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bindings/blst.swg: acquire Python memoryview buffers before use #306

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bindings/blst.swg: acquire Python memoryview buffers before use #306

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30 changes: 20 additions & 10 deletions bindings/blst.swg
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Original file line number Diff line number Diff line change
Expand Up @@ -222,7 +222,8 @@ static int PyLong_GetSign(PyObject *obj, int *sign)

#ifdef __cplusplus
%typemap(in) (const POINT* points[], size_t npoints)
(std::unique_ptr<$*1_ltype[]> points, size_t _global_npoints) %{
(std::unique_ptr<$*1_ltype[]> points, size_t _global_npoints,
Py_buffer view = {}) %{
if (PyList_Check($input)) {
_global_npoints = PyList_Size($input);

Expand Down Expand Up @@ -253,17 +254,19 @@ static int PyLong_GetSign(PyObject *obj, int *sign)
$1 = points.get();
$2 = _global_npoints = nbytes / sizeof(*points[0]);
} else if (PyMemoryView_Check($input)) { // output from to_affine()
Py_buffer *buf = PyMemoryView_GET_BUFFER($input);
// rejects released and non-contiguous views, holds the buffer
if (PyObject_GetBuffer($input, &view, PyBUF_SIMPLE) < 0)
SWIG_fail;

if (!PyBytes_Check(buf->obj))
if (!PyBytes_Check(PyMemoryView_GET_BUFFER($input)->obj))
SWIG_exception_fail(SWIG_TypeError, "in method '$symname', "
"expecting 'bytes' in "
"'memoryview' for points[]");
points = std::unique_ptr<$*1_ltype[]>(new $*1_ltype[2]);
points[0] = ($*1_ltype)buf->buf;
points[0] = ($*1_ltype)view.buf;
points[1] = nullptr;
$1 = points.get();
$2 = _global_npoints = buf->len / sizeof(*points[0]);
$2 = _global_npoints = view.len / sizeof(*points[0]);
} else {
SWIG_exception_fail(SWIG_TypeError, "in method '$symname', expecting "
"'list', 'bytes' or 'memoryview' "
Expand All @@ -273,6 +276,8 @@ static int PyLong_GetSign(PyObject *obj, int *sign)
SWIG_exception_fail(SWIG_TypeError, "in method '$symname', expecting "
"non-empty set of points[]");
%}
%typemap(freearg) (const POINT* points[], size_t npoints)
%{ PyBuffer_Release(&view$argnum); %}
%apply (const POINT* points[], size_t npoints) {
(const blst::P1_Affine* const points[], size_t npoints),
(const blst::P2_Affine* const points[], size_t npoints),
Expand Down Expand Up @@ -320,7 +325,7 @@ static int PyLong_GetSign(PyObject *obj, int *sign)
%nodefault blst::P2_Affines;

%typemap(in) (const byte* const scalars[], size_t nbits)
(std::unique_ptr<byte[]> bytes, byte *scalars[2]) %{
(std::unique_ptr<byte[]> bytes, byte *scalars[2], Py_buffer view = {}) %{
if (PyList_Check($input)) {
if ((size_t)PyList_Size($input) != _global_npoints)
SWIG_exception_fail(SWIG_IndexError, "in method '$symname', 'list' "
Expand Down Expand Up @@ -376,16 +381,19 @@ static int PyLong_GetSign(PyObject *obj, int *sign)
$1 = scalars;
$2 = 8 * (PyByteArray_Size($input) / _global_npoints);
} else if (PyMemoryView_Check($input)) {
Py_buffer *buf = PyMemoryView_GET_BUFFER($input);
// rejects released and non-contiguous views, holds the buffer
if (PyObject_GetBuffer($input, &view, PyBUF_SIMPLE) < 0)
SWIG_fail;

if (!PyBytes_Check(buf->obj) && !PyByteArray_Check(buf->obj))
PyObject *obj = PyMemoryView_GET_BUFFER($input)->obj;
if (!PyBytes_Check(obj) && !PyByteArray_Check(obj))
SWIG_exception_fail(SWIG_TypeError, "in method '$symname', "
"expecting 'bytes' in "
"'memoryview' for points[]");
scalars[0] = ($*1_ltype)buf->buf;
scalars[0] = ($*1_ltype)view.buf;
scalars[1] = nullptr;
$1 = scalars;
$2 = 8 * (buf->len / _global_npoints);
$2 = 8 * (view.len / _global_npoints);
} else {
SWIG_exception_fail(SWIG_TypeError, "in method '$symname', expecting "
"'list', 'bytes', 'bytearray' "
Expand All @@ -395,6 +403,8 @@ static int PyLong_GetSign(PyObject *obj, int *sign)
SWIG_exception_fail(SWIG_ValueError, "in method '$symname', zero-length "
"scalars, likely an error");
%}
%typemap(freearg) (const byte* const scalars[], size_t nbits)
%{ PyBuffer_Release(&view$argnum); %}

%typemap(out) BLST_ERROR %{
if ($1 != BLST_SUCCESS) {
Expand Down
16 changes: 16 additions & 0 deletions bindings/python/run.me
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Original file line number Diff line number Diff line change
Expand Up @@ -217,6 +217,22 @@ a = blst.P2_Affines.mult_pippenger(blst.P2_Affines.as_memory(points), scalars)
if not a.is_equal(blst.G2().mult(total)):
raise AssertionError("disaster")

# released or non-contiguous memoryview-s are to be rejected
mem = memoryview(bytes(blst.P2_Affines.as_memory(points)))
for args in [(mem[::-1], scalars),
(blst.P2_Affines.as_memory(points), memoryview(bytes(8*42))[::-1])]:
try:
blst.P2_Affines.mult_pippenger(*args)
raise AssertionError("disaster")
except BufferError:
pass
mem.release()
try:
blst.P2_Affines.mult_pippenger(mem, scalars)
raise AssertionError("disaster")
except ValueError:
pass

########################################################################
# rudimentary blind signature PoC

Expand Down
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