bpo-30431: Raise ValueError in case of null in input prompt

If the input prompt to the builtin input function has any null
character, then raise ValueError.

Author: kushaldas

Lib/test/test_readline.py

@@ -127,6 +127,13 @@ def test_init(self):
 input()
 print("History length:", readline.get_current_history_length())
 """
+    auto_history_script_with_null = """\
+import readline
+readline.set_auto_history({})
+input("Hello \\x00 World: ")
+print("History length:", readline.get_current_history_length())
+"""
+
 
     def test_auto_history_enabled(self):
         output = run_pty(self.auto_history_script.format(True))
@@ -136,6 +143,10 @@ def test_auto_history_disabled(self):
         output = run_pty(self.auto_history_script.format(False))
         self.assertIn(b"History length: 0\r\n", output)
 
+    def test_prompt_contains_null(self):
+        output = run_pty(self.auto_history_script_with_null.format(False))
+        self.assertIn(b"ValueError: input: prompt string cannot contain null characters", output)
+
     def test_nonascii(self):
         try:
             readline.add_history("\xEB\xEF")

Python/bltinmodule.c

@@ -1974,6 +1974,11 @@ builtin_input_impl(PyObject *module, PyObject *prompt)
                 goto _readline_errors;
             assert(PyBytes_Check(po));
             promptstr = PyBytes_AS_STRING(po);
+            if ((Py_ssize_t)strlen(promptstr) != PyBytes_GET_SIZE(po)) {
+                    PyErr_SetString(PyExc_ValueError,
+                                    "input: prompt string cannot contain null characters");
+                    goto _readline_errors;
+            }
         }
         else {
             po = NULL;