Stefan-Sanger
a4f17e2506
The mod_websocket continuation-frame patch accumulated fragments in an
unbounded dataBuffer with no size limit, fragment count limit, or
timeout. A buggy or malicious client sending endless continuation
frames without FIN could exhaust memory and degrade the entire server.
Add a configurable websocket_max_message_size option (default 2 MB)
that closes the connection with code 1009 ("Message too big") and
resets the buffer when exceeded. Also add wss-perf-analysis.md
documenting the WebSocket performance and drop investigation.
Part-of: <http://gitlab.vnc.biz/uxf/vnctalk-prosody/-/merge_requests/8>
70 lines
2.1 KiB
Diff
70 lines
2.1 KiB
Diff
--- a/plugins/mod_websocket.lua 2026-07-15 09:48:22.424559760 +0200
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+++ b/plugins/mod_websocket.lua 2026-07-16 12:00:00.000000000 +0200
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@@ -199,9 +199,6 @@
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end
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-- Other (XMPP-specific) validity checks
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- if not frame.FIN then
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- return false, 1003, "Continuation frames are not supported, RFC 7395 3.3.3";
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- end
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if opcode == 0x01 and frame.data and frame.data:byte(1, 1) ~= 60 then
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return false, 1007, "Invalid payload start character, RFC 7395 3.3.3";
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end
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@@ -249,6 +246,9 @@
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end
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end
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+ local max_message_size = module:get_option_number("websocket_max_message_size", 2 * 1024 * 1024);
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+ local dataBufferLen = 0;
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+ local dataBuffer;
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local function handle_frame(frame)
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module:log("debug", "Websocket received frame: opcode=%0x, %i bytes", frame.opcode, #frame.data);
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@@ -266,12 +266,44 @@
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return "";
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elseif opcode == 0xA then -- Pong frame, MAY be sent unsolicited, eg as keepalive
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return "";
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- elseif opcode ~= 0x1 then -- Not text frame (which is all we support)
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+ end
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+
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+ -- Text (0x1) and continuation (0x0) frames: accumulate fragments
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+ if opcode == 0x0 and not dataBuffer then
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+ return false, 1002, "Unexpected continuation frame";
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+ end
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+ if opcode == 0x1 and dataBuffer then
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+ return false, 1002, "Continuation frame expected";
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+ end
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+
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+ if opcode == 0x0 then -- Continuation frame
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+ dataBufferLen = dataBufferLen + #frame.data;
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+ if dataBufferLen > max_message_size then
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+ dataBuffer = nil;
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+ dataBufferLen = 0;
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+ return false, 1009, "Message too big";
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+ end
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+ dataBuffer[#dataBuffer+1] = frame.data;
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+ elseif opcode == 0x1 then -- Text frame
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+ dataBufferLen = #frame.data;
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+ if dataBufferLen > max_message_size then
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+ dataBuffer = nil;
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+ dataBufferLen = 0;
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+ return false, 1009, "Message too big";
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+ end
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+ dataBuffer = { frame.data };
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+ else
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log("warn", "Received frame with unsupported opcode %i", opcode);
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return "";
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end
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- return frame.data;
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+ if frame.FIN then
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+ local data = t_concat(dataBuffer, "");
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+ dataBuffer = nil;
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+ dataBufferLen = 0;
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+ return data;
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+ end
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+ return "";
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end
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conn:setlistener(c2s_listener);
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