# Copyright (c) 2018 Yubico AB
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#   without modification, are permitted provided that the following
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import struct
import time
from typing import Optional

from fido2.ctap1 import ApduError, Ctap1

from yubikit.core.fido import FidoConnection
from yubikit.core.smartcard import SW

U2F_VENDOR_FIRST = 0x40

# FIPS specific INS values
INS_FIPS_VERIFY_PIN = U2F_VENDOR_FIRST + 3
INS_FIPS_SET_PIN = U2F_VENDOR_FIRST + 4
INS_FIPS_RESET = U2F_VENDOR_FIRST + 5
INS_FIPS_VERIFY_FIPS_MODE = U2F_VENDOR_FIRST + 6


def is_in_fips_mode(fido_connection: FidoConnection) -> bool:
    """Check if a YubiKey 4 FIPS is in FIPS approved mode.

    :param fido_connection: A FIDO connection.
    """
    try:
        ctap = Ctap1(fido_connection)
        ctap.send_apdu(ins=INS_FIPS_VERIFY_FIPS_MODE)
        return True
    except ApduError as e:
        # 0x6a81: Function not supported (PIN not set - not FIPS Mode)
        if e.code == SW.FUNCTION_NOT_SUPPORTED:
            return False
        raise


def fips_change_pin(
    fido_connection: FidoConnection, old_pin: Optional[str], new_pin: str
):
    """Change the PIN on a YubiKey 4 FIPS.

    If no PIN is set, pass None or an empty string as old_pin.

    :param fido_connection: A FIDO connection.
    :param old_pin: The old PIN.
    :param new_pin: The new PIN.
    """
    ctap = Ctap1(fido_connection)

    old_pin_bytes = old_pin.encode() if old_pin else b""
    new_pin_bytes = new_pin.encode()
    new_length = len(new_pin_bytes)

    data = struct.pack("B", new_length) + old_pin_bytes + new_pin_bytes

    ctap.send_apdu(ins=INS_FIPS_SET_PIN, data=data)


def fips_verify_pin(fido_connection: FidoConnection, pin: str):
    """Unlock the YubiKey 4 FIPS U2F module for credential creation.

    :param fido_connection: A FIDO connection.
    :param pin: The FIDO PIN.
    """
    ctap = Ctap1(fido_connection)
    ctap.send_apdu(ins=INS_FIPS_VERIFY_PIN, data=pin.encode())


def fips_reset(fido_connection: FidoConnection):
    """Reset the FIDO module of a YubiKey 4 FIPS.

    Note: This action is only permitted immediately after YubiKey power-up. It also
    requires the user to touch the flashing button on the YubiKey, and will halt until
    that happens, or the command times out.

    :param fido_connection: A FIDO connection.
    """
    ctap = Ctap1(fido_connection)
    while True:
        try:
            ctap.send_apdu(ins=INS_FIPS_RESET)
            return
        except ApduError as e:
            if e.code == SW.CONDITIONS_NOT_SATISFIED:
                time.sleep(0.5)
            else:
                raise e
