https://github.com/zookzook/bandit-plug-parser-test
Demo app showing buffer issue when sending invalid JSON payloads
https://github.com/zookzook/bandit-plug-parser-test
Last synced: 2 months ago
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Demo app showing buffer issue when sending invalid JSON payloads
- Host: GitHub
- URL: https://github.com/zookzook/bandit-plug-parser-test
- Owner: zookzook
- Created: 2025-01-07T07:53:30.000Z (4 months ago)
- Default Branch: main
- Last Pushed: 2025-01-07T08:02:07.000Z (4 months ago)
- Last Synced: 2025-01-17T23:35:31.471Z (4 months ago)
- Language: Elixir
- Size: 36.1 KB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
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README
# ParserTest
Shows an issue if a client sends an invalid JSON using keep-alive connections:
```bash
curl -X 'POST' \
'http://localhost:4000/api' \
-H 'accept: */*' \
-H 'Content-Type: application/json' \
-d '{"hello": broken}' \
--next -X 'POST' \
'http://localhost:4000/api' \
-H 'accept: */*' \
-H 'Content-Type: application/json' \
-d '{"hello": "world"}'
```
sends two requests using the same keepalive connection. The first request is invalid
while the second is valid. It results in two errors:
```
[info] POST /api
[debug] ** (Plug.Parsers.ParseError) malformed request, a Jason.DecodeError exception was raised with message "unexpected byte at position 10: 0x62 (\"b\")"
(plug 1.16.1) lib/plug/parsers/json.ex:95: Plug.Parsers.JSON.decode/3
(plug 1.16.1) lib/plug/parsers.ex:340: Plug.Parsers.reduce/8
(parser_test 0.1.0) lib/parser_test_web/endpoint.ex:1: ParserTestWeb.Endpoint.plug_builder_call/2
(parser_test 0.1.0) deps/plug/lib/plug/debugger.ex:136: ParserTestWeb.Endpoint."call (overridable 3)"/2
(parser_test 0.1.0) lib/parser_test_web/endpoint.ex:1: ParserTestWeb.Endpoint.call/2
(phoenix 1.7.18) lib/phoenix/endpoint/sync_code_reload_plug.ex:22: Phoenix.Endpoint.SyncCodeReloadPlug.do_call/4
(bandit 1.6.2) lib/bandit/pipeline.ex:129: Bandit.Pipeline.call_plug!/2
(bandit 1.6.2) lib/bandit/pipeline.ex:40: Bandit.Pipeline.run/4
(bandit 1.6.2) lib/bandit/http1/handler.ex:12: Bandit.HTTP1.Handler.handle_data/3
(bandit 1.6.2) lib/bandit/delegating_handler.ex:18: Bandit.DelegatingHandler.handle_data/3
(bandit 1.6.2) lib/bandit/delegating_handler.ex:8: Bandit.DelegatingHandler.handle_continue/2
(stdlib 6.0.1) gen_server.erl:2163: :gen_server.try_handle_continue/3
(stdlib 6.0.1) gen_server.erl:2072: :gen_server.loop/7
(stdlib 6.0.1) proc_lib.erl:329: :proc_lib.init_p_do_apply/3
[error] ** (Bandit.HTTPError) Request line HTTP error: "{\"hello\": broken}POST /api HTTP/1.1\r\n"
```
Plug uses an exception and a 400 status code.
While throwing the exception the changes to the buffer used to parse the invalid JSON is dropped.
When using keepalive connections, Bandit does not close the connection in case of this status code,
the buffer is reused for the next request
The next request is added to the buffer. This leads to a wrong request and the connection is closed:
```elixir
defp handle_error(kind, reason, stacktrace, transport, span, opts, metadata) do
Bandit.Telemetry.span_exception(span, kind, reason, stacktrace)
status = reason |> Plug.Exception.status() |> Plug.Conn.Status.code()
if status in Keyword.get(opts.http, :log_exceptions_with_status_codes, 500..599) do
logger_metadata = Bandit.Logger.logger_metadata_for(kind, reason, stacktrace, metadata)
Logger.error(Exception.format(kind, reason, stacktrace), logger_metadata)
Bandit.HTTPTransport.send_on_error(transport, reason)
{:error, reason}
else
Bandit.HTTPTransport.send_on_error(transport, reason)
{:ok, transport}
end
end
```
When changing the default status code to 500:
```elixir
try do
apply(module, fun, [body | args])
rescue
e -> raise Plug.Parsers.ParseError, exception: e, plug_status: 500
else
```
the connection is closed and the second request is processed successfully:
```
[info] POST /api
[error] ** (Plug.Parsers.ParseError) malformed request, a Jason.DecodeError exception was raised with message "unexpected byte at position 10: 0x62 (\"b\")"
(parser_test 0.1.0) lib/parser_test_web/json_parser.ex:95: JSON.decode/3
(plug 1.16.1) lib/plug/parsers.ex:340: Plug.Parsers.reduce/8
(parser_test 0.1.0) lib/parser_test_web/endpoint.ex:1: ParserTestWeb.Endpoint.plug_builder_call/2
(parser_test 0.1.0) deps/plug/lib/plug/debugger.ex:136: ParserTestWeb.Endpoint."call (overridable 3)"/2
(parser_test 0.1.0) lib/parser_test_web/endpoint.ex:1: ParserTestWeb.Endpoint.call/2
(phoenix 1.7.18) lib/phoenix/endpoint/sync_code_reload_plug.ex:22: Phoenix.Endpoint.SyncCodeReloadPlug.do_call/4
(bandit 1.6.2) lib/bandit/pipeline.ex:129: Bandit.Pipeline.call_plug!/2
(bandit 1.6.2) lib/bandit/pipeline.ex:40: Bandit.Pipeline.run/4
(bandit 1.6.2) lib/bandit/http1/handler.ex:12: Bandit.HTTP1.Handler.handle_data/3
(bandit 1.6.2) lib/bandit/delegating_handler.ex:18: Bandit.DelegatingHandler.handle_data/3
(bandit 1.6.2) lib/bandit/delegating_handler.ex:8: Bandit.DelegatingHandler.handle_continue/2
(stdlib 6.0.1) gen_server.erl:2163: :gen_server.try_handle_continue/3
(stdlib 6.0.1) gen_server.erl:2072: :gen_server.loop/7
(stdlib 6.0.1) proc_lib.erl:329: :proc_lib.init_p_do_apply/3
[info] POST /api
[debug] Processing with ParserTestWeb.PageController.home/2
Parameters: %{"hello" => "world"}
Pipelines: [:api]
[info] Sent 200 in 7ms
```