
 	MAC_CHECK_VNODE_CHROOT,
diff --git a/sys/security/mac/mac_process.c b/sys/security/mac/mac_process.c
index 00ecd04..c9ec6a1 100644
--- a/sys/security/mac/mac_process.c
+++ b/sys/security/mac/mac_process.c
@@ -151,6 +151,11 @@ SYSCTL_INT(_security_mac, OID_AUTO, enforce_socket, CTLFLAG_RW,
     &mac_enforce_socket, 0, "Enforce MAC policy on socket operations");
 TUNABLE_INT("security.mac.enforce_socket", &mac_enforce_socket);
 
+static int	mac_enforce_sysctl = 1;
+SYSCTL_INT(_security_mac, OID_AUTO, enforce_sysctl, CTLFLAG_RW,
+    &mac_enforce_sysctl, 0, "Enforce MAC policy on sysctl operations");
+TUNABLE_INT("security.mac.enforce_sysctl", &mac_enforce_sysctl);
+
 static int     mac_enforce_vm = 1;
 SYSCTL_INT(_security_mac, OID_AUTO, enforce_vm, CTLFLAG_RW,
     &mac_enforce_vm, 0, "Enforce MAC policy on vm operations");
@@ -912,6 +917,10 @@ mac_policy_register(struct mac_policy_conf *mpc)
 			mpc->mpc_ops->mpo_check_system_swapon =
 			    mpe->mpe_function;
 			break;
+		case MAC_CHECK_SYSTEM_SYSCTL:
+			mpc->mpc_ops->mpo_check_system_sysctl =
+			    mpe->mpe_function;
+			break;
 		case MAC_CHECK_VNODE_ACCESS:
 			mpc->mpc_ops->mpo_check_vnode_access =
 			    mpe->mpe_function;
@@ -3034,6 +3043,25 @@ mac_check_system_swapon(struct ucred *cred, struct vnode *vp)
 }
 
 int
+mac_check_system_sysctl(struct ucred *cred, int *name, u_int namelen,
+    void *old, size_t *oldlenp, int inkernel, void *new, size_t newlen)
+{
+	int error;
+
+	/*
+	 * XXXMAC: We're very much like to assert the SYSCTL_LOCK here,
+	 * but since it's not exported from kern_sysctl.c, we can't.
+	 */
+	if (!mac_enforce_sysctl)
+		return (0);
+
+	MAC_CHECK(check_system_sysctl, cred, name, namelen, old, oldlenp,
+	    inkernel, new, newlen);
+
+	return (error);
+}
+
+int
 mac_ioctl_ifnet_get(struct ucred *cred, struct ifreq *ifr,
     struct ifnet *ifnet)
 {
diff --git a/sys/security/mac/mac_syscalls.c b/sys/security/mac/mac_syscalls.c
index 00ecd04..c9ec6a1 100644
--- a/sys/security/mac/mac_syscalls.c
+++ b/sys/security/mac/mac_syscalls.c
@@ -151,6 +151,11 @@ SYSCTL_INT(_security_mac, OID_AUTO, enforce_socket, CTLFLAG_RW,
     &mac_enforce_socket, 0, "Enforce MAC policy on socket operations");
 TUNABLE_INT("security.mac.enforce_socket", &mac_enforce_socket);
 
+static int	mac_enforce_sysctl = 1;
+SYSCTL_INT(_security_mac, OID_AUTO, enforce_sysctl, CTLFLAG_RW,
+    &mac_enforce_sysctl, 0, "Enforce MAC policy on sysctl operations");
+TUNABLE_INT("security.mac.enforce_sysctl", &mac_enforce_sysctl);
+
 static int     mac_enforce_vm = 1;
 SYSCTL_INT(_security_mac, OID_AUTO, enforce_vm, CTLFLAG_RW,
     &mac_enforce_vm, 0, "Enforce MAC policy on vm operations");
@@ -912,6 +917,10 @@ mac_policy_register(struct mac_policy_conf *mpc)
 			mpc->mpc_ops->mpo_check_system_swapon =
 			    mpe->mpe_function;
 			break;
+		case MAC_CHECK_SYSTEM_SYSCTL:
+			mpc->mpc_ops->mpo_check_system_sysctl =
+			    mpe->mpe_function;
+			break;
 		case MAC_CHECK_VNODE_ACCESS:
 			mpc->mpc_ops->mpo_check_vnode_access =
 			    mpe->mpe_function;
@@ -3034,6 +3043,25 @@ mac_check_system_swapon(struct ucred *cred, struct vnode *vp)
 }
 
 int
+mac_check_system_sysctl(struct ucred *cred, int *name, u_int namelen,
+    void *old, size_t *oldlenp, int inkernel, void *new, size_t newlen)
+{
+	int error;
+
+	/*
+	 * XXXMAC: We're very much like to assert the SYSCTL_LOCK here,
+	 * but since it's not exported from kern_sysctl.c, we can't.
+	 */
+	if (!mac_enforce_sysctl)
+		return (0);
+
+	MAC_CHECK(check_system_sysctl, cred, name, namelen, old, oldlenp,
+	    inkernel, new, newlen);
+
+	return (error);
+}
+
+int
 mac_ioctl_ifnet_get(struct ucred *cred, struct ifreq *ifr,
     struct ifnet *ifnet)
 {
diff --git a/sys/security/mac/mac_system.c b/sys/security/mac/mac_system.c
index 00ecd04..c9ec6a1 100644
--- a/sys/security/mac/mac_system.c
+++ b/sys/security/mac/mac_system.c
@@ -151,6 +151,11 @@ SYSCTL_INT(_security_mac, OID_AUTO, enforce_socket, CTLFLAG_RW,
     &mac_enforce_socket, 0, "Enforce MAC policy on socket operations");
 TUNABLE_INT("security.mac.enforce_socket", &mac_enforce_socket);
 
+static int	mac_enforce_sysctl = 1;
+SYSCTL_INT(_security_mac, OID_AUTO, enforce_sysctl, CTLFLAG_RW,
+    &mac_enforce_sysctl, 0, "Enforce MAC policy on sysctl operations");
+TUNABLE_INT("security.mac.enforce_sysctl", &mac_enforce_sysctl);
+
 static int     mac_enforce_vm = 1;
 SYSCTL_INT(_security_mac, OID_AUTO, enforce_vm, CTLFLAG_RW,
     &mac_enforce_vm, 0, "Enforce MAC policy on vm operations");
@@ -912,6 +917,10 @@ mac_policy_register(struct mac_policy_conf *mpc)
 			mpc->mpc_ops->mpo_check_system_swapon =
 			    mpe->mpe_function;
 			break;
+		case MAC_CHECK_SYSTEM_SYSCTL:
+			mpc->mpc_ops->mpo_check_system_sysctl =
+			    mpe->mpe_function;
+			break;
 		case MAC_CHECK_VNODE_ACCESS:
 			mpc->mpc_ops->mpo_check_vnode_access =
 			    mpe->mpe_function;
@@ -3034,6 +3043,25 @@ mac_check_system_swapon(struct ucred *cred, struct vnode *vp)
 }
 
 int
+mac_check_system_sysctl(struct ucred *cred, int *name, u_int namelen,
+    void *old, size_t *oldlenp, int inkernel, void *new, size_t newlen)
+{
+	int error;
+
+	/*
+	 * XXXMAC: We're very much like to assert the SYSCTL_LOCK here,
+	 * but since it's not exported from kern_sysctl.c, we can't.
+	 */
+	if (!mac_enforce_sysctl)
+		return (0);
+
+	MAC_CHECK(check_system_sysctl, cred, name, namelen, old, oldlenp,
+	    inkernel, new, newlen);
+
+	return (error);
+}
+
+int
 mac_ioctl_ifnet_get(struct ucred *cred, struct ifreq *ifr,
     struct ifnet *ifnet)
 {
diff --git a/sys/security/mac/mac_vfs.c b/sys/security/mac/mac_vfs.c
index 00ecd04..c9ec6a1 100644
--- a/sys/security/mac/mac_vfs.c
+++ b/sys/security/mac/mac_vfs.c
@@ -151,6 +151,11 @@ SYSCTL_INT(_security_mac, OID_AUTO, enforce_socket, CTLFLAG_RW,
     &mac_enforce_socket, 0, "Enforce MAC policy on socket operations");
 TUNABLE_INT("security.mac.enforce_socket", &mac_enforce_socket);
 
+static int	mac_enforce_sysctl = 1;
+SYSCTL_INT(_security_mac, OID_AUTO, enforce_sysctl, CTLFLAG_RW,
+    &mac_enforce_sysctl, 0, "Enforce MAC policy on sysctl operations");
+TUNABLE_INT("security.mac.enforce_sysctl", &mac_enforce_sysctl);
+
 static int     mac_enforce_vm = 1;
 SYSCTL_INT(_security_mac, OID_AUTO, enforce_vm, CTLFLAG_RW,
     &mac_enforce_vm, 0, "Enforce MAC policy on vm operations");
@@ -912,6 +917,10 @@ mac_policy_register(struct mac_policy_conf *mpc)
 			mpc->mpc_ops->mpo_check_system_swapon =
 			    mpe->mpe_function;
 			break;
+		case MAC_CHECK_SYSTEM_SYSCTL:
+			mpc->mpc_ops->mpo_check_system_sysctl =
+			    mpe->mpe_function;
+			break;
 		case MAC_CHECK_VNODE_ACCESS:
 			mpc->mpc_ops->mpo_check_vnode_access =
 			    mpe->mpe_function;
@@ -3034,6 +3043,25 @@ mac_check_system_swapon(struct ucred *cred, struct vnode *vp)
 }
 
 int
+mac_check_system_sysctl(struct ucred *cred, int *name, u_int namelen,
+    void *old, size_t *oldlenp, int inkernel, void *new, size_t newlen)
+{
+	int error;
+
+	/*
+	 * XXXMAC: We're very much like to assert the SYSCTL_LOCK here,
+	 * but since it's not exported from kern_sysctl.c, we can't.
+	 */
+	if (!mac_enforce_sysctl)
+		return (0);
+
+	MAC_CHECK(check_system_sysctl, cred, name, namelen, old, oldlenp,
+	    inkernel, new, newlen);
+
+	return (error);
+}
+
+int
 mac_ioctl_ifnet_get(struct ucred *cred, struct ifreq *ifr,
     struct ifnet *ifnet)
 {
diff --git a/sys/sys/mac.h b/sys/sys/mac.h
index e43139d..0e07753 100644
--- a/sys/sys/mac.h
+++ b/sys/sys/mac.h
@@ -299,6 +299,9 @@ int	mac_check_socket_send(struct ucred *cred, struct socket *so);
 int	mac_check_socket_visible(struct ucred *cred, struct socket *so);
 int	mac_check_system_reboot(struct ucred *cred, int howto);
 int	mac_check_system_swapon(struct ucred *cred, struct vnode *vp);
+int	mac_check_system_sysctl(struct ucred *cred, int *name,
+	    u_int namelen, void *old, size_t *oldlenp, int inkernel,
+	    void *new, size_t newlen);
 int	mac_check_vnode_access(struct ucred *cred, struct vnode *vp,
 	    int flags);
 int	mac_check_vnode_chdir(struct ucred *cred, struct vnode *dvp);
diff --git a/sys/sys/mac_policy.h b/sys/sys/mac_policy.h
index d92bcf7..6485743 100644
--- a/sys/sys/mac_policy.h
+++ b/sys/sys/mac_policy.h
@@ -313,6 +313,9 @@ struct mac_policy_ops {
 	int	(*mpo_check_system_reboot)(struct ucred *cred, int howto);
 	int	(*mpo_check_system_swapon)(struct ucred *cred,
 		    struct vnode *vp, struct label *label);
+	int	(*mpo_check_system_sysctl)(struct ucred *cred, int *name,
+		    u_int namelen, void *old, size_t *oldlenp, int inkernel,
+		    void *new, size_t newlen);
 	int	(*mpo_check_vnode_access)(struct ucred *cred,
 		    struct vnode *vp, struct label *label, int flags);
 	int	(*mpo_check_vnode_chdir)(struct ucred *cred,
@@ -505,6 +508,7 @@ enum mac_op_constant {
 	MAC_CHECK_SOCKET_VISIBLE,
 	MAC_CHECK_SYSTEM_REBOOT,
 	MAC_CHECK_SYSTEM_SWAPON,
+	MAC_CHECK_SYSTEM_SYSCTL,
 	MAC_CHECK_VNODE_ACCESS,
 	MAC_CHECK_VNODE_CHDIR,
 	MAC_CHECK_VNODE_CHROOT,