Grow the allocated buffer in PyUnicode_EncodeUTF7 to avoid buffer overrun.

Without this change, test_unicode.UnicodeTest.test_codecs_utf7 crashes in
debug mode. What happens is the unicode string u'\U000abcde' with a length
of 1 encodes to the string '+2m/c3g-' of length 8. Since only 5 bytes is
reserved in the buffer, a buffer overrun occurs.

diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index c42cd0c6b33476a79380a4d36fb74268ccadad19..0b23e71f3d5c5c1147f0dcaf0cf25960e1453d6d 100644 (file)
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -1752,7 +1752,7 @@ PyObject *PyUnicode_EncodeUTF7(const Py_UNICODE *s,
 {
     PyObject *v;
     /* It might be possible to tighten this worst case */
-    Py_ssize_t allocated = 5 * size;
+    Py_ssize_t allocated = 8 * size;
     int inShift = 0;
     Py_ssize_t i = 0;
     unsigned int base64bits = 0;
@@ -1760,7 +1760,7 @@ PyObject *PyUnicode_EncodeUTF7(const Py_UNICODE *s,
     char * out;
     char * start;
 
-    if (allocated / 5 != size)
+    if (allocated / 8 != size)
         return PyErr_NoMemory();
 
     if (size == 0)