iMessage: Malformed Message Bricks iPhone

Post by EugeneOZ » Mon, Jul 08, 2019, 3:18 PM UTC

ec109685 wrote: post #53

EugeneOZ wrote: post #47

Lazy developers throw exceptions, good developers return errors. Exceptions should be exceptional. I'll use URL to this bug in my next comment-holywars to prove this point. Yes, it takes much less code to throw an exception in hope some code will catch it, but while compiler (not runtime) doesn't check it - this technique is not safe. So we should return errors, check them and handle - sometimes it means returning er…

Crashing a program is often safer for unexpected conditions than hoping your error handling will recover from it? Have you tested every combination of state + error and made sure your app is robust for each situation?

Post by egorfine » Mon, Jul 08, 2019, 3:20 PM UTC

baybal2 wrote: post #145

rixrax wrote: post #34

This brings back old memories from hardening the sms/text parsers of feature phones of yesteryear. There it wasn’t entirely uncommon that when you sent a malformed sms-deliver PDU (e.g. text message) to the phone and crashed parser that tried to decode it, it took also the phone down before it could ack the message back to SMSC. Which of course meant that as soon as phone was turned on and it registered to network, t…

Yes, Sony Ericsson A200 had a bug in SMS picture decoding (old, monochorme, pre-MMS one) which was easily craftable into an exploit if carriers were allowing multipart SMS. Guess what cell carriers did back then? Yes, they disabled multipart SMS

Post by hendersoon » Mon, Jul 08, 2019, 3:28 PM UTC

Post by arwineap » Mon, Jul 08, 2019, 3:42 PM UTC

applecrazy wrote: post #206

romaaeterna wrote: post #135

Speaking as an ex-Apple employee, I'll just point out that a really malicious actor could have used this to harm some significant percentage of the installed iOS infrastructure, and done critical damage to Apple as a company with it. In fact, I don't know the percentage of users still on <12.3, but maybe they still could. A band-aid fix for this one bug should not be where they stop here.

What they should also do is block the malformed message from being sent too. Not sure how to do that, since iMessages are encrypted in transit, but I'm sure there's some way.

Post by icebraining » Mon, Jul 08, 2019, 3:50 PM UTC

microcolonel wrote: post #150

johncolanduoni wrote: post #146

Earlier quoted context omitted.

That's not really a coupling issue, but a matter of GPU drivers not generally being hardened against shader/usage bugs. Similar issues have existed on Windows, Linux, etc. browsers with WebGL support.

> That's not really a coupling issue, but a matter of GPU drivers not generally being hardened against shader/usage bugs. You shouldn't be able to crash the whole operating system (not just the display server, display driver, etc.) with an ordinary shader, even if it crashes the shader compiler or causes the GPU not to halt. It's not as though I wrote these shaders in an attempt to crash iOS.