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https://github.com/retspen/webvirtcloud
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09fbabf705
The expression that checks a storage pool's target directory nested a repetition inside another, so a crafted target backtracked exponentially: "," followed by 22 dashes and "!" took 1.3 s, and every two more characters four times as long. The field allows 100 characters, so one form post could hold a worker for good (CodeQL py/redos; the page is for superusers). The new expression has no nested repetition and accepts exactly the same targets: compared with the old one on 200,000 random strings over letters, digits, "/", ".", "-", "_", ",", "!", space and newline, they agree on every string. A crafted 100-character target is now checked in microseconds. The tests pin the accepted and refused targets and time the crafted one.
33 lines
1.1 KiB
Python
33 lines
1.1 KiB
Python
"""The storage pool target check runs in linear time and accepts what it did."""
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import time
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from django.test import SimpleTestCase
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from storages.forms import AddStgPool
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def target_error(target):
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form = AddStgPool({"name": "pool1", "stg_type": "dir", "target": target})
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form.is_valid()
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return "target" in form.errors
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class PoolTargetTests(SimpleTestCase):
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def test_accepted_and_refused_targets(self):
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for target, refused in (
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("/var/lib/libvirt/images", False),
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("/srv/iso-pool", False),
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("/a//b", False),
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("a-b.c_d/e", False),
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("/a/-b", True), # a dash right after a slash
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("-x", True),
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("/a b", True),
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):
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with self.subTest(target=target):
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self.assertEqual(target_error(target), refused)
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def test_a_crafted_target_is_checked_at_once(self):
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# the previous expression backtracked exponentially: 22 dashes took over a second
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start = time.monotonic()
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self.assertTrue(target_error("," + "-" * 98 + "!"))
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self.assertLess(time.monotonic() - start, 1)
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