#***************************************************************************
#                                  _   _ ____  _
#  Project                     ___| | | |  _ \| |
#                             / __| | | | |_) | |
#                            | (__| |_| |  _ <| |___
#                             \___|\___/|_| \_\_____|
#
# Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
#
# This software is licensed as described in the file COPYING, which
# you should have received as part of this distribution. The terms
# are also available at https://curl.se/docs/copyright.html.
#
# You may opt to use, copy, modify, merge, publish, distribute and/or sell
# copies of the Software, and permit persons to whom the Software is
# furnished to do so, under the terms of the COPYING file.
#
# This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
# KIND, either express or implied.
#
# SPDX-License-Identifier: curl
#
###########################################################################
#
import base64
import ipaddress
import os
import re
import shutil
import subprocess
from datetime import datetime, timedelta, timezone
from typing import Any, List, Optional

from cryptography import x509
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives import hashes
from cryptography.hazmat.primitives._serialization import PublicFormat
from cryptography.hazmat.primitives.asymmetric import ec, rsa
from cryptography.hazmat.primitives.asymmetric.ec import EllipticCurvePrivateKey
from cryptography.hazmat.primitives.asymmetric.rsa import RSAPrivateKey
from cryptography.hazmat.primitives.serialization import (
    Encoding,
    NoEncryption,
    PrivateFormat,
    load_pem_private_key,
)
from cryptography.x509 import ExtendedKeyUsageOID, NameOID

EC_SUPPORTED = {}
EC_SUPPORTED.update([(curve.name.upper(), curve) for curve in [
    ec.SECP192R1,
    ec.SECP224R1,
    ec.SECP256R1,
    ec.SECP384R1,
]])


class CertError(Exception):
    """Error in certificate handling."""


def _private_key(key_type):
    if isinstance(key_type, str):
        key_type = key_type.upper()
        m = re.match(r'^(RSA)?(\d+)$', key_type)
        if m:
            key_type = int(m.group(2))

    if isinstance(key_type, int):
        return rsa.generate_private_key(
            public_exponent=65537,
            key_size=key_type,
            backend=default_backend()
        )
    if not isinstance(key_type, ec.EllipticCurve) and key_type in EC_SUPPORTED:
        key_type = EC_SUPPORTED[key_type]
    return ec.generate_private_key(
        curve=key_type,
        backend=default_backend()
    )


class CertificateSpec:

    def __init__(self, name: Optional[str] = None,
                 domains: Optional[List[str]] = None,
                 email: Optional[str] = None,
                 key_type: Optional[str] = None,
                 single_file: bool = False,
                 valid_from: timedelta = timedelta(days=-1),
                 valid_to: timedelta = timedelta(days=89),
                 client: bool = False,
                 check_valid: bool = True,
                 sub_specs: Optional[List['CertificateSpec']] = None):
        self._name = name
        self.domains = domains
        self.client = client
        self.email = email
        self.key_type = key_type
        self.single_file = single_file
        self.valid_from = valid_from
        self.valid_to = valid_to
        self.sub_specs = sub_specs
        self.check_valid = check_valid

    @property
    def name(self) -> Optional[str]:
        if self._name:
            return self._name
        if self.domains:
            return self.domains[0]
        return None

    @property
    def type(self) -> Optional[str]:
        if self.domains and len(self.domains):
            return "server"
        if self.client:
            return "client"
        if self.name:
            return "ca"
        return None


class Credentials:

    def __init__(self,
                 name: str,
                 cert: Any,
                 pkey: Any,
                 issuer: Optional['Credentials'] = None):
        self._name = name
        self._cert = cert
        self._pkey = pkey
        self._issuer = issuer
        self._cert_file = None
        self._pkey_file = None
        self._store = None
        self._combined_file = None

    @property
    def name(self) -> str:
        return self._name

    @property
    def subject(self) -> x509.Name:
        return self._cert.subject

    @property
    def key_type(self):
        if isinstance(self._pkey, RSAPrivateKey):
            return f"rsa{self._pkey.key_size}"
        if isinstance(self._pkey, EllipticCurvePrivateKey):
            return f"{self._pkey.curve.name}"
        raise CertError(f"unknown key type: {self._pkey}")

    @property
    def private_key(self) -> Any:
        return self._pkey

    def pub_sha256_b64(self) -> Any:
        pubkey = self._pkey.public_key()
        sha256 = hashes.Hash(algorithm=hashes.SHA256())
        sha256.update(pubkey.public_bytes(
            encoding=Encoding.DER,
            format=PublicFormat.SubjectPublicKeyInfo
        ))
        return base64.b64encode(sha256.finalize()).decode('utf8')

    @property
    def certificate(self) -> Any:
        return self._cert

    @property
    def cert_pem(self) -> bytes:
        return self._cert.public_bytes(Encoding.PEM)

    @property
    def pkey_pem(self) -> bytes:
        return self._pkey.private_bytes(
            Encoding.PEM,
            PrivateFormat.TraditionalOpenSSL if self.key_type.startswith('rsa') else PrivateFormat.PKCS8,
            NoEncryption())

    @property
    def issuer(self) -> Optional['Credentials']:
        return self._issuer

    def set_store(self, store: 'CertStore'):
        self._store = store

    def set_files(self, cert_file: str, pkey_file: Optional[str] = None,
                  combined_file: Optional[str] = None):
        self._cert_file = cert_file
        self._pkey_file = pkey_file
        self._combined_file = combined_file

    @property
    def cert_file(self) -> str:
        return self._cert_file

    @property
    def pkey_file(self) -> Optional[str]:
        return self._pkey_file

    @property
    def combined_file(self) -> Optional[str]:
        return self._combined_file

    @property
    def hashdir(self) -> Optional[str]:
        return os.path.join(self._store.path, 'hashdir')

    def get_first(self, name) -> Optional['Credentials']:
        creds = self._store.get_credentials_for_name(name) if self._store else []
        return creds[0] if len(creds) else None

    def get_credentials_for_name(self, name) -> List['Credentials']:
        return self._store.get_credentials_for_name(name) if self._store else []

    def issue_certs(self, specs: List[CertificateSpec],
                    chain: Optional[List['Credentials']] = None) -> List['Credentials']:
        return [self.issue_cert(spec=spec, chain=chain) for spec in specs]

    def issue_cert(self, spec: CertificateSpec,
                   chain: Optional[List['Credentials']] = None) -> 'Credentials':
        key_type = spec.key_type if spec.key_type else self.key_type
        creds = None
        if self._store:
            creds = self._store.load_credentials(
                name=spec.name, key_type=key_type, single_file=spec.single_file,
                issuer=self, check_valid=spec.check_valid)
        if creds is None:
            creds = TestCA.create_credentials(spec=spec, issuer=self, key_type=key_type,
                                              valid_from=spec.valid_from, valid_to=spec.valid_to)
            if self._store:
                self._store.save(creds, single_file=spec.single_file)
                if spec.type == "ca":
                    self._store.save_chain(creds, "ca", with_root=True)

        if spec.sub_specs:
            if self._store:
                sub_store = CertStore(fpath=os.path.join(self._store.path, creds.name))
                creds.set_store(sub_store)
            subchain = chain.copy() if chain else []
            subchain.append(self)
            creds.issue_certs(spec.sub_specs, chain=subchain)
        return creds

    def create_hashdir(self, openssl):
        os.makedirs(self.hashdir, exist_ok=True)
        p = subprocess.run(args=[
            openssl, 'x509', '-hash', '-noout', '-in', self.cert_file
        ], capture_output=True, text=True, check=True)
        cert_hname = f'{p.stdout.strip()}.0'
        shutil.copy(self.cert_file, os.path.join(self.hashdir, cert_hname))


class CertStore:

    def __init__(self, fpath: str):
        self._store_dir = fpath
        if not os.path.exists(self._store_dir):
            os.makedirs(self._store_dir)
        self._creds_by_name = {}

    @property
    def path(self) -> str:
        return self._store_dir

    def save(self, creds: Credentials, name: Optional[str] = None,
             chain: Optional[List[Credentials]] = None,
             single_file: bool = False) -> None:
        name = name if name is not None else creds.name
        cert_file = self.get_cert_file(name=name, key_type=creds.key_type)
        pkey_file = self.get_pkey_file(name=name, key_type=creds.key_type)
        comb_file = self.get_combined_file(name=name, key_type=creds.key_type)
        if single_file:
            pkey_file = None
        with open(cert_file, "wb") as fd:
            fd.write(creds.cert_pem)
            if chain:
                fd.writelines(c.cert_pem for c in chain)
            if pkey_file is None:
                fd.write(creds.pkey_pem)
        if pkey_file is not None:
            with open(pkey_file, "wb") as fd:
                fd.write(creds.pkey_pem)
        with open(comb_file, "wb") as fd:
            fd.write(creds.cert_pem)
            if chain:
                fd.writelines(c.cert_pem for c in chain)
            fd.write(creds.pkey_pem)
        creds.set_files(cert_file, pkey_file, comb_file)
        self._add_credentials(name, creds)

    def save_chain(self, creds: Credentials, infix: str, with_root=False):
        name = creds.name
        chain = [creds]
        while creds.issuer is not None:
            creds = creds.issuer
            chain.append(creds)
        if not with_root and len(chain) > 1:
            chain = chain[:-1]
        chain_file = os.path.join(self._store_dir, f'{name}-{infix}.pem')
        with open(chain_file, "wb") as fd:
            fd.writelines(c.cert_pem for c in chain)

    def _add_credentials(self, name: str, creds: Credentials):
        if name not in self._creds_by_name:
            self._creds_by_name[name] = []
        self._creds_by_name[name].append(creds)

    def get_credentials_for_name(self, name) -> List[Credentials]:
        return self._creds_by_name.get(name, [])

    def get_cert_file(self, name: str, key_type=None) -> str:
        key_infix = f".{key_type}" if key_type is not None else ""
        return os.path.join(self._store_dir, f'{name}{key_infix}.cert.pem')

    def get_pkey_file(self, name: str, key_type=None) -> str:
        key_infix = f".{key_type}" if key_type is not None else ""
        return os.path.join(self._store_dir, f'{name}{key_infix}.pkey.pem')

    def get_combined_file(self, name: str, key_type=None) -> str:
        return os.path.join(self._store_dir, f'{name}.pem')

    def load_pem_cert(self, fpath: str) -> x509.Certificate:
        with open(fpath) as fd:
            return x509.load_pem_x509_certificate("".join(fd.readlines()).encode())

    def load_pem_pkey(self, fpath: str):
        with open(fpath) as fd:
            return load_pem_private_key("".join(fd.readlines()).encode(), password=None)

    def load_credentials(self, name: str, key_type=None,
                         single_file: bool = False,
                         issuer: Optional[Credentials] = None,
                         check_valid: bool = False):
        cert_file = self.get_cert_file(name=name, key_type=key_type)
        pkey_file = cert_file if single_file else self.get_pkey_file(name=name, key_type=key_type)
        comb_file = self.get_combined_file(name=name, key_type=key_type)
        if os.path.isfile(cert_file) and os.path.isfile(pkey_file):
            cert = self.load_pem_cert(cert_file)
            pkey = self.load_pem_pkey(pkey_file)
            try:
                before = cert.not_valid_before_utc
                after = cert.not_valid_after_utc
            except AttributeError:  # cryptography < 42.0.0
                # the timestamps are already returned in UTC, just missing the time zone
                before = cert.not_valid_before.replace(tzinfo=timezone.utc)
                after = cert.not_valid_after.replace(tzinfo=timezone.utc)
            now = datetime.now(timezone.utc)
            if check_valid and ((after < now) or (before > now)):
                return None
            creds = Credentials(name=name, cert=cert, pkey=pkey, issuer=issuer)
            creds.set_store(self)
            creds.set_files(cert_file, pkey_file, comb_file)
            self._add_credentials(name, creds)
            return creds
        return None


class TestCA:

    @classmethod
    def create_root(cls, name: str, store_dir: str, key_type: str = "rsa2048") -> Credentials:
        store = CertStore(fpath=store_dir)
        creds = store.load_credentials(name="ca", key_type=key_type, issuer=None)
        if creds is None:
            creds = TestCA._make_ca_credentials(name=name, key_type=key_type)
            store.save(creds, name="ca")
            creds.set_store(store)
        return creds

    @staticmethod
    def create_credentials(spec: CertificateSpec, issuer: Credentials, key_type: Any,
                           valid_from: timedelta = timedelta(days=-1),
                           valid_to: timedelta = timedelta(days=89),
                           ) -> Credentials:
        """
        Create a certificate signed by this CA for the given domains.

        :returns: the certificate and private key PEM file paths
        """
        if spec.domains and len(spec.domains):
            return TestCA._make_server_credentials(name=spec.name, domains=spec.domains,
                                                   issuer=issuer, valid_from=valid_from,
                                                   valid_to=valid_to, key_type=key_type)
        if spec.client:
            return TestCA._make_client_credentials(name=spec.name, issuer=issuer,
                                                   email=spec.email, valid_from=valid_from,
                                                   valid_to=valid_to, key_type=key_type)
        if spec.name:
            return TestCA._make_ca_credentials(name=spec.name, issuer=issuer,
                                               valid_from=valid_from, valid_to=valid_to,
                                               key_type=key_type)
        raise CertError(f"unrecognized certificate specification: {spec}")

    @staticmethod
    def _make_x509_name(org_name: Optional[str] = None, common_name: Optional[str] = None, parent: x509.Name = None) -> x509.Name:
        name_pieces = []
        if org_name:
            oid = NameOID.ORGANIZATIONAL_UNIT_NAME if parent else NameOID.ORGANIZATION_NAME
            name_pieces.append(x509.NameAttribute(oid, org_name))
        elif common_name:
            name_pieces.append(x509.NameAttribute(NameOID.COMMON_NAME, common_name))
        if parent:
            name_pieces.extend(list(parent))
        return x509.Name(name_pieces)

    @staticmethod
    def _make_csr(
            subject: x509.Name,
            pkey: Any,
            issuer_subject: Optional[Credentials],
            valid_from_delta: Optional[timedelta] = None,
            valid_until_delta: Optional[timedelta] = None
    ) -> x509.CertificateBuilder:
        pubkey = pkey.public_key()
        issuer_subject = issuer_subject if issuer_subject is not None else subject

        valid_from = datetime.now(timezone.utc)
        if valid_until_delta is not None:
            valid_from += valid_from_delta
        valid_until = datetime.now(timezone.utc)
        if valid_until_delta is not None:
            valid_until += valid_until_delta

        return (
            x509.CertificateBuilder()
            .subject_name(subject)
            .issuer_name(issuer_subject)
            .public_key(pubkey)
            .not_valid_before(valid_from)
            .not_valid_after(valid_until)
            .serial_number(x509.random_serial_number())
            .add_extension(
                x509.SubjectKeyIdentifier.from_public_key(pubkey),
                critical=False,
            )
        )

    @staticmethod
    def _add_ca_usages(csr: Any) -> Any:
        return csr.add_extension(
            x509.BasicConstraints(ca=True, path_length=9),
            critical=True,
        ).add_extension(
            x509.KeyUsage(
                digital_signature=True,
                content_commitment=False,
                key_encipherment=False,
                data_encipherment=False,
                key_agreement=False,
                key_cert_sign=True,
                crl_sign=True,
                encipher_only=False,
                decipher_only=False),
            critical=True
        ).add_extension(
            x509.ExtendedKeyUsage([
                ExtendedKeyUsageOID.CLIENT_AUTH,
                ExtendedKeyUsageOID.SERVER_AUTH,
                ExtendedKeyUsageOID.CODE_SIGNING,
            ]),
            critical=True
        )

    @staticmethod
    def _add_leaf_usages(csr: Any, domains: List[str], issuer: Credentials) -> Any:
        names = []
        for name in domains:
            m = re.match(r'dns:(.+)', name)
            if m:
                names.append(x509.DNSName(m.group(1)))
            else:
                try:
                    names.append(x509.IPAddress(ipaddress.ip_address(name)))
                except ValueError:
                    names.append(x509.DNSName(name))

        return csr.add_extension(
            x509.BasicConstraints(ca=False, path_length=None),
            critical=True,
        ).add_extension(
            x509.AuthorityKeyIdentifier.from_issuer_subject_key_identifier(
                issuer.certificate.extensions.get_extension_for_class(
                    x509.SubjectKeyIdentifier).value),
            critical=False
        ).add_extension(
            x509.SubjectAlternativeName(names), critical=True,
        ).add_extension(
            x509.ExtendedKeyUsage([
                ExtendedKeyUsageOID.SERVER_AUTH,
            ]),
            critical=False
        )

    @staticmethod
    def _add_client_usages(csr: Any, issuer: Credentials, rfc82name: Optional[str] = None) -> Any:
        cert = csr.add_extension(
            x509.BasicConstraints(ca=False, path_length=None),
            critical=True,
        ).add_extension(
            x509.AuthorityKeyIdentifier.from_issuer_subject_key_identifier(
                issuer.certificate.extensions.get_extension_for_class(
                    x509.SubjectKeyIdentifier).value),
            critical=False
        )
        if rfc82name:
            cert.add_extension(
                x509.SubjectAlternativeName([x509.RFC822Name(rfc82name)]),
                critical=True,
            )
        cert.add_extension(
            x509.ExtendedKeyUsage([
                ExtendedKeyUsageOID.CLIENT_AUTH,
            ]),
            critical=True
        )
        return cert

    @staticmethod
    def _make_ca_credentials(name, key_type: Any,
                             issuer: Optional[Credentials] = None,
                             valid_from: timedelta = timedelta(days=-1),
                             valid_to: timedelta = timedelta(days=89),
                             ) -> Credentials:
        pkey = _private_key(key_type=key_type)
        if issuer is not None:
            issuer_subject = issuer.certificate.subject
            issuer_key = issuer.private_key
        else:
            issuer_subject = None
            issuer_key = pkey
        subject = TestCA._make_x509_name(org_name=name, parent=issuer.subject if issuer else None)
        csr = TestCA._make_csr(subject=subject,
                               issuer_subject=issuer_subject, pkey=pkey,
                               valid_from_delta=valid_from, valid_until_delta=valid_to)
        csr = TestCA._add_ca_usages(csr)
        cert = csr.sign(private_key=issuer_key,
                        algorithm=hashes.SHA256(),
                        backend=default_backend())
        return Credentials(name=name, cert=cert, pkey=pkey, issuer=issuer)

    @staticmethod
    def _make_server_credentials(name: str, domains: List[str], issuer: Credentials,
                                 key_type: Any,
                                 valid_from: timedelta = timedelta(days=-1),
                                 valid_to: timedelta = timedelta(days=89),
                                 ) -> Credentials:
        pkey = _private_key(key_type=key_type)
        subject = TestCA._make_x509_name(common_name=name, parent=issuer.subject)
        csr = TestCA._make_csr(subject=subject,
                               issuer_subject=issuer.certificate.subject, pkey=pkey,
                               valid_from_delta=valid_from, valid_until_delta=valid_to)
        csr = TestCA._add_leaf_usages(csr, domains=domains, issuer=issuer)
        cert = csr.sign(private_key=issuer.private_key,
                        algorithm=hashes.SHA256(),
                        backend=default_backend())
        return Credentials(name=name, cert=cert, pkey=pkey, issuer=issuer)

    @staticmethod
    def _make_client_credentials(name: str,
                                 issuer: Credentials, email: Optional[str],
                                 key_type: Any,
                                 valid_from: timedelta = timedelta(days=-1),
                                 valid_to: timedelta = timedelta(days=89),
                                 ) -> Credentials:
        pkey = _private_key(key_type=key_type)
        subject = TestCA._make_x509_name(common_name=name, parent=issuer.subject)
        csr = TestCA._make_csr(subject=subject,
                               issuer_subject=issuer.certificate.subject, pkey=pkey,
                               valid_from_delta=valid_from, valid_until_delta=valid_to)
        csr = TestCA._add_client_usages(csr, issuer=issuer, rfc82name=email)
        cert = csr.sign(private_key=issuer.private_key,
                        algorithm=hashes.SHA256(),
                        backend=default_backend())
        return Credentials(name=name, cert=cert, pkey=pkey, issuer=issuer)
