/*-
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Copyright (c) 2008-2010 Edward Tomasz Napierała <trasz@FreeBSD.org>
 *
 * 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.
 */

/*
 * ACL support routines specific to NFSv4 access control lists.  These are
 * utility routines for code common across file systems implementing NFSv4
 * ACLs.
 */

#ifdef _KERNEL

#include <sys/param.h>
#include <sys/kernel.h>
#include <sys/module.h>
#include <sys/systm.h>
#include <sys/mount.h>
#include <sys/priv.h>
#include <sys/vnode.h>
#include <sys/errno.h>
#include <sys/stat.h>
#include <sys/sysctl.h>
#include <sys/acl.h>
#else
#include <errno.h>
#include <assert.h>
#include <sys/acl.h>
#include <sys/stat.h>
#define KASSERT(a, b) assert(a)
#define CTASSERT(a)

#endif /* !_KERNEL */

#ifdef _KERNEL

static void     acl_nfs4_trivial_from_mode(struct acl *aclp, mode_t mode);

static int      acl_nfs4_old_semantics = 0;

SYSCTL_INT(_vfs, OID_AUTO, acl_nfs4_old_semantics, CTLFLAG_RW,
    &acl_nfs4_old_semantics, 0, "Use pre-PSARC/2010/029 NFSv4 ACL semantics");

static struct {
        accmode_t accmode;
        int mask;
} accmode2mask[] = {{VREAD, ACL_READ_DATA},
                    {VWRITE, ACL_WRITE_DATA},
                    {VAPPEND, ACL_APPEND_DATA},
                    {VEXEC, ACL_EXECUTE},
                    {VREAD_NAMED_ATTRS, ACL_READ_NAMED_ATTRS},
                    {VWRITE_NAMED_ATTRS, ACL_WRITE_NAMED_ATTRS},
                    {VDELETE_CHILD, ACL_DELETE_CHILD},
                    {VREAD_ATTRIBUTES, ACL_READ_ATTRIBUTES},
                    {VWRITE_ATTRIBUTES, ACL_WRITE_ATTRIBUTES},
                    {VDELETE, ACL_DELETE},
                    {VREAD_ACL, ACL_READ_ACL},
                    {VWRITE_ACL, ACL_WRITE_ACL},
                    {VWRITE_OWNER, ACL_WRITE_OWNER},
                    {VSYNCHRONIZE, ACL_SYNCHRONIZE},
                    {0, 0}};

static int
_access_mask_from_accmode(accmode_t accmode)
{
        int access_mask = 0, i;

        for (i = 0; accmode2mask[i].accmode != 0; i++) {
                if (accmode & accmode2mask[i].accmode)
                        access_mask |= accmode2mask[i].mask;
        }

        /*
         * VAPPEND is just a modifier for VWRITE; if the caller asked
         * for 'VAPPEND | VWRITE', we want to check for ACL_APPEND_DATA only.
         */
        if (access_mask & ACL_APPEND_DATA)
                access_mask &= ~ACL_WRITE_DATA;

        return (access_mask);
}

/*
 * Return 0, iff access is allowed, 1 otherwise.
 */
static int
_acl_denies(const struct acl *aclp, int access_mask, struct ucred *cred,
    int file_uid, int file_gid, int *denied_explicitly)
{
        int i;
        const struct acl_entry *entry;

        if (denied_explicitly != NULL)
                *denied_explicitly = 0;

        KASSERT(aclp->acl_cnt <= ACL_MAX_ENTRIES,
            ("aclp->acl_cnt <= ACL_MAX_ENTRIES"));

        for (i = 0; i < aclp->acl_cnt; i++) {
                entry = &(aclp->acl_entry[i]);

                if (entry->ae_entry_type != ACL_ENTRY_TYPE_ALLOW &&
                    entry->ae_entry_type != ACL_ENTRY_TYPE_DENY)
                        continue;
                if (entry->ae_flags & ACL_ENTRY_INHERIT_ONLY)
                        continue;
                switch (entry->ae_tag) {
                case ACL_USER_OBJ:
                        if (file_uid != cred->cr_uid)
                                continue;
                        break;
                case ACL_USER:
                        if (entry->ae_id != cred->cr_uid)
                                continue;
                        break;
                case ACL_GROUP_OBJ:
                        if (!groupmember(file_gid, cred))
                                continue;
                        break;
                case ACL_GROUP:
                        if (!groupmember(entry->ae_id, cred))
                                continue;
                        break;
                default:
                        KASSERT(entry->ae_tag == ACL_EVERYONE,
                            ("entry->ae_tag == ACL_EVERYONE"));
                }

                if (entry->ae_entry_type == ACL_ENTRY_TYPE_DENY) {
                        if (entry->ae_perm & access_mask) {
                                if (denied_explicitly != NULL)
                                        *denied_explicitly = 1;
                                return (1);
                        }
                }

                access_mask &= ~(entry->ae_perm);
                if (access_mask == 0)
                        return (0);
        }

        if (access_mask == 0)
                return (0);

        return (1);
}

int
vaccess_acl_nfs4(__enum_uint8(vtype) type, uid_t file_uid, gid_t file_gid,
    struct acl *aclp, accmode_t accmode, struct ucred *cred)
{
        accmode_t priv_granted = 0;
        int denied, explicitly_denied, access_mask, is_directory,
            must_be_owner = 0;
        mode_t file_mode = 0;

        KASSERT((accmode & ~(VEXEC | VWRITE | VREAD | VADMIN | VAPPEND |
            VEXPLICIT_DENY | VREAD_NAMED_ATTRS | VWRITE_NAMED_ATTRS |
            VDELETE_CHILD | VREAD_ATTRIBUTES | VWRITE_ATTRIBUTES | VDELETE |
            VREAD_ACL | VWRITE_ACL | VWRITE_OWNER | VSYNCHRONIZE)) == 0,
            ("invalid bit in accmode"));
        KASSERT((accmode & VAPPEND) == 0 || (accmode & VWRITE),
                ("VAPPEND without VWRITE"));

        if (accmode & VADMIN)
                must_be_owner = 1;

        /*
         * Ignore VSYNCHRONIZE permission.
         */
        accmode &= ~VSYNCHRONIZE;

        access_mask = _access_mask_from_accmode(accmode);

        if (type == VDIR)
                is_directory = 1;
        else
                is_directory = 0;

        /*
         * File owner is always allowed to read and write the ACL
         * and basic attributes.  This is to prevent a situation
         * where user would change ACL in a way that prevents him
         * from undoing the change.
         */
        if (file_uid == cred->cr_uid)
                access_mask &= ~(ACL_READ_ACL | ACL_WRITE_ACL |
                    ACL_READ_ATTRIBUTES | ACL_WRITE_ATTRIBUTES);

        /*
         * Ignore append permission for regular files; use write
         * permission instead.
         */
        if (!is_directory && (access_mask & ACL_APPEND_DATA)) {
                access_mask &= ~ACL_APPEND_DATA;
                access_mask |= ACL_WRITE_DATA;
        }

        denied = _acl_denies(aclp, access_mask, cred, file_uid, file_gid,
            &explicitly_denied);

        if (must_be_owner) {
                if (file_uid != cred->cr_uid)
                        denied = EPERM;
        }

        /*
         * For VEXEC, ensure that at least one execute bit is set for
         * non-directories. We have to check the mode here to stay
         * consistent with execve(2). See the test in
         * exec_check_permissions().
         */
        acl_nfs4_sync_mode_from_acl(&file_mode, aclp);
        if (!denied && !is_directory && (accmode & VEXEC) &&
            (file_mode & (S_IXUSR | S_IXGRP | S_IXOTH)) == 0)
                denied = EACCES;

        if (!denied)
                return (0);

        /*
         * Access failed.  Iff it was not denied explicitly and
         * VEXPLICIT_DENY flag was specified, allow access.
         */
        if ((accmode & VEXPLICIT_DENY) && explicitly_denied == 0)
                return (0);

        accmode &= ~VEXPLICIT_DENY;

        /*
         * No match.  Try to use privileges, if there are any.
         */
        if (is_directory) {
                if ((accmode & VEXEC) && !priv_check_cred(cred, PRIV_VFS_LOOKUP))
                        priv_granted |= VEXEC;
        } else {
                /*
                 * Ensure that at least one execute bit is on. Otherwise,
                 * a privileged user will always succeed, and we don't want
                 * this to happen unless the file really is executable.
                 */
                if ((accmode & VEXEC) && (file_mode &
                    (S_IXUSR | S_IXGRP | S_IXOTH)) != 0 &&
                    !priv_check_cred(cred, PRIV_VFS_EXEC))
                        priv_granted |= VEXEC;
        }

        if ((accmode & VREAD) && !priv_check_cred(cred, PRIV_VFS_READ))
                priv_granted |= VREAD;

        if ((accmode & (VWRITE | VAPPEND | VDELETE_CHILD)) &&
            !priv_check_cred(cred, PRIV_VFS_WRITE))
                priv_granted |= (VWRITE | VAPPEND | VDELETE_CHILD);

        if ((accmode & VADMIN_PERMS) &&
            !priv_check_cred(cred, PRIV_VFS_ADMIN))
                priv_granted |= VADMIN_PERMS;

        if ((accmode & VSTAT_PERMS) &&
            !priv_check_cred(cred, PRIV_VFS_STAT))
                priv_granted |= VSTAT_PERMS;

        if ((accmode & priv_granted) == accmode) {
                return (0);
        }

        if (accmode & (VADMIN_PERMS | VDELETE_CHILD | VDELETE))
                denied = EPERM;
        else
                denied = EACCES;

        return (denied);
}
#endif /* _KERNEL */

static int
_acl_entry_matches(struct acl_entry *entry, acl_tag_t tag, acl_perm_t perm,
    acl_entry_type_t entry_type)
{
        if (entry->ae_tag != tag)
                return (0);

        if (entry->ae_id != ACL_UNDEFINED_ID)
                return (0);

        if (entry->ae_perm != perm)
                return (0);

        if (entry->ae_entry_type != entry_type)
                return (0);

        if (entry->ae_flags != 0)
                return (0);

        return (1);
}

static struct acl_entry *
_acl_append(struct acl *aclp, acl_tag_t tag, acl_perm_t perm,
    acl_entry_type_t entry_type)
{
        struct acl_entry *entry;

        KASSERT(aclp->acl_cnt + 1 <= ACL_MAX_ENTRIES,
            ("aclp->acl_cnt + 1 <= ACL_MAX_ENTRIES"));

        entry = &(aclp->acl_entry[aclp->acl_cnt]);
        aclp->acl_cnt++;

        entry->ae_tag = tag;
        entry->ae_id = ACL_UNDEFINED_ID;
        entry->ae_perm = perm;
        entry->ae_entry_type = entry_type;
        entry->ae_flags = 0;

        return (entry);
}

static struct acl_entry *
_acl_duplicate_entry(struct acl *aclp, unsigned entry_index)
{
        unsigned i;

        KASSERT(aclp->acl_cnt + 1 <= ACL_MAX_ENTRIES,
            ("aclp->acl_cnt + 1 <= ACL_MAX_ENTRIES"));

        for (i = aclp->acl_cnt; i > entry_index; i--)
                aclp->acl_entry[i] = aclp->acl_entry[i - 1];

        aclp->acl_cnt++;

        return (&(aclp->acl_entry[entry_index + 1]));
}

static void
acl_nfs4_sync_acl_from_mode_draft(struct acl *aclp, mode_t mode,
    int file_owner_id)
{
        int meets, must_append;
        unsigned i;
        struct acl_entry *entry, *copy, *previous,
            *a1, *a2, *a3, *a4, *a5, *a6;
        mode_t amode;
        const int READ = 04;
        const int WRITE = 02;
        const int EXEC = 01;

        KASSERT(aclp->acl_cnt <= ACL_MAX_ENTRIES,
            ("aclp->acl_cnt <= ACL_MAX_ENTRIES"));

        /*
         * NFSv4 Minor Version 1, draft-ietf-nfsv4-minorversion1-03.txt
         *
         * 3.16.6.3. Applying a Mode to an Existing ACL
         */

        /*
         * 1. For each ACE:
         */
        for (i = 0; i < aclp->acl_cnt; i++) {
                entry = &(aclp->acl_entry[i]);

                /*
                 * 1.1. If the type is neither ALLOW or DENY - skip.
                 */
                if (entry->ae_entry_type != ACL_ENTRY_TYPE_ALLOW &&
                    entry->ae_entry_type != ACL_ENTRY_TYPE_DENY)
                        continue;

                /*
                 * 1.2. If ACL_ENTRY_INHERIT_ONLY is set - skip.
                 */
                if (entry->ae_flags & ACL_ENTRY_INHERIT_ONLY)
                        continue;

                /*
                 * 1.3. If ACL_ENTRY_FILE_INHERIT or ACL_ENTRY_DIRECTORY_INHERIT
                 *      are set:
                 */
                if (entry->ae_flags &
                    (ACL_ENTRY_FILE_INHERIT | ACL_ENTRY_DIRECTORY_INHERIT)) {
                        /*
                         * 1.3.1. A copy of the current ACE is made, and placed
                         *        in the ACL immediately following the current
                         *        ACE.
                         */
                        copy = _acl_duplicate_entry(aclp, i);

                        /*
                         * 1.3.2. In the first ACE, the flag
                         *        ACL_ENTRY_INHERIT_ONLY is set.
                         */
                        entry->ae_flags |= ACL_ENTRY_INHERIT_ONLY;

                        /*
                         * 1.3.3. In the second ACE, the following flags
                         *        are cleared:
                         *        ACL_ENTRY_FILE_INHERIT,
                         *        ACL_ENTRY_DIRECTORY_INHERIT,
                         *        ACL_ENTRY_NO_PROPAGATE_INHERIT.
                         */
                        copy->ae_flags &= ~(ACL_ENTRY_FILE_INHERIT |
                            ACL_ENTRY_DIRECTORY_INHERIT |
                            ACL_ENTRY_NO_PROPAGATE_INHERIT);

                        /*
                         * The algorithm continues on with the second ACE.
                         */
                        i++;
                        entry = copy;
                }

                /*
                 * 1.4. If it's owner@, group@ or everyone@ entry, clear
                 *      ACL_READ_DATA, ACL_WRITE_DATA, ACL_APPEND_DATA
                 *      and ACL_EXECUTE.  Continue to the next entry.
                 */
                if (entry->ae_tag == ACL_USER_OBJ ||
                    entry->ae_tag == ACL_GROUP_OBJ ||
                    entry->ae_tag == ACL_EVERYONE) {
                        entry->ae_perm &= ~(ACL_READ_DATA | ACL_WRITE_DATA |
                            ACL_APPEND_DATA | ACL_EXECUTE);
                        continue;
                }

                /*
                 * 1.5. Otherwise, if the "who" field did not match one
                 *      of OWNER@, GROUP@, EVERYONE@:
                 *
                 * 1.5.1. If the type is ALLOW, check the preceding ACE.
                 *        If it does not meet all of the following criteria:
                 */
                if (entry->ae_entry_type != ACL_ENTRY_TYPE_ALLOW)
                        continue;

                meets = 0;
                if (i > 0) {
                        meets = 1;
                        previous = &(aclp->acl_entry[i - 1]);

                        /*
                         * 1.5.1.1. The type field is DENY,
                         */
                        if (previous->ae_entry_type != ACL_ENTRY_TYPE_DENY)
                                meets = 0;

                        /*
                         * 1.5.1.2. The "who" field is the same as the current
                         *          ACE,
                         *
                         * 1.5.1.3. The flag bit ACE4_IDENTIFIER_GROUP
                         *          is the same as it is in the current ACE,
                         *          and no other flag bits are set,
                         */
                        if (previous->ae_id != entry->ae_id ||
                            previous->ae_tag != entry->ae_tag)
                                meets = 0;

                        if (previous->ae_flags)
                                meets = 0;

                        /*
                         * 1.5.1.4. The mask bits are a subset of the mask bits
                         *          of the current ACE, and are also subset of
                         *          the following: ACL_READ_DATA,
                         *          ACL_WRITE_DATA, ACL_APPEND_DATA, ACL_EXECUTE
                         */
                        if (previous->ae_perm & ~(entry->ae_perm))
                                meets = 0;

                        if (previous->ae_perm & ~(ACL_READ_DATA |
                            ACL_WRITE_DATA | ACL_APPEND_DATA | ACL_EXECUTE))
                                meets = 0;
                }

                if (!meets) {
                        /*
                         * Then the ACE of type DENY, with a who equal
                         * to the current ACE, flag bits equal to
                         * (<current ACE flags> & <ACE_IDENTIFIER_GROUP>)
                         * and no mask bits, is prepended.
                         */
                        previous = entry;
                        entry = _acl_duplicate_entry(aclp, i);

                        /* Adjust counter, as we've just added an entry. */
                        i++;

                        previous->ae_tag = entry->ae_tag;
                        previous->ae_id = entry->ae_id;
                        previous->ae_flags = entry->ae_flags;
                        previous->ae_perm = 0;
                        previous->ae_entry_type = ACL_ENTRY_TYPE_DENY;
                }

                /*
                 * 1.5.2. The following modifications are made to the prepended
                 *        ACE.  The intent is to mask the following ACE
                 *        to disallow ACL_READ_DATA, ACL_WRITE_DATA,
                 *        ACL_APPEND_DATA, or ACL_EXECUTE, based upon the group
                 *        permissions of the new mode.  As a special case,
                 *        if the ACE matches the current owner of the file,
                 *        the owner bits are used, rather than the group bits.
                 *        This is reflected in the algorithm below.
                 */
                amode = mode >> 3;

                /*
                 * If ACE4_IDENTIFIER_GROUP is not set, and the "who" field
                 * in ACE matches the owner of the file, we shift amode three
                 * more bits, in order to have the owner permission bits
                 * placed in the three low order bits of amode.
                 */
                if (entry->ae_tag == ACL_USER && entry->ae_id == file_owner_id)
                        amode = amode >> 3;

                if (entry->ae_perm & ACL_READ_DATA) {
                        if (amode & READ)
                                previous->ae_perm &= ~ACL_READ_DATA;
                        else
                                previous->ae_perm |= ACL_READ_DATA;
                }

                if (entry->ae_perm & ACL_WRITE_DATA) {
                        if (amode & WRITE)
                                previous->ae_perm &= ~ACL_WRITE_DATA;
                        else
                                previous->ae_perm |= ACL_WRITE_DATA;
                }

                if (entry->ae_perm & ACL_APPEND_DATA) {
                        if (amode & WRITE)
                                previous->ae_perm &= ~ACL_APPEND_DATA;
                        else
                                previous->ae_perm |= ACL_APPEND_DATA;
                }

                if (entry->ae_perm & ACL_EXECUTE) {
                        if (amode & EXEC)
                                previous->ae_perm &= ~ACL_EXECUTE;
                        else
                                previous->ae_perm |= ACL_EXECUTE;
                }

                /*
                 * 1.5.3. If ACE4_IDENTIFIER_GROUP is set in the flags
                 *        of the ALLOW ace:
                 *
                 * XXX: This point is not there in the Falkner's draft.
                 */
                if (entry->ae_tag == ACL_GROUP &&
                    entry->ae_entry_type == ACL_ENTRY_TYPE_ALLOW) {
                        mode_t extramode, ownermode;
                        extramode = (mode >> 3) & 07;
                        ownermode = mode >> 6;
                        extramode &= ~ownermode;

                        if (extramode) {
                                if (extramode & READ) {
                                        entry->ae_perm &= ~ACL_READ_DATA;
                                        previous->ae_perm &= ~ACL_READ_DATA;
                                }

                                if (extramode & WRITE) {
                                        entry->ae_perm &=
                                            ~(ACL_WRITE_DATA | ACL_APPEND_DATA);
                                        previous->ae_perm &=
                                            ~(ACL_WRITE_DATA | ACL_APPEND_DATA);
                                }

                                if (extramode & EXEC) {
                                        entry->ae_perm &= ~ACL_EXECUTE;
                                        previous->ae_perm &= ~ACL_EXECUTE;
                                }
                        }
                }
        }

        /*
         * 2. If there at least six ACEs, the final six ACEs are examined.
         *    If they are not equal to what we want, append six ACEs.
         */
        must_append = 0;
        if (aclp->acl_cnt < 6) {
                must_append = 1;
        } else {
                a6 = &(aclp->acl_entry[aclp->acl_cnt - 1]);
                a5 = &(aclp->acl_entry[aclp->acl_cnt - 2]);
                a4 = &(aclp->acl_entry[aclp->acl_cnt - 3]);
                a3 = &(aclp->acl_entry[aclp->acl_cnt - 4]);
                a2 = &(aclp->acl_entry[aclp->acl_cnt - 5]);
                a1 = &(aclp->acl_entry[aclp->acl_cnt - 6]);

                if (!_acl_entry_matches(a1, ACL_USER_OBJ, 0,
                    ACL_ENTRY_TYPE_DENY))
                        must_append = 1;
                if (!_acl_entry_matches(a2, ACL_USER_OBJ, ACL_WRITE_ACL |
                    ACL_WRITE_OWNER | ACL_WRITE_ATTRIBUTES |
                    ACL_WRITE_NAMED_ATTRS, ACL_ENTRY_TYPE_ALLOW))
                        must_append = 1;
                if (!_acl_entry_matches(a3, ACL_GROUP_OBJ, 0,
                    ACL_ENTRY_TYPE_DENY))
                        must_append = 1;
                if (!_acl_entry_matches(a4, ACL_GROUP_OBJ, 0,
                    ACL_ENTRY_TYPE_ALLOW))
                        must_append = 1;
                if (!_acl_entry_matches(a5, ACL_EVERYONE, ACL_WRITE_ACL |
                    ACL_WRITE_OWNER | ACL_WRITE_ATTRIBUTES |
                    ACL_WRITE_NAMED_ATTRS, ACL_ENTRY_TYPE_DENY))
                        must_append = 1;
                if (!_acl_entry_matches(a6, ACL_EVERYONE, ACL_READ_ACL |
                    ACL_READ_ATTRIBUTES | ACL_READ_NAMED_ATTRS |
                    ACL_SYNCHRONIZE, ACL_ENTRY_TYPE_ALLOW))
                        must_append = 1;
        }

        if (must_append) {
                KASSERT(aclp->acl_cnt + 6 <= ACL_MAX_ENTRIES,
                    ("aclp->acl_cnt <= ACL_MAX_ENTRIES"));

                a1 = _acl_append(aclp, ACL_USER_OBJ, 0, ACL_ENTRY_TYPE_DENY);
                a2 = _acl_append(aclp, ACL_USER_OBJ, ACL_WRITE_ACL |
                    ACL_WRITE_OWNER | ACL_WRITE_ATTRIBUTES |
                    ACL_WRITE_NAMED_ATTRS, ACL_ENTRY_TYPE_ALLOW);
                a3 = _acl_append(aclp, ACL_GROUP_OBJ, 0, ACL_ENTRY_TYPE_DENY);
                a4 = _acl_append(aclp, ACL_GROUP_OBJ, 0, ACL_ENTRY_TYPE_ALLOW);
                a5 = _acl_append(aclp, ACL_EVERYONE, ACL_WRITE_ACL |
                    ACL_WRITE_OWNER | ACL_WRITE_ATTRIBUTES |
                    ACL_WRITE_NAMED_ATTRS, ACL_ENTRY_TYPE_DENY);
                a6 = _acl_append(aclp, ACL_EVERYONE, ACL_READ_ACL |
                    ACL_READ_ATTRIBUTES | ACL_READ_NAMED_ATTRS |
                    ACL_SYNCHRONIZE, ACL_ENTRY_TYPE_ALLOW);

                KASSERT(a1 != NULL && a2 != NULL && a3 != NULL && a4 != NULL &&
                    a5 != NULL && a6 != NULL, ("couldn't append to ACL."));
        }

        /*
         * 3. The final six ACEs are adjusted according to the incoming mode.
         */
        if (mode & S_IRUSR)
                a2->ae_perm |= ACL_READ_DATA;
        else
                a1->ae_perm |= ACL_READ_DATA;
        if (mode & S_IWUSR)
                a2->ae_perm |= (ACL_WRITE_DATA | ACL_APPEND_DATA);
        else
                a1->ae_perm |= (ACL_WRITE_DATA | ACL_APPEND_DATA);
        if (mode & S_IXUSR)
                a2->ae_perm |= ACL_EXECUTE;
        else
                a1->ae_perm |= ACL_EXECUTE;

        if (mode & S_IRGRP)
                a4->ae_perm |= ACL_READ_DATA;
        else
                a3->ae_perm |= ACL_READ_DATA;
        if (mode & S_IWGRP)
                a4->ae_perm |= (ACL_WRITE_DATA | ACL_APPEND_DATA);
        else
                a3->ae_perm |= (ACL_WRITE_DATA | ACL_APPEND_DATA);
        if (mode & S_IXGRP)
                a4->ae_perm |= ACL_EXECUTE;
        else
                a3->ae_perm |= ACL_EXECUTE;

        if (mode & S_IROTH)
                a6->ae_perm |= ACL_READ_DATA;
        else
                a5->ae_perm |= ACL_READ_DATA;
        if (mode & S_IWOTH)
                a6->ae_perm |= (ACL_WRITE_DATA | ACL_APPEND_DATA);
        else
                a5->ae_perm |= (ACL_WRITE_DATA | ACL_APPEND_DATA);
        if (mode & S_IXOTH)
                a6->ae_perm |= ACL_EXECUTE;
        else
                a5->ae_perm |= ACL_EXECUTE;
}

#ifdef _KERNEL
void
acl_nfs4_sync_acl_from_mode(struct acl *aclp, mode_t mode,
    int file_owner_id)
{

        if (acl_nfs4_old_semantics)
                acl_nfs4_sync_acl_from_mode_draft(aclp, mode, file_owner_id);
        else
                acl_nfs4_trivial_from_mode(aclp, mode);
}
#endif /* _KERNEL */

void
acl_nfs4_sync_mode_from_acl(mode_t *_mode, const struct acl *aclp)
{
        int i;
        mode_t old_mode = *_mode, mode = 0, seen = 0;
        const struct acl_entry *entry;

        KASSERT(aclp->acl_cnt <= ACL_MAX_ENTRIES,
            ("aclp->acl_cnt <= ACL_MAX_ENTRIES"));

        /*
         * NFSv4 Minor Version 1, draft-ietf-nfsv4-minorversion1-03.txt
         *
         * 3.16.6.1. Recomputing mode upon SETATTR of ACL
         */

        for (i = 0; i < aclp->acl_cnt; i++) {
                entry = &(aclp->acl_entry[i]);

                if (entry->ae_entry_type != ACL_ENTRY_TYPE_ALLOW &&
                    entry->ae_entry_type != ACL_ENTRY_TYPE_DENY)
                        continue;

                if (entry->ae_flags & ACL_ENTRY_INHERIT_ONLY)
                        continue;

                if (entry->ae_tag == ACL_USER_OBJ) {
                        if ((entry->ae_perm & ACL_READ_DATA) &&
                            ((seen & S_IRUSR) == 0)) {
                                seen |= S_IRUSR;
                                if (entry->ae_entry_type == ACL_ENTRY_TYPE_ALLOW)
                                        mode |= S_IRUSR;
                        }
                        if ((entry->ae_perm & ACL_WRITE_DATA) &&
                             ((seen & S_IWUSR) == 0)) {
                                seen |= S_IWUSR;
                                if (entry->ae_entry_type == ACL_ENTRY_TYPE_ALLOW)
                                        mode |= S_IWUSR;
                        }
                        if ((entry->ae_perm & ACL_EXECUTE) &&
                            ((seen & S_IXUSR) == 0)) {
                                seen |= S_IXUSR;
                                if (entry->ae_entry_type == ACL_ENTRY_TYPE_ALLOW)
                                        mode |= S_IXUSR;
                        }
                } else if (entry->ae_tag == ACL_GROUP_OBJ) {
                        if ((entry->ae_perm & ACL_READ_DATA) &&
                            ((seen & S_IRGRP) == 0)) {
                                seen |= S_IRGRP;
                                if (entry->ae_entry_type == ACL_ENTRY_TYPE_ALLOW)
                                        mode |= S_IRGRP;
                        }
                        if ((entry->ae_perm & ACL_WRITE_DATA) &&
                            ((seen & S_IWGRP) == 0)) {
                                seen |= S_IWGRP;
                                if (entry->ae_entry_type == ACL_ENTRY_TYPE_ALLOW)
                                        mode |= S_IWGRP;
                        }
                        if ((entry->ae_perm & ACL_EXECUTE) &&
                            ((seen & S_IXGRP) == 0)) {
                                seen |= S_IXGRP;
                                if (entry->ae_entry_type == ACL_ENTRY_TYPE_ALLOW)
                                        mode |= S_IXGRP;
                        }
                } else if (entry->ae_tag == ACL_EVERYONE) {
                        if (entry->ae_perm & ACL_READ_DATA) {
                                if ((seen & S_IRUSR) == 0) {
                                        seen |= S_IRUSR;
                                        if (entry->ae_entry_type == ACL_ENTRY_TYPE_ALLOW)
                                                mode |= S_IRUSR;
                                }
                                if ((seen & S_IRGRP) == 0) {
                                        seen |= S_IRGRP;
                                        if (entry->ae_entry_type == ACL_ENTRY_TYPE_ALLOW)
                                                mode |= S_IRGRP;
                                }
                                if ((seen & S_IROTH) == 0) {
                                        seen |= S_IROTH;
                                        if (entry->ae_entry_type == ACL_ENTRY_TYPE_ALLOW)
                                                mode |= S_IROTH;
                                }
                        }
                        if (entry->ae_perm & ACL_WRITE_DATA) {
                                if ((seen & S_IWUSR) == 0) {
                                        seen |= S_IWUSR;
                                        if (entry->ae_entry_type == ACL_ENTRY_TYPE_ALLOW)
                                                mode |= S_IWUSR;
                                }
                                if ((seen & S_IWGRP) == 0) {
                                        seen |= S_IWGRP;
                                        if (entry->ae_entry_type == ACL_ENTRY_TYPE_ALLOW)
                                                mode |= S_IWGRP;
                                }
                                if ((seen & S_IWOTH) == 0) {
                                        seen |= S_IWOTH;
                                        if (entry->ae_entry_type == ACL_ENTRY_TYPE_ALLOW)
                                                mode |= S_IWOTH;
                                }
                        }
                        if (entry->ae_perm & ACL_EXECUTE) {
                                if ((seen & S_IXUSR) == 0) {
                                        seen |= S_IXUSR;
                                        if (entry->ae_entry_type == ACL_ENTRY_TYPE_ALLOW)
                                                mode |= S_IXUSR;
                                }
                                if ((seen & S_IXGRP) == 0) {
                                        seen |= S_IXGRP;
                                        if (entry->ae_entry_type == ACL_ENTRY_TYPE_ALLOW)
                                                mode |= S_IXGRP;
                                }
                                if ((seen & S_IXOTH) == 0) {
                                        seen |= S_IXOTH;
                                        if (entry->ae_entry_type == ACL_ENTRY_TYPE_ALLOW)
                                                mode |= S_IXOTH;
                                }
                        }
                }
        }

        *_mode = mode | (old_mode & ACL_PRESERVE_MASK);
}

#ifdef _KERNEL
/*
 * Calculate inherited ACL in a manner compatible with NFSv4 Minor Version 1,
 * draft-ietf-nfsv4-minorversion1-03.txt.
 */
static void             
acl_nfs4_compute_inherited_acl_draft(const struct acl *parent_aclp,
    struct acl *child_aclp, mode_t mode, int file_owner_id,
    int is_directory)
{
        int i, flags;
        const struct acl_entry *parent_entry;
        struct acl_entry *entry, *copy;

        KASSERT(child_aclp->acl_cnt == 0, ("child_aclp->acl_cnt == 0"));
        KASSERT(parent_aclp->acl_cnt <= ACL_MAX_ENTRIES,
            ("parent_aclp->acl_cnt <= ACL_MAX_ENTRIES"));

        /*
         * NFSv4 Minor Version 1, draft-ietf-nfsv4-minorversion1-03.txt
         *
         * 3.16.6.2. Applying the mode given to CREATE or OPEN
         *           to an inherited ACL
         */

        /*
         * 1. Form an ACL that is the concatenation of all inheritable ACEs.
         */
        for (i = 0; i < parent_aclp->acl_cnt; i++) {
                parent_entry = &(parent_aclp->acl_entry[i]);
                flags = parent_entry->ae_flags;

                /*
                 * Entry is not inheritable at all.
                 */
                if ((flags & (ACL_ENTRY_DIRECTORY_INHERIT |
                    ACL_ENTRY_FILE_INHERIT)) == 0)
                        continue;

                /*
                 * We're creating a file, but entry is not inheritable
                 * by files.
                 */
                if (!is_directory && (flags & ACL_ENTRY_FILE_INHERIT) == 0)
                        continue;

                /*
                 * Entry is inheritable only by files, but has NO_PROPAGATE
                 * flag set, and we're creating a directory, so it wouldn't
                 * propagate to any file in that directory anyway.
                 */
                if (is_directory &&
                    (flags & ACL_ENTRY_DIRECTORY_INHERIT) == 0 &&
                    (flags & ACL_ENTRY_NO_PROPAGATE_INHERIT))
                        continue;

                KASSERT(child_aclp->acl_cnt + 1 <= ACL_MAX_ENTRIES,
                    ("child_aclp->acl_cnt + 1 <= ACL_MAX_ENTRIES"));
                child_aclp->acl_entry[child_aclp->acl_cnt] = *parent_entry;
                child_aclp->acl_cnt++;
        }

        /*
         * 2. For each entry in the new ACL, adjust its flags, possibly
         *    creating two entries in place of one.
         */
        for (i = 0; i < child_aclp->acl_cnt; i++) {
                entry = &(child_aclp->acl_entry[i]);

                /*
                 * This is not in the specification, but SunOS
                 * apparently does that.
                 */
                if (((entry->ae_flags & ACL_ENTRY_NO_PROPAGATE_INHERIT) ||
                    !is_directory) &&
                    entry->ae_entry_type == ACL_ENTRY_TYPE_ALLOW)
                        entry->ae_perm &= ~(ACL_WRITE_ACL | ACL_WRITE_OWNER);

                /*
                 * 2.A. If the ACL_ENTRY_NO_PROPAGATE_INHERIT is set, or if the object
                 *      being created is not a directory, then clear the
                 *      following flags: ACL_ENTRY_NO_PROPAGATE_INHERIT,
                 *      ACL_ENTRY_FILE_INHERIT, ACL_ENTRY_DIRECTORY_INHERIT,
                 *      ACL_ENTRY_INHERIT_ONLY.
                 */
                if (entry->ae_flags & ACL_ENTRY_NO_PROPAGATE_INHERIT ||
                    !is_directory) {
                        entry->ae_flags &= ~(ACL_ENTRY_NO_PROPAGATE_INHERIT |
                        ACL_ENTRY_FILE_INHERIT | ACL_ENTRY_DIRECTORY_INHERIT |
                        ACL_ENTRY_INHERIT_ONLY);

                        /*
                         * Continue on to the next ACE.
                         */
                        continue;
                }

                /*
                 * 2.B. If the object is a directory and ACL_ENTRY_FILE_INHERIT
                 *      is set, but ACL_ENTRY_NO_PROPAGATE_INHERIT is not set, ensure
                 *      that ACL_ENTRY_INHERIT_ONLY is set.  Continue to the
                 *      next ACE.  Otherwise...
                 */
                /*
                 * XXX: Read it again and make sure what does the "otherwise"
                 *      apply to.
                 */
                if (is_directory &&
                    (entry->ae_flags & ACL_ENTRY_FILE_INHERIT) &&
                    ((entry->ae_flags & ACL_ENTRY_DIRECTORY_INHERIT) == 0)) {
                        entry->ae_flags |= ACL_ENTRY_INHERIT_ONLY;
                        continue;
                }

                /*
                 * 2.C. If the type of the ACE is neither ALLOW nor deny,
                 *      then continue.
                 */
                if (entry->ae_entry_type != ACL_ENTRY_TYPE_ALLOW &&
                    entry->ae_entry_type != ACL_ENTRY_TYPE_DENY)
                        continue;

                /*
                 * 2.D. Copy the original ACE into a second, adjacent ACE.
                 */
                copy = _acl_duplicate_entry(child_aclp, i);

                /*
                 * 2.E. On the first ACE, ensure that ACL_ENTRY_INHERIT_ONLY
                 *      is set.
                 */
                entry->ae_flags |= ACL_ENTRY_INHERIT_ONLY;

                /*
                 * 2.F. On the second ACE, clear the following flags:
                 *      ACL_ENTRY_NO_PROPAGATE_INHERIT, ACL_ENTRY_FILE_INHERIT,
                 *      ACL_ENTRY_DIRECTORY_INHERIT, ACL_ENTRY_INHERIT_ONLY.
                 */
                copy->ae_flags &= ~(ACL_ENTRY_NO_PROPAGATE_INHERIT |
                    ACL_ENTRY_FILE_INHERIT | ACL_ENTRY_DIRECTORY_INHERIT |
                    ACL_ENTRY_INHERIT_ONLY);

                /*
                 * 2.G. On the second ACE, if the type is ALLOW,
                 *      an implementation MAY clear the following
                 *      mask bits: ACL_WRITE_ACL, ACL_WRITE_OWNER.
                 */
                if (copy->ae_entry_type == ACL_ENTRY_TYPE_ALLOW)
                        copy->ae_perm &= ~(ACL_WRITE_ACL | ACL_WRITE_OWNER);

                /*
                 * Increment the counter to skip the copied entry.
                 */
                i++;
        }

        /*
         * 3. To ensure that the mode is honored, apply the algorithm describe
         *    in Section 2.16.6.3, using the mode that is to be used for file
         *    creation.
         */
        acl_nfs4_sync_acl_from_mode(child_aclp, mode, file_owner_id);
}
#endif /* _KERNEL */

/*
 * Populate the ACL with entries inherited from parent_aclp.
 */
static void             
acl_nfs4_inherit_entries(const struct acl *parent_aclp,
    struct acl *child_aclp, mode_t mode, int file_owner_id,
    int is_directory)
{
        int i, flags, tag;
        const struct acl_entry *parent_entry;
        struct acl_entry *entry;

        KASSERT(parent_aclp->acl_cnt <= ACL_MAX_ENTRIES,
            ("parent_aclp->acl_cnt <= ACL_MAX_ENTRIES"));

        for (i = 0; i < parent_aclp->acl_cnt; i++) {
                parent_entry = &(parent_aclp->acl_entry[i]);
                flags = parent_entry->ae_flags;
                tag = parent_entry->ae_tag;

                /*
                 * Don't inherit owner@, group@, or everyone@ entries.
                 */
                if (tag == ACL_USER_OBJ || tag == ACL_GROUP_OBJ ||
                    tag == ACL_EVERYONE)
                        continue;

                /*
                 * Entry is not inheritable at all.
                 */
                if ((flags & (ACL_ENTRY_DIRECTORY_INHERIT |
                    ACL_ENTRY_FILE_INHERIT)) == 0)
                        continue;

                /*
                 * We're creating a file, but entry is not inheritable
                 * by files.
                 */
                if (!is_directory && (flags & ACL_ENTRY_FILE_INHERIT) == 0)
                        continue;

                /*
                 * Entry is inheritable only by files, but has NO_PROPAGATE
                 * flag set, and we're creating a directory, so it wouldn't
                 * propagate to any file in that directory anyway.
                 */
                if (is_directory &&
                    (flags & ACL_ENTRY_DIRECTORY_INHERIT) == 0 &&
                    (flags & ACL_ENTRY_NO_PROPAGATE_INHERIT))
                        continue;

                /*
                 * Entry qualifies for being inherited.
                 */
                KASSERT(child_aclp->acl_cnt + 1 <= ACL_MAX_ENTRIES,
                    ("child_aclp->acl_cnt + 1 <= ACL_MAX_ENTRIES"));
                entry = &(child_aclp->acl_entry[child_aclp->acl_cnt]);
                *entry = *parent_entry;
                child_aclp->acl_cnt++;

                entry->ae_flags &= ~ACL_ENTRY_INHERIT_ONLY;
                entry->ae_flags |= ACL_ENTRY_INHERITED;

                /*
                 * If the type of the ACE is neither ALLOW nor DENY,
                 * then leave it as it is and proceed to the next one.
                 */
                if (entry->ae_entry_type != ACL_ENTRY_TYPE_ALLOW &&
                    entry->ae_entry_type != ACL_ENTRY_TYPE_DENY)
                        continue;

                /*
                 * If the ACL_ENTRY_NO_PROPAGATE_INHERIT is set, or if
                 * the object being created is not a directory, then clear
                 * the following flags: ACL_ENTRY_NO_PROPAGATE_INHERIT,
                 * ACL_ENTRY_FILE_INHERIT, ACL_ENTRY_DIRECTORY_INHERIT,
                 * ACL_ENTRY_INHERIT_ONLY.
                 */
                if (entry->ae_flags & ACL_ENTRY_NO_PROPAGATE_INHERIT ||
                    !is_directory) {
                        entry->ae_flags &= ~(ACL_ENTRY_NO_PROPAGATE_INHERIT |
                        ACL_ENTRY_FILE_INHERIT | ACL_ENTRY_DIRECTORY_INHERIT |
                        ACL_ENTRY_INHERIT_ONLY);
                }

                /*
                 * If the object is a directory and ACL_ENTRY_FILE_INHERIT
                 * is set, but ACL_ENTRY_DIRECTORY_INHERIT is not set, ensure
                 * that ACL_ENTRY_INHERIT_ONLY is set.
                 */
                if (is_directory &&
                    (entry->ae_flags & ACL_ENTRY_FILE_INHERIT) &&
                    ((entry->ae_flags & ACL_ENTRY_DIRECTORY_INHERIT) == 0)) {
                        entry->ae_flags |= ACL_ENTRY_INHERIT_ONLY;
                }

                if (entry->ae_entry_type == ACL_ENTRY_TYPE_ALLOW &&
                    (entry->ae_flags & ACL_ENTRY_INHERIT_ONLY) == 0) {
                        /*
                         * Some permissions must never be inherited.
                         */
                        entry->ae_perm &= ~(ACL_WRITE_ACL | ACL_WRITE_OWNER |
                            ACL_WRITE_NAMED_ATTRS | ACL_WRITE_ATTRIBUTES);

                        /*
                         * Others must be masked according to the file mode.
                         */
                        if ((mode & S_IRGRP) == 0)
                                entry->ae_perm &= ~ACL_READ_DATA;
                        if ((mode & S_IWGRP) == 0)
                                entry->ae_perm &=
                                    ~(ACL_WRITE_DATA | ACL_APPEND_DATA);
                        if ((mode & S_IXGRP) == 0)
                                entry->ae_perm &= ~ACL_EXECUTE;
                }
        }
}

/*
 * Calculate inherited ACL in a manner compatible with PSARC/2010/029.
 * It's also being used to calculate a trivial ACL, by inheriting from
 * a NULL ACL.
 */
static void             
acl_nfs4_compute_inherited_acl_psarc(const struct acl *parent_aclp,
    struct acl *aclp, mode_t mode, int file_owner_id, int is_directory)
{
        acl_perm_t user_allow_first = 0, user_deny = 0, group_deny = 0;
        acl_perm_t user_allow, group_allow, everyone_allow;

        KASSERT(aclp->acl_cnt == 0, ("aclp->acl_cnt == 0"));

        user_allow = group_allow = everyone_allow = ACL_READ_ACL |
            ACL_READ_ATTRIBUTES | ACL_READ_NAMED_ATTRS | ACL_SYNCHRONIZE;
        user_allow |= ACL_WRITE_ACL | ACL_WRITE_OWNER | ACL_WRITE_ATTRIBUTES |
            ACL_WRITE_NAMED_ATTRS;

        if (mode & S_IRUSR)
                user_allow |= ACL_READ_DATA;
        if (mode & S_IWUSR)
                user_allow |= (ACL_WRITE_DATA | ACL_APPEND_DATA);
        if (mode & S_IXUSR)
                user_allow |= ACL_EXECUTE;

        if (mode & S_IRGRP)
                group_allow |= ACL_READ_DATA;
        if (mode & S_IWGRP)
                group_allow |= (ACL_WRITE_DATA | ACL_APPEND_DATA);
        if (mode & S_IXGRP)
                group_allow |= ACL_EXECUTE;

        if (mode & S_IROTH)
                everyone_allow |= ACL_READ_DATA;
        if (mode & S_IWOTH)
                everyone_allow |= (ACL_WRITE_DATA | ACL_APPEND_DATA);
        if (mode & S_IXOTH)
                everyone_allow |= ACL_EXECUTE;

        user_deny = ((group_allow | everyone_allow) & ~user_allow);
        group_deny = everyone_allow & ~group_allow;
        user_allow_first = group_deny & ~user_deny;

        if (user_allow_first != 0)
                _acl_append(aclp, ACL_USER_OBJ, user_allow_first,
                    ACL_ENTRY_TYPE_ALLOW);
        if (user_deny != 0)
                _acl_append(aclp, ACL_USER_OBJ, user_deny,
                    ACL_ENTRY_TYPE_DENY);
        if (group_deny != 0)
                _acl_append(aclp, ACL_GROUP_OBJ, group_deny,
                    ACL_ENTRY_TYPE_DENY);

        if (parent_aclp != NULL)
                acl_nfs4_inherit_entries(parent_aclp, aclp, mode,
                    file_owner_id, is_directory);

        _acl_append(aclp, ACL_USER_OBJ, user_allow, ACL_ENTRY_TYPE_ALLOW);
        _acl_append(aclp, ACL_GROUP_OBJ, group_allow, ACL_ENTRY_TYPE_ALLOW);
        _acl_append(aclp, ACL_EVERYONE, everyone_allow, ACL_ENTRY_TYPE_ALLOW);
}

#ifdef _KERNEL
void            
acl_nfs4_compute_inherited_acl(const struct acl *parent_aclp,
    struct acl *child_aclp, mode_t mode, int file_owner_id,
    int is_directory)
{

        if (acl_nfs4_old_semantics)
                acl_nfs4_compute_inherited_acl_draft(parent_aclp, child_aclp,
                    mode, file_owner_id, is_directory);
        else
                acl_nfs4_compute_inherited_acl_psarc(parent_aclp, child_aclp,
                    mode, file_owner_id, is_directory);
}
#endif /* _KERNEL */

/*
 * Calculate trivial ACL in a manner compatible with PSARC/2010/029.
 * Note that this results in an ACL different from (but semantically
 * equal to) the "canonical six" trivial ACL computed using algorithm
 * described in draft-ietf-nfsv4-minorversion1-03.txt, 3.16.6.2.
 */
static void
acl_nfs4_trivial_from_mode(struct acl *aclp, mode_t mode)
{

        aclp->acl_cnt = 0;
        acl_nfs4_compute_inherited_acl_psarc(NULL, aclp, mode, -1, -1);
}

#ifndef _KERNEL
/*
 * This routine is used by libc to implement acl_strip_np(3)
 * and acl_is_trivial_np(3).
 */
void
acl_nfs4_trivial_from_mode_libc(struct acl *aclp, int mode, int canonical_six)
{

        aclp->acl_cnt = 0;
        if (canonical_six)
                acl_nfs4_sync_acl_from_mode_draft(aclp, mode, -1);
        else
                acl_nfs4_trivial_from_mode(aclp, mode);
}
#endif /* !_KERNEL */

#ifdef _KERNEL
static int
_acls_are_equal(const struct acl *a, const struct acl *b)
{
        int i;
        const struct acl_entry *entrya, *entryb;

        if (a->acl_cnt != b->acl_cnt)
                return (0);

        for (i = 0; i < b->acl_cnt; i++) {
                entrya = &(a->acl_entry[i]);
                entryb = &(b->acl_entry[i]);

                if (entrya->ae_tag != entryb->ae_tag ||
                    entrya->ae_id != entryb->ae_id ||
                    entrya->ae_perm != entryb->ae_perm ||
                    entrya->ae_entry_type != entryb->ae_entry_type ||
                    entrya->ae_flags != entryb->ae_flags)
                        return (0);
        }

        return (1);
}

/*
 * This routine is used to determine whether to remove extended attribute
 * that stores ACL contents.
 */
int
acl_nfs4_is_trivial(const struct acl *aclp, int file_owner_id)
{
        int trivial;
        mode_t tmpmode = 0;
        struct acl *tmpaclp;

        if (aclp->acl_cnt > 6)
                return (0);

        /*
         * Compute the mode from the ACL, then compute new ACL from that mode.
         * If the ACLs are identical, then the ACL is trivial.
         *
         * XXX: I guess there is a faster way to do this.  However, even
         *      this slow implementation significantly speeds things up
         *      for files that don't have non-trivial ACLs - it's critical
         *      for performance to not use EA when they are not needed.
         *
         * First try the PSARC/2010/029 semantics.
         */
        tmpaclp = acl_alloc(M_WAITOK | M_ZERO);
        acl_nfs4_sync_mode_from_acl(&tmpmode, aclp);
        acl_nfs4_trivial_from_mode(tmpaclp, tmpmode);
        trivial = _acls_are_equal(aclp, tmpaclp);
        if (trivial) {
                acl_free(tmpaclp);
                return (trivial);
        }

        /*
         * Check if it's a draft-ietf-nfsv4-minorversion1-03.txt trivial ACL.
         */
        tmpaclp->acl_cnt = 0;
        acl_nfs4_sync_acl_from_mode_draft(tmpaclp, tmpmode, file_owner_id);
        trivial = _acls_are_equal(aclp, tmpaclp);
        acl_free(tmpaclp);

        return (trivial);
}
#endif /* _KERNEL */

int
acl_nfs4_check(const struct acl *aclp, int is_directory)
{
        int i;
        const struct acl_entry *entry;

        /*
         * The spec doesn't seem to say anything about ACL validity.
         * It seems there is not much to do here.  There is even no need
         * to count "owner@" or "everyone@" (ACL_USER_OBJ and ACL_EVERYONE)
         * entries, as there can be several of them and that's perfectly
         * valid.  There can be none of them too.  Really.
         */

        if (aclp->acl_cnt > ACL_MAX_ENTRIES || aclp->acl_cnt <= 0)
                return (EINVAL);

        for (i = 0; i < aclp->acl_cnt; i++) {
                entry = &(aclp->acl_entry[i]);

                switch (entry->ae_tag) {
                case ACL_USER_OBJ:
                case ACL_GROUP_OBJ:
                case ACL_EVERYONE:
                        if (entry->ae_id != ACL_UNDEFINED_ID)
                                return (EINVAL);
                        break;

                case ACL_USER:
                case ACL_GROUP:
                        if (entry->ae_id == ACL_UNDEFINED_ID)
                                return (EINVAL);
                        break;

                default:
                        return (EINVAL);
                }

                if ((entry->ae_perm | ACL_NFS4_PERM_BITS) != ACL_NFS4_PERM_BITS)
                        return (EINVAL);

                /*
                 * Disallow ACL_ENTRY_TYPE_AUDIT and ACL_ENTRY_TYPE_ALARM for now.
                 */
                if (entry->ae_entry_type != ACL_ENTRY_TYPE_ALLOW &&
                    entry->ae_entry_type != ACL_ENTRY_TYPE_DENY)
                        return (EINVAL);

                if ((entry->ae_flags | ACL_FLAGS_BITS) != ACL_FLAGS_BITS)
                        return (EINVAL);

                /* Disallow unimplemented flags. */
                if (entry->ae_flags & (ACL_ENTRY_SUCCESSFUL_ACCESS |
                    ACL_ENTRY_FAILED_ACCESS))
                        return (EINVAL);

                /* Disallow flags not allowed for ordinary files. */
                if (!is_directory) {
                        if (entry->ae_flags & (ACL_ENTRY_FILE_INHERIT |
                            ACL_ENTRY_DIRECTORY_INHERIT |
                            ACL_ENTRY_NO_PROPAGATE_INHERIT | ACL_ENTRY_INHERIT_ONLY))
                                return (EINVAL);
                }
        }

        return (0);
}

#ifdef  _KERNEL
static int
acl_nfs4_modload(module_t module, int what, void *arg)
{
        int ret;

        ret = 0;

        switch (what) {
        case MOD_LOAD:
        case MOD_SHUTDOWN:
                break;

        case MOD_QUIESCE:
                /* XXX TODO */
                ret = 0;
                break;

        case MOD_UNLOAD:
                /* XXX TODO */
                ret = 0;
                break;
        default:
                ret = EINVAL;
                break;
        }

        return (ret);
}

static moduledata_t acl_nfs4_mod = {
        "acl_nfs4",
        acl_nfs4_modload,
        NULL
};

/*
 * XXX TODO: which subsystem, order?
 */
DECLARE_MODULE(acl_nfs4, acl_nfs4_mod, SI_SUB_VFS, SI_ORDER_FIRST);
MODULE_VERSION(acl_nfs4, 1);
#endif  /* _KERNEL */