bpo-31505: Fix an assertion failure in json, in case _json.make_encoder() received a bad encoder() argument.

Original patch by Oren Milman.

2 files changed, 44 insertions, 3 deletions

diff --git a/simplejson/_speedups.c b/simplejson/_speedups.c
index 7b46d8a..60f15e1 100644
--- a/simplejson/_speedups.c
+++ b/simplejson/_speedups.c
@@ -2807,10 +2807,25 @@ static PyObject *
 encoder_encode_string(PyEncoderObject *s, PyObject *obj)
 {
     /* Return the JSON representation of a string */
-    if (s->fast_encode)
+    PyObject *encoded;
+
+    if (s->fast_encode) {
         return py_encode_basestring_ascii(NULL, obj);
-    else
-        return PyObject_CallFunctionObjArgs(s->encoder, obj, NULL);
+    }
+    encoded = PyObject_CallFunctionObjArgs(s->encoder, obj, NULL);
+    if (encoded != NULL &&
+#if PY_MAJOR_VERSION < 3
+        !JSON_ASCII_Check(unicode) &&
+#endif /* PY_MAJOR_VERSION < 3 */
+        !PyUnicode_Check(encoded))
+    {
+        PyErr_Format(PyExc_TypeError,
+                     "encoder() must return a string, not %.80s",
+                     Py_TYPE(encoded)->tp_name);
+        Py_DECREF(encoded);
+        return NULL;
+    }
+    return encoded;
 }
 
 static int
diff --git a/simplejson/tests/test_speedups.py b/simplejson/tests/test_speedups.py
index b59eeca..75242fd 100644
--- a/simplejson/tests/test_speedups.py
+++ b/simplejson/tests/test_speedups.py
@@ -60,6 +60,32 @@ class TestEncode(TestCase):
         )
 
     @skip_if_speedups_missing
+    def test_bad_str_encoder(self):
+        # Issue #31505: There shouldn't be an assertion failure in case
+        # c_make_encoder() receives a bad encoder() argument.
+        def bad_encoder1(*args):
+            return None
+        enc = encoder.c_make_encoder(
+                None, lambda obj: str(obj),
+                bad_encoder1, None, ': ', ', ',
+                False, False, False, {}, False, False, False,
+                None, None, 'utf-8', False, False, decimal.Decimal, False)
+        self.assertRaises(TypeError, enc, 'spam', 4)
+        self.assertRaises(TypeError, enc, {'spam': 42}, 4)
+
+        def bad_encoder2(*args):
+            1/0
+        enc = encoder.c_make_encoder(
+                None, lambda obj: str(obj),
+                bad_encoder2, None, ': ', ', ',
+                False, False, False, {}, False, False, False,
+                None, None, 'utf-8', False, False, decimal.Decimal, False)
+        enc = self.json.encoder.c_make_encoder(None, lambda obj: str(obj),
+                                               bad_encoder2, None, ': ', ', ',
+                                               False, False, False)
+        self.assertRaises(ZeroDivisionError, enc, 'spam', 4)
+
+    @skip_if_speedups_missing
     def test_bad_bool_args(self):
         def test(name):
             encoder.JSONEncoder(**{name: BadBool()}).encode({})