bsd/kern/sysv_ipc.c

   1 /*
   2  * Copyright (c) 2000 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28 /*      $NetBSD: sysv_ipc.c,v 1.7 1994/06/29 06:33:11 cgd Exp $ */
  29
  30 /*
  31  * Copyright (c) 1994 Herb Peyerl <hpeyerl@novatel.ca>
  32  * All rights reserved.
  33  *
  34  * Redistribution and use in source and binary forms, with or without
  35  * modification, are permitted provided that the following conditions
  36  * are met:
  37  * 1. Redistributions of source code must retain the above copyright
  38  *    notice, this list of conditions and the following disclaimer.
  39  * 2. Redistributions in binary form must reproduce the above copyright
  40  *    notice, this list of conditions and the following disclaimer in the
  41  *    documentation and/or other materials provided with the distribution.
  42  * 3. All advertising materials mentioning features or use of this software
  43  *    must display the following acknowledgement:
  44  *      This product includes software developed by Herb Peyerl.
  45  * 4. The name of Herb Peyerl may not be used to endorse or promote products
  46  *    derived from this software without specific prior written permission.
  47  *
  48  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  49  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  50  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  51  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  52  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  53  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  54  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  55  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  56  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  57  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  58  */
  59
  60
  61 #include <sys/param.h>
  62 #include <sys/ipc.h>
  63 #include <sys/stat.h>   /* mode constants */
  64 #include <sys/ucred.h>
  65 #include <sys/kauth.h>
  66
  67
  68 /*
  69  * Check for ipc permission
  70  */
  71
  72
  73 /*
  74  * ipc_perm
  75  *
  76  *      perm->mode                      mode of the object
  77  *      mode                            mode bits we want to test
  78  *
  79  * Returns:     0                       Success
  80  *              EPERM
  81  *              EACCES
  82  *
  83  * Notes:       The IPC_M bit is special, in that it may only be granted to
  84  *              root, the creating user, or the owning user.
  85  *
  86  *              This code does not use posix_cred_access() because of the
  87  *              need to check both creator and owner separately when we are
  88  *              considering a rights grant.  Because of this, we need to do
  89  *              two evaluations when the values are inequal, which can lead
  90  *              us to defeat the callout avoidance optimization.  So we do
  91  *              the work here, inline.  This is less than optimal for any
  92  *              future work involving opacity of of POSIX credentials.
  93  *
  94  *              Setting up the mode_owner / mode_group / mode_world implicitly
  95  *              masks the IPC_M bit off.  This is intentional.
  96  *
  97  *              See the posix_cred_access() implementation for algorithm
  98  *              information.
  99  */
 100 int
 101 ipcperm(kauth_cred_t cred, struct ipc_perm *perm, int mode_req)
 102 {
 103         uid_t   uid = kauth_cred_getuid(cred);  /* avoid multiple calls */
 104         int     want_mod_controlinfo = (mode_req & IPC_M);
 105         int     is_member;
 106         mode_t  mode_owner = (perm->mode & S_IRWXU);
 107         mode_t  mode_group = (mode_t)((perm->mode & S_IRWXG) << 3);
 108         mode_t  mode_world = (mode_t)((perm->mode & S_IRWXO) << 6);
 109
 110         /* Grant all rights to super user */
 111         if (!suser(cred, (u_short *)NULL)) {
 112                 return 0;
 113         }
 114
 115         /* Grant or deny rights based on ownership */
 116         if (uid == perm->cuid || uid == perm->uid) {
 117                 if (want_mod_controlinfo) {
 118                         return 0;
 119                 }
 120
 121                 return (mode_req & mode_owner) == mode_req ? 0 : EACCES;
 122         } else {
 123                 /* everyone else who wants to modify control info is denied */
 124                 if (want_mod_controlinfo) {
 125                         return EPERM;
 126                 }
 127         }
 128
 129         /*
 130          * Combined group and world rights check, if no owner rights; positive
 131          * asssertion of gid/cgid equality avoids an extra callout in the
 132          * common case.
 133          */
 134         if ((mode_req & mode_group & mode_world) == mode_req) {
 135                 return 0;
 136         } else {
 137                 if ((mode_req & mode_group) != mode_req) {
 138                         if ((!kauth_cred_ismember_gid(cred, perm->gid, &is_member) && is_member) &&
 139                             ((perm->gid == perm->cgid) ||
 140                             (!kauth_cred_ismember_gid(cred, perm->cgid, &is_member) && is_member))) {
 141                                 return EACCES;
 142                         } else {
 143                                 if ((mode_req & mode_world) != mode_req) {
 144                                         return EACCES;
 145                                 } else {
 146                                         return 0;
 147                                 }
 148                         }
 149                 } else {
 150                         if ((!kauth_cred_ismember_gid(cred, perm->gid, &is_member) && is_member) ||
 151                             ((perm->gid != perm->cgid) &&
 152                             (!kauth_cred_ismember_gid(cred, perm->cgid, &is_member) && is_member))) {
 153                                 return 0;
 154                         } else {
 155                                 if ((mode_req & mode_world) != mode_req) {
 156                                         return EACCES;
 157                                 } else {
 158                                         return 0;
 159                                 }
 160                         }
 161                 }
 162         }
 163 }