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
136
137
138
139
140
141
142
143
144
145
|
/*
* canonicalize.c -- canonicalize pathname by removing symlinks
*
* This file may be distributed under the terms of the
* GNU Lesser General Public License.
*
* Copyright (C) 2009-2013 Karel Zak <kzak@redhat.com>
*/
#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <unistd.h>
#include <errno.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include "canonicalize.h"
/*
* Converts private "dm-N" names to "/dev/mapper/<name>"
*
* Since 2.6.29 (patch 784aae735d9b0bba3f8b9faef4c8b30df3bf0128) kernel sysfs
* provides the real DM device names in /sys/block/<ptname>/dm/name
*/
char *canonicalize_dm_name(const char *ptname)
{
FILE *f;
size_t sz;
char path[256], name[256], *res = NULL;
if (!ptname || !*ptname)
return NULL;
snprintf(path, sizeof(path), "/sys/block/%s/dm/name", ptname);
if (!(f = fopen(path, "r" UL_CLOEXECSTR)))
return NULL;
/* read "<name>\n" from sysfs */
if (fgets(name, sizeof(name), f) && (sz = strlen(name)) > 1) {
name[sz - 1] = '\0';
snprintf(path, sizeof(path), "/dev/mapper/%s", name);
if (access(path, F_OK) == 0)
res = strdup(path);
}
fclose(f);
return res;
}
static int is_dm_devname(char *canonical, char **name)
{
struct stat sb;
char *p = strrchr(canonical, '/');
*name = NULL;
if (!p
|| strncmp(p, "/dm-", 4) != 0
|| !isdigit(*(p + 4))
|| stat(canonical, &sb) != 0
|| !S_ISBLK(sb.st_mode))
return 0;
*name = p + 1;
return 1;
}
char *canonicalize_path(const char *path)
{
char *canonical, *dmname;
if (!path || !*path)
return NULL;
canonical = realpath(path, NULL);
if (!canonical)
return strdup(path);
if (is_dm_devname(canonical, &dmname)) {
char *dm = canonicalize_dm_name(dmname);
if (dm) {
free(canonical);
return dm;
}
}
return canonical;
}
char *canonicalize_path_restricted(const char *path)
{
char *canonical, *dmname;
int errsv;
uid_t euid;
gid_t egid;
if (!path || !*path)
return NULL;
euid = geteuid();
egid = getegid();
/* drop permissions */
if (setegid(getgid()) < 0 || seteuid(getuid()) < 0)
return NULL;
errsv = errno = 0;
canonical = realpath(path, NULL);
if (!canonical)
errsv = errno;
else if (is_dm_devname(canonical, &dmname)) {
char *dm = canonicalize_dm_name(dmname);
if (dm) {
free(canonical);
canonical = dm;
}
}
/* restore */
if (setegid(egid) < 0 || seteuid(euid) < 0) {
free(canonical);
return NULL;
}
errno = errsv;
return canonical;
}
#ifdef TEST_PROGRAM_CANONICALIZE
int main(int argc, char **argv)
{
if (argc < 2) {
fprintf(stderr, "usage: %s <device>\n", argv[0]);
exit(EXIT_FAILURE);
}
fprintf(stdout, "orig: %s\n", argv[1]);
fprintf(stdout, "real: %s\n", canonicalize_path(argv[1]));
exit(EXIT_SUCCESS);
}
#endif
|
