Validate that custom HTTP clients return correct stuff (#794)

Author: savhappy

lib/sentry/transport.ex

@@ -58,7 +58,8 @@ defmodule Sentry.Transport do
   end
 
   defp request(client, endpoint, headers, body) do
-    with {:ok, 200, _headers, body} <- client.post(endpoint, headers, body),
+    with {:ok, 200, _headers, body} <-
+           client_post_and_validate_return_value(client, endpoint, headers, body),
          {:ok, json} <- Config.json_library().decode(body) do
       {:ok, Map.get(json, "id")}
     else
@@ -86,6 +87,21 @@ defmodule Sentry.Transport do
     kind, data -> {:error, {kind, data, __STACKTRACE__}}
   end
 
+  defp client_post_and_validate_return_value(client, endpoint, headers, body) do
+    case client.post(endpoint, headers, body) do
+      {:ok, status, resp_headers, resp_body}
+      when is_integer(status) and status in 200..599 and is_list(resp_headers) and
+             is_binary(resp_body) ->
+        {:ok, status, resp_headers, resp_body}
+
+      {:ok, status, resp_headers, resp_body} ->
+        {:error, {:malformed_http_client_response, status, resp_headers, resp_body}}
+
+      {:error, reason} ->
+        {:error, reason}
+    end
+  end
+
   defp get_endpoint_and_headers do
     %Sentry.DSN{} = dsn = Config.dsn()
 

test/sentry/transport_test.exs

@@ -36,6 +36,21 @@ defmodule Sentry.TransportTest do
       assert {:ok, "123"} = Transport.post_envelope(envelope, HackneyClient)
     end
 
+    defmodule InvalidHTTPClient do
+      def post(_endpoint, _headers, _body) do
+        {:ok, "not an integer", :badarg, %{}}
+      end
+    end
+
+    test "returns an error with an invalid response from a POST request" do
+      envelope = Envelope.from_event(Event.create_event(message: "Hello 1"))
+
+      assert {:error,
+              {:request_failure,
+               {:malformed_http_client_response, "not an integer", :badarg, %{}}}} =
+               Transport.post_envelope(envelope, InvalidHTTPClient, _retries = [])
+    end
+
     test "returns the HTTP client's error if the HTTP client returns one", %{bypass: bypass} do
       envelope = Envelope.from_event(Event.create_event(message: "Hello"))