From 42d87dd7767cde71b7d24633665c0f30ceeb31cf Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Viktor=20S=C3=B6derqvist?= Date: Tue, 31 Oct 2023 11:51:02 +0100 Subject: Add 'max_cancel_stream_rate' config for the rapid reset attack MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Co-authored-by: Björn Svensson --- src/cowboy_http2.erl | 35 ++++++++++++++++++++++++++++++++--- 1 file changed, 32 insertions(+), 3 deletions(-) (limited to 'src') diff --git a/src/cowboy_http2.erl b/src/cowboy_http2.erl index 7440d91..9ad16bd 100644 --- a/src/cowboy_http2.erl +++ b/src/cowboy_http2.erl @@ -48,6 +48,7 @@ max_frame_size_sent => 16384..16777215 | infinity, max_received_frame_rate => {pos_integer(), timeout()}, max_reset_stream_rate => {pos_integer(), timeout()}, + max_cancel_stream_rate => {pos_integer(), timeout()}, max_stream_buffer_size => non_neg_integer(), max_stream_window_size => 0..16#7fffffff, metrics_callback => cowboy_metrics_h:metrics_callback(), @@ -114,6 +115,10 @@ reset_rate_num :: undefined | pos_integer(), reset_rate_time :: undefined | integer(), + %% HTTP/2 rapid reset attack protection. + cancel_rate_num :: undefined | pos_integer(), + cancel_rate_time :: undefined | integer(), + %% Flow requested for all streams. flow = 0 :: non_neg_integer(), @@ -173,9 +178,11 @@ init(Parent, Ref, Socket, Transport, ProxyHeader, Opts, Peer, Sock, Cert, Buffer _ -> parse(State, Buffer) end. -init_rate_limiting(State) -> +init_rate_limiting(State0) -> CurrentTime = erlang:monotonic_time(millisecond), - init_reset_rate_limiting(init_frame_rate_limiting(State, CurrentTime), CurrentTime). + State1 = init_frame_rate_limiting(State0, CurrentTime), + State2 = init_reset_rate_limiting(State1, CurrentTime), + init_cancel_rate_limiting(State2, CurrentTime). init_frame_rate_limiting(State=#state{opts=Opts}, CurrentTime) -> {FrameRateNum, FrameRatePeriod} = maps:get(max_received_frame_rate, Opts, {10000, 10000}), @@ -189,6 +196,12 @@ init_reset_rate_limiting(State=#state{opts=Opts}, CurrentTime) -> reset_rate_num=ResetRateNum, reset_rate_time=add_period(CurrentTime, ResetRatePeriod) }. +init_cancel_rate_limiting(State=#state{opts=Opts}, CurrentTime) -> + {CancelRateNum, CancelRatePeriod} = maps:get(max_cancel_stream_rate, Opts, {500, 10000}), + State#state{ + cancel_rate_num=CancelRateNum, cancel_rate_time=add_period(CurrentTime, CancelRatePeriod) + }. + add_period(_, infinity) -> infinity; add_period(Time, Period) -> Time + Period. @@ -568,11 +581,27 @@ rst_stream_frame(State=#state{streams=Streams0, children=Children0}, StreamID, R {#stream{state=StreamState}, Streams} -> terminate_stream_handler(State, StreamID, Reason, StreamState), Children = cowboy_children:shutdown(Children0, StreamID), - State#state{streams=Streams, children=Children}; + cancel_rate_limit(State#state{streams=Streams, children=Children}); error -> State end. +cancel_rate_limit(State0=#state{cancel_rate_num=Num0, cancel_rate_time=Time}) -> + case Num0 - 1 of + 0 -> + CurrentTime = erlang:monotonic_time(millisecond), + if + CurrentTime < Time -> + terminate(State0, {connection_error, enhance_your_calm, + 'Stream cancel rate larger than configuration allows. Flood? (CVE-2023-44487)'}); + true -> + %% When the option has a period of infinity we cannot reach this clause. + init_cancel_rate_limiting(State0, CurrentTime) + end; + Num -> + State0#state{cancel_rate_num=Num} + end. + ignored_frame(State=#state{http2_machine=HTTP2Machine0}) -> case cow_http2_machine:ignored_frame(HTTP2Machine0) of {ok, HTTP2Machine} -> -- cgit v1.2.3