215 lines
6.6 KiB
Cython
215 lines
6.6 KiB
Cython
class CPacket:
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'''parent class designed to index/parse full tcp/ip packets (including ethernet). two alternate
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constructors are supplied to support nfqueue or raw sockets.
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raw socket:
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packet = RawPacket.interface(data, address, socket)
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nfqueue:
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packet = RawPacket.netfilter(nfqueue)
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the before_exit method can be overridden to extend the parsing functionality, for example to group
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objects in namedtuples or to index application data.
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'''
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def __new__(cls, *args, **kwargs):
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if (cls is RawPacket):
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raise TypeError('RawPacket can only be used via inheritance.')
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return object.__new__(cls)
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def __cinit__(self):
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self._verdict_is_set = False
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self._mark = 0
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self.protocol = PROTO.NOT_SET
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def __str__(self):
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cdef iphdr * hdr = < iphdr * > self.payload
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protocol = PROTOCOLS.get(hdr.protocol, "Unknown protocol")
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return "%s packet, %s bytes" % (protocol, self.payload_len)
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# NOTE: this will be callback target for nfqueue
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cdef netfilter(nfq_q_handle * qh, nfgenmsg * nfmsg, nfq_data * nfa, void * data):
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'''alternate constructor. used to start listener/proxy instances using nfqueue bindings.'''
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'''Assign a packet from NFQ to this object. Parse the header and load local values.'''
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self = cls()
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self.parse()
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self._qh = qh
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self._nfa = nfa
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self._hdr = nfq_get_msg_packet_hdr(nfa)
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self.id = ntohl(self._hdr.packet_id)
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self.hw_protocol = ntohs(self._hdr.hw_protocol)
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self.hook = self._hdr.hook
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self.payload_len = nfq_get_payload(self._nfa, & self.data)
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if self.payload_len < 0:
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raise OSError("Failed to get payload of packet.")
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# timestamp gets assigned via pointer/struct -> time_val: (t_sec, t_usec).
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nfq_get_timestamp(self._nfa, & self.timestamp)
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cdef u_int_32_t self._mark = nfq_get_nfmark(nfa)
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# if (self.continue_condition):
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# self._before_exit()
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# TODO: send to module callback here
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# with gil:
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# callback(self)
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return 0
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cdef void verdict(self, u_int32_t verdict):
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'''Call appropriate set_verdict... function on packet.'''
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if self._verdict_is_set:
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raise RuntimeWarning("Verdict already given for this packet.")
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cdef u_int32_t modified_payload_len = 0
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cdef unsigned char * modified_payload = NULL
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# rewriting payload data/len
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if self._given_payload:
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modified_payload_len = len(self._given_payload)
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modified_payload = self._given_payload
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if self._modified_mark:
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nfq_set_verdict2(
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self._qh, self.id, verdict, self._modified_mark, modified_payload_len, modified_payload
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)
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else:
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nfq_set_verdict(
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self._qh, self.id, verdict, modified_payload_len, modified_payload
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)
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self._verdict_is_set = True
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cdef def parse(self) with nogil:
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'''index tcp/ip packet layers 3 & 4 for use as instance objects.
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the before_exit method will be called before returning, which can be used to create
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subclass specific objects like namedtuples or application layer data.'''
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cdef iphdr * ip_header = < iphdr * > self.payload
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cdef u_int8_t iphdr_len = iphdr.tos & 15) * 4
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if (iphdr.protocol == IPPROTO_TCP):
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cdef tcphdr * tcp_header = < tcphdr * > self.payload[iphdr_len:]
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return 0
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if (iphdr.protocol == IPPROTO_UDP):
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cdef tcphdr * icmp_header = < tcphdr * > self.payload[iphdr_len:]
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return 0
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if (iphdr.protocol == IPPROTO_ICMP):
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cdef icmphdr * icmp_header = < icmphdr * > self.payload[iphdr_len:]
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return 0
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return 1
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def _before_exit(self):
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'''executes before returning from parse call.
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May be overridden.
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'''
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pass
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@property
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def continue_condition(self):
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'''controls whether the _before_exit method gets called. must return a boolean.
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May be overridden.
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'''
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return True
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cdef class NetfilterQueue:
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'''Handle a single numbered queue.'''
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def __cinit__(self, *args, **kwargs):
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self.af = kwargs.get('af', PF_INET)
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self.h = nfq_open()
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if self.h == NULL:
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raise OSError('Failed to open NFQueue.')
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# This does NOT kick out previous running queues
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nfq_unbind_pf(self.h, self.af)
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if nfq_bind_pf(self.h, self.af) < 0:
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raise OSError('Failed to bind family %s. Are you root?' % self.af)
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def __dealloc__(self):
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if self.qh != NULL:
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nfq_destroy_queue(self.qh)
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# Don't call nfq_unbind_pf unless you want to disconnect any other
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# processes using this libnetfilter_queue on this protocol family!
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nfq_close(self.h)
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def bind(self, int queue_num, object user_callback, u_int16_t max_len=DEFAULT_MAX_QUEUELEN,
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u_int8_t mode=NFQNL_COPY_PACKET, u_int16_t range=MaxPacketSize, u_int32_t sock_len=SockRcvSize):
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'''Create and bind to a new queue.'''
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cdef unsigned int newsiz
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self.user_callback = user_callback
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self.qh = nfq_create_queue(self.h, queue_num, < nfq_callback * > global_callback, < void * > self)
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if self.qh == NULL:
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raise OSError(f'Failed to create queue {queue_num}')
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if range > MaxCopySize:
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range = MaxCopySize
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if nfq_set_mode(self.qh, mode, range) < 0:
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raise OSError("Failed to set packet copy mode.")
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nfq_set_queue_maxlen(self.qh, max_len)
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newsiz = nfnl_rcvbufsiz(nfq_nfnlh(self.h), sock_len)
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if newsiz != sock_len * 2:
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raise RuntimeWarning("Socket rcvbuf limit is now %d, requested %d." % (newsiz, sock_len))
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def unbind(self):
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'''Destroy the queue.'''
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if self.qh != NULL:
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nfq_destroy_queue(self.qh)
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self.qh = NULL
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# See warning about nfq _unbind_pf in __dealloc__ above.
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def get_fd(self):
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'''Get the file descriptor of the queue handler.'''
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return nfq_fd(self.h)
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def run(self, bint block=True):
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'''Accept packets using recv.'''
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cdef int fd = self.get_fd()
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cdef char buf[4096]
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cdef int rv
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cdef int recv_flags
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recv_flags = 0
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while True:
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with nogil:
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rv = recv(fd, buf, sizeof(buf), recv_flags)
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print(rv)
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if (rv >= 0):
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nfq_handle_packet(self.h, buf, rv)
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else:
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if errno != ENOBUFS:
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break
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