diff options
Diffstat (limited to 'net/websocket/frames.lua')
| -rw-r--r-- | net/websocket/frames.lua | 195 |
1 files changed, 195 insertions, 0 deletions
diff --git a/net/websocket/frames.lua b/net/websocket/frames.lua new file mode 100644 index 00000000..8bbddd1c --- /dev/null +++ b/net/websocket/frames.lua @@ -0,0 +1,195 @@ +-- Prosody IM +-- Copyright (C) 2012 Florian Zeitz +-- Copyright (C) 2014 Daurnimator +-- +-- This project is MIT/X11 licensed. Please see the +-- COPYING file in the source package for more information. +-- + +local softreq = require "util.dependencies".softreq; +local log = require "util.logger".init "websocket.frames"; +local random_bytes = require "util.random".bytes; + +local bit; +pcall(function() bit = require"bit"; end); +bit = bit or softreq"bit32" +if not bit then log("error", "No bit module found. Either LuaJIT 2, lua-bitop or Lua 5.2 is required"); end +local band = bit.band; +local bor = bit.bor; +local bxor = bit.bxor; +local lshift = bit.lshift; +local rshift = bit.rshift; + +local t_concat = table.concat; +local s_byte = string.byte; +local s_char= string.char; +local s_sub = string.sub; + +local function read_uint16be(str, pos) + local l1, l2 = s_byte(str, pos, pos+1); + return l1*256 + l2; +end +-- FIXME: this may lose precision +local function read_uint64be(str, pos) + local l1, l2, l3, l4, l5, l6, l7, l8 = s_byte(str, pos, pos+7); + return lshift(l1, 56) + lshift(l2, 48) + lshift(l3, 40) + lshift(l4, 32) + + lshift(l5, 24) + lshift(l6, 16) + lshift(l7, 8) + l8; +end +local function pack_uint16be(x) + return s_char(rshift(x, 8), band(x, 0xFF)); +end +local function get_byte(x, n) + return band(rshift(x, n), 0xFF); +end +local function pack_uint64be(x) + return s_char(rshift(x, 56), get_byte(x, 48), get_byte(x, 40), get_byte(x, 32), + get_byte(x, 24), get_byte(x, 16), get_byte(x, 8), band(x, 0xFF)); +end + +local function parse_frame_header(frame) + if #frame < 2 then return; end + + local byte1, byte2 = s_byte(frame, 1, 2); + local result = { + FIN = band(byte1, 0x80) > 0; + RSV1 = band(byte1, 0x40) > 0; + RSV2 = band(byte1, 0x20) > 0; + RSV3 = band(byte1, 0x10) > 0; + opcode = band(byte1, 0x0F); + + MASK = band(byte2, 0x80) > 0; + length = band(byte2, 0x7F); + }; + + local length_bytes = 0; + if result.length == 126 then + length_bytes = 2; + elseif result.length == 127 then + length_bytes = 8; + end + + local header_length = 2 + length_bytes + (result.MASK and 4 or 0); + if #frame < header_length then return; end + + if length_bytes == 2 then + result.length = read_uint16be(frame, 3); + elseif length_bytes == 8 then + result.length = read_uint64be(frame, 3); + end + + if result.MASK then + result.key = { s_byte(frame, length_bytes+3, length_bytes+6) }; + end + + return result, header_length; +end + +-- XORs the string `str` with the array of bytes `key` +-- TODO: optimize +local function apply_mask(str, key, from, to) + from = from or 1 + if from < 0 then from = #str + from + 1 end -- negative indicies + to = to or #str + if to < 0 then to = #str + to + 1 end -- negative indicies + local key_len = #key + local counter = 0; + local data = {}; + for i = from, to do + local key_index = counter%key_len + 1; + counter = counter + 1; + data[counter] = s_char(bxor(key[key_index], s_byte(str, i))); + end + return t_concat(data); +end + +local function parse_frame_body(frame, header, pos) + if header.MASK then + return apply_mask(frame, header.key, pos, pos + header.length - 1); + else + return frame:sub(pos, pos + header.length - 1); + end +end + +local function parse_frame(frame) + local result, pos = parse_frame_header(frame); + if result == nil or #frame < (pos + result.length) then return; end + result.data = parse_frame_body(frame, result, pos+1); + return result, pos + result.length; +end + +local function build_frame(desc) + local data = desc.data or ""; + + assert(desc.opcode and desc.opcode >= 0 and desc.opcode <= 0xF, "Invalid WebSocket opcode"); + if desc.opcode >= 0x8 then + -- RFC 6455 5.5 + assert(#data <= 125, "WebSocket control frames MUST have a payload length of 125 bytes or less."); + end + + local b1 = bor(desc.opcode, + desc.FIN and 0x80 or 0, + desc.RSV1 and 0x40 or 0, + desc.RSV2 and 0x20 or 0, + desc.RSV3 and 0x10 or 0); + + local b2 = #data; + local length_extra; + if b2 <= 125 then -- 7-bit length + length_extra = ""; + elseif b2 <= 0xFFFF then -- 2-byte length + b2 = 126; + length_extra = pack_uint16be(#data); + else -- 8-byte length + b2 = 127; + length_extra = pack_uint64be(#data); + end + + local key = "" + if desc.MASK then + local key_a = desc.key + if key_a then + key = s_char(unpack(key_a, 1, 4)); + else + key = random_bytes(4); + key_a = {key:byte(1,4)}; + end + b2 = bor(b2, 0x80); + data = apply_mask(data, key_a); + end + + return s_char(b1, b2) .. length_extra .. key .. data +end + +local function parse_close(data) + local code, message + if #data >= 2 then + code = read_uint16be(data, 1); + if #data > 2 then + message = s_sub(data, 3); + end + end + return code, message +end + +local function build_close(code, message) + local data = pack_uint16be(code); + if message then + assert(#message<=123, "Close reason must be <=123 bytes"); + data = data .. message; + end + return build_frame({ + opcode = 0x8; + FIN = true; + MASK = true; + data = data; + }); +end + +return { + parse_header = parse_frame_header; + parse_body = parse_frame_body; + parse = parse_frame; + build = build_frame; + parse_close = parse_close; + build_close = build_close; +}; |