Add basic forwarding/multiplexing functionality

lib/proto/proto.ex

@@ -0,0 +1,155 @@
+defmodule Frajtano.Proto do
+  @agentc_request_identities 11
+  @agentc_sign_request 13
+  @agentc_remove_all_identities 19
+  @agentc_extension 27
+
+  @agent_failure 5
+  @agent_success 6
+  @agent_identities_answer 12
+  @agent_sign_response 14
+  @agent_extension_failure 28
+  @agent_extension_response 29
+
+  def encode({:agentc_request_identities, nil}),
+    do: encode_packet(@agentc_request_identities, <<>>)
+
+  def encode({:agentc_sign_request, {key, data, flags}}),
+    do:
+      encode_packet(
+        @agentc_sign_request,
+        <<byte_size(key)::big-integer-32, key::bytes, byte_size(data)::big-integer-32,
+          data::bytes, flags::big-integer-32>>
+      )
+
+  def encode({:agentc_remove_all_identities, nil}),
+    do: encode_packet(@agentc_remove_all_identities, <<>>)
+
+  def encode({:agentc_extension, {type, data}}),
+    do:
+      encode_packet(
+        @agentc_extension,
+        <<byte_size(type)::big-integer-32, type::bytes, data::bytes>>
+      )
+
+  def encode({:agent_failure, nil}), do: encode_packet(@agent_failure, <<>>)
+  def encode({:agent_success, nil}), do: encode_packet(@agent_success, <<>>)
+
+  def encode({:agent_identities_answer, keys}),
+    do:
+      encode_packet(
+        @agent_identities_answer,
+        <<length(keys)::big-integer-32,
+          keys
+          |> Enum.map_join(fn {key, comment} ->
+            <<
+              byte_size(key)::big-integer-32,
+              key::bytes,
+              byte_size(comment)::big-integer-32,
+              comment::bytes
+            >>
+          end)::bytes>>
+      )
+
+  def encode({:agent_sign_response, signature}),
+    do:
+      encode_packet(
+        @agent_sign_response,
+        <<byte_size(signature)::big-integer-32, signature::bytes>>
+      )
+
+  def encode({:agent_extension_failure, nil}),
+    do: encode_packet(@agent_extension_failure, <<>>)
+
+  def encode({:agent_extension_response, {type, data}}),
+    do:
+      encode_packet(
+        @agent_extension_response,
+        <<byte_size(type)::big-integer-32, type::bytes, data::bytes>>
+      )
+
+  defp encode_packet(type, contents),
+    do: <<byte_size(contents) + 1::big-integer-32, type::integer-8, contents::bytes>>
+
+  def decode(packet) do
+    case decode_packet(packet) do
+      {{@agentc_request_identities, contents}, rest} ->
+        {{:agentc_request_identities, decode_agentc_request_identities(contents)}, rest}
+
+      {{@agentc_sign_request, contents}, rest} ->
+        {{:agentc_sign_request, decode_agentc_sign_request(contents)}, rest}
+
+      {{@agentc_remove_all_identities, contents}, rest} ->
+        {{:agentc_remove_all_identities, decode_agentc_remove_all_identities(contents)}, rest}
+
+      {{@agentc_extension, contents}, rest} ->
+        {{:agentc_extension, decode_agentc_extension(contents)}, rest}
+
+      {{@agent_failure, contents}, rest} ->
+        {{:agent_failure, decode_agent_failure(contents)}, rest}
+
+      {{@agent_success, contents}, rest} ->
+        {{:agent_success, decode_agent_success(contents)}, rest}
+
+      {{@agent_identities_answer, contents}, rest} ->
+        {{:agent_identities_answer, decode_agent_identities_answer(contents)}, rest}
+
+      {{@agent_sign_response, contents}, rest} ->
+        {{:agent_sign_response, decode_agent_sign_response(contents)}, rest}
+
+      {{@agent_extension_failure, contents}, rest} ->
+        {{:agent_extension_failure, decode_agent_extension_failure(contents)}, rest}
+
+      {{@agent_extension_response, contents}, rest} ->
+        {{:agent_extension_response, decode_agent_extension_response(contents)}, rest}
+
+      {nil, rest} ->
+        {nil, rest}
+    end
+  end
+
+  defp decode_packet(
+         <<length::big-integer-32, type::integer-8, contents::bytes-size(length - 1),
+           rest::bytes>>
+       ),
+       do: {{type, contents}, rest}
+
+  defp decode_packet(rest), do: {nil, rest}
+
+  defp decode_agentc_request_identities(<<>>), do: nil
+
+  defp decode_agentc_sign_request(
+         <<keylen::big-integer-32, key::bytes-size(keylen), datalen::big-integer-32,
+           data::bytes-size(datalen), flags::big-integer-32>>
+       ),
+       do: {key, data, flags}
+
+  defp decode_agentc_remove_all_identities(<<>>), do: nil
+
+  defp decode_agentc_extension(
+         <<tylen::big-integer-32, type::bytes-size(tylen), contents::bytes>>
+       ),
+       do: {type, contents}
+
+  defp decode_agent_failure(<<>>), do: nil
+  defp decode_agent_success(<<>>), do: nil
+
+  defp decode_agent_identities_answer(<<nkeys::big-integer-32, keys::bytes>>) do
+    lst =
+      for <<keylen::big-integer-32, key::bytes-size(keylen), commentlen::big-integer-32,
+            comment::bytes-size(commentlen) <- keys>>,
+          do: {key, comment}
+
+    ^nkeys = length(lst)
+    lst
+  end
+
+  defp decode_agent_sign_response(<<len::big-integer-32, sig::bytes-size(len)>>), do: sig
+
+  defp decode_agent_extension_failure(<<>>), do: nil
+
+  defp decode_agent_extension_response(
+         <<tylen::big-integer-32, type::bytes-size(tylen), contents::bytes>>
+       ),
+       do: {type, contents}
+end