usr/src/lib/libast/common/preroot/ispreroot.c

   1 /***********************************************************************
   2 *                                                                      *
   3 *               This software is part of the ast package               *
   4 *          Copyright (c) 1985-2010 AT&T Intellectual Property          *
   5 *                      and is licensed under the                       *
   6 *                  Common Public License, Version 1.0                  *
   7 *                    by AT&T Intellectual Property                     *
   8 *                                                                      *
   9 *                A copy of the License is available at                 *
  10 *            http://www.opensource.org/licenses/cpl1.0.txt             *
  11 *         (with md5 checksum 059e8cd6165cb4c31e351f2b69388fd9)         *
  12 *                                                                      *
  13 *              Information and Software Systems Research               *
  14 *                            AT&T Research                             *
  15 *                           Florham Park NJ                            *
  16 *                                                                      *
  17 *                 Glenn Fowler <gsf@research.att.com>                  *
  18 *                  David Korn <dgk@research.att.com>                   *
  19 *                   Phong Vo <kpv@research.att.com>                    *
  20 *                                                                      *
  21 ***********************************************************************/
  22 #pragma prototyped
  23 /*
  24  * AT&T Bell Laboratories
  25  * return 1 if dir [any dir] is the preroot
  26  */
  27
  28 #include <ast.h>
  29 #include <preroot.h>
  30
  31 #if FS_PREROOT
  32
  33 #include <ls.h>
  34
  35 /*
  36  * return 1 if files a and b are the same under preroot
  37  *
  38  * NOTE: the kernel disables preroot for set-uid processes
  39  */
  40
  41 static int
  42 same(const char* a, const char* b)
  43 {
  44         int             i;
  45         int             euid;
  46         int             ruid;
  47
  48         struct stat     ast;
  49         struct stat     bst;
  50
  51         if ((ruid = getuid()) != (euid = geteuid())) setuid(ruid);
  52         i = !stat(a, &ast) && !stat(b, &bst) && ast.st_dev == bst.st_dev && ast.st_ino == bst.st_ino;
  53         if (ruid != euid) setuid(euid);
  54         return(i);
  55 }
  56
  57 int
  58 ispreroot(const char* dir)
  59 {
  60         static int      prerooted = -1;
  61
  62         if (dir) return(same("/", dir));
  63         if (prerooted < 0) prerooted = !same("/", PR_REAL);
  64         return(prerooted);
  65 }
  66
  67 #else
  68
  69 NoN(ispreroot)
  70
  71 #endif