PyORAm
[iotcloud.git] / PyORAM / src / pyoram / tests / test_path_oram.py
diff --git a/PyORAM/src/pyoram/tests/test_path_oram.py b/PyORAM/src/pyoram/tests/test_path_oram.py
new file mode 100644 (file)
index 0000000..e5875b1
--- /dev/null
@@ -0,0 +1,851 @@
+import os
+import unittest2
+import tempfile
+
+from pyoram.oblivious_storage.tree.path_oram import \
+    PathORAM
+from pyoram.storage.block_storage import \
+    BlockStorageTypeFactory
+from pyoram.encrypted_storage.encrypted_heap_storage import \
+    EncryptedHeapStorage
+from pyoram.crypto.aes import AES
+
+from six.moves import xrange
+
+thisdir = os.path.dirname(os.path.abspath(__file__))
+
+class _TestPathORAMBase(object):
+
+    _type_name = None
+    _aes_mode = None
+    _test_key = None
+    _test_key_size = None
+    _bucket_capacity = None
+    _heap_base = None
+    _kwds = None
+
+    @classmethod
+    def setUpClass(cls):
+        assert cls._type_name is not None
+        assert cls._aes_mode is not None
+        assert not ((cls._test_key is not None) and \
+                    (cls._test_key_size is not None))
+        assert cls._bucket_capacity is not None
+        assert cls._heap_base is not None
+        assert cls._kwds is not None
+        fd, cls._dummy_name = tempfile.mkstemp()
+        os.close(fd)
+        try:
+            os.remove(cls._dummy_name)
+        except OSError:                                # pragma: no cover
+            pass                                       # pragma: no cover
+        cls._block_size = 25
+        cls._block_count = 47
+        cls._testfname = cls.__name__ + "_testfile.bin"
+        cls._blocks = []
+        f = PathORAM.setup(
+            cls._testfname,
+            cls._block_size,
+            cls._block_count,
+            bucket_capacity=cls._bucket_capacity,
+            heap_base=cls._heap_base,
+            key_size=cls._test_key_size,
+            key=cls._test_key,
+            storage_type=cls._type_name,
+            aes_mode=cls._aes_mode,
+            initialize=lambda i: bytes(bytearray([i])*cls._block_size),
+            ignore_existing=True,
+            **cls._kwds)
+        f.close()
+        cls._key = f.key
+        cls._stash = f.stash
+        cls._position_map = f.position_map
+        for i in range(cls._block_count):
+            data = bytearray([i])*cls._block_size
+            cls._blocks.append(data)
+
+    @classmethod
+    def tearDownClass(cls):
+        try:
+            os.remove(cls._testfname)
+        except OSError:                                # pragma: no cover
+            pass                                       # pragma: no cover
+        try:
+            os.remove(cls._dummy_name)
+        except OSError:                                # pragma: no cover
+            pass                                       # pragma: no cover
+
+    def test_setup_fails(self):
+        self.assertEqual(os.path.exists(self._dummy_name), False)
+        with self.assertRaises(IOError):
+            PathORAM.setup(
+                os.path.join(thisdir,
+                             "baselines",
+                             "exists.empty"),
+                block_size=10,
+                block_count=10,
+                bucket_capacity=self._bucket_capacity,
+                heap_base=self._heap_base,
+                key=self._test_key,
+                key_size=self._test_key_size,
+                aes_mode=self._aes_mode,
+                storage_type=self._type_name,
+                **self._kwds)
+        self.assertEqual(os.path.exists(self._dummy_name), False)
+        with self.assertRaises(IOError):
+            PathORAM.setup(
+                os.path.join(thisdir,
+                             "baselines",
+                             "exists.empty"),
+                block_size=10,
+                block_count=10,
+                bucket_capacity=self._bucket_capacity,
+                heap_base=self._heap_base,
+                key=self._test_key,
+                key_size=self._test_key_size,
+                storage_type=self._type_name,
+                aes_mode=self._aes_mode,
+                ignore_existing=False,
+                **self._kwds)
+        self.assertEqual(os.path.exists(self._dummy_name), False)
+        with self.assertRaises(ValueError):
+            PathORAM.setup(
+                self._dummy_name,
+                block_size=1,
+                block_count=0,
+                bucket_capacity=self._bucket_capacity,
+                heap_base=self._heap_base,
+                key=self._test_key,
+                key_size=self._test_key_size,
+                aes_mode=self._aes_mode,
+                storage_type=self._type_name,
+                **self._kwds)
+        self.assertEqual(os.path.exists(self._dummy_name), False)
+        with self.assertRaises(ValueError):
+            PathORAM.setup(
+                self._dummy_name,
+                block_size=0,
+                block_count=1,
+                bucket_capacity=self._bucket_capacity,
+                heap_base=self._heap_base,
+                key=self._test_key,
+                key_size=self._test_key_size,
+                aes_mode=self._aes_mode,
+                storage_type=self._type_name,
+                **self._kwds)
+        self.assertEqual(os.path.exists(self._dummy_name), False)
+        with self.assertRaises(TypeError):
+            PathORAM.setup(
+                self._dummy_name,
+                block_size=1,
+                block_count=1,
+                bucket_capacity=self._bucket_capacity,
+                heap_base=self._heap_base,
+                key=self._test_key,
+                key_size=self._test_key_size,
+                aes_mode=self._aes_mode,
+                storage_type=self._type_name,
+                header_data=2,
+                **self._kwds)
+        self.assertEqual(os.path.exists(self._dummy_name), False)
+        with self.assertRaises(ValueError):
+            PathORAM.setup(
+                self._dummy_name,
+                block_size=1,
+                block_count=1,
+                bucket_capacity=self._bucket_capacity,
+                heap_base=self._heap_base,
+                key=self._test_key,
+                key_size=self._test_key_size,
+                aes_mode=None,
+                storage_type=self._type_name,
+                **self._kwds)
+        self.assertEqual(os.path.exists(self._dummy_name), False)
+        with self.assertRaises(ValueError):
+            PathORAM.setup(
+                self._dummy_name,
+                block_size=1,
+                block_count=1,
+                bucket_capacity=0,
+                heap_base=self._heap_base,
+                key=self._test_key,
+                key_size=self._test_key_size,
+                aes_mode=self._aes_mode,
+                storage_type=self._type_name,
+                **self._kwds)
+        self.assertEqual(os.path.exists(self._dummy_name), False)
+        with self.assertRaises(ValueError):
+            PathORAM.setup(
+                self._dummy_name,
+                block_size=1,
+                block_count=1,
+                bucket_capacity=self._bucket_capacity,
+                heap_base=1,
+                key=self._test_key,
+                key_size=self._test_key_size,
+                aes_mode=self._aes_mode,
+                storage_type=self._type_name,
+                **self._kwds)
+        self.assertEqual(os.path.exists(self._dummy_name), False)
+        with self.assertRaises(ValueError):
+            PathORAM.setup(
+                self._dummy_name,
+                block_size=1,
+                block_count=1,
+                bucket_capacity=self._bucket_capacity,
+                heap_base=self._heap_base,
+                key_size=-1,
+                aes_mode=self._aes_mode,
+                storage_type=self._type_name,
+                **self._kwds)
+        self.assertEqual(os.path.exists(self._dummy_name), False)
+        with self.assertRaises(TypeError):
+            PathORAM.setup(
+                self._dummy_name,
+                block_size=1,
+                block_count=1,
+                bucket_capacity=self._bucket_capacity,
+                heap_base=self._heap_base,
+                key=-1,
+                aes_mode=self._aes_mode,
+                storage_type=self._type_name,
+                **self._kwds)
+        self.assertEqual(os.path.exists(self._dummy_name), False)
+        with self.assertRaises(ValueError):
+            PathORAM.setup(
+                self._dummy_name,
+                block_size=1,
+                block_count=1,
+                bucket_capacity=self._bucket_capacity,
+                heap_base=self._heap_base,
+                key=AES.KeyGen(AES.key_sizes[-1]),
+                key_size=AES.key_sizes[-1],
+                aes_mode=self._aes_mode,
+                storage_type=self._type_name,
+                **self._kwds)
+        self.assertEqual(os.path.exists(self._dummy_name), False)
+        with self.assertRaises(ValueError):
+            PathORAM.setup(
+                self._dummy_name,
+                block_size=1,
+                block_count=1,
+                bucket_capacity=self._bucket_capacity,
+                heap_base=self._heap_base,
+                key=os.urandom(AES.key_sizes[-1]+100),
+                aes_mode=self._aes_mode,
+                storage_type=self._type_name,
+                **self._kwds)
+        with self.assertRaises(ValueError):
+            PathORAM.setup(
+                self._dummy_name,
+                block_size=1,
+                block_count=1,
+                heap_height=1,
+                bucket_capacity=self._bucket_capacity,
+                heap_base=self._heap_base,
+                key=self._key,
+                aes_mode=self._aes_mode,
+                storage_type=self._type_name,
+                **self._kwds)
+
+    def test_setup(self):
+        fname = ".".join(self.id().split(".")[1:])
+        fname += ".bin"
+        fname = os.path.join(thisdir, fname)
+        if os.path.exists(fname):
+            os.remove(fname)                           # pragma: no cover
+        bsize = 10
+        bcount = 11
+        fsetup = PathORAM.setup(
+            fname,
+            bsize,
+            bcount,
+            bucket_capacity=self._bucket_capacity,
+            heap_base=self._heap_base,
+            key=self._test_key,
+            key_size=self._test_key_size,
+            aes_mode=self._aes_mode,
+            storage_type=self._type_name,
+            **self._kwds)
+        fsetup.close()
+        self.assertEqual(type(fsetup.raw_storage),
+                         BlockStorageTypeFactory(self._type_name))
+        # test that these can be called with default keyword values
+        fsetup.stash_digest(fsetup.stash)
+        fsetup.position_map_digest(fsetup.position_map)
+        with open(fname, 'rb') as f:
+            flen = len(f.read())
+            self.assertEqual(
+                flen,
+                PathORAM.compute_storage_size(
+                    bsize,
+                    bcount,
+                    bucket_capacity=self._bucket_capacity,
+                    heap_base=self._heap_base,
+                    aes_mode=self._aes_mode,
+                    storage_type=self._type_name))
+            self.assertEqual(
+                flen >
+                PathORAM.compute_storage_size(
+                    bsize,
+                    bcount,
+                    bucket_capacity=self._bucket_capacity,
+                    heap_base=self._heap_base,
+                    aes_mode=self._aes_mode,
+                    storage_type=self._type_name,
+                    ignore_header=True),
+                True)
+        with PathORAM(fname,
+                      fsetup.stash,
+                      fsetup.position_map,
+                      key=fsetup.key,
+                      storage_type=self._type_name,
+                      **self._kwds) as f:
+            self.assertEqual(f.header_data, bytes())
+            self.assertEqual(fsetup.header_data, bytes())
+            self.assertEqual(f.key, fsetup.key)
+            self.assertEqual(f.block_size, bsize)
+            self.assertEqual(fsetup.block_size, bsize)
+            self.assertEqual(f.block_count, bcount)
+            self.assertEqual(fsetup.block_count, bcount)
+            self.assertEqual(f.storage_name, fname)
+            self.assertEqual(fsetup.storage_name, fname)
+        os.remove(fname)
+
+    def test_setup_withdata(self):
+        fname = ".".join(self.id().split(".")[1:])
+        fname += ".bin"
+        fname = os.path.join(thisdir, fname)
+        if os.path.exists(fname):
+            os.remove(fname)                           # pragma: no cover
+        bsize = 10
+        bcount = 11
+        header_data = bytes(bytearray([0,1,2]))
+        fsetup = PathORAM.setup(
+            fname,
+            block_size=bsize,
+            block_count=bcount,
+            bucket_capacity=self._bucket_capacity,
+            heap_base=self._heap_base,
+            key=self._test_key,
+            key_size=self._test_key_size,
+            aes_mode=self._aes_mode,
+            storage_type=self._type_name,
+            header_data=header_data,
+            **self._kwds)
+        fsetup.close()
+        self.assertEqual(type(fsetup.raw_storage),
+                         BlockStorageTypeFactory(self._type_name))
+        with open(fname, 'rb') as f:
+            flen = len(f.read())
+            self.assertEqual(
+                flen,
+                PathORAM.compute_storage_size(
+                    bsize,
+                    bcount,
+                    bucket_capacity=self._bucket_capacity,
+                    heap_base=self._heap_base,
+                    aes_mode=self._aes_mode,
+                    storage_type=self._type_name,
+                    header_data=header_data))
+            self.assertTrue(len(header_data) > 0)
+            self.assertEqual(
+                PathORAM.compute_storage_size(
+                    bsize,
+                    bcount,
+                    bucket_capacity=self._bucket_capacity,
+                    heap_base=self._heap_base,
+                    aes_mode=self._aes_mode,
+                    storage_type=self._type_name) <
+                PathORAM.compute_storage_size(
+                    bsize,
+                    bcount,
+                    bucket_capacity=self._bucket_capacity,
+                    heap_base=self._heap_base,
+                    aes_mode=self._aes_mode,
+                    storage_type=self._type_name,
+                    header_data=header_data),
+                True)
+            self.assertEqual(
+                flen >
+                PathORAM.compute_storage_size(
+                    bsize,
+                    bcount,
+                    bucket_capacity=self._bucket_capacity,
+                    heap_base=self._heap_base,
+                    aes_mode=self._aes_mode,
+                    storage_type=self._type_name,
+                    header_data=header_data,
+                    ignore_header=True),
+                True)
+        with PathORAM(fname,
+                      fsetup.stash,
+                      fsetup.position_map,
+                      key=fsetup.key,
+                      storage_type=self._type_name,
+                      **self._kwds) as f:
+            self.assertEqual(f.header_data, header_data)
+            self.assertEqual(fsetup.header_data, header_data)
+            self.assertEqual(f.key, fsetup.key)
+            self.assertEqual(f.block_size, bsize)
+            self.assertEqual(fsetup.block_size, bsize)
+            self.assertEqual(f.block_count, bcount)
+            self.assertEqual(fsetup.block_count, bcount)
+            self.assertEqual(f.storage_name, fname)
+            self.assertEqual(fsetup.storage_name, fname)
+        os.remove(fname)
+
+    def test_init_noexists(self):
+        self.assertEqual(os.path.exists(self._dummy_name), False)
+        with self.assertRaises(IOError):
+            with PathORAM(
+                    self._dummy_name,
+                    self._stash,
+                    self._position_map,
+                    key=self._key,
+                    storage_type=self._type_name,
+                    **self._kwds) as f:
+                pass                                   # pragma: no cover
+
+    def test_init_exists(self):
+        self.assertEqual(os.path.exists(self._testfname), True)
+        with open(self._testfname, 'rb') as f:
+            databefore = f.read()
+        # no key
+        with self.assertRaises(ValueError):
+            with PathORAM(self._testfname,
+                          self._stash,
+                          self._position_map,
+                          storage_type=self._type_name,
+                          **self._kwds) as f:
+                pass                                   # pragma: no cover
+        # stash does not match digest
+        with self.assertRaises(ValueError):
+            with PathORAM(self._testfname,
+                          {1: bytes()},
+                          self._position_map,
+                          key=self._key,
+                          storage_type=self._type_name,
+                          **self._kwds) as f:
+                pass                                   # pragma: no cover
+        # stash hash invalid key (negative)
+        with self.assertRaises(ValueError):
+            with PathORAM(self._testfname,
+                          {-1: bytes()},
+                          self._position_map,
+                          key=self._key,
+                          storage_type=self._type_name,
+                          **self._kwds) as f:
+                pass                                   # pragma: no cover
+        # position map has invalid item (negative)
+        with self.assertRaises(ValueError):
+            with PathORAM(self._testfname,
+                          self._stash,
+                          [-1],
+                          key=self._key,
+                          storage_type=self._type_name,
+                          **self._kwds) as f:
+                pass                                   # pragma: no cover
+        # position map does not match digest
+        with self.assertRaises(ValueError):
+            with PathORAM(self._testfname,
+                          self._stash,
+                          [1],
+                          key=self._key,
+                          storage_type=self._type_name,
+                          **self._kwds) as f:
+                pass                                   # pragma: no cover
+        with self.assertRaises(ValueError):
+            with EncryptedHeapStorage(self._testfname,
+                                      key=self._key,
+                                      storage_type=self._type_name) as fb:
+                with PathORAM(fb,
+                              self._stash,
+                              self._position_map,
+                              key=self._key,
+                              storage_type=self._type_name,
+                              **self._kwds) as f:
+                    pass                               # pragma: no cover
+        with PathORAM(self._testfname,
+                      self._stash,
+                      self._position_map,
+                      key=self._key,
+                      storage_type=self._type_name,
+                      **self._kwds) as f:
+            self.assertEqual(f.key, self._key)
+            self.assertEqual(f.block_size, self._block_size)
+            self.assertEqual(f.block_count, self._block_count)
+            self.assertEqual(f.storage_name, self._testfname)
+            self.assertEqual(f.header_data, bytes())
+        self.assertEqual(os.path.exists(self._testfname), True)
+        with open(self._testfname, 'rb') as f:
+            dataafter = f.read()
+        self.assertEqual(databefore[-(self._block_count*self._block_size):],
+                         dataafter[-(self._block_count*self._block_size):])
+
+    def test_read_block(self):
+        with PathORAM(self._testfname,
+                      self._stash,
+                      self._position_map,
+                      key=self._key,
+                      storage_type=self._type_name,
+                      **self._kwds) as f:
+            for i, data in enumerate(self._blocks):
+                self.assertEqual(list(bytearray(f.read_block(i))),
+                                 list(self._blocks[i]))
+            for i, data in enumerate(self._blocks):
+                self.assertEqual(list(bytearray(f.read_block(i))),
+                                 list(self._blocks[i]))
+            for i, data in reversed(list(enumerate(self._blocks))):
+                self.assertEqual(list(bytearray(f.read_block(i))),
+                                 list(self._blocks[i]))
+            for i, data in reversed(list(enumerate(self._blocks))):
+                self.assertEqual(list(bytearray(f.read_block(i))),
+                                 list(self._blocks[i]))
+        with PathORAM(self._testfname,
+                      self._stash,
+                      self._position_map,
+                      key=self._key,
+                      storage_type=self._type_name,
+                      **self._kwds) as f:
+            self.assertEqual(list(bytearray(f.read_block(0))),
+                             list(self._blocks[0]))
+            self.assertEqual(list(bytearray(f.read_block(self._block_count-1))),
+                             list(self._blocks[-1]))
+
+        # test eviction behavior of the tree oram helper
+        with PathORAM(self._testfname,
+                      self._stash,
+                      self._position_map,
+                      key=self._key,
+                      storage_type=self._type_name,
+                      **self._kwds) as f:
+            oram = f._oram
+            vheap = oram.storage_heap.virtual_heap
+            Z = vheap.blocks_per_bucket
+            def _has_vacancies(level):
+                return any(oram.path_block_ids[i] == oram.empty_block_id
+                           for i in range(level*Z, (level+1)*Z))
+
+            for i in range(len(f.position_map)):
+                b = f.position_map[i]
+                f.position_map[i] = vheap.random_leaf_bucket()
+                oram.load_path(b)
+                block = oram.extract_block_from_path(i)
+                if block is not None:
+                    oram.stash[i] = block
+
+                # track where everyone should be able to move
+                # to, unless the bucket fills up
+                eviction_levels = {}
+                for id_, level in zip(oram.path_block_ids,
+                                      oram.path_block_eviction_levels):
+                    eviction_levels[id_] = level
+                for id_ in oram.stash:
+                    block_id, block_addr = \
+                        oram.get_block_info(oram.stash[id_])
+                    assert block_id == id_
+                    eviction_levels[id_] = \
+                        vheap.clib.calculate_last_common_level(
+                            vheap.k, b, block_addr)
+
+                oram.push_down_path()
+                oram.fill_path_from_stash()
+                oram.evict_path()
+
+                # check that everyone was pushed down greedily
+                oram.load_path(b)
+                for pos, id_ in enumerate(oram.path_block_ids):
+                    current_level = pos // Z
+                    if (id_ != oram.empty_block_id):
+                        eviction_level = eviction_levels[id_]
+                        self.assertEqual(current_level <= eviction_level, True)
+                        if current_level < eviction_level:
+                            self.assertEqual(_has_vacancies(eviction_level), False)
+                for id_ in oram.stash:
+                    self.assertEqual(
+                        _has_vacancies(eviction_levels[id_]), False)
+
+    def test_write_block(self):
+        data = bytearray([self._block_count])*self._block_size
+        self.assertEqual(len(data) > 0, True)
+        with PathORAM(self._testfname,
+                      self._stash,
+                      self._position_map,
+                      key=self._key,
+                      storage_type=self._type_name,
+                      **self._kwds) as f:
+            for i in xrange(self._block_count):
+                self.assertNotEqual(list(bytearray(f.read_block(i))),
+                                    list(data))
+            for i in xrange(self._block_count):
+                f.write_block(i, bytes(data))
+            for i in xrange(self._block_count):
+                self.assertEqual(list(bytearray(f.read_block(i))),
+                                 list(data))
+            for i, block in enumerate(self._blocks):
+                f.write_block(i, bytes(block))
+
+    def test_read_blocks(self):
+        with PathORAM(self._testfname,
+                      self._stash,
+                      self._position_map,
+                      key=self._key,
+                      storage_type=self._type_name,
+                      **self._kwds) as f:
+            data = f.read_blocks(list(xrange(self._block_count)))
+            self.assertEqual(len(data), self._block_count)
+            for i, block in enumerate(data):
+                self.assertEqual(list(bytearray(block)),
+                                 list(self._blocks[i]))
+            data = f.read_blocks([0])
+            self.assertEqual(len(data), 1)
+            self.assertEqual(list(bytearray(data[0])),
+                             list(self._blocks[0]))
+            self.assertEqual(len(self._blocks) > 1, True)
+            data = f.read_blocks(list(xrange(1, self._block_count)) + [0])
+            self.assertEqual(len(data), self._block_count)
+            for i, block in enumerate(data[:-1], 1):
+                self.assertEqual(list(bytearray(block)),
+                                 list(self._blocks[i]))
+            self.assertEqual(list(bytearray(data[-1])),
+                             list(self._blocks[0]))
+
+    def test_write_blocks(self):
+        data = [bytearray([self._block_count])*self._block_size
+                for i in xrange(self._block_count)]
+        with PathORAM(self._testfname,
+                      self._stash,
+                      self._position_map,
+                      key=self._key,
+                      storage_type=self._type_name,
+                      **self._kwds) as f:
+            orig = f.read_blocks(list(xrange(self._block_count)))
+            self.assertEqual(len(orig), self._block_count)
+            for i, block in enumerate(orig):
+                self.assertEqual(list(bytearray(block)),
+                                 list(self._blocks[i]))
+            f.write_blocks(list(xrange(self._block_count)),
+                           [bytes(b) for b in data])
+            new = f.read_blocks(list(xrange(self._block_count)))
+            self.assertEqual(len(new), self._block_count)
+            for i, block in enumerate(new):
+                self.assertEqual(list(bytearray(block)),
+                                 list(data[i]))
+            f.write_blocks(list(xrange(self._block_count)),
+                           [bytes(b) for b in self._blocks])
+            orig = f.read_blocks(list(xrange(self._block_count)))
+            self.assertEqual(len(orig), self._block_count)
+            for i, block in enumerate(orig):
+                self.assertEqual(list(bytearray(block)),
+                                 list(self._blocks[i]))
+
+    def test_update_header_data(self):
+        fname = ".".join(self.id().split(".")[1:])
+        fname += ".bin"
+        fname = os.path.join(thisdir, fname)
+        if os.path.exists(fname):
+            os.remove(fname)                           # pragma: no cover
+        bsize = 10
+        bcount = 11
+        header_data = bytes(bytearray([0,1,2]))
+        fsetup = PathORAM.setup(
+            fname,
+            block_size=bsize,
+            block_count=bcount,
+            bucket_capacity=self._bucket_capacity,
+            heap_base=self._heap_base,
+            key=self._test_key,
+            key_size=self._test_key_size,
+            header_data=header_data,
+            **self._kwds)
+        fsetup.close()
+        new_header_data = bytes(bytearray([1,1,1]))
+        with PathORAM(fname,
+                      fsetup.stash,
+                      fsetup.position_map,
+                      key=fsetup.key,
+                      storage_type=self._type_name,
+                      **self._kwds) as f:
+            self.assertEqual(f.header_data, header_data)
+            f.update_header_data(new_header_data)
+            self.assertEqual(f.header_data, new_header_data)
+        with PathORAM(fname,
+                      fsetup.stash,
+                      fsetup.position_map,
+                      key=fsetup.key,
+                      storage_type=self._type_name,
+                      **self._kwds) as f:
+            self.assertEqual(f.header_data, new_header_data)
+        with self.assertRaises(ValueError):
+            with PathORAM(fname,
+                          fsetup.stash,
+                          fsetup.position_map,
+                          key=fsetup.key,
+                          storage_type=self._type_name,
+                          **self._kwds) as f:
+                f.update_header_data(bytes(bytearray([1,1])))
+        with self.assertRaises(ValueError):
+            with PathORAM(fname,
+                          fsetup.stash,
+                          fsetup.position_map,
+                          key=fsetup.key,
+                          storage_type=self._type_name,
+                          **self._kwds) as f:
+                f.update_header_data(bytes(bytearray([1,1,1,1])))
+        with PathORAM(fname,
+                      fsetup.stash,
+                      fsetup.position_map,
+                      key=fsetup.key,
+                      storage_type=self._type_name,
+                      **self._kwds) as f:
+            self.assertEqual(f.header_data, new_header_data)
+        os.remove(fname)
+
+    def test_locked_flag(self):
+        with PathORAM(self._testfname,
+                      self._stash,
+                      self._position_map,
+                      key=self._key,
+                      storage_type=self._type_name,
+                      **self._kwds) as f:
+            with self.assertRaises(IOError):
+                with PathORAM(self._testfname,
+                              self._stash,
+                              self._position_map,
+                              key=self._key,
+                              storage_type=self._type_name,
+                              **self._kwds) as f1:
+                    pass                               # pragma: no cover
+            with self.assertRaises(IOError):
+                with PathORAM(self._testfname,
+                              self._stash,
+                              self._position_map,
+                              key=self._key,
+                              storage_type=self._type_name,
+                              **self._kwds) as f1:
+                    pass                               # pragma: no cover
+            with PathORAM(self._testfname,
+                          self._stash,
+                          self._position_map,
+                          key=self._key,
+                          storage_type=self._type_name,
+                          ignore_lock=True,
+                          **self._kwds) as f1:
+                pass
+            with self.assertRaises(IOError):
+                with PathORAM(self._testfname,
+                              self._stash,
+                              self._position_map,
+                              key=self._key,
+                              storage_type=self._type_name,
+                              **self._kwds) as f1:
+                    pass                               # pragma: no cover
+            with PathORAM(self._testfname,
+                          self._stash,
+                          self._position_map,
+                          key=self._key,
+                          storage_type=self._type_name,
+                          ignore_lock=True,
+                          **self._kwds) as f1:
+                pass
+            with PathORAM(self._testfname,
+                          self._stash,
+                          self._position_map,
+                          key=self._key,
+                          storage_type=self._type_name,
+                          ignore_lock=True,
+                          **self._kwds) as f1:
+                pass
+        with PathORAM(self._testfname,
+                      self._stash,
+                      self._position_map,
+                      key=self._key,
+                      storage_type=self._type_name,
+                      **self._kwds) as f:
+            pass
+
+class TestPathORAMB2Z1(_TestPathORAMBase,
+                       unittest2.TestCase):
+    _type_name = 'file'
+    _aes_mode = 'ctr'
+    _bucket_capacity = 1
+    _heap_base = 2
+    _kwds = {'cached_levels': 0}
+
+class TestPathORAMB2Z2(_TestPathORAMBase,
+                       unittest2.TestCase):
+    _type_name = 'mmap'
+    _aes_mode = 'gcm'
+    _bucket_capacity = 2
+    _heap_base = 2
+    _kwds = {'cached_levels': 0}
+
+class TestPathORAMB2Z3(_TestPathORAMBase,
+                       unittest2.TestCase):
+    _type_name = 'mmap'
+    _aes_mode = 'ctr'
+    _bucket_capacity = 3
+    _heap_base = 2
+    _kwds = {'cached_levels': 1}
+
+class TestPathORAMB2Z4(_TestPathORAMBase,
+                       unittest2.TestCase):
+    _type_name = 'file'
+    _aes_mode = 'gcm'
+    _bucket_capacity = 4
+    _heap_base = 2
+    _kwds = {'cached_levels': 1}
+
+class TestPathORAMB2Z5(_TestPathORAMBase,
+                       unittest2.TestCase):
+    _type_name = 'file'
+    _aes_mode = 'ctr'
+    _bucket_capacity = 5
+    _heap_base = 2
+    _kwds = {'cached_levels': 2,
+             'concurrency_level': 0}
+
+class TestPathORAMB3Z1(_TestPathORAMBase,
+                       unittest2.TestCase):
+    _type_name = 'file'
+    _aes_mode = 'ctr'
+    _bucket_capacity = 1
+    _heap_base = 3
+    _kwds = {'cached_levels': 2,
+             'concurrency_level': 1}
+
+class TestPathORAMB3Z2(_TestPathORAMBase,
+                       unittest2.TestCase):
+    _type_name = 'mmap'
+    _aes_mode = 'gcm'
+    _bucket_capacity = 2
+    _heap_base = 3
+    _kwds = {}
+
+class TestPathORAMB3Z3(_TestPathORAMBase,
+                       unittest2.TestCase):
+    _type_name = 'mmap'
+    _aes_mode = 'ctr'
+    _bucket_capacity = 3
+    _heap_base = 3
+    _kwds = {}
+
+class TestPathORAMB3Z4(_TestPathORAMBase,
+                       unittest2.TestCase):
+    _type_name = 'file'
+    _aes_mode = 'gcm'
+    _bucket_capacity = 4
+    _heap_base = 3
+    _kwds = {}
+
+class TestPathORAMB3Z5(_TestPathORAMBase,
+                       unittest2.TestCase):
+    _type_name = 'file'
+    _aes_mode = 'ctr'
+    _bucket_capacity = 5
+    _heap_base = 3
+    _kwds = {}
+
+if __name__ == "__main__":
+    unittest2.main()                                    # pragma: no cover