# HG changeset patch
# User Benjamin Peterson <benjamin@python.org>
# Date 1397441438 14400
# Node ID 50c07ed1743da9cd4540d83de0c30bd17aeb41b0
# Parent  218e28a935ab4494d05215c243e2129625a71893
in scan_once, prevent the reading of arbitrary memory when passed a negative index

Bug reported by Guido Vranken.

Index: Python-2.7.6/Lib/json/tests/test_decode.py
===================================================================
--- Python-2.7.6.orig/Lib/json/tests/test_decode.py	2014-06-26 18:40:10.825269130 +0200
+++ Python-2.7.6/Lib/json/tests/test_decode.py	2014-06-26 18:40:21.962323035 +0200
@@ -60,5 +60,10 @@
         msg = 'escape'
         self.assertRaisesRegexp(ValueError, msg, self.loads, s)
 
+    def test_negative_index(self):
+        d = self.json.JSONDecoder()
+        self.assertRaises(ValueError, d.raw_decode, 'a'*42, -50000)
+        self.assertRaises(ValueError, d.raw_decode, u'a'*42, -50000)
+
 class TestPyDecode(TestDecode, PyTest): pass
 class TestCDecode(TestDecode, CTest): pass
Index: Python-2.7.6/Misc/ACKS
===================================================================
--- Python-2.7.6.orig/Misc/ACKS	2014-06-26 18:40:10.826269135 +0200
+++ Python-2.7.6/Misc/ACKS	2014-06-26 18:40:21.962323035 +0200
@@ -1085,6 +1085,7 @@
 Frank Visser
 Johannes Vogel
 Alex Volkov
+Guido Vranken
 Martijn Vries
 Niki W. Waibel
 Wojtek Walczak
Index: Python-2.7.6/Modules/_json.c
===================================================================
--- Python-2.7.6.orig/Modules/_json.c	2014-06-26 18:40:10.828269145 +0200
+++ Python-2.7.6/Modules/_json.c	2014-06-26 18:40:21.965323049 +0200
@@ -1491,7 +1491,10 @@
     PyObject *res;
     char *str = PyString_AS_STRING(pystr);
     Py_ssize_t length = PyString_GET_SIZE(pystr);
-    if (idx >= length) {
+    if (idx < 0)
+        /* Compatibility with the Python version. */
+        idx += length;
+    if (idx < 0 || idx >= length) {
         PyErr_SetNone(PyExc_StopIteration);
         return NULL;
     }
@@ -1578,7 +1581,10 @@
     PyObject *res;
     Py_UNICODE *str = PyUnicode_AS_UNICODE(pystr);
     Py_ssize_t length = PyUnicode_GET_SIZE(pystr);
-    if (idx >= length) {
+    if (idx < 0)
+        /* Compatibility with Python version. */
+        idx += length;
+    if (idx < 0 || idx >= length) {
         PyErr_SetNone(PyExc_StopIteration);
         return NULL;
     }