1 /* Return the canonical absolute name of a given file.
2 Copyright (C) 1996-2020 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 This program is free software: you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published by
7 the Free Software Foundation; either version 3 of the License, or
8 (at your option) 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 General Public License for more details.
14
15 You should have received a copy of the GNU General Public License
16 along with this program. If not, see <https://www.gnu.org/licenses/>. */
17
18 #ifndef _LIBC
19 /* Don't use __attribute__ __nonnull__ in this compilation unit. Otherwise gcc
20 optimizes away the name == NULL test below. */
21 # define _GL_ARG_NONNULL(params)
22
23 # define _GL_USE_STDLIB_ALLOC 1
24 # include <config.h>
25 #endif
26
27 #if !HAVE_CANONICALIZE_FILE_NAME || !FUNC_REALPATH_WORKS || defined _LIBC
28
29 /* Specification. */
30 #include <stdlib.h>
31
32 #include <alloca.h>
33 #include <string.h>
34 #include <unistd.h>
35 #include <limits.h>
36 #if HAVE_SYS_PARAM_H || defined _LIBC
37 # include <sys/param.h>
38 #endif
39 #include <sys/stat.h>
40 #include <errno.h>
41 #include <stddef.h>
42
43 #ifdef _LIBC
44 # include <shlib-compat.h>
45 #else
46 # define SHLIB_COMPAT(lib, introduced, obsoleted) 0
47 # define versioned_symbol(lib, local, symbol, version) extern int dummy
48 # define compat_symbol(lib, local, symbol, version)
49 # define weak_alias(local, symbol)
50 # define __canonicalize_file_name canonicalize_file_name
51 # define __realpath realpath
52 # include "pathmax.h"
53 # include "malloca.h"
54 # include "filename.h"
55 # if HAVE_GETCWD
56 # if IN_RELOCWRAPPER
57 /* When building the relocatable program wrapper, use the system's getcwd
58 function, not the gnulib override, otherwise we would get a link error.
59 */
60 # undef getcwd
61 # endif
62 # if defined VMS && !defined getcwd
63 /* We want the directory in Unix syntax, not in VMS syntax.
64 The gnulib override of 'getcwd' takes 2 arguments; the original VMS
65 'getcwd' takes 3 arguments. */
66 # define __getcwd(buf, max) getcwd (buf, max, 0)
67 # else
68 # define __getcwd getcwd
69 # endif
70 # else
71 # define __getcwd(buf, max) getwd (buf)
72 # endif
73 # define __readlink readlink
74 # define __set_errno(e) errno = (e)
75 # ifndef MAXSYMLINKS
76 # ifdef SYMLOOP_MAX
77 # define MAXSYMLINKS SYMLOOP_MAX
78 # else
79 # define MAXSYMLINKS 20
80 # endif
81 # endif
82 #endif
83
84 #ifndef DOUBLE_SLASH_IS_DISTINCT_ROOT
85 # define DOUBLE_SLASH_IS_DISTINCT_ROOT 0
86 #endif
87
88 /* Define this independently so that stdint.h is not a prerequisite. */
89 #ifndef SIZE_MAX
90 # define SIZE_MAX ((size_t) -1)
91 #endif
92
93 #if !FUNC_REALPATH_WORKS || defined _LIBC
94
95 static void
alloc_failed(void)96 alloc_failed (void)
97 {
98 #if defined _WIN32 && ! defined __CYGWIN__
99 /* Avoid errno problem without using the malloc or realloc modules; see:
100 https://lists.gnu.org/r/bug-gnulib/2016-08/msg00025.html */
101 errno = ENOMEM;
102 #endif
103 }
104
105 /* Return the canonical absolute name of file NAME. A canonical name
106 does not contain any ".", ".." components nor any repeated path
107 separators ('/') or symlinks. All path components must exist. If
108 RESOLVED is null, the result is malloc'd; otherwise, if the
109 canonical name is PATH_MAX chars or more, returns null with 'errno'
110 set to ENAMETOOLONG; if the name fits in fewer than PATH_MAX chars,
111 returns the name in RESOLVED. If the name cannot be resolved and
112 RESOLVED is non-NULL, it contains the path of the first component
113 that cannot be resolved. If the path can be resolved, RESOLVED
114 holds the same value as the value returned. */
115
116 char *
__realpath(const char * name,char * resolved)117 __realpath (const char *name, char *resolved)
118 {
119 char *rpath, *dest, *extra_buf = NULL;
120 const char *start, *end, *rpath_limit;
121 long int path_max;
122 int num_links = 0;
123 size_t prefix_len;
124
125 if (name == NULL)
126 {
127 /* As per Single Unix Specification V2 we must return an error if
128 either parameter is a null pointer. We extend this to allow
129 the RESOLVED parameter to be NULL in case the we are expected to
130 allocate the room for the return value. */
131 __set_errno (EINVAL);
132 return NULL;
133 }
134
135 if (name[0] == '\0')
136 {
137 /* As per Single Unix Specification V2 we must return an error if
138 the name argument points to an empty string. */
139 __set_errno (ENOENT);
140 return NULL;
141 }
142
143 #ifdef PATH_MAX
144 path_max = PATH_MAX;
145 #else
146 path_max = pathconf (name, _PC_PATH_MAX);
147 if (path_max <= 0)
148 path_max = 8192;
149 #endif
150
151 if (resolved == NULL)
152 {
153 rpath = malloc (path_max);
154 if (rpath == NULL)
155 {
156 alloc_failed ();
157 return NULL;
158 }
159 }
160 else
161 rpath = resolved;
162 rpath_limit = rpath + path_max;
163
164 /* This is always zero for Posix hosts, but can be 2 for MS-Windows
165 and MS-DOS X:/foo/bar file names. */
166 prefix_len = FILE_SYSTEM_PREFIX_LEN (name);
167
168 if (!IS_ABSOLUTE_FILE_NAME (name))
169 {
170 if (!__getcwd (rpath, path_max))
171 {
172 rpath[0] = '\0';
173 goto error;
174 }
175 dest = strchr (rpath, '\0');
176 start = name;
177 prefix_len = FILE_SYSTEM_PREFIX_LEN (rpath);
178 }
179 else
180 {
181 dest = rpath;
182 if (prefix_len)
183 {
184 memcpy (rpath, name, prefix_len);
185 dest += prefix_len;
186 }
187 *dest++ = '/';
188 if (DOUBLE_SLASH_IS_DISTINCT_ROOT)
189 {
190 if (ISSLASH (name[1]) && !ISSLASH (name[2]) && !prefix_len)
191 *dest++ = '/';
192 *dest = '\0';
193 }
194 start = name + prefix_len;
195 }
196
197 for (end = start; *start; start = end)
198 {
199 #ifdef _LIBC
200 struct stat64 st;
201 #else
202 struct stat st;
203 #endif
204
205 /* Skip sequence of multiple path-separators. */
206 while (ISSLASH (*start))
207 ++start;
208
209 /* Find end of path component. */
210 for (end = start; *end && !ISSLASH (*end); ++end)
211 /* Nothing. */;
212
213 if (end - start == 0)
214 break;
215 else if (end - start == 1 && start[0] == '.')
216 /* nothing */;
217 else if (end - start == 2 && start[0] == '.' && start[1] == '.')
218 {
219 /* Back up to previous component, ignore if at root already. */
220 if (dest > rpath + prefix_len + 1)
221 for (--dest; dest > rpath && !ISSLASH (dest[-1]); --dest)
222 continue;
223 if (DOUBLE_SLASH_IS_DISTINCT_ROOT
224 && dest == rpath + 1 && !prefix_len
225 && ISSLASH (*dest) && !ISSLASH (dest[1]))
226 dest++;
227 }
228 else
229 {
230 size_t new_size;
231
232 if (!ISSLASH (dest[-1]))
233 *dest++ = '/';
234
235 if (dest + (end - start) >= rpath_limit)
236 {
237 ptrdiff_t dest_offset = dest - rpath;
238 char *new_rpath;
239
240 if (resolved)
241 {
242 __set_errno (ENAMETOOLONG);
243 if (dest > rpath + prefix_len + 1)
244 dest--;
245 *dest = '\0';
246 goto error;
247 }
248 new_size = rpath_limit - rpath;
249 if (end - start + 1 > path_max)
250 new_size += end - start + 1;
251 else
252 new_size += path_max;
253 new_rpath = (char *) realloc (rpath, new_size);
254 if (new_rpath == NULL)
255 {
256 alloc_failed ();
257 goto error;
258 }
259 rpath = new_rpath;
260 rpath_limit = rpath + new_size;
261
262 dest = rpath + dest_offset;
263 }
264
265 #ifdef _LIBC
266 dest = __mempcpy (dest, start, end - start);
267 #else
268 memcpy (dest, start, end - start);
269 dest += end - start;
270 #endif
271 *dest = '\0';
272
273 /* FIXME: if lstat fails with errno == EOVERFLOW,
274 the entry exists. */
275 #ifdef _LIBC
276 if (__lxstat64 (_STAT_VER, rpath, &st) < 0)
277 #else
278 if (lstat (rpath, &st) < 0)
279 #endif
280 goto error;
281
282 if (S_ISLNK (st.st_mode))
283 {
284 char *buf;
285 size_t len;
286 ssize_t n;
287
288 if (++num_links > MAXSYMLINKS)
289 {
290 __set_errno (ELOOP);
291 goto error;
292 }
293
294 buf = malloca (path_max);
295 if (!buf)
296 {
297 __set_errno (ENOMEM);
298 goto error;
299 }
300
301 n = __readlink (rpath, buf, path_max - 1);
302 if (n < 0)
303 {
304 int saved_errno = errno;
305 freea (buf);
306 __set_errno (saved_errno);
307 goto error;
308 }
309 buf[n] = '\0';
310
311 if (!extra_buf)
312 {
313 extra_buf = malloca (path_max);
314 if (!extra_buf)
315 {
316 freea (buf);
317 __set_errno (ENOMEM);
318 goto error;
319 }
320 }
321
322 len = strlen (end);
323 /* Check that n + len + 1 doesn't overflow and is <= path_max. */
324 if (n >= SIZE_MAX - len || n + len >= path_max)
325 {
326 freea (buf);
327 __set_errno (ENAMETOOLONG);
328 goto error;
329 }
330
331 /* Careful here, end may be a pointer into extra_buf... */
332 memmove (&extra_buf[n], end, len + 1);
333 name = end = memcpy (extra_buf, buf, n);
334
335 if (IS_ABSOLUTE_FILE_NAME (buf))
336 {
337 size_t pfxlen = FILE_SYSTEM_PREFIX_LEN (buf);
338
339 if (pfxlen)
340 memcpy (rpath, buf, pfxlen);
341 dest = rpath + pfxlen;
342 *dest++ = '/'; /* It's an absolute symlink */
343 if (DOUBLE_SLASH_IS_DISTINCT_ROOT)
344 {
345 if (ISSLASH (buf[1]) && !ISSLASH (buf[2]) && !pfxlen)
346 *dest++ = '/';
347 *dest = '\0';
348 }
349 /* Install the new prefix to be in effect hereafter. */
350 prefix_len = pfxlen;
351 }
352 else
353 {
354 /* Back up to previous component, ignore if at root
355 already: */
356 if (dest > rpath + prefix_len + 1)
357 for (--dest; dest > rpath && !ISSLASH (dest[-1]); --dest)
358 continue;
359 if (DOUBLE_SLASH_IS_DISTINCT_ROOT && dest == rpath + 1
360 && ISSLASH (*dest) && !ISSLASH (dest[1]) && !prefix_len)
361 dest++;
362 }
363 }
364 else if (!S_ISDIR (st.st_mode) && *end != '\0')
365 {
366 __set_errno (ENOTDIR);
367 goto error;
368 }
369 }
370 }
371 if (dest > rpath + prefix_len + 1 && ISSLASH (dest[-1]))
372 --dest;
373 if (DOUBLE_SLASH_IS_DISTINCT_ROOT && dest == rpath + 1 && !prefix_len
374 && ISSLASH (*dest) && !ISSLASH (dest[1]))
375 dest++;
376 *dest = '\0';
377
378 if (extra_buf)
379 freea (extra_buf);
380
381 return rpath;
382
383 error:
384 {
385 int saved_errno = errno;
386 if (extra_buf)
387 freea (extra_buf);
388 if (resolved == NULL)
389 free (rpath);
390 __set_errno (saved_errno);
391 }
392 return NULL;
393 }
394 versioned_symbol (libc, __realpath, realpath, GLIBC_2_3);
395 #endif /* !FUNC_REALPATH_WORKS || defined _LIBC */
396
397
398 #if SHLIB_COMPAT(libc, GLIBC_2_0, GLIBC_2_3)
399 char *
400 attribute_compat_text_section
__old_realpath(const char * name,char * resolved)401 __old_realpath (const char *name, char *resolved)
402 {
403 if (resolved == NULL)
404 {
405 __set_errno (EINVAL);
406 return NULL;
407 }
408
409 return __realpath (name, resolved);
410 }
411 compat_symbol (libc, __old_realpath, realpath, GLIBC_2_0);
412 #endif
413
414
415 char *
__canonicalize_file_name(const char * name)416 __canonicalize_file_name (const char *name)
417 {
418 return __realpath (name, NULL);
419 }
420 weak_alias (__canonicalize_file_name, canonicalize_file_name)
421
422 #else
423
424 /* This declaration is solely to ensure that after preprocessing
425 this file is never empty. */
426 typedef int dummy;
427
428 #endif
429