[whatwg] TCPConnection feedback

Shannon shannon at arc.net.au
Wed Jun 18 05:50:00 PDT 2008

Frode Børli wrote:
> XMLHttpRequest only allows connections to the origin server ip of the
> script that created the object. If a TCPConnection is supposed to be
> able to connect to other services, then some sort of mechanism must be
> implemented so that the targeted web server must perform some sort of
> approval. The method of approval must be engineered in such a way that
> approval process itself cannot be the target of the dos attack. I can
> imagine something implemented on the DNS servers and then some digital
> signing of the script using public/private key certificates.
Using DNS is an excellent idea, though I would debate whether the 
certificate is needed in addition the DNS record. Perhaps the DNS record 
could simply list domains authorised to provide scripted access. The 
distributed nature and general robustness of DNS servers provides the 
most solid protection against denial of service and brute-force cracking 
which are the primary concerns here. Access-control should probably be 
handled by the hosts usual firewall and authentication methods which is 
trivial once the unauthorised redirect issue is dealt with.

The biggest issue I see is that most UAs are probably not wired to read 
DNS records directly. This means adding DNS access and parsing libraries 
for this one feature. Having said that I can see a whole range of 
security issues that could be addressed by DNS access so maybe this is 
something that HTML5 could address as a more general feature. One 
feature that comes to mind would be to advertise expected server outages 
or /.'ing via DNS so the UAs could tell the user "Hey, this site might 
not respond so maybe come back later".

It is worth considering allowing scripts to access devices without said 
DNS rules but with a big fat UA warning, requiring user approval. 
Something like "This site is attempting to access a remote service or 
device at the address (POP3). This could be part of a 
legitimate service but may also be an attempt to perform a malicious 
task. If you do not trust this site you should say no here.". This would 
address the needs of private networks and home appliances that wish to 
utilise TCPConnection services without having the desire or ability to 
mess with DNS zone files.

> The protocol should not require any data (not even hello - it should
> function as an ordinary TCPConnection similar to implementations in
> java, c# or any other major programming language. If not, it should be
> called something else - as it is not a TCP connection.
I agree completely. Just providing async HTTP is a weak use case 
compared to allowing client-side access to millions of existing 
(opted-in) services and gadgets.


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