1/* Return the canonical absolute name of a given file.
2 Copyright (C) 1996-2018 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library 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 GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <http://www.gnu.org/licenses/>. */
18
19#include <assert.h>
20#include <stdlib.h>
21#include <string.h>
22#include <unistd.h>
23#include <limits.h>
24#include <sys/stat.h>
25#include <errno.h>
26#include <stddef.h>
27
28#include <eloop-threshold.h>
29#include <shlib-compat.h>
30
31/* Return the canonical absolute name of file NAME. A canonical name
32 does not contain any `.', `..' components nor any repeated path
33 separators ('/') or symlinks. All path components must exist. If
34 RESOLVED is null, the result is malloc'd; otherwise, if the
35 canonical name is PATH_MAX chars or more, returns null with `errno'
36 set to ENAMETOOLONG; if the name fits in fewer than PATH_MAX chars,
37 returns the name in RESOLVED. If the name cannot be resolved and
38 RESOLVED is non-NULL, it contains the path of the first component
39 that cannot be resolved. If the path can be resolved, RESOLVED
40 holds the same value as the value returned. */
41
42char *
43__realpath (const char *name, char *resolved)
44{
45 char *rpath, *dest, *extra_buf = NULL;
46 const char *start, *end, *rpath_limit;
47 long int path_max;
48 int num_links = 0;
49
50 if (name == NULL)
51 {
52 /* As per Single Unix Specification V2 we must return an error if
53 either parameter is a null pointer. We extend this to allow
54 the RESOLVED parameter to be NULL in case the we are expected to
55 allocate the room for the return value. */
56 __set_errno (EINVAL);
57 return NULL;
58 }
59
60 if (name[0] == '\0')
61 {
62 /* As per Single Unix Specification V2 we must return an error if
63 the name argument points to an empty string. */
64 __set_errno (ENOENT);
65 return NULL;
66 }
67
68#ifdef PATH_MAX
69 path_max = PATH_MAX;
70#else
71 path_max = pathconf (name, _PC_PATH_MAX);
72 if (path_max <= 0)
73 path_max = 1024;
74#endif
75
76 if (resolved == NULL)
77 {
78 rpath = malloc (path_max);
79 if (rpath == NULL)
80 return NULL;
81 }
82 else
83 rpath = resolved;
84 rpath_limit = rpath + path_max;
85
86 if (name[0] != '/')
87 {
88 if (!__getcwd (rpath, path_max))
89 {
90 rpath[0] = '\0';
91 goto error;
92 }
93 dest = __rawmemchr (rpath, '\0');
94 }
95 else
96 {
97 rpath[0] = '/';
98 dest = rpath + 1;
99 }
100
101 for (start = end = name; *start; start = end)
102 {
103 struct stat64 st;
104 int n;
105
106 /* Skip sequence of multiple path-separators. */
107 while (*start == '/')
108 ++start;
109
110 /* Find end of path component. */
111 for (end = start; *end && *end != '/'; ++end)
112 /* Nothing. */;
113
114 if (end - start == 0)
115 break;
116 else if (end - start == 1 && start[0] == '.')
117 /* nothing */;
118 else if (end - start == 2 && start[0] == '.' && start[1] == '.')
119 {
120 /* Back up to previous component, ignore if at root already. */
121 if (dest > rpath + 1)
122 while ((--dest)[-1] != '/');
123 }
124 else
125 {
126 size_t new_size;
127
128 if (dest[-1] != '/')
129 *dest++ = '/';
130
131 if (dest + (end - start) >= rpath_limit)
132 {
133 ptrdiff_t dest_offset = dest - rpath;
134 char *new_rpath;
135
136 if (resolved)
137 {
138 __set_errno (ENAMETOOLONG);
139 if (dest > rpath + 1)
140 dest--;
141 *dest = '\0';
142 goto error;
143 }
144 new_size = rpath_limit - rpath;
145 if (end - start + 1 > path_max)
146 new_size += end - start + 1;
147 else
148 new_size += path_max;
149 new_rpath = (char *) realloc (rpath, new_size);
150 if (new_rpath == NULL)
151 goto error;
152 rpath = new_rpath;
153 rpath_limit = rpath + new_size;
154
155 dest = rpath + dest_offset;
156 }
157
158 dest = __mempcpy (dest, start, end - start);
159 *dest = '\0';
160
161 if (__lxstat64 (_STAT_VER, rpath, &st) < 0)
162 goto error;
163
164 if (S_ISLNK (st.st_mode))
165 {
166 char *buf = __alloca (path_max);
167 size_t len;
168
169 if (++num_links > __eloop_threshold ())
170 {
171 __set_errno (ELOOP);
172 goto error;
173 }
174
175 n = __readlink (rpath, buf, path_max - 1);
176 if (n < 0)
177 goto error;
178 buf[n] = '\0';
179
180 if (!extra_buf)
181 extra_buf = __alloca (path_max);
182
183 len = strlen (end);
184 if ((long int) (n + len) >= path_max)
185 {
186 __set_errno (ENAMETOOLONG);
187 goto error;
188 }
189
190 /* Careful here, end may be a pointer into extra_buf... */
191 memmove (&extra_buf[n], end, len + 1);
192 name = end = memcpy (extra_buf, buf, n);
193
194 if (buf[0] == '/')
195 dest = rpath + 1; /* It's an absolute symlink */
196 else
197 /* Back up to previous component, ignore if at root already: */
198 if (dest > rpath + 1)
199 while ((--dest)[-1] != '/');
200 }
201 else if (!S_ISDIR (st.st_mode) && *end != '\0')
202 {
203 __set_errno (ENOTDIR);
204 goto error;
205 }
206 }
207 }
208 if (dest > rpath + 1 && dest[-1] == '/')
209 --dest;
210 *dest = '\0';
211
212 assert (resolved == NULL || resolved == rpath);
213 return rpath;
214
215error:
216 assert (resolved == NULL || resolved == rpath);
217 if (resolved == NULL)
218 free (rpath);
219 return NULL;
220}
221libc_hidden_def (__realpath)
222versioned_symbol (libc, __realpath, realpath, GLIBC_2_3);
223
224
225#if SHLIB_COMPAT(libc, GLIBC_2_0, GLIBC_2_3)
226char *
227attribute_compat_text_section
228__old_realpath (const char *name, char *resolved)
229{
230 if (resolved == NULL)
231 {
232 __set_errno (EINVAL);
233 return NULL;
234 }
235
236 return __realpath (name, resolved);
237}
238compat_symbol (libc, __old_realpath, realpath, GLIBC_2_0);
239#endif
240
241
242char *
243__canonicalize_file_name (const char *name)
244{
245 return __realpath (name, NULL);
246}
247weak_alias (__canonicalize_file_name, canonicalize_file_name)
248