security/mac/mac_cred.c

/*-
 * Copyright (c) 1999-2002 Robert N. M. Watson
 * Copyright (c) 2001 Ilmar S. Habibulin
 * Copyright (c) 2001-2003 Networks Associates Technology, Inc.
 * All rights reserved.
 *
 * This software was developed by Robert Watson and Ilmar Habibulin for the
 * TrustedBSD Project.
 *
 * This software was developed for the FreeBSD Project in part by Network
 * Associates Laboratories, the Security Research Division of Network
 * Associates, Inc. under DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"),
 * as part of the DARPA CHATS research program.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/cdefs.h>
__FBSDID("$FreeBSD: head/sys/security/mac/mac_process.c 126097 2004-02-22 00:33:12Z rwatson $");

#include "opt_mac.h"

#include <sys/param.h>
#include <sys/condvar.h>
#include <sys/imgact.h>
#include <sys/kernel.h>
#include <sys/lock.h>
#include <sys/malloc.h>
#include <sys/mutex.h>
#include <sys/mac.h>
#include <sys/proc.h>
#include <sys/sbuf.h>
#include <sys/systm.h>
#include <sys/vnode.h>
#include <sys/mount.h>
#include <sys/file.h>
#include <sys/namei.h>
#include <sys/sysctl.h>

#include <vm/vm.h>
#include <vm/pmap.h>
#include <vm/vm_map.h>
#include <vm/vm_object.h>

#include <sys/mac_policy.h>

#include <security/mac/mac_internal.h>

int	mac_enforce_process = 1;
SYSCTL_INT(_security_mac, OID_AUTO, enforce_process, CTLFLAG_RW,
    &mac_enforce_process, 0, "Enforce MAC policy on inter-process operations");
TUNABLE_INT("security.mac.enforce_process", &mac_enforce_process);

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");
TUNABLE_INT("security.mac.enforce_vm", &mac_enforce_vm);

static int	mac_mmap_revocation = 1;
SYSCTL_INT(_security_mac, OID_AUTO, mmap_revocation, CTLFLAG_RW,
    &mac_mmap_revocation, 0, "Revoke mmap access to files on subject "
    "relabel");

static int	mac_mmap_revocation_via_cow = 0;
SYSCTL_INT(_security_mac, OID_AUTO, mmap_revocation_via_cow, CTLFLAG_RW,
    &mac_mmap_revocation_via_cow, 0, "Revoke mmap access to files via "
    "copy-on-write semantics, or by removing all write access");

#ifdef MAC_DEBUG
static unsigned int nmaccreds, nmacprocs;
SYSCTL_UINT(_security_mac_debug_counters, OID_AUTO, creds, CTLFLAG_RD,
    &nmaccreds, 0, "number of ucreds in use");
SYSCTL_UINT(_security_mac_debug_counters, OID_AUTO, procs, CTLFLAG_RD,
    &nmacprocs, 0, "number of procs in use");
#endif

static void	mac_cred_mmapped_drop_perms_recurse(struct thread *td,
		    struct ucred *cred, struct vm_map *map);

struct label *
mac_cred_label_alloc(void)
{
	struct label *label;

	label = mac_labelzone_alloc(M_WAITOK);
	MAC_PERFORM(init_cred_label, label);
	MAC_DEBUG_COUNTER_INC(&nmaccreds);
	return (label);
}

void
mac_init_cred(struct ucred *cred)
{

	cred->cr_label = mac_cred_label_alloc();
}

static struct label *
mac_proc_label_alloc(void)
{
	struct label *label;

	label = mac_labelzone_alloc(M_WAITOK);
	MAC_PERFORM(init_proc_label, label);
	MAC_DEBUG_COUNTER_INC(&nmacprocs);
	return (label);
}

void
mac_init_proc(struct proc *p)
{

	p->p_label = mac_proc_label_alloc();
}

void
mac_cred_label_free(struct label *label)
{

	MAC_PERFORM(destroy_cred_label, label);
	mac_labelzone_free(label);
	MAC_DEBUG_COUNTER_DEC(&nmaccreds);
}

void
mac_destroy_cred(struct ucred *cred)
{

	mac_cred_label_free(cred->cr_label);
	cred->cr_label = NULL;
}

static void
mac_proc_label_free(struct label *label)
{

	MAC_PERFORM(destroy_proc_label, label);
	mac_labelzone_free(label);
	MAC_DEBUG_COUNTER_DEC(&nmacprocs);
}

void
mac_destroy_proc(struct proc *p)
{

	mac_proc_label_free(p->p_label);
	p->p_label = NULL;
}

int
mac_externalize_cred_label(struct label *label, char *elements,
    char *outbuf, size_t outbuflen)
{
	int error;

	MAC_EXTERNALIZE(cred, label, elements, outbuf, outbuflen);

	return (error);
}

int
mac_internalize_cred_label(struct label *label, char *string)
{
	int error;

	MAC_INTERNALIZE(cred, label, string);

	return (error);
}

/*
 * Initialize MAC label for the first kernel process, from which other
 * kernel processes and threads are spawned.
 */
void
mac_create_proc0(struct ucred *cred)
{

	MAC_PERFORM(create_proc0, cred);
}

/*
 * Initialize MAC label for the first userland process, from which other
 * userland processes and threads are spawned.
 */
void
mac_create_proc1(struct ucred *cred)
{

	MAC_PERFORM(create_proc1, cred);
}

void
mac_thread_userret(struct thread *td)
{

	MAC_PERFORM(thread_userret, td);
}

/*
 * When a new process is created, its label must be initialized.  Generally,
 * this involves inheritence from the parent process, modulo possible
 * deltas.  This function allows that processing to take place.
 */
void
mac_copy_cred(struct ucred *src, struct ucred *dest)
{

	MAC_PERFORM(copy_cred_label, src->cr_label, dest->cr_label);
}

int
mac_execve_enter(struct image_params *imgp, struct mac *mac_p)
{
	struct label *label;
	struct mac mac;
	char *buffer;
	int error;

	if (mac_p == NULL)
		return (0);

	error = copyin(mac_p, &mac, sizeof(mac));
	if (error)
		return (error);

	error = mac_check_structmac_consistent(&mac);
	if (error)
		return (error);

	buffer = malloc(mac.m_buflen, M_MACTEMP, M_WAITOK);
	error = copyinstr(mac.m_string, buffer, mac.m_buflen, NULL);
	if (error) {
		free(buffer, M_MACTEMP);
		return (error);
	}

	label = mac_cred_label_alloc();
	error = mac_internalize_cred_label(label, buffer);
	free(buffer, M_MACTEMP);
	if (error) {
		mac_cred_label_free(label);
		return (error);
	}
	imgp->execlabel = label;
	return (0);
}

void
mac_execve_exit(struct image_params *imgp)
{
	if (imgp->execlabel != NULL) {
		mac_cred_label_free(imgp->execlabel);
		imgp->execlabel = NULL;
	}
}

/*
 * When relabeling a process, call out to the policies for the maximum
 * permission allowed for each object type we know about in its
 * memory space, and revoke access (in the least surprising ways we
 * know) when necessary.  The process lock is not held here.
 */
void
mac_cred_mmapped_drop_perms(struct thread *td, struct ucred *cred)
{

	/* XXX freeze all other threads */
	mac_cred_mmapped_drop_perms_recurse(td, cred,
	    &td->td_proc->p_vmspace->vm_map);
	/* XXX allow other threads to continue */
}

static __inline const char *
prot2str(vm_prot_t prot)
{

	switch (prot & VM_PROT_ALL) {
	case VM_PROT_READ:
		return ("r--");
	case VM_PROT_READ | VM_PROT_WRITE:
		return ("rw-");
	case VM_PROT_READ | VM_PROT_EXECUTE:
		return ("r-x");
	case VM_PROT_READ | VM_PROT_WRITE | VM_PROT_EXECUTE:
		return ("rwx");
	case VM_PROT_WRITE:
		return ("-w-");
	case VM_PROT_EXECUTE:
		return ("--x");
	case VM_PROT_WRITE | VM_PROT_EXECUTE:
		return ("-wx");
	default:
		return ("---");
	}
}

static void
mac_cred_mmapped_drop_perms_recurse(struct thread *td, struct ucred *cred,
    struct vm_map *map)
{
	struct vm_map_entry *vme;
	int result;
	vm_prot_t revokeperms;
	vm_object_t object;
	vm_ooffset_t offset;
	struct vnode *vp;

	if (!mac_mmap_revocation)
		return;

	vm_map_lock_read(map);
	for (vme = map->header.next; vme != &map->header; vme = vme->next) {
		if (vme->eflags & MAP_ENTRY_IS_SUB_MAP) {
			mac_cred_mmapped_drop_perms_recurse(td, cred,
			    vme->object.sub_map);
			continue;
		}
		/*
		 * Skip over entries that obviously are not shared.
		 */
		if (vme->eflags & (MAP_ENTRY_COW | MAP_ENTRY_NOSYNC) ||
		    !vme->max_protection)
			continue;
		/*
		 * Drill down to the deepest backing object.
		 */
		offset = vme->offset;
		object = vme->object.vm_object;
		if (object == NULL)
			continue;
		while (object->backing_object != NULL) {
			object = object->backing_object;
			offset += object->backing_object_offset;
		}
		/*
		 * At the moment, vm_maps and objects aren't considered
		 * by the MAC system, so only things with backing by a
		 * normal object (read: vnodes) are checked.
		 */
		if (object->type != OBJT_VNODE)
			continue;
		vp = (struct vnode *)object->handle;
		vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td);
		result = vme->max_protection;
		mac_check_vnode_mmap_downgrade(cred, vp, &result);
		VOP_UNLOCK(vp, 0, td);
		/*
		 * Find out what maximum protection we may be allowing
		 * now but a policy needs to get removed.
		 */
		revokeperms = vme->max_protection & ~result;
		if (!revokeperms)
			continue;
		printf("pid %ld: revoking %s perms from %#lx:%ld "
		    "(max %s/cur %s)\n", (long)td->td_proc->p_pid,
		    prot2str(revokeperms), (u_long)vme->start,
		    (long)(vme->end - vme->start),
		    prot2str(vme->max_protection), prot2str(vme->protection));
		vm_map_lock_upgrade(map);
		/*
		 * This is the really simple case: if a map has more
		 * max_protection than is allowed, but it's not being
		 * actually used (that is, the current protection is
		 * still allowed), we can just wipe it out and do
		 * nothing more.
		 */
		if ((vme->protection & revokeperms) == 0) {
			vme->max_protection -= revokeperms;
		} else {
			if (revokeperms & VM_PROT_WRITE) {
				/*
				 * In the more complicated case, flush out all
				 * pending changes to the object then turn it
				 * copy-on-write.
				 */
				vm_object_reference(object);
				vn_lock(vp, LK_EXCLUSIVE | LK_RETRY, td);
				VM_OBJECT_LOCK(object);
				vm_object_page_clean(object,
				    OFF_TO_IDX(offset),
				    OFF_TO_IDX(offset + vme->end - vme->start +
					PAGE_MASK),
				    OBJPC_SYNC);
				VM_OBJECT_UNLOCK(object);
				VOP_UNLOCK(vp, 0, td);
				vm_object_deallocate(object);
				/*
				 * Why bother if there's no read permissions
				 * anymore?  For the rest, we need to leave
				 * the write permissions on for COW, or
				 * remove them entirely if configured to.
				 */
				if (!mac_mmap_revocation_via_cow) {
					vme->max_protection &= ~VM_PROT_WRITE;
					vme->protection &= ~VM_PROT_WRITE;
				} if ((revokeperms & VM_PROT_READ) == 0)
					vme->eflags |= MAP_ENTRY_COW |
					    MAP_ENTRY_NEEDS_COPY;
			}
			if (revokeperms & VM_PROT_EXECUTE) {
				vme->max_protection &= ~VM_PROT_EXECUTE;
				vme->protection &= ~VM_PROT_EXECUTE;
			}
			if (revokeperms & VM_PROT_READ) {
				vme->max_protection = 0;
				vme->protection = 0;
			}
			pmap_protect(map->pmap, vme->start, vme->end,
			    vme->protection & ~revokeperms);
			vm_map_simplify_entry(map, vme);
		}
		vm_map_lock_downgrade(map);
	}
	vm_map_unlock_read(map);
}

/*
 * When the subject's label changes, it may require revocation of privilege
 * to mapped objects.  This can't be done on-the-fly later with a unified
 * buffer cache.
 */
void
mac_relabel_cred(struct ucred *cred, struct label *newlabel)
{

	MAC_PERFORM(relabel_cred, cred, newlabel);
}

int
mac_check_cred_relabel(struct ucred *cred, struct label *newlabel)
{
	int error;

	MAC_CHECK(check_cred_relabel, cred, newlabel);

	return (error);
}

int
mac_check_cred_visible(struct ucred *u1, struct ucred *u2)
{
	int error;

	if (!mac_enforce_process)
		return (0);

	MAC_CHECK(check_cred_visible, u1, u2);

	return (error);
}

int
mac_check_proc_debug(struct ucred *cred, struct proc *proc)
{
	int error;

	PROC_LOCK_ASSERT(proc, MA_OWNED);

	if (!mac_enforce_process)
		return (0);

	MAC_CHECK(check_proc_debug, cred, proc);

	return (error);
}

int
mac_check_proc_sched(struct ucred *cred, struct proc *proc)
{
	int error;

	PROC_LOCK_ASSERT(proc, MA_OWNED);

	if (!mac_enforce_process)
		return (0);

	MAC_CHECK(check_proc_sched, cred, proc);

	return (error);
}

int
mac_check_proc_signal(struct ucred *cred, struct proc *proc, int signum)
{
	int error;

	PROC_LOCK_ASSERT(proc, MA_OWNED);

	if (!mac_enforce_process)
		return (0);

	MAC_CHECK(check_proc_signal, cred, proc, signum);

	return (error);
}