PageSigner/content/socket.js

//The only way to determine if the server is done sending data is to check that the receiving
//buffer has nothing but complete TLS records i.e. that there is no incomplete TLS records
//However it was observed that in cases when getting e.g. zip files, some servers first send HTTP header as one
//TLS record followed by the body as another record(s)
//That's why after receiving a complete TLS record we wait to get some more data
//This extra waiting must not be done for the handshake messages to avoid adding latency and having the handshake
//dropped by the server
function AbstractSocket(){};
AbstractSocket.prototype.recv = function(is_handshake){
	if (typeof(is_handshake) === 'undefined'){
		is_handshake = false;
	}
	var that = this;
	return new Promise(function(resolve, reject) {
		var startTime = new Date().getTime();
		var complete_records = [];
		var buf = [];		
		var resolved = false;
		
		var timer = setTimeout(function(){
			reject('recv: socket timed out');
			resolved = true;
		}, that.recv_timeout);
				
		var check = function(){
			//console.log('check()ing for more data', uid);
			if (resolved) {
				console.log('returning because resolved');
				return;
			}
			if (that.buffer.length === 0) {
				setTimeout(function(){check()}, 100);
				return;
			}
			console.log('new data in check', that.buffer.length);
			//else got new data
			buf = [].concat(buf, that.buffer);
			that.buffer = [];		
			var rv = check_complete_records(buf);
			complete_records = [].concat(complete_records, rv.comprecs);
			if (! rv.is_complete){
				console.log("check_complete_records failed", that.uid);
				buf = rv.incomprecs;
				setTimeout(function(){check()}, 100);
				return;
			}
			else {
				function finished_receiving(){
					clearTimeout(timer);
					console.log('recv promise resolving', that.uid);
					resolved = true;
					resolve(complete_records);
				};
				
				console.log("got complete records", that.uid);
				if (is_handshake){
					finished_receiving();
					return;
				}
				else {
					console.log("in recv waiting for an extra second", that.uid);
					buf = [];
					//give the server another second to send more data
					setTimeout(function(){
						if (that.buffer.length === 0){
							finished_receiving();
							return;
						}
						else {
							console.log('more data received after waiting for a second', that.uid);
							check();
						}
					},1000);
				}
			}
		};
		check();
	});
};


function check_complete_records(d){
    /*'''Given a response d from a server,
    we want to know if its contents represents
    a complete set of records, however many.'''
    */
    var complete_records = [];
    var incomplete_records = [];
    
    while(d){
		if (d.length < 5){
			return {'is_complete':false, 'comprecs':complete_records, 'incomprecs':d};
		}
		var l = ba2int(d.slice(3,5));
		if (d.length < (l+5)){
			return {'is_complete':false, 'comprecs':complete_records, 'incomprecs':d};
		}
		else if(d.length === (l+5)){
			return {'is_complete':true, 'comprecs':[].concat(complete_records, d)};
		}
		else {
			complete_records = [].concat(complete_records, d.slice(0, l+5));
			d = d.slice(l+5);
			continue;
		}
	}
}