Python cryptography.hazmat.primitives.hashes.SHA256 Examples

def decrypt(input_str, key, iterations=100000):
    try:
        input_str = binascii.unhexlify(input_str)
        salt = b'D9\x82\xbfSibW(\xb1q\xeb\xd1\x84\x118'
        kdf = PBKDF2HMAC(
            algorithm=hashes.SHA256(),
            length=32,
            salt=salt,
            iterations=iterations,
            backend=default_backend()
        )
        key = base64.urlsafe_b64encode(kdf.derive(key.encode('utf-8')))
        fer = Fernet(key)
        h = fer.decrypt(input_str)
        h = h.decode('utf-8')
    except:
        raise
    return h 

def validate(self, authenticator_data, rp_id_hash, client_data_hash):
        # See https://www.w3.org/TR/webauthn/#fido-u2f-attestation, "Verification procedure"
        credential = authenticator_data.credential
        public_key_u2f = b'\x04' + credential.public_key.x + credential.public_key.y
        verification_data = b'\x00' + rp_id_hash + client_data_hash + credential.id + public_key_u2f
        assert len(credential.public_key.x) == 32
        assert len(credential.public_key.y) == 32
        self.cert_public_key.verify(self.signature, verification_data, ec.ECDSA(hashes.SHA256()))
        key_id = x509.SubjectKeyIdentifier.from_public_key(self.cert_public_key).digest.hex()
        att_root_cert_chain = self.metadata_for_key_id(key_id)["attestationRootCertificates"]

        # TODO: implement full cert chain validation
        # See https://cryptography.io/en/latest/x509/reference/#cryptography.x509.Certificate.tbs_certificate_bytes
        # See https://github.com/pyca/cryptography/issues/2381
        # See https://github.com/wbond/certvalidator
        assert len(att_root_cert_chain) == 1
        att_root_cert = x509.load_der_x509_certificate(att_root_cert_chain[0].encode(),
                                                       cryptography.hazmat.backends.default_backend())
        att_root_cert.public_key().verify(self.att_cert.signature,
                                          self.att_cert.tbs_certificate_bytes,
                                          padding.PKCS1v15(),
                                          self.att_cert.signature_hash_algorithm)
        return self.validated_attestation(type="Basic", trust_path="x5c", credential=credential) 

def decrypt(message, receiver_private_key):
    point = message[0:65]
    tag = message[65:81]
    ciphertext = message[81:]
    sender_public_numbers = ec.EllipticCurvePublicNumbers.from_encoded_point(ec.SECP256K1(), point)
    sender_public_key = sender_public_numbers.public_key(backend)
    shared_key = receiver_private_key.exchange(ec.ECDH(), sender_public_key)
    iv = '000000000000'
    xkdf = x963kdf.X963KDF(
        algorithm = hashes.SHA256(),
        length = 32,
        sharedinfo = '',
        backend = backend
        )
    key = xkdf.derive(shared_key)
    decryptor = Cipher(
        algorithms.AES(key),
        modes.GCM(iv,tag),
        backend = backend
        ).decryptor()
    message = decryptor.update(ciphertext) +  decryptor.finalize()
    return message 

def _encrypt_from_parts(self, data, current_time, iv):
        utils._check_bytes("data", data)

        padder = padding.PKCS7(algorithms.AES.block_size).padder()
        padded_data = padder.update(data) + padder.finalize()
        encryptor = Cipher(
            algorithms.AES(self._encryption_key), modes.CBC(iv), self._backend
        ).encryptor()
        ciphertext = encryptor.update(padded_data) + encryptor.finalize()

        basic_parts = (
            b"\x80" + struct.pack(">Q", current_time) + iv + ciphertext
        )

        h = HMAC(self._signing_key, hashes.SHA256(), backend=self._backend)
        h.update(basic_parts)
        hmac = h.finalize()
        return base64.urlsafe_b64encode(basic_parts + hmac) 

def encrypt(message, receiver_public_key):
    sender_private_key = ec.generate_private_key(ec.SECP256K1(), backend)
    shared_key = sender_private_key.exchange(ec.ECDH(), receiver_public_key)
    sender_public_key = sender_private_key.public_key()
    point = sender_public_key.public_numbers().encode_point()
    iv = '000000000000'
    xkdf = x963kdf.X963KDF(
        algorithm = hashes.SHA256(),
        length = 32,
        sharedinfo = '',
        backend = backend
        )
    key = xkdf.derive(shared_key)
    encryptor = Cipher(
        algorithms.AES(key),
        modes.GCM(iv),
        backend = backend
        ).encryptor()
    ciphertext = encryptor.update(message) + encryptor.finalize()
    return point + encryptor.tag + ciphertext 

def __init__(self, key, length, algorithm, backend,
                 enforce_key_length=True):
        if not isinstance(backend, HMACBackend):
            raise UnsupportedAlgorithm(
                "Backend object does not implement HMACBackend.",
                _Reasons.BACKEND_MISSING_INTERFACE
            )

        if len(key) < 16 and enforce_key_length is True:
            raise ValueError("Key length has to be at least 128 bits.")

        if not isinstance(length, six.integer_types):
            raise TypeError("Length parameter must be an integer type.")

        if length < 6 or length > 8:
            raise ValueError("Length of HOTP has to be between 6 to 8.")

        if not isinstance(algorithm, (SHA1, SHA256, SHA512)):
            raise TypeError("Algorithm must be SHA1, SHA256 or SHA512.")

        self._key = key
        self._length = length
        self._algorithm = algorithm
        self._backend = backend 

def __init__(self, key, length, algorithm, backend,
                 enforce_key_length=True):
        if not isinstance(backend, HMACBackend):
            raise UnsupportedAlgorithm(
                "Backend object does not implement HMACBackend.",
                _Reasons.BACKEND_MISSING_INTERFACE
            )

        if len(key) < 16 and enforce_key_length is True:
            raise ValueError("Key length has to be at least 128 bits.")

        if not isinstance(length, six.integer_types):
            raise TypeError("Length parameter must be an integer type.")

        if length < 6 or length > 8:
            raise ValueError("Length of HOTP has to be between 6 to 8.")

        if not isinstance(algorithm, (SHA1, SHA256, SHA512)):
            raise TypeError("Algorithm must be SHA1, SHA256 or SHA512.")

        self._key = key
        self._length = length
        self._algorithm = algorithm
        self._backend = backend 

def _derive_keys(self, password=None):
        label = encode(self.encryption_oid) + encode(self.mac_oid)
        context = self.nonce.asOctets()
        backend = default_backend()

        kdf = KBKDFHMAC(
            algorithm=hashes.SHA256(),
            mode=Mode.CounterMode,
            length=48,
            rlen=4,
            llen=4,
            location=CounterLocation.BeforeFixed,
            label=label,
            context=context,
            fixed=None,
            backend=backend
        )

        key = kdf.derive(password)
        if self.DEBUG:
            sys.stderr.write("Derived key: {0}\n".format(key))

        self.encryption_key = key[0:16]
        self.mac_key = key[16:] 

def _get_key():
    if this.key:
        return this.key

    secret = getpass.getpass()
    try:
        salt = config().get('Security', 'salt')
    except NoOptionError:
        salt = base64.urlsafe_b64encode(os.urandom(16))
        config().set('Security', 'salt', salt)

    kdf = PBKDF2HMAC(
        algorithm=hashes.SHA256(),
        length=32,
        salt=salt,
        iterations=100000,
        backend=default_backend()
    )
    this.key = base64.urlsafe_b64encode(kdf.derive(secret))
    return this.key 

def issue_certificate(self, ca_pem_key, ca_pem_cert, csr_pem):

        ca_cert = self.load_pem(entity_type="certificate", pem_text=ca_pem_cert)
        ca_key = self.load_pem(entity_type="key", pem_text=ca_pem_key)
        csr = self.load_pem(entity_type="csr", pem_text=csr_pem)

        builder = x509.CertificateBuilder(
            issuer_name=ca_cert.issuer,
            subject_name=csr.subject,
            public_key=csr.public_key(),
            not_valid_before=self.not_valid_before_date,
            not_valid_after=self.not_valid_after_date,
            extensions=csr.extensions,
            serial_number=self.serial_num,
        )

        certificate = builder.sign(
            private_key=ca_key,
            algorithm=hashes.SHA256(),
            backend=default_backend(),
        )

        self.pem_certificate = certificate.public_bytes(
            encoding=serialization.Encoding.PEM
        )

        return certificate 

def _encrypt_from_parts(self, data, current_time, iv):
        utils._check_bytes("data", data)

        padder = padding.PKCS7(algorithms.AES.block_size).padder()
        padded_data = padder.update(data) + padder.finalize()
        encryptor = Cipher(
            algorithms.AES(self._encryption_key), modes.CBC(iv), self._backend
        ).encryptor()
        ciphertext = encryptor.update(padded_data) + encryptor.finalize()

        basic_parts = (
            b"\x80" + struct.pack(">Q", current_time) + iv + ciphertext
        )

        h = HMAC(self._signing_key, hashes.SHA256(), backend=self._backend)
        h.update(basic_parts)
        hmac = h.finalize()
        return base64.urlsafe_b64encode(basic_parts + hmac) 

def __init__(self, key, length, algorithm, backend,
                 enforce_key_length=True):
        if not isinstance(backend, HMACBackend):
            raise UnsupportedAlgorithm(
                "Backend object does not implement HMACBackend.",
                _Reasons.BACKEND_MISSING_INTERFACE
            )

        if len(key) < 16 and enforce_key_length is True:
            raise ValueError("Key length has to be at least 128 bits.")

        if not isinstance(length, six.integer_types):
            raise TypeError("Length parameter must be an integer type.")

        if length < 6 or length > 8:
            raise ValueError("Length of HOTP has to be between 6 to 8.")

        if not isinstance(algorithm, (SHA1, SHA256, SHA512)):
            raise TypeError("Algorithm must be SHA1, SHA256 or SHA512.")

        self._key = key
        self._length = length
        self._algorithm = algorithm
        self._backend = backend 

def _encrypt_from_parts(self, data, current_time, iv):
        if not isinstance(data, bytes):
            raise TypeError("data must be bytes.")

        padder = padding.PKCS7(algorithms.AES.block_size).padder()
        padded_data = padder.update(data) + padder.finalize()
        encryptor = Cipher(
            algorithms.AES(self._encryption_key), modes.CBC(iv), self._backend
        ).encryptor()
        ciphertext = encryptor.update(padded_data) + encryptor.finalize()

        basic_parts = (
            b"\x80" + struct.pack(">Q", current_time) + iv + ciphertext
        )

        h = HMAC(self._signing_key, hashes.SHA256(), backend=self._backend)
        h.update(basic_parts)
        hmac = h.finalize()
        return base64.urlsafe_b64encode(basic_parts + hmac) 

def __init__(self, key, length, algorithm, backend,
                 enforce_key_length=True):
        if not isinstance(backend, HMACBackend):
            raise UnsupportedAlgorithm(
                "Backend object does not implement HMACBackend.",
                _Reasons.BACKEND_MISSING_INTERFACE
            )

        if len(key) < 16 and enforce_key_length is True:
            raise ValueError("Key length has to be at least 128 bits.")

        if not isinstance(length, six.integer_types):
            raise TypeError("Length parameter must be an integer type.")

        if length < 6 or length > 8:
            raise ValueError("Length of HOTP has to be between 6 to 8.")

        if not isinstance(algorithm, (SHA1, SHA256, SHA512)):
            raise TypeError("Algorithm must be SHA1, SHA256 or SHA512.")

        self._key = key
        self._length = length
        self._algorithm = algorithm
        self._backend = backend 

def _get_key(self, alg, key, p2s, p2c):
        if isinstance(key, bytes):
            plain = key
        else:
            plain = key.encode('utf8')
        salt = bytes(self.name.encode('utf8')) + b'\x00' + p2s

        if self.hashsize == 256:
            hashalg = hashes.SHA256()
        elif self.hashsize == 384:
            hashalg = hashes.SHA384()
        elif self.hashsize == 512:
            hashalg = hashes.SHA512()
        else:
            raise ValueError('Unknown Hash Size')

        kdf = PBKDF2HMAC(algorithm=hashalg, length=_inbytes(self.keysize),
                         salt=salt, iterations=p2c, backend=self.backend)
        rk = kdf.derive(plain)
        if _bitsize(rk) != self.keysize:
            raise InvalidJWEKeyLength(self.keysize, len(rk))
        return JWK(kty="oct", use="enc", k=base64url_encode(rk)) 

def _encrypt_from_parts(self, data, current_time, iv):
        if not isinstance(data, bytes):
            raise TypeError("data must be bytes.")

        padder = padding.PKCS7(algorithms.AES.block_size).padder()
        padded_data = padder.update(data) + padder.finalize()
        encryptor = Cipher(
            algorithms.AES(self._encryption_key), modes.CBC(iv), self._backend
        ).encryptor()
        ciphertext = encryptor.update(padded_data) + encryptor.finalize()

        basic_parts = (
            b"\x80" + struct.pack(">Q", current_time) + iv + ciphertext
        )

        h = HMAC(self._signing_key, hashes.SHA256(), backend=self._backend)
        h.update(basic_parts)
        hmac = h.finalize()
        return base64.urlsafe_b64encode(basic_parts + hmac) 

def encrypt(input_str, key, iterations=100000):
    """Basic encryption with a predefined key. Its purpose is to protect not very important data, just to avoid
    saving them as plaintext."""

    salt = b'D9\x82\xbfSibW(\xb1q\xeb\xd1\x84\x118'
    kdf = PBKDF2HMAC(
        algorithm=hashes.SHA256(),
        length=32,
        salt=salt,
        iterations=iterations,
        backend=default_backend()
    )
    key = base64.urlsafe_b64encode(kdf.derive(key.encode('utf-8')))
    fer = Fernet(key)
    h = fer.encrypt(input_str.encode('utf-8'))
    h = h.hex()
    return h 

def kdf(key_material: bytes) -> bytes:
    """NIST SP 800-56a Concatenation Key Derivation Function (see section 5.8.1).

    Pretty much copied from geth's implementation:
    https://github.com/ethereum/go-ethereum/blob/673007d7aed1d2678ea3277eceb7b55dc29cf092/crypto/ecies/ecies.go#L167
    """
    key = b""
    hash_blocksize = hashes.SHA256().block_size
    reps = ((KEY_LEN + 7) * 8) / (hash_blocksize * 8)
    counter = 0
    while counter <= reps:
        counter += 1
        ctx = sha256()
        ctx.update(struct.pack(">I", counter))
        ctx.update(key_material)
        key += ctx.digest()
    return key[:KEY_LEN] 

def __init__(self, key, length, algorithm, backend):
        if not isinstance(backend, HMACBackend):
            raise UnsupportedAlgorithm(
                "Backend object does not implement HMACBackend.",
                _Reasons.BACKEND_MISSING_INTERFACE
            )

        if len(key) < 16:
            raise ValueError("Key length has to be at least 128 bits.")

        if not isinstance(length, six.integer_types):
            raise TypeError("Length parameter must be an integer type.")

        if length < 6 or length > 8:
            raise ValueError("Length of HOTP has to be between 6 to 8.")

        if not isinstance(algorithm, (SHA1, SHA256, SHA512)):
            raise TypeError("Algorithm must be SHA1, SHA256 or SHA512.")

        self._key = key
        self._length = length
        self._algorithm = algorithm
        self._backend = backend 

def _encrypt_from_parts(self, data, current_time, iv):
        if not isinstance(data, bytes):
            raise TypeError("data must be bytes.")

        padder = padding.PKCS7(algorithms.AES.block_size).padder()
        padded_data = padder.update(data) + padder.finalize()
        encryptor = Cipher(
            algorithms.AES(self._encryption_key), modes.CBC(iv), self._backend
        ).encryptor()
        ciphertext = encryptor.update(padded_data) + encryptor.finalize()

        basic_parts = (
            b"\x80" + struct.pack(">Q", current_time) + iv + ciphertext
        )

        h = HMAC(self._signing_key, hashes.SHA256(), backend=self._backend)
        h.update(basic_parts)
        hmac = h.finalize()
        return base64.urlsafe_b64encode(basic_parts + hmac) 

def generate_signature(self, pri_key: str, msg: bytes) -> str:
        if self.__scheme == SignatureScheme.SHA224withECDSA:
            private_key = ec.derive_private_key(int(pri_key, 16), ec.SECP224R1(), default_backend())
            signature = private_key.sign(
                msg,
                ec.ECDSA(hashes.SHA224())
            )
        elif self.__scheme == SignatureScheme.SHA256withECDSA:
            private_key = ec.derive_private_key(int(pri_key, 16), ec.SECP256R1(), default_backend())
            signature = private_key.sign(
                msg,
                ec.ECDSA(hashes.SHA256())
            )
        elif self.__scheme == SignatureScheme.SHA384withECDSA:
            private_key = ec.derive_private_key(int(pri_key, 16), ec.SECP384R1(), default_backend())
            signature = private_key.sign(
                msg,
                ec.ECDSA(hashes.SHA384())
            )
        else:
            raise SDKException(ErrorCode.other_error('Invalid signature scheme.'))
        sign = SignatureHandler.dsa_der_to_plain(signature)
        return sign 

def sign(self, s):
        """
        Create a signature of the string s

        :param s: String to sign
        :type s: str
        :return: The hexlified and versioned signature of the string
        :rtype: str
        """
        if not self.private:
            log.info('Could not sign message {0!s}, no private key!'.format(s))
            # TODO: should we throw an exception in this case?
            return ''

        signature = self.private.sign(
            to_bytes(s),
            asym_padding.PSS(
                mgf=asym_padding.MGF1(hashes.SHA256()),
                salt_length=asym_padding.PSS.MAX_LENGTH),
            hashes.SHA256())
        res = ':'.join([self.sig_ver, hexlify_and_unicode(signature)])
        return res 

def _verify_signature(public_key, alg, data, signature):
    if alg == COSE_ALGORITHM.ES256:
        public_key.verify(signature, data, ECDSA(SHA256()))
    elif alg == COSE_ALGORITHM.RS256:
        public_key.verify(signature, data, PKCS1v15(), SHA256())
    elif alg == COSE_ALGORITHM.PS256:
        padding = PSS(mgf=MGF1(SHA256()), salt_length=PSS.MAX_LENGTH)
        public_key.verify(signature, data, padding, SHA256())
    else:
        raise NotImplementedError() 

def _mgf1_sha256_supported():
    wk = serialization.load_pem_private_key(
        data=VALUES["raw"][b"asym1"][EncryptionKeyType.PRIVATE], password=None, backend=default_backend()
    )
    try:
        wk.public_key().encrypt(
            plaintext=b"aosdjfoiajfoiaj;foijae;rogijaerg",
            padding=padding.OAEP(mgf=padding.MGF1(hashes.SHA256()), algorithm=hashes.SHA256(), label=None),
        )
    except cryptography.exceptions.UnsupportedAlgorithm:
        return False
    return True 

def _get_client_data_hash(decoded_client_data):
    """
    Compute the SHA256 hash of the client data.

    :param decoded_client_data: The client data to hash.
    :type decoded_client_data: bytes
    :return: The hash of the client data.
    :rtype: bytes
    """
    if not isinstance(decoded_client_data, six.binary_type):
        return ''

    return hashlib.sha256(decoded_client_data).digest() 

def _oaep_hash_supported(self, algorithm):
        if self._lib.Cryptography_HAS_RSA_OAEP_MD:
            return isinstance(
                algorithm, (
                    hashes.SHA1,
                    hashes.SHA224,
                    hashes.SHA256,
                    hashes.SHA384,
                    hashes.SHA512,
                )
            )
        else:
            return isinstance(algorithm, hashes.SHA1) 

def password(self, raw_password, salt):
        kdf = PBKDF2HMAC(
            algorithm=hashes.SHA256(),
            length=32,
            salt=salt,
            iterations=100000,
            backend=default_backend())
        return urlsafe_b64encode(kdf.derive(raw_password.encode("utf-8"))) 

def decrypt(message_encrypted, secret_key):
    message_salt = message_encrypted[-24:]
    message_payload = message_encrypted[:-24]
    salt = base64.b64decode(message_salt)
    kdf = PBKDF2HMAC(
        algorithm=hashes.SHA256(),
        length=32,
        salt=salt,
        iterations=100000,
        backend=backend
    )
    key = base64.urlsafe_b64encode(kdf.derive(bytes(secret_key, encoding='utf8')))
    f = Fernet(key)
    return f.decrypt(bytes(message_payload, encoding='latin1')).decode('utf8') 

def get_hashing_class(hash_algorithm_id):
  """
  <Purpose>
    Return a pyca/cryptography hashing class reference for the passed RFC4880
    hash algorithm ID.

  <Arguments>
    hash_algorithm_id:
            one of SHA1, SHA256, SHA512 (see securesystemslib.gpg.constants)

  <Exceptions>
    ValueError
            if the passed hash_algorithm_id is not supported.

  <Returns>
    A pyca/cryptography hashing class

  """
  supported_hashing_algorithms = [securesystemslib.gpg.constants.SHA1,
      securesystemslib.gpg.constants.SHA256,
      securesystemslib.gpg.constants.SHA512]
  corresponding_hashing_classes = [hashing.SHA1, hashing.SHA256,
      hashing.SHA512]

  # Map supported hash algorithm ids to corresponding hashing classes
  hashing_class = dict(zip(supported_hashing_algorithms,
      corresponding_hashing_classes))

  try:
    return hashing_class[hash_algorithm_id]

  except KeyError:
    raise ValueError("Hash algorithm '{}' not supported, must be one of '{}' "
        "(see RFC4880 9.4. Hash Algorithms).".format(hash_algorithm_id,
        supported_hashing_algorithms)) 

def test_get_hashing_class(self):
    # Assert return expected hashing class
    expected_hashing_class = [hashing.SHA1, hashing.SHA256, hashing.SHA512]
    for idx, hashing_id in enumerate([SHA1, SHA256, SHA512]):
      result = get_hashing_class(hashing_id)
      self.assertEqual(result, expected_hashing_class[idx])

    # Assert raises ValueError with non-supported hashing id
    with self.assertRaises(ValueError):
      get_hashing_class("bogus_hashing_id")