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[3.8] bpo-41004: Resolve hash collisions for IPv4Interface and IPv6Interface (GH-21033) #21221

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Merged
miss-islington merged 1 commit into from
Jun 29, 2020
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[3.8] bpo-41004: Resolve hash collisions for IPv4Interface and IPv6Interface (GH-21033) #21221

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bpo-41004: Resolve hash collisions for IPv4Interface and IPv6Interface ( 
GH-21033)

The __hash__() methods of classes IPv4Interface and IPv6Interface had issue
of generating constant hash values of 32 and 128 respectively causing hash collisions.
The fix uses the hash() function to generate hash values for the objects
instead of XOR operation
(cherry picked from commit b30ee26)

Co-authored-by: Ravi Teja P <rvteja92@gmail.com>
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@rvteja92 @miss-islington
rvteja92 authored and miss-islington committed Jun 29, 2020
commit bd32b1fc950e6633d237855ceddd84ea83904238
4 changes: 2 additions & 2 deletions Lib/ipaddress.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1370,7 +1370,7 @@ def __lt__(self, other):
return False

def __hash__(self):
return self._ip ^ self._prefixlen ^ int(self.network.network_address)
return hash((self._ip, self._prefixlen, int(self.network.network_address)))

__reduce__ = _IPAddressBase.__reduce__

Expand Down Expand Up @@ -2017,7 +2017,7 @@ def __lt__(self, other):
return False

def __hash__(self):
return self._ip ^ self._prefixlen ^ int(self.network.network_address)
return hash((self._ip, self._prefixlen, int(self.network.network_address)))

__reduce__ = _IPAddressBase.__reduce__

Expand Down
12 changes: 12 additions & 0 deletions Lib/test/test_ipaddress.py
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Original file line number Diff line number Diff line change
Expand Up @@ -2053,6 +2053,18 @@ def testsixtofour(self):
sixtofouraddr.sixtofour)
self.assertFalse(bad_addr.sixtofour)

# issue41004 Hash collisions in IPv4Interface and IPv6Interface
def testV4HashIsNotConstant(self):
ipv4_address1 = ipaddress.IPv4Interface("1.2.3.4")
ipv4_address2 = ipaddress.IPv4Interface("2.3.4.5")
self.assertNotEqual(ipv4_address1.__hash__(), ipv4_address2.__hash__())

# issue41004 Hash collisions in IPv4Interface and IPv6Interface
def testV6HashIsNotConstant(self):
ipv6_address1 = ipaddress.IPv6Interface("2001:658:22a:cafe:200:0:0:1")
ipv6_address2 = ipaddress.IPv6Interface("2001:658:22a:cafe:200:0:0:2")
self.assertNotEqual(ipv6_address1.__hash__(), ipv6_address2.__hash__())


if __name__ == '__main__':
unittest.main()
1 change: 1 addition & 0 deletions Misc/NEWS.d/next/Security/2020-06-29-16-02-29.bpo-41004.ovF0KZ.rst
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@@ -0,0 +1 @@
The __hash__() methods of ipaddress.IPv4Interface and ipaddress.IPv6Interface incorrectly generated constant hash values of 32 and 128 respectively. This resulted in always causing hash collisions. The fix uses hash() to generate hash values for the tuple of (address, mask length, network address).