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-- 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
-- TODO: 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 sm(x, n)
return band(rshift(x, n), 0xFF);
end
local function pack_uint64be(x)
return s_char(rshift(x, 56), sm(x, 48), sm(x, 40), sm(x, 32),
sm(x, 24), sm(x, 16), sm(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, pos+1, pos+4) };
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;
local length_extra
if #data <= 125 then -- 7-bit length
b2 = #data;
length_extra = "";
elseif #data <= 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;
};
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