general.py

"""General key class."""

# SPDX-License-Identifier: Apache-2.0

import os
import sys

from cryptography.hazmat.primitives.asymmetric.types import PrivateKeyTypes, PublicKeyTypes
from cryptography.hazmat.primitives.hashes import Hash, SHA256

from imgtool import keys

AUTOGEN_MESSAGE = "/* Autogenerated by imgtool.py, do not edit. */"


def key_types_matching(key: PrivateKeyTypes, enckey: PublicKeyTypes):
    type_dict = {keys.ECDSA256P1: keys.ECDSA256P1Public,
                 keys.ECDSA384P1: keys.ECDSA384P1Public,
                 keys.Ed25519: keys.X25519Public,
                 keys.RSA: keys.RSAPublic}
    return type_dict[type(key)] == type(enckey)


class FileHandler(object):
    def __init__(self, file, *args, **kwargs):
        self.file_in = file
        self.args = args
        self.kwargs = kwargs

    def __enter__(self):
        if isinstance(self.file_in, (str, bytes, os.PathLike)):
            self.file = open(self.file_in, *self.args, **self.kwargs)
        else:
            self.file = self.file_in
        return self.file

    def __exit__(self, *args):
        if self.file != self.file_in:
            self.file.close()


class KeyClass(object):
    def _emit(self, header, trailer, encoded_bytes, indent, file=sys.stdout,
              len_format=None):
        with FileHandler(file, 'w') as file:
            self._emit_to_output(header, trailer, encoded_bytes, indent,
                                 file, len_format)

    def _emit_to_output(self, header, trailer, encoded_bytes, indent, file,
                        len_format):
        print(AUTOGEN_MESSAGE, file=file)
        print(header, end='', file=file)
        for count, b in enumerate(encoded_bytes):
            if count % 8 == 0:
                print("\n" + indent, end='', file=file)
            else:
                print(" ", end='', file=file)
            print("0x{:02x},".format(b), end='', file=file)
        print("\n" + trailer, file=file)
        if len_format is not None:
            print(len_format.format(len(encoded_bytes)), file=file)

    def _emit_raw(self, encoded_bytes, file):
        with FileHandler(file, 'wb') as file:
            try:
                # file.buffer is not part of the TextIOBase API
                # and may not exist in some implementations.
                file.buffer.write(encoded_bytes)
            except AttributeError:
                # raw binary data, can be for example io.BytesIO
                file.write(encoded_bytes)

    def emit_c_public(self, file=sys.stdout):
        self._emit(
            header="const unsigned char {}_pub_key[] = {{"
            .format(self.shortname()),
            trailer="};",
            encoded_bytes=self.get_public_bytes(),
            indent="    ",
            len_format="const unsigned int {}_pub_key_len = {{}};"
            .format(self.shortname()),
            file=file)

    def emit_c_public_hash(self, file=sys.stdout):
        digest = Hash(SHA256())
        digest.update(self.get_public_bytes())
        self._emit(
            header="const unsigned char {}_pub_key_hash[] = {{"
            .format(self.shortname()),
            trailer="};",
            encoded_bytes=digest.finalize(),
            indent="    ",
            len_format="const unsigned int {}_pub_key_hash_len = {{}};"
            .format(self.shortname()),
            file=file)

    def emit_raw_public(self, file=sys.stdout):
        self._emit_raw(self.get_public_bytes(), file=file)

    def emit_raw_public_hash(self, file=sys.stdout):
        digest = Hash(SHA256())
        digest.update(self.get_public_bytes())
        self._emit_raw(digest.finalize(), file=file)

    def emit_rust_public(self, file=sys.stdout):
        self._emit(
            header="static {}_PUB_KEY: &[u8] = &["
            .format(self.shortname().upper()),
            trailer="];",
            encoded_bytes=self.get_public_bytes(),
            indent="    ",
            file=file)

    def emit_public_pem(self, file=sys.stdout):
        with FileHandler(file, 'w') as file:
            print(str(self.get_public_pem(), 'utf-8'), file=file, end='')

    def emit_private(self, minimal, format, file=sys.stdout):
        self._emit(
            header="const unsigned char enc_priv_key[] = {",
            trailer="};",
            encoded_bytes=self.get_private_bytes(minimal, format),
            indent="    ",
            len_format="const unsigned int enc_priv_key_len = {};",
            file=file)