stdlib/canonicalize.c

   1 /* Return the canonical absolute name of a given file.
   2    Copyright (C) 1996-2001, 2002, 2004 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, write to the Free
  17    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  18    02111-1307 USA.  */
  19
  20 #include <assert.h>
  21 #include <stdlib.h>
  22 #include <string.h>
  23 #include <unistd.h>
  24 #include <limits.h>
  25 #include <sys/param.h>
  26 #include <sys/stat.h>
  27 #include <errno.h>
  28 #include <stddef.h>
  29
  30 #include <shlib-compat.h>
  31
  32 /* Return the canonical absolute name of file NAME.  A canonical name
  33    does not contain any `.', `..' components nor any repeated path
  34    separators ('/') or symlinks.  All path components must exist.  If
  35    RESOLVED is null, the result is malloc'd; otherwise, if the
  36    canonical name is PATH_MAX chars or more, returns null with `errno'
  37    set to ENAMETOOLONG; if the name fits in fewer than PATH_MAX chars,
  38    returns the name in RESOLVED.  If the name cannot be resolved and
  39    RESOLVED is non-NULL, it contains the path of the first component
  40    that cannot be resolved.  If the path can be resolved, RESOLVED
  41    holds the same value as the value returned.  */
  42
  43 char *
  44 __realpath (const char *name, char *resolved)
  45 {
  46   char *rpath, *dest, *extra_buf = NULL;
  47   const char *start, *end, *rpath_limit;
  48   long int path_max;
  49   int num_links = 0;
  50
  51   if (name == NULL)
  52     {
  53       /* As per Single Unix Specification V2 we must return an error if
  54          either parameter is a null pointer.  We extend this to allow
  55          the RESOLVED parameter to be NULL in case the we are expected to
  56          allocate the room for the return value.  */
  57       __set_errno (EINVAL);
  58       return NULL;
  59     }
  60
  61   if (name[0] == '\0')
  62     {
  63       /* As per Single Unix Specification V2 we must return an error if
  64          the name argument points to an empty string.  */
  65       __set_errno (ENOENT);
  66       return NULL;
  67     }
  68
  69 #ifdef PATH_MAX
  70   path_max = PATH_MAX;
  71 #else
  72   path_max = pathconf (name, _PC_PATH_MAX);
  73   if (path_max <= 0)
  74     path_max = 1024;
  75 #endif
  76
  77   if (resolved == NULL)
  78     {
  79       rpath = malloc (path_max);
  80       if (rpath == NULL)
  81         return NULL;
  82     }
  83   else
  84     rpath = resolved;
  85   rpath_limit = rpath + path_max;
  86
  87   if (name[0] != '/')
  88     {
  89       if (!__getcwd (rpath, path_max))
  90         {
  91           rpath[0] = '\0';
  92           goto error;
  93         }
  94       dest = strchr (rpath, '\0');
  95     }
  96   else
  97     {
  98       rpath[0] = '/';
  99       dest = rpath + 1;
 100     }
 101
 102   for (start = end = name; *start; start = end)
 103     {
 104       struct stat64 st;
 105       int n;
 106
 107       /* Skip sequence of multiple path-separators.  */
 108       while (*start == '/')
 109         ++start;
 110
 111       /* Find end of path component.  */
 112       for (end = start; *end && *end != '/'; ++end)
 113         /* Nothing.  */;
 114
 115       if (end - start == 0)
 116         break;
 117       else if (end - start == 1 && start[0] == '.')
 118         /* nothing */;
 119       else if (end - start == 2 && start[0] == '.' && start[1] == '.')
 120         {
 121           /* Back up to previous component, ignore if at root already.  */
 122           if (dest > rpath + 1)
 123             while ((--dest)[-1] != '/');
 124         }
 125       else
 126         {
 127           size_t new_size;
 128
 129           if (dest[-1] != '/')
 130             *dest++ = '/';
 131
 132           if (dest + (end - start) >= rpath_limit)
 133             {
 134               ptrdiff_t dest_offset = dest - rpath;
 135               char *new_rpath;
 136
 137               if (resolved)
 138                 {
 139                   __set_errno (ENAMETOOLONG);
 140                   if (dest > rpath + 1)
 141                     dest--;
 142                   *dest = '\0';
 143                   goto error;
 144                 }
 145               new_size = rpath_limit - rpath;
 146               if (end - start + 1 > path_max)
 147                 new_size += end - start + 1;
 148               else
 149                 new_size += path_max;
 150               new_rpath = (char *) realloc (rpath, new_size);
 151               if (new_rpath == NULL)
 152                 goto error;
 153               rpath = new_rpath;
 154               rpath_limit = rpath + new_size;
 155
 156               dest = rpath + dest_offset;
 157             }
 158
 159           dest = __mempcpy (dest, start, end - start);
 160           *dest = '\0';
 161
 162           if (__lxstat64 (_STAT_VER, rpath, &st) < 0)
 163             goto error;
 164
 165           if (S_ISLNK (st.st_mode))
 166             {
 167               char *buf = __alloca (path_max);
 168               size_t len;
 169
 170               if (++num_links > MAXSYMLINKS)
 171                 {
 172                   __set_errno (ELOOP);
 173                   goto error;
 174                 }
 175
 176               n = __readlink (rpath, buf, path_max);
 177               if (n < 0)
 178                 goto error;
 179               buf[n] = '\0';
 180
 181               if (!extra_buf)
 182                 extra_buf = __alloca (path_max);
 183
 184               len = strlen (end);
 185               if ((long int) (n + len) >= path_max)
 186                 {
 187                   __set_errno (ENAMETOOLONG);
 188                   goto error;
 189                 }
 190
 191               /* Careful here, end may be a pointer into extra_buf... */
 192               memmove (&extra_buf[n], end, len + 1);
 193               name = end = memcpy (extra_buf, buf, n);
 194
 195               if (buf[0] == '/')
 196                 dest = rpath + 1;       /* It's an absolute symlink */
 197               else
 198                 /* Back up to previous component, ignore if at root already: */
 199                 if (dest > rpath + 1)
 200                   while ((--dest)[-1] != '/');
 201             }
 202         }
 203     }
 204   if (dest > rpath + 1 && dest[-1] == '/')
 205     --dest;
 206   *dest = '\0';
 207
 208   assert (resolved == NULL || resolved == rpath);
 209   return rpath;
 210
 211 error:
 212   assert (resolved == NULL || resolved == rpath);
 213   if (resolved == NULL)
 214     free (rpath);
 215   return NULL;
 216 }
 217 versioned_symbol (libc, __realpath, realpath, GLIBC_2_3);
 218
 219
 220 #if SHLIB_COMPAT(libc, GLIBC_2_0, GLIBC_2_3)
 221 char *
 222 attribute_compat_text_section
 223 __old_realpath (const char *name, char *resolved)
 224 {
 225   if (resolved == NULL)
 226     {
 227       __set_errno (EINVAL);
 228       return NULL;
 229     }
 230
 231   return __realpath (name, resolved);
 232 }
 233 compat_symbol (libc, __old_realpath, realpath, GLIBC_2_0);
 234 #endif
 235
 236
 237 char *
 238 __canonicalize_file_name (const char *name)
 239 {
 240   return __realpath (name, NULL);
 241 }
 242 weak_alias (__canonicalize_file_name, canonicalize_file_name)