1 files changed, 165 insertions, 46 deletions
diff --git a/shard/lib/net/tcpconn.ex b/shard/lib/net/tcpconn.ex
index 543341a..35bf9d1 100644
--- a/shard/lib/net/tcpconn.ex
+++ b/shard/lib/net/tcpconn.ex
@@ -1,7 +1,15 @@
 defmodule SNet.TCPConn do
+  @moduledoc"""
+  Secret handshake as described in this document:
+  https://ssbc.github.io/scuttlebutt-protocol-guide/#peer-connections
+
+  Does not implement the stream protocol, we don't hide the length of packets.
+  (TODO ^)
+  """
+
+
   use GenServer, restart: :temporary
-  require Salty.Box.Curve25519xchacha20poly1305, as: Box
-  require Salty.Sign.Ed25519, as: Sign
+
   require Logger
 
   def start_link(state) do
@@ -9,60 +17,166 @@ defmodule SNet.TCPConn do
   end
 
   def init(state) do
-    GenServer.cast(self(), :handshake)
-  	{:ok, state}
-  end
+    if state.is_client do
+      GenServer.cast(self(), :client_handshake)
+    else
+      GenServer.cast(self(), :server_handshake)
+    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}
+    {:ok, {addr, port}} = :inet.peername state.socket
+    {:ok, %{state | addr: addr, port: port}}
   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
+  def handle_call(:get_peer_info, _from, state) do
+    {:reply, {:tcp4, state.addr, state.port}, state}
+  end
 
-    # 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)
+  def handle_cast(:client_handshake, state) do
+    socket = state.socket
 
-    {: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)
+    net_key = Application.get_env(:shard, :network_key)
+    {:ok, cli_eph_pk, cli_eph_sk} = :enacl.box_keypair
+
+    [srv_longterm_pk] = state.his_auth
+    cli_longterm_pk = state.my_auth
+    cli_longterm_sk = Keys.get_sk cli_longterm_pk
+
+    # 1. Client hello
+    {:ok, cli_hello_hmac} = :enacl.auth(cli_eph_pk, net_key)
+    cli_hello = cli_hello_hmac <> cli_eph_pk
+    :gen_tcp.send(socket, cli_hello)
+
+    # 2. Server hello
+    {:ok, srv_hello} = :gen_tcp.recv(socket, 0)
+    64 = byte_size srv_hello
+    srv_hmac = :binary.part srv_hello, 0, 32
+    srv_eph_pk = :binary.part srv_hello, 32, 32
+    true = :enacl.auth_verify(srv_hmac, srv_eph_pk, net_key)
+
+    # Shared secret derivation
+    sh_sec_ab = :enacl.curve25519_scalarmult(cli_eph_sk, srv_eph_pk)
+    sh_sec_aB = :enacl.curve25519_scalarmult(cli_eph_sk, :enacl.crypto_sign_ed25519_public_to_curve25519(srv_longterm_pk))
+
+    # 3. Client authenticate
+    msg1 = net_key <> srv_longterm_pk <> :crypto.hash(:sha256, sh_sec_ab)
+    det_sign_A = :enacl.sign_detached(msg1, cli_longterm_sk)
+    key3 = :crypto.hash(:sha256, net_key <> sh_sec_ab <> sh_sec_aB)
+    cli_auth = :crypto.secretbox(det_sign_A <> cli_longterm_pk, <<0 :: 24*8>>, key3)
+    :gen_tcp.send(socket, cli_auth)
+
+    # Shared secret derivation, again
+    sh_sec_Ab = :enacl.curve25519_scalarmult(:enacl.crypto_sign_ed25519_secret_to_curve25519(cli_longterm_sk), srv_eph_pk)
+
+    # 4. Server accept
+    {:ok, srv_accept} = :gen_tcp.recv(socket, 0)
+    key4 = :crypto.hash(:sha256, net_key <> sh_sec_ab <> sh_sec_aB <> sh_sec_Ab)
+    {:ok, det_sign_B} = :enacl.secretbox_open(srv_accept, <<0 :: 24*8>>, key4)
+    true = :enacl.sign_verify_detached(det_sign_B, net_key <> det_sign_A <> cli_longterm_pk <> :crypto.sha256(sh_sec_ab), srv_longterm_pk)
+
+    # Derive secrets and initial nonces for stream communication
+    secret_common = :crypto.hash(:sha256, :crypto.hash(:sha256, net_key <> sh_sec_ab <> sh_sec_aB <> sh_sec_Ab))
+    secret_cli2srv = :crypto.hash(:sha256, secret_common <> srv_longterm_pk)
+    secret_srv2cli = :crypto.hash(:sha256, secret_common <> cli_longterm_pk)
+    {:ok, hmac1} = :enacl.auth(srv_eph_pk, net_key)
+    nonce_cli2srv = :binary.part(hmac1, 0, 24)
+    {:ok, hmac2} = :enacl.auth(cli_eph_pk, net_key)
+    nonce_srv2cli = :binary.part(hmac2, 0, 24)
+
+    # Set up the rest
+    :inet.setopts(socket, [active: true])
+    {:ok, {addr, port}} = :inet.peername socket
+    state = %{
+      socket: socket,
+      my_pk: cli_longterm_pk,
+      his_pk: srv_longterm_pk,
+      secret_send: secret_cli2srv,
+      secret_recv: secret_srv2cli,
+      nonce_send: nonce_cli2srv,
+      nonce_recv: nonce_srv2cli,
+      addr: addr,
+      port: port,
+      # his_port: his_port
+    }
+
+    GenServer.cast(Shard.Manager, {:peer_up, state.his_pk, self(), addr, port})
+    Logger.info "New peer: #{print_id state} at #{inspect addr}:#{port}"
 
-    expected_suffix = Application.get_env(:shard, :peer_id_suffix)
-    len = byte_size(expected_suffix)
-    ^len = :binary.longest_common_suffix([cli_pkey, expected_suffix])
+    {:noreply, state}
+  end
 
-    if srv_pkey == cli_pkey do
-      exit :normal
-    end
+  def handle_cast(:server_handshake, state) do
+    socket = state.socket
 
-    # Connected
+    net_key = Application.get_env(:shard, :network_key)
+    {:ok, srv_eph_pk, srv_eph_sk} = :enacl.box_keypair
+
+    srv_longterm_pk = state.my_auth
+    srv_longterm_sk = Keys.get_sk srv_longterm_pk
+
+    # 1. Client hello
+    {:ok, cli_hello} = :gen_tcp.recv(socket, 0)
+    64 = byte_size cli_hello
+    cli_hmac = :binary.part cli_hello, 0, 32
+    cli_eph_pk = :binary.part cli_hello, 32, 32
+    true = :enacl.auth_verify(cli_hmac, cli_eph_pk, net_key)
+
+    # 2. Server hello
+    {:ok, srv_hello_hmac} = :enacl.auth(srv_eph_pk, net_key)
+    srv_hello = srv_hello_hmac <> srv_eph_pk
+    :gen_tcp.send(socket, srv_hello)
+
+    # Shared secret derivation
+    sh_sec_ab = :enacl.curve25519_scalarmult(srv_eph_sk, cli_eph_pk)
+    sh_sec_aB = :enacl.curve25519_scalarmult(:enacl.crypto_sign_ed25519_secret_to_curve25519(srv_longterm_sk), cli_eph_pk)
+
+    # 3. Client authenticate
+    {:ok, cli_auth} = :gen_tcp.recv(socket, 0)
+    key3 = :crypto.hash(:sha256, net_key <> sh_sec_ab <> sh_sec_aB)
+    {:ok, cli_auth_plain} = :enacl.secretbox_open(cli_auth, <<0 :: 24*8>>, key3)
+    96 = byte_size cli_auth_plain
+    det_sign_A = :binary.part(cli_auth_plain, 0, 64)
+    cli_longterm_pk = :binary.part(cli_auth_plain, 64, 32)
+    true = :enacl.sign_verify_deteached(det_sign_A, net_key <> srv_longterm_pk <> :crypto.hash(:sha256, sh_sec_ab), cli_longterm_pk)
+
+    # Shared secret derivation
+    sh_sec_Ab = :enacl.curve25519_scalarmult(srv_eph_sk, :enacl.crypto_sign_ed25519_public_to_curve25519(cli_longterm_pk))
+
+    # TODO: here we can stop if we don't like the client's longterm pk
+
+    # 4. Server accept
+    det_sign_B = :enacl.sign_detached(net_key <> det_sign_A <> cli_longterm_pk <> :crypto.hash(:sha256, sh_sec_ab), srv_longterm_sk)
+    key4 = :crypto.hash(:sha256, net_key <> sh_sec_ab <> sh_sec_aB <> sh_sec_Ab)
+    msg4 = :enacl.secretbox(det_sign_B, <<0 :: 24*8>>, key4)
+    :gen_tcp.send(socket, msg4)
+
+    # Derive secrets and initial nonces for stream communication
+    secret_common = :crypto.hash(:sha256, :crypto.hash(:sha256, net_key <> sh_sec_ab <> sh_sec_aB <> sh_sec_Ab))
+    secret_cli2srv = :crypto.hash(:sha256, secret_common <> srv_longterm_pk)
+    secret_srv2cli = :crypto.hash(:sha256, secret_common <> cli_longterm_pk)
+    {:ok, hmac1} = :enacl.auth(srv_eph_pk, net_key)
+    nonce_cli2srv = :binary.part(hmac1, 0, 24)
+    {:ok, hmac2} = :enacl.auth(cli_eph_pk, net_key)
+    nonce_srv2cli = :binary.part(hmac2, 0, 24)
+
+    # Set up the rest
     :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})
+    state = %{
+      socket: socket,
+      my_pk: cli_longterm_pk,
+      his_pk: srv_longterm_pk,
+      secret_send: secret_srv2cli,
+      secret_recv: secret_cli2srv,
+      nonce_send: nonce_srv2cli,
+      nonce_recv: nonce_cli2srv,
+      addr: addr,
+      port: port,
+      # his_port: his_port
+    }
+
+    GenServer.cast(Shard.Manager, {:peer_up, state.his_pk, self(), addr, port})
     Logger.info "New peer: #{print_id state} at #{inspect addr}:#{port}"
 
     {:noreply, state}
@@ -75,6 +189,11 @@ defmodule SNet.TCPConn do
     {:noreply, state}
   end
 
+  defp next_nonce(nonce) do
+    i = :crypto.bytes_to_integer(nonce)
+    <<i+1 :: 24*8>>
+  end
+
   defp encode_pkt(pkt, pk, sk) do
     {:ok, n} = Salty.Random.buf Box.noncebytes
     {:ok, msg} = Box.easy(pkt, n, pk, sk)
@@ -91,7 +210,7 @@ defmodule SNet.TCPConn do
   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)
+    Shard.Manager.incoming(state.his_pkey, msg_data)
     {:noreply, state}
   end
 
@@ -102,7 +221,7 @@ defmodule SNet.TCPConn do
   end
 
   defp print_id(state) do
-    state.his_pkey
+    state.his_pk
     |> binary_part(0, 8)
     |> Base.encode16
     |> String.downcase