lib/canonicalize-lgpl.c

   1 /* Return the canonical absolute name of a given file.
   2    Copyright (C) 1996-2003, 2005-2008 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 Lesser 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 Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public License
  16    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  17
  18 #include <config.h>
  19
  20 /* Avoid a clash of our rpl_realpath() function with the prototype in
  21    <stdlib.h> on Solaris 2.5.1.  */
  22 #undef realpath
  23
  24 #if !HAVE_CANONICALIZE_FILE_NAME || defined _LIBC
  25
  26 #include <alloca.h>
  27
  28 /* Specification.  */
  29 #include "canonicalize.h"
  30
  31 #include <stddef.h>
  32 #include <stdlib.h>
  33 #include <string.h>
  34
  35 #if HAVE_UNISTD_H || defined _LIBC
  36 # include <unistd.h>
  37 #endif
  38
  39 #include <limits.h>
  40
  41 #if HAVE_SYS_PARAM_H || defined _LIBC
  42 # include <sys/param.h>
  43 #endif
  44 #ifndef MAXSYMLINKS
  45 # define MAXSYMLINKS 20
  46 #endif
  47
  48 #include <sys/stat.h>
  49
  50 #include <errno.h>
  51 #ifndef _LIBC
  52 # define __set_errno(e) errno = (e)
  53 # ifndef ENAMETOOLONG
  54 #  define ENAMETOOLONG EINVAL
  55 # endif
  56 #endif
  57
  58 #ifdef _LIBC
  59 # include <shlib-compat.h>
  60 #else
  61 # define SHLIB_COMPAT(lib, introduced, obsoleted) 0
  62 # define versioned_symbol(lib, local, symbol, version)
  63 # define compat_symbol(lib, local, symbol, version)
  64 # define weak_alias(local, symbol)
  65 # define __canonicalize_file_name canonicalize_file_name
  66 # define __realpath rpl_realpath
  67 # include "pathmax.h"
  68 # include "malloca.h"
  69 # if HAVE_GETCWD
  70 #  ifdef VMS
  71     /* We want the directory in Unix syntax, not in VMS syntax.  */
  72 #   define __getcwd(buf, max) getcwd (buf, max, 0)
  73 #  else
  74 #   define __getcwd getcwd
  75 #  endif
  76 # else
  77 #  define __getcwd(buf, max) getwd (buf)
  78 # endif
  79 # define __readlink readlink
  80   /* On systems without symbolic links, call stat() instead of lstat().  */
  81 # if !defined S_ISLNK && !HAVE_READLINK
  82 #  define lstat stat
  83 # endif
  84 #endif
  85
  86 /* Return the canonical absolute name of file NAME.  A canonical name
  87    does not contain any `.', `..' components nor any repeated path
  88    separators ('/') or symlinks.  All path components must exist.  If
  89    RESOLVED is null, the result is malloc'd; otherwise, if the
  90    canonical name is PATH_MAX chars or more, returns null with `errno'
  91    set to ENAMETOOLONG; if the name fits in fewer than PATH_MAX chars,
  92    returns the name in RESOLVED.  If the name cannot be resolved and
  93    RESOLVED is non-NULL, it contains the path of the first component
  94    that cannot be resolved.  If the path can be resolved, RESOLVED
  95    holds the same value as the value returned.  */
  96
  97 char *
  98 __realpath (const char *name, char *resolved)
  99 {
 100   char *rpath, *dest, *extra_buf = NULL;
 101   const char *start, *end, *rpath_limit;
 102   long int path_max;
 103 #if HAVE_READLINK
 104   int num_links = 0;
 105 #endif
 106
 107   if (name == NULL)
 108     {
 109       /* As per Single Unix Specification V2 we must return an error if
 110          either parameter is a null pointer.  We extend this to allow
 111          the RESOLVED parameter to be NULL in case the we are expected to
 112          allocate the room for the return value.  */
 113       __set_errno (EINVAL);
 114       return NULL;
 115     }
 116
 117   if (name[0] == '\0')
 118     {
 119       /* As per Single Unix Specification V2 we must return an error if
 120          the name argument points to an empty string.  */
 121       __set_errno (ENOENT);
 122       return NULL;
 123     }
 124
 125 #ifdef PATH_MAX
 126   path_max = PATH_MAX;
 127 #else
 128   path_max = pathconf (name, _PC_PATH_MAX);
 129   if (path_max <= 0)
 130     path_max = 1024;
 131 #endif
 132
 133   if (resolved == NULL)
 134     {
 135       rpath = malloc (path_max);
 136       if (rpath == NULL)
 137         {
 138           /* It's easier to set errno to ENOMEM than to rely on the
 139              'malloc-posix' gnulib module.  */
 140           errno = ENOMEM;
 141           return NULL;
 142         }
 143     }
 144   else
 145     rpath = resolved;
 146   rpath_limit = rpath + path_max;
 147
 148   if (name[0] != '/')
 149     {
 150       if (!__getcwd (rpath, path_max))
 151         {
 152           rpath[0] = '\0';
 153           goto error;
 154         }
 155       dest = strchr (rpath, '\0');
 156     }
 157   else
 158     {
 159       rpath[0] = '/';
 160       dest = rpath + 1;
 161     }
 162
 163   for (start = end = name; *start; start = end)
 164     {
 165 #ifdef _LIBC
 166       struct stat64 st;
 167 #else
 168       struct stat st;
 169 #endif
 170
 171       /* Skip sequence of multiple path-separators.  */
 172       while (*start == '/')
 173         ++start;
 174
 175       /* Find end of path component.  */
 176       for (end = start; *end && *end != '/'; ++end)
 177         /* Nothing.  */;
 178
 179       if (end - start == 0)
 180         break;
 181       else if (end - start == 1 && start[0] == '.')
 182         /* nothing */;
 183       else if (end - start == 2 && start[0] == '.' && start[1] == '.')
 184         {
 185           /* Back up to previous component, ignore if at root already.  */
 186           if (dest > rpath + 1)
 187             while ((--dest)[-1] != '/');
 188         }
 189       else
 190         {
 191           size_t new_size;
 192
 193           if (dest[-1] != '/')
 194             *dest++ = '/';
 195
 196           if (dest + (end - start) >= rpath_limit)
 197             {
 198               ptrdiff_t dest_offset = dest - rpath;
 199               char *new_rpath;
 200
 201               if (resolved)
 202                 {
 203                   __set_errno (ENAMETOOLONG);
 204                   if (dest > rpath + 1)
 205                     dest--;
 206                   *dest = '\0';
 207                   goto error;
 208                 }
 209               new_size = rpath_limit - rpath;
 210               if (end - start + 1 > path_max)
 211                 new_size += end - start + 1;
 212               else
 213                 new_size += path_max;
 214               new_rpath = (char *) realloc (rpath, new_size);
 215               if (new_rpath == NULL)
 216                 {
 217                   /* It's easier to set errno to ENOMEM than to rely on the
 218                      'realloc-posix' gnulib module.  */
 219                   errno = ENOMEM;
 220                   goto error;
 221                 }
 222               rpath = new_rpath;
 223               rpath_limit = rpath + new_size;
 224
 225               dest = rpath + dest_offset;
 226             }
 227
 228 #ifdef _LIBC
 229           dest = __mempcpy (dest, start, end - start);
 230 #else
 231           memcpy (dest, start, end - start);
 232           dest += end - start;
 233 #endif
 234           *dest = '\0';
 235
 236 #ifdef _LIBC
 237           if (__lxstat64 (_STAT_VER, rpath, &st) < 0)
 238 #else
 239           if (lstat (rpath, &st) < 0)
 240 #endif
 241             goto error;
 242
 243 #if HAVE_READLINK
 244           if (S_ISLNK (st.st_mode))
 245             {
 246               char *buf;
 247               size_t len;
 248               int n;
 249
 250               if (++num_links > MAXSYMLINKS)
 251                 {
 252                   __set_errno (ELOOP);
 253                   goto error;
 254                 }
 255
 256               buf = malloca (path_max);
 257               if (!buf)
 258                 {
 259                   errno = ENOMEM;
 260                   goto error;
 261                 }
 262
 263               n = __readlink (rpath, buf, path_max - 1);
 264               if (n < 0)
 265                 {
 266                   int saved_errno = errno;
 267                   freea (buf);
 268                   errno = saved_errno;
 269                   goto error;
 270                 }
 271               buf[n] = '\0';
 272
 273               if (!extra_buf)
 274                 {
 275                   extra_buf = malloca (path_max);
 276                   if (!extra_buf)
 277                     {
 278                       freea (buf);
 279                       errno = ENOMEM;
 280                       goto error;
 281                     }
 282                 }
 283
 284               len = strlen (end);
 285               if ((long int) (n + len) >= path_max)
 286                 {
 287                   freea (buf);
 288                   __set_errno (ENAMETOOLONG);
 289                   goto error;
 290                 }
 291
 292               /* Careful here, end may be a pointer into extra_buf... */
 293               memmove (&extra_buf[n], end, len + 1);
 294               name = end = memcpy (extra_buf, buf, n);
 295
 296               if (buf[0] == '/')
 297                 dest = rpath + 1;       /* It's an absolute symlink */
 298               else
 299                 /* Back up to previous component, ignore if at root already: */
 300                 if (dest > rpath + 1)
 301                   while ((--dest)[-1] != '/');
 302             }
 303 #endif
 304         }
 305     }
 306   if (dest > rpath + 1 && dest[-1] == '/')
 307     --dest;
 308   *dest = '\0';
 309
 310   if (extra_buf)
 311     freea (extra_buf);
 312
 313   return resolved ? memcpy (resolved, rpath, dest - rpath + 1) : rpath;
 314
 315 error:
 316   {
 317     int saved_errno = errno;
 318     if (extra_buf)
 319       freea (extra_buf);
 320     if (resolved)
 321       strcpy (resolved, rpath);
 322     else
 323       free (rpath);
 324     errno = saved_errno;
 325   }
 326   return NULL;
 327 }
 328 #ifdef _LIBC
 329 versioned_symbol (libc, __realpath, realpath, GLIBC_2_3);
 330 #endif
 331
 332
 333 #if SHLIB_COMPAT(libc, GLIBC_2_0, GLIBC_2_3)
 334 char *
 335 __old_realpath (const char *name, char *resolved)
 336 {
 337   if (resolved == NULL)
 338     {
 339       __set_errno (EINVAL);
 340       return NULL;
 341     }
 342
 343   return __realpath (name, resolved);
 344 }
 345 compat_symbol (libc, __old_realpath, realpath, GLIBC_2_0);
 346 #endif
 347
 348
 349 char *
 350 __canonicalize_file_name (const char *name)
 351 {
 352   return __realpath (name, NULL);
 353 }
 354 weak_alias (__canonicalize_file_name, canonicalize_file_name)
 355
 356 #else
 357
 358 /* This declaration is solely to ensure that after preprocessing
 359    this file is never empty.  */
 360 typedef int dummy;
 361
 362 #endif