# 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 datetime
import ipaddress

from asn1crypto.core import Integer, SequenceOf

from cryptography import x509
from cryptography.x509.extensions import _TLS_FEATURE_TYPE_TO_ENUM
from cryptography.x509.name import _ASN1_TYPE_TO_ENUM
from cryptography.x509.oid import (
    CRLEntryExtensionOID, CertificatePoliciesOID, ExtensionOID
)


class _Integers(SequenceOf):
    _child_spec = Integer


def _obj2txt(backend, obj):
    # Set to 80 on the recommendation of
    # https://www.openssl.org/docs/crypto/OBJ_nid2ln.html#return_values
    #
    # But OIDs longer than this occur in real life (e.g. Active
    # Directory makes some very long OIDs).  So we need to detect
    # and properly handle the case where the default buffer is not
    # big enough.
    #
    buf_len = 80
    buf = backend._ffi.new("char[]", buf_len)

    # 'res' is the number of bytes that *would* be written if the
    # buffer is large enough.  If 'res' > buf_len - 1, we need to
    # alloc a big-enough buffer and go again.
    res = backend._lib.OBJ_obj2txt(buf, buf_len, obj, 1)
    if res > buf_len - 1:  # account for terminating null byte
        buf_len = res + 1
        buf = backend._ffi.new("char[]", buf_len)
        res = backend._lib.OBJ_obj2txt(buf, buf_len, obj, 1)
    backend.openssl_assert(res > 0)
    return backend._ffi.buffer(buf, res)[:].decode()


def _decode_x509_name_entry(backend, x509_name_entry):
    obj = backend._lib.X509_NAME_ENTRY_get_object(x509_name_entry)
    backend.openssl_assert(obj != backend._ffi.NULL)
    data = backend._lib.X509_NAME_ENTRY_get_data(x509_name_entry)
    backend.openssl_assert(data != backend._ffi.NULL)
    value = _asn1_string_to_utf8(backend, data)
    oid = _obj2txt(backend, obj)
    type = _ASN1_TYPE_TO_ENUM[data.type]

    return x509.NameAttribute(x509.ObjectIdentifier(oid), value, type)


def _decode_x509_name(backend, x509_name):
    count = backend._lib.X509_NAME_entry_count(x509_name)
    attributes = []
    prev_set_id = -1
    for x in range(count):
        entry = backend._lib.X509_NAME_get_entry(x509_name, x)
        attribute = _decode_x509_name_entry(backend, entry)
        set_id = backend._lib.Cryptography_X509_NAME_ENTRY_set(entry)
        if set_id != prev_set_id:
            attributes.append(set([attribute]))
        else:
            # is in the same RDN a previous entry
            attributes[-1].add(attribute)
        prev_set_id = set_id

    return x509.Name(x509.RelativeDistinguishedName(rdn) for rdn in attributes)


def _decode_general_names(backend, gns):
    num = backend._lib.sk_GENERAL_NAME_num(gns)
    names = []
    for i in range(num):
        gn = backend._lib.sk_GENERAL_NAME_value(gns, i)
        backend.openssl_assert(gn != backend._ffi.NULL)
        names.append(_decode_general_name(backend, gn))

    return names


def _decode_general_name(backend, gn):
    if gn.type == backend._lib.GEN_DNS:
        # Convert to bytes and then decode to utf8. We don't use
        # asn1_string_to_utf8 here because it doesn't properly convert
        # utf8 from ia5strings.
        data = _asn1_string_to_bytes(backend, gn.d.dNSName).decode("utf8")
        # We don't use the constructor for DNSName so we can bypass validation
        # This allows us to create DNSName objects that have unicode chars
        # when a certificate (against the RFC) contains them.
        return x509.DNSName._init_without_validation(data)
    elif gn.type == backend._lib.GEN_URI:
        # Convert to bytes and then decode to utf8. We don't use
        # asn1_string_to_utf8 here because it doesn't properly convert
        # utf8 from ia5strings.
        data = _asn1_string_to_bytes(
            backend, gn.d.uniformResourceIdentifier
        ).decode("utf8")
        # We don't use the constructor for URI so we can bypass validation
        # This allows us to create URI objects that have unicode chars
        # when a certificate (against the RFC) contains them.
        return x509.UniformResourceIdentifier._init_without_validation(data)
    elif gn.type == backend._lib.GEN_RID:
        oid = _obj2txt(backend, gn.d.registeredID)
        return x509.RegisteredID(x509.ObjectIdentifier(oid))
    elif gn.type == backend._lib.GEN_IPADD:
        data = _asn1_string_to_bytes(backend, gn.d.iPAddress)
        data_len = len(data)
        if data_len == 8 or data_len == 32:
            # This is an IPv4 or IPv6 Network and not a single IP. This
            # type of data appears in Name Constraints. Unfortunately,
            # ipaddress doesn't support packed bytes + netmask. Additionally,
            # IPv6Network can only handle CIDR rather than the full 16 byte
            # netmask. To handle this we convert the netmask to integer, then
            # find the first 0 bit, which will be the prefix. If another 1
            # bit is present after that the netmask is invalid.
            base = ipaddress.ip_address(data[:data_len // 2])
            netmask = ipaddress.ip_address(data[data_len // 2:])
            bits = bin(int(netmask))[2:]
            prefix = bits.find('0')
            # If no 0 bits are found it is a /32 or /128
            if prefix == -1:
                prefix = len(bits)

            if "1" in bits[prefix:]:
                raise ValueError("Invalid netmask")

            ip = ipaddress.ip_network(base.exploded + u"/{0}".format(prefix))
        else:
            ip = ipaddress.ip_address(data)

        return x509.IPAddress(ip)
    elif gn.type == backend._lib.GEN_DIRNAME:
        return x509.DirectoryName(
            _decode_x509_name(backend, gn.d.directoryName)
        )
    elif gn.type == backend._lib.GEN_EMAIL:
        # Convert to bytes and then decode to utf8. We don't use
        # asn1_string_to_utf8 here because it doesn't properly convert
        # utf8 from ia5strings.
        data = _asn1_string_to_bytes(backend, gn.d.rfc822Name).decode("utf8")
        # We don't use the constructor for RFC822Name so we can bypass
        # validation. This allows us to create RFC822Name objects that have
        # unicode chars when a certificate (against the RFC) contains them.
        return x509.RFC822Name._init_without_validation(data)
    elif gn.type == backend._lib.GEN_OTHERNAME:
        type_id = _obj2txt(backend, gn.d.otherName.type_id)
        value = _asn1_to_der(backend, gn.d.otherName.value)
        return x509.OtherName(x509.ObjectIdentifier(type_id), value)
    else:
        # x400Address or ediPartyName
        raise x509.UnsupportedGeneralNameType(
            "{0} is not a supported type".format(
                x509._GENERAL_NAMES.get(gn.type, gn.type)
            ),
            gn.type
        )


def _decode_ocsp_no_check(backend, ext):
    return x509.OCSPNoCheck()


def _decode_crl_number(backend, ext):
    asn1_int = backend._ffi.cast("ASN1_INTEGER *", ext)
    asn1_int = backend._ffi.gc(asn1_int, backend._lib.ASN1_INTEGER_free)
    return x509.CRLNumber(_asn1_integer_to_int(backend, asn1_int))


def _decode_delta_crl_indicator(backend, ext):
    asn1_int = backend._ffi.cast("ASN1_INTEGER *", ext)
    asn1_int = backend._ffi.gc(asn1_int, backend._lib.ASN1_INTEGER_free)
    return x509.DeltaCRLIndicator(_asn1_integer_to_int(backend, asn1_int))


class _X509ExtensionParser(object):
    def __init__(self, ext_count, get_ext, handlers):
        self.ext_count = ext_count
        self.get_ext = get_ext
        self.handlers = handlers

    def parse(self, backend, x509_obj):
        extensions = []
        seen_oids = set()
        for i in range(self.ext_count(backend, x509_obj)):
            ext = self.get_ext(backend, x509_obj, i)
            backend.openssl_assert(ext != backend._ffi.NULL)
            crit = backend._lib.X509_EXTENSION_get_critical(ext)
            critical = crit == 1
            oid = x509.ObjectIdentifier(
                _obj2txt(backend, backend._lib.X509_EXTENSION_get_object(ext))
            )
            if oid in seen_oids:
                raise x509.DuplicateExtension(
                    "Duplicate {0} extension found".format(oid), oid
                )

            # This OID is only supported in OpenSSL 1.1.0+ but we want
            # to support it in all versions of OpenSSL so we decode it
            # ourselves.
            if oid == ExtensionOID.TLS_FEATURE:
                data = backend._lib.X509_EXTENSION_get_data(ext)
                parsed = _Integers.load(_asn1_string_to_bytes(backend, data))
                value = x509.TLSFeature(
                    [_TLS_FEATURE_TYPE_TO_ENUM[x.native] for x in parsed]
                )
                extensions.append(x509.Extension(oid, critical, value))
                seen_oids.add(oid)
                continue

            try:
                handler = self.handlers[oid]
            except KeyError:
                # Dump the DER payload into an UnrecognizedExtension object
                data = backend._lib.X509_EXTENSION_get_data(ext)
                backend.openssl_assert(data != backend._ffi.NULL)
                der = backend._ffi.buffer(data.data, data.length)[:]
                unrecognized = x509.UnrecognizedExtension(oid, der)
                extensions.append(
                    x509.Extension(oid, critical, unrecognized)
                )
            else:
                ext_data = backend._lib.X509V3_EXT_d2i(ext)
                if ext_data == backend._ffi.NULL:
                    backend._consume_errors()
                    raise ValueError(
                        "The {0} extension is invalid and can't be "
                        "parsed".format(oid)
                    )

                value = handler(backend, ext_data)
                extensions.append(x509.Extension(oid, critical, value))

            seen_oids.add(oid)

        return x509.Extensions(extensions)


def _decode_certificate_policies(backend, cp):
    cp = backend._ffi.cast("Cryptography_STACK_OF_POLICYINFO *", cp)
    cp = backend._ffi.gc(cp, backend._lib.CERTIFICATEPOLICIES_free)

    num = backend._lib.sk_POLICYINFO_num(cp)
    certificate_policies = []
    for i in range(num):
        qualifiers = None
        pi = backend._lib.sk_POLICYINFO_value(cp, i)
        oid = x509.ObjectIdentifier(_obj2txt(backend, pi.policyid))
        if pi.qualifiers != backend._ffi.NULL:
            qnum = backend._lib.sk_POLICYQUALINFO_num(pi.qualifiers)
            qualifiers = []
            for j in range(qnum):
                pqi = backend._lib.sk_POLICYQUALINFO_value(
                    pi.qualifiers, j
                )
                pqualid = x509.ObjectIdentifier(
                    _obj2txt(backend, pqi.pqualid)
                )
                if pqualid == CertificatePoliciesOID.CPS_QUALIFIER:
                    cpsuri = backend._ffi.buffer(
                        pqi.d.cpsuri.data, pqi.d.cpsuri.length
                    )[:].decode('ascii')
                    qualifiers.append(cpsuri)
                else:
                    assert pqualid == CertificatePoliciesOID.CPS_USER_NOTICE
                    user_notice = _decode_user_notice(
                        backend, pqi.d.usernotice
                    )
                    qualifiers.append(user_notice)

        certificate_policies.append(
            x509.PolicyInformation(oid, qualifiers)
        )

    return x509.CertificatePolicies(certificate_policies)


def _decode_user_notice(backend, un):
    explicit_text = None
    notice_reference = None

    if un.exptext != backend._ffi.NULL:
        explicit_text = _asn1_string_to_utf8(backend, un.exptext)

    if un.noticeref != backend._ffi.NULL:
        organization = _asn1_string_to_utf8(
            backend, un.noticeref.organization
        )

        num = backend._lib.sk_ASN1_INTEGER_num(
            un.noticeref.noticenos
        )
        notice_numbers = []
        for i in range(num):
            asn1_int = backend._lib.sk_ASN1_INTEGER_value(
                un.noticeref.noticenos, i
            )
            notice_num = _asn1_integer_to_int(backend, asn1_int)
            notice_numbers.append(notice_num)

        notice_reference = x509.NoticeReference(
            organization, notice_numbers
        )

    return x509.UserNotice(notice_reference, explicit_text)


def _decode_basic_constraints(backend, bc_st):
    basic_constraints = backend._ffi.cast("BASIC_CONSTRAINTS *", bc_st)
    basic_constraints = backend._ffi.gc(
        basic_constraints, backend._lib.BASIC_CONSTRAINTS_free
    )
    # The byte representation of an ASN.1 boolean true is \xff. OpenSSL
    # chooses to just map this to its ordinal value, so true is 255 and
    # false is 0.
    ca = basic_constraints.ca == 255
    path_length = _asn1_integer_to_int_or_none(
        backend, basic_constraints.pathlen
    )

    return x509.BasicConstraints(ca, path_length)


def _decode_subject_key_identifier(backend, asn1_string):
    asn1_string = backend._ffi.cast("ASN1_OCTET_STRING *", asn1_string)
    asn1_string = backend._ffi.gc(
        asn1_string, backend._lib.ASN1_OCTET_STRING_free
    )
    return x509.SubjectKeyIdentifier(
        backend._ffi.buffer(asn1_string.data, asn1_string.length)[:]
    )


def _decode_authority_key_identifier(backend, akid):
    akid = backend._ffi.cast("AUTHORITY_KEYID *", akid)
    akid = backend._ffi.gc(akid, backend._lib.AUTHORITY_KEYID_free)
    key_identifier = None
    authority_cert_issuer = None