# SPDX-License-Identifier: GPL-2.0-only
# Copyright (C) 2021-2022 Stephan Gerhold
# See https://www.qualcomm.com/media/documents/files/secure-boot-and-image-authentication-technical-overview-v1-0.pdf
# Somewhat based on code snippets from https://cryptography.io/en/latest/x509/tutorial.html
from __future__ import annotations

from datetime import datetime
from typing import List

from cryptography import x509
from cryptography.hazmat.primitives import hashes, serialization
from cryptography.x509.oid import NameOID

# NOTE: The certificate chain generated by qtestsign is NOT meant
# to be secure. The private keys are listed here to make the
# resulting files reproducible. THESE KEYS SHOULD ONLY BE USED
# FOR TESTING AND NOT FOR A PROPER SECURE BOOT SETUP.

ROOT_KEY = serialization.load_pem_private_key(b"""
-----BEGIN PRIVATE KEY-----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	roOT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-----END PRIVATE KEY-----
""", password=None)

ATT_KEY = serialization.load_pem_private_key(b"""
-----BEGIN PRIVATE KEY-----
MIIEvQIBADANBgkqhkiG9w0BAQEFAASCBKcwggSjAgEAAoIBAQDT449phHltY2aV
QIvaT4PUgNS7wDybnnjVO88NGB5PjfUaWY99oDQgOLJlejyVVqRO2wHxLaUMsbuc
oe0XbgSFJgrnGvG6yPbjSXeIfV5k2dJG60S4Fg2mZ1ieSabuPVKLA03frhbATmIf
Q+VTMlWLgLVxcT04iqph6VpjehnYke0VPMuN7OM6RsIOEhLcje0bvL4YjTYXH5j4
mPquc/ZEj/n6WJ6VsS27QygOBbaiGqHs54QnQi4gcgIgUmkR/bl2wL5s+729RBzS
v1FZfA5gdM9uEG3ogLHOC2uk+1Nuqcdk/tQxd30/2ulXubqDku/nNY2RSJrwD	att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-----END PRIVATE KEY-----
""", password=None)


def _begin_cert() -> x509.CertificateBuilder:
	return x509.CertificateBuilder() \
		.serial_number(1) \
		.not_valid_before(datetime(2023, 1, 1)) \
		.not_valid_after(datetime(9999, 12, 31, 23, 59, 59))  # no well-defined expiration date, see RFC5280 4.1.2.5.


def generate_chain(ou_fields: List[str]) -> bytes:
	# First, create the root CA
	root_name = x509.Name([
		x509.NameAttribute(NameOID.COMMON_NAME, "qtestsign Root CA - NOT SECURE"),
	])
	# only key_cert_sign=True
	root_usage = x509.KeyUsage(False, False, False, False, False, True, False, False, False)
	root_ski = x509.SubjectKeyIdentifier.from_public_key(ROOT_KEY.public_key())
	root_cert_der = _begin_cert() \
		.subject_name(root_name) \
		.issuer_name(root_name) \
		.public_key(ROOT_KEY.public_key()) \
		.add_extension(x509.BasicConstraints(ca=True, path_length=0), critical=True) \
		.add_extension(root_usage, critical=True) \
		.add_extension(root_ski, critical=False) \
		.sign(ROOT_KEY, hashes.SHA256()) \
		.public_bytes(serialization.Encoding.DER)

	# Now, create the attestation certificate
	att_name = x509.Name([
		x509.NameAttribute(NameOID.COMMON_NAME, "qtestsign Attestation CA - NOT SECURE"),
		*[x509.NameAttribute(NameOID.ORGANIZATIONAL_UNIT_NAME, ou) for ou in ou_fields],
	])
	# only digital_signature=True
	att_usage = x509.KeyUsage(True, False, False, False, False, False, False, False, False)
	att_cert_der = _begin_cert() \
		.subject_name(att_name) \
		.issuer_name(root_name) \
		.public_key(ATT_KEY.public_key()) \
		.add_extension(x509.BasicConstraints(ca=False, path_length=None), critical=True) \
		.add_extension(att_usage, critical=True) \
		.add_extension(x509.SubjectKeyIdentifier.from_public_key(ATT_KEY.public_key()), critical=False) \
		.add_extension(x509.AuthorityKeyIdentifier.from_issuer_subject_key_identifier(root_ski), critical=False) \
		.sign(ROOT_KEY, hashes.SHA256()) \
		.public_bytes(serialization.Encoding.DER)

	# The certificate chain is the attestation and root certificate concatenated
	# in DER format. Note: The order (first attestation, then root) is important!
	return att_cert_der + root_cert_der