/* audit_fsnotify.c -- tracking inodes
   *
   * Copyright 2003-2009,2014-2015 Red Hat, Inc.
   * Copyright 2005 Hewlett-Packard Development Company, L.P.
   * Copyright 2005 IBM Corporation
   *
   * 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; either version 2 of the License, or
   * (at your option) any later version.
   *
   * This program 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 General Public License for more details.
   */
  
  #include <linux/kernel.h>
  #include <linux/audit.h>
  #include <linux/kthread.h>
  #include <linux/mutex.h>
  #include <linux/fs.h>
  #include <linux/fsnotify_backend.h>
  #include <linux/namei.h>
  #include <linux/netlink.h>
  #include <linux/sched.h>
  #include <linux/slab.h>
  #include <linux/security.h>
  #include "audit.h"
  
  /*
   * this mark lives on the parent directory of the inode in question.
   * but dev, ino, and path are about the child
   */
  struct audit_fsnotify_mark {
  	dev_t dev;		/* associated superblock device */
  	unsigned long ino;	/* associated inode number */
  	char *path;		/* insertion path */
  	struct fsnotify_mark mark; /* fsnotify mark on the inode */
  	struct audit_krule *rule;
  };
  
  /* fsnotify handle. */
  static struct fsnotify_group *audit_fsnotify_group;
  
  /* fsnotify events we care about. */
  #define AUDIT_FS_EVENTS (FS_MOVE | FS_CREATE | FS_DELETE | FS_DELETE_SELF |\
  			 FS_MOVE_SELF | FS_EVENT_ON_CHILD)
  
  static void audit_fsnotify_mark_free(struct audit_fsnotify_mark *audit_mark)
  {
  	kfree(audit_mark->path);
  	kfree(audit_mark);
  }
  
  static void audit_fsnotify_free_mark(struct fsnotify_mark *mark)
  {
  	struct audit_fsnotify_mark *audit_mark;
  
  	audit_mark = container_of(mark, struct audit_fsnotify_mark, mark);
  	audit_fsnotify_mark_free(audit_mark);
  }
  
  char *audit_mark_path(struct audit_fsnotify_mark *mark)
  {
  	return mark->path;
  }
  
  int audit_mark_compare(struct audit_fsnotify_mark *mark, unsigned long ino, dev_t dev)
  {
  	if (mark->ino == AUDIT_INO_UNSET)
  		return 0;
  	return (mark->ino == ino) && (mark->dev == dev);
  }
  
  static void audit_update_mark(struct audit_fsnotify_mark *audit_mark,

  			     const struct inode *inode)

  {
  	audit_mark->dev = inode ? inode->i_sb->s_dev : AUDIT_DEV_UNSET;
  	audit_mark->ino = inode ? inode->i_ino : AUDIT_INO_UNSET;
  }
  
  struct audit_fsnotify_mark *audit_alloc_mark(struct audit_krule *krule, char *pathname, int len)
  {
  	struct audit_fsnotify_mark *audit_mark;
  	struct path path;
  	struct dentry *dentry;
  	struct inode *inode;
  	int ret;
  
  	if (pathname[0] != '/' || pathname[len-1] == '/')
  		return ERR_PTR(-EINVAL);
  
  	dentry = kern_path_locked(pathname, &path);
  	if (IS_ERR(dentry))
  		return (void *)dentry; /* returning an error */
  	inode = path.dentry->d_inode;

  	inode_unlock(inode);

  
  	audit_mark = kzalloc(sizeof(*audit_mark), GFP_KERNEL);
  	if (unlikely(!audit_mark)) {
  		audit_mark = ERR_PTR(-ENOMEM);
  		goto out;
  	}

  	fsnotify_init_mark(&audit_mark->mark, audit_fsnotify_group);

  	audit_mark->mark.mask = AUDIT_FS_EVENTS;
  	audit_mark->path = pathname;
  	audit_update_mark(audit_mark, dentry->d_inode);
  	audit_mark->rule = krule;

  	ret = fsnotify_add_mark(&audit_mark->mark, inode, NULL, true);

  	if (ret < 0) {

  		fsnotify_put_mark(&audit_mark->mark);

  		audit_mark = ERR_PTR(ret);
  	}
  out:
  	dput(dentry);
  	path_put(&path);
  	return audit_mark;
  }
  
  static void audit_mark_log_rule_change(struct audit_fsnotify_mark *audit_mark, char *op)
  {
  	struct audit_buffer *ab;
  	struct audit_krule *rule = audit_mark->rule;
  
  	if (!audit_enabled)
  		return;
  	ab = audit_log_start(NULL, GFP_NOFS, AUDIT_CONFIG_CHANGE);
  	if (unlikely(!ab))
  		return;

  	audit_log_format(ab, "auid=%u ses=%u op=%s",

  			 from_kuid(&init_user_ns, audit_get_loginuid(current)),

  			 audit_get_sessionid(current), op);

  	audit_log_format(ab, " path=");
  	audit_log_untrustedstring(ab, audit_mark->path);
  	audit_log_key(ab, rule->filterkey);
  	audit_log_format(ab, " list=%d res=1", rule->listnr);
  	audit_log_end(ab);
  }
  
  void audit_remove_mark(struct audit_fsnotify_mark *audit_mark)
  {
  	fsnotify_destroy_mark(&audit_mark->mark, audit_fsnotify_group);
  	fsnotify_put_mark(&audit_mark->mark);
  }
  
  void audit_remove_mark_rule(struct audit_krule *krule)
  {
  	struct audit_fsnotify_mark *mark = krule->exe;
  
  	audit_remove_mark(mark);
  }
  
  static void audit_autoremove_mark_rule(struct audit_fsnotify_mark *audit_mark)
  {
  	struct audit_krule *rule = audit_mark->rule;
  	struct audit_entry *entry = container_of(rule, struct audit_entry, rule);
  
  	audit_mark_log_rule_change(audit_mark, "autoremove_rule");
  	audit_del_rule(entry);
  }
  
  /* Update mark data in audit rules based on fsnotify events. */
  static int audit_mark_handle_event(struct fsnotify_group *group,
  				    struct inode *to_tell,
  				    struct fsnotify_mark *inode_mark,
  				    struct fsnotify_mark *vfsmount_mark,

  				    u32 mask, const void *data, int data_type,

  				    const unsigned char *dname, u32 cookie,
  				    struct fsnotify_iter_info *iter_info)

  {
  	struct audit_fsnotify_mark *audit_mark;

  	const struct inode *inode = NULL;

  
  	audit_mark = container_of(inode_mark, struct audit_fsnotify_mark, mark);
  
  	BUG_ON(group != audit_fsnotify_group);
  
  	switch (data_type) {
  	case (FSNOTIFY_EVENT_PATH):

  		inode = ((const struct path *)data)->dentry->d_inode;

  		break;
  	case (FSNOTIFY_EVENT_INODE):

  		inode = (const struct inode *)data;

  		break;
  	default:
  		BUG();
  		return 0;

  	}

  
  	if (mask & (FS_CREATE|FS_MOVED_TO|FS_DELETE|FS_MOVED_FROM)) {
  		if (audit_compare_dname_path(dname, audit_mark->path, AUDIT_NAME_FULL))
  			return 0;
  		audit_update_mark(audit_mark, inode);
  	} else if (mask & (FS_DELETE_SELF|FS_UNMOUNT|FS_MOVE_SELF))
  		audit_autoremove_mark_rule(audit_mark);
  
  	return 0;
  }
  
  static const struct fsnotify_ops audit_mark_fsnotify_ops = {
  	.handle_event =	audit_mark_handle_event,

  	.free_mark = audit_fsnotify_free_mark,

  };
  
  static int __init audit_fsnotify_init(void)
  {
  	audit_fsnotify_group = fsnotify_alloc_group(&audit_mark_fsnotify_ops);
  	if (IS_ERR(audit_fsnotify_group)) {
  		audit_fsnotify_group = NULL;
  		audit_panic("cannot create audit fsnotify group");
  	}
  	return 0;
  }
  device_initcall(audit_fsnotify_init);