usr.sbin/sysvipcd/perm.c

   1 /*
   2  * Copyright (c) 2013 Larisa Grigore <larisagrigore@gmail.com>.
   3  * All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  * 3. All advertising materials mentioning features or use of this software
  14  *    must display the following acknowledgement:
  15  *      This product includes software developed by Herb Peyerl.
  16  * 4. The name of Herb Peyerl may not be used to endorse or promote products
  17  *    derived from this software without specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  20  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  21  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  22  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  23  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  24  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  25  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  26  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  27  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  28  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  29  */
  30
  31 #include <unistd.h>
  32
  33 #include "perm.h"
  34 #include <errno.h>
  35
  36 static int
  37 is_root(struct cmsgcred *cred) {
  38         return (cred->cmcred_euid == 0);
  39 }
  40
  41 static int
  42 is_grpmember(gid_t gid, struct cmsgcred *cred) {
  43         int n;
  44
  45         if (cred->cmcred_gid == gid)
  46                 return (1);
  47
  48         for (n = 0 ; n < cred->cmcred_ngroups ; n++) {
  49                 if (cred->cmcred_groups[n] == gid)
  50                         return (1);
  51         }
  52
  53         return (0);
  54 }
  55
  56 int
  57 ipcperm(struct cmsgcred *cred, struct ipc_perm *perm, int mode) {
  58         if (cred == NULL)
  59                 return (0);
  60
  61         if (cred->cmcred_euid != perm->cuid
  62                         && cred->cmcred_euid != perm->uid) {
  63                 /* In order to modify control info the caller must be
  64                  * owner, creator or privileged.
  65                  */
  66                 if (mode & IPC_M)
  67                         return (is_root(cred) ? 0 : EACCES);
  68
  69                 /* Check for group match. */
  70                 mode >>= 3;
  71                 if (!is_grpmember(perm->gid, cred) &&
  72                                 !is_grpmember(perm->cgid, cred))
  73                         mode >>= 3;
  74         }
  75
  76         if (mode & IPC_M)
  77                 return (0);
  78
  79         if ((mode & perm->mode) == mode)
  80                 return (0);
  81
  82         if (is_root(cred))
  83                 return (0);
  84
  85         return (EACCES);
  86 }