lib/canonicalize-lgpl.c

   1 /* Return the canonical absolute name of a given file.
   2    Copyright (C) 1996-2019 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 <https://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 #  if defined VMS && !defined getcwd
  63     /* We want the directory in Unix syntax, not in VMS syntax.
  64        The gnulib override of 'getcwd' takes 2 arguments; the original VMS
  65        'getcwd' takes 3 arguments.  */
  66 #   define __getcwd(buf, max) getcwd (buf, max, 0)
  67 #  else
  68 #   define __getcwd getcwd
  69 #  endif
  70 # else
  71 #  define __getcwd(buf, max) getwd (buf)
  72 # endif
  73 # define __readlink readlink
  74 # define __set_errno(e) errno = (e)
  75 # ifndef MAXSYMLINKS
  76 #  ifdef SYMLOOP_MAX
  77 #   define MAXSYMLINKS SYMLOOP_MAX
  78 #  else
  79 #   define MAXSYMLINKS 20
  80 #  endif
  81 # endif
  82 #endif
  83
  84 #ifndef DOUBLE_SLASH_IS_DISTINCT_ROOT
  85 # define DOUBLE_SLASH_IS_DISTINCT_ROOT 0
  86 #endif
  87
  88 /* Define this independently so that stdint.h is not a prerequisite.  */
  89 #ifndef SIZE_MAX
  90 # define SIZE_MAX ((size_t) -1)
  91 #endif
  92
  93 #if !FUNC_REALPATH_WORKS || defined _LIBC
  94
  95 static void
  96 alloc_failed (void)
  97 {
  98 #if defined _WIN32 && ! defined __CYGWIN__
  99   /* Avoid errno problem without using the malloc or realloc modules; see:
 100      https://lists.gnu.org/r/bug-gnulib/2016-08/msg00025.html  */
 101   errno = ENOMEM;
 102 #endif
 103 }
 104
 105 /* Return the canonical absolute name of file NAME.  A canonical name
 106    does not contain any ".", ".." components nor any repeated path
 107    separators ('/') or symlinks.  All path components must exist.  If
 108    RESOLVED is null, the result is malloc'd; otherwise, if the
 109    canonical name is PATH_MAX chars or more, returns null with 'errno'
 110    set to ENAMETOOLONG; if the name fits in fewer than PATH_MAX chars,
 111    returns the name in RESOLVED.  If the name cannot be resolved and
 112    RESOLVED is non-NULL, it contains the path of the first component
 113    that cannot be resolved.  If the path can be resolved, RESOLVED
 114    holds the same value as the value returned.  */
 115
 116 char *
 117 __realpath (const char *name, char *resolved)
 118 {
 119   char *rpath, *dest, *extra_buf = NULL;
 120   const char *start, *end, *rpath_limit;
 121   long int path_max;
 122   int num_links = 0;
 123   size_t prefix_len;
 124
 125   if (name == NULL)
 126     {
 127       /* As per Single Unix Specification V2 we must return an error if
 128          either parameter is a null pointer.  We extend this to allow
 129          the RESOLVED parameter to be NULL in case the we are expected to
 130          allocate the room for the return value.  */
 131       __set_errno (EINVAL);
 132       return NULL;
 133     }
 134
 135   if (name[0] == '\0')
 136     {
 137       /* As per Single Unix Specification V2 we must return an error if
 138          the name argument points to an empty string.  */
 139       __set_errno (ENOENT);
 140       return NULL;
 141     }
 142
 143 #ifdef PATH_MAX
 144   path_max = PATH_MAX;
 145 #else
 146   path_max = pathconf (name, _PC_PATH_MAX);
 147   if (path_max <= 0)
 148     path_max = 8192;
 149 #endif
 150
 151   if (resolved == NULL)
 152     {
 153       rpath = malloc (path_max);
 154       if (rpath == NULL)
 155         {
 156           alloc_failed ();
 157           return NULL;
 158         }
 159     }
 160   else
 161     rpath = resolved;
 162   rpath_limit = rpath + path_max;
 163
 164   /* This is always zero for Posix hosts, but can be 2 for MS-Windows
 165      and MS-DOS X:/foo/bar file names.  */
 166   prefix_len = FILE_SYSTEM_PREFIX_LEN (name);
 167
 168   if (!IS_ABSOLUTE_FILE_NAME (name))
 169     {
 170       if (!__getcwd (rpath, path_max))
 171         {
 172           rpath[0] = '\0';
 173           goto error;
 174         }
 175       dest = strchr (rpath, '\0');
 176       start = name;
 177       prefix_len = FILE_SYSTEM_PREFIX_LEN (rpath);
 178     }
 179   else
 180     {
 181       dest = rpath;
 182       if (prefix_len)
 183         {
 184           memcpy (rpath, name, prefix_len);
 185           dest += prefix_len;
 186         }
 187       *dest++ = '/';
 188       if (DOUBLE_SLASH_IS_DISTINCT_ROOT)
 189         {
 190           if (ISSLASH (name[1]) && !ISSLASH (name[2]) && !prefix_len)
 191             *dest++ = '/';
 192           *dest = '\0';
 193         }
 194       start = name + prefix_len;
 195     }
 196
 197   for (end = start; *start; start = end)
 198     {
 199 #ifdef _LIBC
 200       struct stat64 st;
 201 #else
 202       struct stat st;
 203 #endif
 204
 205       /* Skip sequence of multiple path-separators.  */
 206       while (ISSLASH (*start))
 207         ++start;
 208
 209       /* Find end of path component.  */
 210       for (end = start; *end && !ISSLASH (*end); ++end)
 211         /* Nothing.  */;
 212
 213       if (end - start == 0)
 214         break;
 215       else if (end - start == 1 && start[0] == '.')
 216         /* nothing */;
 217       else if (end - start == 2 && start[0] == '.' && start[1] == '.')
 218         {
 219           /* Back up to previous component, ignore if at root already.  */
 220           if (dest > rpath + prefix_len + 1)
 221             for (--dest; dest > rpath && !ISSLASH (dest[-1]); --dest)
 222               continue;
 223           if (DOUBLE_SLASH_IS_DISTINCT_ROOT
 224               && dest == rpath + 1 && !prefix_len
 225               && ISSLASH (*dest) && !ISSLASH (dest[1]))
 226             dest++;
 227         }
 228       else
 229         {
 230           size_t new_size;
 231
 232           if (!ISSLASH (dest[-1]))
 233             *dest++ = '/';
 234
 235           if (dest + (end - start) >= rpath_limit)
 236             {
 237               ptrdiff_t dest_offset = dest - rpath;
 238               char *new_rpath;
 239
 240               if (resolved)
 241                 {
 242                   __set_errno (ENAMETOOLONG);
 243                   if (dest > rpath + prefix_len + 1)
 244                     dest--;
 245                   *dest = '\0';
 246                   goto error;
 247                 }
 248               new_size = rpath_limit - rpath;
 249               if (end - start + 1 > path_max)
 250                 new_size += end - start + 1;
 251               else
 252                 new_size += path_max;
 253               new_rpath = (char *) realloc (rpath, new_size);
 254               if (new_rpath == NULL)
 255                 {
 256                   alloc_failed ();
 257                   goto error;
 258                 }
 259               rpath = new_rpath;
 260               rpath_limit = rpath + new_size;
 261
 262               dest = rpath + dest_offset;
 263             }
 264
 265 #ifdef _LIBC
 266           dest = __mempcpy (dest, start, end - start);
 267 #else
 268           memcpy (dest, start, end - start);
 269           dest += end - start;
 270 #endif
 271           *dest = '\0';
 272
 273           /* FIXME: if lstat fails with errno == EOVERFLOW,
 274              the entry exists.  */
 275 #ifdef _LIBC
 276           if (__lxstat64 (_STAT_VER, rpath, &st) < 0)
 277 #else
 278           if (lstat (rpath, &st) < 0)
 279 #endif
 280             goto error;
 281
 282           if (S_ISLNK (st.st_mode))
 283             {
 284               char *buf;
 285               size_t len;
 286               ssize_t n;
 287
 288               if (++num_links > MAXSYMLINKS)
 289                 {
 290                   __set_errno (ELOOP);
 291                   goto error;
 292                 }
 293
 294               buf = malloca (path_max);
 295               if (!buf)
 296                 {
 297                   __set_errno (ENOMEM);
 298                   goto error;
 299                 }
 300
 301               n = __readlink (rpath, buf, path_max - 1);
 302               if (n < 0)
 303                 {
 304                   int saved_errno = errno;
 305                   freea (buf);
 306                   __set_errno (saved_errno);
 307                   goto error;
 308                 }
 309               buf[n] = '\0';
 310
 311               if (!extra_buf)
 312                 {
 313                   extra_buf = malloca (path_max);
 314                   if (!extra_buf)
 315                     {
 316                       freea (buf);
 317                       __set_errno (ENOMEM);
 318                       goto error;
 319                     }
 320                 }
 321
 322               len = strlen (end);
 323               /* Check that n + len + 1 doesn't overflow and is <= path_max. */
 324               if (n >= SIZE_MAX - len || n + len >= path_max)
 325                 {
 326                   freea (buf);
 327                   __set_errno (ENAMETOOLONG);
 328                   goto error;
 329                 }
 330
 331               /* Careful here, end may be a pointer into extra_buf... */
 332               memmove (&extra_buf[n], end, len + 1);
 333               name = end = memcpy (extra_buf, buf, n);
 334
 335               if (IS_ABSOLUTE_FILE_NAME (buf))
 336                 {
 337                   size_t pfxlen = FILE_SYSTEM_PREFIX_LEN (buf);
 338
 339                   if (pfxlen)
 340                     memcpy (rpath, buf, pfxlen);
 341                   dest = rpath + pfxlen;
 342                   *dest++ = '/'; /* It's an absolute symlink */
 343                   if (DOUBLE_SLASH_IS_DISTINCT_ROOT)
 344                     {
 345                       if (ISSLASH (buf[1]) && !ISSLASH (buf[2]) && !pfxlen)
 346                         *dest++ = '/';
 347                       *dest = '\0';
 348                     }
 349                   /* Install the new prefix to be in effect hereafter.  */
 350                   prefix_len = pfxlen;
 351                 }
 352               else
 353                 {
 354                   /* Back up to previous component, ignore if at root
 355                      already: */
 356                   if (dest > rpath + prefix_len + 1)
 357                     for (--dest; dest > rpath && !ISSLASH (dest[-1]); --dest)
 358                       continue;
 359                   if (DOUBLE_SLASH_IS_DISTINCT_ROOT && dest == rpath + 1
 360                       && ISSLASH (*dest) && !ISSLASH (dest[1]) && !prefix_len)
 361                     dest++;
 362                 }
 363             }
 364           else if (!S_ISDIR (st.st_mode) && *end != '\0')
 365             {
 366               __set_errno (ENOTDIR);
 367               goto error;
 368             }
 369         }
 370     }
 371   if (dest > rpath + prefix_len + 1 && ISSLASH (dest[-1]))
 372     --dest;
 373   if (DOUBLE_SLASH_IS_DISTINCT_ROOT && dest == rpath + 1 && !prefix_len
 374       && ISSLASH (*dest) && !ISSLASH (dest[1]))
 375     dest++;
 376   *dest = '\0';
 377
 378   if (extra_buf)
 379     freea (extra_buf);
 380
 381   return rpath;
 382
 383 error:
 384   {
 385     int saved_errno = errno;
 386     if (extra_buf)
 387       freea (extra_buf);
 388     if (resolved == NULL)
 389       free (rpath);
 390     __set_errno (saved_errno);
 391   }
 392   return NULL;
 393 }
 394 versioned_symbol (libc, __realpath, realpath, GLIBC_2_3);
 395 #endif /* !FUNC_REALPATH_WORKS || defined _LIBC */
 396
 397
 398 #if SHLIB_COMPAT(libc, GLIBC_2_0, GLIBC_2_3)
 399 char *
 400 attribute_compat_text_section
 401 __old_realpath (const char *name, char *resolved)
 402 {
 403   if (resolved == NULL)
 404     {
 405       __set_errno (EINVAL);
 406       return NULL;
 407     }
 408
 409   return __realpath (name, resolved);
 410 }
 411 compat_symbol (libc, __old_realpath, realpath, GLIBC_2_0);
 412 #endif
 413
 414
 415 char *
 416 __canonicalize_file_name (const char *name)
 417 {
 418   return __realpath (name, NULL);
 419 }
 420 weak_alias (__canonicalize_file_name, canonicalize_file_name)
 421
 422 #else
 423
 424 /* This declaration is solely to ensure that after preprocessing
 425    this file is never empty.  */
 426 typedef int dummy;
 427
 428 #endif