fix: overflow in malformed interval

NEWS

@@ -1,3 +1,12 @@
+Future releases
+---------------
+
+What's new in psycopg 2.9.12 (unreleased)
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+- Fix infinite loop with malformed interval (:ticket:`1835`).
+
+
 Current release
 ---------------
 

psycopg/typecast_datetime.c

@@ -358,7 +358,12 @@ typecast_PYINTERVAL_cast(const char *str, Py_ssize_t len, PyObject *curs)
                 v = v1;
             }
             if (part == 6) {
-                denom *= 10;
+                /* if denom would overflow it means that an excess of decimal
+                 * digits is being pushed. Postgres should never send more than
+                 * 6. Therefore we can quietly discard the extra. */
+                if (denom <= INT_MAX / 10) {
+                    denom *= 10;
+                }
             }
             break;
 

tests/test_dates.py

@@ -479,6 +479,12 @@ def test_interval_iso_8601_not_supported(self):
         cur.execute("select '1 day 2 hours'::interval")
         self.assertRaises(psycopg2.NotSupportedError, cur.fetchone)
 
+    def test_bug_1835(self):
+        for digits in (8, 31, 100):
+            self.assertEqual(
+                psycopg2.extensions.INTERVAL(b"0:0:0." + b"0" * digits, None),
+                timedelta(0))
+
 
 class FromTicksTestCase(unittest.TestCase):
     # bug "TimestampFromTicks() throws ValueError (2-2.0.14)"