keyctl.c

linux 内核源代码

			ret = -ENOKEY;
		goto error5;
	}

	/* link the resulting key to the destination keyring if we can */
	if (dest_ref) {
		ret = key_permission(key_ref, KEY_LINK);
		if (ret < 0)
			goto error6;

		ret = key_link(key_ref_to_ptr(dest_ref), key_ref_to_ptr(key_ref));
		if (ret < 0)
			goto error6;
	}

	ret = key_ref_to_ptr(key_ref)->serial;

 error6:
	key_ref_put(key_ref);
 error5:
	key_type_put(ktype);
 error4:
	key_ref_put(dest_ref);
 error3:
	key_ref_put(keyring_ref);
 error2:
	kfree(description);
 error:
	return ret;

} /* end keyctl_keyring_search() */

/*****************************************************************************/
/*
 * read a user key's payload
 * - the keyring must be readable or the key must be searchable from the
 *   process's keyrings
 * - if there's a buffer, we place up to buflen bytes of data into it
 * - unless there's an error, we return the amount of data in the key,
 *   irrespective of how much we may have copied
 * - implements keyctl(KEYCTL_READ)
 */
long keyctl_read_key(key_serial_t keyid, char __user *buffer, size_t buflen)
{
	struct key *key;
	key_ref_t key_ref;
	long ret;

	/* find the key first */
	key_ref = lookup_user_key(NULL, keyid, 0, 0, 0);
	if (IS_ERR(key_ref)) {
		ret = -ENOKEY;
		goto error;
	}

	key = key_ref_to_ptr(key_ref);

	/* see if we can read it directly */
	ret = key_permission(key_ref, KEY_READ);
	if (ret == 0)
		goto can_read_key;
	if (ret != -EACCES)
		goto error;

	/* we can't; see if it's searchable from this process's keyrings
	 * - we automatically take account of the fact that it may be
	 *   dangling off an instantiation key
	 */
	if (!is_key_possessed(key_ref)) {
		ret = -EACCES;
		goto error2;
	}

	/* the key is probably readable - now try to read it */
 can_read_key:
	ret = key_validate(key);
	if (ret == 0) {
		ret = -EOPNOTSUPP;
		if (key->type->read) {
			/* read the data with the semaphore held (since we
			 * might sleep) */
			down_read(&key->sem);
			ret = key->type->read(key, buffer, buflen);
			up_read(&key->sem);
		}
	}

 error2:
	key_put(key);
 error:
	return ret;

} /* end keyctl_read_key() */

/*****************************************************************************/
/*
 * change the ownership of a key
 * - the keyring owned by the changer
 * - if the uid or gid is -1, then that parameter is not changed
 * - implements keyctl(KEYCTL_CHOWN)
 */
long keyctl_chown_key(key_serial_t id, uid_t uid, gid_t gid)
{
	struct key_user *newowner, *zapowner = NULL;
	struct key *key;
	key_ref_t key_ref;
	long ret;

	ret = 0;
	if (uid == (uid_t) -1 && gid == (gid_t) -1)
		goto error;

	key_ref = lookup_user_key(NULL, id, 1, 1, KEY_SETATTR);
	if (IS_ERR(key_ref)) {
		ret = PTR_ERR(key_ref);
		goto error;
	}

	key = key_ref_to_ptr(key_ref);

	/* make the changes with the locks held to prevent chown/chown races */
	ret = -EACCES;
	down_write(&key->sem);

	if (!capable(CAP_SYS_ADMIN)) {
		/* only the sysadmin can chown a key to some other UID */
		if (uid != (uid_t) -1 && key->uid != uid)
			goto error_put;

		/* only the sysadmin can set the key's GID to a group other
		 * than one of those that the current process subscribes to */
		if (gid != (gid_t) -1 && gid != key->gid && !in_group_p(gid))
			goto error_put;
	}

	/* change the UID */
	if (uid != (uid_t) -1 && uid != key->uid) {
		ret = -ENOMEM;
		newowner = key_user_lookup(uid);
		if (!newowner)
			goto error_put;

		/* transfer the quota burden to the new user */
		if (test_bit(KEY_FLAG_IN_QUOTA, &key->flags)) {
			spin_lock(&newowner->lock);
			if (newowner->qnkeys + 1 >= KEYQUOTA_MAX_KEYS ||
			    newowner->qnbytes + key->quotalen >=
			    KEYQUOTA_MAX_BYTES)
				goto quota_overrun;

			newowner->qnkeys++;
			newowner->qnbytes += key->quotalen;
			spin_unlock(&newowner->lock);

			spin_lock(&key->user->lock);
			key->user->qnkeys--;
			key->user->qnbytes -= key->quotalen;
			spin_unlock(&key->user->lock);
		}

		atomic_dec(&key->user->nkeys);
		atomic_inc(&newowner->nkeys);

		if (test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
			atomic_dec(&key->user->nikeys);
			atomic_inc(&newowner->nikeys);
		}

		zapowner = key->user;
		key->user = newowner;
		key->uid = uid;
	}

	/* change the GID */
	if (gid != (gid_t) -1)
		key->gid = gid;

	ret = 0;

error_put:
	up_write(&key->sem);
	key_put(key);
	if (zapowner)
		key_user_put(zapowner);
error:
	return ret;

quota_overrun:
	spin_unlock(&newowner->lock);
	zapowner = newowner;
	ret = -EDQUOT;
	goto error_put;

} /* end keyctl_chown_key() */

/*****************************************************************************/
/*
 * change the permission mask on a key
 * - the keyring owned by the changer
 * - implements keyctl(KEYCTL_SETPERM)
 */
long keyctl_setperm_key(key_serial_t id, key_perm_t perm)
{
	struct key *key;
	key_ref_t key_ref;
	long ret;

	ret = -EINVAL;
	if (perm & ~(KEY_POS_ALL | KEY_USR_ALL | KEY_GRP_ALL | KEY_OTH_ALL))
		goto error;

	key_ref = lookup_user_key(NULL, id, 1, 1, KEY_SETATTR);
	if (IS_ERR(key_ref)) {
		ret = PTR_ERR(key_ref);
		goto error;
	}

	key = key_ref_to_ptr(key_ref);

	/* make the changes with the locks held to prevent chown/chmod races */
	ret = -EACCES;
	down_write(&key->sem);

	/* if we're not the sysadmin, we can only change a key that we own */
	if (capable(CAP_SYS_ADMIN) || key->uid == current->fsuid) {
		key->perm = perm;
		ret = 0;
	}

	up_write(&key->sem);
	key_put(key);
error:
	return ret;

} /* end keyctl_setperm_key() */

/*****************************************************************************/
/*
 * instantiate the key with the specified payload, and, if one is given, link
 * the key into the keyring
 */
long keyctl_instantiate_key(key_serial_t id,
			    const void __user *_payload,
			    size_t plen,
			    key_serial_t ringid)
{
	struct request_key_auth *rka;
	struct key *instkey;
	key_ref_t keyring_ref;
	void *payload;
	long ret;

	ret = -EINVAL;
	if (plen > 32767)
		goto error;

	/* the appropriate instantiation authorisation key must have been
	 * assumed before calling this */
	ret = -EPERM;
	instkey = current->request_key_auth;
	if (!instkey)
		goto error;

	rka = instkey->payload.data;
	if (rka->target_key->serial != id)
		goto error;

	/* pull the payload in if one was supplied */
	payload = NULL;

	if (_payload) {
		ret = -ENOMEM;
		payload = kmalloc(plen, GFP_KERNEL);
		if (!payload)
			goto error;

		ret = -EFAULT;
		if (copy_from_user(payload, _payload, plen) != 0)
			goto error2;
	}

	/* find the destination keyring amongst those belonging to the
	 * requesting task */
	keyring_ref = NULL;
	if (ringid) {
		keyring_ref = lookup_user_key(rka->context, ringid, 1, 0,
					      KEY_WRITE);
		if (IS_ERR(keyring_ref)) {
			ret = PTR_ERR(keyring_ref);
			goto error2;
		}
	}

	/* instantiate the key and link it into a keyring */
	ret = key_instantiate_and_link(rka->target_key, payload, plen,
				       key_ref_to_ptr(keyring_ref), instkey);

	key_ref_put(keyring_ref);

	/* discard the assumed authority if it's just been disabled by
	 * instantiation of the key */
	if (ret == 0) {
		key_put(current->request_key_auth);
		current->request_key_auth = NULL;
	}

error2:
	kfree(payload);
error:
	return ret;

} /* end keyctl_instantiate_key() */

/*****************************************************************************/
/*
 * negatively instantiate the key with the given timeout (in seconds), and, if
 * one is given, link the key into the keyring
 */
long keyctl_negate_key(key_serial_t id, unsigned timeout, key_serial_t ringid)
{
	struct request_key_auth *rka;
	struct key *instkey;
	key_ref_t keyring_ref;
	long ret;

	/* the appropriate instantiation authorisation key must have been
	 * assumed before calling this */
	ret = -EPERM;
	instkey = current->request_key_auth;
	if (!instkey)
		goto error;

	rka = instkey->payload.data;
	if (rka->target_key->serial != id)
		goto error;

	/* find the destination keyring if present (which must also be
	 * writable) */
	keyring_ref = NULL;
	if (ringid) {
		keyring_ref = lookup_user_key(NULL, ringid, 1, 0, KEY_WRITE);
		if (IS_ERR(keyring_ref)) {
			ret = PTR_ERR(keyring_ref);
			goto error;
		}
	}

	/* instantiate the key and link it into a keyring */
	ret = key_negate_and_link(rka->target_key, timeout,
				  key_ref_to_ptr(keyring_ref), instkey);

	key_ref_put(keyring_ref);

	/* discard the assumed authority if it's just been disabled by
	 * instantiation of the key */
	if (ret == 0) {
		key_put(current->request_key_auth);
		current->request_key_auth = NULL;
	}

error:
	return ret;

} /* end keyctl_negate_key() */

/*****************************************************************************/
/*
 * set the default keyring in which request_key() will cache keys
 * - return the old setting
 */
long keyctl_set_reqkey_keyring(int reqkey_defl)
{
	int ret;

	switch (reqkey_defl) {
	case KEY_REQKEY_DEFL_THREAD_KEYRING:
		ret = install_thread_keyring(current);
		if (ret < 0)
			return ret;
		goto set;

	case KEY_REQKEY_DEFL_PROCESS_KEYRING:
		ret = install_process_keyring(current);
		if (ret < 0)
			return ret;

	case KEY_REQKEY_DEFL_DEFAULT:
	case KEY_REQKEY_DEFL_SESSION_KEYRING:
	case KEY_REQKEY_DEFL_USER_KEYRING:
	case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
	set:
		current->jit_keyring = reqkey_defl;

	case KEY_REQKEY_DEFL_NO_CHANGE:
		return current->jit_keyring;

	case KEY_REQKEY_DEFL_GROUP_KEYRING:
	default:
		return -EINVAL;
	}

} /* end keyctl_set_reqkey_keyring() */

/*****************************************************************************/
/*
 * set or clear the timeout for a key
 */
long keyctl_set_timeout(key_serial_t id, unsigned timeout)
{
	struct timespec now;
	struct key *key;
	key_ref_t key_ref;
	time_t expiry;
	long ret;

	key_ref = lookup_user_key(NULL, id, 1, 1, KEY_SETATTR);
	if (IS_ERR(key_ref)) {
		ret = PTR_ERR(key_ref);
		goto error;
	}

	key = key_ref_to_ptr(key_ref);

	/* make the changes with the locks held to prevent races */
	down_write(&key->sem);

	expiry = 0;
	if (timeout > 0) {
		now = current_kernel_time();
		expiry = now.tv_sec + timeout;
	}

	key->expiry = expiry;

	up_write(&key->sem);
	key_put(key);

	ret = 0;
error:
	return ret;

} /* end keyctl_set_timeout() */

/*****************************************************************************/
/*
 * assume the authority to instantiate the specified key
 */
long keyctl_assume_authority(key_serial_t id)
{
	struct key *authkey;
	long ret;

	/* special key IDs aren't permitted */
	ret = -EINVAL;
	if (id < 0)
		goto error;

	/* we divest ourselves of authority if given an ID of 0 */
	if (id == 0) {
		key_put(current->request_key_auth);
		current->request_key_auth = NULL;
		ret = 0;
		goto error;
	}

	/* attempt to assume the authority temporarily granted to us whilst we
	 * instantiate the specified key
	 * - the authorisation key must be in the current task's keyrings
	 *   somewhere
	 */
	authkey = key_get_instantiation_authkey(id);
	if (IS_ERR(authkey)) {
		ret = PTR_ERR(authkey);
		goto error;
	}

	key_put(current->request_key_auth);
	current->request_key_auth = authkey;
	ret = authkey->serial;

error:
	return ret;

} /* end keyctl_assume_authority() */

/*****************************************************************************/
/*
 * the key control system call
 */
asmlinkage long sys_keyctl(int option, unsigned long arg2, unsigned long arg3,
			   unsigned long arg4, unsigned long arg5)
{
	switch (option) {
	case KEYCTL_GET_KEYRING_ID:
		return keyctl_get_keyring_ID((key_serial_t) arg2,
					     (int) arg3);

	case KEYCTL_JOIN_SESSION_KEYRING:
		return keyctl_join_session_keyring((const char __user *) arg2);

	case KEYCTL_UPDATE:
		return keyctl_update_key((key_serial_t) arg2,
					 (const void __user *) arg3,
					 (size_t) arg4);

	case KEYCTL_REVOKE:
		return keyctl_revoke_key((key_serial_t) arg2);

	case KEYCTL_DESCRIBE:
		return keyctl_describe_key((key_serial_t) arg2,
					   (char __user *) arg3,
					   (unsigned) arg4);

	case KEYCTL_CLEAR:
		return keyctl_keyring_clear((key_serial_t) arg2);

	case KEYCTL_LINK:
		return keyctl_keyring_link((key_serial_t) arg2,
					   (key_serial_t) arg3);

	case KEYCTL_UNLINK:
		return keyctl_keyring_unlink((key_serial_t) arg2,
					     (key_serial_t) arg3);

	case KEYCTL_SEARCH:
		return keyctl_keyring_search((key_serial_t) arg2,
					     (const char __user *) arg3,
					     (const char __user *) arg4,
					     (key_serial_t) arg5);

	case KEYCTL_READ:
		return keyctl_read_key((key_serial_t) arg2,
				       (char __user *) arg3,
				       (size_t) arg4);

	case KEYCTL_CHOWN:
		return keyctl_chown_key((key_serial_t) arg2,
					(uid_t) arg3,
					(gid_t) arg4);

	case KEYCTL_SETPERM:
		return keyctl_setperm_key((key_serial_t) arg2,
					  (key_perm_t) arg3);

	case KEYCTL_INSTANTIATE:
		return keyctl_instantiate_key((key_serial_t) arg2,
					      (const void __user *) arg3,
					      (size_t) arg4,
					      (key_serial_t) arg5);

	case KEYCTL_NEGATE:
		return keyctl_negate_key((key_serial_t) arg2,
					 (unsigned) arg3,
					 (key_serial_t) arg4);

	case KEYCTL_SET_REQKEY_KEYRING:
		return keyctl_set_reqkey_keyring(arg2);

	case KEYCTL_SET_TIMEOUT:
		return keyctl_set_timeout((key_serial_t) arg2,
					  (unsigned) arg3);

	case KEYCTL_ASSUME_AUTHORITY:
		return keyctl_assume_authority((key_serial_t) arg2);

	default:
		return -EOPNOTSUPP;
	}

} /* end sys_keyctl() */