Ignore client_max_window_bits with missing header

When the client does not provide the "client_max_window_bits" option, the server must reserve the max size. Co-authored-by: Ignacio Martínez <[email protected]>
ninenines · Oct 5, 2021 · 5990041 · 5990041
1 parent 0f5c2f8
commit 5990041
Showing 1 changed file with 11 additions and 3 deletions.
diff --git a/src/cow_ws.erl b/src/cow_ws.erl
@@ -141,8 +141,14 @@ negotiate_permessage_deflate1(Params, Extensions, Opts) ->
 				_ -> [<<"; server_max_window_bits=">>,
 					integer_to_binary(ServerMaxWindowBits)|RespParams2]
 			end,
+			NegotiatedClientMaxWindowBits = case Negotiated of
+				#{client_max_window_bits_set := true} ->
+					maps:get(client_max_window_bits, Negotiated);
+				_ ->
+					15
+			end,
 			{Inflate, Deflate} = init_permessage_deflate(
-				maps:get(client_max_window_bits, Negotiated),
+				NegotiatedClientMaxWindowBits,
 				maps:get(server_max_window_bits, Negotiated), Opts),
 			{ok, [<<"permessage-deflate">>, RespParams], Extensions#{
 				deflate => Deflate,
@@ -165,12 +171,14 @@ negotiate_params([{<<"client_max_window_bits">>, Max}|Tail], Negotiated, RespPar
 		error ->
 			ignore;
 		CB when CB =< CB0 ->
-			negotiate_params(Tail, Negotiated#{client_max_window_bits => CB},
+			negotiate_params(Tail,
+				Negotiated#{client_max_window_bits => CB,
+					client_max_window_bits_set => true},
 				[<<"; client_max_window_bits=">>, Max|RespParams]);
 		%% When the client sends window bits larger than the server wants
 		%% to use, we use what the server defined.
 		_ ->
-			negotiate_params(Tail, Negotiated,
+			negotiate_params(Tail, Negotiated#{client_max_window_bits_set => true},
 				[<<"; client_max_window_bits=">>, integer_to_binary(CB0)|RespParams])
 	end;
 negotiate_params([{<<"server_max_window_bits">>, Max}|Tail], Negotiated, RespParams) ->