walkingonions/client.py

#!/usr/bin/env python3

import random # For simulation, not cryptography!
import math

import network
import dirauth
import relay

class CellClient(relay.CellHandler):
    """The subclass of CellHandler for clients."""

    def __init__(self, myaddr, dirauthaddrs):
        super().__init__(myaddr, dirauthaddrs)
        self.guardaddr = None
        self.consensus_cdf = [0]

    def get_consensus_from_fallbackrelay(self):
        """Download a fresh consensus from a random fallbackrelay."""
        fb = random.choice(network.thenetwork.getfallbackrelays())
        self.send_msg(relay.RelayGetConsensusMsg(), fb.netaddr)

    def ensure_guard_vanilla(self):
        """Ensure that we have a channel to a guard (Vanilla Onion
        Routing version)."""
        while True:
            if self.guardaddr is None:
                # Pick a guard from the consensus
                guard = self.consensus.select_weighted_relay(self.consensus_cdf)
                self.guardaddr = guard.descdict['addr']

            # Connect to the guard
            try:
                self.get_channel_to(self.guardaddr)
            except network.NetNoServer:
                # Our guard is gone
                self.guardaddr = None

            if self.guardaddr is not None:
                break

        print('chose guard=', self.guardaddr)

    def ensure_guard(self):
        """Ensure that we have a channel to a guard."""
        if network.thenetwork.womode == network.WOMode.VANILLA:
            self.ensure_guard_vanilla()

    def received_msg(self, msg, peeraddr, peer):
        """Callback when a NetMsg not specific to a circuit is
        received."""
        print("Client %s received msg %s from %s" % (self.myaddr, msg, peeraddr))
        if isinstance(msg, relay.RelayConsensusMsg):
            self.consensus = msg.consensus
            dirauth.verify_consensus(self.consensus, network.thenetwork.dirauthkeys())
            self.consensus_cdf = self.consensus.bw_cdf()
        else:
            return super().received_msg(msg, peeraddr, peer)

    def received_cell(self, circid, cell, peeraddr, peer):
        """Callback with a circuit-specific cell is received."""
        print("Client %s received cell on circ %d: %s from %s" % (self.myaddr, circid, cell, peeraddr))
        return super().received_cell(circid, cell, peeraddr, peer)


class Client:
    """A class representing a Tor client."""

    def __init__(self, dirauthaddrs):
        # Get a network address for client-side use only (do not bind it
        # to the network)
        self.netaddr = network.NetAddr()
        self.cellhandler = CellClient(self.netaddr, dirauthaddrs)

        # Register for epoch tick notifications
        network.thenetwork.wantepochticks(self, True)

    def terminate(self):
        """Quit this client."""

        # Stop listening for epoch ticks
        network.thenetwork.wantepochticks(self, False)

        # Close relay connections
        self.cellhandler.terminate()

    def get_consensus(self):
        """Fetch a new consensus."""

        # We're going to want a new consensus from our guard.  In order
        # to get that, we'll need a channel to our guard.  In order to
        # get that, we'll need a guard address.  In order to get that,
        # we'll need a consensus (uh, oh; in that case, fetch the
        # consensus from a fallback relay).

        self.cellhandler.get_consensus_from_fallbackrelay()
        print('client consensus=', self.cellhandler.consensus)

    def newepoch(self, epoch):
        """Callback that fires at the start of each epoch"""

        # We'll need a new consensus
        self.get_consensus()

        # If we don't have a guard, pick one and make a channel to it
        self.cellhandler.ensure_guard()



if __name__ == '__main__':
    # Start some dirauths
    numdirauths = 9
    dirauthaddrs = []
    for i in range(numdirauths):
        dira = dirauth.DirAuth(i, numdirauths)
        dirauthaddrs.append(network.thenetwork.bind(dira))

    # Start some relays
    numrelays = 10
    relays = []
    for i in range(numrelays):
        # Relay bandwidths (at least the ones fast enough to get used)
        # in the live Tor network (as of Dec 2019) are well approximated
        # by (200000-(200000-25000)/3*log10(x)) where x is a
        # uniform integer in [1,2500]
        x = random.randint(1,2500)
        bw = int(200000-(200000-25000)/3*math.log10(x))
        relays.append(relay.Relay(dirauthaddrs, bw, 0))

    # The fallback relays are a hardcoded list of about 5% of the
    # relays, used by clients for bootstrapping
    numfallbackrelays = int(numrelays * 0.05) + 1
    fallbackrelays = random.sample(relays, numfallbackrelays)
    for r in fallbackrelays:
        r.set_is_fallbackrelay()
    network.thenetwork.setfallbackrelays(fallbackrelays)

    # Tick the epoch
    network.thenetwork.nextepoch()

    dirauth.verify_consensus(dirauth.DirAuth.consensus, network.thenetwork.dirauthkeys())

    print('ticked; epoch=', network.thenetwork.getepoch())

    relays[3].cellhandler.send_msg(relay.RelayRandomHopMsg(30), relays[5].netaddr)

    # See what channels exist and do a consistency check
    for r in relays:
        print("%s: %s" % (r.netaddr, [ str(k) for k in r.cellhandler.channels.keys()]))
        raddr = r.netaddr
        for ad, ch in r.cellhandler.channels.items():
            if ch.peer.cellhandler.myaddr != ad:
                print('address mismatch:', raddr, ad, ch.peer.cellhandler.myaddr)

            if ch.peer.cellhandler.channels[raddr].peer is not ch:
                print('asymmetry:', raddr, ad, ch, ch.peer.cellhandler.channels[raddr].peer)

    # Start some clients
    numclients = 1
    clients = []
    for i in range(numclients):
        clients.append(Client(dirauthaddrs))

    # Tick the epoch
    network.thenetwork.nextepoch()

    # See what channels exist and do a consistency check
    for c in clients:
        print("%s: %s" % (c.netaddr, [ str(k) for k in c.cellhandler.channels.keys()]))
        caddr = c.netaddr
        for ad, ch in c.cellhandler.channels.items():
            if ch.peer.cellhandler.myaddr != ad:
                print('address mismatch:', caddr, ad, ch.peer.cellhandler.myaddr)

            if ch.peer.cellhandler.channels[caddr].peer is not ch:
                print('asymmetry:', caddr, ad, ch, ch.peer.cellhandler.channels[caddr].peer)

    relays[3].terminate()
    del relays[3]

    # Tick the epoch
    network.thenetwork.nextepoch()

    # See what channels exist and do a consistency check
    for c in clients:
        print("%s: %s" % (c.netaddr, [ str(k) for k in c.cellhandler.channels.keys()]))
        caddr = c.netaddr
        for ad, ch in c.cellhandler.channels.items():
            if ch.peer.cellhandler.myaddr != ad:
                print('address mismatch:', caddr, ad, ch.peer.cellhandler.myaddr)

            if ch.peer.cellhandler.channels[caddr].peer is not ch:
                print('asymmetry:', caddr, ad, ch, ch.peer.cellhandler.channels[caddr].peer)