[webkit-dev] Networking proxy on iOS

Sun May 22 03:14:30 PDT 2016

> It’s not yet clear what the ideal architecture is, which is one of the
reasons why the mentioned issued remains unresolved.

What are the other reasons?
Are there any reasons that block us from discussing the right architecture?
I'd like to start working on a patch, but I need directions from you.

I'd like to come up with some sort of a plan for this as well. Since the
desired approach sounds complicated, it would be nice to split it as a
series of patches where each patch is committed separately and improves the
feature towards the goal.

On Sun, May 22, 2016 at 6:16 AM, Brady Eidson <beidson at apple.com> wrote:

>
> On May 21, 2016, at 2:05 PM, Daniel Olegovich Lazarenko <danielo at opera.com>
> wrote:
>
> > We are exploring ways to restore that full functionality -
> https://bugs.webkit.org/show_bug.cgi?id=138169
>
> Having custom scheme protocols is important to me too. I didn't know that
> it is broken with WKWebView. Do you know what exactly is broken?
>
>
> From most developer’s perspective, what is broken is that their
> NSURLProtocol they can register in their “UI Process” that used to work in
> WK1 views no longer has any effect in WK2.
>
>
> I thought that if you call [WKBrowsingContextController
> registerSchemeForCustomProtocol:] with your scheme, then it works. When I
> checked last (a year ago) it was implemented in a way that the WebProcess/
> NetworkingProcess would pass a message to UIProcess, and handle the
> network request in the UIProcess. Did it change?
>
>
> That did not change.
>
> But that mechanism was never API, and even as SPI it is formally
> deprecated.
>
> Assuming that registerSchemeForCustomProtocol still works the same way,
> you basically state that you dislike the current solution (that does the
> work in the UIProcess), and want to have a different architecture.
>
> For custom networking or proxying you have to run the app-provided code.
> The basic strategy I proposed was to run it in the app process (i.e.
> UIProcess). Since you don't want any networking in UIProcess, it means that
> the app needs to spawn a dedicated process to do custom networking. This
> process would run app-specific code (including NSURLProtocol-s), and
> communicate by IPC with the NetworkingProcess. Is this a kind of
> architecture you would like to have?
>
>
> It’s not yet clear what the ideal architecture is, which is one of the
> reasons why the mentioned issued remains unresolved.
>
> Thanks,
> ~Brady
>
>
>
>
> On Fri, May 20, 2016 at 5:58 PM, Brady Eidson <beidson at apple.com> wrote:
>
>>
>> On May 20, 2016, at 2:30 AM, Daniel Olegovich Lazarenko <
>> danielo at opera.com> wrote:
>>
>> Thank you for such a fast reply. That is amazing! :)
>> Back to questions...
>>
>> > Are you primarily focused on a custom networking layer (e.g. your own
>> HTTP implementation?),
>> > or with custom protocol handling for non-http protocols?
>>
>> I'm primarily concerned about HTTP and friends (HTTPS, SPDY, HTTP2), but
>> if there are any other widely used protocols that's also interesting. FTP
>> support is not interesting for me. Do you have any other specific things in
>> mind?
>>
>> If there's a custom proprietary protocol that people handle in the app
>> with their own code, for example, acme://acme.com:1234, then proxying
>> this thing is not very interesting to me, because it's very easy to proxy
>> my own protocol handled by my own code. There's a case when "acme" is
>> provided by some 3rd party, and the app author doesn't have the processing
>> code. In such case it might be interesting to proxy it as well, but then
>> again, I'm asking for a concrete example of such protocol (in WebKit
>> context).
>>
>>
>> In a WebKit1 app (WebView on Mac, UIWebView on iOS), app authors were
>> able to use NSURLProtocol to override any scheme they wished.
>>
>> While some such as yourself might’ve used it to override http from the
>> default handling, *many more* used it to implement custom protocols. e.g. “
>> acme://my-app-specific-url”
>>
>> We are exploring ways to restore that full functionality -
>> https://bugs.webkit.org/show_bug.cgi?id=138169
>>
>> > You seem to dismiss the Networking process’ crash recovery aspect.
>> > "because in practice we know that most of the crashes happen in the
>> WebProcess parts”.
>> > I’m curious what data you’re using to make that claim?
>>
>> Well, I'm not dismissing it, it's definitely a trade off that an app
>> author will make by choosing to enable this option.
>> The data comes from our web browser apps. We certainly see networking
>> faults, but in total it was usually a minor part of all the WebKit crashes.
>> To not sound subjective, I've looked through our current app version, which
>> already has enough data to judge, and in the top WebKit crashes there are
>> none in the network code. Most are crashes in JavaScriptCore, DOM and
>> graphics subsystems. This is the experience we have over many versions and
>> years of service. I might be able to show you the data in private if you
>> want, although I'm sure that you have your own crash analysis system with
>> much more data.
>>
>>
>> Without getting in to specifics, the NetworkingProcess does crash.
>>
>> And while the WebContent process does crash way more, it usually only
>> effects that one web page.
>>
>> If networking code was back inside the UI Process, and it crashed, that
>> takes down the whole browser.
>>
>> Doing so would be reverting towards the single process architecture of
>> yesteryear, not progressing away from it.
>>
>> Let's discuss the sandboxing a little bit. First of all, and correct me
>> if I'm wrong: I thought that there's no 3rd party code execution in the
>> networking process,
>>
>>
>> Currently, there is no 3rd party code execution in the networking process.
>>
>> and all the JS execution happens inside the WebProcess.
>>
>>
>> That’s correct, but I’m not necessarily talking about JS.
>>
>> The code that we want to run is our own code that we control that we
>> implement in a safe and secure manner.
>>
>>
>> The 1st party is “the Modern WebKit framework.”
>> The 3rd party is “the application’s code, as well as stuff downloaded
>> from the Internet.
>>
>> In this sense it's no less secure.
>>
>>
>> A single process app that does whatever it wants with the networking
>> stack is less secure to the user than a multi-process app that has well
>> defined behavior inside certain sandboxed parts of the app.
>>
>> In the end we are always protected by the iOS/Mac sandbox.
>>
>>
>> For a WKWebView app on iOS, while the app itself is sandboxed, the
>> Networking process is *much more* sandboxed.
>>
>> Maybe I'm wrong about JS here, or do you have some other use case in
>> mind?
>>
>>
>> I think you misunderstood that I was talking about the native app code
>> that is a 3rd party client to the WebKit framework.
>>
>> But, there is an important JS aspect to this; Since there is messaging
>> between the WebContent process and the Networking process, a vulnerability
>> in the WebContent process can turn into a “remote exploit” of the
>> Networking process.
>> Therefore it is beneficial to have the Networking process tightened down
>> as much as possible.
>>
>> ---
>>
>> There’s another very important reason why offering a
>> “networking-in-UI-process mode” is not appealing. From a project
>> maintenance standpoint, the more configurations we have the harder it is to
>> test and develop within the project.
>>
>> Adding this “optional” networking mode would double certain testing
>> matrices and make development in this area (which there has been a lot of
>> lately) more difficult.
>>
>> > Debugging the multi process architecture of WebKit2
>> > has not gotten any harder in years, active developers have all
>> adapted,
>> > and new developers tend to pick it up pretty quickly. This is not a
>> useful point.
>>
>> I'm sorry that you are rejecting this. Of course you can adapt to that,
>> but it inevitably has a steeper learning curve, and takes longer time. Many
>> app developers come from a single-process background and find
>> multi-process debugging much harder. Often it's a real challenge to
>> understand what's going on. I'm sure that you in your team have multiple
>> stories that show how non-trivial it is, and tricks about dealing with it.
>> Nevertheless, I agree, it's not a decisive point.
>>
>>
>> AFAIK, we haven’t had a potential contributor to the WebKit Open Source
>> project decide to not contribute because of the multi-process architecture.
>>
>> But, regardless, the MP architecture is primarily how well WebKit works
>> as a browser engine for the user, and not about how easy it is for
>> single-process-only developers to contribute.
>>
>> Such developers can still actively contribute to the cross platform code
>> of the project (WebCore) in single process mode using MiniBrowser or
>> DumpRenderTree.
>>
>> Thanks,
>> ~Brady
>>
>>
>>
>>
>> On Thu, May 19, 2016 at 6:43 PM, Brady Eidson <beidson at apple.com> wrote:
>>
>>>
>>> On May 19, 2016, at 8:41 AM, Daniel Olegovich Lazarenko <
>>> danielo at opera.com> wrote:
>>>
>>> I'd like to ask your for advice about implementation of a custom
>>> networking layer
>>>
>>>
>>> Are you primarily focused on a custom networking layer (e.g. your own
>>> HTTP implementation?), or with custom protocol handling for non-http
>>> protocols?
>>>
>>> ...with WKWebView on iOS.
>>>
>>>
>>> WKWebView is an API that ships on both OS X and iOS. When a design
>>> aspect of it affects both platforms (such as the networking behavior), we
>>> must consider both platforms.
>>>
>>> Our current solution is based on NSURLProtocol, and the issues we had
>>> with it in 2014 are unresolved:
>>> https://bugs.webkit.org/show_bug.cgi?id=137302
>>> https://bugs.webkit.org/show_bug.cgi?id=138131
>>>
>>> It was kind of a shoehorn hack, and so it was rejected by Benjamin
>>> Poulain and Alexey Proskuryakov among other reviewers.
>>>
>>>
>>> I’m not sure it’s useful for WebKit to spend energy testing and
>>> maintaining a mechanism that *only* allows for HTTP-handling replacement
>>> and doesn’t also allow for the oft-requested feature of custom protocol
>>> handling.
>>>
>>> Now I'm again looking for a better solution.
>>> I'd really like to discuss it with somebody responsible,
>>>
>>>
>>> There is no single person responsible; the project works largely on
>>> consensus. When dealing with platform specific concerns such as this, it
>>> works on consensus of the platform owners.
>>>
>>> That said, I have been the primary caretaker of the Networking process
>>> since it’s inception, as well one of the primary caretakers of Mac/iOS
>>> networking in general for many years, so I’ll share my thoughts below.
>>>
>>> There's currently 2 solutions I'm weighting:
>>>
>>>    1. Pass and use NetworkProcessCreationParameters.httpProxy to
>>>    NSURLSessionConfiguration (in NetworkSession and maybe other places). The
>>>    httpProxy solution is easy to implement and would look clean design-wise.
>>>    It would let us spawn an HTTP proxy on localhost and filter the traffic
>>>    there. There might be some complications, because it's not fully
>>>    transparent to the client side. For example HTTPS will have issues. All in
>>>    all this could be a fine short-term solution.
>>>
>>> While ToT WebKit contains an NSURLSession-based networking
>>> implementation for Mac/iOS, it also still contains an NSURLConnection
>>> implementation, which is unaffected by NSURLSession considerations.
>>>
>>> That a solution doesn’t work on all supported platforms is not a deal
>>> breaker, but it certainly makes it less interesting than one that does.
>>>
>>> HTTPS losing reliability is likely an unacceptable red flag.
>>>
>>> I’m not sure it’s useful for WebKit to spend energy testing and
>>> maintaining a mechanism that *only* allows for HTTP-handling replacement
>>> and doesn’t also allow for the oft-requested feature of custom protocol
>>> handling.
>>>
>>>
>>>    1. Add a new mode to the NetworkProcess, which would do all
>>>    networking in UIProcess (instead of spawning a new process). A mode would
>>>    be optional and controlled with some configuration setting (or
>>>    NSUserDefaults).
>>>
>>> The UIProcess solution is harder to implement, and it will affect more
>>> code. It is somewhat controversial. One of the reasons of splitting out a
>>> NetworkProcess was to have it respawn after crashes. Nevertheless we can
>>> take this risk, because in practice we know that most of the crashes happen
>>> in the WebProcess parts.
>>>
>>>
>>> You seem to dismiss the Networking process’ crash recovery aspect.
>>> "because in practice we know that most of the crashes happen in the
>>> WebProcess parts”.  I’m curious what data you’re using to make that claim?
>>>
>>>  I don't see any other significant downsides of having the UIProcess
>>> handling networking.
>>>
>>>
>>> The Networking process provides significant benefit unrelated to crash
>>> recovery that should not be abandoned for convenience sake. e.g. Sandboxing.
>>>
>>> Especially when moving the networking to the UI process would also end
>>> up moving 3rd party code execution into the UI process, this seems like an
>>> unacceptable regression.
>>>
>>> In addition it can simplify the NetworkProcess debugging.
>>>
>>>
>>> Debugging the multi process architecture of WebKit2 has not gotten any
>>> harder in years, active developers have all adapted, and new developers
>>> tend to pick it up pretty quickly. This is not a useful point.
>>>
>>> Thanks,
>>> ~Brady
>>>
>>>
>>
>>
>
>
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