1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
|
/* euidaccess-stat -- check if effective user id can access lstat'd file
This function is probably useful only for choosing whether to issue
a prompt in an implementation of POSIX-specified rm.
Copyright (C) 2005-2006, 2009-2011 Free Software Foundation, Inc.
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>. */
/* Adapted for use in GNU remove.c by Jim Meyering. */
#include <config.h>
#include "euidaccess-stat.h"
#include <unistd.h>
#include "group-member.h"
#include "stat-macros.h"
/* Return true if the current user has permission of type MODE
on the file from which stat buffer *ST was obtained, ignoring
ACLs, attributes, `read-only'ness, etc...
Otherwise, return false.
Like the reentrant version of euidaccess, but starting with
a stat buffer rather than a file name. Hence, this function
never calls access or accessx, and doesn't take into account
whether the file has ACLs or other attributes, or resides on
a read-only file system. */
bool
euidaccess_stat (struct stat const *st, int mode)
{
uid_t euid;
unsigned int granted;
/* Convert the mode to traditional form, clearing any bogus bits. */
if (R_OK == 4 && W_OK == 2 && X_OK == 1 && F_OK == 0)
mode &= 7;
else
mode = ((mode & R_OK ? 4 : 0)
+ (mode & W_OK ? 2 : 0)
+ (mode & X_OK ? 1 : 0));
if (mode == 0)
return true; /* The file exists. */
euid = geteuid ();
/* The super-user can read and write any file, and execute any file
that anyone can execute. */
if (euid == 0 && ((mode & X_OK) == 0
|| (st->st_mode & (S_IXUSR | S_IXGRP | S_IXOTH))))
return true;
/* Convert the file's permission bits to traditional form. */
if ( S_IRUSR == (4 << 6)
&& S_IWUSR == (2 << 6)
&& S_IXUSR == (1 << 6)
&& S_IRGRP == (4 << 3)
&& S_IWGRP == (2 << 3)
&& S_IXGRP == (1 << 3)
&& S_IROTH == (4 << 0)
&& S_IWOTH == (2 << 0)
&& S_IXOTH == (1 << 0))
granted = st->st_mode;
else
granted = ( (st->st_mode & S_IRUSR ? 4 << 6 : 0)
+ (st->st_mode & S_IWUSR ? 2 << 6 : 0)
+ (st->st_mode & S_IXUSR ? 1 << 6 : 0)
+ (st->st_mode & S_IRGRP ? 4 << 3 : 0)
+ (st->st_mode & S_IWGRP ? 2 << 3 : 0)
+ (st->st_mode & S_IXGRP ? 1 << 3 : 0)
+ (st->st_mode & S_IROTH ? 4 << 0 : 0)
+ (st->st_mode & S_IWOTH ? 2 << 0 : 0)
+ (st->st_mode & S_IXOTH ? 1 << 0 : 0));
if (euid == st->st_uid)
granted >>= 6;
else
{
gid_t egid = getegid ();
if (egid == st->st_gid || group_member (st->st_gid))
granted >>= 3;
}
if ((mode & ~granted) == 0)
return true;
return false;
}
#ifdef TEST
# include <errno.h>
# include <stdio.h>
# include <stdlib.h>
# include "error.h"
# define _(msg) msg
char *program_name;
int
main (int argc, char **argv)
{
char *file;
int mode;
bool ok;
struct stat st;
program_name = argv[0];
if (argc < 3)
abort ();
file = argv[1];
mode = atoi (argv[2]);
if (lstat (file, &st) != 0)
error (EXIT_FAILURE, errno, _("cannot stat %s"), file);
ok = euidaccess_stat (&st, mode);
printf ("%s: %s\n", file, ok ? "y" : "n");
return 0;
}
#endif
|
