Why the Nitro JavaScript Engine Isn’t Available to Other iOS Apps

http://daringfireball.net/2011/03/nitro_ios_43

by danilocampos • 15 years ago

65 79 15 years ago

aphyr• 15 years ago

Gruber: It is not an oversight or a bug, or the result of a single person at Apple wishing to hinder the performance of web apps.

Ars: Apple is aware of the issues, which are currently filed as bugs... are marked "not to be fixed by exec order,"

Well, this ought to be interesting.

danilocampos2• 15 years ago

I don't have any idea where the truth lies, here, but it's worth pulling the whole paragraph:

But according to Matt Asay, who is vice president of business development for mobile Web framework maker Strobe, Apple supposedly has no plans to fix them. Instead, they are marked "not to be fixed by exec order," suggesting that a higher up at Apple is preventing engineers from fixing the problems.

"Supposedly" and "suggested" let Ars weasel out of determining the truth of these assertions. Unless Apple has suddenly turned absurdly transparent, I have a hard time believing that this guy actually has any inside knowledge. On the other hand, he certainly has an incentive to bring pressure on Apple to make his business work better.

kanja• 15 years ago

AFAIK strobe is made up mostly of ex-apple people - furthermore, they knew about the "bugs" at least a month ago - Charles Jolley was talking about them at the most recent sproutcore nyc meetup. I don't think it's unreasonable to believe the truth of these assertions.

sammcd• 15 years ago

I don't see how these two points are mutually exclusive.

It very well could be an executive order not fix it because of the security issue.

Me1000• 15 years ago

The problem is that if the issue never gets fixed then native apps using a webview will never see this performance improvement. Which means in order to stay competitive Apple must continue to develop nitro. Which means they'll either develop nitro in parallel with the old JS engine, or they'll let the webview stagnate. Marking an issue as "dont fix" is very scary indeed for the web on iOS.

ra88it3• 15 years ago

If they're indeed marked "don't fix", that's probably because they are intentional. They aren't bugs.

stephenjudkins2• 15 years ago

I'm not sure why I read John Gruber anymore. I get my hopes up that perhaps I'll see some of the smart, incisive that I remember from years ago, but instead I see another pretty baseless apology for Apple's behavior. He may actually be correct in this case, but it's hard to take him seriously given that he seems to bend over backwards to interpret Apple's actions as charitably as possible. This post is certainly more defensible than his recent defense of Apple's 30% application revenue power-grab, but I am skeptical that it was written in any better faith.

With every thing he writes like this, he's behaving more like a fanboy and less like a reliable source of information. It's a bit sad.

tjogin• 15 years ago

So, even if he's right, he's wrong?

stephenjudkins2• 15 years ago

If I'm looking for the most reasonably explanation for Apple's behavior that still manages to cast them in a good light, I'll read Gruber. If I'm looking for the most reasonable possible explanation, full stop, I'll read elsewhere.

abraham• 15 years ago

A broken analog clock is only right twice a day.

spamizbad• 15 years ago

His reasoning seems shaky to me. Assuming this new JS engine is a security risk (it's not really, but lets pretend) you're not protecting anyone by making it Safari-only. It'd be like leaving all your ground-floor windows wide open, whilst locking your front and back doors in hopes that it will discourage burglars.

If the new JS engine is a security problem either fix it or remove it. Compromise helps no one.

bigiain• 15 years ago

I'm not sure which I'd rather see - Gruber being proved wrong (again), or a whole class of new remote "visit this site to jailbreak your iPhone" exploits...

rayiner• 15 years ago

It's not the JS engine that's the security problem. It's that the JS engine requires allowing apps to mark pages as executable. Executable pages opens up a whole another vector of attacks that have nothing to do with dangerous JS apps.

saurik5• 15 years ago

Apple can't turn on the ability to do executable, dynamically written to memory pages just for their library: they'd have to turn it on for the entire process, at which point you could also do crazy things like download native code and execute it, bypassing the entire concept of their "codesign" mechanism.

schrototo• 15 years ago

It's not the JavaScript engine that's the security risk, it's that in order to run the new JS engine, the app running it has to be able to execute code from writable memory. This is where the security risk lies, and it has always been forbidden, for all apps. Safari can get an exception, since Apple obviously trusts its own code not to be malicious. But 3rd party apps still won't be allowed to execute arbitrary code from memory, so any apps embedding a UIWebView to present a browser can't get the performance improvements of the new engine.

The only real question is why Apple's own app that's used to display those saved-to-home-screen webapps didn't get an exception alongside Safari. My guess is that the Nitro engine is built directly into Safari and that the UIWebView control (which is used by webapp viewer app) simply can't use it at all, regardless of ability to execute writable code. I'm sure this will change, either the viewer app will get rewritten, or UIWebView will get its own sandbox etc. They probably just didn't have the time to do that yet.

ryanisinallofus• 15 years ago

Man. I totally agree with you but you knew you were going to sacrifice some karma for saying this.

alanstorm• 15 years ago

You can't read Gruber in the same context you did five or six years ago. At this point he's an established journalisty blogger who depends on a network of sources, some of whom are within Apple Inc. That means, like most working journalists, he needs to consider the tone he takes with any individual article vs. what that article is going to do to his network of sources. The result is his writing still contains the smart incisive analysis it always has, but he also has to bend over backwards to make sure he's presenting what the the internal Apple take on the situation is. Compared to what you or I might say about Apple's behavior over a few beers, yeah, he comes off sounding like an apologist, but compare his coverage to what other in-the-tank tech writers say about Apple and he still comes off as an independent voice covering the company AND someone who can provide a level of context other people can't (details on Nitro's implementation)

panacea• 15 years ago

He had an explanation quite a while back (he kinda shifted gears) which I parsed as him saying he wasn't going to spend as much time being a link roll with snippets of commentary, into spending more time on his long-form pieces. (No idea what my search terms would be to find it)

Perhaps his best work was when he distilled the ecosystem down into a fantastic stream of links, a brilliant and hard-working focused aggregator/editor.

Bit more of a bloviating opinion columnist now-a-days. And I guess his biases are brought to the front more.

Understandable though. Everyone is converging on his range of primary sources and editorially crowd-sourcing it in realtime.

I'll still be frequenting his site. It's still quality. You just read with a bias-aware filter like you do any other news source.

xpaulbettsx• 15 years ago

100% agreed, his treatment of Apple here and in other articles reads like an Animal Farm'esque quote. If he wants to be Apple's PR department, that's fine, but his masquerade as "independent journalism" strikes me as pretty disingenuous. Which is a shame, because I think he's an very insightful writer who puts a lot of work into his articles.

'"Ah, that is different!" said Boxer. "If Comrade Napoleon says it, it must be right."'

jsz0• 15 years ago

No one knows for sure either way yet. So wouldn't most people's opinion on the subject be inherently lacking in the 'reliable source of information' department? He usually provides links to the other side of any given argument. Isn't it really up to the reader to decide what they believe? I tend to agree with him on this one because web apps on 4.2 weren't exactly impossibly slow and unusable. The performance increases in 4.3 are nice but it doesn't really make any huge difference to someone's ability to write good web apps today. Apple could have just removed the ability to launch web apps from the home-screen entirely if they wanted to. Why would they be so sloppy at executing a grand anti-competitive conspiracy?

ugh• 15 years ago

But why is it a good idea to have a saver web view outside of Safari when Safari remains wide open?

Maybe they think that people are aware that the web is generally less safe and act accordingly? And they don‘t want someone to smuggle that unsafeness into apps? (The homescreen webapps are more or less just collateral damage if you take on this view.) That’s the only somewhat plausible explanation I can think of and it doesn’t make all that much sense.

msbarnett2• 15 years ago

Because if I write an app for iOS, I can't mess with Safari's address space. But if I have a UIWebView in my address space and I can use it to get a hold of memory pages with their executable bits marked, I could use that to do all manner of things that are normally forbidden.

jevinskie• 15 years ago

Then why not allow at the home screen web apps to use Nitro? The entire app is within the UIWebView and controls nothing outside of it. I fail to see how a home screen web app is any different than one within MobileSafari.

brownleej• 15 years ago

Maybe the problem is that Nitro requires that an app have special permission to mark pages as executable. Apple may be comfortable giving this permission to Safari (or any if their apps, for that matter) but not comfortable giving it to third party apps. Along the same lines, it could be that apps saved to the home screen don't get Nitro because there is a special exemption low in the system for Safari, and they haven't yet worked out how to roll it out to the thin apps that are created when you save something to the home screen.

saurik5• 15 years ago

As someone who pulls this system apart constantly: this comment is dead on accurate.

tolmasky6• 15 years ago

The clear insinuation is that web apps running outside Mobile Safari have been made to run slower, but that’s not true. What happened with iOS 4.3 is that web apps (and JavaScript in general) running inside Mobile Safari have been made significantly faster.

This is such a ridiculous argument, and Gruber chooses to lead with it. So, according to Gruber, if 10 years from now everything else on iOS got crazy faster (including Mobile Safari), but web apps on the home screen remained the same speed as they do today, then Apple still wouldn't be hampering them. How can anyone even read the rest of the article after this?

But, if we do, we find the security argument is equally frivolous when it comes to home-screen web apps. There is nothing less secure about a home screen app (which is just a glorified bookmark) than MobileSafari. MobileSafari is connected to the web, which means they're already allowing anything access to Nitro. If anything, there would be a much better argument for ONLY allowing home-screen web apps, because the user is implicitly stating they trust it more (than any random page you might be redirected to).

Beyond all this, I am willing to believe the "hey, it'll come with time" argument. But we should just say that, not bend over backwards to manifest false reasons.

bandushrew9• 15 years ago

That is not the argument that Gruber is making. That is his factual summary of the current situation.

The argument that is being made is that Apple currently considers it a security risk to enable the new Nitro Javascript engine for all applications, preferring instead to enable it only for Safari Mobile, and leave other applications using the older javascript engine.

Possibly forever, destroying web apps on the iPhone completely, or possibly just until Apple is able to sort out the security implications of having to mark in memory pages as executable.

You get to chose which scenario you think is most plausible.

bandushrew9• 15 years ago

Edit: yay! you changed your post while I wrote mine.

tolmasky6• 15 years ago

Well, he's making multiple arguments, and that first one was an argument. My position is that it is a ridiculous one.

I am also not entering the discussion of native apps running UIWebView. I have zero comment on that (mainly because I'm disinterested in the subject).

My only comment is on home-screen web apps, which are 100% equivalent to opening the page on your browser. They deserve more privileges because the user had to make a decision to install them. It makes no sense to me whatsoever that a random advertisement loaded from some insecure URL on a web page is allowed to access Nitro and web cache, but a web app that I trust enough to install on my home screen is not.

Ironically, I'm actually pretty happy with this decision, because I believe all apps should be in the browser. I'm just telling it like it is when people make nonsensical arguments.

ynniv• 15 years ago

The "home screen bookmark" app is based on MobileSafari, but clearly isn't the same code base. I understand that your company would benefit from improved offline app performance, but it's likely that developer time and patience will fix the problem.

tolmasky6• 15 years ago

If you read my later reply, you'll see that I actually prefer the way things are, I just don't like misinformation. I am perfectly capable of accepting that its a matter of engineering time to get this to work. What I am not OK with is the notion that Safari is somehow a "trusted" app where this is not a security concern, whereas a home-screen web app is a security concern. There is no such thing as a trusted browser, any random malicious ad loaded in an iframe can have access to Nitro. Home screen web apps are necessarily just as safe or more safe than web pages.

raganwald2• 15 years ago

Elsewhere in the comments I'm reading HN folks who agree that there are security implications with having writeable code pages available to native apps, and that it's reasonable for some of the JIT stuff to appear in Mobile Safari and not in native apps (although there are other approaches Apple may pursue in the future).

Have you read these arguments? Do you disagree with them? Or are you saying something else?

Just trying to understand...

boucher3• 15 years ago

His point is that HomeScreen web apps (for lack of a better term) are fundamentally exactly as secure as MobileSafari.

Even a technical argument is somewhat hard to fathom, since it should be a trivially simple thing to enable, but given that none of us can see the code it's at least possible.

As far as native apps with embedded UIWebViews, this is a believable technical argument, though it isn't obviously true either. In other words, the political argument isn't significantly less likely than the technical one.

tolmasky6• 15 years ago

For starters, my argument is only about MobileSafari (MS) and home-screen web apps.

If you read my other posts I think you'll see I have no issue with the idea that there may be a security issue with JIT. That is fine and acceptable.

What I have an issue with is the idea that MobileSafari is somehow the safest place to put it. If there is a security issue, then MobileSafari is clearly the absolute least safe place to put it (vs homescreen web apps), since any malicious web page has access to it. That includes random ads loaded on otherwise safe web pages. The user is not prompted when entering a web page if they want to use Nitro or not, so basically anything goes on the open web. If a security flaw is discovered in Nitro, I have only to place it on an ad that gets deployed to popular sites to take advantage of it. And Apple's only recourse is to issue an entire system upgrade and hope people update.

Home-screen web apps are thus at least as safe as MobileSafari, since they are literally just bookmarks that load web pages (in a different process and without chrome, but fundamentally the same, no access to any other native code or anything). They are in fact arguably more safe, because the user has to first grant it "home-screen" status. This is a sensible time to ask the user if this ONE app should deserve more privileges than the rest of the wild-west web. In other words, had apple done the opposite, ONLY allowing home-screen web apps access to Nitro, it would make a lot of security sense, especially because Apple could warn the user before they download the app saying "downloading this app gives it access to the special Nitro engine, which may be less secure...".

statictype• 15 years ago

What the GP is arguing is that web apps pinned to the home screen are no different from those same web apps viewed in a browser and therefore, there doesn't seem like there should be any security issue involved in it.

Someone (who I think works on Cydia - the Jailbreak App Store) commented about this further down:

Of course, this means that there is no real good reason why Apple has disabled Nitro for full-screen web applications (that I at least yet understand), and so I'd expect that this was frankly just a silly oversight

ra88it3• 15 years ago

Would you concede that there could be a security diff between JIT and not JIT?

All Gruber is arguing is:

1) that there is a significant difference in security

2) that Apple didn't release any JIT for webkit all this time [edit: since 2008] because of security concerns

3) that Apple did not go out of its way to remove JIT from those instances of webkit that occurr outside of Mobile Safari

4) that perhaps Apple is simply rolling it out gradually

I don't see how any of this is ridiculous or could be called "bending over backwards" unless you are pre-loaded with a bias against Gruber.

There goes what little karma I earned since 2008.

boucher3• 15 years ago

2) They didn't release it, one imagines, because it is hardware specific, and originally written for x86 not ARM.

hopeless2• 15 years ago

It seems like there might be some justification for restricting Nitro from UIWebView because then you have to trust a third party app... but a webapp launched from the home screen is completely controlled by Apple's apps just like if you launched it from Safari (except less annoying). Surely these home page webapps can be treated just like Safari?

<cynical>Unless, of course, you want to discourage their development</cynical>

lukifer• 15 years ago

> but a webapp launched from the home screen is completely controlled by Apple's apps just like if you launched it from Safari

Not quite. In essence, a native app using UIWebView is created on the fly, and past that point it acts just like a standalone app. Only real-deal Safari gets the exception.

hopeless2• 15 years ago

ok, but it's created by iOS so surely can be trusted just like Safari?

ZeroGravitas• 15 years ago

The thing is, and I believe Gruber himself has pointed this out regarding Microsoft's past transgressions, you don't need a Simpsons style committee of evil for this stuff to happen. You just need a normal corporation filled with employees smart enough to know what's in the financial interests of their employer, and that sticking to those interests aids their own career progression.

Bugs and difficult to solve issues arise in all sorts of code. Just by prioritising what you work on and fix you can hose your competitors both within or outside your ecosystem. In this case, extra speed for Mobile Safari was clearly more important to Apple than extra speed for mobile apps that compete with their native apps.

zmmmmm3• 15 years ago

What really disturbs me is not the nitro JS performance part but this (from the register article):

    What's more, such "home screen web apps" 
    can't use various web caching systems, 
    including the HTML5 Application Cache, 
    which means they can't be cached to
    run offline.

I can live with my app being a little slower; after all, I don't really even contemplate writing performance sensitive apps as off line web apps anyway. I can NOT live with my apps not working, being unreliable, or taking ages to load because the user went through a tunnel or tried to use it on a plane.

Not only is this a much worse consequence and far more damaging than slower javascript, it's not addressed by any of the arguments I have heard about security. How does anybody explain this as a consequence of marking memory pages non-executable?

I will be very interested to see whether Apple fixes this and how quickly they do it. If they fix it urgently then I will recall the cynic hound-dogs within me. But if they let this lag for months then it seems pretty clear to me that they are just cynically closing down any attempt to route around the app store, if only by ensuring nobody will try to do so due to the chilling effect of knowing such apps could be broken for months at a time.

wzdd• 15 years ago

The explanation does actually derive from a security concern. Apps are sandboxed on the file system, so they can't access the cache. If apps were given access to the shared cache, they could pollute it.

Of course there are plenty of ways that Apple could address this problem, just as there are plenty of ways that Apple could address the non-executable pages problem.

zmmmmm3• 15 years ago

If it's a security concern then it's a very strange one. Apps are certainly sandboxed, but they've always been able to access their own files before. And this offline cache has been working for a long time. It's a very strange thing if they suddenly claim this is a security problem now.

saurik5• 15 years ago

As far as I know there was a bug on 4.2.1 where home screen web applications marked with a specific flag couldn't use the HTML5 Application Cache. Maybe they didn't get to fixing this in 4.3, but on 4.2.1 there was a reasonable-ish workaround.

Look, I hate Apple as much as the next guy (maybe more so: I mean, I've dedicate my life to messing with them), but the random rumor mongering surrounding tiny actions that they perform needs to stop.

Like, the HTML5 Application Cache? That code is horribly broken. I started using the HTML5 Application Cache in Cydia (and am now sufficiently "down that road" that I'm launching with this, hell or high water), but WebKit's implementation's barely works, and I don't think it is reasonable for people to be holding Apple quite to task on whether this feature happens to be working in every scenario.

I mean, seriously: when you start going through the WebCore code history and public bug tracker teasing apart what is going on, you find that the developers working on with some of these issues (and there are still critical show-stopper bugs that have only been noticed a few months ago, as well as ones that are still open) actually claim "no one understands this system", something you really believe when you see the massive unstable state machine that surrounds it.

It is therefore entirely plausible to me that the reason the app cache isn't working in apps with some random meta flag is solely because of one of the numerous queue bugs in WebKit's appcache logic that totally wedge the mechanism (even crashing it at times) if things happen to reload in the wrong order.

zmmmmm3• 15 years ago

It's been working for a long time to suddenly just break now ... when Apple just happens to be exercising some particularly anti-competitive practices against other players who might conceivably use it as a workaround.

Like I said - if they jump on it and fix it I'll say fair enough - anything can get broken in the rush to put out a new release (especially with a high profile new device involved - one can hardly expect they would be delaying release of iPad2 because of something like this). So we will see what happens. However until I see it fixed or some kind of indication that it will be I remain highly skeptical.

morganw2• 15 years ago

I don't know why they said that. I still can run http://code.google.com/p/pjs4ipad/ on an iPad 1 with wi-fi shut off with 4.3 (8F190). It works after a shutdown, power-up cycle too.

It's not just the Register, Ars http://arstechnica.com/apple/news/2011/03/confirmed-some-web... makes the same claim, but it works on my desk ;)

morganw2• 15 years ago

Saurik answered it, but it turns out that clearing Safari's cache will show that offline webapps are broken: http://technologizer.com/2011/03/16/the-trouble-with-iphone-...

blinkingled• 15 years ago

This is a design issue that is basically unsolvable unless Apple fully rethinks the iOS security model. In the current model, you can't give a library separate permissions than the process in which it was loaded - that's the gist of it. This has nothing whatsoever to do with Security as Gruber is spinning it to be - not directly at the least. As with Flash the real reason seems to be bypassing control.

I suspect RIM's security model allows them to do package / API specific permissions and prevent the app from doing things such as mmap(... PROT_EXEC) - anyone familiar with BB Security/Permissions model - care to comment?

mcculley• 15 years ago

To say that Apple does not allow writable executable pages for security reasons is to ignore the bigger reason Apple does not allow modifiable code: Apple does not want apps to have writable executable pages because then an app could implement an app store.

Why the Nitro JavaScript Engine Isn’t Available to Other iOS Apps

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