From: Miss Islington (bot) <31488909+miss-islington@users.noreply.github.com>
Date: Mon, 29 Jun 2020 18:12:50 +0000 (-0700)
Subject: bpo-41004: Resolve hash collisions for IPv4Interface and IPv6Interface (GH-21033)
X-Git-Tag: v3.8.4rc1~1
X-Git-Url: http://git.ipfire.org/gitweb.cgi?a=commitdiff_plain;h=dc8ce8ead182de46584cc1ed8a8c51d48240cbd5;p=thirdparty%2FPython%2Fcpython.git

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 b30ee26e366bf509b7538d79bfec6c6d38d53f28)

Co-authored-by: Ravi Teja P <rvteja92@gmail.com>
---

diff --git a/Lib/ipaddress.py b/Lib/ipaddress.py
index 873c7644081a..a3a04f7f4b30 100644
--- a/Lib/ipaddress.py
+++ b/Lib/ipaddress.py
@@ -1370,7 +1370,7 @@ class IPv4Interface(IPv4Address):
             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__
 
@@ -2017,7 +2017,7 @@ class IPv6Interface(IPv6Address):
             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__
 
diff --git a/Lib/test/test_ipaddress.py b/Lib/test/test_ipaddress.py
index de77111705b6..2eba740e5e7a 100644
--- a/Lib/test/test_ipaddress.py
+++ b/Lib/test/test_ipaddress.py
@@ -2053,6 +2053,18 @@ class IpaddrUnitTest(unittest.TestCase):
                          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()
diff --git a/Misc/NEWS.d/next/Security/2020-06-29-16-02-29.bpo-41004.ovF0KZ.rst b/Misc/NEWS.d/next/Security/2020-06-29-16-02-29.bpo-41004.ovF0KZ.rst
new file mode 100644
index 000000000000..1380b31fbe9f
--- /dev/null
+++ b/Misc/NEWS.d/next/Security/2020-06-29-16-02-29.bpo-41004.ovF0KZ.rst
@@ -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).