borg/src/borg/testsuite/key.py

import getpass
import os.path
import re
import tempfile
from binascii import hexlify, unhexlify, a2b_base64
from unittest.mock import MagicMock

import pytest

from ..crypto.key import bin_to_hex
from ..crypto.key import PlaintextKey, AuthenticatedKey, Blake2AuthenticatedKey
from ..crypto.key import RepoKey, KeyfileKey, Blake2RepoKey, Blake2KeyfileKey
from ..crypto.key import AESOCBRepoKey, AESOCBKeyfileKey, CHPORepoKey, CHPOKeyfileKey
from ..crypto.key import Blake2AESOCBRepoKey, Blake2AESOCBKeyfileKey, Blake2CHPORepoKey, Blake2CHPOKeyfileKey
from ..crypto.key import ID_HMAC_SHA_256, ID_BLAKE2b_256
from ..crypto.key import TAMRequiredError, TAMInvalid, TAMUnsupportedSuiteError, UnsupportedManifestError, UnsupportedKeyFormatError
from ..crypto.key import identify_key
from ..crypto.low_level import bytes_to_long
from ..crypto.low_level import IntegrityError as IntegrityErrorBase
from ..helpers import IntegrityError
from ..helpers import Location
from ..helpers import StableDict
from ..helpers import get_security_dir
from ..helpers import msgpack
from ..constants import KEY_ALGORITHMS


class TestKey:
    class MockArgs:
        location = Location(tempfile.mkstemp()[1])
        key_algorithm = "argon2"

    keyfile2_key_file = """
        BORG_KEY 0000000000000000000000000000000000000000000000000000000000000000
        hqlhbGdvcml0aG2mc2hhMjU2pGRhdGHaAN4u2SiN7hqISe3OA8raBWNuvHn1R50ZU7HVCn
        11vTJNEaj9soxUaIGcW+pAB2N5yYoKMg/sGCMuZa286iJ008DvN99rf/ORfcKrK2GmzslO
        N3uv9Tk9HtqV/Sq5zgM9xuY9rEeQGDQVQ+AOsFamJqSUrAemGJbJqw9IerXC/jN4XPnX6J
        pi1cXCFxHfDaEhmWrkdPNoZdirCv/eP/dOVOLmwU58YsS+MvkZNfEa16el/fSb/ENdrwJ/
        2aYMQrDdk1d5MYzkjotv/KpofNwPXZchu2EwH7OIHWQjEVL1DZWkaGFzaNoAIO/7qn1hr3
        F84MsMMiqpbz4KVICeBZhfAaTPs4W7BC63qml0ZXJhdGlvbnPOAAGGoKRzYWx02gAgLENQ
        2uVCoR7EnAoiRzn8J+orbojKtJlNCnQ31SSC8rendmVyc2lvbgE=""".strip()

    keyfile2_cdata = unhexlify(re.sub(r'\W', '', """
        0055f161493fcfc16276e8c31493c4641e1eb19a79d0326fad0291e5a9c98e5933
        00000000000003e8d21eaf9b86c297a8cd56432e1915bb
        """))
    keyfile2_id = unhexlify('c3fbf14bc001ebcc3cd86e696c13482ed071740927cd7cbe1b01b4bfcee49314')

    keyfile_blake2_key_file = """
        BORG_KEY 0000000000000000000000000000000000000000000000000000000000000000
        hqlhbGdvcml0aG2mc2hhMjU2pGRhdGHaAZ7VCsTjbLhC1ipXOyhcGn7YnROEhP24UQvOCi
        Oar1G+JpwgO9BIYaiCODUpzPuDQEm6WxyTwEneJ3wsuyeqyh7ru2xo9FAUKRf6jcqqZnan
        ycTfktkUC+CPhKR7W6MTu5fPvy99chyL09/RGdD15aswR5PjNoFu4626sfMrBReyPdlxqt
        F80m+fbNE/vln2Trqoz9EMHQ3IxjIK4q0m4Aj7TwCu7ZankFtwt898+tYsWE7lb2Ps/gXB
        F8PM/5wHpYps2AKhDCpwKp5HyqIqlF5IzR2ydL9QP20QBjp/rSi6b+xwrfxNJZfw78f8ef
        A2Yj7xIsxNQ0kmVmTL/UF6d7+Mw1JfurWrySiDU7QQ+RiZpWUZ0DdReB+e4zn6/KNKC884
        34SGywADuLIQe2FKU+5jBCbutEyEGILQbAR/cgeLy5+V2XwXMJh4ytwXVIeT6Lk+qhYAdz
        Klx4ub7XijKcOxJyBE+4k33DAhcfIT2r4/sxgMhXrIOEQPKsMAixzdcqVYkpou+6c4PZeL
        nr+UjfJwOqK1BlWk1NgwE4GXYIKkaGFzaNoAIAzjUtpBPPh6kItZtHQZvnQG6FpucZNfBC
        UTHFJg343jqml0ZXJhdGlvbnPOAAGGoKRzYWx02gAgz3YaUZZ/s+UWywj97EY5b4KhtJYi
        qkPqtDDxs2j/T7+ndmVyc2lvbgE=""".strip()

    keyfile_blake2_cdata = bytes.fromhex('04fdf9475cf2323c0ba7a99ddc011064f2e7d039f539f2e448'
                                         '0e6f5fc6ff9993d604040404040404098c8cee1c6db8c28947')
    # Verified against b2sum. Entire string passed to BLAKE2, including the padded 64 byte key contained in
    # keyfile_blake2_key_file above is
    # 19280471de95185ec27ecb6fc9edbb4f4db26974c315ede1cd505fab4250ce7cd0d081ea66946c
    # 95f0db934d5f616921efbd869257e8ded2bd9bd93d7f07b1a30000000000000000000000000000
    # 000000000000000000000000000000000000000000000000000000000000000000000000000000
    # 00000000000000000000007061796c6f6164
    #                       p a y l o a d
    keyfile_blake2_id = bytes.fromhex('d8bc68e961c79f99be39061589e5179b2113cd9226e07b08ddd4a1fef7ce93fb')

    @pytest.fixture
    def keys_dir(self, request, monkeypatch, tmpdir):
        monkeypatch.setenv('BORG_KEYS_DIR', str(tmpdir))
        return tmpdir

    @pytest.fixture(params=(
        # not encrypted
        PlaintextKey,
        AuthenticatedKey, Blake2AuthenticatedKey,
        # legacy crypto
        KeyfileKey, Blake2KeyfileKey,
        RepoKey, Blake2RepoKey,
        # new crypto
        AESOCBKeyfileKey, AESOCBRepoKey,
        Blake2AESOCBKeyfileKey, Blake2AESOCBRepoKey,
        CHPOKeyfileKey, CHPORepoKey,
        Blake2CHPOKeyfileKey, Blake2CHPORepoKey,
    ))
    def key(self, request, monkeypatch):
        monkeypatch.setenv('BORG_PASSPHRASE', 'test')
        return request.param.create(self.MockRepository(), self.MockArgs())

    class MockRepository:
        class _Location:
            raw = processed = '/some/place'

            def canonical_path(self):
                return self.processed

        _location = _Location()
        id = bytes(32)
        id_str = bin_to_hex(id)

        def get_free_nonce(self):
            return None

        def commit_nonce_reservation(self, next_unreserved, start_nonce):
            pass

        def save_key(self, data):
            self.key_data = data

        def load_key(self):
            return self.key_data

    def test_plaintext(self):
        key = PlaintextKey.create(None, None)
        chunk = b'foo'
        id = key.id_hash(chunk)
        assert hexlify(id) == b'2c26b46b68ffc68ff99b453c1d30413413422d706483bfa0f98a5e886266e7ae'
        assert chunk == key.decrypt(id, key.encrypt(id, chunk))

    def test_keyfile(self, monkeypatch, keys_dir):
        monkeypatch.setenv('BORG_PASSPHRASE', 'test')
        key = KeyfileKey.create(self.MockRepository(), self.MockArgs())
        assert key.cipher.next_iv() == 0
        chunk = b'ABC'
        id = key.id_hash(chunk)
        manifest = key.encrypt(id, chunk)
        assert key.cipher.extract_iv(manifest) == 0
        manifest2 = key.encrypt(id, chunk)
        assert manifest != manifest2
        assert key.decrypt(id, manifest) == key.decrypt(id, manifest2)
        assert key.cipher.extract_iv(manifest2) == 1
        iv = key.cipher.extract_iv(manifest)
        key2 = KeyfileKey.detect(self.MockRepository(), manifest)
        assert key2.cipher.next_iv() >= iv + key2.cipher.block_count(len(manifest) - KeyfileKey.PAYLOAD_OVERHEAD)
        # Key data sanity check
        assert len({key2.id_key, key2.enc_key, key2.enc_hmac_key}) == 3
        assert key2.chunk_seed != 0
        chunk = b'foo'
        id = key.id_hash(chunk)
        assert chunk == key2.decrypt(id, key.encrypt(id, chunk))

    def test_keyfile_kfenv(self, tmpdir, monkeypatch):
        keyfile = tmpdir.join('keyfile')
        monkeypatch.setenv('BORG_KEY_FILE', str(keyfile))
        monkeypatch.setenv('BORG_PASSPHRASE', 'testkf')
        assert not keyfile.exists()
        key = CHPOKeyfileKey.create(self.MockRepository(), self.MockArgs())
        assert keyfile.exists()
        chunk = b'ABC'
        chunk_id = key.id_hash(chunk)
        chunk_cdata = key.encrypt(chunk_id, chunk)
        key = CHPOKeyfileKey.detect(self.MockRepository(), chunk_cdata)
        assert chunk == key.decrypt(chunk_id, chunk_cdata)
        keyfile.remove()
        with pytest.raises(FileNotFoundError):
            CHPOKeyfileKey.detect(self.MockRepository(), chunk_cdata)

    def test_keyfile2(self, monkeypatch, keys_dir):
        with keys_dir.join('keyfile').open('w') as fd:
            fd.write(self.keyfile2_key_file)
        monkeypatch.setenv('BORG_PASSPHRASE', 'passphrase')
        key = KeyfileKey.detect(self.MockRepository(), self.keyfile2_cdata)
        assert key.decrypt(self.keyfile2_id, self.keyfile2_cdata) == b'payload'

    def test_keyfile2_kfenv(self, tmpdir, monkeypatch):
        keyfile = tmpdir.join('keyfile')
        with keyfile.open('w') as fd:
            fd.write(self.keyfile2_key_file)
        monkeypatch.setenv('BORG_KEY_FILE', str(keyfile))
        monkeypatch.setenv('BORG_PASSPHRASE', 'passphrase')
        key = KeyfileKey.detect(self.MockRepository(), self.keyfile2_cdata)
        assert key.decrypt(self.keyfile2_id, self.keyfile2_cdata) == b'payload'

    def test_keyfile_blake2(self, monkeypatch, keys_dir):
        with keys_dir.join('keyfile').open('w') as fd:
            fd.write(self.keyfile_blake2_key_file)
        monkeypatch.setenv('BORG_PASSPHRASE', 'passphrase')
        key = Blake2KeyfileKey.detect(self.MockRepository(), self.keyfile_blake2_cdata)
        assert key.decrypt(self.keyfile_blake2_id, self.keyfile_blake2_cdata) == b'payload'

    def _corrupt_byte(self, key, data, offset):
        data = bytearray(data)
        # note: we corrupt in a way so that even corruption of the unauthenticated encryption type byte
        # will trigger an IntegrityError (does not happen while we stay within TYPES_ACCEPTABLE).
        data[offset] ^= 64
        with pytest.raises(IntegrityErrorBase):
            key.decrypt(b'', data)

    def test_decrypt_integrity(self, monkeypatch, keys_dir):
        with keys_dir.join('keyfile').open('w') as fd:
            fd.write(self.keyfile2_key_file)
        monkeypatch.setenv('BORG_PASSPHRASE', 'passphrase')
        key = KeyfileKey.detect(self.MockRepository(), self.keyfile2_cdata)

        data = self.keyfile2_cdata
        for i in range(len(data)):
            self._corrupt_byte(key, data, i)

        with pytest.raises(IntegrityError):
            data = bytearray(self.keyfile2_cdata)
            id = bytearray(key.id_hash(data))  # corrupt chunk id
            id[12] = 0
            key.decrypt(id, data)

    def test_roundtrip(self, key):
        repository = key.repository
        plaintext = b'foo'
        id = key.id_hash(plaintext)
        encrypted = key.encrypt(id, plaintext)
        identified_key_class = identify_key(encrypted)
        assert identified_key_class == key.__class__
        loaded_key = identified_key_class.detect(repository, encrypted)
        decrypted = loaded_key.decrypt(id, encrypted)
        assert decrypted == plaintext

    def test_decrypt_decompress(self, key):
        plaintext = b'123456789'
        id = key.id_hash(plaintext)
        encrypted = key.encrypt(id, plaintext)
        assert key.decrypt(id, encrypted, decompress=False) != plaintext
        assert key.decrypt(id, encrypted) == plaintext

    def test_assert_id(self, key):
        plaintext = b'123456789'
        id = key.id_hash(plaintext)
        key.assert_id(id, plaintext)
        id_changed = bytearray(id)
        id_changed[0] ^= 1
        with pytest.raises(IntegrityError):
            key.assert_id(id_changed, plaintext)
        plaintext_changed = plaintext + b'1'
        with pytest.raises(IntegrityError):
            key.assert_id(id, plaintext_changed)

    def test_authenticated_encrypt(self, monkeypatch):
        monkeypatch.setenv('BORG_PASSPHRASE', 'test')
        key = AuthenticatedKey.create(self.MockRepository(), self.MockArgs())
        assert AuthenticatedKey.id_hash is ID_HMAC_SHA_256.id_hash
        assert len(key.id_key) == 32
        plaintext = b'123456789'
        id = key.id_hash(plaintext)
        authenticated = key.encrypt(id, plaintext)
        # 0x07 is the key TYPE, \x00ff identifies no compression / unknown level.
        assert authenticated == b'\x07\x00\xff' + plaintext

    def test_blake2_authenticated_encrypt(self, monkeypatch):
        monkeypatch.setenv('BORG_PASSPHRASE', 'test')
        key = Blake2AuthenticatedKey.create(self.MockRepository(), self.MockArgs())
        assert Blake2AuthenticatedKey.id_hash is ID_BLAKE2b_256.id_hash
        assert len(key.id_key) == 128
        plaintext = b'123456789'
        id = key.id_hash(plaintext)
        authenticated = key.encrypt(id, plaintext)
        # 0x06 is the key TYPE, 0x00ff identifies no compression / unknown level.
        assert authenticated == b'\x06\x00\xff' + plaintext


class TestTAM:
    @pytest.fixture
    def key(self, monkeypatch):
        monkeypatch.setenv('BORG_PASSPHRASE', 'test')
        return CHPOKeyfileKey.create(TestKey.MockRepository(), TestKey.MockArgs())

    def test_unpack_future(self, key):
        blob = b'\xc1\xc1\xc1\xc1foobar'
        with pytest.raises(UnsupportedManifestError):
            key.unpack_and_verify_manifest(blob)

        blob = b'\xc1\xc1\xc1'
        with pytest.raises(msgpack.UnpackException):
            key.unpack_and_verify_manifest(blob)

    def test_missing_when_required(self, key):
        blob = msgpack.packb({})
        with pytest.raises(TAMRequiredError):
            key.unpack_and_verify_manifest(blob)

    def test_missing(self, key):
        blob = msgpack.packb({})
        key.tam_required = False
        unpacked, verified = key.unpack_and_verify_manifest(blob)
        assert unpacked == {}
        assert not verified

    def test_unknown_type_when_required(self, key):
        blob = msgpack.packb({
            'tam': {
                'type': 'HMAC_VOLLBIT',
            },
        })
        with pytest.raises(TAMUnsupportedSuiteError):
            key.unpack_and_verify_manifest(blob)

    def test_unknown_type(self, key):
        blob = msgpack.packb({
            'tam': {
                'type': 'HMAC_VOLLBIT',
            },
        })
        key.tam_required = False
        unpacked, verified = key.unpack_and_verify_manifest(blob)
        assert unpacked == {}
        assert not verified

    @pytest.mark.parametrize('tam, exc', (
        ({}, TAMUnsupportedSuiteError),
        ({'type': b'\xff'}, TAMUnsupportedSuiteError),
        (None, TAMInvalid),
        (1234, TAMInvalid),
    ))
    def test_invalid(self, key, tam, exc):
        blob = msgpack.packb({
            'tam': tam,
        })
        with pytest.raises(exc):
            key.unpack_and_verify_manifest(blob)

    @pytest.mark.parametrize('hmac, salt', (
        ({}, bytes(64)),
        (bytes(64), {}),
        (None, bytes(64)),
        (bytes(64), None),
    ))
    def test_wrong_types(self, key, hmac, salt):
        data = {
            'tam': {
                'type': 'HKDF_HMAC_SHA512',
                'hmac': hmac,
                'salt': salt
            },
        }
        tam = data['tam']
        if hmac is None:
            del tam['hmac']
        if salt is None:
            del tam['salt']
        blob = msgpack.packb(data)
        with pytest.raises(TAMInvalid):
            key.unpack_and_verify_manifest(blob)

    def test_round_trip(self, key):
        data = {'foo': 'bar'}
        blob = key.pack_and_authenticate_metadata(data)
        assert blob.startswith(b'\x82')

        unpacked = msgpack.unpackb(blob)
        assert unpacked['tam']['type'] == 'HKDF_HMAC_SHA512'

        unpacked, verified = key.unpack_and_verify_manifest(blob)
        assert verified
        assert unpacked['foo'] == 'bar'
        assert 'tam' not in unpacked

    @pytest.mark.parametrize('which', ('hmac', 'salt'))
    def test_tampered(self, key, which):
        data = {'foo': 'bar'}
        blob = key.pack_and_authenticate_metadata(data)
        assert blob.startswith(b'\x82')

        unpacked = msgpack.unpackb(blob, object_hook=StableDict)
        assert len(unpacked['tam'][which]) == 64
        unpacked['tam'][which] = unpacked['tam'][which][0:32] + bytes(32)
        assert len(unpacked['tam'][which]) == 64
        blob = msgpack.packb(unpacked)

        with pytest.raises(TAMInvalid):
            key.unpack_and_verify_manifest(blob)


def test_decrypt_key_file_unsupported_algorithm():
    """We will add more algorithms in the future. We should raise a helpful error."""
    key = CHPOKeyfileKey(None)
    encrypted = msgpack.packb({
        'algorithm': 'THIS ALGORITHM IS NOT SUPPORTED',
        'version': 1,
    })

    with pytest.raises(UnsupportedKeyFormatError):
        key.decrypt_key_file(encrypted, "hello, pass phrase")


def test_decrypt_key_file_v2_is_unsupported():
    """There may eventually be a version 2 of the format. For now we should raise a helpful error."""
    key = CHPOKeyfileKey(None)
    encrypted = msgpack.packb({
        'version': 2,
    })

    with pytest.raises(UnsupportedKeyFormatError):
        key.decrypt_key_file(encrypted, "hello, pass phrase")


def test_key_file_roundtrip(monkeypatch):
    def to_dict(key):
        extract = 'repository_id', 'enc_key', 'enc_hmac_key', 'id_key', 'chunk_seed'
        return {a: getattr(key, a) for a in extract}

    repository = MagicMock(id=b'repository_id')
    monkeypatch.setenv('BORG_PASSPHRASE', "hello, pass phrase")

    save_me = AESOCBRepoKey.create(repository, args=MagicMock(key_algorithm='argon2'))
    saved = repository.save_key.call_args.args[0]
    repository.load_key.return_value = saved
    load_me = AESOCBRepoKey.detect(repository, manifest_data=None)

    assert to_dict(load_me) == to_dict(save_me)
    assert msgpack.unpackb(a2b_base64(saved))['algorithm'] == KEY_ALGORITHMS['argon2']