Added IP-based rate limiting for Copi (fixes #1877)

copi.owasp.org/SECURITY.md

@@ -0,0 +1,37 @@
+# Security Policy for Copi
+
+## Rate Limiting
+
+Copi implements IP-based rate limiting to protect against CAPEC-212 (Functionality Misuse) attacks and ensure service availability.
+
+## Protected Actions
+
+1. **Game Creation**: Limited to prevent abuse
+   - Default: 10 games per IP per hour
+   - Configurable via `MAX_GAMES_PER_IP` and `GAME_CREATION_WINDOW_SECONDS`
+
+2. **Player Creation**: Separate limit from game creation
+   - Default: 20 players per IP per hour
+   - Configurable via `MAX_PLAYERS_PER_IP` and `PLAYER_CREATION_WINDOW_SECONDS`
+
+3. **WebSocket Connections**: Prevents connection flooding
+   - Default: 50 connections per IP per 5 minutes
+   - Configurable via `MAX_CONNECTIONS_PER_IP` and `CONNECTION_WINDOW_SECONDS`
+
+## Configuration
+
+All limits can be adjusted via environment variables in production:
+
+```bash
+MAX_GAMES_PER_IP=10
+GAME_CREATION_WINDOW_SECONDS=3600
+MAX_PLAYERS_PER_IP=20
+PLAYER_CREATION_WINDOW_SECONDS=3600
+MAX_CONNECTIONS_PER_IP=50
+CONNECTION_WINDOW_SECONDS=300
+```
+
+### Reporting Security Issues
+
+If you discover a security vulnerability, please email [email protected] with details.
+Do not create public GitHub issues for security problems.

copi.owasp.org/config/runtime.exs

@@ -119,3 +119,35 @@ if config_env() == :prod do
   #
   # See https://hexdocs.pm/swoosh/Swoosh.html#module-installation for details.
 end
+
+# Rate Limiter Configuration (runtime - can be changed via environment variables)
+env_integer = fn var, default ->
+  case System.get_env(var) do
+    nil ->
+      default
+
+    value ->
+      case Integer.parse(value) do
+        {int, ""} ->
+          int
+
+        _ ->
+          raise ArgumentError,
+                "environment variable #{var} must be an integer, got: #{inspect(value)}"
+      end
+  end
+end
+
+config :copi, Copi.RateLimiter,
+  # Maximum number of games that can be created from a single IP in the time window
+  max_games_per_ip: env_integer.("MAX_GAMES_PER_IP", 10),
+  # Time window in seconds for game creation rate limiting (default: 1 hour)
+  game_creation_window_seconds: env_integer.("GAME_CREATION_WINDOW_SECONDS", 3600),
+  # Maximum number of players that can be created from a single IP in the time window
+  max_players_per_ip: env_integer.("MAX_PLAYERS_PER_IP", 20),
+  # Time window in seconds for player creation rate limiting (default: 1 hour)
+  player_creation_window_seconds: env_integer.("PLAYER_CREATION_WINDOW_SECONDS", 3600),
+  # Maximum number of WebSocket connections from a single IP in the time window
+  max_connections_per_ip: env_integer.("MAX_CONNECTIONS_PER_IP", 50),
+  # Time window in seconds for connection rate limiting (default: 5 minutes)
+  connection_window_seconds: env_integer.("CONNECTION_WINDOW_SECONDS", 300)

copi.owasp.org/lib/copi/application.ex

@@ -15,6 +15,8 @@ defmodule Copi.Application do
       {Phoenix.PubSub, name: Copi.PubSub},
       # Start the DNS clustering
       {DNSCluster, query: Application.get_env(:copi, :dns_cluster_query) || :ignore},
+      # Start the Rate Limiter for security (CAPEC-212 protection)
+      Copi.RateLimiter,
       # Start the Endpoint (http/https)
       CopiWeb.Endpoint
       # Start a worker by calling: Copi.Worker.start_link(arg)

copi.owasp.org/lib/copi/rate_limiter.ex

@@ -0,0 +1,229 @@
+defmodule Copi.RateLimiter do
+  @moduledoc """
+  Rate limiter to prevent abuse by limiting requests per IP address.
+
+  This module implements rate limiting for game creation, player creation, and user connections
+  to protect against CAPEC 212 (Functionality Misuse) attacks.
+  """
+
+  use GenServer
+  require Logger
+
+  @cleanup_interval :timer.minutes(5)
+
+  # Client API
+
+  @doc """
+  Starts the rate limiter GenServer.
+  """
+  def start_link(opts \\ []) do
+    GenServer.start_link(__MODULE__, opts, name: __MODULE__)
+  end
+
+  @doc """
+  Checks if a request from the given IP for the specified action should be allowed.
+
+  Returns `{:ok, remaining}` if allowed, `{:error, :rate_limited, retry_after}` if blocked.
+  """
+  def check_rate(ip_address, action) when action in [:game_creation, :player_creation, :connection] do
+    GenServer.call(__MODULE__, {:check_rate, ip_address, action})
+  end
+
+  @doc """
+  Atomically checks and records a rate limit action in a single operation.
+  This prevents race conditions where multiple concurrent requests could bypass the limit.
+
+  Returns `{:ok, remaining}` if allowed (and records the action), 
+  `{:error, :rate_limited, retry_after}` if blocked (does not record).
+  """
+  def check_and_record(ip_address, action) when action in [:game_creation, :player_creation, :connection] do
+    GenServer.call(__MODULE__, {:check_and_record, ip_address, action})
+  end
+
+  @doc """
+  Records a successful action for rate limiting tracking.
+  """
+  def record_action(ip_address, action) when action in [:game_creation, :player_creation, :connection] do
+    GenServer.cast(__MODULE__, {:record_action, ip_address, action})
+  end
+
+  @doc """
+  Clears all rate limit data for an IP address (useful for testing).
+  """
+  def clear_ip(ip_address) do
+    GenServer.cast(__MODULE__, {:clear_ip, ip_address})
+  end
+
+  @doc """
+  Gets current rate limit configuration.
+  """
+  def get_config do
+    GenServer.call(__MODULE__, :get_config)
+  end
+
+  # Server callbacks
+
+  @impl true
+  def init(_opts) do
+    # Schedule periodic cleanup
+    schedule_cleanup()
+
+    config = %{
+      game_creation: %{
+        max_requests: get_env(:max_games_per_ip, 10),
+        window_seconds: get_env(:game_creation_window_seconds, 3600)
+      },
+      player_creation: %{
+        max_requests: get_env(:max_players_per_ip, 20),
+        window_seconds: get_env(:player_creation_window_seconds, 3600)
+      },
+      connection: %{
+        max_requests: get_env(:max_connections_per_ip, 50),
+        window_seconds: get_env(:connection_window_seconds, 300)
+      }
+    }
+
+    state = %{
+      requests: %{},
+      config: config
+    }
+
+    Logger.info("RateLimiter started with config: #{inspect(config)}")
+
+    {:ok, state}
+  end
+
+  @impl true
+  def handle_call({:check_rate, ip_address, action}, _from, state) do
+    now = System.system_time(:second)
+    config = state.config[action]
+
+    ip_requests = get_ip_requests(state, ip_address, action)
+
+    # Filter out expired requests
+    valid_requests = Enum.filter(ip_requests, fn timestamp ->
+      now - timestamp < config.window_seconds
+    end)
+
+    count = length(valid_requests)
+    remaining = max(0, config.max_requests - count)
+
+    if count < config.max_requests do
+      {:reply, {:ok, remaining}, state}
+    else
+      oldest_request = List.first(valid_requests)
+      retry_after = oldest_request + config.window_seconds - now
+
+      Logger.warning(
+        "Rate limit exceeded for IP #{inspect(ip_address)}, action: #{action}, " <>
+        "count: #{count}/#{config.max_requests}, retry_after: #{retry_after}s"
+      )
+
+      {:reply, {:error, :rate_limited, retry_after}, state}
+    end
+  end
+
+  @impl true
+  def handle_call({:check_and_record, ip_address, action}, _from, state) do
+    now = System.system_time(:second)
+    config = state.config[action]
+
+    ip_requests = get_ip_requests(state, ip_address, action)
+
+    # Filter out expired requests
+    valid_requests = Enum.filter(ip_requests, fn timestamp ->
+      now - timestamp < config.window_seconds
+    end)
+
+    count = length(valid_requests)
+    remaining = max(0, config.max_requests - count)
+
+    if count < config.max_requests do
+      # Atomically record the action before returning success
+      updated_requests = [now | valid_requests]
+      new_requests = put_in(state.requests, [ip_address, action], updated_requests)
+      new_state = %{state | requests: new_requests}
+
+      {:reply, {:ok, remaining}, new_state}
+    else
+      oldest_request = List.first(valid_requests)
+      retry_after = oldest_request + config.window_seconds - now
+
+      Logger.warning(
+        "Rate limit exceeded for IP #{inspect(ip_address)}, action: #{action}, " <>
+        "count: #{count}/#{config.max_requests}, retry_after: #{retry_after}s"
+      )
+
+      {:reply, {:error, :rate_limited, retry_after}, state}
+    end
+  end
+
+  @impl true
+  def handle_call(:get_config, _from, state) do
+    {:reply, state.config, state}
+  end
+
+  @impl true
+  def handle_cast({:record_action, ip_address, action}, state) do
+    now = System.system_time(:second)
+
+    ip_requests = get_ip_requests(state, ip_address, action)
+    updated_requests = [now | ip_requests]
+
+    new_requests = put_in(
+      state.requests,
+      [ip_address, action],
+      updated_requests
+    )
+
+    {:noreply, %{state | requests: new_requests}}
+  end
+
+  @impl true
+  def handle_cast({:clear_ip, ip_address}, state) do
+    new_requests = Map.delete(state.requests, ip_address)
+    {:noreply, %{state | requests: new_requests}}
+  end
+
+  @impl true
+  def handle_info(:cleanup, state) do
+    now = System.system_time(:second)
+
+    cleaned_requests = state.requests
+    |> Enum.map(fn {ip, actions} ->
+      cleaned_actions = actions
+      |> Enum.map(fn {action, timestamps} ->
+        config = state.config[action]
+        valid_timestamps = Enum.filter(timestamps, fn timestamp ->
+          now - timestamp < config.window_seconds
+        end)
+        {action, valid_timestamps}
+      end)
+      |> Enum.filter(fn {_action, timestamps} -> length(timestamps) > 0 end)
+      |> Map.new()
+
+      {ip, cleaned_actions}
+    end)
+    |> Enum.filter(fn {_ip, actions} -> map_size(actions) > 0 end)
+    |> Map.new()
+
+    schedule_cleanup()
+
+    {:noreply, %{state | requests: cleaned_requests}}
+  end
+
+  # Private helpers
+
+  defp get_ip_requests(state, ip_address, action) do
+    get_in(state.requests, [ip_address, action]) || []
+  end
+
+  defp schedule_cleanup do
+    Process.send_after(self(), :cleanup, @cleanup_interval)
+  end
+
+  defp get_env(key, default) do
+    Application.get_env(:copi, __MODULE__, [])
+    |> Keyword.get(key, default)
+  end
+end

copi.owasp.org/lib/copi_web/endpoint.ex

@@ -12,8 +12,8 @@ defmodule CopiWeb.Endpoint do
   ]
 
   socket "/live", Phoenix.LiveView.Socket,
-    websocket: [timeout: 45_000, connect_info: [session: @session_options]],
-    longpoll: [connect_info: [session: @session_options]]
+    websocket: [timeout: 45_000, connect_info: [:peer_data, session: @session_options]],
+    longpoll: [connect_info: [:peer_data, session: @session_options]]
 
   # Serve at "/" the static files from "priv/static" directory.
   #

copi.owasp.org/lib/copi_web/helpers/ip_helper.ex

@@ -0,0 +1,37 @@
+defmodule CopiWeb.Helpers.IPHelper do
+  @moduledoc """
+  Helper functions for extracting and formatting IP addresses from socket connections.
+  """
+
+  @doc """
+  Extracts the IP address from a LiveView socket connection.
+
+  Returns a string representation of the IP address (IPv4 or IPv6).
+  Raises an error if the IP address cannot be determined, as this should never
+  happen in a properly configured backend environment.
+
+  ## Examples
+
+      iex> get_connect_ip(socket)
+      "192.168.1.1"
+
+      iex> get_connect_ip(socket)
+      "2001:db8::1"
+  """
+  def get_connect_ip(socket) do
+    case Phoenix.LiveView.get_connect_info(socket, :peer_data) do
+      %{address: address} when is_tuple(address) ->
+        # Use Erlang's :inet.ntoa for proper IPv4/IPv6 formatting
+        address
+        |> :inet.ntoa()
+        |> to_string()
+
+      nil ->
+        raise "Unable to determine IP address from socket connection. peer_data is nil. " <>
+              "Ensure endpoint.ex has :peer_data in connect_info list."
+
+      other ->
+        raise "Unexpected peer_data format: #{inspect(other)}"
+    end
+  end
+end