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Issue #13612: handle unknown encodings without a buffer overflow.

Browse source 
This affects pyexpat and _elementtree. PyExpat_CAPI now exposes a new
function - DefaultUnknownEncodingHandler.

Based on a patch by Serhiy Storchaka.
This commit is contained in:
Eli Bendersky 2013-05-25 05:27:10 -07:00
commit 7b3022f24f
4 changed files with 128 additions and 79 deletions
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43
Modules/_elementtree.c
View file

@ -3094,47 +3094,6 @@ expat_pi_handler(XMLParserObject* self, const XML_Char* target_in,
}
}
static int
expat_unknown_encoding_handler(XMLParserObject *self, const XML_Char *name,
XML_Encoding *info)
{
PyObject* u;
unsigned char s[256];
int i;
void *data;
unsigned int kind;
memset(info, 0, sizeof(XML_Encoding));
for (i = 0; i < 256; i++)
s[i] = i;
u = PyUnicode_Decode((char*) s, 256, name, "replace");
if (!u)
return XML_STATUS_ERROR;
if (PyUnicode_READY(u))
return XML_STATUS_ERROR;
if (PyUnicode_GET_LENGTH(u) != 256) {
Py_DECREF(u);
return XML_STATUS_ERROR;
}
kind = PyUnicode_KIND(u);
data = PyUnicode_DATA(u);
for (i = 0; i < 256; i++) {
Py_UCS4 ch = PyUnicode_READ(kind, data, i);
if (ch != Py_UNICODE_REPLACEMENT_CHARACTER)
info->map[i] = ch;
else
info->map[i] = -1;
}
Py_DECREF(u);
return XML_STATUS_OK;
}
/* -------------------------------------------------------------------- */
static PyObject *
@ -3236,7 +3195,7 @@ xmlparser_init(PyObject *self, PyObject *args, PyObject *kwds)
);
EXPAT(SetUnknownEncodingHandler)(
self_xp->parser,
(XML_UnknownEncodingHandler) expat_unknown_encoding_handler, NULL
EXPAT(DefaultUnknownEncodingHandler), NULL
);
return 0;

68
Modules/pyexpat.c
View file

@ -1111,53 +1111,49 @@ static struct PyMethodDef xmlparse_methods[] = {
Make it as simple as possible.
*/
static char template_buffer[257];
static void
init_template_buffer(void)
{
int i;
for (i = 0; i < 256; i++) {
template_buffer[i] = i;
}
template_buffer[256] = 0;
}
static int
PyUnknownEncodingHandler(void *encodingHandlerData,
const XML_Char *name,
XML_Encoding *info)
{
PyUnicodeObject *_u_string = NULL;
int result = 0;
static unsigned char template_buffer[256] = {0};
PyObject* u;
int i;
int kind;
void *data;
unsigned int kind;
/* Yes, supports only 8bit encodings */
_u_string = (PyUnicodeObject *)
PyUnicode_Decode(template_buffer, 256, name, "replace");
if (_u_string == NULL || PyUnicode_READY(_u_string) == -1)
return result;
kind = PyUnicode_KIND(_u_string);
data = PyUnicode_DATA(_u_string);
for (i = 0; i < 256; i++) {
/* Stupid to access directly, but fast */
Py_UCS4 c = PyUnicode_READ(kind, data, i);
if (c == Py_UNICODE_REPLACEMENT_CHARACTER)
info->map[i] = -1;
else
info->map[i] = c;
if (template_buffer[1] == 0) {
for (i = 0; i < 256; i++)
template_buffer[i] = i;
}
u = PyUnicode_Decode((char*) template_buffer, 256, name, "replace");
if (u == NULL || PyUnicode_READY(u))
return XML_STATUS_ERROR;
if (PyUnicode_GET_LENGTH(u) != 256) {
Py_DECREF(u);
PyErr_SetString(PyExc_ValueError,
"multi-byte encodings are not supported");
return XML_STATUS_ERROR;
}
kind = PyUnicode_KIND(u);
data = PyUnicode_DATA(u);
for (i = 0; i < 256; i++) {
Py_UCS4 ch = PyUnicode_READ(kind, data, i);
if (ch != Py_UNICODE_REPLACEMENT_CHARACTER)
info->map[i] = ch;
else
info->map[i] = -1;
}
info->data = NULL;
info->convert = NULL;
info->release = NULL;
result = 1;
Py_DECREF(_u_string);
return result;
Py_DECREF(u);
return XML_STATUS_OK;
}
@ -1752,7 +1748,6 @@ MODULE_INITFUNC(void)
Py_BuildValue("(iii)", info.major,
info.minor, info.micro));
}
init_template_buffer();
/* XXX When Expat supports some way of figuring out how it was
compiled, this should check and set native_encoding
appropriately.
@ -1938,6 +1933,7 @@ MODULE_INITFUNC(void)
capi.SetUserData = XML_SetUserData;
capi.SetStartDoctypeDeclHandler = XML_SetStartDoctypeDeclHandler;
capi.SetEncoding = XML_SetEncoding;
capi.DefaultUnknownEncodingHandler = PyUnknownEncodingHandler;
/* export using capsule */
capi_object = PyCapsule_New(&capi, PyExpat_CAPSULE_NAME, NULL);