path: root/locale/findlocale.c

/* Copyright (C) 1996-2025 Free Software Foundation, Inc.
   This file is part of the GNU C Library.

   The GNU C Library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   The GNU C Library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with the GNU C Library; if not, see
   <https://www.gnu.org/licenses/>.  */

#include <assert.h>
#include <errno.h>
#include <locale.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#ifdef _POSIX_MAPPED_FILES
# include <sys/mman.h>
#endif

#include "localeinfo.h"
#include "../iconv/gconv_charset.h"
#include "../iconv/gconv_int.h"


#ifdef NL_CURRENT_INDIRECT
# define DEFINE_CATEGORY(category, category_name, items, a) \
extern struct __locale_data _nl_C_##category; \
weak_extern (_nl_C_##category)
# include "categories.def"
# undef	DEFINE_CATEGORY

/* Array indexed by category of pointers to _nl_C_CATEGORY slots.
   Elements are zero for categories whose data is never used.  */
struct __locale_data *const _nl_C[] attribute_hidden =
  {
# define DEFINE_CATEGORY(category, category_name, items, a) \
    [category] = &_nl_C_##category,
# include "categories.def"
# undef	DEFINE_CATEGORY
  };
#else
# define _nl_C		(_nl_C_locobj.__locales)
#endif


/* For each category we keep a list of records for the locale files
   which are somehow addressed.  */
struct loaded_l10nfile *_nl_locale_file_list[__LC_LAST];

const char _nl_default_locale_path[] attribute_hidden = COMPLOCALEDIR;

/* Checks if the name is actually present, that is, not NULL and not
   empty.  */
static inline int
name_present (const char *name)
{
  return name != NULL && name[0] != '\0';
}

/* Checks that the locale name neither extremely long, nor contains a
   ".." path component (to prevent directory traversal).  */
static inline int
valid_locale_name (const char *name)
{
  /* Not set.  */
  size_t namelen = strlen (name);
  /* Name too long.  The limit is arbitrary and prevents stack overflow
     issues later.  */
  if (__glibc_unlikely (namelen > 255))
    return 0;
  /* Directory traversal attempt.  */
  static const char slashdot[4] = {'/', '.', '.', '/'};
  if (__glibc_unlikely (__memmem (name, namelen,
				  slashdot, sizeof (slashdot)) != NULL))
    return 0;
  if (namelen == 2 && __glibc_unlikely (name[0] == '.' && name [1] == '.'))
    return 0;
  if (namelen >= 3
      && __glibc_unlikely (((name[0] == '.'
			     && name[1] == '.'
			     && name[2] == '/')
			    || (name[namelen - 3] == '/'
				&& name[namelen - 2] == '.'
				&& name[namelen - 1] == '.'))))
    return 0;
  /* If there is a slash in the name, it must start with one.  */
  if (__glibc_unlikely (memchr (name, '/', namelen) != NULL) && name[0] != '/')
    return 0;
  return 1;
}

struct __locale_data *
_nl_find_locale (const char *locale_path, size_t locale_path_len,
		 int category, const char **name)
{
  int mask;
  /* Name of the locale for this category.  */
  const char *cloc_name = *name;
  const char *language;
  const char *modifier;
  const char *territory;
  const char *codeset;
  const char *normalized_codeset;
  struct loaded_l10nfile *locale_file;

  if (cloc_name[0] == '\0')
    {
      /* The user decides which locale to use by setting environment
	 variables.  */
      cloc_name = getenv ("LC_ALL");
      if (!name_present (cloc_name))
	cloc_name = getenv (_nl_category_names_get (category));
      if (!name_present (cloc_name))
	cloc_name = getenv ("LANG");
      if (!name_present (cloc_name))
	cloc_name = _nl_C_name;
    }

  /* We used to fall back to the C locale if the name contains a slash
     character '/', but we now check for directory traversal in
     valid_locale_name, so this is no longer necessary.  */

  if (__builtin_expect (strcmp (cloc_name, _nl_C_name), 1) == 0
      || __builtin_expect (strcmp (cloc_name, _nl_POSIX_name), 1) == 0)
    {
      /* We need not load anything.  The needed data is contained in
	 the library itself.  */
      *name = _nl_C_name;
      return _nl_C[category];
    }
  else if (!valid_locale_name (cloc_name))
    {
      __set_errno (EINVAL);
      return NULL;
    }

  *name = cloc_name;

  /* We really have to load some data.  First we try the archive,
     but only if there was no LOCPATH environment variable specified.  */
  if (__glibc_likely (locale_path == NULL))
    {
      struct __locale_data *data
	= _nl_load_locale_from_archive (category, name);
      if (__glibc_likely (data != NULL))
	return data;

      /* Nothing in the archive with the given name.  Expanding it as
	 an alias and retry.  */
      cloc_name = _nl_expand_alias (*name);
      if (cloc_name != NULL)
	{
	  data = _nl_load_locale_from_archive (category, &cloc_name);
	  if (__builtin_expect (data != NULL, 1))