[4.2.x] Fixed CVE-2024-56374 -- Mitigated potential DoS in IPv6 validation.

Thanks Saravana Kumar for the report, and Sarah Boyce and Mariusz
Felisiak for the reviews.

Co-authored-by: Natalia <124304+nessita@users.noreply.github.com>

1 files changed, 32 insertions, 1 deletions

diff --git a/tests/forms_tests/field_tests/test_genericipaddressfield.py b/tests/forms_tests/field_tests/test_genericipaddressfield.py
index 80722f5c65..ef00a727a4 100644
--- a/tests/forms_tests/field_tests/test_genericipaddressfield.py
+++ b/tests/forms_tests/field_tests/test_genericipaddressfield.py
@@ -1,6 +1,7 @@
 from django.core.exceptions import ValidationError
 from django.forms import GenericIPAddressField
 from django.test import SimpleTestCase
+from django.utils.ipv6 import MAX_IPV6_ADDRESS_LENGTH
 
 
 class GenericIPAddressFieldTest(SimpleTestCase):
@@ -125,6 +126,35 @@ class GenericIPAddressFieldTest(SimpleTestCase):
         ):
             f.clean("1:2")
 
+    def test_generic_ipaddress_max_length_custom(self):
+        # Valid IPv4-mapped IPv6 address, len 45.
+        addr = "0000:0000:0000:0000:0000:ffff:192.168.100.228"
+        f = GenericIPAddressField(max_length=len(addr))
+        f.clean(addr)
+
+    def test_generic_ipaddress_max_length_validation_error(self):
+        # Valid IPv4-mapped IPv6 address, len 45.
+        addr = "0000:0000:0000:0000:0000:ffff:192.168.100.228"
+
+        cases = [
+            ({}, MAX_IPV6_ADDRESS_LENGTH),  # Default value.
+            ({"max_length": len(addr) - 1}, len(addr) - 1),
+        ]
+        for kwargs, max_length in cases:
+            max_length_plus_one = max_length + 1
+            msg = (
+                f"Ensure this value has at most {max_length} characters (it has "
+                f"{max_length_plus_one}).'"
+            )
+            with self.subTest(max_length=max_length):
+                f = GenericIPAddressField(**kwargs)
+                with self.assertRaisesMessage(ValidationError, msg):
+                    f.clean("x" * max_length_plus_one)
+                with self.assertRaisesMessage(
+                    ValidationError, "This is not a valid IPv6 address."
+                ):
+                    f.clean(addr)
+
     def test_generic_ipaddress_as_generic_not_required(self):
         f = GenericIPAddressField(required=False)
         self.assertEqual(f.clean(""), "")
@@ -150,7 +180,8 @@ class GenericIPAddressFieldTest(SimpleTestCase):
             f.clean(" fe80::223:6cff:fe8a:2e8a "), "fe80::223:6cff:fe8a:2e8a"
         )
         self.assertEqual(
-            f.clean(" 2a02::223:6cff:fe8a:2e8a "), "2a02::223:6cff:fe8a:2e8a"
+            f.clean(" " * MAX_IPV6_ADDRESS_LENGTH + " 2a02::223:6cff:fe8a:2e8a "),
+            "2a02::223:6cff:fe8a:2e8a",
         )
         with self.assertRaisesMessage(
             ValidationError, "'This is not a valid IPv6 address.'"