Re: What is missing for building "real" services?

And that's fine, so long as you respect the Same Origin policy without 
exceptions, right?


On 09/01/2014 12:45 AM, Eric Rescorla wrote:
> People also want to be able to share the browser.
> -Ekr
> On Wed, Jan 8, 2014 at 9:39 PM, cowwoc <> wrote:
>> Okay, so here is my second attempt at this:
>> We should be able to share any part of the display that the application does
>> not control. Meaning, the webapp might allow users to share the contents of
>> Excel so long as it has no control over what gets displayed by Excel.
>> Similarly, it should be allowed to share any browser tab so long as it plays
>> within its own host/origin.
>> Assuming that co-browsing is a non-goal for now, is the above (read-only
>> screen sharing) safe from a security point of view?
>> Gili
>> On 09/01/2014 12:19 AM, Alex Gouaillard wrote:
>>> importance of the interest:
>>> We, and the 50 Millions pool of clients we already serve, want this
>>> scenario (full screen sharing), even though we would prefer the
>>> version where only the display of a given (potentially masked on the
>>> origin computer own desktop) window is shared. I cannot speak for
>>> others, but I remember seeing quite a few hints of interest on the
>>> mailing list, and some experiments with chrome screen sharing seem
>>> pretty popular out there. Some of the video conferencing product we
>>> used to sell (*cough*vidyo*cough*) and others already propose this
>>> functionality and it was the main sales point. Many of
>>> not-yet-customers have expressed utmost interest in the use case
>>> described below for either education purpose, or in hospital
>>> environment (regulation are different for tablets, and iPad with a
>>> specific casing are allow in surgery. What was only prototyping in
>>> Research Units when I was at Harvard Medical School (2008-ish) is now
>>> a reality in "standard" hospital and radiology Units as well.
>>> use case / scenario:
>>> The most usual case is sharing a presentation, table, or text document
>>> as a stream in a multi stream (document display + self video + self
>>> audio + potentially other stuff) call. Screen sharing allows to share
>>> the document, but then, you don't see yourself. Sharing separate
>>> window content (as in desktop composition's window), would allow a
>>> better presentation experience for the sender, who who be able to see
>>> the document he is sending (as a local stream), and himself, basically
>>> mirroring what the remote peer could see.
>>> On Thu, Jan 9, 2014 at 12:02 PM, Eric Rescorla <> wrote:
>>>> On Wed, Jan 8, 2014 at 7:52 PM, cowwoc <> wrote:
>>>>> Remind me again, what was wrong with this approach?
>>>> It doesn't enable essentially any screen sharing scenario that
>>>> people want.
>>>> -Ekr
>>>>> Enable screensharing without a flag/plugin.
>>>>> Prompt the user for permission.
>>>>> Allow screensharing for a single browser tab (can't capture the general
>>>>> screen or foreign processes).
>>>>> Prevent pages that use screensharing from issuing requests to foreign
>>>>> hosts
>>>>> (i.e. Same Origin policy minus any exceptions).
>>>>> Lets start with something that is fairly restrictive (but doesn't
>>>>> require a
>>>>> flag/plugin which kills traction), enable *some* use-cases, and built up
>>>>> from there.
>>>>> Gili
>>>>> On 08/01/2014 9:03 PM, Eric Rescorla wrote:
>>>>> On Wed, Jan 8, 2014 at 5:53 PM, <>
>>>>> wrote:
>>>>> I'm not ccomparing both in the way I accept whatever of both, but
>>>>> instead in
>>>>> the way both (plugins and flags) are equally bad ideas. Screen and
>>>>> application sharing should be included and enabled on browsers by
>>>>> default,
>>>>> and not hidden behind a flag or whatever other method.
>>>>> For the reasons described in:
>>>>> The browser vendors don't think this is that great an idea.
>>>>> If you think that screen sharing should be available by default, you
>>>>> should perhaps suggest some security mechanisms which would
>>>>> make the threats described here less severe.
>>>>> -Ekr
>>>>> Send from my Samsung Galaxy Note II
>>>>> El 09/01/2014 02:42, "Alex Gouaillard" <>
>>>>> escribió:
>>>>> @ piranha.
>>>>> while I agree with you for social users and most of the population out
>>>>> there, the difference between clicking a flag and installing a plugin
>>>>> is the process required by IT teams to accept the product and deploy
>>>>> it in an enterprise environment. Everything needs to validated
>>>>> beforehand, including (especially?) plugins. They have a very long
>>>>> list of products to screen and maintain, and are very reluctant to add
>>>>> yet another one. Moreover, google's chrome start with a higher
>>>>> credibility than any small or medium sized company's plugin.
>>>>> On Thu, Jan 9, 2014 at 8:54 AM, Silvia Pfeiffer
>>>>> <> wrote:
>>>>> On Thu, Jan 9, 2014 at 10:10 AM, Randell Jesup <>
>>>>> wrote:
>>>>> On 1/7/2014 8:50 PM, Alexandre GOUAILLARD wrote:
>>>>> here are a few proposition on things that are really biting us, and how
>>>>> to
>>>>> (perhaps) make it easier:
>>>>> - bandwidth control
>>>>> 1. It seems that the number one sdp munging cause is the now infamous
>>>>> B=AS:
>>>>> line to put a cap on bandwidth. Since that capacity exists in the
>>>>> underlying
>>>>> code, it would be great to have an API that can help us put caps,
>>>>> either on
>>>>> each stream, and/or on the full call.
>>>>> yes.
>>>>> 2. I also see that there is a "auto-mute" feature being implemented
>>>>> that
>>>>> depend on an arbitrary threshold. It might be interested (but
>>>>> overkill?), to
>>>>> give user the capacity to set that limit (currently 50k I guess)
>>>>> somehow.
>>>>> Pointer to this auto-mute implemetation?
>>>>> 3. Additionally, and perhaps not unrelated, we would alike to be able
>>>>> to
>>>>> decide what happen when bandwidth goes down. Right now it feels like
>>>>> the
>>>>> video has the priority over the audio. We would like to be able to
>>>>> explicitly set the audio priority higher than the video in the
>>>>> underlying
>>>>> system, as opposed to implement a stats listener, which triggers
>>>>> re-negotiation (with the corresponding O/A delay) when bandwidth goes
>>>>> below
>>>>> a certain threshold.
>>>>> Right now they have the same "priority", but really audio is typically
>>>>> fixed, so the video reacts to changes in the apparent level of
>>>>> delay/buffering.  What you may be seeing is better (or less-obvious)
>>>>> error
>>>>> control and recovery in the video; the eye is often less sensitive to
>>>>> things
>>>>> like dropped frames than the ear.
>>>>> I'd love to see a trace/packet-capture/screen-scrape-recording where
>>>>> you see
>>>>> that apparent behavior.
>>>>> - call controls like mute / hold
>>>>> Right now, you can mute a local stream, but it does not seem to be
>>>>> possible
>>>>> to let the remote peers know about the stream being muted. We ended up
>>>>> implementing a specific off band message for that, but we believe that
>>>>> the
>>>>> stream/track could carry this information. This is more important for
>>>>> video
>>>>> than audio, as a muted video stream is displayed as a black square,
>>>>> while a
>>>>> muted audio as no audible consequence. We believe that this mute / hold
>>>>> scenario will be frequent enough, that we should have a standardized
>>>>> way of
>>>>> doing it, or interop will be very difficult.
>>>>> There is no underlying standard in IETF for communicating this; it's
>>>>> typically at the application level.  And while we don't have good ways
>>>>> in
>>>>> MediaStream to do this yet, I strongly prefer to send an fixed image
>>>>> when
>>>>> video-muted/holding.  Black is a bad choice....
>>>>> It would be nice if browsers sent an image, such as "video on hold" -
>>>>> just like they provide default 404 page renderings. This is a quality
>>>>> of implementation issue then. Maybe worth registering a bug on
>>>>> browsers. But also might be worth a note in the spec.
>>>>> - screen/application sharing
>>>>> We are aware of the security implications, but there is a very very
>>>>> strong
>>>>> demand for screen sharing. Beyond screen sharing, the capacity to share
>>>>> the
>>>>> displayed content of a given window of the desktop would due even
>>>>> better.
>>>>> Most of the time, users only want to display one document, and that
>>>>> would
>>>>> also reduce the security risk by not showing system trays.
>>>>> Collaboration
>>>>> (the ability to let the remote peer edit the document) would be even
>>>>> better,
>>>>> but we believe it to be outside of the scope of webRTC.
>>>>> yes, and dramatically more risky.  Screen-sharing and how to preserve
>>>>> privacy and security is a huge problem.  Right now the temporary kludge
>>>>> is
>>>>> to have the user whitelist services that can request it (via extensions
>>>>> typically)
>>>>> Yeah, I'm really unhappy about the screen sharing state of affairs,
>>>>> too. I would much prefer it became a standard browser feature.
>>>>> Cheers,
>>>>> Silvia.
>>>>>      Randell
>>>>> - NAT / Firewall penetration feedback - ICE process feedback
>>>>> Connectivity is a super super pain to debug, and the number one cause
>>>>> of
>>>>> concern.
>>>>> 1. The 30s time out on chrome generated candidate is biting a lot of
>>>>> people.
>>>>> The time out is fine, but there should be an error message that
>>>>> surfaces
>>>>> (see 5)
>>>>> 2. Turn server authentication failure does not generate an error, and
>>>>> should
>>>>> (see 5)
>>>>> 3. ICE state can stay stuck in "checking" forever even after all the
>>>>> candidate have been exhausted
>>>>> 4. Not all ICE states stated in the spec are implemented (completed?
>>>>> fail?)
>>>>> 5. It would due fantastic to be able to access the list of candidates,
>>>>> with
>>>>> their corresponding status (not checked, in use, failed, ….) with the
>>>>> cause
>>>>> for failure
>>>>> 6. In case of success, it would be great to know which candidate is
>>>>> being
>>>>> used (google does that with the googActive thingy) but also what is the
>>>>> type
>>>>> of the candidate. Right now, on client side, at best you have to go to
>>>>> chrome://webrtc-internals, get the active candidate, and look it up
>>>>> from the
>>>>> list of candidates. When you use a TURN server as a STUN server too,
>>>>> then
>>>>> the look up is not an isomorphism.
>>>>> right now, the only way to understand what's going on is to have a
>>>>> "weaponized" version of chrome, or a native app, that gives you access
>>>>> to
>>>>> the ICE stack, but we can not expect clients to deploy this, nor to
>>>>> automate
>>>>> it. Surfacing those in an API would allow one to:
>>>>> - adapt the connection strategy on the fly in an iterative fashion on
>>>>> client
>>>>> side.
>>>>> - report automatically the problems and allow remote debug of failed
>>>>> calls,
>>>>> On Tue, Jan 7, 2014 at 2:15 AM, Eric Rescorla <> wrote:
>>>>> On Mon, Jan 6, 2014 at 10:10 AM, <>
>>>>> wrote:
>>>>> That's not really going to work unless you basically are on a
>>>>> public
>>>>> IP address with no firewall. The issue here isn't the properties of
>>>>> PeerConnection but the basic way in which NAT traversal algorithms
>>>>> work.
>>>>> I know that the "IP and port" think would work due to NAT, but
>>>>> nothing
>>>>> prevent to just only need to exchange one endpoint connection data
>>>>> instead of both...
>>>>> I don't know what you are trying to say here.
>>>>> A large fraction of NATs use address/port dependent filtering which
>>>>> means that there needs to be an outgoing packet from each endpoint
>>>>> through their NAT to the other side's server reflexive IP in order to
>>>>> open the pinhole. And that means that each side needs to provide
>>>>> their address information over the signaling channel.
>>>>> I strongly recommend that you go read the ICE specification and
>>>>> understand the algorithms it describes. That should make clear
>>>>> why the communications patterns in WebRTC are the way they
>>>>> are.
>>>>> -Ekr
>>>>> --
>>>>> Randell Jesup -- rjesup a t mozilla d o t com

Received on Thursday, 9 January 2014 05:57:41 UTC