- From: Sergio Garcia Murillo <sergio.garcia.murillo@gmail.com>
- Date: Mon, 15 Jan 2018 16:16:24 +0100
- To: Byron Campen <docfaraday@gmail.com>, Martin Thomson <martin.thomson@gmail.com>, T H Panton <thp@westhawk.co.uk>
- Cc: "public-webrtc@w3.org" <public-webrtc@w3.org>, IƱaki Baz Castillo <ibc@aliax.net>, Cullen Jennings <fluffy@iii.ca>
- Message-ID: <069d71d4-0292-410f-d7cc-436d3c65c3f5@gmail.com>
Well, I don't agree with how that statement is written (although I think we share the same idea) WebRTC must be *disabled* by default if CSP is in place. Wether it is a simple rule or multiple complex rules to *enable* it back, won't affect normal web developers. Best regards Sergio On 15/01/2018 15:19, Byron Campen wrote: > Agreed. All of this hullabaloo started with the publication of > this article > <https://hackernoon.com/im-harvesting-credit-card-numbers-and-passwords-from-your-site-here-s-how-9a8cb347c5b5>, > one of the central points of which was "CSP won't stop me, because CSP > is frequently misconfigured". Let's make it as easy as possible for > web developers to avoid this problem, and refine things later as needed. > > On 1/14/18 9:33 PM, Martin Thomson wrote: >> A simple rule prohibiting >> webrtc entire seems more operationally feasible. >> >> >> On Fri, Jan 12, 2018 at 10:01 PM, T H Panton<thp@westhawk.co.uk> wrote: >>> In the call yesterday, I said I'd try and summarize the concerns that have been raised about 'Drive-by webRTC CSP' attacks. >>> >>> Content Security Policy on web pages allows a site developer to proscribe what their page can do. >>> This is intended to mitigate the risks of XSS and other injection attacks. >>> >>> https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy/connect-src >>> >>> This reduces exposure to included 3rd party scripts being tampered with at source >>> e.g. if someone hackshttps://webrtc.github.io/adapter/adapter-latest.js >>> - the page may not function correctly, but it should not be able to send sensitive >>> data to domains that aren't whitelisted in the CSP connect-src header. >>> >>> This prevents a web-font supplier from capturing the credit card data from your >>> e-commerce site shopping forms. >>> >>> The connect-src explicitly covers websockets. It does not mention DataChannels or webRTC. >>> >>> In principle you might not think that matters, since in order to set up a data-channel >>> you need to perform an SDP exchange, and that SDP exchange would have to go through >>> a whitelisted server. >>> >>> It turns out in the case of ice-lite the browser does not verify that the remote party has >>> ever seen it's SDP - ICE responses do not require the requester's ufrag or pass. >>> This means that the malicious javascript does not need to send an answer to a >>> cooperating server. >>> >>> So it would be possible to bury static SDP for an ice-lite offer in malicious javascript. >>> The offer would point to a malicious server that implemented ice-lite on a fixed port >>> (for example) and accepted data channels without checking the DTLS fingerprint. >>> >>> The javascript would apply this to a peerconnection and drop the generated answer in the >>> bit-bucket. >>> >>> The malicious javascript can now inspect the page DOM and send all the form values it >>> finds over a datachannel to the malicious server. Despite the fact that the conscientious developer >>> had configured connect-src to mitigate this risk. >>> >>> At the heart of this is that ice-lite breaks the conceptual linkage between the 5 tuple and the >>> page origin. >>> >>> Proposal: >>> a) Ban ice-lite on pages with any CSP set >>> c) add a allow-ice-lite CSP >>> b) add a CSP turn-servers whitelist (to prevent leakage via the credentials) >>> c) test plain ICE to make sure it fails if the far side sends no valid requests. >>> d) ensure that any new ICE api's don't make this mistake (worse) >>> >>> Thanks toibc@aliax.net for starting the discussion andsergio.garcia.murillo@gmail.com for pointing me at CSP connect-src: >>> https://twitter.com/ibc_tw/status/949993145978245120 >>> >>> P.S. >>> As you will see in the twitter thread, this isn't specific to the datachannel - one can exfiltrate data over DTMF or G711 perfectly easily. >>> >>> Tim. > >
Received on Monday, 15 January 2018 15:16:50 UTC