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Add protection against slowloris vulnerability
This changes the behavior of the `timeout` protocol option to mean "Time in which the full request line and headers must be received". The default of 5s should be fine for all normal uses. This change has no noticeable impact on performance and is thus enabled by default for everyone. It can be disabled by setting `timeout` to `infinity` although that is definitely not encouraged. Inspired by the contribution from @naryl on github.
This commit is contained in:
Loïc Hoguin
parent
638d0345d1
commit
a013becc66
2 changed files with 72 additions and 16 deletions
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@ -38,8 +38,8 @@
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%% not available at this point.</dd>
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%% <dt>onresponse</dt><dd>Optional fun that allows replacing a response
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%% sent by the application.</dd>
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%% <dt>timeout</dt><dd>Time in milliseconds before an idle
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%% connection is closed. Defaults to 5000 milliseconds.</dd>
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%% <dt>timeout</dt><dd>Time in milliseconds a client has to send the
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%% full request line and headers. Defaults to 5000 milliseconds.</dd>
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%% </dl>
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%%
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%% Note that there is no need to monitor these processes when using Cowboy as
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@ -74,7 +74,8 @@
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max_header_name_length :: non_neg_integer(),
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max_header_value_length :: non_neg_integer(),
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max_headers :: non_neg_integer(),
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timeout :: timeout()
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timeout :: timeout(),
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until :: non_neg_integer() | infinity
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}).
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%% API.
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@ -116,7 +117,15 @@ init(ListenerPid, Socket, Transport, Opts) ->
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max_request_line_length=MaxRequestLineLength,
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max_header_name_length=MaxHeaderNameLength,
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max_header_value_length=MaxHeaderValueLength, max_headers=MaxHeaders,
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timeout=Timeout, onrequest=OnRequest, onresponse=OnResponse}, 0).
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onrequest=OnRequest, onresponse=OnResponse,
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timeout=Timeout, until=until(Timeout)}, 0).
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-spec until(timeout()) -> non_neg_integer() | infinity.
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until(infinity) ->
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infinity;
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until(Timeout) ->
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{Me, S, Mi} = os:timestamp(),
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Me * 1000000000 + S * 1000 + Mi div 1000 + Timeout.
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%% Request parsing.
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%%
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@ -125,10 +134,24 @@ init(ListenerPid, Socket, Transport, Opts) ->
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%% right after the header parsing is finished and the code becomes
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%% more interesting past that point.
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-spec recv(inet:socket(), module(), non_neg_integer() | infinity)
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-> {ok, binary()} | {error, closed | timeout | atom()}.
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recv(Socket, Transport, infinity) ->
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Transport:recv(Socket, 0, infinity);
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recv(Socket, Transport, Until) ->
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{Me, S, Mi} = os:timestamp(),
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Now = Me * 1000000000 + S * 1000 + Mi div 1000,
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Timeout = Until - Now,
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if Timeout < 0 ->
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{error, timeout};
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true ->
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Transport:recv(Socket, 0, Timeout)
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end.
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-spec wait_request(binary(), #state{}, non_neg_integer()) -> ok.
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wait_request(Buffer, State=#state{socket=Socket, transport=Transport,
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timeout=Timeout}, ReqEmpty) ->
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case Transport:recv(Socket, 0, Timeout) of
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until=Until}, ReqEmpty) ->
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case recv(Socket, Transport, Until) of
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{ok, Data} ->
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parse_request(<< Buffer/binary, Data/binary >>, State, ReqEmpty);
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{error, _} ->
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@ -219,8 +242,8 @@ wait_header(_, State=#state{max_headers=MaxHeaders}, _, _, _, _, _, Headers)
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when length(Headers) >= MaxHeaders ->
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error_terminate(400, State);
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wait_header(Buffer, State=#state{socket=Socket, transport=Transport,
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timeout=Timeout}, M, P, Q, F, V, H) ->
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case Transport:recv(Socket, 0, Timeout) of
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until=Until}, M, P, Q, F, V, H) ->
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case recv(Socket, Transport, Until) of
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{ok, Data} ->
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parse_header(<< Buffer/binary, Data/binary >>,
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State, M, P, Q, F, V, H);
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@ -291,9 +314,9 @@ parse_hd_name_ws(<< C, Rest/bits >>, S, M, P, Q, F, V, H, Name) ->
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end.
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wait_hd_before_value(Buffer, State=#state{
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socket=Socket, transport=Transport, timeout=Timeout},
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socket=Socket, transport=Transport, until=Until},
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M, P, Q, F, V, H, N) ->
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case Transport:recv(Socket, 0, Timeout) of
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case recv(Socket, Transport, Until) of
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{ok, Data} ->
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parse_hd_before_value(<< Buffer/binary, Data/binary >>,
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State, M, P, Q, F, V, H, N);
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@ -323,9 +346,9 @@ parse_hd_before_value(Buffer, State=#state{
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%% to change the other arguments' position and trigger costy
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%% operations for no reasons.
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wait_hd_value(_, State=#state{
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socket=Socket, transport=Transport, timeout=Timeout},
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socket=Socket, transport=Transport, until=Until},
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M, P, Q, F, V, H, N, SoFar) ->
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case Transport:recv(Socket, 0, Timeout) of
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case recv(Socket, Transport, Until) of
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{ok, Data} ->
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parse_hd_value(Data, State, M, P, Q, F, V, H, N, SoFar);
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{error, timeout} ->
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@ -338,9 +361,9 @@ wait_hd_value(_, State=#state{
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%% to check for multilines allows us to avoid a few tests in
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%% the critical path, but forces us to have a special function.
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wait_hd_value_nl(_, State=#state{
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socket=Socket, transport=Transport, timeout=Timeout},
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socket=Socket, transport=Transport, until=Until},
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M, P, Q, F, V, Headers, Name, SoFar) ->
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case Transport:recv(Socket, 0, Timeout) of
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case recv(Socket, Transport, Until) of
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{ok, << C, Data/bits >>} when C =:= $\s; C =:= $\t ->
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parse_hd_value(Data, State, M, P, Q, F, V, Headers, Name, SoFar);
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{ok, Data} ->
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@ -492,7 +515,8 @@ resume(State, Env, Tail, Module, Function, Args) ->
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end.
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-spec next_request(cowboy_req:req(), #state{}, any()) -> ok.
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next_request(Req, State=#state{req_keepalive=Keepalive}, HandlerRes) ->
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next_request(Req, State=#state{req_keepalive=Keepalive, timeout=Timeout},
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HandlerRes) ->
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cowboy_req:ensure_response(Req, 204),
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{BodyRes, [Buffer, Connection]} = case cowboy_req:skip_body(Req) of
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{ok, Req2} -> {ok, cowboy_req:get([buffer, connection], Req2)};
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@ -503,7 +527,7 @@ next_request(Req, State=#state{req_keepalive=Keepalive}, HandlerRes) ->
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case {HandlerRes, BodyRes, Connection} of
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{ok, ok, keepalive} ->
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?MODULE:parse_request(Buffer, State#state{
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req_keepalive=Keepalive + 1}, 0);
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req_keepalive=Keepalive + 1, until=until(Timeout)}, 0);
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_Closed ->
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terminate(State)
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end.
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@ -60,6 +60,8 @@
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-export([set_resp_body/1]).
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-export([set_resp_header/1]).
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-export([set_resp_overwrite/1]).
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-export([slowloris/1]).
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-export([slowloris2/1]).
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-export([static_attribute_etag/1]).
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-export([static_function_etag/1]).
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-export([static_mimetypes_function/1]).
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@ -110,6 +112,8 @@ groups() ->
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set_resp_body,
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set_resp_header,
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set_resp_overwrite,
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slowloris,
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slowloris2,
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static_attribute_etag,
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static_function_etag,
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static_mimetypes_function,
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@ -812,6 +816,34 @@ set_resp_overwrite(Config) ->
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{<<"server">>, <<"DesireDrive/1.0">>}
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= lists:keyfind(<<"server">>, 1, Headers).
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slowloris(Config) ->
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Client = ?config(client, Config),
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Transport = ?config(transport, Config),
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{ok, Client2} = cowboy_client:connect(
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Transport, "localhost", ?config(port, Config), Client),
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try
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[begin
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{ok, _} = cowboy_client:raw_request([C], Client2),
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receive after 25 -> ok end
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end || C <- "GET / HTTP/1.1\r\nHost: localhost\r\n"
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"User-Agent: Mozilla/5.0 (Windows; U; Windows NT 6.0; en-US)\r\n"
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"Cookie: name=aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\r\n\r\n"],
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error(failure)
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catch error:{badmatch, _} ->
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ok
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end.
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slowloris2(Config) ->
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Client = ?config(client, Config),
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Transport = ?config(transport, Config),
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{ok, Client2} = cowboy_client:connect(
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Transport, "localhost", ?config(port, Config), Client),
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{ok, _} = cowboy_client:raw_request("GET / HTTP/1.1\r\n", Client2),
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receive after 300 -> ok end,
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{ok, _} = cowboy_client:raw_request("Host: localhost\r\n", Client2),
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receive after 300 -> ok end,
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{ok, 408, _, _} = cowboy_client:response(Client2).
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static_attribute_etag(Config) ->
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Client = ?config(client, Config),
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{ok, Client2} = cowboy_client:request(<<"GET">>,
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