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|
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.Identity.get_keypair
{:ok, sess_pkey, sess_skey} = Box.keypair
{:ok, challenge} = Salty.Random.buf 32
# Exchange public keys and challenge
:gen_tcp.send(socket, srv_pkey <> sess_pkey <> challenge)
{:ok, pkt} = :gen_tcp.recv(socket, 0)
cli_pkey = binary_part(pkt, 0, Sign.publickeybytes)
cli_sess_pkey = binary_part(pkt, Sign.publickeybytes, Box.publickeybytes)
cli_challenge = binary_part(pkt, Sign.publickeybytes + Box.publickeybytes, 32)
# 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)
# 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
}
Logger.info "New peer: #{print_id state} at #{inspect addr}:#{port}"
GenServer.cast(self(), :init_push)
{:noreply, state}
end
def handle_cast({:send_msg, msg}, state) do
send_msg(state, msg)
{:noreply, state}
end
def handle_cast(:init_push, state) do
push_messages(state, nil, 10)
{: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
defp send_msg(state, msg) 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)
end
def handle_info({:tcp, _socket, raw_data}, state) do
msg = decode_pkt(raw_data, state.conn_his_pkey, state.conn_my_skey)
handle_packet(:erlang.binary_to_term(msg, [:safe]), state)
{:noreply, state}
end
def handle_info({:tcp_closed, _socket}, state) do
Logger.info "Disconnected: #{print_id state} at #{inspect state.addr}:#{state.port}"
exit(:normal)
end
defp push_messages(state, start, num) do
case GenServer.call(SApp.Chat.Log, {:read, start, num}) do
{:ok, list, rest} ->
send_msg(state, {:info, start, list, rest})
_ -> nil
end
end
defp handle_packet(msg, state) do
# Logger.info "Message: #{inspect msg}"
case msg do
:get_top -> push_messages(state, nil, 10)
{:get, start} -> push_messages(state, start, 20)
{:info, _start, list, rest} ->
if rest != nil and not GenServer.call(SApp.Chat.Log, {:has, rest}) do
send_msg(state, {:get, rest})
end
spawn_link(fn ->
Process.sleep 1000
GenServer.cast(SApp.Chat.Log, {:insert_many, list, &SApp.Chat.msg_callback/1})
end)
end
end
defp print_id(state) do
state.his_pkey
|> binary_part(0, 8)
|> Base.encode16
|> String.downcase
end
end
|
