stdlib/canonicalize.c

   1 /* Return the canonical absolute name of a given file.
   2    Copyright (C) 1996-2001, 2002 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 <stdlib.h>
  21 #include <string.h>
  22 #include <unistd.h>
  23 #include <limits.h>
  24 #include <sys/param.h>
  25 #include <sys/stat.h>
  26 #include <errno.h>
  27 #include <stddef.h>
  28
  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
  42 char *
  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   rpath = resolved ? __alloca (path_max) : malloc (path_max);
  77   rpath_limit = rpath + path_max;
  78
  79   if (name[0] != '/')
  80     {
  81       if (!__getcwd (rpath, path_max))
  82         {
  83           rpath[0] = '\0';
  84           goto error;
  85         }
  86       dest = strchr (rpath, '\0');
  87     }
  88   else
  89     {
  90       rpath[0] = '/';
  91       dest = rpath + 1;
  92     }
  93
  94   for (start = end = name; *start; start = end)
  95     {
  96       struct stat64 st;
  97       int n;
  98
  99       /* Skip sequence of multiple path-separators.  */
 100       while (*start == '/')
 101         ++start;
 102
 103       /* Find end of path component.  */
 104       for (end = start; *end && *end != '/'; ++end)
 105         /* Nothing.  */;
 106
 107       if (end - start == 0)
 108         break;
 109       else if (end - start == 1 && start[0] == '.')
 110         /* nothing */;
 111       else if (end - start == 2 && start[0] == '.' && start[1] == '.')
 112         {
 113           /* Back up to previous component, ignore if at root already.  */
 114           if (dest > rpath + 1)
 115             while ((--dest)[-1] != '/');
 116         }
 117       else
 118         {
 119           size_t new_size;
 120
 121           if (dest[-1] != '/')
 122             *dest++ = '/';
 123
 124           if (dest + (end - start) >= rpath_limit)
 125             {
 126               ptrdiff_t dest_offset = dest - rpath;
 127               char *new_rpath;
 128
 129               if (resolved)
 130                 {
 131                   __set_errno (ENAMETOOLONG);
 132                   if (dest > rpath + 1)
 133                     dest--;
 134                   *dest = '\0';
 135                   goto error;
 136                 }
 137               new_size = rpath_limit - rpath;
 138               if (end - start + 1 > path_max)
 139                 new_size += end - start + 1;
 140               else
 141                 new_size += path_max;
 142               new_rpath = (char *) realloc (rpath, new_size);
 143               if (new_rpath == NULL)
 144                 goto error;
 145               rpath = new_rpath;
 146               rpath_limit = rpath + new_size;
 147
 148               dest = rpath + dest_offset;
 149             }
 150
 151           dest = __mempcpy (dest, start, end - start);
 152           *dest = '\0';
 153
 154           if (__lxstat64 (_STAT_VER, rpath, &st) < 0)
 155             goto error;
 156
 157           if (S_ISLNK (st.st_mode))
 158             {
 159               char *buf = __alloca (path_max);
 160               size_t len;
 161
 162               if (++num_links > MAXSYMLINKS)
 163                 {
 164                   __set_errno (ELOOP);
 165                   goto error;
 166                 }
 167
 168               n = __readlink (rpath, buf, path_max);
 169               if (n < 0)
 170                 goto error;
 171               buf[n] = '\0';
 172
 173               if (!extra_buf)
 174                 extra_buf = __alloca (path_max);
 175
 176               len = strlen (end);
 177               if ((long int) (n + len) >= path_max)
 178                 {
 179                   __set_errno (ENAMETOOLONG);
 180                   goto error;
 181                 }
 182
 183               /* Careful here, end may be a pointer into extra_buf... */
 184               memmove (&extra_buf[n], end, len + 1);
 185               name = end = memcpy (extra_buf, buf, n);
 186
 187               if (buf[0] == '/')
 188                 dest = rpath + 1;       /* It's an absolute symlink */
 189               else
 190                 /* Back up to previous component, ignore if at root already: */
 191                 if (dest > rpath + 1)
 192                   while ((--dest)[-1] != '/');
 193             }
 194         }
 195     }
 196   if (dest > rpath + 1 && dest[-1] == '/')
 197     --dest;
 198   *dest = '\0';
 199
 200   return resolved ? memcpy (resolved, rpath, dest - rpath + 1) : rpath;
 201
 202 error:
 203   if (resolved)
 204     strcpy (resolved, rpath);
 205   else
 206     free (rpath);
 207   return NULL;
 208 }
 209 versioned_symbol (libc, __realpath, realpath, GLIBC_2_3);
 210
 211
 212 #if SHLIB_COMPAT(libc, GLIBC_2_0, GLIBC_2_3)
 213 char *
 214 __old_realpath (const char *name, char *resolved)
 215 {
 216   if (resolved == NULL)
 217     {
 218       __set_errno (EINVAL);
 219       return NULL;
 220     }
 221
 222   return __realpath (name, resolved);
 223 }
 224 compat_symbol (libc, __old_realpath, realpath, GLIBC_2_0);
 225 #endif
 226
 227
 228 char *
 229 __canonicalize_file_name (const char *name)
 230 {
 231   return __realpath (name, NULL);
 232 }
 233 weak_alias (__canonicalize_file_name, canonicalize_file_name)