# asn.py
#
# Copyright (C) 2006-2022 wolfSSL Inc.
#
# This file is part of wolfSSL. (formerly known as CyaSSL)
#
# wolfSSL 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.
#
# wolfSSL 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.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA

# pylint: disable=no-member,no-name-in-module

from wolfcrypt._ffi import ffi as _ffi
from wolfcrypt._ffi import lib as _lib
from wolfcrypt.exceptions import WolfCryptError

if _lib.SHA_ENABLED:
    from wolfcrypt.hashes import Sha
if _lib.SHA256_ENABLED:
    from wolfcrypt.hashes import Sha256
if _lib.SHA384_ENABLED:
    from wolfcrypt.hashes import Sha384
if _lib.SHA512_ENABLED:
    from wolfcrypt.hashes import Sha512

if _lib.ASN_ENABLED:
    def pem_to_der(pem, pem_type):
        der = _ffi.new("DerBuffer**")
        ret = _lib.wc_PemToDer(pem, len(pem), pem_type, der, _ffi.NULL,
                               _ffi.NULL, _ffi.NULL)
        if ret != 0:
            err = "Error converting from PEM to DER. ({})".format(ret)
            raise WolfCryptError(err)

        return _ffi.buffer(der[0][0].buffer, der[0][0].length)[:]

    def der_to_pem(der, pem_type):
        pem_length = _lib.wc_DerToPemEx(der, len(der), _ffi.NULL, 0, _ffi.NULL,
                                        pem_type)
        if pem_length <= 0:
            err = "Error getting required PEM buffer length. ({})".format(pem_length)
            raise WolfCryptError(err)

        pem = _ffi.new("byte[%d]" % pem_length)
        pem_length = _lib.wc_DerToPemEx(der, len(der), pem, pem_length,
                                        _ffi.NULL, pem_type)
        if pem_length <= 0:
            err = "Error converting from DER to PEM. ({})".format(pem_length)
            raise WolfCryptError(err)

        return _ffi.buffer(pem, pem_length)[:]

    def hash_oid_from_class(hash_cls):
        if hash_cls == Sha:
            return _lib.SHAh
        elif hash_cls == Sha256:
            return _lib.SHA256h
        elif hash_cls == Sha384:
            return _lib.SHA384h
        elif hash_cls == Sha512:
            return _lib.SHA512h
        else:
            err = "Unknown hash class {}.".format(hash_cls.__name__)
            raise WolfCryptError(err)

    def make_signature(data, hash_cls, key=None):
        hash_obj = hash_cls()
        hash_obj.update(data)
        digest = hash_obj.digest()

        plaintext_sig = _ffi.new("byte[%d]" % _lib.MAX_DER_DIGEST_SZ)
        hash_oid = hash_oid_from_class(hash_cls)
        plaintext_len = _lib.wc_EncodeSignature(plaintext_sig, digest,
                                                len(digest), hash_oid)
        if plaintext_len == 0:
            err = "Error calling wc_EncodeSignature. ({})".format(plaintext_len)
            raise WolfCryptError(err)

        plaintext_sig = _ffi.buffer(plaintext_sig, plaintext_len)[:]
        if key:
            return key.sign(plaintext_sig)
        else:
            return plaintext_sig

    def check_signature(signature, data, hash_cls, pub_key):
        computed_signature = make_signature(data, hash_cls)
        decrypted_signature = pub_key.verify(signature)
        return computed_signature == decrypted_signature