lib/canonicalize-lgpl.c

   1 /* Return the canonical absolute name of a given file.
   2    Copyright (C) 1996-2020 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 "filename.h"
  55 # if defined _WIN32 && !defined __CYGWIN__
  56 #  define __getcwd _getcwd
  57 # elif HAVE_GETCWD
  58 #  if IN_RELOCWRAPPER
  59     /* When building the relocatable program wrapper, use the system's getcwd
  60        function, not the gnulib override, otherwise we would get a link error.
  61      */
  62 #   undef getcwd
  63 #  endif
  64 #  if defined VMS && !defined getcwd
  65     /* We want the directory in Unix syntax, not in VMS syntax.
  66        The gnulib override of 'getcwd' takes 2 arguments; the original VMS
  67        'getcwd' takes 3 arguments.  */
  68 #   define __getcwd(buf, max) getcwd (buf, max, 0)
  69 #  else
  70 #   define __getcwd getcwd
  71 #  endif
  72 # else
  73 #  define __getcwd(buf, max) getwd (buf)
  74 # endif
  75 # define __readlink readlink
  76 # define __set_errno(e) errno = (e)
  77 # ifndef MAXSYMLINKS
  78 #  ifdef SYMLOOP_MAX
  79 #   define MAXSYMLINKS SYMLOOP_MAX
  80 #  else
  81 #   define MAXSYMLINKS 20
  82 #  endif
  83 # endif
  84 #endif
  85
  86 #ifndef DOUBLE_SLASH_IS_DISTINCT_ROOT
  87 # define DOUBLE_SLASH_IS_DISTINCT_ROOT 0
  88 #endif
  89
  90 /* Define this independently so that stdint.h is not a prerequisite.  */
  91 #ifndef SIZE_MAX
  92 # define SIZE_MAX ((size_t) -1)
  93 #endif
  94
  95 #if !FUNC_REALPATH_WORKS || defined _LIBC
  96
  97 static void
  98 alloc_failed (void)
  99 {
 100 #if defined _WIN32 && ! defined __CYGWIN__
 101   /* Avoid errno problem without using the malloc or realloc modules; see:
 102      https://lists.gnu.org/r/bug-gnulib/2016-08/msg00025.html  */
 103   errno = ENOMEM;
 104 #endif
 105 }
 106
 107 /* Return the canonical absolute name of file NAME.  A canonical name
 108    does not contain any ".", ".." components nor any repeated path
 109    separators ('/') or symlinks.  All path components must exist.  If
 110    RESOLVED is null, the result is malloc'd; otherwise, if the
 111    canonical name is PATH_MAX chars or more, returns null with 'errno'
 112    set to ENAMETOOLONG; if the name fits in fewer than PATH_MAX chars,
 113    returns the name in RESOLVED.  If the name cannot be resolved and
 114    RESOLVED is non-NULL, it contains the path of the first component
 115    that cannot be resolved.  If the path can be resolved, RESOLVED
 116    holds the same value as the value returned.  */
 117
 118 char *
 119 __realpath (const char *name, char *resolved)
 120 {
 121   char *rpath, *dest, *extra_buf = NULL;
 122   const char *start, *end, *rpath_limit;
 123   long int path_max;
 124   int num_links = 0;
 125   size_t prefix_len;
 126
 127   if (name == NULL)
 128     {
 129       /* As per Single Unix Specification V2 we must return an error if
 130          either parameter is a null pointer.  We extend this to allow
 131          the RESOLVED parameter to be NULL in case the we are expected to
 132          allocate the room for the return value.  */
 133       __set_errno (EINVAL);
 134       return NULL;
 135     }
 136
 137   if (name[0] == '\0')
 138     {
 139       /* As per Single Unix Specification V2 we must return an error if
 140          the name argument points to an empty string.  */
 141       __set_errno (ENOENT);
 142       return NULL;
 143     }
 144
 145 #ifdef PATH_MAX
 146   path_max = PATH_MAX;
 147 #else
 148   path_max = pathconf (name, _PC_PATH_MAX);
 149   if (path_max <= 0)
 150     path_max = 8192;
 151 #endif
 152
 153   if (resolved == NULL)
 154     {
 155       rpath = malloc (path_max);
 156       if (rpath == NULL)
 157         {
 158           alloc_failed ();
 159           return NULL;
 160         }
 161     }
 162   else
 163     rpath = resolved;
 164   rpath_limit = rpath + path_max;
 165
 166   /* This is always zero for Posix hosts, but can be 2 for MS-Windows
 167      and MS-DOS X:/foo/bar file names.  */
 168   prefix_len = FILE_SYSTEM_PREFIX_LEN (name);
 169
 170   if (!IS_ABSOLUTE_FILE_NAME (name))
 171     {
 172       if (!__getcwd (rpath, path_max))
 173         {
 174           rpath[0] = '\0';
 175           goto error;
 176         }
 177       dest = strchr (rpath, '\0');
 178       start = name;
 179       prefix_len = FILE_SYSTEM_PREFIX_LEN (rpath);
 180     }
 181   else
 182     {
 183       dest = rpath;
 184       if (prefix_len)
 185         {
 186           memcpy (rpath, name, prefix_len);
 187           dest += prefix_len;
 188         }
 189       *dest++ = '/';
 190       if (DOUBLE_SLASH_IS_DISTINCT_ROOT)
 191         {
 192           if (ISSLASH (name[1]) && !ISSLASH (name[2]) && !prefix_len)
 193             *dest++ = '/';
 194           *dest = '\0';
 195         }
 196       start = name + prefix_len;
 197     }
 198
 199   for (end = start; *start; start = end)
 200     {
 201 #ifdef _LIBC
 202       struct stat64 st;
 203 #else
 204       struct stat st;
 205 #endif
 206
 207       /* Skip sequence of multiple path-separators.  */
 208       while (ISSLASH (*start))
 209         ++start;
 210
 211       /* Find end of path component.  */
 212       for (end = start; *end && !ISSLASH (*end); ++end)
 213         /* Nothing.  */;
 214
 215       if (end - start == 0)
 216         break;
 217       else if (end - start == 1 && start[0] == '.')
 218         /* nothing */;
 219       else if (end - start == 2 && start[0] == '.' && start[1] == '.')
 220         {
 221           /* Back up to previous component, ignore if at root already.  */
 222           if (dest > rpath + prefix_len + 1)
 223             for (--dest; dest > rpath && !ISSLASH (dest[-1]); --dest)
 224               continue;
 225           if (DOUBLE_SLASH_IS_DISTINCT_ROOT
 226               && dest == rpath + 1 && !prefix_len
 227               && ISSLASH (*dest) && !ISSLASH (dest[1]))
 228             dest++;
 229         }
 230       else
 231         {
 232           size_t new_size;
 233
 234           if (!ISSLASH (dest[-1]))
 235             *dest++ = '/';
 236
 237           if (rpath_limit - dest <= end - start)
 238             {
 239               ptrdiff_t dest_offset = dest - rpath;
 240               char *new_rpath;
 241
 242               if (resolved)
 243                 {
 244                   __set_errno (ENAMETOOLONG);
 245                   if (dest > rpath + prefix_len + 1)
 246                     dest--;
 247                   *dest = '\0';
 248                   goto error;
 249                 }
 250               new_size = rpath_limit - rpath;
 251               if (end - start + 1 > path_max)
 252                 new_size += end - start + 1;
 253               else
 254                 new_size += path_max;
 255               new_rpath = (char *) realloc (rpath, new_size);
 256               if (new_rpath == NULL)
 257                 {
 258                   alloc_failed ();
 259                   goto error;
 260                 }
 261               rpath = new_rpath;
 262               rpath_limit = rpath + new_size;
 263
 264               dest = rpath + dest_offset;
 265             }
 266
 267 #ifdef _LIBC
 268           dest = __mempcpy (dest, start, end - start);
 269 #else
 270           memcpy (dest, start, end - start);
 271           dest += end - start;
 272 #endif
 273           *dest = '\0';
 274
 275           /* FIXME: if lstat fails with errno == EOVERFLOW,
 276              the entry exists.  */
 277 #ifdef _LIBC
 278           if (__lxstat64 (_STAT_VER, rpath, &st) < 0)
 279 #else
 280           if (lstat (rpath, &st) < 0)
 281 #endif
 282             goto error;
 283
 284           if (S_ISLNK (st.st_mode))
 285             {
 286               char *buf;
 287               size_t len;
 288               ssize_t n;
 289
 290               if (++num_links > MAXSYMLINKS)
 291                 {
 292                   __set_errno (ELOOP);
 293                   goto error;
 294                 }
 295
 296               if (!extra_buf)
 297                 {
 298                   extra_buf = malloca (2 * path_max);
 299                   if (!extra_buf)
 300                     {
 301                       alloc_failed ();
 302                       goto error;
 303                     }
 304                 }
 305               buf = extra_buf + path_max;
 306
 307               n = __readlink (rpath, buf, path_max - 1);
 308               if (n < 0)
 309                 goto error;
 310               buf[n] = '\0';
 311
 312               len = strlen (end);
 313               /* Check that n + len + 1 doesn't overflow and is <= path_max. */
 314               if (n >= SIZE_MAX - len || n + len >= path_max)
 315                 {
 316                   __set_errno (ENAMETOOLONG);
 317                   goto error;
 318                 }
 319
 320               /* Careful here, end may be a pointer into extra_buf... */
 321               memmove (&extra_buf[n], end, len + 1);
 322               name = end = memcpy (extra_buf, buf, n);
 323
 324               if (IS_ABSOLUTE_FILE_NAME (buf))
 325                 {
 326                   size_t pfxlen = FILE_SYSTEM_PREFIX_LEN (buf);
 327
 328                   if (pfxlen)
 329                     memcpy (rpath, buf, pfxlen);
 330                   dest = rpath + pfxlen;
 331                   *dest++ = '/'; /* It's an absolute symlink */
 332                   if (DOUBLE_SLASH_IS_DISTINCT_ROOT)
 333                     {
 334                       if (ISSLASH (buf[1]) && !ISSLASH (buf[2]) && !pfxlen)
 335                         *dest++ = '/';
 336                       *dest = '\0';
 337                     }
 338                   /* Install the new prefix to be in effect hereafter.  */
 339                   prefix_len = pfxlen;
 340                 }
 341               else
 342                 {
 343                   /* Back up to previous component, ignore if at root
 344                      already: */
 345                   if (dest > rpath + prefix_len + 1)
 346                     for (--dest; dest > rpath && !ISSLASH (dest[-1]); --dest)
 347                       continue;
 348                   if (DOUBLE_SLASH_IS_DISTINCT_ROOT && dest == rpath + 1
 349                       && ISSLASH (*dest) && !ISSLASH (dest[1]) && !prefix_len)
 350                     dest++;
 351                 }
 352             }
 353           else if (!S_ISDIR (st.st_mode) && *end != '\0')
 354             {
 355               __set_errno (ENOTDIR);
 356               goto error;
 357             }
 358         }
 359     }
 360   if (dest > rpath + prefix_len + 1 && ISSLASH (dest[-1]))
 361     --dest;
 362   if (DOUBLE_SLASH_IS_DISTINCT_ROOT && dest == rpath + 1 && !prefix_len
 363       && ISSLASH (*dest) && !ISSLASH (dest[1]))
 364     dest++;
 365   *dest = '\0';
 366
 367   if (extra_buf)
 368     freea (extra_buf);
 369
 370   return rpath;
 371
 372 error:
 373   {
 374     int saved_errno = errno;
 375     if (extra_buf)
 376       freea (extra_buf);
 377     if (resolved == NULL)
 378       free (rpath);
 379     __set_errno (saved_errno);
 380   }
 381   return NULL;
 382 }
 383 versioned_symbol (libc, __realpath, realpath, GLIBC_2_3);
 384 #endif /* !FUNC_REALPATH_WORKS || defined _LIBC */
 385
 386
 387 #if SHLIB_COMPAT(libc, GLIBC_2_0, GLIBC_2_3)
 388 char *
 389 attribute_compat_text_section
 390 __old_realpath (const char *name, char *resolved)
 391 {
 392   if (resolved == NULL)
 393     {
 394       __set_errno (EINVAL);
 395       return NULL;
 396     }
 397
 398   return __realpath (name, resolved);
 399 }
 400 compat_symbol (libc, __old_realpath, realpath, GLIBC_2_0);
 401 #endif
 402
 403
 404 char *
 405 __canonicalize_file_name (const char *name)
 406 {
 407   return __realpath (name, NULL);
 408 }
 409 weak_alias (__canonicalize_file_name, canonicalize_file_name)
 410
 411 #else
 412
 413 /* This declaration is solely to ensure that after preprocessing
 414    this file is never empty.  */
 415 typedef int dummy;
 416
 417 #endif