lib/canonicalize-lgpl.c

   1 /* Return the canonical absolute name of a given file.
   2    Copyright (C) 1996-2011 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 #ifndef _LIBC
  19 # define _GL_USE_STDLIB_ALLOC 1
  20 # include <config.h>
  21 #endif
  22
  23 #if !HAVE_CANONICALIZE_FILE_NAME || !FUNC_REALPATH_WORKS || defined _LIBC
  24
  25 /* Don't use __attribute__ __nonnull__ in this compilation unit.  Otherwise gcc
  26    optimizes away the name == NULL test below.  */
  27 #define _GL_ARG_NONNULL(params)
  28
  29 /* Specification.  */
  30 #include <stdlib.h>
  31
  32 #include <alloca.h>
  33 #include <string.h>
  34 #include <unistd.h>
  35 #include <limits.h>
  36 #if HAVE_SYS_PARAM_H || defined _LIBC
  37 # include <sys/param.h>
  38 #endif
  39 #include <sys/stat.h>
  40 #include <errno.h>
  41 #include <stddef.h>
  42
  43 #ifdef _LIBC
  44 # include <shlib-compat.h>
  45 #else
  46 # define SHLIB_COMPAT(lib, introduced, obsoleted) 0
  47 # define versioned_symbol(lib, local, symbol, version) extern int dummy
  48 # define compat_symbol(lib, local, symbol, version)
  49 # define weak_alias(local, symbol)
  50 # define __canonicalize_file_name canonicalize_file_name
  51 # define __realpath realpath
  52 # include "pathmax.h"
  53 # include "malloca.h"
  54 # if HAVE_GETCWD
  55 #  if IN_RELOCWRAPPER
  56     /* When building the relocatable program wrapper, use the system's getcwd
  57        function, not the gnulib override, otherwise we would get a link error.
  58      */
  59 #   undef getcwd
  60 #  endif
  61 #  ifdef VMS
  62     /* We want the directory in Unix syntax, not in VMS syntax.  */
  63 #   define __getcwd(buf, max) getcwd (buf, max, 0)
  64 #  else
  65 #   define __getcwd getcwd
  66 #  endif
  67 # else
  68 #  define __getcwd(buf, max) getwd (buf)
  69 # endif
  70 # define __readlink readlink
  71 # define __set_errno(e) errno = (e)
  72 # ifndef MAXSYMLINKS
  73 #  ifdef SYMLOOP_MAX
  74 #   define MAXSYMLINKS SYMLOOP_MAX
  75 #  else
  76 #   define MAXSYMLINKS 20
  77 #  endif
  78 # endif
  79 #endif
  80
  81 #ifndef DOUBLE_SLASH_IS_DISTINCT_ROOT
  82 # define DOUBLE_SLASH_IS_DISTINCT_ROOT 0
  83 #endif
  84
  85 #if !FUNC_REALPATH_WORKS || defined _LIBC
  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   int num_links = 0;
 104
 105   if (name == NULL)
 106     {
 107       /* As per Single Unix Specification V2 we must return an error if
 108          either parameter is a null pointer.  We extend this to allow
 109          the RESOLVED parameter to be NULL in case the we are expected to
 110          allocate the room for the return value.  */
 111       __set_errno (EINVAL);
 112       return NULL;
 113     }
 114
 115   if (name[0] == '\0')
 116     {
 117       /* As per Single Unix Specification V2 we must return an error if
 118          the name argument points to an empty string.  */
 119       __set_errno (ENOENT);
 120       return NULL;
 121     }
 122
 123 #ifdef PATH_MAX
 124   path_max = PATH_MAX;
 125 #else
 126   path_max = pathconf (name, _PC_PATH_MAX);
 127   if (path_max <= 0)
 128     path_max = 8192;
 129 #endif
 130
 131   if (resolved == NULL)
 132     {
 133       rpath = malloc (path_max);
 134       if (rpath == NULL)
 135         {
 136           /* It's easier to set errno to ENOMEM than to rely on the
 137              'malloc-posix' gnulib module.  */
 138           errno = ENOMEM;
 139           return NULL;
 140         }
 141     }
 142   else
 143     rpath = resolved;
 144   rpath_limit = rpath + path_max;
 145
 146   if (name[0] != '/')
 147     {
 148       if (!__getcwd (rpath, path_max))
 149         {
 150           rpath[0] = '\0';
 151           goto error;
 152         }
 153       dest = strchr (rpath, '\0');
 154     }
 155   else
 156     {
 157       rpath[0] = '/';
 158       dest = rpath + 1;
 159       if (DOUBLE_SLASH_IS_DISTINCT_ROOT && name[1] == '/')
 160         *dest++ = '/';
 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       int n;
 171
 172       /* Skip sequence of multiple path-separators.  */
 173       while (*start == '/')
 174         ++start;
 175
 176       /* Find end of path component.  */
 177       for (end = start; *end && *end != '/'; ++end)
 178         /* Nothing.  */;
 179
 180       if (end - start == 0)
 181         break;
 182       else if (end - start == 1 && start[0] == '.')
 183         /* nothing */;
 184       else if (end - start == 2 && start[0] == '.' && start[1] == '.')
 185         {
 186           /* Back up to previous component, ignore if at root already.  */
 187           if (dest > rpath + 1)
 188             while ((--dest)[-1] != '/');
 189           if (DOUBLE_SLASH_IS_DISTINCT_ROOT && dest == rpath + 1
 190               && *dest == '/')
 191             dest++;
 192         }
 193       else
 194         {
 195           size_t new_size;
 196
 197           if (dest[-1] != '/')
 198             *dest++ = '/';
 199
 200           if (dest + (end - start) >= rpath_limit)
 201             {
 202               ptrdiff_t dest_offset = dest - rpath;
 203               char *new_rpath;
 204
 205               if (resolved)
 206                 {
 207                   __set_errno (ENAMETOOLONG);
 208                   if (dest > rpath + 1)
 209                     dest--;
 210                   *dest = '\0';
 211                   goto error;
 212                 }
 213               new_size = rpath_limit - rpath;
 214               if (end - start + 1 > path_max)
 215                 new_size += end - start + 1;
 216               else
 217                 new_size += path_max;
 218               new_rpath = (char *) realloc (rpath, new_size);
 219               if (new_rpath == NULL)
 220                 {
 221                   /* It's easier to set errno to ENOMEM than to rely on the
 222                      'realloc-posix' gnulib module.  */
 223                   errno = ENOMEM;
 224                   goto error;
 225                 }
 226               rpath = new_rpath;
 227               rpath_limit = rpath + new_size;
 228
 229               dest = rpath + dest_offset;
 230             }
 231
 232 #ifdef _LIBC
 233           dest = __mempcpy (dest, start, end - start);
 234 #else
 235           memcpy (dest, start, end - start);
 236           dest += end - start;
 237 #endif
 238           *dest = '\0';
 239
 240 #ifdef _LIBC
 241           if (__lxstat64 (_STAT_VER, rpath, &st) < 0)
 242 #else
 243           if (lstat (rpath, &st) < 0)
 244 #endif
 245             goto error;
 246
 247           if (S_ISLNK (st.st_mode))
 248             {
 249               char *buf;
 250               size_t len;
 251
 252               if (++num_links > MAXSYMLINKS)
 253                 {
 254                   __set_errno (ELOOP);
 255                   goto error;
 256                 }
 257
 258               buf = malloca (path_max);
 259               if (!buf)
 260                 {
 261                   errno = ENOMEM;
 262                   goto error;
 263                 }
 264
 265               n = __readlink (rpath, buf, path_max - 1);
 266               if (n < 0)
 267                 {
 268                   int saved_errno = errno;
 269                   freea (buf);
 270                   errno = saved_errno;
 271                   goto error;
 272                 }
 273               buf[n] = '\0';
 274
 275               if (!extra_buf)
 276                 {
 277                   extra_buf = malloca (path_max);
 278                   if (!extra_buf)
 279                     {
 280                       freea (buf);
 281                       errno = ENOMEM;
 282                       goto error;
 283                     }
 284                 }
 285
 286               len = strlen (end);
 287               if ((long int) (n + len) >= path_max)
 288                 {
 289                   freea (buf);
 290                   __set_errno (ENAMETOOLONG);
 291                   goto error;
 292                 }
 293
 294               /* Careful here, end may be a pointer into extra_buf... */
 295               memmove (&extra_buf[n], end, len + 1);
 296               name = end = memcpy (extra_buf, buf, n);
 297
 298               if (buf[0] == '/')
 299                 {
 300                   dest = rpath + 1;     /* It's an absolute symlink */
 301                   if (DOUBLE_SLASH_IS_DISTINCT_ROOT && buf[1] == '/')
 302                     *dest++ = '/';
 303                 }
 304               else
 305                 {
 306                   /* Back up to previous component, ignore if at root
 307                      already: */
 308                   if (dest > rpath + 1)
 309                     while ((--dest)[-1] != '/');
 310                   if (DOUBLE_SLASH_IS_DISTINCT_ROOT && dest == rpath + 1
 311                       && *dest == '/')
 312                     dest++;
 313                 }
 314             }
 315           else if (!S_ISDIR (st.st_mode) && *end != '\0')
 316             {
 317               __set_errno (ENOTDIR);
 318               goto error;
 319             }
 320         }
 321     }
 322   if (dest > rpath + 1 && dest[-1] == '/')
 323     --dest;
 324   if (DOUBLE_SLASH_IS_DISTINCT_ROOT && dest == rpath + 1 && *dest == '/')
 325     dest++;
 326   *dest = '\0';
 327
 328   if (extra_buf)
 329     freea (extra_buf);
 330
 331   return rpath;
 332
 333 error:
 334   {
 335     int saved_errno = errno;
 336     if (extra_buf)
 337       freea (extra_buf);
 338     if (resolved == NULL)
 339       free (rpath);
 340     errno = saved_errno;
 341   }
 342   return NULL;
 343 }
 344 versioned_symbol (libc, __realpath, realpath, GLIBC_2_3);
 345 #endif /* !FUNC_REALPATH_WORKS || defined _LIBC */
 346
 347
 348 #if SHLIB_COMPAT(libc, GLIBC_2_0, GLIBC_2_3)
 349 char *
 350 attribute_compat_text_section
 351 __old_realpath (const char *name, char *resolved)
 352 {
 353   if (resolved == NULL)
 354     {
 355       __set_errno (EINVAL);
 356       return NULL;
 357     }
 358
 359   return __realpath (name, resolved);
 360 }
 361 compat_symbol (libc, __old_realpath, realpath, GLIBC_2_0);
 362 #endif
 363
 364
 365 char *
 366 __canonicalize_file_name (const char *name)
 367 {
 368   return __realpath (name, NULL);
 369 }
 370 weak_alias (__canonicalize_file_name, canonicalize_file_name)
 371
 372 #else
 373
 374 /* This declaration is solely to ensure that after preprocessing
 375    this file is never empty.  */
 376 typedef int dummy;
 377
 378 #endif