File: test_fernet.py

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# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
# implied.
# See the License for the specific language governing permissions and
# limitations under the License.

from __future__ import absolute_import, division, print_function

import base64
import calendar
import json
import time

import iso8601

import pytest

import six

from cryptography.fernet import Fernet, InvalidToken
from cryptography.hazmat.backends import default_backend
from cryptography.hazmat.primitives.ciphers import algorithms, modes

import cryptography_vectors


def json_parametrize(keys, filename):
    vector_file = cryptography_vectors.open_vector_file('fernet', filename)
    with vector_file:
        data = json.load(vector_file)
        return pytest.mark.parametrize(keys, [
            tuple([entry[k] for k in keys])
            for entry in data
        ])


@pytest.mark.cipher
class TestFernet(object):
    @pytest.mark.supported(
        only_if=lambda backend: backend.cipher_supported(
            algorithms.AES("\x00" * 32), modes.CBC("\x00" * 16)
        ),
        skip_message="Does not support AES CBC",
    )
    @json_parametrize(
        ("secret", "now", "iv", "src", "token"), "generate.json",
    )
    def test_generate(self, secret, now, iv, src, token, backend):
        f = Fernet(secret.encode("ascii"), backend=backend)
        actual_token = f._encrypt_from_parts(
            src.encode("ascii"),
            calendar.timegm(iso8601.parse_date(now).utctimetuple()),
            b"".join(map(six.int2byte, iv))
        )
        assert actual_token == token.encode("ascii")

    @pytest.mark.supported(
        only_if=lambda backend: backend.cipher_supported(
            algorithms.AES("\x00" * 32), modes.CBC("\x00" * 16)
        ),
        skip_message="Does not support AES CBC",
    )
    @json_parametrize(
        ("secret", "now", "src", "ttl_sec", "token"), "verify.json",
    )
    def test_verify(self, secret, now, src, ttl_sec, token, backend,
                    monkeypatch):
        f = Fernet(secret.encode("ascii"), backend=backend)
        current_time = calendar.timegm(iso8601.parse_date(now).utctimetuple())
        monkeypatch.setattr(time, "time", lambda: current_time)
        payload = f.decrypt(token.encode("ascii"), ttl=ttl_sec)
        assert payload == src.encode("ascii")

    @pytest.mark.supported(
        only_if=lambda backend: backend.cipher_supported(
            algorithms.AES("\x00" * 32), modes.CBC("\x00" * 16)
        ),
        skip_message="Does not support AES CBC",
    )
    @json_parametrize(("secret", "token", "now", "ttl_sec"), "invalid.json")
    def test_invalid(self, secret, token, now, ttl_sec, backend, monkeypatch):
        f = Fernet(secret.encode("ascii"), backend=backend)
        current_time = calendar.timegm(iso8601.parse_date(now).utctimetuple())
        monkeypatch.setattr(time, "time", lambda: current_time)
        with pytest.raises(InvalidToken):
            f.decrypt(token.encode("ascii"), ttl=ttl_sec)

    @pytest.mark.supported(
        only_if=lambda backend: backend.cipher_supported(
            algorithms.AES("\x00" * 32), modes.CBC("\x00" * 16)
        ),
        skip_message="Does not support AES CBC",
    )
    def test_invalid_start_byte(self, backend):
        f = Fernet(Fernet.generate_key(), backend=backend)
        with pytest.raises(InvalidToken):
            f.decrypt(base64.urlsafe_b64encode(b"\x81"))

    @pytest.mark.supported(
        only_if=lambda backend: backend.cipher_supported(
            algorithms.AES("\x00" * 32), modes.CBC("\x00" * 16)
        ),
        skip_message="Does not support AES CBC",
    )
    def test_timestamp_too_short(self, backend):
        f = Fernet(Fernet.generate_key(), backend=backend)
        with pytest.raises(InvalidToken):
            f.decrypt(base64.urlsafe_b64encode(b"\x80abc"))

    @pytest.mark.supported(
        only_if=lambda backend: backend.cipher_supported(
            algorithms.AES("\x00" * 32), modes.CBC("\x00" * 16)
        ),
        skip_message="Does not support AES CBC",
    )
    def test_unicode(self, backend):
        f = Fernet(base64.urlsafe_b64encode(b"\x00" * 32), backend=backend)
        with pytest.raises(TypeError):
            f.encrypt(six.u(""))
        with pytest.raises(TypeError):
            f.decrypt(six.u(""))

    @pytest.mark.supported(
        only_if=lambda backend: backend.cipher_supported(
            algorithms.AES("\x00" * 32), modes.CBC("\x00" * 16)
        ),
        skip_message="Does not support AES CBC",
    )
    @pytest.mark.parametrize("message", [b"", b"Abc!", b"\x00\xFF\x00\x80"])
    def test_roundtrips(self, message, backend):
        f = Fernet(Fernet.generate_key(), backend=backend)
        assert f.decrypt(f.encrypt(message)) == message

    def test_default_backend(self):
        f = Fernet(Fernet.generate_key())
        assert f._backend is default_backend()

    @pytest.mark.supported(
        only_if=lambda backend: backend.cipher_supported(
            algorithms.AES("\x00" * 32), modes.CBC("\x00" * 16)
        ),
        skip_message="Does not support AES CBC",
    )
    def test_bad_key(self, backend):
        with pytest.raises(ValueError):
            Fernet(base64.urlsafe_b64encode(b"abc"), backend=backend)