1 /***********************************************************************
2 *                                                                      *
3 *               This software is part of the ast package               *
4 *          Copyright (c) 1985-2011 AT&T Intellectual Property          *
5 *                      and is licensed under the                       *
6 *                 Eclipse Public License, Version 1.0                  *
7 *                    by AT&T Intellectual Property                     *
8 *                                                                      *
9 *                A copy of the License is available at                 *
10 *          http://www.eclipse.org/org/documents/epl-v10.html           *
11 *         (with md5 checksum b35adb5213ca9657e911e9befb180842)         *
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
same(const char * a,const char * b)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
ispreroot(const char * dir)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
72