kernel/syscall/access.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright (c) 1994, 2010, Oracle and/or its affiliates. All rights reserved.
  24  */
  25
  26 /*      Copyright (c) 1983, 1984, 1985, 1986, 1987, 1988, 1989 AT&T     */
  27 /*        All Rights Reserved   */
  28
  29 /*
  30  * Portions of this source code were derived from Berkeley 4.3 BSD
  31  * under license from the Regents of the University of California.
  32  */
  33
  34 #include <sys/param.h>
  35 #include <sys/isa_defs.h>
  36 #include <sys/types.h>
  37 #include <sys/sysmacros.h>
  38 #include <sys/cred_impl.h>
  39 #include <sys/systm.h>
  40 #include <sys/errno.h>
  41 #include <sys/pathname.h>
  42 #include <sys/vnode.h>
  43 #include <sys/uio.h>
  44 #include <sys/cmn_err.h>
  45 #include <sys/debug.h>
  46 #include <sys/file.h>
  47 #include <sys/fs_subr.h>
  48 #include <c2/audit.h>
  49 #include <sys/fcntl.h>
  50
  51 /*
  52  * Determine accessibility of file.
  53  */
  54
  55 #define E_OK    010     /* use effective ids */
  56 #define R_OK    004
  57 #define W_OK    002
  58 #define X_OK    001
  59
  60 static int
  61 caccess(char *fname, int fmode, vnode_t *startvp)
  62 {
  63         vnode_t *vp;
  64         cred_t *tmpcr;
  65         int error;
  66         int mode;
  67         int eok;
  68         cred_t *cr;
  69         int estale_retry = 0;
  70
  71         if (fmode & ~(E_OK|R_OK|W_OK|X_OK))
  72                 return (EINVAL);
  73
  74         mode = ((fmode & (R_OK|W_OK|X_OK)) << 6);
  75
  76         cr = CRED();
  77
  78         /* OK to use effective uid/gid, i.e., no need to crdup(CRED())? */
  79         eok = (fmode & E_OK) ||
  80             (cr->cr_uid == cr->cr_ruid && cr->cr_gid == cr->cr_rgid);
  81
  82         if (eok)
  83                 tmpcr = cr;
  84         else {
  85                 tmpcr = crdup(cr);
  86                 tmpcr->cr_uid = cr->cr_ruid;
  87                 tmpcr->cr_gid = cr->cr_rgid;
  88                 tmpcr->cr_ruid = cr->cr_uid;
  89                 tmpcr->cr_rgid = cr->cr_gid;
  90         }
  91
  92 lookup:
  93         if (error = lookupnameatcred(fname, UIO_USERSPACE, FOLLOW, NULLVPP, &vp,
  94             startvp, tmpcr)) {
  95                 if ((error == ESTALE) && fs_need_estale_retry(estale_retry++))
  96                         goto lookup;
  97                 if (!eok)
  98                         crfree(tmpcr);
  99                 return (error);
 100         }
 101
 102         if (mode) {
 103                 error = fop_access(vp, mode, 0, tmpcr, NULL);
 104                 if (error) {
 105                         if ((error == ESTALE) &&
 106                             fs_need_estale_retry(estale_retry++)) {
 107                                 VN_RELE(vp);
 108                                 goto lookup;
 109                         }
 110                 }
 111         }
 112
 113         if (!eok)
 114                 crfree(tmpcr);
 115         VN_RELE(vp);
 116         return (error);
 117 }
 118
 119 int
 120 faccessat(int fd, char *fname, int fmode, int flag)
 121 {
 122         vnode_t *startvp;
 123         int error;
 124
 125         if ((flag & ~AT_EACCESS) != 0)
 126                 return (set_errno(EINVAL));
 127
 128         if (fname == NULL)
 129                 return (set_errno(EFAULT));
 130         if ((error = fgetstartvp(fd, fname, &startvp)) != 0)
 131                 return (set_errno(error));
 132         if (AU_AUDITING() && startvp != NULL)
 133                 audit_setfsat_path(1);
 134
 135         /* Do not allow E_OK unless AT_EACCESS flag is set */
 136         fmode &= ~E_OK;
 137         if (flag & AT_EACCESS)
 138                 fmode |= E_OK;
 139
 140         error = caccess(fname, fmode, startvp);
 141         if (startvp != NULL)
 142                 VN_RELE(startvp);
 143         if (error)
 144                 return (set_errno(error));
 145         return (0);
 146 }