diff options
| -rw-r--r-- | plugins/mod_websocket.lua | 172 |
1 files changed, 95 insertions, 77 deletions
diff --git a/plugins/mod_websocket.lua b/plugins/mod_websocket.lua index ecc12a45..a613672b 100644 --- a/plugins/mod_websocket.lua +++ b/plugins/mod_websocket.lua @@ -142,6 +142,65 @@ local function filter_open_close(data) return data; end + +local function validate_frame(frame, max_length) + local opcode, length = frame.opcode, frame.length; + + if max_length and length > max_length then + return false, 1009, "Payload too large"; + end + + -- Error cases + if frame.RSV1 or frame.RSV2 or frame.RSV3 then -- Reserved bits non zero + return false, 1002, "Reserved bits not zero"; + end + + if opcode == 0x8 and frame.data then -- close frame + if length == 1 then + return false, 1002, "Close frame with payload, but too short for status code"; + elseif length >= 2 then + local status_code = parse_close(frame.data) + if status_code < 1000 then + return false, 1002, "Closed with invalid status code"; + elseif ((status_code > 1003 and status_code < 1007) or status_code > 1011) and status_code < 3000 then + return false, 1002, "Closed with reserved status code"; + end + end + end + + if opcode >= 0x8 then + if length > 125 then -- Control frame with too much payload + return false, 1002, "Payload too large"; + end + + if not frame.FIN then -- Fragmented control frame + return false, 1002, "Fragmented control frame"; + end + end + + if (opcode > 0x2 and opcode < 0x8) or (opcode > 0xA) then + return false, 1002, "Reserved opcode"; + end + + -- Check opcode + if opcode == 0x2 then -- Binary frame + return false, 1003, "Only text frames are supported, RFC 7395 3.2"; + elseif opcode == 0x8 then -- Close request + return false, 1000, "Goodbye"; + end + + -- Other (XMPP-specific) validity checks + if not frame.FIN then + return false, 1003, "Continuation frames are not supported, RFC 7395 3.3.3"; + end + if opcode == 0x01 and frame.data and frame.data:byte(1, 1) ~= 60 then + return false, 1007, "Invalid payload start character, RFC 7395 3.3.3"; + end + + return true; +end + + function handle_request(event) local request, response = event.request, event.response; local conn = response.conn; @@ -172,90 +231,40 @@ function handle_request(event) conn:close(); end - local dataBuffer; - local function handle_frame(frame) - local opcode = frame.opcode; - local length = frame.length; - module:log("debug", "Websocket received frame: opcode=%0x, %i bytes", frame.opcode, #frame.data); - - -- Error cases - if frame.RSV1 or frame.RSV2 or frame.RSV3 then -- Reserved bits non zero - websocket_close(1002, "Reserved bits not zero"); - return false; - end - - if opcode == 0x8 then -- close frame - if length == 1 then - websocket_close(1002, "Close frame with payload, but too short for status code"); - return false; - elseif length >= 2 then - local status_code = parse_close(frame.data) - if status_code < 1000 then - websocket_close(1002, "Closed with invalid status code"); - return false; - elseif ((status_code > 1003 and status_code < 1007) or status_code > 1011) and status_code < 3000 then - websocket_close(1002, "Closed with reserved status code"); - return false; - end - end - end - - if opcode >= 0x8 then - if length > 125 then -- Control frame with too much payload - websocket_close(1002, "Payload too large"); - return false; - end - - if not frame.FIN then -- Fragmented control frame - websocket_close(1002, "Fragmented control frame"); - return false; - end - end - - if (opcode > 0x2 and opcode < 0x8) or (opcode > 0xA) then - websocket_close(1002, "Reserved opcode"); - return false; + local function websocket_handle_error(session, code, message) + if code == 1009 then -- stanza size limit exceeded + -- we close the session, rather than the connection, + -- otherwise a resuming client will simply resend the + -- offending stanza + session:close({ condition = "policy-violation", text = "stanza too large" }); + else + websocket_close(code, message); end + end - if opcode == 0x0 and not dataBuffer then - websocket_close(1002, "Unexpected continuation frame"); - return false; - end + local function handle_frame(frame) + module:log("debug", "Websocket received frame: opcode=%0x, %i bytes", frame.opcode, #frame.data); - if (opcode == 0x1 or opcode == 0x2) and dataBuffer then - websocket_close(1002, "Continuation frame expected"); - return false; + -- Check frame makes sense + local frame_ok, err_status, err_text = validate_frame(frame, stanza_size_limit); + if not frame_ok then + return frame_ok, err_status, err_text; end - -- Valid cases - if opcode == 0x0 then -- Continuation frame - dataBuffer[#dataBuffer+1] = frame.data; - elseif opcode == 0x1 then -- Text frame - dataBuffer = {frame.data}; - elseif opcode == 0x2 then -- Binary frame - websocket_close(1003, "Only text frames are supported"); - return; - elseif opcode == 0x8 then -- Close request - websocket_close(1000, "Goodbye"); - return; - elseif opcode == 0x9 then -- Ping frame + local opcode = frame.opcode; + if opcode == 0x9 then -- Ping frame frame.opcode = 0xA; frame.MASK = false; -- Clients send masked frames, servers don't, see #1484 conn:write(build_frame(frame)); return ""; elseif opcode == 0xA then -- Pong frame, MAY be sent unsolicited, eg as keepalive return ""; - else + elseif opcode ~= 0x1 then -- Not text frame (which is all we support) log("warn", "Received frame with unsupported opcode %i", opcode); return ""; end - if frame.FIN then - local data = t_concat(dataBuffer, ""); - dataBuffer = nil; - return data; - end - return ""; + return frame.data; end conn:setlistener(c2s_listener); @@ -282,19 +291,28 @@ function handle_request(event) end local cache = {}; - local frame, length = parse_frame(frameBuffer); + local frame, length, partial = parse_frame(frameBuffer); while frame do - if length > stanza_size_limit then - session:close({ condition = "policy-violation", text = "stanza too large" }); - return; - end frameBuffer:discard(length); - local result = handle_frame(frame); - if not result then break; end + local result, err_status, err_text = handle_frame(frame); + if not result then + websocket_handle_error(session, err_status, err_text); + break; + end cache[#cache+1] = filter_open_close(result); - frame, length = parse_frame(frameBuffer); + frame, length, partial = parse_frame(frameBuffer); end + + if partial then + -- The header of the next frame is already in the buffer, run + -- some early validation here + local frame_ok, err_status, err_text = validate_frame(partial, stanza_size_limit); + if not frame_ok then + websocket_handle_error(session, err_status, err_text); + end + end + return t_concat(cache, ""); end); |