/* Key permission checking

   *
   * Copyright (C) 2005 Red Hat, Inc. All Rights Reserved.
   * Written by David Howells (dhowells@redhat.com)
   *
   * 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.
   */
  
  #include <linux/module.h>

  #include <linux/security.h>

  #include "internal.h"

  /**
   * key_task_permission - Check a key can be used

   * @key_ref: The key to check.
   * @cred: The credentials to use.
   * @perm: The permissions to check for.

   *
   * Check to see whether permission is granted to use a key in the desired way,
   * but permit the security modules to override.
   *

   * The caller must hold either a ref on cred or must hold the RCU readlock.
   *
   * Returns 0 if successful, -EACCES if access is denied based on the
   * permissions bits or the LSM check.

   */

  int key_task_permission(const key_ref_t key_ref, const struct cred *cred,

  			key_perm_t perm)
  {
  	struct key *key;
  	key_perm_t kperm;
  	int ret;
  
  	key = key_ref_to_ptr(key_ref);

  	if (key->user->user_ns != cred->user->user_ns)
  		goto use_other_perms;

  	/* use the second 8-bits of permissions for keys the caller owns */

  	if (key->uid == cred->fsuid) {

  		kperm = key->perm >> 16;
  		goto use_these_perms;
  	}
  
  	/* use the third 8-bits of permissions for keys the caller has a group
  	 * membership in common with */
  	if (key->gid != -1 && key->perm & KEY_GRP_ALL) {

  		if (key->gid == cred->fsgid) {

  			kperm = key->perm >> 8;
  			goto use_these_perms;
  		}

  		ret = groups_search(cred->group_info, key->gid);

  		if (ret) {
  			kperm = key->perm >> 8;
  			goto use_these_perms;
  		}
  	}

  use_other_perms:

  	/* otherwise use the least-significant 8-bits */
  	kperm = key->perm;
  
  use_these_perms:

  	/* use the top 8-bits of permissions for keys the caller possesses
  	 * - possessor permissions are additive with other permissions
  	 */
  	if (is_key_possessed(key_ref))
  		kperm |= key->perm >> 24;

  	kperm = kperm & perm & KEY_ALL;

  	if (kperm != perm)
  		return -EACCES;
  
  	/* let LSM be the final arbiter */

  	return security_key_permission(key_ref, cred, perm);

  }

  EXPORT_SYMBOL(key_task_permission);

  /**
   * key_validate - Validate a key.
   * @key: The key to be validated.
   *
   * Check that a key is valid, returning 0 if the key is okay, -EKEYREVOKED if
   * the key's type has been removed or if the key has been revoked or
   * -EKEYEXPIRED if the key has expired.

   */
  int key_validate(struct key *key)
  {
  	struct timespec now;
  	int ret = 0;
  
  	if (key) {
  		/* check it's still accessible */
  		ret = -EKEYREVOKED;
  		if (test_bit(KEY_FLAG_REVOKED, &key->flags) ||
  		    test_bit(KEY_FLAG_DEAD, &key->flags))
  			goto error;
  
  		/* check it hasn't expired */
  		ret = 0;
  		if (key->expiry) {
  			now = current_kernel_time();
  			if (now.tv_sec >= key->expiry)
  				ret = -EKEYEXPIRED;
  		}
  	}

  error:

  	return ret;

  }

  EXPORT_SYMBOL(key_validate);