gnulib/import/canonicalize-lgpl.c

   1 /* Return the canonical absolute name of a given file.
   2    Copyright (C) 1996-2016 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 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 General Public License for more details.
  14
  15    You should have received a copy of the GNU General Public License
  16    along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
  17
  18 #ifndef _LIBC
  19 /* Don't use __attribute__ __nonnull__ in this compilation unit.  Otherwise gcc
  20    optimizes away the name == NULL test below.  */
  21 # define _GL_ARG_NONNULL(params)
  22
  23 # define _GL_USE_STDLIB_ALLOC 1
  24 # include <config.h>
  25 #endif
  26
  27 #if !HAVE_CANONICALIZE_FILE_NAME || !FUNC_REALPATH_WORKS || defined _LIBC
  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 # include "dosname.h"
  55 # if HAVE_GETCWD
  56 #  if IN_RELOCWRAPPER
  57     /* When building the relocatable program wrapper, use the system's getcwd
  58        function, not the gnulib override, otherwise we would get a link error.
  59      */
  60 #   undef getcwd
  61 #  endif
  62 #  ifdef VMS
  63     /* We want the directory in Unix syntax, not in VMS syntax.  */
  64 #   define __getcwd(buf, max) getcwd (buf, max, 0)
  65 #  else
  66 #   define __getcwd getcwd
  67 #  endif
  68 # else
  69 #  define __getcwd(buf, max) getwd (buf)
  70 # endif
  71 # define __readlink readlink
  72 # define __set_errno(e) errno = (e)
  73 # ifndef MAXSYMLINKS
  74 #  ifdef SYMLOOP_MAX
  75 #   define MAXSYMLINKS SYMLOOP_MAX
  76 #  else
  77 #   define MAXSYMLINKS 20
  78 #  endif
  79 # endif
  80 #endif
  81
  82 #ifndef DOUBLE_SLASH_IS_DISTINCT_ROOT
  83 # define DOUBLE_SLASH_IS_DISTINCT_ROOT 0
  84 #endif
  85
  86 /* Define this independently so that stdint.h is not a prerequisite.  */
  87 #ifndef SIZE_MAX
  88 # define SIZE_MAX ((size_t) -1)
  89 #endif
  90
  91 #if !FUNC_REALPATH_WORKS || defined _LIBC
  92
  93 static void
  94 alloc_failed (void)
  95 {
  96 #if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
  97   /* Avoid errno problem without using the malloc or realloc modules; see:
  98      http://lists.gnu.org/archive/html/bug-gnulib/2016-08/msg00025.html  */
  99   errno = ENOMEM;
 100 #endif
 101 }
 102
 103 /* Return the canonical absolute name of file NAME.  A canonical name
 104    does not contain any ".", ".." components nor any repeated path
 105    separators ('/') or symlinks.  All path components must exist.  If
 106    RESOLVED is null, the result is malloc'd; otherwise, if the
 107    canonical name is PATH_MAX chars or more, returns null with 'errno'
 108    set to ENAMETOOLONG; if the name fits in fewer than PATH_MAX chars,
 109    returns the name in RESOLVED.  If the name cannot be resolved and
 110    RESOLVED is non-NULL, it contains the path of the first component
 111    that cannot be resolved.  If the path can be resolved, RESOLVED
 112    holds the same value as the value returned.  */
 113
 114 char *
 115 __realpath (const char *name, char *resolved)
 116 {
 117   char *rpath, *dest, *extra_buf = NULL;
 118   const char *start, *end, *rpath_limit;
 119   long int path_max;
 120   int num_links = 0;
 121   size_t prefix_len;
 122
 123   if (name == NULL)
 124     {
 125       /* As per Single Unix Specification V2 we must return an error if
 126          either parameter is a null pointer.  We extend this to allow
 127          the RESOLVED parameter to be NULL in case the we are expected to
 128          allocate the room for the return value.  */
 129       __set_errno (EINVAL);
 130       return NULL;
 131     }
 132
 133   if (name[0] == '\0')
 134     {
 135       /* As per Single Unix Specification V2 we must return an error if
 136          the name argument points to an empty string.  */
 137       __set_errno (ENOENT);
 138       return NULL;
 139     }
 140
 141 #ifdef PATH_MAX
 142   path_max = PATH_MAX;
 143 #else
 144   path_max = pathconf (name, _PC_PATH_MAX);
 145   if (path_max <= 0)
 146     path_max = 8192;
 147 #endif
 148
 149   if (resolved == NULL)
 150     {
 151       rpath = malloc (path_max);
 152       if (rpath == NULL)
 153         {
 154           alloc_failed ();
 155           return NULL;
 156         }
 157     }
 158   else
 159     rpath = resolved;
 160   rpath_limit = rpath + path_max;
 161
 162   /* This is always zero for Posix hosts, but can be 2 for MS-Windows
 163      and MS-DOS X:/foo/bar file names.  */
 164   prefix_len = FILE_SYSTEM_PREFIX_LEN (name);
 165
 166   if (!IS_ABSOLUTE_FILE_NAME (name))
 167     {
 168       if (!__getcwd (rpath, path_max))
 169         {
 170           rpath[0] = '\0';
 171           goto error;
 172         }
 173       dest = strchr (rpath, '\0');
 174       start = name;
 175       prefix_len = FILE_SYSTEM_PREFIX_LEN (rpath);
 176     }
 177   else
 178     {
 179       dest = rpath;
 180       if (prefix_len)
 181         {
 182           memcpy (rpath, name, prefix_len);
 183           dest += prefix_len;
 184         }
 185       *dest++ = '/';
 186       if (DOUBLE_SLASH_IS_DISTINCT_ROOT)
 187         {
 188           if (ISSLASH (name[1]) && !ISSLASH (name[2]) && !prefix_len)
 189             *dest++ = '/';
 190           *dest = '\0';
 191         }
 192       start = name + prefix_len;
 193     }
 194
 195   for (end = start; *start; start = end)
 196     {
 197 #ifdef _LIBC
 198       struct stat64 st;
 199 #else
 200       struct stat st;
 201 #endif
 202
 203       /* Skip sequence of multiple path-separators.  */
 204       while (ISSLASH (*start))
 205         ++start;
 206
 207       /* Find end of path component.  */
 208       for (end = start; *end && !ISSLASH (*end); ++end)
 209         /* Nothing.  */;
 210
 211       if (end - start == 0)
 212         break;
 213       else if (end - start == 1 && start[0] == '.')
 214         /* nothing */;
 215       else if (end - start == 2 && start[0] == '.' && start[1] == '.')
 216         {
 217           /* Back up to previous component, ignore if at root already.  */
 218           if (dest > rpath + prefix_len + 1)
 219             for (--dest; dest > rpath && !ISSLASH (dest[-1]); --dest)
 220               continue;
 221           if (DOUBLE_SLASH_IS_DISTINCT_ROOT
 222               && dest == rpath + 1 && !prefix_len
 223               && ISSLASH (*dest) && !ISSLASH (dest[1]))
 224             dest++;
 225         }
 226       else
 227         {
 228           size_t new_size;
 229
 230           if (!ISSLASH (dest[-1]))
 231             *dest++ = '/';
 232
 233           if (dest + (end - start) >= rpath_limit)
 234             {
 235               ptrdiff_t dest_offset = dest - rpath;
 236               char *new_rpath;
 237
 238               if (resolved)
 239                 {
 240                   __set_errno (ENAMETOOLONG);
 241                   if (dest > rpath + prefix_len + 1)
 242                     dest--;
 243                   *dest = '\0';
 244                   goto error;
 245                 }
 246               new_size = rpath_limit - rpath;
 247               if (end - start + 1 > path_max)
 248                 new_size += end - start + 1;
 249               else
 250                 new_size += path_max;
 251               new_rpath = (char *) realloc (rpath, new_size);
 252               if (new_rpath == NULL)
 253                 {
 254                   alloc_failed ();
 255                   goto error;
 256                 }
 257               rpath = new_rpath;
 258               rpath_limit = rpath + new_size;
 259
 260               dest = rpath + dest_offset;
 261             }
 262
 263 #ifdef _LIBC
 264           dest = __mempcpy (dest, start, end - start);
 265 #else
 266           memcpy (dest, start, end - start);
 267           dest += end - start;
 268 #endif
 269           *dest = '\0';
 270
 271 #ifdef _LIBC
 272           if (__lxstat64 (_STAT_VER, rpath, &st) < 0)
 273 #else
 274           if (lstat (rpath, &st) < 0)
 275 #endif
 276             goto error;
 277
 278           if (S_ISLNK (st.st_mode))
 279             {
 280               char *buf;
 281               size_t len;
 282               ssize_t n;
 283
 284               if (++num_links > MAXSYMLINKS)
 285                 {
 286                   __set_errno (ELOOP);
 287                   goto error;
 288                 }
 289
 290               buf = malloca (path_max);
 291               if (!buf)
 292                 {
 293                   __set_errno (ENOMEM);
 294                   goto error;
 295                 }
 296
 297               n = __readlink (rpath, buf, path_max - 1);
 298               if (n < 0)
 299                 {
 300                   int saved_errno = errno;
 301                   freea (buf);
 302                   __set_errno (saved_errno);
 303                   goto error;
 304                 }
 305               buf[n] = '\0';
 306
 307               if (!extra_buf)
 308                 {
 309                   extra_buf = malloca (path_max);
 310                   if (!extra_buf)
 311                     {
 312                       freea (buf);
 313                       __set_errno (ENOMEM);
 314                       goto error;
 315                     }
 316                 }
 317
 318               len = strlen (end);
 319               /* Check that n + len + 1 doesn't overflow and is <= path_max. */
 320               if (n >= SIZE_MAX - len || n + len >= path_max)
 321                 {
 322                   freea (buf);
 323                   __set_errno (ENAMETOOLONG);
 324                   goto error;
 325                 }
 326
 327               /* Careful here, end may be a pointer into extra_buf... */
 328               memmove (&extra_buf[n], end, len + 1);
 329               name = end = memcpy (extra_buf, buf, n);
 330
 331               if (IS_ABSOLUTE_FILE_NAME (buf))
 332                 {
 333                   size_t pfxlen = FILE_SYSTEM_PREFIX_LEN (buf);
 334
 335                   if (pfxlen)
 336                     memcpy (rpath, buf, pfxlen);
 337                   dest = rpath + pfxlen;
 338                   *dest++ = '/'; /* It's an absolute symlink */
 339                   if (DOUBLE_SLASH_IS_DISTINCT_ROOT)
 340                     {
 341                       if (ISSLASH (buf[1]) && !ISSLASH (buf[2]) && !pfxlen)
 342                         *dest++ = '/';
 343                       *dest = '\0';
 344                     }
 345                   /* Install the new prefix to be in effect hereafter.  */
 346                   prefix_len = pfxlen;
 347                 }
 348               else
 349                 {
 350                   /* Back up to previous component, ignore if at root
 351                      already: */
 352                   if (dest > rpath + prefix_len + 1)
 353                     for (--dest; dest > rpath && !ISSLASH (dest[-1]); --dest)
 354                       continue;
 355                   if (DOUBLE_SLASH_IS_DISTINCT_ROOT && dest == rpath + 1
 356                       && ISSLASH (*dest) && !ISSLASH (dest[1]) && !prefix_len)
 357                     dest++;
 358                 }
 359             }
 360           else if (!S_ISDIR (st.st_mode) && *end != '\0')
 361             {
 362               __set_errno (ENOTDIR);
 363               goto error;
 364             }
 365         }
 366     }
 367   if (dest > rpath + prefix_len + 1 && ISSLASH (dest[-1]))
 368     --dest;
 369   if (DOUBLE_SLASH_IS_DISTINCT_ROOT && dest == rpath + 1 && !prefix_len
 370       && ISSLASH (*dest) && !ISSLASH (dest[1]))
 371     dest++;
 372   *dest = '\0';
 373
 374   if (extra_buf)
 375     freea (extra_buf);
 376
 377   return rpath;
 378
 379 error:
 380   {
 381     int saved_errno = errno;
 382     if (extra_buf)
 383       freea (extra_buf);
 384     if (resolved == NULL)
 385       free (rpath);
 386     __set_errno (saved_errno);
 387   }
 388   return NULL;
 389 }
 390 versioned_symbol (libc, __realpath, realpath, GLIBC_2_3);
 391 #endif /* !FUNC_REALPATH_WORKS || defined _LIBC */
 392
 393
 394 #if SHLIB_COMPAT(libc, GLIBC_2_0, GLIBC_2_3)
 395 char *
 396 attribute_compat_text_section
 397 __old_realpath (const char *name, char *resolved)
 398 {
 399   if (resolved == NULL)
 400     {
 401       __set_errno (EINVAL);
 402       return NULL;
 403     }
 404
 405   return __realpath (name, resolved);
 406 }
 407 compat_symbol (libc, __old_realpath, realpath, GLIBC_2_0);
 408 #endif
 409
 410
 411 char *
 412 __canonicalize_file_name (const char *name)
 413 {
 414   return __realpath (name, NULL);
 415 }
 416 weak_alias (__canonicalize_file_name, canonicalize_file_name)
 417
 418 #else
 419
 420 /* This declaration is solely to ensure that after preprocessing
 421    this file is never empty.  */
 422 typedef int dummy;
 423
 424 #endif