common/syscall/access.c

	access.c revision 005d3feb53a9a10272d4a24b03991575d6a9bcb3
/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*
 * Copyright 2010 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*  Copyright (c) 1983, 1984, 1985, 1986, 1987, 1988, 1989 AT&T */
/*    All Rights Reserved   */

/*
 * Portions of this source code were derived from Berkeley 4.3 BSD
 * under license from the Regents of the University of California.
 */

#include <sys/param.h>
#include <sys/isa_defs.h>
#include <sys/types.h>
#include <sys/sysmacros.h>
#include <sys/cred_impl.h>
#include <sys/systm.h>
#include <sys/errno.h>
#include <sys/pathname.h>
#include <sys/vnode.h>
#include <sys/uio.h>
#include <sys/cmn_err.h>
#include <sys/debug.h>
#include <sys/file.h>
#include <fs/fs_subr.h>
#include <c2/audit.h>
#include <sys/fcntl.h>

/*
 * Determine accessibility of file.
 */

#define E_OK    010 /* use effective ids */
#define R_OK    004
#define W_OK    002
#define X_OK    001

static int
caccess(char *fname, int fmode, vnode_t *startvp)
{
    vnode_t *vp;
    cred_t *tmpcr;
    int error;
    int mode;
    int eok;
    cred_t *cr;
    int estale_retry = 0;

    if (fmode & ~(E_OK|R_OK|W_OK|X_OK))
        return (set_errno(EINVAL));

    mode = ((fmode & (R_OK|W_OK|X_OK)) << 6);

    cr = CRED();

    /* OK to use effective uid/gid, i.e., no need to crdup(CRED())? */
    eok = (fmode & E_OK) ||
        (cr->cr_uid == cr->cr_ruid && cr->cr_gid == cr->cr_rgid);

    if (eok)
        tmpcr = cr;
    else {
        tmpcr = crdup(cr);
        tmpcr->cr_uid = cr->cr_ruid;
        tmpcr->cr_gid = cr->cr_rgid;
        tmpcr->cr_ruid = cr->cr_uid;
        tmpcr->cr_rgid = cr->cr_gid;
    }

lookup:
    if (error = lookupnameatcred(fname, UIO_USERSPACE, FOLLOW, NULLVPP, &vp,
        startvp, tmpcr)) {
        if ((error == ESTALE) && fs_need_estale_retry(estale_retry++))
            goto lookup;
        if (!eok)
            crfree(tmpcr);
        return (set_errno(error));
    }

    if (mode) {
        error = VOP_ACCESS(vp, mode, 0, tmpcr, NULL);
        if (error) {
            if ((error == ESTALE) &&
                fs_need_estale_retry(estale_retry++)) {
                VN_RELE(vp);
                goto lookup;
            }
            (void) set_errno(error);
        }
    }

    if (!eok)
        crfree(tmpcr);
    VN_RELE(vp);
    return (error);
}

int
faccessat(int fd, char *fname, int fmode, int flag)
{
    file_t *dirfp;
    vnode_t *dirvp;
    int error;
    char startchar;

    if (fd == AT_FDCWD && fname == NULL)
        return (set_errno(EFAULT));

    if ((flag & ~AT_EACCESS) != 0)
        return (set_errno(EINVAL));

    if (fname != NULL) {
        if (copyin(fname, &startchar, sizeof (char)))
            return (set_errno(EFAULT));
    } else
        startchar = '\0';

    if (fd == AT_FDCWD) {
        dirvp = NULL;
    } else {
        if (startchar != '/') {
            if ((dirfp = getf(fd)) == NULL) {
                return (set_errno(EBADF));
            }
            dirvp = dirfp->f_vnode;
            VN_HOLD(dirvp);
            releasef(fd);
        } else {
            dirvp = NULL;
        }
    }

    if (AU_AUDITING())
        audit_setfsat_path(1);

    /* Do not allow E_OK unless AT_EACCESS flag is set */
    fmode &= ~E_OK;
    if (flag & AT_EACCESS)
        fmode |= E_OK;

    error = caccess(fname, fmode, dirvp);
    if (dirvp != NULL)
        VN_RELE(dirvp);

    return (error);
}

int
access(char *fname, int fmode)
{
    return (faccessat(AT_FDCWD, fname, fmode, 0));
}