/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2011-2023 Juniper Networks, Inc.
 * All rights reserved.
 *
 * 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 ``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 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>

#include "opt_capsicum.h"
#include "opt_mac.h"

#include <sys/param.h>
#include <sys/systm.h>
#include <sys/capsicum.h>
#include <sys/eventhandler.h>
#include <sys/fcntl.h>
#include <sys/file.h>
#include <sys/filedesc.h>
#include <sys/imgact.h>
#include <sys/jail.h>
#include <sys/kernel.h>
#include <sys/mac.h>
#include <sys/mount.h>
#include <sys/namei.h>
#include <sys/priv.h>
#include <sys/proc.h>
#include <sys/sbuf.h>
#include <sys/stat.h>
#include <sys/sysctl.h>
#include <sys/vnode.h>
#ifdef COMPAT_FREEBSD32
#include <sys/sysent.h>
#include <sys/stdint.h>
#include <sys/abi_compat.h>
#endif
#include <fs/nullfs/null.h>
#include <security/mac/mac_framework.h>
#include <security/mac/mac_policy.h>

#include "mac_veriexec.h"
#include "mac_veriexec_internal.h"

#define SLOT(l) \
        mac_label_get((l), mac_veriexec_slot)
#define SLOT_SET(l, v) \
        mac_label_set((l), mac_veriexec_slot, (v))

#ifdef MAC_VERIEXEC_DEBUG
#define MAC_VERIEXEC_DBG(_lvl, _fmt, ...)                               \
        do {                                                            \
                VERIEXEC_DEBUG((_lvl), (MAC_VERIEXEC_FULLNAME ": " _fmt \
                     "\n", ##__VA_ARGS__));                             \
        } while(0)
#else
#define MAC_VERIEXEC_DBG(_lvl, _fmt, ...)
#endif

static int sysctl_mac_veriexec_state(SYSCTL_HANDLER_ARGS);
static int sysctl_mac_veriexec_db(SYSCTL_HANDLER_ARGS);
static struct mac_policy_ops mac_veriexec_ops;

SYSCTL_NODE(_security_mac, OID_AUTO, veriexec, CTLFLAG_RW | CTLFLAG_MPSAFE, 0,
    "MAC/veriexec policy controls");

int     mac_veriexec_debug;
SYSCTL_INT(_security_mac_veriexec, OID_AUTO, debug, CTLFLAG_RW,
    &mac_veriexec_debug, 0, "Debug level");

static int      mac_veriexec_state;
SYSCTL_PROC(_security_mac_veriexec, OID_AUTO, state,
    CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_NEEDGIANT,
    0, 0, sysctl_mac_veriexec_state, "A",
    "Verified execution subsystem state");

SYSCTL_PROC(_security_mac_veriexec, OID_AUTO, db,
    CTLTYPE_STRING | CTLFLAG_RD | CTLFLAG_SKIP | CTLFLAG_NEEDGIANT,
    0, 0, sysctl_mac_veriexec_db,
    "A", "Verified execution fingerprint database");


static int mac_veriexec_slot;

static int mac_veriexec_block_unlink;
SYSCTL_INT(_security_mac_veriexec, OID_AUTO, block_unlink, CTLFLAG_RDTUN,
    &mac_veriexec_block_unlink, 0, "Veriexec unlink protection");

MALLOC_DEFINE(M_VERIEXEC, "veriexec", "Verified execution data");

/**
 * @internal
 * @brief Handler for security.mac.veriexec.db sysctl
 *
 * Display a human-readable form of the current fingerprint database.
 */
static int
sysctl_mac_veriexec_db(SYSCTL_HANDLER_ARGS)
{
        struct sbuf sb;
        int error;

        error = sysctl_wire_old_buffer(req, 0);
        if (error != 0)
                return (error);

        sbuf_new_for_sysctl(&sb, NULL, 1024, req);
        mac_veriexec_metadata_print_db(&sb);
        error = sbuf_finish(&sb);
        sbuf_delete(&sb);

        return (error);
}

/**
 * @internal
 * @brief Generate human-readable output about the current verified execution
 *        state.
 *
 * @param sbp           sbuf to write output to
 */
static void
mac_veriexec_print_state(struct sbuf *sbp)
{

        if (mac_veriexec_state & VERIEXEC_STATE_INACTIVE)
                sbuf_printf(sbp, "inactive ");
        if (mac_veriexec_state & VERIEXEC_STATE_LOADED)
                sbuf_printf(sbp, "loaded ");
        if (mac_veriexec_state & VERIEXEC_STATE_ACTIVE)
                sbuf_printf(sbp, "active ");
        if (mac_veriexec_state & VERIEXEC_STATE_ENFORCE)
                sbuf_printf(sbp, "enforce ");
        if (mac_veriexec_state & VERIEXEC_STATE_LOCKED)
                sbuf_printf(sbp, "locked ");
        if (mac_veriexec_state != 0)
                sbuf_trim(sbp);
}

/**
 * @internal
 * @brief Handler for security.mac.veriexec.state sysctl
 *
 * Display a human-readable form of the current verified execution subsystem
 * state.
 */
static int
sysctl_mac_veriexec_state(SYSCTL_HANDLER_ARGS)
{
        struct sbuf sb;
        int error;

        sbuf_new(&sb, NULL, 128, SBUF_AUTOEXTEND);
        mac_veriexec_print_state(&sb);
        sbuf_finish(&sb);

        error = SYSCTL_OUT(req, sbuf_data(&sb), sbuf_len(&sb));
        sbuf_delete(&sb);
        return (error);
}

/**
 * @internal
 * @brief Event handler called when a virtual file system is mounted.
 *
 * We need to record the file system identifier in the MAC per-policy slot
 * assigned to veriexec, so we have a key to use in order to reference the
 * mount point in the meta-data store.
 *
 * @param arg           unused argument
 * @param mp            mount point that is being mounted
 * @param fsrootvp      vnode of the file system root
 * @param td            calling thread
 */
static void
mac_veriexec_vfs_mounted(void *arg __unused, struct mount *mp,
    struct vnode *fsrootvp, struct thread *td)
{
        struct vattr va;
        int error;

        error = VOP_GETATTR(fsrootvp, &va, td->td_ucred);
        if (error)
                return;

        SLOT_SET(mp->mnt_label, va.va_fsid);
        MAC_VERIEXEC_DBG(3, "set fsid to %ju for mount %p",
            (uintmax_t)va.va_fsid, mp);
}

/**
 * @internal
 * @brief Event handler called when a virtual file system is unmounted.
 *
 * If we recorded a file system identifier in the MAC per-policy slot assigned
 * to veriexec, then we need to tell the meta-data store to clean up.
 *
 * @param arg           unused argument
 * @param mp            mount point that is being unmounted
 * @param td            calling thread
 */
static void
mac_veriexec_vfs_unmounted(void *arg __unused, struct mount *mp,
    struct thread *td)
{
        dev_t fsid;

        fsid = SLOT(mp->mnt_label);
        if (fsid) {
                MAC_VERIEXEC_DBG(3, "fsid %ju, cleaning up mount",
                    (uintmax_t)fsid);
                mac_veriexec_metadata_unmounted(fsid, td);
        }
}

/**
 * @internal
 * @brief The mount point is being initialized, set the value in the MAC
 *     per-policy slot for veriexec to zero.
 *
 * @note A value of zero in this slot indicates no file system identifier
 *     is assigned.
 *
 * @param label the label that is being initialized
 */
static void
mac_veriexec_mount_init_label(struct label *label)
{

        SLOT_SET(label, 0);
}

/**
 * @internal
 * @brief The mount-point is being destroyed, reset the value in the MAC
 *     per-policy slot for veriexec back to zero.
 *
 * @note A value of zero in this slot indicates no file system identifier
 *     is assigned.
 *
 * @param label the label that is being destroyed
 */
static void
mac_veriexec_mount_destroy_label(struct label *label)
{

        SLOT_SET(label, 0);
}

/**
 * @internal
 * @brief The vnode label is being initialized, set the value in the MAC
 *     per-policy slot for veriexec to @c FINGERPRINT_INVALID
 *
 * @note @c FINGERPRINT_INVALID indicates the fingerprint is invalid.
 *
 * @param label         the label that is being initialized
 */
static void
mac_veriexec_vnode_init_label(struct label *label)
{

        SLOT_SET(label, FINGERPRINT_INVALID);
}

/**
 * @internal
 * @brief The vnode label is being destroyed, reset the value in the MAC
 *        per-policy slot for veriexec back to @c FINGERPRINT_INVALID
 *
 * @note @c FINGERPRINT_INVALID indicates the fingerprint is invalid.
 *
 * @param label         the label that is being destroyed
 */
static void
mac_veriexec_vnode_destroy_label(struct label *label)
{

        SLOT_SET(label, FINGERPRINT_INVALID);
}

/**
 * @internal
 * @brief Copy the value in the MAC per-policy slot assigned to veriexec from
 *        the @p src label to the @p dest label
 */
static void
mac_veriexec_copy_label(struct label *src, struct label *dest)
{

        SLOT_SET(dest, SLOT(src));
}

/**
 * @internal
 * @brief Check if the requested process can be debugged
 *
 * @param cred          credentials to use
 * @param p             process to debug
 *
 * @return 0 if debugging is allowed, otherwise an error code.
 */
static int
mac_veriexec_proc_check_debug(struct ucred *cred, struct proc *p)
{
        int error, flags;

        /* If we are not enforcing veriexec, nothing for us to check */
        if ((mac_veriexec_state & VERIEXEC_STATE_ENFORCE) == 0)
                return (0);

        error = mac_veriexec_metadata_get_executable_flags(cred, p, &flags, 0);
        if (error != 0)
                return (0);

        error = (flags & (VERIEXEC_NOTRACE|VERIEXEC_TRUSTED)) ? EACCES : 0;
        MAC_VERIEXEC_DBG(4, "%s flags=%#x error=%d", __func__, flags, error);

        return (error);
}

/**
 * @internal
 * @brief A KLD load has been requested and needs to be validated.
 *
 * @param cred          credentials to use
 * @param vp            vnode of the KLD that has been requested
 * @param vlabel        vnode label assigned to the vnode
 *
 * @return 0 if the KLD load is allowed, otherwise an error code.
 */
static int
mac_veriexec_kld_check_load(struct ucred *cred, struct vnode *vp,
    struct label *vlabel)
{
        struct vattr va;
        struct thread *td = curthread;
        fingerprint_status_t status;
        int error;

        /*
         * If we are not actively enforcing, allow it
         */
        if ((mac_veriexec_state & VERIEXEC_STATE_ENFORCE) == 0)
                return (0);

        /* Get vnode attributes */
        error = VOP_GETATTR(vp, &va, cred);
        if (error)
                return (error);

        /*
         * Fetch the fingerprint status for the vnode
         * (starting with files first)
         */
        error = mac_veriexec_metadata_fetch_fingerprint_status(vp, &va, td,
            VERIEXEC_FILES_FIRST);
        if (error && error != EAUTH)
                return (error);

        /*
         * By now we should have status...
         */
        status = mac_veriexec_get_fingerprint_status(vp);
        switch (status) {
        case FINGERPRINT_FILE:
        case FINGERPRINT_VALID:
        case FINGERPRINT_INDIRECT:
                if (error)
                        return (error);
                break;
        default:
                /*
                 * kldload should fail unless there is a valid fingerprint
                 * registered.
                 */
                MAC_VERIEXEC_DBG(2, "fingerprint status is %d for dev %ju, "
                    "file %ju.%ju\n", status, (uintmax_t)va.va_fsid,
                    (uintmax_t)va.va_fileid, (uintmax_t)va.va_gen);
                return (EAUTH);
        }

        /* Everything is good, allow the KLD to be loaded */
        return (0);
}

/**
 * @internal
 * @brief Check privileges that veriexec needs to be concerned about.
 *
 * The following privileges are checked by this function:
 *  - PRIV_KMEM_WRITE\n
 *    Check if writes to /dev/mem and /dev/kmem are allowed\n
 *    (Only trusted processes are allowed)
 *  - PRIV_VERIEXEC_CONTROL\n
 *    Check if manipulating veriexec is allowed\n
 *    (only trusted processes are allowed)
 *
 * @param cred          credentials to use
 * @param priv          privilege to check
 *
 * @return 0 if the privilege is allowed, error code otherwise.
 */
static int
mac_veriexec_priv_check(struct ucred *cred, int priv)
{
        int error;

        /* If we are not enforcing veriexec, nothing for us to check */
        if ((mac_veriexec_state & VERIEXEC_STATE_ENFORCE) == 0)
                return (0);

        error = 0;
        switch (priv) {
        case PRIV_KMEM_WRITE:
        case PRIV_PROC_MEM_WRITE:
        case PRIV_VERIEXEC_CONTROL:
                /*
                 * Do not allow writing to memory or manipulating veriexec,
                 * unless trusted
                 */
                if (mac_veriexec_proc_is_trusted(cred, curproc) == 0 &&
                    mac_priv_grant(cred, priv) != 0)
                        error = EPERM;
                MAC_VERIEXEC_DBG(4, "%s priv=%d error=%d", __func__, priv,
                    error);
                break;
        default:
                break;
        }
        return (error);
}

/**
 * @internal
 * @brief Check if the requested sysctl should be allowed
 *
 * @param cred         credentials to use
 * @param oidp         sysctl OID
 * @param arg1         first sysctl argument
 * @param arg2         second sysctl argument
 * @param req          sysctl request information
 *
 * @return 0 if the sysctl should be allowed, otherwise an error code.
 */
static int
mac_veriexec_sysctl_check(struct ucred *cred, struct sysctl_oid *oidp,
    void *arg1, int arg2, struct sysctl_req *req)
{
        struct sysctl_oid *oid;

        /* If we are not enforcing veriexec, nothing for us to check */
        if ((mac_veriexec_state & VERIEXEC_STATE_ENFORCE) == 0)
                return (0);

        oid = oidp;
        if (req->newptr && (oid->oid_kind & CTLFLAG_SECURE)) {
                return (EPERM);         /* XXX call mac_veriexec_priv_check? */
        }
        return 0;
}

/**
 * @internal
 * @brief A program is being executed and needs to be validated.
 *
 * @param cred          credentials to use
 * @param vp            vnode of the program that is being executed
 * @param label         vnode label assigned to the vnode
 * @param imgp          parameters for the image to be executed
 * @param execlabel     optional exec label
 *
 * @return 0 if the program should be allowed to execute, otherwise an error
 *     code.
 */
static int
mac_veriexec_vnode_check_exec(struct ucred *cred __unused,
    struct vnode *vp __unused, struct label *label __unused,
    struct image_params *imgp, struct label *execlabel __unused)
{
        struct thread *td = curthread;
        int error;

        error = mac_veriexec_fingerprint_check_image(imgp, 0, td);
        return (error);
}

/**
 * @brief Check fingerprint for the specified vnode and validate it
 *
 * @param cred          credentials to use
 * @param vp            vnode of the file
 * @param accmode       access mode to check (read, write, append, create,
 *                      verify, etc.)
 *
 * @return 0 if the file validated, otherwise an error code.
 */
static int
mac_veriexec_check_vp(struct ucred *cred, struct vnode *vp, accmode_t accmode)
{
        struct vattr va;
        struct thread *td = curthread;
        fingerprint_status_t status;
        int error;

        /* Get vnode attributes */
        error = VOP_GETATTR(vp, &va, cred);
        if (error)
                return (error);

        /* Get the fingerprint status for the file */
        error = mac_veriexec_metadata_fetch_fingerprint_status(vp, &va, td,
            VERIEXEC_FILES_FIRST);
        if (error && error != EAUTH)
                return (error);

        /*
         * By now we should have status...
         */
        status = mac_veriexec_get_fingerprint_status(vp);
        if (accmode & VWRITE) {
                /*
                 * If file has a fingerprint then deny the write request,
                 * otherwise invalidate the status so we don't keep checking
                 * for the file having a fingerprint.
                 */
                switch (status) {
                case FINGERPRINT_FILE:
                case FINGERPRINT_VALID:
                case FINGERPRINT_INDIRECT:
                        MAC_VERIEXEC_DBG(2,
                            "attempted write to fingerprinted file for dev "
                            "%ju, file %ju.%ju\n", (uintmax_t)va.va_fsid,
                            (uintmax_t)va.va_fileid, (uintmax_t)va.va_gen);
                        return (EPERM);
                default:
                        break;
                }
        }
        if (accmode & VVERIFY) {
                switch (status) {
                case FINGERPRINT_FILE:
                case FINGERPRINT_VALID:
                case FINGERPRINT_INDIRECT:
                        if (error)
                                return (error);
                        break;
                default:
                        /* Allow for overriding verification requirement */
                        if (mac_priv_grant(cred, PRIV_VERIEXEC_NOVERIFY) == 0)
                                return (0);
                        /*
                         * Caller wants open to fail unless there is a valid
                         * fingerprint registered.
                         */
                        MAC_VERIEXEC_DBG(2, "fingerprint status is %d for dev "
                            "%ju, file %ju.%ju\n", status,
                            (uintmax_t)va.va_fsid, (uintmax_t)va.va_fileid,
                            (uintmax_t)va.va_gen);
                        return (EAUTH);
                }
        }
        return (0);
}

/**
 * @brief Opening a file has been requested and may need to be validated.
 *
 * @param cred          credentials to use
 * @param vp            vnode of the file to open
 * @param label         vnode label assigned to the vnode
 * @param accmode       access mode to use for opening the file (read, write,
 *                      append, create, verify, etc.)
 *
 * @return 0 if opening the file should be allowed, otherwise an error code.
 */
static int
mac_veriexec_vnode_check_open(struct ucred *cred, struct vnode *vp,
        struct label *label __unused, accmode_t accmode)
{
        int error;

        /*
         * Look for the file on the fingerprint lists iff it has not been seen
         * before.
         */
        if ((mac_veriexec_state & VERIEXEC_STATE_ENFORCE) == 0)
                return (0);

        error = mac_veriexec_check_vp(cred, vp, accmode);
        return (error);
}

/**
 * @brief Unlink on a file has been requested and may need to be validated.
 *
 * @param cred          credentials to use
 * @param dvp           parent directory for file vnode vp
 * @param dlabel        vnode label assigned to the directory vnode
 * @param vp            vnode of the file to unlink
 * @param label         vnode label assigned to the vnode
 * @param cnp           component name for vp
 *
 *
 * @return 0 if opening the file should be allowed, otherwise an error code.
 */
static int
mac_veriexec_vnode_check_unlink(struct ucred *cred, struct vnode *dvp __unused,
    struct label *dvplabel __unused, struct vnode *vp,
    struct label *label __unused, struct componentname *cnp __unused)
{
        int error;

        /*
         * Look for the file on the fingerprint lists iff it has not been seen
         * before.
         */
        if ((mac_veriexec_state & VERIEXEC_STATE_ENFORCE) == 0)
                return (0);

        error = mac_veriexec_check_vp(cred, vp, VVERIFY);
        if (error == 0) {
                /*
                 * The target is verified, so disallow replacement.
                 */
                MAC_VERIEXEC_DBG(2,
    "(UNLINK) attempted to unlink a protected file (euid: %u)", cred->cr_uid);

                return (EAUTH);
        }
        return (0);
}

/**
 * @brief Rename the file has been requested and may need to be validated.
 *
 * @param cred          credentials to use
 * @param dvp           parent directory for file vnode vp
 * @param dlabel        vnode label assigned to the directory vnode
 * @param vp            vnode of the file to rename
 * @param label         vnode label assigned to the vnode
 * @param cnp           component name for vp
 *
 *
 * @return 0 if opening the file should be allowed, otherwise an error code.
 */
static int
mac_veriexec_vnode_check_rename_from(struct ucred *cred,
    struct vnode *dvp __unused, struct label *dvplabel __unused,
    struct vnode *vp, struct label *label __unused,
    struct componentname *cnp __unused)
{
        int error;

        /*
         * Look for the file on the fingerprint lists iff it has not been seen
         * before.
         */
        if ((mac_veriexec_state & VERIEXEC_STATE_ENFORCE) == 0)
                return (0);

        error = mac_veriexec_check_vp(cred, vp, VVERIFY);
        if (error == 0) {
                /*
                 * The target is verified, so disallow replacement.
                 */
                MAC_VERIEXEC_DBG(2,
    "(RENAME_FROM) attempted to rename a protected file (euid: %u)", cred->cr_uid);
                return (EAUTH);
        }
        return (0);
}


/**
 * @brief Rename to file into the directory (overwrite the file name) has been
 * requested and may need to be validated.
 *
 * @param cred          credentials to use
 * @param dvp           parent directory for file vnode vp
 * @param dlabel        vnode label assigned to the directory vnode
 * @param vp            vnode of the overwritten file
 * @param label         vnode label assigned to the vnode
 * @param samedir       1 if the source and destination directories are the same
 * @param cnp           component name for vp
 *
 *
 * @return 0 if opening the file should be allowed, otherwise an error code.
 */
        static int
mac_veriexec_vnode_check_rename_to(struct ucred *cred, struct vnode *dvp __unused,
    struct label *dvplabel __unused, struct vnode *vp,
    struct label *label __unused, int samedir __unused,
    struct componentname *cnp __unused)
{
        int error;
        /*
         * If there is no existing file to overwrite, vp and label will be
         * NULL.
         */
        if (vp == NULL)
                return (0);

        /*
         * Look for the file on the fingerprint lists iff it has not been seen
         * before.
         */
        if ((mac_veriexec_state & VERIEXEC_STATE_ENFORCE) == 0)
                return (0);

        error = mac_veriexec_check_vp(cred, vp, VVERIFY);
        if (error == 0) {
                /*
                 * The target is verified, so disallow replacement.
                 */
                MAC_VERIEXEC_DBG(2,
    "(RENAME_TO) attempted to overwrite a protected file (euid: %u)", cred->cr_uid);
                return (EAUTH);
        }
        return (0);
}


/**
 * @brief Check mode changes on file to ensure they should be allowed.
 *
 * We cannot allow chmod of SUID or SGID on verified files.
 *
 * @param cred          credentials to use
 * @param vp            vnode of the file to open
 * @param label         vnode label assigned to the vnode
 * @param mode          mode flags to set
 *
 * @return 0 if the mode change should be allowed, EAUTH otherwise.
 */
static int
mac_veriexec_vnode_check_setmode(struct ucred *cred, struct vnode *vp,
    struct label *label __unused, mode_t mode)
{
        int error;

        if ((mac_veriexec_state & VERIEXEC_STATE_ENFORCE) == 0)
                return (0);

        /*
         * Prohibit chmod of verified set-[gu]id file.
         */
        error = mac_veriexec_check_vp(cred, vp, VVERIFY);
        if (error == EAUTH)             /* target not verified */
                return (0);
        if (error == 0 && (mode & (S_ISUID|S_ISGID)) != 0)
                return (EAUTH);

        return (0);
}

/**
 * @internal
 * @brief Initialize the mac_veriexec MAC policy
 *
 * @param mpc           MAC policy configuration
 */
static void
mac_veriexec_init(struct mac_policy_conf *mpc __unused)
{
        /* Initialize state */
        mac_veriexec_state = VERIEXEC_STATE_INACTIVE;

        /* Initialize meta-data storage */
        mac_veriexec_metadata_init();

        /* Initialize fingerprint ops */
        mac_veriexec_fingerprint_init();

        /* Register event handlers */
        EVENTHANDLER_REGISTER(vfs_mounted, mac_veriexec_vfs_mounted, NULL,
            EVENTHANDLER_PRI_FIRST);
        EVENTHANDLER_REGISTER(vfs_unmounted, mac_veriexec_vfs_unmounted, NULL,
            EVENTHANDLER_PRI_LAST);

        /* Check if unlink control is activated via tunable value */
        if (!mac_veriexec_block_unlink)
                mac_veriexec_ops.mpo_vnode_check_unlink = NULL;
}

#ifdef COMPAT_FREEBSD32
struct mac_veriexec_syscall_params32  {
        char fp_type[VERIEXEC_FPTYPELEN];
        unsigned char fingerprint[MAXFINGERPRINTLEN];
        char label[MAXLABELLEN];
        uint32_t labellen;
        unsigned char flags;
};

struct mac_veriexec_syscall_params_args32 {
        union {
                pid_t pid;
                uint32_t filename;
        } u;                              /* input only */
        uint32_t params;                  /* result */
};
#endif

/**
 * @internal
 * @brief MAC policy-specific syscall for mac_veriexec
 *
 * The following syscalls are implemented:
 *   - @c MAC_VERIEXEC_CHECK_SYSCALL
 *        Check if the file referenced by a file descriptor has a fingerprint
 *        registered in the meta-data store.
 *
 * @param td            calling thread
 * @param call          system call number
 * @param arg           arugments to the syscall
 *
 * @return 0 on success, otherwise an error code.
 */
static int
mac_veriexec_syscall(struct thread *td, int call, void *arg)
{
        struct image_params img;
        struct nameidata nd;
        cap_rights_t rights;
        struct vattr va;
        struct file *fp;
        struct mac_veriexec_syscall_params_args pargs;
        struct mac_veriexec_syscall_params result;
#ifdef COMPAT_FREEBSD32
        struct mac_veriexec_syscall_params_args32 pargs32;
        struct mac_veriexec_syscall_params32 result32;
#endif
        struct mac_veriexec_file_info *ip;
        struct proc *proc;
        struct vnode *textvp;
        int error, flags, proc_locked;

        nd.ni_vp = NULL;
        proc_locked = 0;
        textvp = NULL;
        switch (call) {
        case MAC_VERIEXEC_GET_PARAMS_PID_SYSCALL:
        case MAC_VERIEXEC_GET_PARAMS_PATH_SYSCALL:
#ifdef COMPAT_FREEBSD32
                if (SV_PROC_FLAG(td->td_proc, SV_ILP32)) {
                        error = copyin(arg, &pargs32, sizeof(pargs32));
                        if (error)
                                return error;
                        bzero(&pargs, sizeof(pargs));
                        switch (call) {
                        case MAC_VERIEXEC_GET_PARAMS_PID_SYSCALL:
                                CP(pargs32, pargs, u.pid);
                                break;
                        case MAC_VERIEXEC_GET_PARAMS_PATH_SYSCALL:
                                PTRIN_CP(pargs32, pargs, u.filename);
                                break;
                        }
                        PTRIN_CP(pargs32, pargs, params);
                } else
#endif
                error = copyin(arg, &pargs, sizeof(pargs));
                if (error)
                        return error;
                break;
        }

        switch (call) {
        case MAC_VERIEXEC_CHECK_FD_SYSCALL:
                /* Get the vnode associated with the file descriptor passed */
                error = getvnode(td, (uintptr_t) arg,
                    cap_rights_init_one(&rights, CAP_READ), &fp);
                if (error)
                        return (error);
                if (fp->f_type != DTYPE_VNODE) {
                        MAC_VERIEXEC_DBG(3, "MAC_VERIEXEC_CHECK_SYSCALL: "
                            "file is not vnode type (type=0x%x)",
                            fp->f_type);
                        error = EINVAL;
                        goto cleanup_file;
                }

                /*
                 * setup the bits of image_params that are used by
                 * mac_veriexec_check_fingerprint().
                 */
                bzero(&img, sizeof(img));
                img.proc = td->td_proc;
                img.vp = fp->f_vnode;
                img.attr = &va;

                /*
                 * Get vnode attributes
                 * (need to obtain a lock on the vnode first)
                 */
                vn_lock(img.vp, LK_EXCLUSIVE | LK_RETRY);
                error = VOP_GETATTR(fp->f_vnode, &va,  td->td_ucred);
                if (error)
                        goto check_done;

                MAC_VERIEXEC_DBG(2, "mac_veriexec_fingerprint_check_image: "
                    "va_mode=%o, check_files=%d\n", va.va_mode,
                    ((va.va_mode & (S_IXUSR|S_IXGRP|S_IXOTH)) == 0));
                error = mac_veriexec_fingerprint_check_image(&img,
                    ((va.va_mode & (S_IXUSR|S_IXGRP|S_IXOTH)) == 0), td);
check_done:
                /* Release the lock we obtained earlier */
                VOP_UNLOCK(img.vp);
cleanup_file:
                fdrop(fp, td);
                break;
        case MAC_VERIEXEC_CHECK_PATH_SYSCALL:
                /* Look up the path to get the vnode */
                NDINIT(&nd, LOOKUP,
                    FOLLOW | LOCKLEAF | LOCKSHARED | AUDITVNODE1,
                    UIO_USERSPACE, arg);
                flags = FREAD;
                error = vn_open(&nd, &flags, 0, NULL);
                if (error != 0)
                        break;
                NDFREE_PNBUF(&nd);

                /* Check the fingerprint status of the vnode */
                error = mac_veriexec_check_vp(td->td_ucred, nd.ni_vp, VVERIFY);
                /* nd.ni_vp cleaned up below */
                break;
        case MAC_VERIEXEC_GET_PARAMS_PID_SYSCALL:
                if (pargs.u.pid == 0 || pargs.u.pid == curproc->p_pid) {
                        proc = curproc;
                } else {
                        proc = pfind(pargs.u.pid);
                        if (proc == NULL)
                                return (EINVAL);
                        proc_locked = 1;
                }
                textvp = proc->p_textvp;
                /* FALLTHROUGH */
        case MAC_VERIEXEC_GET_PARAMS_PATH_SYSCALL:
                if (textvp == NULL) {
                        /* Look up the path to get the vnode */
                        NDINIT(&nd, LOOKUP, FOLLOW | LOCKLEAF | AUDITVNODE1,
                            UIO_USERSPACE, pargs.u.filename);
                        flags = FREAD;
                        error = vn_open(&nd, &flags, 0, NULL);
                        if (error != 0)
                                break;

                        NDFREE_PNBUF(&nd);
                        textvp = nd.ni_vp;
                }
                error = VOP_GETATTR(textvp, &va, curproc->p_ucred);
                if (proc_locked)
                        PROC_UNLOCK(proc);
                if (error != 0)
                        break;

                error = mac_veriexec_metadata_get_file_info(va.va_fsid,
                    va.va_fileid, va.va_gen, NULL, &ip, FALSE);
                if (error != 0)
                        break;

#ifdef COMPAT_FREEBSD32
                if (SV_PROC_FLAG(td->td_proc, SV_ILP32)) {
                        bzero(&result32, sizeof(result32));
                        result32.flags = ip->flags;
                        strlcpy(result32.fp_type, ip->ops->type, sizeof(result32.fp_type));
                        result.labellen = ip->labellen;
                        CP(result, result32, labellen);
                        if (ip->labellen > 0)
                                strlcpy(result32.label, ip->label, sizeof(result32.label));
                        result32.label[result.labellen] = '\0';
                        memcpy(result32.fingerprint, ip->fingerprint,
                            ip->ops->digest_len);

                        error = copyout(&result32, pargs.params, sizeof(result32));
                        break;          /* yes */
                }
#endif
                bzero(&result, sizeof(result));
                result.flags = ip->flags;
                strlcpy(result.fp_type, ip->ops->type, sizeof(result.fp_type));
                result.labellen = ip->labellen;
                if (ip->labellen > 0)
                        strlcpy(result.label, ip->label, sizeof(result.label));
                result.label[result.labellen] = '\0';
                memcpy(result.fingerprint, ip->fingerprint,
                    ip->ops->digest_len);

                error = copyout(&result, pargs.params, sizeof(result));
                break;
        default:
                error = EOPNOTSUPP;
        }
        if (nd.ni_vp != NULL) {
                VOP_UNLOCK(nd.ni_vp);
                vn_close(nd.ni_vp, FREAD, td->td_ucred, td);
        }
        return (error);
}

static struct mac_policy_ops mac_veriexec_ops =
{
        .mpo_init = mac_veriexec_init,
        .mpo_kld_check_load = mac_veriexec_kld_check_load,
        .mpo_mount_destroy_label = mac_veriexec_mount_destroy_label,
        .mpo_mount_init_label = mac_veriexec_mount_init_label,
        .mpo_priv_check = mac_veriexec_priv_check,
        .mpo_proc_check_debug = mac_veriexec_proc_check_debug,
        .mpo_syscall = mac_veriexec_syscall,
        .mpo_system_check_sysctl = mac_veriexec_sysctl_check,
        .mpo_vnode_check_exec = mac_veriexec_vnode_check_exec,
        .mpo_vnode_check_open = mac_veriexec_vnode_check_open,
        .mpo_vnode_check_unlink = mac_veriexec_vnode_check_unlink,
        .mpo_vnode_check_rename_to = mac_veriexec_vnode_check_rename_to,
        .mpo_vnode_check_rename_from = mac_veriexec_vnode_check_rename_from,
        .mpo_vnode_check_setmode = mac_veriexec_vnode_check_setmode,
        .mpo_vnode_copy_label = mac_veriexec_copy_label,
        .mpo_vnode_destroy_label = mac_veriexec_vnode_destroy_label,
        .mpo_vnode_init_label = mac_veriexec_vnode_init_label,
};

MAC_POLICY_SET(&mac_veriexec_ops, mac_veriexec, MAC_VERIEXEC_FULLNAME,
    MPC_LOADTIME_FLAG_NOTLATE, &mac_veriexec_slot);
MODULE_VERSION(mac_veriexec, MAC_VERIEXEC_VERSION);

static struct vnode *
mac_veriexec_bottom_vnode(struct vnode *vp)
{
        struct vnode *ldvp = NULL;

        /*
         * XXX This code is bogus. nullfs is not the only stacking
         * filesystem. Less bogus code would add a VOP to reach bottom
         * vnode and would not make assumptions how to get there.
         */
        if (vp->v_mount != NULL &&
            strcmp(vp->v_mount->mnt_vfc->vfc_name, "nullfs") == 0)
                ldvp = NULLVPTOLOWERVP(vp);
        return (ldvp);
}

/**
 * @brief Get the fingerprint status set on a vnode.
 *
 * @param vp            vnode to obtain fingerprint status from
 *
 * @return Fingerprint status assigned to the vnode.
 */
fingerprint_status_t
mac_veriexec_get_fingerprint_status(struct vnode *vp)
{
        fingerprint_status_t fps;
        struct vnode *ldvp;

        fps = SLOT(vp->v_label);
        switch (fps) {
        case FINGERPRINT_VALID:
        case FINGERPRINT_INDIRECT:
        case FINGERPRINT_FILE:
                break;
        default:
                /* we may need to recurse */
                ldvp = mac_veriexec_bottom_vnode(vp);
                if (ldvp != NULL)
                        return mac_veriexec_get_fingerprint_status(ldvp);
                break;
        }
        return fps;
}

/**
 * @brief Get the current verified execution subsystem state.
 *
 * @return Current set of verified execution subsystem state flags.
 */
int
mac_veriexec_get_state(void)
{

        return (mac_veriexec_state);
}

/**
 * @brief Determine if the verified execution subsystem state has specific
 *     flags set.
 *
 * @param state         mask of flags to check
 *
 * @return State flags set within the masked bits
 */
int
mac_veriexec_in_state(int state)
{

        return (mac_veriexec_state & state);
}

/**
 * @brief Set the fingerprint status for a vnode
 *
 * Fingerprint status is stored in the MAC per-policy slot assigned to
 * mac_veriexec.
 *
 * @param vp            vnode to store the fingerprint status on
 * @param fp_status     fingerprint status to store
 */
void
mac_veriexec_set_fingerprint_status(struct vnode *vp,
    fingerprint_status_t fp_status)
{
        struct vnode *ldvp;

        /* recurse until we find the real storage */
        ldvp = mac_veriexec_bottom_vnode(vp);
        if (ldvp != NULL) {
                mac_veriexec_set_fingerprint_status(ldvp, fp_status);
                return;
        }
        SLOT_SET(vp->v_label, fp_status);
}

/**
 * @brief Set verified execution subsystem state flags
 *
 * @note Flags can only be added to the current state, not removed.
 *
 * @param state         state flags to add to the current state
 */
void
mac_veriexec_set_state(int state)
{

        mac_veriexec_state |= state;
}

/**
 * @brief Determine if the process is trusted
 *
 * @param cred          credentials to use
 * @param p             the process in question
 *
 * @return 1 if the process is trusted, otherwise 0.
 */
int
mac_veriexec_proc_is_trusted(struct ucred *cred, struct proc *p)
{
        int already_locked, error, flags;

        /* Make sure we lock the process if we do not already have the lock */
        already_locked = PROC_LOCKED(p);
        if (!already_locked)
                PROC_LOCK(p);

        error = mac_veriexec_metadata_get_executable_flags(cred, p, &flags, 0);

        /* Unlock the process if we locked it previously */
        if (!already_locked)
                PROC_UNLOCK(p);

        /* Any errors, deny access */
        if (error != 0)
                return (0);

        /* Check that the trusted flag is set */
        return ((flags & VERIEXEC_TRUSTED) == VERIEXEC_TRUSTED);
}