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Major new iOS bug can crash iPhones and disable access to apps and iMessages

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Re: Major new iOS bug can crash iPhones and disable access to apps and iMessages

#51

Post by gmueckl »

mattnewton wrote: post #6
hello_asdf wrote: post #3

I've never done any fuzzing personally, but wouldn't this be discoverable internally during testing? I would think that they would attempt sending all possible characters, especially because they've had issues with this in the past.

I would hope that after all the character-crashing-everything bugs that have hit iOS there is a team dedicated to replacing the text rendering code with something more fault tolerant.

I wonder if its the renderer or the font itself that is at fault here. Fonts are almost more code than data these days.

Re: Major new iOS bug can crash iPhones and disable access to apps and iMessages

#52

Post by Manishearth »

kumarm wrote: post #30

Wow its just unicode character in a language spoken by just 75Million people https://en.wikipedia.org/wiki/Telugu_language

Not technically correct; is not a sequence you'd see in actual Telugu text (zwnj doesn't do anything for telugu).

However, there are similar test cases for Bengali, and ZWNJ does have an effect on some Bengali vowels, so it's definitely a real world character in that case.

Re: Major new iOS bug can crash iPhones and disable access to apps and iMessages

#53

Post by taf2 »

virgilp wrote: post #38
TazeTSchnitzel wrote: post #26

Earlier quoted context omitted.

Fuzzing finds bugs, using a safe language precludes them.

No it doesn't. At best it precludes a certain class of bugs (which may be very significant, but it's not a silver bullet)

var stack = [];

function ThisWillNeverCrash() {

   console.log('hello');

   stack.push('it');

   setTimeout(ThisWillNeverCrash, 0);
}

setTimeout(ThisWillNeverCrash, 0);

// my point in posting this was to demonstrate a bug ... that array will eventually run out of memory and this loops infinitely but not using a standard language loop construct... but I see someone didn’t think that was relevant

Re: Major new iOS bug can crash iPhones and disable access to apps and iMessages

#54

Post by badgers »

TazeTSchnitzel wrote: post #14

This isn't the first time a weird sequence of Unicode characters has caused the text renderer to crash and create problems for iOS users. This is why we shouldn't be writing new code in C.

We need a new "Falsehoods programmers believe about character encodings" article to be added to the falsehoods list [1]. Joel Spolsky wrote in 2003 about the dangers of the ignorance of character encodings [2].

[1] - https://github.com/kdeldycke/awesome-falsehood

[2] - https://www.joelonsoftware.com/2003/10/08/the-absolute-minim...

Re: Major new iOS bug can crash iPhones and disable access to apps and iMessages

#55

Post by makecheck »

TazeTSchnitzel wrote: post #14

This isn't the first time a weird sequence of Unicode characters has caused the text renderer to crash and create problems for iOS users. This is why we shouldn't be writing new code in C.

There are compartmentalization options, such as XPC Services on macOS (specialized sub-processes that can “crash” if something is risky).

Also, non-C languages frequently implement lots of library features on top of C because it would be a ton of work not to (and slower), which means any language could be at risk.

Re: Major new iOS bug can crash iPhones and disable access to apps and iMessages

#56

Post by andrewmcwatters »

TazeTSchnitzel wrote: post #14

This isn't the first time a weird sequence of Unicode characters has caused the text renderer to crash and create problems for iOS users. This is why we shouldn't be writing new code in C.

What causes this to be an issue in C but not in other languages?

Re: Major new iOS bug can crash iPhones and disable access to apps and iMessages

#57

Post by aaomidi »

tosz25 wrote: post #20
Cknight70 wrote: post #15

Here's a link to the character if someone wants to test it themselves https://pastebin.com/9Tr8ytTr

Crashed Chrome as well.

If if its the iPhone you're talking about. Chrome is a "wrapper" around Safari's web engine.

Re: Major new iOS bug can crash iPhones and disable access to apps and iMessages

#58

Post by echohack4 »

For those you looking to test this out yourself, I have a python script that could be helpful in pulling iMessages off your iPhone backup (assuming because it might be difficult to access them if the application is in a crash loop).

https://github.com/echohack/iphone_messages_dump

Re: Major new iOS bug can crash iPhones and disable access to apps and iMessages

#59

Post by blub »

13of40 wrote: post #8
taylodl wrote: post #2

What Apple, and Microsoft before them, are discovering is the tools and processes we use to create software simply doesn't scale. We're simply reaching the limits of what these giant software teams are able to produce and keep running. We can discuss solutions, but currently not everybody even agrees we have a problem. That's the first step we need to take.

I disagree that this is the product of scale. Looking at some of the bugs coming out of Apple lately and how they respond to them (assuming it's really a trend and not just a run of bad luck) it feels like they're slipping into a culture where individual feature teams are making emotional or schedule-based decisions about security without central guidance. A good example is the recent bug on MacOS where a low-privile…

You're just making assumptions. All we know is that there's a failure.

We don't know what kind of and how many errors triggered the failure, nor do we know what the faults causing the errors were.

We certainly don't know what kind of hazard analysis they did and what kind of mitigations they have in place, nor do we know whether they accepted a specific amount of residual risk for e.g. economic or market pressure reasons.

We don't know what kind of QC they do.

Without this information, it's pointless to talk about how things feel or seem. This is a very large engineering organization, working on a very large and complex system. It's not possible to find the root cause (or any cause) of a failure by using guesswork or by reporting to familiar failure cases.

Re: Major new iOS bug can crash iPhones and disable access to apps and iMessages

#60

Post by ronnier »

jcsnv wrote: post #46
Cknight70 wrote: post #15

Here's a link to the character if someone wants to test it themselves https://pastebin.com/9Tr8ytTr

I sent this link to my phone and the character is in the meta-title, which then crashed my phone. It works! Now how to fix it...

Option 1:

* Have someone else send you a message

* Click the notification and it'll open their message

* Navigate back and delete the corrupting message

Option 2:

* Sign up for the ios beta program (free) https://beta.apple.com/sp/betaprogram/ and install the latest beta which isn't impacted.

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