# This file is dual licensed under the terms of the Apache License, Version
# 2.0, and the BSD License. See the LICENSE file in the root of this repository
# for complete details.

from __future__ import absolute_import, division, print_function

import abc
import datetime
import os
from enum import Enum

import six

from cryptography import utils
from cryptography.hazmat.primitives.asymmetric import dsa, ec, rsa
from cryptography.x509.extensions import Extension, ExtensionType
from cryptography.x509.name import Name


_UNIX_EPOCH = datetime.datetime(1970, 1, 1)


def _convert_to_naive_utc_time(time):
    """Normalizes a datetime to a naive datetime in UTC.

    time -- datetime to normalize. Assumed to be in UTC if not timezone
            aware.
    """
    if time.tzinfo is not None:
        offset = time.utcoffset()
        offset = offset if offset else datetime.timedelta()
        return time.replace(tzinfo=None) - offset
    else:
        return time


class Version(Enum):
    v1 = 0
    v3 = 2


def load_pem_x509_certificate(data, backend):
    return backend.load_pem_x509_certificate(data)


def load_der_x509_certificate(data, backend):
    return backend.load_der_x509_certificate(data)


def load_pem_x509_csr(data, backend):
    return backend.load_pem_x509_csr(data)


def load_der_x509_csr(data, backend):
    return backend.load_der_x509_csr(data)


def load_pem_x509_crl(data, backend):
    return backend.load_pem_x509_crl(data)


def load_der_x509_crl(data, backend):
    return backend.load_der_x509_crl(data)


class InvalidVersion(Exception):
    def __init__(self, msg, parsed_version):
        super(InvalidVersion, self).__init__(msg)
        self.parsed_version = parsed_version


@six.add_metaclass(abc.ABCMeta)
class Certificate(object):
    @abc.abstractmethod
    def fingerprint(self, algorithm):
        """
        Returns bytes using digest passed.
        """

    @abc.abstractproperty
    def serial_number(self):
        """
        Returns certificate serial number
        """

    @abc.abstractproperty
    def version(self):
        """
        Returns the certificate version
        """

    @abc.abstractmethod
    def public_key(self):
        """
        Returns the public key
        """

    @abc.abstractproperty
    def not_valid_before(self):
        """
        Not before time (represented as UTC datetime)
        """

    @abc.abstractproperty
    def not_valid_after(self):
        """
        Not after time (represented as UTC datetime)
        """

    @abc.abstractproperty
    def issuer(self):
        """
        Returns the issuer name object.
        """

    @abc.abstractproperty
    def subject(self):
        """
        Returns the subject name object.
        """

    @abc.abstractproperty
    def signature_hash_algorithm(self):
        """
        Returns a HashAlgorithm corresponding to the type of the digest signed
        in the certificate.
        """

    @abc.abstractproperty
    def signature_algorithm_oid(self):
        """
        Returns the ObjectIdentifier of the signature algorithm.
        """

    @abc.abstractproperty
    def extensions(self):
        """
        Returns an Extensions object.
        """

    @abc.abstractproperty
    def signature(self):
        """
        Returns the signature bytes.
        """

    @abc.abstractproperty
    def tbs_certificate_bytes(self):
        """
        Returns the tbsCertificate payload bytes as defined in RFC 5280.
        """

    @abc.abstractmethod
    def __eq__(self, other):
        """
        Checks equality.
        """

    @abc.abstractmethod
    def __ne__(self, other):
        """
        Checks not equal.
        """

    @abc.abstractmethod
    def __hash__(self):
        """
        Computes a hash.
        """

    @abc.abstractmethod
    def public_bytes(self, encoding):
        """
        Serializes the certificate to PEM or DER format.
        """


@six.add_metaclass(abc.ABCMeta)
class CertificateRevocationList(object):
    @abc.abstractmethod
    def public_bytes(self, encoding):
        """
        Serializes the CRL to PEM or DER format.
        """

    @abc.abstractmethod
    def fingerprint(self, algorithm):
        """
        Returns bytes using digest passed.
        """

    @abc.abstractmethod
    def get_revoked_certificate_by_serial_number(self, serial_number):
        """
        Returns an instance of RevokedCertificate or None if the serial_number
        is not in the CRL.
        """

    @abc.abstractproperty
    def signature_hash_algorithm(self):
        """
        Returns a HashAlgorithm corresponding to the type of the digest signed
        in the certificate.
        """

    @abc.abstractproperty
    def signature_algorithm_oid(self):
        """
        Returns the ObjectIdentifier of the signature algorithm.
        """

    @abc.abstractproperty
    def issuer(self):
        """
        Returns the X509Name with the issuer of this CRL.
        """

    @abc.abstractproperty
    def next_update(self):
        """
        Returns the date of next update for this CRL.
        """

    @abc.abstractproperty
    def last_update(self):
        """
        Returns the date of last update for this CRL.
        """

    @abc.abstractproperty
    def extensions(self):
        """
        Returns an Extensions object containing a list of CRL extensions.
        """

    @abc.abstractproperty
    def signature(self):
        """
        Returns the signature bytes.
        """

    @abc.abstractproperty
    def tbs_certlist_bytes(self):
        """
        Returns the tbsCertList payload bytes as defined in RFC 5280.
        """

    @abc.abstractmethod
    def __eq__(self, other):
        """
        Checks equality.
        """

    @abc.abstractmethod
    def __ne__(self, other):
        """
        Checks not equal.
        """

    @abc.abstractmethod
    def is_signature_valid(self, public_key):
        """
        Verifies signature of revocation list against given public key.
        """


@six.add_metaclass(abc.ABCMeta)
class CertificateSigningRequest(object):
    @abc.abstractmethod
    def __eq__(self, other):
        """
        Checks equality.
        """

    @abc.abstractmethod
    def __ne__(self, other):
        """
        Checks not equal.
        """

    @abc.abstractmethod
    def __hash__(self):
        """
        Computes a hash.
        """

    @abc.abstractmethod
    def public_key(self):
        """
        Returns the public key
        """

    @abc.abstractproperty
    def subject(self):
        """
        Returns the subject name object.
        """

    @abc.abstractproperty
    def signature_hash_algorithm(self):
        """
        Returns a HashAlgorithm corresponding to the type of the digest signed
        in the certificate.
        """

    @abc.abstractproperty
    def signature_algorithm_oid(self):
        """
        Returns the ObjectIdentifier of the signature algorithm.
        """

    @abc.abstractproperty
    def extensions(self):
        """
        Returns the extensions in the signing request.
        """

    @abc.abstractmethod
    def public_bytes(self, encoding):
        """
        Encodes the request to PEM or DER format.
        """

    @abc.abstractproperty
    def signature(self):
        """
        Returns the signature bytes.
        """

    @abc.abstractproperty
    def tbs_certrequest_bytes(self):
        """
        Returns the PKCS#10 CertificationRequestInfo bytes as defined in RFC
        2986.
        """

    @abc.abstractproperty
    def is_signature_valid(self):
        """
        Verifies signature of signing request.
        """


@six.add_metaclass(abc.ABCMeta)
class RevokedCertificate(object):
    @abc.abstractproperty
    def serial_number(self):
        """
        Returns the serial number of the revoked certificate.
        """

    @abc.abstractproperty
    def revocation_date(self):
        """
        Returns the date of when this certificate was revoked.
        """

    @abc.abstractproperty
    def extensions(self):
        """
        Returns an Extensions object containing a list of Revoked extensions.
        """


class CertificateSigningRequestBuilder(object):
    def __init__(self, subject_name=None, extensions=[]):
        """
        Creates an empty X.509 certificate request (v1).
        """
        self._subject_name = subject_name
        self._extensions = extensions

    def subject_name(self, name):
        """
        Sets the certificate requestor's distinguished name.
        """
        if not isinstance(name, Name):
            raise TypeError('Expecting x509.Name object.')
        if self._subject_name is not None:
            raise ValueError('The subject name may only be set once.')
        return CertificateSigningRequestBuilder(name, self._extensions)

    def add_extension(self, extension, critical):
        """
        Adds an X.509 extension to the certificate request.
        """
        if not isinstance(extension, ExtensionType):
            raise TypeError("extension must be an ExtensionType")

        extension = Extension(extension.oid, critical, extension)

        # TODO: This is quadratic in the number of extensions
        for e in self._extensions:
            if e.oid == extension.oid:
                raise ValueError('This extension has already been set.')
        return CertificateSigningRequestBuilder(
            self._subject_name, self._extensions + [extension]
        )

    def sign(self, private_key, algorithm, backend):
        """
        Signs the request using the requestor's private key.
        """
        if self._subject_name is None:
            raise ValueError("A CertificateSigningRequest must have a subject")
        return backend.create_x509_csr(self, private_key, algorithm)


class CertificateBuilder(object):
    def __init__(self, issuer_name=None, subject_name=None,
                 public_key=None, serial_number=None, not_valid_before=None,
                 not_valid_after=None, extensions=[]):
        self._version = Version.v3
        self._issuer_name = issuer_name
        self._subject_name = subject_name
        self._public_key = public_key
        self._serial_number = serial_number
        self._not_valid_before = not_valid_before
        self._not_valid_after = not_valid_after
        self._extensions = extensions

    def issuer_name(self, name):
        """
        Sets the CA's distinguished name.
        """
        if not isinstance(name, Name):
            raise TypeError('Expecting x509.Name object.')
        if self._issuer_name is not None:
            raise ValueError('The issuer name may only be set once.')
        return CertificateBuilder(
            name, self._subject_name, self._public_key,
            self._serial_number, self._not_valid_before,
            self._not_valid_after, self._extensions
        )

    def subject_name(self, name):
        """
        Sets the requestor's distinguished name.
        """
        if not isinstance(name, Name):
            raise TypeError('Expecting x509.Name object.')
        if self._subject_name is not None:
            raise ValueError('The subject name may only be set once.')
        return CertificateBuilder(
            self._issuer_name, name, self._public_key,
            self._serial_number, self._not_valid_before,
            self._not_valid_after, self._extensions
        )

    def public_key(self, key):
        """
        Sets the requestor's public key (as found in the signing request).
        """
        if not isinstance(key, (dsa.DSAPublicKey, rsa.RSAPublicKey,
                                ec.EllipticCurvePublicKey)):
            raise TypeError('Expecting one of DSAPublicKey, RSAPublicKey,'
                            ' or EllipticCurvePublicKey.')
        if self._public_key is not None:
            raise ValueError('The public key may only be set once.')
        return CertificateBuilder(
            self._issuer_name, self._subject_name, key,
            self._serial_number, self._not_valid_before,
            self._not_valid_after, self._extensions
        )

    def serial_number(self, number):
        """
        Sets the certificate serial number.
        """
        if not isinstance(number, six.integer_types):
            raise TypeError('Serial number must be of integral type.')
        if self._serial_number is not None:
            raise ValueError('The serial number may only be set once.')
        if number <= 0:
            raise ValueError('The serial number should be positive.')

        # ASN.1 integers are always signed, so most significant bit must be
        # zero.
        if number.bit_length() >= 160:  # As defined in RFC 5280
            raise ValueError('The serial number should not be more than 159 '
                             'bits.')
        return CertificateBuilder(
            self._issuer_name, self._subject_name,
            self._public_key, number, self._not_valid_before,
            self._not_valid_after, self._extensions
        )

    def not_valid_before(self, time):
        """
        Sets the certificate activation time.
        """
        if not isinstance(time, datetime.datetime):
            raise TypeError('Expecting datetime object.')
        if self._not_valid_before is not None:
            raise ValueError('The not valid before may only be set once.')
        time = _convert_to_naive_utc_time(time)
        if time <= _UNIX_EPOCH:
            raise ValueError('The not valid before date must be after the unix'
                             ' epoch (1970 January 1).')
        if self._not_valid_after is not None and time > self._not_valid_after:
            raise ValueError(
                'The not valid before date must be before the not valid after '
                'date.'
            )
        return CertificateBuilder(
            self._issuer_name, self._subject_name,
            self._public_key, self._serial_number, time,
            self._not_valid_after, self._extensions
        )

    def not_valid_after(self, time):
        """
        Sets the certificate expiration time.
        """
        if not isinstance(time, datetime.datetime):
            raise TypeError('Expecting datetime object.')
        if self._not_valid_after is not None:
            raise ValueError('The not valid after may only be set once.')
        time = _convert_to_naive_utc_time(time)
        if time <= _UNIX_EPOCH:
            raise ValueError('The not valid after date must be after the unix'
                             ' epoch (1970 January 1).')
        if (self._not_valid_before is not None and
                time < self._not_valid_before):
            raise ValueError(
                'The not valid after date must be after the not valid before '
                'date.'
            )
        return CertificateBuilder(
            self._issuer_name, self._subject_name,
            self._public_key, self._serial_number, self._not_valid_before,
            time, self._extensions
        )

    def add_extension(self, extension, critical):
        """
        Adds an X.509 extension to the certificate.
        """
        if not isinstance(extension, ExtensionType):
            raise TypeError("extension must be an ExtensionType")

        extension = Extension(extension.oid, critical, extension)

        # TODO: This is quadratic in the number of extensions
        for e in self._extensions:
            if e.oid == extension.oid:
                raise ValueError('This extension has already been set.')

        return CertificateBuilder(
            self._issuer_name, self._subject_name,
            self._public_key, self._serial_number, self._not_valid_before,
            self._not_valid_after, self._extensions + [extension]
        )

    def sign(self, private_key, algorithm, backend):
        """
        Signs the certificate using the CA's private key.
        """
        if self._subject_name is None:
            raise ValueError("A certificate must have a subject name")

        if self._issuer_name is None:
            raise ValueError("A certificate must have an issuer name")

        if self._serial_number is None:
            raise ValueError("A certificate must have a serial number")

        if self._not_valid_before is None:
            raise ValueError("A certificate must have a not valid before time")

        if self._not_valid_after is None:
            raise ValueError("A certificate must have a not valid after time")

        if self._public_key is None:
            raise ValueError("A certificate must have a public key")

        return backend.create_x509_certificate(self, private_key, algorithm)


class CertificateRevocationListBuilder(object):
    def __init__(self, issuer_name=None, last_update=None, next_update=None,
                 extensions=[], revoked_certificates=[]):
        self._issuer_name = issuer_name
        self._last_update = last_update
        self._next_update = next_update
        self._extensions = extensions
        self._revoked_certificates = revoked_certificates

    def issuer_name(self, issuer_name):
        if not isinstance(issuer_name, Name):
            raise TypeError('Expecting x509.Name object.')
        if self._issuer_name is not None:
            raise ValueError('The issuer name may only be set once.')
        return CertificateRevocationListBuilder(
            issuer_name, self._last_update, self._next_update,
            self._extensions, self._revoked_certificates
        )

    def last_update(self, last_update):
        if not isinstance(last_update, datetime.datetime):
            raise TypeError('Expecting datetime object.')
        if self._last_update is not None:
            raise ValueError('Last update may only be set once.')
        last_update = _convert_to_naive_utc_time(last_update)
        if last_update <= _UNIX_EPOCH:
            raise ValueError('The last update date must be after the unix'
                             ' epoch (1970 January 1).')
        if self._next_update is not None and last_update > self._next_update:
            raise ValueError(
                'The last update date must be before the next update date.'
            )
        return CertificateRevocationListBuilder(
            self._issuer_name, last_update, self._next_update,
            self._extensions, self._revoked_certificates
        )

    def next_update(self, next_update):
        if not isinstance(next_update, datetime.datetime):
            raise TypeError('Expecting datetime object.')
        if self._next_update is not None:
            raise ValueError('Last update may only be set once.')
        next_update = _convert_to_naive_utc_time(next_update)
        if next_update <= _UNIX_EPOCH:
            raise ValueError('The last update date must be after the unix'
                             ' epoch (1970 January 1).')
        if self._last_update is not None and next_update < self._last_update:
            raise ValueError(
                'The next update date must be after the last update date.'
            )
        return CertificateRevocationListBuilder(
            self._issuer_name, self._last_update, next_update,
            self._extensions, self._revoked_certificates
        )

    def add_extension(self, extension, critical):
        """
        Adds an X.509 extension to the certificate revocation list.
        """
        if not isinstance(extension, ExtensionType):
            raise TypeError("extension must be an ExtensionType")

        extension = Extension(extension.oid, critical, extension)

        # TODO: This is quadratic in the number of extensions
        for e in self._extensions:
            if e.oid == extension.oid:
                raise ValueError('This extension has already been set.')
        return CertificateRevocationListBuilder(
            self._issuer_name, self._last_update, self._next_update,
            self._extensions + [extension], self._revoked_certificates
        )

    def add_revoked_certificate(self, revoked_certificate):
        """
        Adds a revoked certificate to the CRL.
        """
        if not isinstance(revoked_certificate, RevokedCertificate):
            raise TypeError("Must be an instance of RevokedCertificate")

        return CertificateRevocationListBuilder(
            self._issuer_name, self._last_update,
            self._next_update, self._extensions,
            self._revoked_certificates + [revoked_certificate]
        )

    def sign(self, private_key, algorithm, backend):
        if self._issuer_name is None:
            raise ValueError("A CRL must have an issuer name")

        if self._last_update is None:
            raise ValueError("A CRL must have a last update time")

        if self._next_update is None:
            raise ValueError("A CRL must have a next update time")

        return backend.create_x509_crl(self, private_key, algorithm)


class RevokedCertificateBuilder(object):
    def __init__(self, serial_number=None, revocation_date=None,
                 extensions=[]):
        self._serial_number = serial_number
        self._revocation_date = revocation_date
        self._extensions = extensions

    def serial_number(self, number):
        if not isinstance(number, six.integer_types):
            raise TypeError('Serial number must be of integral type.')
        if self._serial_number is not None:
            raise ValueError('The serial number may only be set once.')
        if number <= 0:
            raise ValueError('The serial number should be positive')

        # ASN.1 integers are always signed, so most significant bit must be
        # zero.
        if number.bit_length() >= 160:  # As defined in RFC 5280
            raise ValueError('The serial number should not be more than 159 '
                             'bits.')
        return RevokedCertificateBuilder(
            number, self._revocation_date, self._extensions
        )

    def revocation_date(self, time):
        if not isinstance(time, datetime.datetime):
            raise TypeError('Expecting datetime object.')
        if self._revocation_date is not None:
            raise ValueError('The revocation date may only be set once.')
        time = _convert_to_naive_utc_time(time)
        if time <= _UNIX_EPOCH:
            raise ValueError('The revocation date must be after the unix'
                             ' epoch (1970 January 1).')
        return RevokedCertificateBuilder(
            self._serial_number, time, self._extensions
        )

    def add_extension(self, extension, critical):
        if not isinstance(extension, ExtensionType):
            raise TypeError("extension must be an ExtensionType")

        extension = Extension(extension.oid, critical, extension)

        # TODO: This is quadratic in the number of extensions
        for e in self._extensions:
            if e.oid == extension.oid:
                raise ValueError('This extension has already been set.')
        return RevokedCertificateBuilder(
            self._serial_number, self._revocation_date,
            self._extensions + [extension]
        )

    def build(self, backend):
        if self._serial_number is None:
            raise ValueError("A revoked certificate must have a serial number")
        if self._revocation_date is None:
            raise ValueError(
                "A revoked certificate must have a revocation date"
            )

        return backend.create_x509_revoked_certificate(self)


def random_serial_number():
    return utils.int_from_bytes(os.urandom(20), "big") >> 1