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icmp_analyzer.py
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icmp_analyzer.py
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import icmpheader
import ipv4header
import entropy
import struct
MAX_DATA_SIZE_v4ICMP = 65507
MIN_DATA_SIZE_v4ICMP = 1
MIN_DATA_SIZE_v4ICMPErrMsg = 28
MAX_DATA_SIZE_v4ICMPErrMsg = 548
# values deprecated icmp types
DEFAULT_DEPRECATED_TYPES = tuple([icmpheader.TYPE_v4SourceQuench, 6,
icmpheader.TYPE_v4InfoRequest, icmpheader.TYPE_v4InfoReply,
icmpheader.TYPE_v4AddressMaskRequest, icmpheader.TYPE_v4AddressMaskReply]
+ list(range(30, 40)))
# values unassigned icmp types
DEFAULT_UNASSIGNED_TYPES = tuple([1, 2, 7, 40, 41] + list(range(19, 30)) +
list(range(44, 255)))
# all variants ipv4 network masks
IPV4_POSSIBLE_MASKS = (0, 2147483648, 3221225472, 3758096384,
4026531840, 4160749568, 4227858432, 4261412864,
4278190080, 4286578688, 4290772992, 4292870144,
4293918720, 4294443008, 4294705152, 4294836224,
4294901760, 4294934528, 4294950912, 4294959104,
4294963200, 4294965248, 4294966272, 4294966784,
4294967040, 4294967168, 4294967232, 4294967264,
4294967280, 4294967288, 4294967292, 4294967294,
4294967295)
def right_direction_vals_bytes(data: bytes, **kwargs)-> bool:
""" Function return cofficient right direction values bytes.
Right direction bytes is data[i] - data[i + 1] == 1
data[i] value less that data[i + 1] on 1
Example:
this_function(data = b'abcdefg') == True;
this_function(data = b'gfedcba') == False
Note: cff must be 0 < cff < 1
"""
start = kwargs.get("start", 0)
end = kwargs.get("end", len(data))
cff = kwargs.get("cff", 0.75)
if end > len(data) or start >= end:
raise ValueError(f"right_direction_bytes: Uncorrect end or start value!!!")
max_count = end - start - 1
if max_count == 0:
raise ValueError(f"right_direction_bytes: Uncorrect size data!!! Data must be more 1!!!")
count = 0
for i in range(start, end - 1):
if data[i + 1] - data[i] == 1:
count +=1
return count / max_count > cff
def left_direction_vals_bytes(data: bytes, **kwargs)-> bool:
""" Function return cofficient left direction values bytes
Left direction bytes is data[i + 1] - data[i] == 1,
data[i] value more that data[i + 1] on 1
Example:
this_function(data = b'abcdefg') == False;
this_function(data = b'gfedcba') == True
Note: cff must be 0 < cff < 1
"""
start = kwargs.get("start", 0)
end = kwargs.get("end", len(data))
cff = kwargs.get("cff", 0.75)
if end > len(data) or start >= end:
raise ValueError(f"Uncorrect end or start value!!!")
max_count = end - start - 1
if max_count == 0:
raise ValueError(f"right_direction_bytes: Uncorrect size data!!! Data must be more 1!!!")
count = 0
for i in range(start, end - 1):
if data[i] - data[i + 1] == 1:
count +=1
return count / max_count > cff
class ICMPAnalyzer:
def __init__(self, **kwargs):
"""
:param kwargs:
deprecated - list deprecated icmp types,
unassigned - list unassigned icmp types,
eps_encrypt - value epsilon for check encryption data;
coeff_bytes_direct - reference value probability for check direct values bytes
"""
self.deprecated_types = kwargs.get("deprecated", DEFAULT_DEPRECATED_TYPES)
self.unassigned_types = kwargs.get("unassigned", DEFAULT_UNASSIGNED_TYPES)
self.eps_encrypt = kwargs.get("eps_encrypt", 0.5)
self.cff_bdirect = kwargs.get("coeff_bytes_direct", 0.75)
def analyze(self, packet: bytes, offset = 0):
assert len(packet) - offset <= MAX_DATA_SIZE_v4ICMP + icmpheader.ICMPHeader.Length, "Too big size packet!!!"
assert len(packet) - offset >= icmpheader.ICMPHeader.Length, "Too little size packet!!!"
icmph = icmpheader.ICMPHeader()
icmph.read_bytes_from(packet, offset)
icmp_pid = 0
tunnelled = 0
pos_data = offset + icmph.Length
size_data = len(packet) - pos_data
if icmph.type in (icmpheader.TYPE_v4EchoRequest, icmpheader.TYPE_v4EchoReply):
icmp_pid = icmpheader.icmpv4_id(icmph)
if icmph.code != 0:
tunnelled = 1
else:
if size_data > 1:
if not right_direction_vals_bytes(packet, start=pos_data, cff=self.cff_bdirect) and \
not left_direction_vals_bytes(packet, start=pos_data, cff=self.cff_bdirect):
tunnelled = int(entropy.is_encrypted_data(packet,
start=pos_data, eps=self.eps_encrypt)) # check data encrypted?
elif icmph.type in (icmpheader.TYPE_v4TimestampRequest, icmpheader.TYPE_v4TimestampReply):
icmp_pid = icmpheader.icmpv4_id(icmph)
if size_data != 12 or icmph.code != 0:
tunnelled = 1
else:
if icmph.type == icmpheader.TYPE_v4TimestampRequest:
t1, t2, t3 = struct.unpack_from(">3I", packet, pos_data)
if t1 != t2 or t2 != t3 or t1 != t3:
tunnelled = 1
elif icmph.type in (icmpheader.TYPE_v4AddressMaskRequest, icmpheader.TYPE_v4AddressMaskReply):
icmp_pid = icmpheader.icmpv4_id(icmph)
if size_data != 4 or icmph.code != 0:
tunnelled = 1
else:
mask_addr = struct.unpack_from('>I', packet, pos_data)
if mask_addr not in IPV4_POSSIBLE_MASKS:
tunnelled = 1
elif icmph.type == icmpheader.TYPE_v4ExtendedEchoReply:
icmp_pid = icmpheader.icmpv4_id(icmph)
if size_data != 0 or icmph.code not in range(0, 5):
tunnelled = 1
elif icmph.type == icmpheader.TYPE_v4ExtendedEchoRequest:
icmp_pid = icmpheader.icmpv4_id(icmph)
L = struct.unpack_from('>B', icmph.other_bs, 3)[0] & 0b00000001
min_size = size_data
if min_size < icmpheader.ICMPExtHeader.Length or icmph.code != 0:
tunnelled = 1
else:
exth = icmpheader.ICMPExtHeader()
exth.read_bytes_from(packet, pos_data)
if exth.version != 2:
tunnelled = 1
else:
min_size -= icmpheader.ICMPExtHeader.Length
if min_size < icmpheader.ICMPExtObjHeader.Length:
tunnelled = 1
else:
exthobj = icmpheader.ICMPExtObjHeader()
exthobj.read_bytes_from(packet, offset + icmph.Length + exth.Length)
min_size -= exthobj.Length
if exthobj.cls_num != 3:
tunnelled = 1
else:
if exthobj.c_type == 1:
if L == 0:
tunnelled = 1
else:
ifname_len = exthobj.len - exthobj.Length
if ifname_len == 0:
tunnelled = 1
else:
if min_size < ifname_len:
tunnelled = 1
else:
tunnelled = int(entropy.is_encrypted_data(packet,
start= pos_data
+ exth.Length
+ exthobj.Length,
eps=self.eps_encrypt))
elif exthobj.c_type == 2:
if L == 0:
tunnelled = 1
else:
if exthobj.len != 4 + exthobj.Length:
tunnelled = 1
elif exthobj.c_type == 3:
if min_size < icmpheader.ICMPIntIdObjAddrHeader.Length:
tunnelled = 1
else:
id_obj_addrh = icmpheader.ICMPIntIdObjAddrHeader()
id_obj_addrh.read_bytes_from(packet,
pos_data + exth.Length + exthobj.Length)
if id_obj_addrh.addr_len == 0:
tunnelled = 1
else:
min_size -= id_obj_addrh.Length
loffset = pos_data + exth.Length + exthobj.Length + id_obj_addrh.Length
if min_size < id_obj_addrh.addr_len:
tunnelled = 1
else:
tunnelled = 1
elif icmph.type in (icmpheader.TYPE_v4Redirect, icmpheader.TYPE_v4SourceQuench):
if icmph.type == icmpheader.TYPE_v4SourceQuench:
codes = range(0, 1)
else:
codes = range(0, 4)
if size_data < MIN_DATA_SIZE_v4ICMPErrMsg or \
size_data > MAX_DATA_SIZE_v4ICMPErrMsg or icmph.code not in codes:
tunnelled = 1
else:
val = struct.unpack_from('>B', packet, pos_data)[0]
v = val >> 4
hl = (val & 0x0f) * 4
if v != 4 or (hl < ipv4header.IPv4Header.MinLength or hl > ipv4header.IPv4Header.MaxLength):
tunnelled = 1
else:
tunnelled = int(entropy.is_encrypted_data(packet, start=pos_data, eps=self.eps_encrypt))
elif icmph.type == icmpheader.TYPE_v4RouterAdvertisement:
if icmph.code != 0:
tunnelled = 1
else:
num_addr = struct.unpack_from('>B', packet, offset + 4)[0]
life_time = struct.unpack_from('>H', packet, offset + 6)[0]
addr_entry_size = struct.unpack_from('>B', packet, offset + 5)[0] * 4
if num_addr == 0 or life_time == 0 or num_addr * addr_entry_size != size_data:
tunnelled = 1
else:
tunnelled = int(entropy.is_encrypted_data(packet, start=pos_data, eps=self.eps_encrypt))
elif icmph.type in (icmpheader.TYPE_v4DestinationUnreachable,
icmpheader.TYPE_v4TimeExceeded, icmpheader.TYPE_v4SourceQuench,
icmpheader.TYPE_v4ParameterProblem):
if icmph.type == icmpheader.TYPE_v4DestinationUnreachable:
codes = range(0, 16)
elif icmph.type == icmpheader.TYPE_v4TimeExceeded:
codes = range(0, 2)
else:
# icmph.type == icmpheader.TYPE_v4ParameterProblem
codes = range(0, 3)
if size_data < MIN_DATA_SIZE_v4ICMPErrMsg or icmph.code not in codes:
tunnelled = 1
else:
val = struct.unpack_from('>B', packet, pos_data)[0]
v = val >> 4
hl = (val & 0x0f) * 4
if v != 4 or (hl < ipv4header.IPv4Header.MinLength or hl > ipv4header.IPv4Header.MaxLength):
tunnelled = 1
else:
length = struct.unpack_from('>B', packet, pos_data - 3)[0]
if length == 0:
tunnelled = int(entropy.is_encrypted_data(packet, start=pos_data, eps=self.eps_encrypt))
else:
length *= 4
length += 20
if length < 128 or size_data <= length + icmpheader.ICMPExtHeader.Length:
tunnelled = 1
else:
zcount = 0
i = pos_data + length - 1
while packet[i] == 0x00 and i >= pos_data + 20:
i -= 1
zcount += 1
e1 = entropy.is_encrypted_data(packet, start=pos_data, end=pos_data + length - zcount,
eps=self.eps_encrypt)
exthdr = icmpheader.ICMPExtHeader()
exthdr.read_bytes_from(packet, pos_data + length)
if exthdr.version == 2:
e2 = entropy.is_encrypted_data(packet,
start=pos_data + length + icmpheader.ICMPExtHeader.Length,
end=pos_data + size_data, eps=self.eps_encrypt)
else:
e2 = 1
tunnelled = int(e1 or e2)
if icmph.type in self.deprecated_types or icmph.type in self.unassigned_types:
tunnelled = 1
return icmp_pid, tunnelled