New submission from John Leitch:
Python 3.5.2 suffers from a type confusion vulnerability in the
chain.__setstate__ method of the itertools module. The issue exists due to lack
of argument validation in the chain_setstate() function:
static PyObject *
chain_setstate(chainobject *lz, PyObject *state)
{
PyObject *source, *active=NULL;
if (! PyArg_ParseTuple(state, "O|O", &source, &active))
return NULL;
Py_INCREF(source);
Py_XSETREF(lz->source, source);
Py_XINCREF(active);
Py_XSETREF(lz->active, active);
Py_RETURN_NONE;
}
After parsing the argument tuple, source and active are set without validating
that they are iterator objects. This causes issues elsewhere, where the values
are passed PyIter_Next:
static PyObject *
chain_next(chainobject *lz)
{
PyObject *item;
if (lz->source == NULL)
return NULL; /* already stopped */
if (lz->active == NULL) {
PyObject *iterable = PyIter_Next(lz->source);
if (iterable == NULL) {
Py_CLEAR(lz->source);
return NULL; /* no more input
sources */
}
lz->active = PyObject_GetIter(iterable);
Py_DECREF(iterable);
if (lz->active == NULL) {
Py_CLEAR(lz->source);
return NULL; /* input not iterable */
}
}
item = PyIter_Next(lz->active);
if (item != NULL)
return item;
if (PyErr_Occurred()) {
if (PyErr_ExceptionMatches(PyExc_StopIteration))
PyErr_Clear();
else
return NULL; /* input raised an
exception */
}
Py_CLEAR(lz->active);
return chain_next(lz); /* recurse and use next active
*/
}
In some cases, this can lead to a DEP access violation. It might be possible to
exploit this to achieve code execution.
(4074.198c): Access violation - code c0000005 (first chance)
First chance exceptions are reported before any exception handling.
This exception may be expected and handled.
eax=00000000 ebx=0132fa10 ecx=5b547028 edx=00000002 esi=0132fa10 edi=5b37b3e0
eip=00000000 esp=009ef940 ebp=009ef94c iopl=0 nv up ei pl zr na pe nc
cs=0023 ss=002b ds=002b es=002b fs=0053 gs=002b efl=00010246
00000000 ?? ???
0:000> k6
ChildEBP RetAddr
WARNING: Frame IP not in any known module. Following frames may be wrong.
009ef93c 5b329ac0 0x0
009ef94c 5b2cb321 python35!PyIter_Next+0x10
[c:\build\cpython\objects\abstract.c @ 2778]
009ef960 5b37b42e python35!chain_next+0x21
[c:\build\cpython\modules\itertoolsmodule.c @ 1846]
009ef970 5b33fedd python35!wrap_next+0x4e
[c:\build\cpython\objects\typeobject.c @ 5470]
009ef990 5b328b9d python35!wrapper_call+0x7d
[c:\build\cpython\objects\descrobject.c @ 1195]
009ef9ac 5b3c463c python35!PyObject_Call+0x6d
[c:\build\cpython\objects\abstract.c @ 2167]
To fix this issue, it is recommended that chain_setstate() be updated to
validate its arguments. A proposed patch has been attached.
static PyObject *
chain_setstate(chainobject *lz, PyObject *state)
{
PyObject *source, *active=NULL;
if (! PyArg_ParseTuple(state, "O|O", &source, &active))
return NULL;
if (!PyIter_Check(source) || (active != NULL && !PyIter_Check(active))) {
PyErr_SetString(PyExc_ValueError, "Arguments must be iterators.");
return NULL;
}
Py_INCREF(source);
Py_XSETREF(lz->source, source);
Py_XINCREF(active);
Py_XSETREF(lz->active, active);
Py_RETURN_NONE;
}
----------
components: Library (Lib)
files: itertools.patch
keywords: patch
messages: 277799
nosy: JohnLeitch
priority: normal
severity: normal
status: open
title: chain.__setstate__ Type Confusion
type: security
versions: Python 3.5
Added file: http://bugs.python.org/file44899/itertools.patch
_______________________________________
Python tracker <[email protected]>
<http://bugs.python.org/issue28322>
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