defmodule SNet.TCPConn do
use GenServer, restart: :temporary
require Salty.Box.Curve25519xchacha20poly1305, as: Box
require Salty.Sign.Ed25519, as: Sign
require Logger
def start_link(state) do
GenServer.start_link(__MODULE__, state)
end
def init(state) do
GenServer.cast(self(), :handshake)
{:ok, state}
end
def handle_call(:get_host_str, _from, state) do
{:reply, "#{state.his_pkey|>Base.encode16|>String.downcase}@#{to_string(:inet_parse.ntoa(state.addr))}:#{state.port}", state}
end
def handle_cast(:handshake, state) do
socket = state.socket
{srv_pkey, srv_skey} = Shard.Keys.get_peer_keypair
{:ok, sess_pkey, sess_skey} = Box.keypair
{:ok, challenge} = Salty.Random.buf 32
# Exchange public keys and challenge
hello = {srv_pkey, sess_pkey, challenge, state.my_port}
:gen_tcp.send(socket, :erlang.term_to_binary hello)
{:ok, pkt} = :gen_tcp.recv(socket, 0)
{cli_pkey, cli_sess_pkey, cli_challenge, his_port} = :erlang.binary_to_term(pkt, [:safe])
# Do challenge and check their challenge
{:ok, cli_challenge_sign} = Sign.sign_detached(cli_challenge, srv_skey)
pkt = encode_pkt(cli_challenge_sign, cli_sess_pkey, sess_skey)
:gen_tcp.send(socket, pkt)
{:ok, pkt} = :gen_tcp.recv(socket, 0)
challenge_sign = decode_pkt(pkt, cli_sess_pkey, sess_skey)
:ok = Sign.verify_detached(challenge_sign, challenge, cli_pkey)
expected_suffix = Application.get_env(:shard, :peer_id_suffix)
len = byte_size(expected_suffix)
^len = :binary.longest_common_suffix([cli_pkey, expected_suffix])
if srv_pkey == cli_pkey do
exit :normal
end
# Connected
:inet.setopts(socket, [active: true])
{:ok, {addr, port}} = :inet.peername socket
state =%{ socket: socket,
my_pkey: srv_pkey,
my_skey: srv_skey,
his_pkey: cli_pkey,
conn_my_pkey: sess_pkey,
conn_my_skey: sess_skey,
conn_his_pkey: cli_sess_pkey,
addr: addr,
port: port,
his_port: his_port
}
GenServer.cast(Shard.Manager, {:peer_up, cli_pkey, self(), addr, his_port})
Logger.info "New peer: #{print_id state} at #{inspect addr}:#{port}"
{:noreply, state}
end
def handle_cast({:send_msg, msg}, state) do
msgbin = :erlang.term_to_binary msg
enc = encode_pkt(msgbin, state.conn_his_pkey, state.conn_my_skey)
:gen_tcp.send(state.socket, enc)
{:noreply, state}
end
defp encode_pkt(pkt, pk, sk) do
{:ok, n} = Salty.Random.buf Box.noncebytes
{:ok, msg} = Box.easy(pkt, n, pk, sk)
n <> msg
end
defp decode_pkt(pkt, pk, sk) do
n = binary_part(pkt, 0, Box.noncebytes)
enc = binary_part(pkt, Box.noncebytes, (byte_size pkt) - Box.noncebytes)
{:ok, msg} = Box.open_easy(enc, n, pk, sk)
msg
end
def handle_info({:tcp, _socket, raw_data}, state) do
msg = decode_pkt(raw_data, state.conn_his_pkey, state.conn_my_skey)
msg_data = :erlang.binary_to_term(msg, [:safe])
Shard.Manager.dispatch(state.his_pkey, msg_data)
{:noreply, state}
end
def handle_info({:tcp_closed, _socket}, state) do
Logger.info "Disconnected: #{print_id state} at #{inspect state.addr}:#{state.port}"
GenServer.cast(Shard.Manager, {:peer_down, state.his_pkey, state.addr, state.his_port})
exit(:normal)
end
defp print_id(state) do
state.his_pkey
|> binary_part(0, 8)
|> Base.encode16
|> String.downcase
end
end
