File

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−-- Prosody IM
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−-- Copyright (C) 2012 Florian Zeitz
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−-- Copyright (C) 2014 Daurnimator
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−--
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−-- This project is MIT/X11 licensed. Please see the
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−-- COPYING file in the source package for more information.
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−--
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−
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−local softreq = require "util.dependencies".softreq;
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−local random_bytes = require "util.random".bytes;
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−
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−local bit = assert(softreq"bit" or softreq"bit32",
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−	"No bit module found. See https://prosody.im/doc/depends#bitop");
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−local band = bit.band;
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−local bor = bit.bor;
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−local bxor = bit.bxor;
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−local lshift = bit.lshift;
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−local rshift = bit.rshift;
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−
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−local t_concat = table.concat;
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−local s_byte = string.byte;
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−local s_char= string.char;
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−local s_sub = string.sub;
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−local s_pack = string.pack;
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−local s_unpack = string.unpack;
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−
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−if not s_pack and softreq"struct" then
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−	s_pack = softreq"struct".pack;
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−	s_unpack = softreq"struct".unpack;
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−end
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−
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−local function read_uint16be(str, pos)
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−	local l1, l2 = s_byte(str, pos, pos+1);
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−	return l1*256 + l2;
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−end
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−-- FIXME: this may lose precision
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−local function read_uint64be(str, pos)
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−	local l1, l2, l3, l4, l5, l6, l7, l8 = s_byte(str, pos, pos+7);
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−	local h = lshift(l1, 24) + lshift(l2, 16) + lshift(l3, 8) + l4;
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−	local l = lshift(l5, 24) + lshift(l6, 16) + lshift(l7, 8) + l8;
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−	return h * 2^32 + l;
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−end
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−local function pack_uint16be(x)
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−	return s_char(rshift(x, 8), band(x, 0xFF));
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−end
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−local function get_byte(x, n)
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−	return band(rshift(x, n), 0xFF);
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−end
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−local function pack_uint64be(x)
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−	local h = band(x / 2^32, 2^32-1);
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−	return s_char(get_byte(h, 24), get_byte(h, 16), get_byte(h, 8), band(h, 0xFF),
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−		get_byte(x, 24), get_byte(x, 16), get_byte(x, 8), band(x, 0xFF));
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−end
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−
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−if s_pack then
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−	function pack_uint16be(x)
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−		return s_pack(">I2", x);
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−	end
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−	function pack_uint64be(x)
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−		return s_pack(">I8", x);
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−	end
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−end
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−
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−if s_unpack then
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−	function read_uint16be(str, pos)
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−		return s_unpack(">I2", str, pos);
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−	end
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−	function read_uint64be(str, pos)
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−		return s_unpack(">I8", str, pos);
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−	end
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−end
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−
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−local function parse_frame_header(frame)
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−	if #frame < 2 then return; end
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−
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−	local byte1, byte2 = s_byte(frame, 1, 2);
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−	local result = {
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−		FIN = band(byte1, 0x80) > 0;
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−		RSV1 = band(byte1, 0x40) > 0;
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−		RSV2 = band(byte1, 0x20) > 0;
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−		RSV3 = band(byte1, 0x10) > 0;
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−		opcode = band(byte1, 0x0F);
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−
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−		MASK = band(byte2, 0x80) > 0;
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−		length = band(byte2, 0x7F);
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−	};
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−
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−	local length_bytes = 0;
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−	if result.length == 126 then
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−		length_bytes = 2;
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−	elseif result.length == 127 then
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−		length_bytes = 8;
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−	end
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−
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−	local header_length = 2 + length_bytes + (result.MASK and 4 or 0);
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−	if #frame < header_length then return; end
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−
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−	if length_bytes == 2 then
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−		result.length = read_uint16be(frame, 3);
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−	elseif length_bytes == 8 then
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−		result.length = read_uint64be(frame, 3);
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−	end
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−
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−	if result.MASK then
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−		result.key = { s_byte(frame, length_bytes+3, length_bytes+6) };
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−	end
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−
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−	return result, header_length;
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−end
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−
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−-- XORs the string `str` with the array of bytes `key`
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−-- TODO: optimize
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−local function apply_mask(str, key, from, to)
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−	from = from or 1
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−	if from < 0 then from = #str + from + 1 end -- negative indicies
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−	to = to or #str
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−	if to < 0 then to = #str + to + 1 end -- negative indicies
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−	local key_len = #key
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−	local counter = 0;
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−	local data = {};
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−	for i = from, to do
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−		local key_index = counter%key_len + 1;
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−		counter = counter + 1;
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−		data[counter] = s_char(bxor(key[key_index], s_byte(str, i)));
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−	end
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−	return t_concat(data);
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−end
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−
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−local function parse_frame_body(frame, header, pos)
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−	if header.MASK then
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−		return apply_mask(frame, header.key, pos, pos + header.length - 1);
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−	else
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−		return frame:sub(pos, pos + header.length - 1);
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−	end
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−end
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−
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−local function parse_frame(frame)
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−	local result, pos = parse_frame_header(frame);
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−	if result == nil or #frame < (pos + result.length) then return; end
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−	result.data = parse_frame_body(frame, result, pos+1);
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−	return result, pos + result.length;
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−end
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−
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−local function build_frame(desc)
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−	local data = desc.data or "";
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−
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−	assert(desc.opcode and desc.opcode >= 0 and desc.opcode <= 0xF, "Invalid WebSocket opcode");
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−	if desc.opcode >= 0x8 then
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−		-- RFC 6455 5.5
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−		assert(#data <= 125, "WebSocket control frames MUST have a payload length of 125 bytes or less.");
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−	end
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−
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−	local b1 = bor(desc.opcode,
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−		desc.FIN and 0x80 or 0,
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−		desc.RSV1 and 0x40 or 0,
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−		desc.RSV2 and 0x20 or 0,
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−		desc.RSV3 and 0x10 or 0);
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−
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−	local b2 = #data;
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−	local length_extra;
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−	if b2 <= 125 then -- 7-bit length
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−		length_extra = "";
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−	elseif b2 <= 0xFFFF then -- 2-byte length
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−		b2 = 126;
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−		length_extra = pack_uint16be(#data);
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−	else -- 8-byte length
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−		b2 = 127;
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−		length_extra = pack_uint64be(#data);
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−	end
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−
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−	local key = ""
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−	if desc.MASK then
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−		local key_a = desc.key
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−		if key_a then
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−			key = s_char(unpack(key_a, 1, 4));
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−		else
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−			key = random_bytes(4);
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−			key_a = {key:byte(1,4)};
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−		end
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−		b2 = bor(b2, 0x80);
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−		data = apply_mask(data, key_a);
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−	end
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−
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−	return s_char(b1, b2) .. length_extra .. key .. data
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−end
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−
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−local function parse_close(data)
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−	local code, message
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−	if #data >= 2 then
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−		code = read_uint16be(data, 1);
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−		if #data > 2 then
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−			message = s_sub(data, 3);
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−		end
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−	end
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−	return code, message
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−end
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−
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−local function build_close(code, message, mask)
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−	local data = pack_uint16be(code);
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−	if message then
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−		assert(#message<=123, "Close reason must be <=123 bytes");
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−		data = data .. message;
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−	end
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−	return build_frame({
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−		opcode = 0x8;
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−		FIN = true;
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−		MASK = mask;
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−		data = data;
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−	});
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−end
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−
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−return {
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−	parse_header = parse_frame_header;
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−	parse_body = parse_frame_body;
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−	parse = parse_frame;
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−	build = build_frame;
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−	parse_close = parse_close;
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−	build_close = build_close;
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−};