Avoid leaking Authorization request headers in cleartext for Phoenix Controllers

lib/error_tracker/integrations/plug.ex

@@ -111,14 +111,16 @@ defmodule ErrorTracker.Integrations.Plug do
     conn |> build_context |> ErrorTracker.set_context()
   end
 
+  @sensitive_headers ["cookie", "authorization"]
+
   defp build_context(conn = %Plug.Conn{}) do
     %{
       "request.host" => conn.host,
       "request.path" => conn.request_path,
       "request.query" => conn.query_string,
       "request.method" => conn.method,
       "request.ip" => remote_ip(conn),
-      "request.headers" => conn.req_headers |> Map.new() |> Map.drop(["cookie"]),
+      "request.headers" => conn.req_headers |> Map.new() |> Map.drop(@sensitive_headers),
       # Depending on the error source, the request params may have not been fetched yet
       "request.params" => unless(is_struct(conn.params, Plug.Conn.Unfetched), do: conn.params)
     }

test/integrations/plug_test.exs

@@ -0,0 +1,57 @@
+defmodule ErrorTracker.Integrations.PlugTest do
+  use ErrorTracker.Test.Case
+
+  alias ErrorTracker.Integrations.Plug, as: IntegrationPlug
+
+  @fake_callstack []
+
+  setup do
+    [conn: Phoenix.ConnTest.build_conn()]
+  end
+
+  test "it reports errors, including the request headers", %{conn: conn} do
+    conn = conn |> Plug.Conn.put_req_header("accept", "application/json")
+
+    IntegrationPlug.report_error(
+      conn,
+      {"an error from Phoenix", "something bad happened"},
+      @fake_callstack
+    )
+
+    [error] = repo().all(ErrorTracker.Error)
+
+    assert error.kind == "an error from Phoenix"
+    assert error.reason == "something bad happened"
+
+    [occurrence] = repo().all(ErrorTracker.Occurrence)
+    assert occurrence.error_id == error.id
+
+    %{"request.headers" => request_headers} = occurrence.context
+    assert request_headers == %{"accept" => "application/json"}
+  end
+
+  test "it does not save sensitive request headers, to avoid storing them in cleartext", %{
+    conn: conn
+  } do
+    conn =
+      conn
+      |> Plug.Conn.put_req_header("cookie", "who stole the cookie from the cookie jar ?")
+      |> Plug.Conn.put_req_header("authorization", "Bearer plz-dont-leak-my-secrets")
+      |> Plug.Conn.put_req_header("safe", "this can be safely stored in cleartext")
+
+    IntegrationPlug.report_error(
+      conn,
+      {"an error from Phoenix", "something bad happened"},
+      @fake_callstack
+    )
+
+    [occurrence] = repo().all(ErrorTracker.Occurrence)
+
+    header_names = occurrence.context |> Map.get("request.headers") |> Map.keys()
+
+    assert "cookie" not in header_names
+    assert "authorization" not in header_names
+
+    assert "safe" in header_names
+  end
+end