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[2.7] bpo-31478: Prevent unwanted behavior in _random.Random.seed() in case the arg has a bad __abs__() method (GH-3596) #3845

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Merged
merged 5 commits into from
Oct 2, 2017
Merged

[2.7] bpo-31478: Prevent unwanted behavior in _random.Random.seed() in case the arg has a bad __abs__() method (GH-3596) #3845

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e15c28c
init commit
orenmn Oct 1, 2017
f5300db
move the comment
orenmn Oct 1, 2017
eb8ea90
simplify the test
orenmn Oct 1, 2017
e9d75c6
remove blank line
orenmn Oct 1, 2017
27f9260
add a NEWS.d item, and make a little fix to the test
orenmn Oct 1, 2017
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16 changes: 16 additions & 0 deletions Lib/test/test_random.py
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Original file line number Diff line number Diff line change
Expand Up @@ -307,6 +307,22 @@ def test_randbelow_logic(self, _log=log, int=int):
class MersenneTwister_TestBasicOps(TestBasicOps):
gen = random.Random()

@test_support.cpython_only
def test_bug_31478(self):
# _random.Random.seed() should ignore the __abs__() method of a
# long/int subclass argument.
class BadInt(int):
def __abs__(self):
1/0
class BadLong(long):
def __abs__(self):
1/0
self.gen.seed(42)
expected_value = self.gen.random()
for seed_arg in [42L, BadInt(42), BadLong(42)]:
self.gen.seed(seed_arg)
self.assertEqual(expected_value, self.gen.random())
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Use the actual value at left and the expected value at right.


def test_setstate_first_arg(self):
self.assertRaises(ValueError, self.gen.setstate, (1, None, None))

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10 changes: 8 additions & 2 deletions Modules/_randommodule.c
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Expand Up @@ -230,9 +230,15 @@ random_seed(RandomObject *self, PyObject *args)
}
/* If the arg is an int or long, use its absolute value; else use
* the absolute value of its hash code.
* Calling int.__abs__() or long.__abs__() prevents calling arg.__abs__(),
* which might return an invalid value. See issue #31478.
*/
if (PyInt_Check(arg) || PyLong_Check(arg))
n = PyNumber_Absolute(arg);
if (PyInt_Check(arg)) {
n = PyInt_Type.tp_as_number->nb_absolute(arg);
}
else if (PyLong_Check(arg)) {
n = PyLong_Type.tp_as_number->nb_absolute(arg);
}
else {
long hash = PyObject_Hash(arg);
if (hash == -1)
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