#!/usr/bin/env python3
'''
Bind to a Linux netfilter queue. Send packets to a user-specified callback
function.
Copyright: (c) 2011, Kerkhoff Technologies Inc.
License: MIT; see SOURCE-LICENSE.txt
'''
'''
Expanded features + general refactor to be used with DNXFIREWALL.
- DOWRIGHT @ Wright Network Solutions, LLC.
'''
import socket
# Constants for module users
cdef int COPY_NONE = 0
cdef int COPY_META = 1
cdef int COPY_PACKET = 2
cdef u_int16_t DEFAULT_MAX_QUEUELEN = 1024
cdef u_int16_t MaxPacketSize = 0xFFFF
# buffer size - metadata size
cdef u_int16_t MaxCopySize = 4096 - 80
# Socket queue should hold max number of packets of copy size bytes
# formula: DEF_MAX_QUEUELEN * (MaxCopySize+SockOverhead) / 2
cdef u_int32_t SockRcvSize = 1024 * 4796 // 2
cdef int global_callback(nfq_q_handle * qh, nfgenmsg * nfmsg, nfq_data * nfa, void * data) with gil:
'''Create a Packet and pass it to appropriate callback.'''
cdef NetfilterQueue nfqueue = < NetfilterQueue > data
cdef object user_callback = < object > nfqueue.user_callback
packet = Packet()
packet.set_nfq_data(qh, nfa)
user_callback(packet)
return 1
cdef class Packet:
'''A packet received from NetfilterQueue.'''
def __cinit__(self):
self._verdict_is_set = False
self._mark = 0
self._given_payload = None
def __str__(self):
cdef ip_header * hdr = < ip_header * > self.payload
protocol = PROTOCOLS.get(hdr.protocol, "Unknown protocol")
return "%s packet, %s bytes" % (protocol, self.payload_len)
cdef set_nfq_data(self, nfq_q_handle * qh, nfq_data * nfa):
'''Assign a packet from NFQ to this object. Parse the header and load local values.'''
self._qh = qh
self._nfa = nfa
self._hdr = nfq_get_msg_packet_hdr(nfa)
self.id = ntohl(self._hdr.packet_id)
self.hw_protocol = ntohs(self._hdr.hw_protocol)
self.hook = self._hdr.hook
self.payload_len = nfq_get_payload(self._nfa, &self.payload)
if self.payload_len < 0:
raise OSError("Failed to get payload of packet.")
self._payload
# timestamp gets assigned via pointer/struct -> time_val: (t_sec, t_usec).
nfq_get_timestamp(self._nfa, &self.timestamp)
cdef u_int32_t mark = nfq_get_nfmark(nfa)
cdef void verdict(self, u_int32_t verdict):
'''Call appropriate set_verdict... function on packet.'''
if self._verdict_is_set:
raise RuntimeWarning("Verdict already given for this packet.")
cdef u_int32_t modified_payload_len = 0
cdef unsigned char * modified_payload = NULL
# rewriting payload data/len
if self._given_payload:
modified_payload_len = len(self._given_payload)
modified_payload = self._given_payload
if self._modified_mark:
nfq_set_verdict2(
self._qh, self.id, verdict, self._modified_mark, modified_payload_len, modified_payload
)
else:
nfq_set_verdict(
self._qh, self.id, verdict, modified_payload_len, modified_payload
)
self._verdict_is_set = True
cpdef get_inint(self, bint name=False):
'''Returns index of inbound interface of packet. If the packet sourced from localhost or the input
interface is not known, 0 will be returned.
if name=True, socket.if_indextoname() will be returned.
'''
cdef object in_interface_name
in_interface = nfq_get_indev(self._nfa)
if not name:
return in_interface
try:
in_interface_name = socket.if_indextoname(in_interface)
except OSError:
in_interface_name = 'unknown'
return in_interface_name
# NOTE: keeping these funtions separate instead of making an argument option to adjust which interface to return.
# this will keep it explicit for which interface is returning to minimize chance of confusion/bugs.
cpdef get_outint(self, bint name=False):
'''Returns index of outbound interface of packet. If the packet is destined for localhost or the output
interface is not yet known, 0 will be returned.
if name=True, socket.if_indextoname() will be returned.
'''
cdef object out_interface_name
out_interface = nfq_get_outdev(self._nfa)
if not name:
return out_interface
try:
out_interface_name = socket.if_indextoname(out_interface)
except OSError:
out_interface_name = 'unknown'
return out_interface_name
def get_mark(self):
'''Return mark set at first receipt of packet.'''
return self._mark
cpdef update_mark(self, u_int32_t mark):
'''Modifies the running mark of the packet. This will not override the initial mark received, but any
subsequent update will override the previous.'''
self._modified_mark = mark
def get_hw(self):
'''Return the source mac address of the packet.'''
cdef object mac_addr
self._hw = nfq_get_packet_hw(self._nfa)
if self._hw == NULL:
# nfq_get_packet_hw doesn't work on OUTPUT and PREROUTING chains
# NOTE: making this a quick fail scenario since this would likely cause problems later in the packet
# parsing process and forcing error handling will ensure it is dealt with [properly].
raise OSError('MAC address not available in OUTPUT and PREROUTING chains')
# NOTE: can this not just be directly referenced below?
self.hw_addr = self._hw.hw_addr
mac_addr = PyBytes_FromStringAndSize( < char * > self.hw_addr, 8)
return mac_addr
def get_payload(self):
'''Return payload as Python string.'''
cdef object payload
payload = self.payload[:self.payload_len]
return payload
cpdef set_payload(self, bytes payload):
'''Set the new payload of this packet.'''
self._given_payload = payload
cpdef Py_ssize_t get_payload_len(self):
return self.payload_len
cpdef double get_timestamp(self):
return self.timestamp.tv_sec + (self.timestamp.tv_usec / 1000000.0)
cpdef accept(self):
'''Accept the packet.'''
self.verdict(NF_ACCEPT)
cpdef drop(self):
'''Drop the packet.'''
self.verdict(NF_DROP)
cpdef forward(self, u_int16_t queue_num):
'''Send the packet to a different queue.'''
cdef u_int32_t forward_to_queue
forward_to_queue = queue_num << 16 | NF_QUEUE
self.verdict(forward_to_queue)
cpdef repeat(self):
'''Repeat the packet.'''
self.verdict(NF_REPEAT)
cdef class NetfilterQueue:
'''Handle a single numbered queue.'''
def __cinit__(self, *args, **kwargs):
self.af = kwargs.get('af', PF_INET)
self.h = nfq_open()
if self.h == NULL:
raise OSError('Failed to open NFQueue.')
# This does NOT kick out previous running queues
nfq_unbind_pf(self.h, self.af)
if nfq_bind_pf(self.h, self.af) < 0:
raise OSError('Failed to bind family %s. Are you root?' % self.af)
def __dealloc__(self):
if self.qh != NULL:
nfq_destroy_queue(self.qh)
# Don't call nfq_unbind_pf unless you want to disconnect any other
# processes using this libnetfilter_queue on this protocol family!
nfq_close(self.h)
def bind(self, int queue_num, object user_callback, u_int16_t max_len=DEFAULT_MAX_QUEUELEN,
u_int8_t mode=NFQNL_COPY_PACKET, u_int16_t range=MaxPacketSize, u_int32_t sock_len=SockRcvSize):
'''Create and bind to a new queue.'''
cdef unsigned int newsiz
self.user_callback = user_callback
self.qh = nfq_create_queue(self.h, queue_num, < nfq_callback * > global_callback, < void * > self)
if self.qh == NULL:
raise OSError(f'Failed to create queue {queue_num}')
if range > MaxCopySize:
range = MaxCopySize
if nfq_set_mode(self.qh, mode, range) < 0:
raise OSError("Failed to set packet copy mode.")
nfq_set_queue_maxlen(self.qh, max_len)
newsiz = nfnl_rcvbufsiz(nfq_nfnlh(self.h), sock_len)
if newsiz != sock_len * 2:
raise RuntimeWarning("Socket rcvbuf limit is now %d, requested %d." % (newsiz, sock_len))
def unbind(self):
'''Destroy the queue.'''
if self.qh != NULL:
nfq_destroy_queue(self.qh)
self.qh = NULL
# See warning about nfq _unbind_pf in __dealloc__ above.
def get_fd(self):
'''Get the file descriptor of the queue handler.'''
return nfq_fd(self.h)
def run(self, bint block=True):
'''Accept packets using recv.'''
cdef int fd = self.get_fd()
cdef char buf[4096]
cdef int rv
cdef int recv_flags
recv_flags = 0
while True:
with nogil:
rv = recv(fd, buf, sizeof(buf), recv_flags)
print(rv)
if (rv >= 0):
nfq_handle_packet(self.h, buf, rv)
else:
if errno != ENOBUFS:
break
def run_socket(self, s):
'''Accept packets using socket.recv so that, for example, gevent can monkeypatch it.'''
while True:
try:
buf = s.recv(4096)
except socket.error as e:
err = e.args[0]
if err == ENOBUFS:
continue
elif err == EAGAIN or err == EWOULDBLOCK:
# This should only happen with a non-blocking socket, and the
# app should call run_socket again when more data is available.
break
else:
# This is bad. Let the caller handle it.
raise e
else:
rv = len(buf)
if rv >= 0:
nfq_handle_packet(self.h, buf, rv)
else:
break
PROTOCOLS = {
0: "HOPOPT",
1: "ICMP",
2: "IGMP",
3: "GGP",
4: "IP",
5: "ST",
6: "TCP",
7: "CBT",
8: "EGP",
9: "IGP",
10: "BBN-RCC-MON",
11: "NVP-II",
12: "PUP",
13: "ARGUS",
14: "EMCON",
15: "XNET",
16: "CHAOS",
17: "UDP",
18: "MUX",
19: "DCN-MEAS",
20: "HMP",
21: "PRM",
22: "XNS-IDP",
23: "TRUNK-1",
24: "TRUNK-2",
25: "LEAF-1",
26: "LEAF-2",
27: "RDP",
28: "IRTP",
29: "ISO-TP4",
30: "NETBLT",
31: "MFE-NSP",
32: "MERIT-INP",
33: "DCCP",
34: "3PC",
35: "IDPR",
36: "XTP",
37: "DDP",
38: "IDPR-CMTP",
39: "TP++",
40: "IL",
41: "IPv6",
42: "SDRP",
43: "IPv6-Route",
44: "IPv6-Frag",
45: "IDRP",
46: "RSVP",
47: "GRE",
48: "DSR",
49: "BNA",
50: "ESP",
51: "AH",
52: "I-NLSP",
53: "SWIPE",
54: "NARP",
55: "MOBILE",
56: "TLSP",
57: "SKIP",
58: "IPv6-ICMP",
59: "IPv6-NoNxt",
60: "IPv6-Opts",
61: "any host internal protocol",
62: "CFTP",
63: "any local network",
64: "SAT-EXPAK",
65: "KRYPTOLAN",
66: "RVD",
67: "IPPC",
68: "any distributed file system",
69: "SAT-MON",
70: "VISA",
71: "IPCV",
72: "CPNX",
73: "CPHB",
74: "WSN",
75: "PVP",
76: "BR-SAT-MON",
77: "SUN-ND",
78: "WB-MON",
79: "WB-EXPAK",
80: "ISO-IP",
81: "VMTP",
82: "SECURE-VMTP",
83: "VINES",
84: "TTP",
85: "NSFNET-IGP",
86: "DGP",
87: "TCF",
88: "EIGRP",
89: "OSPFIGP",
90: "Sprite-RPC",
91: "LARP",
92: "MTP",
93: "AX.25",
94: "IPIP",
95: "MICP",
96: "SCC-SP",
97: "ETHERIP",
98: "ENCAP",
99: "any private encryption scheme",
100: "GMTP",
101: "IFMP",
102: "PNNI",
103: "PIM",
104: "ARIS",
105: "SCPS",
106: "QNX",
107: "A/N",
108: "IPComp",
109: "SNP",
110: "Compaq-Peer",
111: "IPX-in-IP",
112: "VRRP",
113: "PGM",
114: "any 0-hop protocol",
115: "L2TP",
116: "DDX",
117: "IATP",
118: "STP",
119: "SRP",
120: "UTI",
121: "SMP",
122: "SM",
123: "PTP",
124: "ISIS",
125: "FIRE",
126: "CRTP",
127: "CRUDP",
128: "SSCOPMCE",
129: "IPLT",
130: "SPS",
131: "PIPE",
132: "SCTP",
133: "FC",
134: "RSVP-E2E-IGNORE",
135: "Mobility",
136: "UDPLite",
137: "MPLS-in-IP",
138: "manet",
139: "HIP",
140: "Shim6",
255: "Reserved",
}