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;
+};