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7c673cae FG |
1 | /* |
2 | * canonicalize.c -- canonicalize pathname by removing symlinks | |
3 | * Copyright (C) 1993 Rick Sladkey <jrs@world.std.com> | |
4 | * | |
5 | * This program is free software; you can redistribute it and/or modify | |
6 | * it under the terms of the GNU Library Public License as published by | |
7 | * the Free Software Foundation; either version 2, or (at your option) | |
8 | * any later version. | |
9 | * | |
10 | * This program is distributed in the hope that it will be useful, | |
11 | * but WITHOUT ANY WARRANTY; without even the implied warranty of | |
12 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the | |
13 | * GNU Library Public License for more details. | |
14 | * | |
15 | */ | |
16 | ||
17 | /* | |
18 | * This routine is part of libc. We include it nevertheless, | |
19 | * since the libc version has some security flaws. | |
20 | * | |
21 | * TODO: use canonicalize_file_name() when exist in glibc | |
22 | */ | |
23 | #include <stdio.h> | |
24 | #include <string.h> | |
25 | #include <ctype.h> | |
26 | #include <unistd.h> | |
27 | #include <errno.h> | |
28 | #include <stdlib.h> | |
29 | #include <limits.h> | |
30 | ||
31 | #ifndef MAXSYMLINKS | |
32 | # define MAXSYMLINKS 256 | |
33 | #endif | |
34 | ||
35 | static char * | |
36 | myrealpath(const char *path, char *resolved_path, int maxreslth) { | |
37 | int readlinks = 0; | |
38 | char *npath; | |
39 | char *link_path; | |
40 | int n; | |
41 | char *buf = NULL; | |
42 | ||
43 | npath = resolved_path; | |
44 | ||
45 | /* If it's a relative pathname use getcwd for starters. */ | |
46 | if (*path != '/') { | |
47 | if (!getcwd(npath, maxreslth-2)) | |
48 | return NULL; | |
49 | npath += strlen(npath); | |
50 | if (npath[-1] != '/') | |
51 | *npath++ = '/'; | |
52 | } else { | |
53 | *npath++ = '/'; | |
54 | path++; | |
55 | } | |
56 | ||
57 | /* Expand each slash-separated pathname component. */ | |
58 | link_path = malloc(PATH_MAX+1); | |
59 | if (!link_path) | |
60 | return NULL; | |
61 | while (*path != '\0') { | |
62 | /* Ignore stray "/" */ | |
63 | if (*path == '/') { | |
64 | path++; | |
65 | continue; | |
66 | } | |
67 | if (*path == '.' && (path[1] == '\0' || path[1] == '/')) { | |
68 | /* Ignore "." */ | |
69 | path++; | |
70 | continue; | |
71 | } | |
72 | if (*path == '.' && path[1] == '.' && | |
73 | (path[2] == '\0' || path[2] == '/')) { | |
74 | /* Backup for ".." */ | |
75 | path += 2; | |
76 | while (npath > resolved_path+1 && | |
77 | (--npath)[-1] != '/') | |
78 | ; | |
79 | continue; | |
80 | } | |
81 | /* Safely copy the next pathname component. */ | |
82 | while (*path != '\0' && *path != '/') { | |
83 | if (npath-resolved_path > maxreslth-2) { | |
84 | errno = ENAMETOOLONG; | |
85 | goto err; | |
86 | } | |
87 | *npath++ = *path++; | |
88 | } | |
89 | ||
90 | /* Protect against infinite loops. */ | |
91 | if (readlinks++ > MAXSYMLINKS) { | |
92 | errno = ELOOP; | |
93 | goto err; | |
94 | } | |
95 | ||
96 | /* See if last pathname component is a symlink. */ | |
97 | *npath = '\0'; | |
98 | ||
99 | n = readlink(resolved_path, link_path, PATH_MAX); | |
100 | if (n < 0) { | |
101 | /* EINVAL means the file exists but isn't a symlink. */ | |
102 | if (errno != EINVAL) | |
103 | goto err; | |
104 | } else { | |
105 | int m; | |
106 | char *newbuf; | |
107 | ||
108 | /* Note: readlink doesn't add the null byte. */ | |
109 | link_path[n] = '\0'; | |
110 | if (*link_path == '/') | |
111 | /* Start over for an absolute symlink. */ | |
112 | npath = resolved_path; | |
113 | else | |
114 | /* Otherwise back up over this component. */ | |
115 | while (*(--npath) != '/') | |
116 | ; | |
117 | ||
118 | /* Insert symlink contents into path. */ | |
119 | m = strlen(path); | |
120 | newbuf = malloc(m + n + 1); | |
121 | if (!newbuf) | |
122 | goto err; | |
123 | memcpy(newbuf, link_path, n); | |
124 | memcpy(newbuf + n, path, m + 1); | |
125 | free(buf); | |
126 | path = buf = newbuf; | |
127 | } | |
128 | *npath++ = '/'; | |
129 | } | |
130 | /* Delete trailing slash but don't whomp a lone slash. */ | |
131 | if (npath != resolved_path+1 && npath[-1] == '/') | |
132 | npath--; | |
133 | /* Make sure it's null terminated. */ | |
134 | *npath = '\0'; | |
135 | ||
136 | free(link_path); | |
137 | free(buf); | |
138 | return resolved_path; | |
139 | ||
140 | err: | |
141 | free(link_path); | |
142 | free(buf); | |
143 | return NULL; | |
144 | } | |
145 | ||
146 | /* | |
147 | * Converts private "dm-N" names to "/dev/mapper/<name>" | |
148 | * | |
149 | * Since 2.6.29 (patch 784aae735d9b0bba3f8b9faef4c8b30df3bf0128) kernel sysfs | |
150 | * provides the real DM device names in /sys/block/<ptname>/dm/name | |
151 | */ | |
152 | char * | |
153 | canonicalize_dm_name(const char *ptname) | |
154 | { | |
155 | FILE *f; | |
156 | size_t sz; | |
157 | char path[256], name[256], *res = NULL; | |
158 | ||
159 | snprintf(path, sizeof(path), "/sys/block/%s/dm/name", ptname); | |
160 | if (!(f = fopen(path, "r"))) | |
161 | return NULL; | |
162 | ||
163 | /* read "<name>\n" from sysfs */ | |
164 | if (fgets(name, sizeof(name), f) && (sz = strlen(name)) > 1) { | |
165 | name[sz - 1] = '\0'; | |
166 | snprintf(path, sizeof(path), "/dev/mapper/%s", name); | |
167 | res = strdup(path); | |
168 | } | |
169 | fclose(f); | |
170 | return res; | |
171 | } | |
172 | ||
173 | char * | |
174 | canonicalize_path(const char *path) | |
175 | { | |
176 | char *canonical; | |
177 | char *p; | |
178 | ||
179 | if (path == NULL) | |
180 | return NULL; | |
181 | ||
182 | canonical = malloc(PATH_MAX+2); | |
183 | if (!canonical) | |
184 | return NULL; | |
185 | if (!myrealpath(path, canonical, PATH_MAX+1)) { | |
186 | free(canonical); | |
187 | return strdup(path); | |
188 | } | |
189 | ||
190 | ||
191 | p = strrchr(canonical, '/'); | |
192 | if (p && strncmp(p, "/dm-", 4) == 0 && isdigit(*(p + 4))) { | |
193 | p = canonicalize_dm_name(p+1); | |
194 | if (p) { | |
195 | free(canonical); | |
196 | return p; | |
197 | } | |
198 | } | |
199 | ||
200 | return canonical; | |
201 | } | |
202 | ||
203 |