Hurd: Define some posix types
[glibc.git] / elf / chroot_canon.c
bloba7a7d9b22582cbbee77a0b969d5e64e4ab592463
1 /* Return the canonical absolute name of a given file inside chroot.
2 Copyright (C) 1996,1997,1998,1999,2000,2001,2004,2005,2010,2011
3 Free Software Foundation, Inc.
4 This file is part of the GNU C Library.
6 This program is free software; you can redistribute it and/or modify
7 it under the terms of the GNU General Public License as published
8 by the Free Software Foundation; version 2 of the License, or
9 (at your option) any later version.
11 This program is distributed in the hope that it will be useful,
12 but WITHOUT ANY WARRANTY; without even the implied warranty of
13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 GNU General Public License for more details.
16 You should have received a copy of the GNU General Public License
17 along with this program; if not, see <http://www.gnu.org/licenses/>. */
19 #include <stdlib.h>
20 #include <string.h>
21 #include <unistd.h>
22 #include <limits.h>
23 #include <sys/param.h>
24 #include <sys/stat.h>
25 #include <errno.h>
26 #include <stddef.h>
27 #include <stdint.h>
29 #include <ldconfig.h>
31 #ifndef PATH_MAX
32 #define PATH_MAX 1024
33 #endif
35 /* Return the canonical absolute name of file NAME as if chroot(CHROOT) was
36 done first. A canonical name does not contain any `.', `..' components
37 nor any repeated path separators ('/') or symlinks. All path components
38 must exist and NAME must be absolute filename. The result is malloc'd.
39 The returned name includes the CHROOT prefix. */
41 char *
42 chroot_canon (const char *chroot, const char *name)
44 char *rpath;
45 char *dest;
46 char *extra_buf = NULL;
47 char *rpath_root;
48 const char *start;
49 const char *end;
50 const char *rpath_limit;
51 int num_links = 0;
52 size_t chroot_len = strlen (chroot);
54 if (chroot_len < 1)
56 __set_errno (EINVAL);
57 return NULL;
60 rpath = xmalloc (chroot_len + PATH_MAX);
62 rpath_limit = rpath + chroot_len + PATH_MAX;
64 rpath_root = (char *) mempcpy (rpath, chroot, chroot_len) - 1;
65 if (*rpath_root != '/')
66 *++rpath_root = '/';
67 dest = rpath_root + 1;
69 for (start = end = name; *start; start = end)
71 struct stat64 st;
73 /* Skip sequence of multiple path-separators. */
74 while (*start == '/')
75 ++start;
77 /* Find end of path component. */
78 for (end = start; *end && *end != '/'; ++end)
79 /* Nothing. */;
81 if (end - start == 0)
82 break;
83 else if (end - start == 1 && start[0] == '.')
84 /* nothing */;
85 else if (end - start == 2 && start[0] == '.' && start[1] == '.')
87 /* Back up to previous component, ignore if at root already. */
88 if (dest > rpath_root + 1)
89 while ((--dest)[-1] != '/');
91 else
93 size_t new_size;
95 if (dest[-1] != '/')
96 *dest++ = '/';
98 if (dest + (end - start) >= rpath_limit)
100 ptrdiff_t dest_offset = dest - rpath;
101 char *new_rpath;
103 new_size = rpath_limit - rpath;
104 if (end - start + 1 > PATH_MAX)
105 new_size += end - start + 1;
106 else
107 new_size += PATH_MAX;
108 new_rpath = (char *) xrealloc (rpath, new_size);
109 rpath = new_rpath;
110 rpath_limit = rpath + new_size;
112 dest = rpath + dest_offset;
115 dest = mempcpy (dest, start, end - start);
116 *dest = '\0';
118 if (lstat64 (rpath, &st) < 0)
120 if (*end == '\0')
121 goto done;
122 goto error;
125 if (S_ISLNK (st.st_mode))
127 char *buf = alloca (PATH_MAX);
128 size_t len;
130 if (++num_links > MAXSYMLINKS)
132 __set_errno (ELOOP);
133 goto error;
136 ssize_t n = readlink (rpath, buf, PATH_MAX - 1);
137 if (n < 0)
139 if (*end == '\0')
140 goto done;
141 goto error;
143 buf[n] = '\0';
145 if (!extra_buf)
146 extra_buf = alloca (PATH_MAX);
148 len = strlen (end);
149 if (len >= PATH_MAX - n)
151 __set_errno (ENAMETOOLONG);
152 goto error;
155 /* Careful here, end may be a pointer into extra_buf... */
156 memmove (&extra_buf[n], end, len + 1);
157 name = end = memcpy (extra_buf, buf, n);
159 if (buf[0] == '/')
160 dest = rpath_root + 1; /* It's an absolute symlink */
161 else
162 /* Back up to previous component, ignore if at root already: */
163 if (dest > rpath_root + 1)
164 while ((--dest)[-1] != '/');
168 done:
169 if (dest > rpath_root + 1 && dest[-1] == '/')
170 --dest;
171 *dest = '\0';
173 return rpath;
175 error:
176 free (rpath);
177 return NULL;