Merge support for mac_check_vnode_link(), a MAC framework/policy entry

point that instruments the creation of hard links.  Policy implementations
to follow.

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

15 files changed, 294 insertions, 2 deletions

diff --git a/sys/kern/kern_mac.c b/sys/kern/kern_mac.c
index d21d5df..5719b01f 100644
--- a/sys/kern/kern_mac.c
+++ b/sys/kern/kern_mac.c
@@ -799,6 +799,10 @@ mac_policy_register(struct mac_policy_conf *mpc)
 			mpc->mpc_ops->mpo_check_vnode_getextattr =
 			    mpe->mpe_function;
 			break;
+		case MAC_CHECK_VNODE_LINK:
+			mpc->mpc_ops->mpo_check_vnode_link =
+			    mpe->mpe_function;
+			break;
 		case MAC_CHECK_VNODE_LOOKUP:
 			mpc->mpc_ops->mpo_check_vnode_lookup =
 			    mpe->mpe_function;
@@ -1832,6 +1836,32 @@ mac_check_vnode_getextattr(struct ucred *cred, struct vnode *vp,
 }
 
 int
+mac_check_vnode_link(struct ucred *cred, struct vnode *dvp,
+    struct vnode *vp, struct componentname *cnp)
+{
+
+	int error;
+
+	ASSERT_VOP_LOCKED(dvp, "mac_check_vnode_link");
+	ASSERT_VOP_LOCKED(vp, "mac_check_vnode_link");
+
+	if (!mac_enforce_fs)
+		return (0);
+
+	error = vn_refreshlabel(dvp, cred);
+	if (error)
+		return (error);
+
+	error = vn_refreshlabel(vp, cred);
+	if (error)
+		return (error);
+
+	MAC_CHECK(check_vnode_link, cred, dvp, &dvp->v_label, vp,
+	    &vp->v_label, cnp);
+	return (error);
+}
+
+int
 mac_check_vnode_lookup(struct ucred *cred, struct vnode *dvp,
     struct componentname *cnp)
 {
diff --git a/sys/kern/vfs_extattr.c b/sys/kern/vfs_extattr.c
index 7c72a8c..4cba8b5 100644
--- a/sys/kern/vfs_extattr.c
+++ b/sys/kern/vfs_extattr.c
@@ -1031,7 +1031,12 @@ kern_link(struct thread *td, char *path, char *link, enum uio_seg segflg)
 		    == 0) {
 			VOP_LEASE(nd.ni_dvp, td, td->td_ucred, LEASE_WRITE);
 			VOP_LEASE(vp, td, td->td_ucred, LEASE_WRITE);
-			error = VOP_LINK(nd.ni_dvp, vp, &nd.ni_cnd);
+#ifdef MAC
+			error = mac_check_vnode_link(td->td_ucred, nd.ni_dvp,
+			    vp, &nd.ni_cnd);
+			if (error == 0)
+#endif
+				error = VOP_LINK(nd.ni_dvp, vp, &nd.ni_cnd);
 			VOP_UNLOCK(vp, 0, td);
 		}
 		NDFREE(&nd, NDF_ONLY_PNBUF);
diff --git a/sys/kern/vfs_syscalls.c b/sys/kern/vfs_syscalls.c
index 7c72a8c..4cba8b5 100644
--- a/sys/kern/vfs_syscalls.c
+++ b/sys/kern/vfs_syscalls.c
@@ -1031,7 +1031,12 @@ kern_link(struct thread *td, char *path, char *link, enum uio_seg segflg)
 		    == 0) {
 			VOP_LEASE(nd.ni_dvp, td, td->td_ucred, LEASE_WRITE);
 			VOP_LEASE(vp, td, td->td_ucred, LEASE_WRITE);
-			error = VOP_LINK(nd.ni_dvp, vp, &nd.ni_cnd);
+#ifdef MAC
+			error = mac_check_vnode_link(td->td_ucred, nd.ni_dvp,
+			    vp, &nd.ni_cnd);
+			if (error == 0)
+#endif
+				error = VOP_LINK(nd.ni_dvp, vp, &nd.ni_cnd);
 			VOP_UNLOCK(vp, 0, td);
 		}
 		NDFREE(&nd, NDF_ONLY_PNBUF);
diff --git a/sys/security/mac/mac_framework.c b/sys/security/mac/mac_framework.c
index d21d5df..5719b01f 100644
--- a/sys/security/mac/mac_framework.c
+++ b/sys/security/mac/mac_framework.c
@@ -799,6 +799,10 @@ mac_policy_register(struct mac_policy_conf *mpc)
 			mpc->mpc_ops->mpo_check_vnode_getextattr =
 			    mpe->mpe_function;
 			break;
+		case MAC_CHECK_VNODE_LINK:
+			mpc->mpc_ops->mpo_check_vnode_link =
+			    mpe->mpe_function;
+			break;
 		case MAC_CHECK_VNODE_LOOKUP:
 			mpc->mpc_ops->mpo_check_vnode_lookup =
 			    mpe->mpe_function;
@@ -1832,6 +1836,32 @@ mac_check_vnode_getextattr(struct ucred *cred, struct vnode *vp,
 }
 
 int
+mac_check_vnode_link(struct ucred *cred, struct vnode *dvp,
+    struct vnode *vp, struct componentname *cnp)
+{
+
+	int error;
+
+	ASSERT_VOP_LOCKED(dvp, "mac_check_vnode_link");
+	ASSERT_VOP_LOCKED(vp, "mac_check_vnode_link");
+
+	if (!mac_enforce_fs)
+		return (0);
+
+	error = vn_refreshlabel(dvp, cred);
+	if (error)
+		return (error);
+
+	error = vn_refreshlabel(vp, cred);
+	if (error)
+		return (error);
+
+	MAC_CHECK(check_vnode_link, cred, dvp, &dvp->v_label, vp,
+	    &vp->v_label, cnp);
+	return (error);
+}
+
+int
 mac_check_vnode_lookup(struct ucred *cred, struct vnode *dvp,
     struct componentname *cnp)
 {
diff --git a/sys/security/mac/mac_framework.h b/sys/security/mac/mac_framework.h
index ebb65cb..a646ad3 100644
--- a/sys/security/mac/mac_framework.h
+++ b/sys/security/mac/mac_framework.h
@@ -333,6 +333,8 @@ int	mac_check_vnode_getacl(struct ucred *cred, struct vnode *vp,
 	    acl_type_t type);
 int	mac_check_vnode_getextattr(struct ucred *cred, struct vnode *vp,
 	    int attrnamespace, const char *name, struct uio *uio);
+int	mac_check_vnode_link(struct ucred *cred, struct vnode *dvp,
+	    struct vnode *vp, struct componentname *cnp);
 int	mac_check_vnode_lookup(struct ucred *cred, struct vnode *dvp,
  	    struct componentname *cnp);
 /* XXX This u_char should be vm_prot_t! */
diff --git a/sys/security/mac/mac_internal.h b/sys/security/mac/mac_internal.h
index d21d5df..5719b01f 100644
--- a/sys/security/mac/mac_internal.h
+++ b/sys/security/mac/mac_internal.h
@@ -799,6 +799,10 @@ mac_policy_register(struct mac_policy_conf *mpc)
 			mpc->mpc_ops->mpo_check_vnode_getextattr =
 			    mpe->mpe_function;
 			break;
+		case MAC_CHECK_VNODE_LINK:
+			mpc->mpc_ops->mpo_check_vnode_link =
+			    mpe->mpe_function;
+			break;
 		case MAC_CHECK_VNODE_LOOKUP:
 			mpc->mpc_ops->mpo_check_vnode_lookup =
 			    mpe->mpe_function;
@@ -1832,6 +1836,32 @@ mac_check_vnode_getextattr(struct ucred *cred, struct vnode *vp,
 }
 
 int
+mac_check_vnode_link(struct ucred *cred, struct vnode *dvp,
+    struct vnode *vp, struct componentname *cnp)
+{
+
+	int error;
+
+	ASSERT_VOP_LOCKED(dvp, "mac_check_vnode_link");
+	ASSERT_VOP_LOCKED(vp, "mac_check_vnode_link");
+
+	if (!mac_enforce_fs)
+		return (0);
+
+	error = vn_refreshlabel(dvp, cred);
+	if (error)
+		return (error);
+
+	error = vn_refreshlabel(vp, cred);
+	if (error)
+		return (error);
+
+	MAC_CHECK(check_vnode_link, cred, dvp, &dvp->v_label, vp,
+	    &vp->v_label, cnp);
+	return (error);
+}
+
+int
 mac_check_vnode_lookup(struct ucred *cred, struct vnode *dvp,
     struct componentname *cnp)
 {
diff --git a/sys/security/mac/mac_net.c b/sys/security/mac/mac_net.c
index d21d5df..5719b01f 100644
--- a/sys/security/mac/mac_net.c
+++ b/sys/security/mac/mac_net.c
@@ -799,6 +799,10 @@ mac_policy_register(struct mac_policy_conf *mpc)
 			mpc->mpc_ops->mpo_check_vnode_getextattr =
 			    mpe->mpe_function;
 			break;
+		case MAC_CHECK_VNODE_LINK:
+			mpc->mpc_ops->mpo_check_vnode_link =
+			    mpe->mpe_function;
+			break;
 		case MAC_CHECK_VNODE_LOOKUP:
 			mpc->mpc_ops->mpo_check_vnode_lookup =
 			    mpe->mpe_function;
@@ -1832,6 +1836,32 @@ mac_check_vnode_getextattr(struct ucred *cred, struct vnode *vp,
 }
 
 int
+mac_check_vnode_link(struct ucred *cred, struct vnode *dvp,
+    struct vnode *vp, struct componentname *cnp)
+{
+
+	int error;
+
+	ASSERT_VOP_LOCKED(dvp, "mac_check_vnode_link");
+	ASSERT_VOP_LOCKED(vp, "mac_check_vnode_link");
+
+	if (!mac_enforce_fs)
+		return (0);
+
+	error = vn_refreshlabel(dvp, cred);
+	if (error)
+		return (error);
+
+	error = vn_refreshlabel(vp, cred);
+	if (error)
+		return (error);
+
+	MAC_CHECK(check_vnode_link, cred, dvp, &dvp->v_label, vp,
+	    &vp->v_label, cnp);
+	return (error);
+}
+
+int
 mac_check_vnode_lookup(struct ucred *cred, struct vnode *dvp,
     struct componentname *cnp)
 {
diff --git a/sys/security/mac/mac_pipe.c b/sys/security/mac/mac_pipe.c
index d21d5df..5719b01f 100644
--- a/sys/security/mac/mac_pipe.c
+++ b/sys/security/mac/mac_pipe.c
@@ -799,6 +799,10 @@ mac_policy_register(struct mac_policy_conf *mpc)
 			mpc->mpc_ops->mpo_check_vnode_getextattr =
 			    mpe->mpe_function;
 			break;
+		case MAC_CHECK_VNODE_LINK:
+			mpc->mpc_ops->mpo_check_vnode_link =
+			    mpe->mpe_function;
+			break;
 		case MAC_CHECK_VNODE_LOOKUP:
 			mpc->mpc_ops->mpo_check_vnode_lookup =
 			    mpe->mpe_function;
@@ -1832,6 +1836,32 @@ mac_check_vnode_getextattr(struct ucred *cred, struct vnode *vp,
 }
 
 int
+mac_check_vnode_link(struct ucred *cred, struct vnode *dvp,
+    struct vnode *vp, struct componentname *cnp)
+{
+
+	int error;
+
+	ASSERT_VOP_LOCKED(dvp, "mac_check_vnode_link");
+	ASSERT_VOP_LOCKED(vp, "mac_check_vnode_link");
+
+	if (!mac_enforce_fs)
+		return (0);
+
+	error = vn_refreshlabel(dvp, cred);
+	if (error)
+		return (error);
+
+	error = vn_refreshlabel(vp, cred);
+	if (error)
+		return (error);
+
+	MAC_CHECK(check_vnode_link, cred, dvp, &dvp->v_label, vp,
+	    &vp->v_label, cnp);
+	return (error);
+}
+
+int
 mac_check_vnode_lookup(struct ucred *cred, struct vnode *dvp,
     struct componentname *cnp)
 {
diff --git a/sys/security/mac/mac_policy.h b/sys/security/mac/mac_policy.h
index a54e925..d9f1a8e 100644
--- a/sys/security/mac/mac_policy.h
+++ b/sys/security/mac/mac_policy.h
@@ -294,6 +294,9 @@ struct mac_policy_ops {
 	int	(*mpo_check_vnode_getextattr)(struct ucred *cred,
 		    struct vnode *vp, struct label *label, int attrnamespace,
 		    const char *name, struct uio *uio);
+	int	(*mpo_check_vnode_link)(struct ucred *cred, struct vnode *dvp,
+		    struct label *dlabel, struct vnode *vp,
+		    struct label *label, struct componentname *cnp);
 	int	(*mpo_check_vnode_lookup)(struct ucred *cred,
 		    struct vnode *dvp, struct label *dlabel,
 		    struct componentname *cnp);
@@ -454,6 +457,7 @@ enum mac_op_constant {
 	MAC_CHECK_VNODE_EXEC,
 	MAC_CHECK_VNODE_GETACL,
 	MAC_CHECK_VNODE_GETEXTATTR,
+	MAC_CHECK_VNODE_LINK,
 	MAC_CHECK_VNODE_LOOKUP,
 	MAC_CHECK_VNODE_MMAP_PERMS,
 	MAC_CHECK_VNODE_OPEN,
diff --git a/sys/security/mac/mac_process.c b/sys/security/mac/mac_process.c
index d21d5df..5719b01f 100644
--- a/sys/security/mac/mac_process.c
+++ b/sys/security/mac/mac_process.c
@@ -799,6 +799,10 @@ mac_policy_register(struct mac_policy_conf *mpc)
 			mpc->mpc_ops->mpo_check_vnode_getextattr =
 			    mpe->mpe_function;
 			break;
+		case MAC_CHECK_VNODE_LINK:
+			mpc->mpc_ops->mpo_check_vnode_link =
+			    mpe->mpe_function;
+			break;
 		case MAC_CHECK_VNODE_LOOKUP:
 			mpc->mpc_ops->mpo_check_vnode_lookup =
 			    mpe->mpe_function;
@@ -1832,6 +1836,32 @@ mac_check_vnode_getextattr(struct ucred *cred, struct vnode *vp,
 }
 
 int
+mac_check_vnode_link(struct ucred *cred, struct vnode *dvp,
+    struct vnode *vp, struct componentname *cnp)
+{
+
+	int error;
+
+	ASSERT_VOP_LOCKED(dvp, "mac_check_vnode_link");
+	ASSERT_VOP_LOCKED(vp, "mac_check_vnode_link");
+
+	if (!mac_enforce_fs)
+		return (0);
+
+	error = vn_refreshlabel(dvp, cred);
+	if (error)
+		return (error);
+
+	error = vn_refreshlabel(vp, cred);
+	if (error)
+		return (error);
+
+	MAC_CHECK(check_vnode_link, cred, dvp, &dvp->v_label, vp,
+	    &vp->v_label, cnp);
+	return (error);
+}
+
+int
 mac_check_vnode_lookup(struct ucred *cred, struct vnode *dvp,
     struct componentname *cnp)
 {
diff --git a/sys/security/mac/mac_syscalls.c b/sys/security/mac/mac_syscalls.c
index d21d5df..5719b01f 100644
--- a/sys/security/mac/mac_syscalls.c
+++ b/sys/security/mac/mac_syscalls.c
@@ -799,6 +799,10 @@ mac_policy_register(struct mac_policy_conf *mpc)
 			mpc->mpc_ops->mpo_check_vnode_getextattr =
 			    mpe->mpe_function;
 			break;
+		case MAC_CHECK_VNODE_LINK:
+			mpc->mpc_ops->mpo_check_vnode_link =
+			    mpe->mpe_function;
+			break;
 		case MAC_CHECK_VNODE_LOOKUP:
 			mpc->mpc_ops->mpo_check_vnode_lookup =
 			    mpe->mpe_function;
@@ -1832,6 +1836,32 @@ mac_check_vnode_getextattr(struct ucred *cred, struct vnode *vp,
 }
 
 int
+mac_check_vnode_link(struct ucred *cred, struct vnode *dvp,
+    struct vnode *vp, struct componentname *cnp)
+{
+
+	int error;
+
+	ASSERT_VOP_LOCKED(dvp, "mac_check_vnode_link");
+	ASSERT_VOP_LOCKED(vp, "mac_check_vnode_link");
+
+	if (!mac_enforce_fs)
+		return (0);
+
+	error = vn_refreshlabel(dvp, cred);
+	if (error)
+		return (error);
+
+	error = vn_refreshlabel(vp, cred);
+	if (error)
+		return (error);
+
+	MAC_CHECK(check_vnode_link, cred, dvp, &dvp->v_label, vp,
+	    &vp->v_label, cnp);
+	return (error);
+}
+
+int
 mac_check_vnode_lookup(struct ucred *cred, struct vnode *dvp,
     struct componentname *cnp)
 {
diff --git a/sys/security/mac/mac_system.c b/sys/security/mac/mac_system.c
index d21d5df..5719b01f 100644
--- a/sys/security/mac/mac_system.c
+++ b/sys/security/mac/mac_system.c
@@ -799,6 +799,10 @@ mac_policy_register(struct mac_policy_conf *mpc)
 			mpc->mpc_ops->mpo_check_vnode_getextattr =
 			    mpe->mpe_function;
 			break;
+		case MAC_CHECK_VNODE_LINK:
+			mpc->mpc_ops->mpo_check_vnode_link =
+			    mpe->mpe_function;
+			break;
 		case MAC_CHECK_VNODE_LOOKUP:
 			mpc->mpc_ops->mpo_check_vnode_lookup =
 			    mpe->mpe_function;
@@ -1832,6 +1836,32 @@ mac_check_vnode_getextattr(struct ucred *cred, struct vnode *vp,
 }
 
 int
+mac_check_vnode_link(struct ucred *cred, struct vnode *dvp,
+    struct vnode *vp, struct componentname *cnp)
+{
+
+	int error;
+
+	ASSERT_VOP_LOCKED(dvp, "mac_check_vnode_link");
+	ASSERT_VOP_LOCKED(vp, "mac_check_vnode_link");
+
+	if (!mac_enforce_fs)
+		return (0);
+
+	error = vn_refreshlabel(dvp, cred);
+	if (error)
+		return (error);
+
+	error = vn_refreshlabel(vp, cred);
+	if (error)
+		return (error);
+
+	MAC_CHECK(check_vnode_link, cred, dvp, &dvp->v_label, vp,
+	    &vp->v_label, cnp);
+	return (error);
+}
+
+int
 mac_check_vnode_lookup(struct ucred *cred, struct vnode *dvp,
     struct componentname *cnp)
 {
diff --git a/sys/security/mac/mac_vfs.c b/sys/security/mac/mac_vfs.c
index d21d5df..5719b01f 100644
--- a/sys/security/mac/mac_vfs.c
+++ b/sys/security/mac/mac_vfs.c
@@ -799,6 +799,10 @@ mac_policy_register(struct mac_policy_conf *mpc)
 			mpc->mpc_ops->mpo_check_vnode_getextattr =
 			    mpe->mpe_function;
 			break;
+		case MAC_CHECK_VNODE_LINK:
+			mpc->mpc_ops->mpo_check_vnode_link =
+			    mpe->mpe_function;
+			break;
 		case MAC_CHECK_VNODE_LOOKUP:
 			mpc->mpc_ops->mpo_check_vnode_lookup =
 			    mpe->mpe_function;
@@ -1832,6 +1836,32 @@ mac_check_vnode_getextattr(struct ucred *cred, struct vnode *vp,
 }
 
 int
+mac_check_vnode_link(struct ucred *cred, struct vnode *dvp,
+    struct vnode *vp, struct componentname *cnp)
+{
+
+	int error;
+
+	ASSERT_VOP_LOCKED(dvp, "mac_check_vnode_link");
+	ASSERT_VOP_LOCKED(vp, "mac_check_vnode_link");
+
+	if (!mac_enforce_fs)
+		return (0);
+
+	error = vn_refreshlabel(dvp, cred);
+	if (error)
+		return (error);
+
+	error = vn_refreshlabel(vp, cred);
+	if (error)
+		return (error);
+
+	MAC_CHECK(check_vnode_link, cred, dvp, &dvp->v_label, vp,
+	    &vp->v_label, cnp);
+	return (error);
+}
+
+int
 mac_check_vnode_lookup(struct ucred *cred, struct vnode *dvp,
     struct componentname *cnp)
 {
diff --git a/sys/sys/mac.h b/sys/sys/mac.h
index ebb65cb..a646ad3 100644
--- a/sys/sys/mac.h
+++ b/sys/sys/mac.h
@@ -333,6 +333,8 @@ int	mac_check_vnode_getacl(struct ucred *cred, struct vnode *vp,
 	    acl_type_t type);
 int	mac_check_vnode_getextattr(struct ucred *cred, struct vnode *vp,
 	    int attrnamespace, const char *name, struct uio *uio);
+int	mac_check_vnode_link(struct ucred *cred, struct vnode *dvp,
+	    struct vnode *vp, struct componentname *cnp);
 int	mac_check_vnode_lookup(struct ucred *cred, struct vnode *dvp,
  	    struct componentname *cnp);
 /* XXX This u_char should be vm_prot_t! */
diff --git a/sys/sys/mac_policy.h b/sys/sys/mac_policy.h
index a54e925..d9f1a8e 100644
--- a/sys/sys/mac_policy.h
+++ b/sys/sys/mac_policy.h
@@ -294,6 +294,9 @@ struct mac_policy_ops {
 	int	(*mpo_check_vnode_getextattr)(struct ucred *cred,
 		    struct vnode *vp, struct label *label, int attrnamespace,
 		    const char *name, struct uio *uio);
+	int	(*mpo_check_vnode_link)(struct ucred *cred, struct vnode *dvp,
+		    struct label *dlabel, struct vnode *vp,
+		    struct label *label, struct componentname *cnp);
 	int	(*mpo_check_vnode_lookup)(struct ucred *cred,
 		    struct vnode *dvp, struct label *dlabel,
 		    struct componentname *cnp);
@@ -454,6 +457,7 @@ enum mac_op_constant {
 	MAC_CHECK_VNODE_EXEC,
 	MAC_CHECK_VNODE_GETACL,
 	MAC_CHECK_VNODE_GETEXTATTR,
+	MAC_CHECK_VNODE_LINK,
 	MAC_CHECK_VNODE_LOOKUP,
 	MAC_CHECK_VNODE_MMAP_PERMS,
 	MAC_CHECK_VNODE_OPEN,