Allow a Py_buffer as data for Rules_match (#152)

* Allow a Py_buffer as data for Rules_match

This makes rules matching compatible with data objects
`PyArg_ParseTuple` does not consider read-only (even though they might
actually be), such a memoryviews. The main change is replacing the `s#`
formatter with `s*` and replacing the `(pointer, length)` pair with a
`Py_buffer` object accordingly. Additional care must be taken to release
the `Py_buffer` on every error path.

* Rules_match: zero-initialize data

PyArg_ParseTupleAndKeywords does not initialize optional fields unless
they are passed, which means we need to zero-initialize the data buffer
to be sure the later NULL checks always work.

This commit also gets rid of the unneeded has_data flag.

* Add test for matching on a memoryview

tests.py

@@ -1086,6 +1086,13 @@ class TestYara(unittest.TestCase):
         self.assertTrue(r[0].is_global == True)
         self.assertTrue(r[1].is_private == True)
 
+    def testMatchMemoryview(self):
+
+        r = yara.compile(source='rule test { strings: $s = "test" condition: $s }')
+        data = memoryview(b"test")
+
+        self.assertTrue(r.match(data=data))
+
 
 if __name__ == "__main__":
     unittest.main()

yara-python.c

@@ -1372,11 +1372,10 @@ static PyObject* Rules_match(
       };
 
   char* filepath = NULL;
-  char* data = NULL;
+  Py_buffer data = {0};
 
   int pid = 0;
   int timeout = 0;
-  Py_ssize_t length = 0;
   int error = ERROR_SUCCESS;
   int fast_mode = 0;
 
@@ -1396,12 +1395,11 @@ static PyObject* Rules_match(
   if (PyArg_ParseTupleAndKeywords(
         args,
         keywords,
-        "|sis#OOOiOOi",
+        "|sis*OOOiOOi",
         kwlist,
         &filepath,
         &pid,
         &data,
-        &length,
         &externals,
         &callback_data.callback,
         &fast,
@@ -1410,7 +1408,7 @@ static PyObject* Rules_match(
         &callback_data.modules_callback,
         &callback_data.which))
   {
-    if (filepath == NULL && data == NULL && pid == 0)
+    if (filepath == NULL && data.buf == NULL && pid == 0)
     {
       return PyErr_Format(
           PyExc_TypeError,
@@ -1421,6 +1419,7 @@ static PyObject* Rules_match(
     {
       if (!PyCallable_Check(callback_data.callback))
       {
+        PyBuffer_Release(&data);
         return PyErr_Format(
             PyExc_TypeError,
             "'callback' must be callable");
@@ -1431,6 +1430,7 @@ static PyObject* Rules_match(
     {
       if (!PyCallable_Check(callback_data.modules_callback))
       {
+        PyBuffer_Release(&data);
         return PyErr_Format(
             PyExc_TypeError,
             "'modules_callback' must be callable");
@@ -1441,6 +1441,7 @@ static PyObject* Rules_match(
     {
       if (!PyDict_Check(callback_data.modules_data))
       {
+        PyBuffer_Release(&data);
         return PyErr_Format(
             PyExc_TypeError,
             "'modules_data' must be a dictionary");
@@ -1455,11 +1456,14 @@ static PyObject* Rules_match(
         {
           // Restore original externals provided during compiling.
           process_match_externals(object->externals, object->rules);
+
+          PyBuffer_Release(&data);
           return NULL;
         }
       }
       else
       {
+        PyBuffer_Release(&data);
         return PyErr_Format(
             PyExc_TypeError,
             "'externals' must be a dictionary");
@@ -1487,7 +1491,7 @@ static PyObject* Rules_match(
 
       Py_END_ALLOW_THREADS
     }
-    else if (data != NULL)
+    else if (data.buf != NULL)
     {
       callback_data.matches = PyList_New(0);
 
@@ -1495,8 +1499,8 @@ static PyObject* Rules_match(
 
       error = yr_rules_scan_mem(
           object->rules,
-          (unsigned char*) data,
-          (size_t) length,
+          (unsigned char*) data.buf,
+          (size_t) data.len,
           fast_mode ? SCAN_FLAGS_FAST_MODE : 0,
           yara_callback,
           &callback_data,
@@ -1521,6 +1525,8 @@ static PyObject* Rules_match(
       Py_END_ALLOW_THREADS
     }
 
+    PyBuffer_Release(&data);
+
     // Restore original externals provided during compiling.
     if (object->externals != NULL)
     {
@@ -1542,14 +1548,14 @@ static PyObject* Rules_match(
         {
           handle_error(error, filepath);
         }
-        else if (data != NULL)
-        {
-          handle_error(error, "<data>");
-        }
         else if (pid != 0)
         {
           handle_error(error, "<proc>");
         }
+        else
+        {
+          handle_error(error, "<data>");
+        }
 
         #ifdef PROFILING_ENABLED
         PyObject* exception = PyErr_Occurred();