Issue #13703: add a way to randomize the hash values of basic types (str, bytes, datetime)

in order to make algorithmic complexity attacks on (e.g.) web apps much more complicated.

The environment variable PYTHONHASHSEED and the new command line flag -R control this
behavior.

10 files changed, 180 insertions, 20 deletions

diff --git a/Lib/test/mapping_tests.py b/Lib/test/mapping_tests.py
index c34bd59..592a78b 100644
--- a/Lib/test/mapping_tests.py
+++ b/Lib/test/mapping_tests.py
@@ -14,7 +14,7 @@ class BasicTestMappingProtocol(unittest.TestCase):
     def _reference(self):
         """Return a dictionary of values which are invariant by storage
         in the object under test."""
-        return {1:2, "key1":"value1", "key2":(1,2,3)}
+        return {"1": "2", "key1":"value1", "key2":(1,2,3)}
     def _empty_mapping(self):
         """Return an empty mapping object"""
         return self.type2test()
diff --git a/Lib/test/regrtest.py b/Lib/test/regrtest.py
index 98d68bd..d203600 100755
--- a/Lib/test/regrtest.py
+++ b/Lib/test/regrtest.py
@@ -428,6 +428,11 @@ def main(tests=None, testdir=None, verbose=0, quiet=False, generate=False,
         except ValueError:
             print("Couldn't find starting test (%s), using all tests" % start)
     if randomize:
+        hashseed = os.getenv('PYTHONHASHSEED')
+        if not hashseed:
+            os.environ['PYTHONHASHSEED'] = str(random_seed)
+            os.execv(sys.executable, [sys.executable] + sys.argv)
+            return
         random.seed(random_seed)
         print("Using random seed", random_seed)
         random.shuffle(tests)
diff --git a/Lib/test/script_helper.py b/Lib/test/script_helper.py
index 0699cf6..fca28d3 100644
--- a/Lib/test/script_helper.py
+++ b/Lib/test/script_helper.py
@@ -3,7 +3,6 @@
 
 import sys
 import os
-import re
 import os.path
 import tempfile
 import subprocess
@@ -19,11 +18,15 @@ def _assert_python(expected_success, *args, **env_vars):
     cmd_line = [sys.executable]
     if not env_vars:
         cmd_line.append('-E')
-    cmd_line.extend(args)
     # Need to preserve the original environment, for in-place testing of
     # shared library builds.
     env = os.environ.copy()
+    # But a special flag that can be set to override -- in this case, the
+    # caller is responsible to pass the full environment.
+    if env_vars.pop('__cleanenv', None):
+        env = {}
     env.update(env_vars)
+    cmd_line.extend(args)
     p = subprocess.Popen(cmd_line, stdin=subprocess.PIPE,
                          stdout=subprocess.PIPE, stderr=subprocess.PIPE,
                          env=env)
diff --git a/Lib/test/test_cmd_line.py b/Lib/test/test_cmd_line.py
index c4b8be5..eacd7a6 100644
--- a/Lib/test/test_cmd_line.py
+++ b/Lib/test/test_cmd_line.py
@@ -4,7 +4,6 @@
 
 import os
 import test.support, unittest
-import os
 import sys
 import subprocess
 
@@ -190,6 +189,22 @@ sys.stdout.buffer.write(path)"""
             self.assertTrue(path1.encode('ascii') in stdout)
             self.assertTrue(path2.encode('ascii') in stdout)
 
+    def test_hash_randomization(self):
+        # Verify that -R enables hash randomization:
+        self.verify_valid_flag('-R')
+        hashes = []
+        for i in range(2):
+            code = 'print(hash("spam"))'
+            data, rc = self.start_python_and_exit_code('-R', '-c', code)
+            self.assertEqual(rc, 0)
+            hashes.append(data)
+        self.assertNotEqual(hashes[0], hashes[1])
+
+        # Verify that sys.flags contains hash_randomization
+        code = 'import sys; print("random is", sys.flags.hash_randomization)'
+        data, rc = self.start_python_and_exit_code('-R', '-c', code)
+        self.assertEqual(rc, 0)
+        self.assertIn(b'random is 1', data)
 
 def test_main():
     test.support.run_unittest(CmdLineTest)
diff --git a/Lib/test/test_descr.py b/Lib/test/test_descr.py
index 0ce85f0..077f5da 100644
--- a/Lib/test/test_descr.py
+++ b/Lib/test/test_descr.py
@@ -4300,8 +4300,18 @@ class DictProxyTests(unittest.TestCase):
 
     def test_repr(self):
         # Testing dict_proxy.__repr__
+        def sorted_dict_repr(repr_):
+            # Given the repr of a dict, sort the keys
+            assert repr_.startswith('{')
+            assert repr_.endswith('}')
+            kvs = repr_[1:-1].split(', ')
+            return '{' + ', '.join(sorted(kvs)) + '}'
         dict_ = {k: v for k, v in self.C.__dict__.items()}
-        self.assertEqual(repr(self.C.__dict__), 'dict_proxy({!r})'.format(dict_))
+        repr_ = repr(self.C.__dict__)
+        self.assert_(repr_.startswith('dict_proxy('))
+        self.assert_(repr_.endswith(')'))
+        self.assertEqual(sorted_dict_repr(repr_[len('dict_proxy('):-len(')')]),
+                         sorted_dict_repr('{!r}'.format(dict_)))
 
 
 class PTypesLongInitTest(unittest.TestCase):
diff --git a/Lib/test/test_hash.py b/Lib/test/test_hash.py
index 569e5e0..f5736b2 100644
--- a/Lib/test/test_hash.py
+++ b/Lib/test/test_hash.py
@@ -3,10 +3,16 @@
 #
 # Also test that hash implementations are inherited as expected
 
+import datetime
+import os
+import struct
 import unittest
 from test import support
+from test.script_helper import assert_python_ok
 from collections import Hashable
 
+IS_64BIT = (struct.calcsize('l') == 8)
+
 
 class HashEqualityTestCase(unittest.TestCase):
 
@@ -118,10 +124,92 @@ class HashBuiltinsTestCase(unittest.TestCase):
         for obj in self.hashes_to_check:
             self.assertEqual(hash(obj), _default_hash(obj))
 
+class HashRandomizationTests(unittest.TestCase):
+
+    # Each subclass should define a field "repr_", containing the repr() of
+    # an object to be tested
+
+    def get_hash_command(self, repr_):
+        return 'print(hash(%s))' % repr_
+
+    def get_hash(self, repr_, seed=None):
+        env = os.environ.copy()
+        env['__cleanenv'] = True  # signal to assert_python not to do a copy
+                                  # of os.environ on its own
+        if seed is not None:
+            env['PYTHONHASHSEED'] = str(seed)
+        else:
+            env.pop('PYTHONHASHSEED', None)
+        out = assert_python_ok(
+            '-c', self.get_hash_command(repr_),
+            **env)
+        stdout = out[1].strip()
+        return int(stdout)
+
+    def test_randomized_hash(self):
+        # two runs should return different hashes
+        run1 = self.get_hash(self.repr_, seed='random')
+        run2 = self.get_hash(self.repr_, seed='random')
+        self.assertNotEqual(run1, run2)
+
+class StringlikeHashRandomizationTests(HashRandomizationTests):
+    def test_null_hash(self):
+        # PYTHONHASHSEED=0 disables the randomized hash
+        if IS_64BIT:
+            known_hash_of_obj = 1453079729188098211
+        else:
+            known_hash_of_obj = -1600925533
+
+        # Randomization is disabled by default:
+        self.assertEqual(self.get_hash(self.repr_), known_hash_of_obj)
+
+        # It can also be disabled by setting the seed to 0:
+        self.assertEqual(self.get_hash(self.repr_, seed=0), known_hash_of_obj)
+
+    def test_fixed_hash(self):
+        # test a fixed seed for the randomized hash
+        # Note that all types share the same values:
+        if IS_64BIT:
+            h = -4410911502303878509
+        else:
+            h = -206076799
+        self.assertEqual(self.get_hash(self.repr_, seed=42), h)
+
+class StrHashRandomizationTests(StringlikeHashRandomizationTests):
+    repr_ = repr('abc')
+
+    def test_empty_string(self):
+        self.assertEqual(hash(""), 0)
+
+class BytesHashRandomizationTests(StringlikeHashRandomizationTests):
+    repr_ = repr(b'abc')
+
+    def test_empty_string(self):
+        self.assertEqual(hash(b""), 0)
+
+class DatetimeTests(HashRandomizationTests):
+    def get_hash_command(self, repr_):
+        return 'import datetime; print(hash(%s))' % repr_
+
+class DatetimeDateTests(DatetimeTests):
+    repr_ = repr(datetime.date(1066, 10, 14))
+
+class DatetimeDatetimeTests(DatetimeTests):
+    repr_ = repr(datetime.datetime(1, 2, 3, 4, 5, 6, 7))
+
+class DatetimeTimeTests(DatetimeTests):
+    repr_ = repr(datetime.time(0))
+
+
 def test_main():
     support.run_unittest(HashEqualityTestCase,
-                              HashInheritanceTestCase,
-                              HashBuiltinsTestCase)
+                         HashInheritanceTestCase,
+                         HashBuiltinsTestCase,
+                         StrHashRandomizationTests,
+                         BytesHashRandomizationTests,
+                         DatetimeDateTests,
+                         DatetimeDatetimeTests,
+                         DatetimeTimeTests)
 
 
 if __name__ == "__main__":
diff --git a/Lib/test/test_os.py b/Lib/test/test_os.py
index cbf0c16..bff4f0b 100644
--- a/Lib/test/test_os.py
+++ b/Lib/test/test_os.py
@@ -9,6 +9,7 @@ import warnings
 import sys
 import shutil
 from test import support
+from test.script_helper import assert_python_ok
 
 # Detect whether we're on a Linux system that uses the (now outdated
 # and unmaintained) linuxthreads threading library.  There's an issue
@@ -574,14 +575,33 @@ class DevNullTests(unittest.TestCase):
         f.close()
 
 class URandomTests(unittest.TestCase):
-    def test_urandom(self):
-        try:
-            self.assertEqual(len(os.urandom(1)), 1)
-            self.assertEqual(len(os.urandom(10)), 10)
-            self.assertEqual(len(os.urandom(100)), 100)
-            self.assertEqual(len(os.urandom(1000)), 1000)
-        except NotImplementedError:
-            pass
+    def test_urandom_length(self):
+        self.assertEqual(len(os.urandom(0)), 0)
+        self.assertEqual(len(os.urandom(1)), 1)
+        self.assertEqual(len(os.urandom(10)), 10)
+        self.assertEqual(len(os.urandom(100)), 100)
+        self.assertEqual(len(os.urandom(1000)), 1000)
+
+    def test_urandom_value(self):
+        data1 = os.urandom(16)
+        data2 = os.urandom(16)
+        self.assertNotEqual(data1, data2)
+
+    def get_urandom_subprocess(self, count):
+        code = '\n'.join((
+            'import os, sys',
+            'data = os.urandom(%s)' % count,
+            'sys.stdout.buffer.write(data)',
+            'sys.stdout.buffer.flush()'))
+        out = assert_python_ok('-c', code)
+        stdout = out[1]
+        self.assertEqual(len(stdout), 16)
+        return stdout
+
+    def test_urandom_subprocess(self):
+        data1 = self.get_urandom_subprocess(16)
+        data2 = self.get_urandom_subprocess(16)
+        self.assertNotEqual(data1, data2)
 
 class ExecTests(unittest.TestCase):
     @unittest.skipIf(USING_LINUXTHREADS,
diff --git a/Lib/test/test_set.py b/Lib/test/test_set.py
index 99d5c70..5d5e232 100644
--- a/Lib/test/test_set.py
+++ b/Lib/test/test_set.py
@@ -734,6 +734,17 @@ class TestBasicOps(unittest.TestCase):
         if self.repr is not None:
             self.assertEqual(repr(self.set), self.repr)
 
+    def check_repr_against_values(self):
+        text = repr(self.set)
+        self.assertTrue(text.startswith('{'))
+        self.assertTrue(text.endswith('}'))
+
+        result = text[1:-1].split(', ')
+        result.sort()
+        sorted_repr_values = [repr(value) for value in self.values]
+        sorted_repr_values.sort()
+        self.assertEqual(result, sorted_repr_values)
+
     def test_print(self):
         try:
             fo = open(support.TESTFN, "w")
@@ -892,7 +903,9 @@ class TestBasicOpsString(TestBasicOps):
         self.set    = set(self.values)
         self.dup    = set(self.values)
         self.length = 3
-        self.repr   = "{'a', 'c', 'b'}"
+
+    def test_repr(self):
+        self.check_repr_against_values()
 
 #------------------------------------------------------------------------------
 
@@ -903,7 +916,9 @@ class TestBasicOpsBytes(TestBasicOps):
         self.set    = set(self.values)
         self.dup    = set(self.values)
         self.length = 3
-        self.repr   = "{b'a', b'c', b'b'}"
+
+    def test_repr(self):
+        self.check_repr_against_values()
 
 #------------------------------------------------------------------------------
 
@@ -916,11 +931,13 @@ class TestBasicOpsMixedStringBytes(TestBasicOps):
         self.set    = set(self.values)
         self.dup    = set(self.values)
         self.length = 4
-        self.repr   = "{'a', b'a', 'b', b'b'}"
 
     def tearDown(self):
         warnings.filters = self.warning_filters
 
+    def test_repr(self):
+        self.check_repr_against_values()
+
 #==============================================================================
 
 def baditer():
diff --git a/Lib/test/test_sys.py b/Lib/test/test_sys.py
index 11685a4..7732c4c 100644
--- a/Lib/test/test_sys.py
+++ b/Lib/test/test_sys.py
@@ -446,7 +446,7 @@ class SysModuleTest(unittest.TestCase):
         attrs = ("debug", "division_warning",
                  "inspect", "interactive", "optimize", "dont_write_bytecode",
                  "no_user_site", "no_site", "ignore_environment", "verbose",
-                 "bytes_warning")
+                 "bytes_warning", "hash_randomization")
         for attr in attrs:
             self.assertTrue(hasattr(sys.flags, attr), attr)
             self.assertEqual(type(getattr(sys.flags, attr)), int, attr)
diff --git a/Lib/test/test_urllib.py b/Lib/test/test_urllib.py
index 4d3509a..482acc1 100644
--- a/Lib/test/test_urllib.py
+++ b/Lib/test/test_urllib.py
@@ -12,6 +12,7 @@ import os
 import sys
 import tempfile
 import warnings
+import collections
 
 def hexescape(char):
     """Escape char as RFC 2396 specifies"""
@@ -840,8 +841,9 @@ class urlencode_Tests(unittest.TestCase):
         self.assertEqual("a=1&a=2", urllib.parse.urlencode({"a": [1, 2]}, True))
         self.assertEqual("a=None&a=a",
                          urllib.parse.urlencode({"a": [None, "a"]}, True))
+        data = collections.OrderedDict([("a", 1), ("b", 1)])
         self.assertEqual("a=a&a=b",
-                         urllib.parse.urlencode({"a": {"a": 1, "b": 1}}, True))
+                         urllib.parse.urlencode({"a": data}, True))
 
     def test_urlencode_encoding(self):
         # ASCII encoding. Expect %3F with errors="replace'