/*
   * AppArmor security module
   *
   * This file contains AppArmor function for pathnames
   *
   * Copyright (C) 1998-2008 Novell/SUSE
   * Copyright 2009-2010 Canonical Ltd.
   *
   * This program is free software; you can redistribute it and/or
   * modify it under the terms of the GNU General Public License as
   * published by the Free Software Foundation, version 2 of the
   * License.
   */
  
  #include <linux/magic.h>

  #include <linux/mount.h>
  #include <linux/namei.h>
  #include <linux/nsproxy.h>
  #include <linux/path.h>
  #include <linux/sched.h>
  #include <linux/slab.h>
  #include <linux/fs_struct.h>
  
  #include "include/apparmor.h"
  #include "include/path.h"
  #include "include/policy.h"
  
  
  /* modified from dcache.c */
  static int prepend(char **buffer, int buflen, const char *str, int namelen)
  {
  	buflen -= namelen;
  	if (buflen < 0)
  		return -ENAMETOOLONG;
  	*buffer -= namelen;
  	memcpy(*buffer, str, namelen);
  	return 0;
  }
  
  #define CHROOT_NSCONNECT (PATH_CHROOT_REL | PATH_CHROOT_NSCONNECT)
  
  /**
   * d_namespace_path - lookup a name associated with a given path
   * @path: path to lookup  (NOT NULL)
   * @buf:  buffer to store path to  (NOT NULL)
   * @buflen: length of @buf
   * @name: Returns - pointer for start of path name with in @buf (NOT NULL)
   * @flags: flags controlling path lookup
   *
   * Handle path name lookup.
   *
   * Returns: %0 else error code if path lookup fails
   *          When no error the path name is returned in @name which points to
   *          to a position in @buf
   */
  static int d_namespace_path(struct path *path, char *buf, int buflen,
  			    char **name, int flags)
  {

  	char *res;

  	int error = 0;
  	int connected = 1;

  	if (path->mnt->mnt_flags & MNT_INTERNAL) {
  		/* it's not mounted anywhere */
  		res = dentry_path(path->dentry, buf, buflen);
  		*name = res;
  		if (IS_ERR(res)) {
  			*name = buf;
  			return PTR_ERR(res);
  		}
  		if (path->dentry->d_sb->s_magic == PROC_SUPER_MAGIC &&
  		    strncmp(*name, "/sys/", 5) == 0) {
  			/* TODO: convert over to using a per namespace
  			 * control instead of hard coded /proc
  			 */
  			return prepend(name, *name - buf, "/proc", 5);
  		}
  		return 0;
  	}
  
  	/* resolve paths relative to chroot?*/

  	if (flags & PATH_CHROOT_REL) {

  		struct path root;

  		get_fs_root(current->fs, &root);

  		res = __d_path(path, &root, buf, buflen);
  		if (res && !IS_ERR(res)) {
  			/* everything's fine */
  			*name = res;
  			path_put(&root);
  			goto ok;
  		}
  		path_put(&root);
  		connected = 0;

  	}

  	res = d_absolute_path(path, buf, buflen);

  
  	*name = res;
  	/* handle error conditions - and still allow a partial path to
  	 * be returned.
  	 */
  	if (IS_ERR(res)) {
  		error = PTR_ERR(res);
  		*name = buf;
  		goto out;
  	}

  	if (!our_mnt(path->mnt))
  		connected = 0;

  ok:

  	/* Handle two cases:
  	 * 1. A deleted dentry && profile is not allowing mediation of deleted
  	 * 2. On some filesystems, newly allocated dentries appear to the
  	 *    security_path hooks as a deleted dentry except without an inode
  	 *    allocated.
  	 */
  	if (d_unlinked(path->dentry) && path->dentry->d_inode &&
  	    !(flags & PATH_MEDIATE_DELETED)) {

  			error = -ENOENT;
  			goto out;

  	}

  	/* If the path is not connected to the expected root,

  	 * check if it is a sysctl and handle specially else remove any
  	 * leading / that __d_path may have returned.
  	 * Unless
  	 *     specifically directed to connect the path,
  	 * OR
  	 *     if in a chroot and doing chroot relative paths and the path
  	 *     resolves to the namespace root (would be connected outside
  	 *     of chroot) and specifically directed to connect paths to
  	 *     namespace root.
  	 */
  	if (!connected) {

  		if (!(flags & PATH_CONNECT_PATH) &&

  			   !(((flags & CHROOT_NSCONNECT) == CHROOT_NSCONNECT) &&

  			     our_mnt(path->mnt))) {

  			/* disconnected path, don't return pathname starting
  			 * with '/'
  			 */
  			error = -ESTALE;
  			if (*res == '/')
  				*name = res + 1;
  		}
  	}
  
  out:

  	return error;
  }
  
  /**
   * get_name_to_buffer - get the pathname to a buffer ensure dir / is appended
   * @path: path to get name for  (NOT NULL)
   * @flags: flags controlling path lookup
   * @buffer: buffer to put name in  (NOT NULL)
   * @size: size of buffer
   * @name: Returns - contains position of path name in @buffer (NOT NULL)
   *
   * Returns: %0 else error on failure
   */
  static int get_name_to_buffer(struct path *path, int flags, char *buffer,
  			      int size, char **name)
  {
  	int adjust = (flags & PATH_IS_DIR) ? 1 : 0;
  	int error = d_namespace_path(path, buffer, size - adjust, name, flags);
  
  	if (!error && (flags & PATH_IS_DIR) && (*name)[1] != '\0')
  		/*
  		 * Append "/" to the pathname.  The root directory is a special
  		 * case; it already ends in slash.
  		 */
  		strcpy(&buffer[size - 2], "/");
  
  	return error;
  }
  
  /**
   * aa_get_name - compute the pathname of a file
   * @path: path the file  (NOT NULL)
   * @flags: flags controlling path name generation
   * @buffer: buffer that aa_get_name() allocated  (NOT NULL)
   * @name: Returns - the generated path name if !error (NOT NULL)
   *
   * @name is a pointer to the beginning of the pathname (which usually differs
   * from the beginning of the buffer), or NULL.  If there is an error @name
   * may contain a partial or invalid name that can be used for audit purposes,
   * but it can not be used for mediation.
   *
   * We need PATH_IS_DIR to indicate whether the file is a directory or not
   * because the file may not yet exist, and so we cannot check the inode's
   * file type.
   *
   * Returns: %0 else error code if could retrieve name
   */
  int aa_get_name(struct path *path, int flags, char **buffer, const char **name)
  {
  	char *buf, *str = NULL;
  	int size = 256;
  	int error;
  
  	*name = NULL;
  	*buffer = NULL;
  	for (;;) {
  		/* freed by caller */
  		buf = kmalloc(size, GFP_KERNEL);
  		if (!buf)
  			return -ENOMEM;
  
  		error = get_name_to_buffer(path, flags, buf, size, &str);
  		if (error != -ENAMETOOLONG)
  			break;
  
  		kfree(buf);
  		size <<= 1;
  		if (size > aa_g_path_max)
  			return -ENAMETOOLONG;
  	}
  	*buffer = buf;
  	*name = str;
  
  	return error;
  }