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/*
* Copyright (c) 2014 CORE Security Technologies
*
* This software is provided under under a slightly modified version
* of the Apache Software License. See the accompanying LICENSE file
* for more information.
*
*/
#define PY_SSIZE_T_CLEAN
#include <pcap.h>
#include <Python.h>
#include "bpfobj.h"
#include "pcapy.h"
// internal bpfobject
typedef struct {
PyObject_HEAD
struct bpf_program bpf;
} bpfobject;
// BPFProgramType
static void
bpfprog_dealloc(register bpfobject* bpf)
{
#ifndef WIN32 // XXX: is this missing from winpcap 2.3?
pcap_freecode(&bpf->bpf);
#endif
PyObject_Del(bpf);
}
PyObject* BPFError;
// BPFProgram methods
static PyObject* p_filter(register bpfobject* bpf, PyObject* args);
static PyObject* p_get_bpf(register bpfobject* bpf, PyObject* args);
static PyObject* p_new_bpfobject(PyTypeObject *type, PyObject* args, PyObject *kwags);
static PyMethodDef bpf_methods[] = {
{"filter", (PyCFunction) p_filter, METH_VARARGS, "filter(packet) applies the filter to the packet, returns 0 if there's no match"},
{"get_bpf", (PyCFunction) p_get_bpf, METH_NOARGS, "return packet-matching code as decimal numbers"},
{NULL, NULL} /* sentinel */
};
static PyObject*
bpfprog_getattr(bpfobject* pp, char* name)
{
#if PY_MAJOR_VERSION >= 3
PyObject *nameobj = PyUnicode_FromString(name);
PyObject *attr = PyObject_GenericGetAttr((PyObject *)pp, nameobj);
Py_DECREF(nameobj);
return attr;
#else
return Py_FindMethod(bpf_methods, (PyObject*)pp, name);
#endif
}
PyTypeObject BPFProgramType = {
#if PY_MAJOR_VERSION >= 3
PyVarObject_HEAD_INIT(&PyType_Type, 0)
"BPFProgram", /* tp_name */
sizeof(bpfobject), /* tp_basicsize */
0, /* tp_itemsize */
(destructor)bpfprog_dealloc, /* tp_dealloc */
0, /* tp_print */
(getattrfunc)bpfprog_getattr, /* tp_getattr */
0, /* tp_setattr */
0, /* tp_reserved */
0, /* tp_repr */
0, /* tp_as_number */
0, /* tp_as_sequence */
0, /* tp_as_mapping */
0, /* tp_hash */
0, /* tp_call */
0, /* tp_str */
0, /* tp_getattro */
0, /* tp_setattro */
0, /* tp_as_buffer */
Py_TPFLAGS_DEFAULT, /* tp_flags */
"BPF Program Wrapper", /* tp_doc */
0, /* tp_traverse */
0, /* tp_clear */
0, /* tp_richcompare */
0, /* tp_weaklistoffset */
0, /* tp_iter */
0, /* tp_iternext */
bpf_methods, /* tp_methods */
0, /* tp_members */
0, /* tp_getset */
0, /* tp_base */
0, /* tp_dict */
0, /* tp_descr_get */
0, /* tp_descr_set */
0, /* tp_dictoffset */
0, /* tp_init */
0, /* tp_alloc */
p_new_bpfobject /* tp_new */
#else
PyObject_HEAD_INIT(NULL)
0,
"BPFProgram",
sizeof(bpfobject),
0,
/* methods */
(destructor)bpfprog_dealloc, /* tp_dealloc*/
0, /* tp_print*/
(getattrfunc)bpfprog_getattr, /* tp_getattr*/
0, /* tp_setattr*/
0, /*tp_compare*/
0, /*tp_repr*/
0, /*tp_as_number*/
0, /*tp_as_sequence*/
0, /*tp_as_mapping*/
0, /*tp_hash */
0, /*tp_call*/
0, /*tp_str*/
0, /*tp_getattro*/
0, /*tp_setattro*/
0, /*tp_as_buffer*/
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
/*tp_flags*/
"BPF Program Wrapper", /* tp_doc */
0, /* tp_traverse */
0, /* tp_clear */
0, /* tp_richcompare */
0, /* tp_weaklistoffset */
0, /* tp_iter */
0, /* tp_iternext */
bpf_methods, /* tp_methods */
0, /* tp_members */
0, /* tp_getset */
0, /* tp_base */
0, /* tp_dict */
0, /* tp_descr_get */
0, /* tp_descr_set */
0, /* tp_dictoffset */
0, /* tp_init */
0, /* tp_alloc */
p_new_bpfobject /* tp_new */
#endif
};
PyObject*
new_bpfobject(const struct bpf_program &bpfprog)
{
if (PyType_Ready(&BPFProgramType) < 0)
return NULL;
bpfobject *bpf;
bpf = PyObject_New(bpfobject, &BPFProgramType);
if (bpf == NULL)
{
PyErr_SetString(BPFError, "Failed to create object");
return NULL;
}
bpf->bpf = bpfprog;
return (PyObject*)bpf;
}
static PyObject*
p_new_bpfobject(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
char *filter_string;
int linktype = 1; // DLT_EN10MB
if (!PyArg_ParseTuple(args, "s|i", &filter_string, &linktype)){
return NULL;
}
struct bpf_program bpfprog;
if (pcap_compile_nopcap((1<<16), linktype, &bpfprog, filter_string, 0, 0)){
PyErr_SetString(BPFError, "Couldn't compile BPF program");
return NULL;
}
return new_bpfobject(bpfprog);
}
static PyObject*
p_filter(register bpfobject* bpf, PyObject* args)
{
int status;
u_char* packet;
Py_ssize_t len;
if (Py_TYPE(bpf) != &BPFProgramType)
{
PyErr_SetString(BPFError, "Not a bpfprogram object");
return NULL;
}
#if PY_MAJOR_VERSION >= 3
if (!PyArg_ParseTuple(args,"y#:filter",&packet, &len)){
return NULL;
}
#else
if (!PyArg_ParseTuple(args,"s#:filter",&packet, &len)){
return NULL;
}
#endif
status = bpf_filter(bpf->bpf.bf_insns,
packet,
len, len);
return Py_BuildValue("i", status);
}
static PyObject*
p_get_bpf(register bpfobject* bpf, PyObject* args)
{
struct bpf_insn *insn;
int i;
int n = bpf->bpf.bf_len;
PyObject* list;
PyObject* instruction;
insn = bpf->bpf.bf_insns;
if (Py_TYPE(bpf) != &BPFProgramType)
{
PyErr_SetString(BPFError, "Not a bpfprogram object");
return NULL;
}
list = PyList_New(n);
if (!list) {
return NULL;
}
for (i = 0; i < n; ++insn, ++i) {
instruction = Py_BuildValue("IIII", insn->code, insn->jt, insn->jf, insn->k);
if (!instruction) {
Py_DECREF(list);
return NULL;
}
PyList_SET_ITEM(list, i, instruction);
}
return list;
}
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