Apple Has Stopped iOS Downgrading 207
An anonymous reader noted a forum post seems to confirmApple will be
fighting downgrading in iOS 5. Quoting:
"This will only affect restores starting at iOS5 and onward, and Apple will be able to flip that switch off and on at will (by opening or closing the APTicket signing window for that firmware, like they do for the BBTicket)."
Walled Garden (Score:5, Insightful)
I found... (Score:5, Insightful)
Re:Hmmmm (Score:3, Insightful)
That depends. Do you love Apple products and think that they provide a slick, productive, secure intrrface? If so, this is wonderful news. Do you hate Apple and everything they stand for, and detest the idea of compromising your freedom for the safety of a walled garden? If so, this is draconian fascism that threatens the foundation of western freedom.
Re:Officially they never enabled it anyway (Score:5, Insightful)
1. In most walled gardens with cryptographically secured clients(either hardware devices or software DRM piles on general purpose PCs) downgrading is a valuable tool for attackers: unless a fundamental attack is found, most attacks are comparatively minor bugs in version N or game Y's savegame loading routine or whatever, which are then fixed in version N+1 or game Y Gold Edition. If downgrading is possible, it becomes pretty trivial for people to keep a copy of the easiest-to-exploit firmware or software version that ever received a cryptographic signature, and then downgrade to it. If downgrading isn't possible, they have to keep finding fresh exploits as old holes are closed. This is the same reason why software that connects to DRMed media sources tends to get updated a zillion times a year, and why such updates are generally made mandatory pretty quickly.
2. At least some of the updates, for Apple's flagship devices(upon which the iPod touch and wifi-only iPad are sort of hangers-on), aren't just OS update lumps, they also meddle with the embedded cellular hardware's firmware. Allowing downgrading would require dealing with v.N+1 basebands talking to v.N OSes, or involve allowing the baseband firmware to be downgraded(which is of interest to unlockers and other parties who Apple's carrier buddies don't approve of) and may involve some amount of bricking risk.
3. Apple has, at least until shitstorms forced their hand, never been much troubled at the idea that they are seen as forcing people to upgrade(remember their original response to the iPod battery life problem, until whining forced them to change it? Or the various OS 10.x releases that have dropped support for hardware configs upon which, once the version check is hacked away, it can in fact run?). This seems to be a matter both of business and of philosophy: Obviously, as a hardware maker, anything that makes people buy new hardware is profitable. Philosophically, they have never shied away from a pattern of releases of the form "Here is version N+1, it is insanely great. Everything prior to today is an obsolete archaism. On the plus side, this allows them to do interesting things with some regularity. On the minus side, this makes them quite happy to declare various features dead well before some of their customers are ready. The idea that they would dedicate engineering effort to allowing people with version N-1 or N-2 devices to run an obsolete OS runs against their priorities.
Re:Grand until the update bricks your phone (Score:4, Insightful)
Speaking from experience: I had a less-than-a-year-old iPhone 3g, which got semi-bricked when I installed the iOS 4 update last summer (stated as compatible, as in Vista-compatible).
At the time, I was able to downgrade back to a previous iOS release; but, being unable to call even emergency numbers for minutes (oh, if the phone didn't crash entirely) until they fixed their memory-hogging, badly written OS months later (iOS 4.2), would be a very bad thing.
If you had a less than a year old iPhone 3G, then you had a warranty. I can't imagine what you had to worry about. Oh, wait, I just saw the thing about being unable to call emergency numbers for MINUTES. This is good advice, and should be in the disclaimer in iTunes. Never start an iOS upgrade in the middle of a house robbery, or other event that might require you calling 911, unless you have another phone handy.
Re:Officially they never enabled it anyway (Score:4, Insightful)
I think that your work in OS security may have induced a certain amount of myopia. My discussion purely applied to DRM systems because DRM systems are the only scenario where the 'attacker' has access to the system from day one(it's their device, or the software running on their PC); and wishes to compromise the system's security. With other classes of software, the person with personal access and the vendor are allies in wanting the system to be secure.
If you think I'm a non-technical idiot, pull your head out of the confines of one particular flavor of security work and do a little research:
It's pretty painless: Wikipedia [wikipedia.org] has a list of iOS/baseband firmware versions, with handy notes about which baseband 'fixes' are there to deal with unlocking... A little googling will dig up some of the oddities involved in trying to mix versions. For virtually any DRM/walled garden system in wide consumer use(say, iDevice/PS3/xbox/Wii/PSP/DS/DSi) a quick google of 'Name downgrade' will pull up a sheet of results containing, depending on the system, a mixture of information on how to downgrade to more vulnerable firmware before running a hack or people with presently unhacked firmware on their devices hunting for downgrading information.
For the software case, one can look up various DRM-stripping tools, many of which will specify themselves as working only with certain older versions of the application that they attack, or (holding one's nose) attempt to connect to a DRMed service and be informed that you will need to upgrade to get access.
Within the specific domain of OS security I have no interest in arguing with your correctness; but you appear to have stepped into something quite different in attempting to talk about anti-customer security features, which are subject to their own peculiar dynamics... Try not to be rude when travelling.