# -*- coding: utf-8 -*-
#
# (c) 2016, Yanis Guenane <yanis+ansible@guenane.org>
#
# Ansible 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 3 of the License, or
# (at your option) any later version.
#
# Ansible 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 Ansible.  If not, see <http://www.gnu.org/licenses/>.


try:
    from OpenSSL import crypto
except ImportError:
    # An error will be raised in the calling class to let the end
    # user know that OpenSSL couldn't be found.
    pass

try:
    from cryptography import x509
    from cryptography.hazmat.backends import default_backend as cryptography_backend
    from cryptography.hazmat.primitives.serialization import load_pem_private_key
    from cryptography.hazmat.primitives import hashes
    import ipaddress
except ImportError:
    # Error handled in the calling module.
    pass


import abc
import datetime
import errno
import hashlib
import os
import re

from ansible.module_utils import six
from ansible.module_utils._text import to_bytes, to_text


class OpenSSLObjectError(Exception):
    pass


class OpenSSLBadPassphraseError(OpenSSLObjectError):
    pass


def get_fingerprint_of_bytes(source):
    """Generate the fingerprint of the given bytes."""

    fingerprint = {}

    try:
        algorithms = hashlib.algorithms
    except AttributeError:
        try:
            algorithms = hashlib.algorithms_guaranteed
        except AttributeError:
            return None

    for algo in algorithms:
        f = getattr(hashlib, algo)
        h = f(source)
        try:
            # Certain hash functions have a hexdigest() which expects a length parameter
            pubkey_digest = h.hexdigest()
        except TypeError:
            pubkey_digest = h.hexdigest(32)
        fingerprint[algo] = ':'.join(pubkey_digest[i:i + 2] for i in range(0, len(pubkey_digest), 2))

    return fingerprint


def get_fingerprint(path, passphrase=None):
    """Generate the fingerprint of the public key. """

    privatekey = load_privatekey(path, passphrase, check_passphrase=False)
    try:
        publickey = crypto.dump_publickey(crypto.FILETYPE_ASN1, privatekey)
        return get_fingerprint_of_bytes(publickey)
    except AttributeError:
        # If PyOpenSSL < 16.0 crypto.dump_publickey() will fail.
        # By doing this we prevent the code from raising an error
        # yet we return no value in the fingerprint hash.
        return None


def load_privatekey(path, passphrase=None, check_passphrase=True, backend='pyopenssl'):
    """Load the specified OpenSSL private key."""

    try:
        with open(path, 'rb') as b_priv_key_fh:
            priv_key_detail = b_priv_key_fh.read()

        if backend == 'pyopenssl':

            # First try: try to load with real passphrase (resp. empty string)
            # Will work if this is the correct passphrase, or the key is not
            # password-protected.
            try:
                result = crypto.load_privatekey(crypto.FILETYPE_PEM,
                                                priv_key_detail,
                                                to_bytes(passphrase or ''))
            except crypto.Error as e:
                if len(e.args) > 0 and len(e.args[0]) > 0 and e.args[0][0][2] == 'bad decrypt':
                    # This happens in case we have the wrong passphrase.
                    if passphrase is not None:
                        raise OpenSSLBadPassphraseError('Wrong passphrase provided for private key!')
                    else:
                        raise OpenSSLBadPassphraseError('No passphrase provided, but private key is password-protected!')
                raise
            if check_passphrase:
                # Next we want to make sure that the key is actually protected by
                # a passphrase (in case we did try the empty string before, make
                # sure that the key is not protected by the empty string)
                try:
                    crypto.load_privatekey(crypto.FILETYPE_PEM,
                                           priv_key_detail,
                                           to_bytes('y' if passphrase == 'x' else 'x'))
                    if passphrase is not None:
                        # Since we can load the key without an exception, the
                        # key isn't password-protected
                        raise OpenSSLBadPassphraseError('Passphrase provided, but private key is not password-protected!')
                except crypto.Error as e:
                    if passphrase is None and len(e.args) > 0 and len(e.args[0]) > 0 and e.args[0][0][2] == 'bad decrypt':
                        # The key is obviously protected by the empty string.
                        # Don't do this at home (if it's possible at all)...
                        raise OpenSSLBadPassphraseError('No passphrase provided, but private key is password-protected!')
        elif backend == 'cryptography':
            try:
                result = load_pem_private_key(priv_key_detail,
                                              passphrase,
                                              cryptography_backend())
            except TypeError as dummy:
                raise OpenSSLBadPassphraseError('Wrong or empty passphrase provided for private key')
            except ValueError as dummy:
                raise OpenSSLBadPassphraseError('Wrong passphrase provided for private key')

        return result
    except (IOError, OSError) as exc:
        raise OpenSSLObjectError(exc)


def load_certificate(path, backend='pyopenssl'):
    """Load the specified certificate."""

    try:
        with open(path, 'rb') as cert_fh:
            cert_content = cert_fh.read()
        if backend == 'pyopenssl':
            return crypto.load_certificate(crypto.FILETYPE_PEM, cert_content)
        elif backend == 'cryptography':
            return x509.load_pem_x509_certificate(cert_content, cryptography_backend())
    except (IOError, OSError) as exc:
        raise OpenSSLObjectError(exc)


def load_certificate_request(path, backend='pyopenssl'):
    """Load the specified certificate signing request."""
    try:
        with open(path, 'rb') as csr_fh:
            csr_content = csr_fh.read()
    except (IOError, OSError) as exc:
        raise OpenSSLObjectError(exc)
    if backend == 'pyopenssl':
        return crypto.load_certificate_request(crypto.FILETYPE_PEM, csr_content)
    elif backend == 'cryptography':
        return x509.load_pem_x509_csr(csr_content, cryptography_backend())


def parse_name_field(input_dict):
    """Take a dict with key: value or key: list_of_values mappings and return a list of tuples"""

    result = []
    for key in input_dict:
        if isinstance(input_dict[key], list):
            for entry in input_dict[key]:
                result.append((key, entry))
        else:
            result.append((key, input_dict[key]))
    return result


def convert_relative_to_datetime(relative_time_string):
    """Get a datetime.datetime or None from a string in the time format described in sshd_config(5)"""

    parsed_result = re.match(
        r"^(?P<prefix>[+-])((?P<weeks>\d+)[wW])?((?P<days>\d+)[dD])?((?P<hours>\d+)[hH])?((?P<minutes>\d+)[mM])?((?P<seconds>\d+)[sS]?)?$",
        relative_time_string)

    if parsed_result is None or len(relative_time_string) == 1:
        # not matched or only a single "+" or "-"
        return None

    offset = datetime.timedelta(0)
    if parsed_result.group("weeks") is not None:
        offset += datetime.timedelta(weeks=int(parsed_result.group("weeks")))
    if parsed_result.group("days") is not None:
        offset += datetime.timedelta(days=int(parsed_result.group("days")))
    if parsed_result.group("hours") is not None:
        offset += datetime.timedelta(hours=int(parsed_result.group("hours")))
    if parsed_result.group("minutes") is not None:
        offset += datetime.timedelta(
            minutes=int(parsed_result.group("minutes")))
    if parsed_result.group("seconds") is not None:
        offset += datetime.timedelta(
            seconds=int(parsed_result.group("seconds")))

    if parsed_result.group("prefix") == "+":
        return datetime.datetime.utcnow() + offset
    else:
        return datetime.datetime.utcnow() - offset


def select_message_digest(digest_string):
    digest = None
    if digest_string == 'sha256':
        digest = hashes.SHA256()
    elif digest_string == 'sha384':
        digest = hashes.SHA384()
    elif digest_string == 'sha512':
        digest = hashes.SHA512()
    elif digest_string == 'sha1':
        digest = hashes.SHA1()
    elif digest_string == 'md5':
        digest = hashes.MD5()
    return digest


@six.add_metaclass(abc.ABCMeta)
class OpenSSLObject(object):

    def __init__(self, path, state, force, check_mode):
        self.path = path
        self.state = state
        self.force = force
        self.name = os.path.basename(path)
        self.changed = False
        self.check_mode = check_mode

    def check(self, module, perms_required=True):
        """Ensure the resource is in its desired state."""

        def _check_state():
            return os.path.exists(self.path)

        def _check_perms(module):
            file_args = module.load_file_common_arguments(module.params)
            return not module.set_fs_attributes_if_different(file_args, False)

        if not perms_required:
            return _check_state()

        return _check_state() and _check_perms(module)

    @abc.abstractmethod
    def dump(self):
        """Serialize the object into a dictionary."""

        pass

    @abc.abstractmethod
    def generate(self):
        """Generate the resource."""

        pass

    def remove(self, module):
        """Remove the resource from the filesystem."""

        try:
            os.remove(self.path)
            self.changed = True
        except OSError as exc:
            if exc.errno != errno.ENOENT:
                raise OpenSSLObjectError(exc)
            else:
                pass


def cryptography_get_name_oid(id):
    '''
    Given a symbolic ID, finds the appropriate OID for use with cryptography.
    Raises an OpenSSLObjectError if the ID is unknown.
    '''
    if id in ('CN', 'commonName'):
        return x509.oid.NameOID.COMMON_NAME
    if id in ('C', 'countryName'):
        return x509.oid.NameOID.COUNTRY_NAME
    if id in ('L', 'localityName'):
        return x509.oid.NameOID.LOCALITY_NAME
    if id in ('ST', 'stateOrProvinceName'):
        return x509.oid.NameOID.STATE_OR_PROVINCE_NAME
    if id in ('street', 'streetAddress'):
        return x509.oid.NameOID.STREET_ADDRESS
    if id in ('O', 'organizationName'):
        return x509.oid.NameOID.ORGANIZATION_NAME
    if id in ('OU', 'organizationalUnitName'):
        return x509.oid.NameOID.ORGANIZATIONAL_UNIT_NAME
    if id in ('serialNumber', ):
        return x509.oid.NameOID.SERIAL_NUMBER
    if id in ('SN', 'surname'):
        return x509.oid.NameOID.SURNAME
    if id in ('GN', 'givenName'):
        return x509.oid.NameOID.GIVEN_NAME
    if id in ('title', ):
        return x509.oid.NameOID.TITLE
    if id in ('generationQualifier', ):
        return x509.oid.NameOID.GENERATION_QUALIFIER
    if id in ('x500UniqueIdentifier', ):
        return x509.oid.NameOID.X500_UNIQUE_IDENTIFIER
    if id in ('dnQualifier', ):
        return x509.oid.NameOID.DN_QUALIFIER
    if id in ('pseudonym', ):
        return x509.oid.NameOID.PSEUDONYM
    if id in ('UID', 'userId'):
        return x509.oid.NameOID.USER_ID
    if id in ('DC', 'domainComponent'):
        return x509.oid.NameOID.DOMAIN_COMPONENT
    if id in ('emailAddress', ):
        return x509.oid.NameOID.EMAIL_ADDRESS
    if id in ('jurisdictionC', 'jurisdictionCountryName'):
        return x509.oid.NameOID.JURISDICTION_COUNTRY_NAME
    if id in ('jurisdictionL', 'jurisdictionLocalityName'):
        return x509.oid.NameOID.JURISDICTION_LOCALITY_NAME
    if id in ('jurisdictionST', 'jurisdictionStateOrProvinceName'):
        return x509.oid.NameOID.JURISDICTION_STATE_OR_PROVINCE_NAME
    if id in ('businessCategory', ):
        return x509.oid.NameOID.BUSINESS_CATEGORY
    if id in ('postalAddress', ):
        return x509.oid.NameOID.POSTAL_ADDRESS
    if id in ('postalCode', ):
        return x509.oid.NameOID.POSTAL_CODE
    raise OpenSSLObjectError('Unknown subject field identifier "{0}"'.format(id))


def cryptography_get_name(name):
    '''
    Given a name string, returns a cryptography x509.Name object.
    Raises an OpenSSLObjectError if the name is unknown or cannot be parsed.
    '''
    try:
        if name.startswith('DNS:'):
            return x509.DNSName(to_text(name[4:]))
        if name.startswith('IP:'):
            return x509.IPAddress(ipaddress.ip_address(to_text(name[3:])))
        if name.startswith('email:'):
            return x509.RFC822Name(to_text(name[6:]))
        if name.startswith('URI:'):
            return x509.UniformResourceIdentifier(to_text(name[4:]))
    except Exception as e:
        raise OpenSSLObjectError('Cannot parse Subject Alternative Name "{0}": {1}'.format(name, e))
    if ':' not in name:
        raise OpenSSLObjectError('Cannot parse Subject Alternative Name "{0}" (forgot "DNS:" prefix?)'.format(name))
    raise OpenSSLObjectError('Cannot parse Subject Alternative Name "{0}" (potentially unsupported by cryptography backend)'.format(name))


def _cryptography_get_keyusage(usage):
    '''
    Given a key usage identifier string, returns the parameter name used by cryptography's x509.KeyUsage().
    Raises an OpenSSLObjectError if the identifier is unknown.
    '''
    if usage in ('Digital Signature', 'digitalSignature'):
        return 'digital_signature'
    if usage in ('Non Repudiation', 'nonRepudiation'):
        return 'content_commitment'
    if usage in ('Key Encipherment', 'keyEncipherment'):
        return 'key_encipherment'
    if usage in ('Data Encipherment', 'dataEncipherment'):
        return 'data_encipherment'
    if usage in ('Key Agreement', 'keyAgreement'):
        return 'key_agreement'
    if usage in ('Certificate Sign', 'keyCertSign'):
        return 'key_cert_sign'
    if usage in ('CRL Sign', 'cRLSign'):
        return 'crl_sign'
    if usage in ('Encipher Only', 'encipherOnly'):
        return 'encipher_only'
    if usage in ('Decipher Only', 'decipherOnly'):
        return 'decipher_only'
    raise OpenSSLObjectError('Unknown key usage "{0}"'.format(usage))


def cryptography_parse_key_usage_params(usages):
    '''
    Given a list of key usage identifier strings, returns the parameters for cryptography's x509.KeyUsage().
    Raises an OpenSSLObjectError if an identifier is unknown.
    '''
    params = dict(
        digital_signature=False,
        content_commitment=False,
        key_encipherment=False,
        data_encipherment=False,
        key_agreement=False,
        key_cert_sign=False,
        crl_sign=False,
        encipher_only=False,
        decipher_only=False,
    )
    for usage in usages:
        params[_cryptography_get_keyusage(usage)] = True
    return params


def cryptography_get_ext_keyusage(usage):
    '''
    Given an extended key usage identifier string, returns the OID used by cryptography.
    Raises an OpenSSLObjectError if the identifier is unknown.
    '''
    if usage in ('serverAuth', 'TLS Web Server Authentication'):
        return x509.oid.ExtendedKeyUsageOID.SERVER_AUTH
    if usage in ('clientAuth', 'TLS Web Client Authentication'):
        return x509.oid.ExtendedKeyUsageOID.CLIENT_AUTH
    if usage in ('codeSigning', 'Code Signing'):
        return x509.oid.ExtendedKeyUsageOID.CODE_SIGNING
    if usage in ('emailProtection', 'E-mail Protection'):
        return x509.oid.ExtendedKeyUsageOID.EMAIL_PROTECTION
    if usage in ('timeStamping', 'Time Stamping'):
        return x509.oid.ExtendedKeyUsageOID.TIME_STAMPING
    if usage in ('OCSPSigning', 'OCSP Signing'):
        return x509.oid.ExtendedKeyUsageOID.OCSP_SIGNING
    if usage in ('anyExtendedKeyUsage', 'Any Extended Key Usage'):
        return x509.oid.ExtendedKeyUsageOID.ANY_EXTENDED_KEY_USAGE
    if usage in ('qcStatements', ):
        return x509.oid.ObjectIdentifier("1.3.6.1.5.5.7.1.3")
    if usage in ('DVCS', ):
        return x509.oid.ObjectIdentifier("1.3.6.1.5.5.7.3.10")
    if usage in ('IPSec User', 'ipsecUser'):
        return x509.oid.ObjectIdentifier("1.3.6.1.5.5.7.3.7")
    if usage in ('Biometric Info', 'biometricInfo'):
        return x509.oid.ObjectIdentifier("1.3.6.1.5.5.7.1.2")
    # FIXME need some more, probably all from https://www.iana.org/assignments/smi-numbers/smi-numbers.xhtml#smi-numbers-1.3.6.1.5.5.7.3
    raise OpenSSLObjectError('Unknown extended key usage "{0}"'.format(usage))


def cryptography_get_basic_constraints(constraints):
    '''
    Given a list of constraints, returns a tuple (ca, path_length).
    Raises an OpenSSLObjectError if a constraint is unknown or cannot be parsed.
    '''
    ca = False
    path_length = None
    if constraints:
        for constraint in constraints:
            if constraint.startswith('CA:'):
                if constraint == 'CA:TRUE':
                    ca = True
                elif constraint == 'CA:FALSE':
                    ca = False
                else:
                    raise OpenSSLObjectError('Unknown basic constraint value "{0}" for CA'.format(constraint[3:]))
            elif constraint.startswith('pathlen:'):
                v = constraint[len('pathlen:'):]
                try:
                    path_length = int(v)
                except Exception as e:
                    raise OpenSSLObjectError('Cannot parse path length constraint "{0}" ({1})'.format(v, e))
            else:
                raise OpenSSLObjectError('Unknown basic constraint "{0}"'.format(constraint))
    return ca, path_length