path: root/libmenu/canonicalize.c

/* Return the canonical absolute name of a given file.
 * Copyright (C) 1996-2001, 2002 Free Software Foundation, Inc.
 * This file is part of the GNU C Library.
 *
 * Copyright (C) 2002 Red Hat, Inc. (trivial port to GLib)
 *
 * 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, write to the Free
 * Software Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA.
 */

#include <config.h>

#include "canonicalize.h"

#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <limits.h>
#include <sys/param.h>
#include <sys/stat.h>
#include <errno.h>
#include <stddef.h>

#ifndef MAXSYMLINKS
#define MAXSYMLINKS sysconf(_SC_SYMLOOP_MAX)
#endif

/* Return the canonical absolute name of file NAME.  A canonical name
   does not contain any `.', `..' components nor any repeated path
   separators ('/') or symlinks.  All path components must exist.  If
   RESOLVED is null, the result is malloc'd; otherwise, if the
   canonical name is PATH_MAX chars or more, returns null with `errno'
   set to ENAMETOOLONG; if the name fits in fewer than PATH_MAX chars,
   returns the name in RESOLVED.  If the name cannot be resolved and
   RESOLVED is non-NULL, it contains the path of the first component
   that cannot be resolved.  If the path can be resolved, RESOLVED
   holds the same value as the value returned.  */

static char* menu_realpath(const char* name, char* resolved)
{
	char* rpath = NULL;
	char* dest = NULL;
	char* extra_buf = NULL;
	const char* start;
	const char* end;
	const char* rpath_limit;
	long int path_max;
	int num_links = 0;

	if (name == NULL)
	{
		/* As per Single Unix Specification V2 we must return an error if
		 * either parameter is a null pointer.  We extend this to allow
		 * the RESOLVED parameter to be NULL in case the we are expected to
		 * allocate the room for the return value.  */
		errno = EINVAL;
		return NULL;
	}

	if (name[0] == '\0')
	{
		/* As per Single Unix Specification V2 we must return an error if
		 * the name argument points to an empty string.  */
		errno = ENOENT;
		return NULL;
	}

	#ifdef PATH_MAX
		path_max = PATH_MAX;
	#else
		path_max = pathconf(name, _PC_PATH_MAX);

		if (path_max <= 0)
		{
			path_max = 1024;
		}
	#endif

	rpath = resolved ? g_alloca(path_max) : g_malloc(path_max);
	rpath_limit = rpath + path_max;

	if (name[0] != G_DIR_SEPARATOR)
	{
		if (!getcwd(rpath, path_max))
		{
			rpath[0] = '\0';
			goto error;
		}

		dest = strchr(rpath, '\0');
	}
	else
	{
		rpath[0] = G_DIR_SEPARATOR;
		dest = rpath + 1;
	}

	for (start = end = name; *start; start = end)
    {
		struct stat st;
		int n;

		/* Skip sequence of multiple path-separators.  */
		while (*start == G_DIR_SEPARATOR)
		{
			++start;
		}

		/* Find end of path component.  */
		for (end = start; *end && *end != G_DIR_SEPARATOR; ++end)
		{
			/* Nothing.  */;
		}

		if (end - start == 0)
		{
			break;
		}
		else if (end - start == 1 && start[0] == '.')
		{
			/* nothing */;
		}
		else if (end - start == 2 && start[0] == '.' && start[1] == '.')
        {
			/* Back up to previous component, ignore if at root already.  */
			if (dest > rpath + 1)
			{
				while ((--dest)[-1] != G_DIR_SEPARATOR)
				{
					/* Nothing.  */;
				}
			}
        }
		else
        {
			size_t new_size;

			if (dest[-1] != G_DIR_SEPARATOR)
			{
				*dest++ = G_DIR_SEPARATOR;
			}

			if (dest + (end - start) >= rpath_limit)
            {
				char* new_rpath;
				ptrdiff_t dest_offset = dest - rpath;

				if (resolved)
				{
					#ifdef ENAMETOOLONG
					  errno = ENAMETOOLONG;
					#else
					  /* Uh... just pick something */
					  errno = EINVAL;
					#endif

					if (dest > rpath + 1)
					{
						dest--;
					}

					*dest = '\0';
					goto error;
                }

				new_size = rpath_limit - rpath;

				if (end - start + 1 > path_max)
				{
					new_size += end - start + 1;
				}
				else
				{
					new_size += path_max;
				}

				new_rpath = (char*) realloc(rpath, new_size);

				if (new_rpath == NULL)
				{
					goto error;
				}

				rpath = new_rpath;
				rpath_limit = rpath + new_size;

				dest = rpath + dest_offset;
            }

			memcpy(dest, start, end - start);
			dest = dest + (end - start);
			*dest = '\0';

			if (stat(rpath, &st) < 0)
			{
				goto error;
			}

			if (S_ISLNK(st.st_mode))
			{
				char* buf = alloca(path_max);
				size_t len;

				if (++num_links > MAXSYMLINKS)
				{
					errno = ELOOP;
					goto error;
				}

				n = readlink(rpath, buf, path_max);

				if (n < 0)
				{
					goto error;
				}

				buf[n] = '\0';



				if (!extra_buf)
				{
					extra_buf = g_alloca(path_max);
				}

				len = strlen(end);

				if ((long int) (n + len) >= path_max)
                {
					#ifdef ENAMETOOLONG
					  errno = ENAMETOOLONG;
					#else
					  /* Uh... just pick something */
					  errno = EINVAL;
					#endif

					goto error;
                }

				/* Careful here, end may be a pointer into extra_buf... */
				g_memmove(&extra_buf[n], end, len + 1);
				name = end = memcpy(extra_buf, buf, n);

				if (buf[0] == G_DIR_SEPARATOR)
				{
					dest = rpath + 1;       /* It's an absolute symlink */
				}
				else
				{
					/* Back up to previous component, ignore if at root already: */
					if (dest > rpath + 1)
					{
						while ((--dest)[-1] != G_DIR_SEPARATOR)
						{
							/* Nothing.  */;
						}
					}
				}
            }
        }
    }

	if (dest > rpath + 1 && dest[-1] == G_DIR_SEPARATOR)
	{
		--dest;
	}

	*dest = '\0';

	return resolved ? memcpy(resolved, rpath, dest - rpath + 1) : rpath;

	error:

	if (resolved)
	{
		strcpy(resolved, rpath);
	}
	else
	{
		g_free(rpath);
	}

	return NULL;
}

char* menu_canonicalize_file_name(const char* name, gboolean allow_missing_basename)
{
	char* retval;

	retval = menu_realpath(name, NULL);

	/* We could avoid some system calls by using the second
	 * argument to realpath() instead of doing realpath
	 * all over again, but who cares really. we'll see if
	 * it's ever in a profile.
	 */
	if (allow_missing_basename && retval == NULL)
	{
		char* dirname;
		char* canonical_dirname;

		dirname = g_path_get_dirname(name);
		canonical_dirname = menu_realpath(dirname, NULL);
		g_free(dirname);

		if (canonical_dirname)
		{
			char* basename;

			basename = g_path_get_basename(name);
			retval = g_build_filename(canonical_dirname, basename, NULL);
			g_free(basename);
			g_free(canonical_dirname);
		}
	}

	return retval;
}