import random
import copy
# information taken from https://www.cymru.com/jtk/misc/ephemeralports.html
class PortRanges:
# dynamic ports as listed by RFC 6056
DYNAMIC_PORTS = range(49152, 65536)
LINUX = range(32768, 61001)
FREEBSD = range(10000, 65536)
APPLE_IOS = DYNAMIC_PORTS
APPLE_OSX = DYNAMIC_PORTS
WINDOWS_7 = DYNAMIC_PORTS
WINDOWS_8 = DYNAMIC_PORTS
WINDOWS_VISTA = DYNAMIC_PORTS
WINDOWS_XP = range(1024, 5001)
# This class uses classes instead of functions so deepcloning works
class PortSelectionStrategy:
class sequential:
def __init__(self):
self.counter = -1
# that function will always return a one higher counter than before,
# restarting from the start once it reached the highest value
def __call__(self, port_range, *args):
if self.counter == -1:
self.counter = port_range.start
port = self.counter
self.counter += 1
if self.counter == port_range.stop:
self.counter = port_range.start
return port
class random:
def __call__(self, port_range, *args):
return random.randrange(port_range.start, port_range.stop)
class linux_kernel:
"""
A port-selection-strategy oriented on the linux-kernel
The implementation follows https://github.com/torvalds/linux/blob/master/net/ipv4/inet_connection_sock.c#L173
as much as possible when converting from one language to another (The newest file was used
by the time of writing, make sure you select the correct one when following the link!)
"""
def __call__(self, port_range: range, port_selector, *args):
"""
This method is an attempt to map a c-function to python. To solve the goto-problem
while-true's have been added. Both of the while-true's are placed where the original
had a label to jump to. break's and continue's are set to preserve the original
control flow. Another method could have been used to rewrite the c-code, however this
was chosen to preserve the similarity between this and the original
:param port_range: the port range to choose from
:param port_selector: the port selector that tells which ports are in use
:param args: Not used for now
:return: A port number
"""
low, high = port_range.start, port_range.stop
# this var tells us if we should use the upper or lower port-range-half, or the whole range if
# this var is None. The original was an enum of the values 0, 1 and 2. But I think an Optional[bool]
# is more clear
# None: use whole range, True: use lower half, False: use upper half
attempt_half = True
high += 1 # line 186 in the original file
while True:
if high - low < 4:
attempt_half = None
if attempt_half is not None:
# apparently a fast method to find a number close to the real half
# unless the difference between high and low is 4 (see above, note the 2-shift below)
# this does not work
half = low + (((high - low) >> 2) << 1)
if attempt_half:
high = half
else:
low = half
remaining = high - low
if remaining > 1:
remaining &= ~1 # flip the 1-bit
offset = random.randrange(0, remaining)
offset |= 1
attempt_half_before = attempt_half # slight hack to keep track of change
while True:
port = low + offset
for i in range(0, remaining, 2):
if port >= high:
port -= remaining
if port_selector.is_port_in_use(port):
port += 2
continue
return port
offset -= 1
if not (offset & 1):
continue
if attempt_half:
attempt_half = False
break
if attempt_half_before: # we still got ports to search, attemp_half was just set to False
continue
if not attempt_half: # the port-range is exhausted
break
raise ValueError("Could not find suitable port")
class PortSelector:
"""
This class simulates a port-selection-process. Instances keep a list of port-numbers they generated so
the same port-number will not be generated again.
"""
def __init__(self, port_range, select_function):
"""
Create a PortSelector given a range of ports to choose from and a function that chooses the next port
:param port_range: a range-object containing the range of ports to choose from
:param select_function: a function that receives the port_range and selects a port
"""
if len(port_range) == 0:
raise ValueError("cannot choose from an empty range")
if port_range.start not in range(1, 65536) or port_range.stop not in range(1, 65536 + 1):
raise ValueError("port_range is no subset of the valid port-range")
self.port_range = port_range
self._select_port = select_function
self.generated = []
def select_port(self):
# do this check to avoid endless loops
if len(self.generated) == len(self.port_range):
raise RuntimeError("All %i port numbers were already generated, no more can be generated"
% len(self.port_range))
while True:
port = self._select_port(self.port_range, self)
if port not in self.generated:
self.generated.append(port)
return port
def is_port_in_use(self, port: int):
return port in self.generated
def undo_port_use(self, port: int):
if port in self.generated:
self.generated.remove(port)
else:
raise ValueError("Port %i is not in use and thus can not be undone" % port)
def reduce_size(self, size: int):
"""
Reduce the list of already generated ports to the last <size> generated.
If size if bigger than the number of generated ports nothing happens.
"""
self.generated = self.generated[-size:]
def clear(self):
"""
Clear the list of generated ports. As of now this does not reset the state of the selection-function
"""
self.generated = []
def clone(self):
return copy.deepcopy(self)
class ProtocolPortSelector:
"""
This class contains a method to select ports for udp and tcp. It generally consists of the port-selectors, one
for tcp and one for udp. For convenience this class has a __getattr__-method to call methods on both selectors
at once. E.g, clear() does not exist for ProtocolPortSelector but it does for PortSelector, therefore
protocolPortSelector.clear() will call clear for both port-selectors.
"""
def __init__(self, port_range, select_tcp, select_udp=None):
self.tcp = PortSelector(port_range, select_tcp)
self.udp = PortSelector(port_range, select_udp or select_tcp)
def get_tcp_generator(self):
return self.tcp
def get_udp_generator(self):
return self.udp
def select_port_tcp(self):
return self.tcp.select_port()
def select_port_udp(self):
return self.udp.select_port()
def is_port_in_use_tcp(self, port):
return self.tcp.is_port_in_use(port)
def is_port_in_use_udp(self, port):
return self.udp.is_port_in_use(port)
def clone(self):
class Tmp:
pass
clone = Tmp()
clone.__class__ = type(self)
clone.udp = self.udp.clone()
clone.tcp = self.tcp.clone()
return clone
def __getattr__(self, attr):
val = getattr(self.tcp, attr)
if callable(val): # we proprably got a method here
tcp_meth = val
udp_meth = getattr(self.udp, attr)
def double_method(*args, **kwargs):
return tcp_meth(*args, **kwargs), udp_meth(*args, **kwargs)
return double_method # calling this function will call the method for both port-selectors
else: # we have found a simple value, return a tuple containing the attribute-value from both port-selectors
return val, getattr(self.udp, attr)
class PortSelectors:
"""
To save some time this class contains some of the port-selection-strategies found in the wild. It is recommended
to use .clone() to get your personal copy, otherwise two parts of your code might select ports on the same
port-selector which is something you might want to avoid.
"""
LINUX = ProtocolPortSelector(PortRanges.LINUX, PortSelectionStrategy.random())
APPLE = ProtocolPortSelector(PortRanges.DYNAMIC_PORTS,
PortSelectionStrategy.sequential(),
PortSelectionStrategy.random())
FREEBSD = ProtocolPortSelector(PortRanges.FREEBSD, PortSelectionStrategy.random())
# the selection strategy is a guess as i can't find more info on it
WINDOWS = ProtocolPortSelector(PortRanges.WINDOWS_7, PortSelectionStrategy.random())