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iPhone 6s, running iOS 12.0.1

Plugging the phone into a computer to charge produces an "Unlock iPhone to use accessories" message and the phone refuses to charge.

How do I fix this nonsensical behavior? I know Apple added a privacy feature where the phone disables the data connection on lock to thwart hacktools that plug into the phone and brute-force the access code, but there's no reason to disable charging-only while it's locked. In this particular case, I only need to charge the phone over a computer; it doesn't need data access.

I'd like to avoid having to buy additional hardware such as a separate power-only limited USB cable.

  • 2
    Are you sure it's because the iPhone is locked? Maybe the USB port just won't supply enough power. (In the latter case, it may in fact be charging, just very, very slowly.) – Wowfunhappy Oct 18 '18 at 23:14
  • I'm 100% certain that the USB port works properly. It worked fine before updating to iOS 12. Additionally, if I unlock the phone and plug it in, it charges normally on that computer. I assume a low-power port would produce a different error, likely a silent failure such as apple.stackexchange.com/questions/287157/… – user1258361 Oct 18 '18 at 23:16
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    Just to be clear, a lower power USB port is working properly—you could in fact argue it's the higher power ports that are borked, because they're technically breaking the USB spec. But yeah, if the phone charges once it's unlocked, your assessment is likely correct. – Wowfunhappy Oct 18 '18 at 23:25
  • Have you tried another USB cable? – IconDaemon Oct 18 '18 at 23:37
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    I retract my above comment after waking this morning to discover I had failed to unlock mine the night before so after 10 hours of "charging" the damn thing was flat. [& I just read today that the 'grey box' thingy has already succeeded in bypassing this measure.] – Tetsujin Oct 22 '18 at 15:57
3

Newer iOS and hardware have a way to relax the security and allow charging / negotiation of fast charge even while locked. I'll let the OP answer cover that detail and keep the older details here.

The iPhone will charge at lower rates from a pure charging port, so you just want to put a data blocker on the USB so that the phone won't reject a computer and see a charge only device.

There are many of these and you generally get what you pay for in low cost USB accessories. I'd expect to pay $10 for either one good blocker or a pair in the US. I know you didn't want to buy hardware, but unless you can get your computer to stop signaling it's a USB data connection, iOS is going to shut down the port since that's "what it do".

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    Voting this up for being partially helpful; however an answer needs to work with my existing hardware to be properly accepted. As an interim solution I temporarily disabled the USB restricted mode while waiting for Apple to implement what should have been obvious from the start. Moral of the story: unreasonably strict security "features" are no practical protection if they significantly damage usability simply because people get fed up and disable them – user1258361 Oct 19 '18 at 1:22
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    what if you just unlock it when you plug it in and then lock it once it starts charging. That should take off of 2 seconds... – Steve Chambers Oct 19 '18 at 14:56
  • It's NOT "obvious from the start". If you plug the phone into a USB port (as opposed to a charger), then the phone has to negotiate with the device on the other end about what is to occur. It's working EXACTLY as it should. – Marc Wilson Oct 21 '18 at 19:03
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    @user1258361 Well done. I've pointed to your answer on the settings to relax security. Well done. +1 on that and glad it got a bounty. It should rise above my answer in time. – bmike Feb 28 at 12:48
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+50

Fixed.

Go into the security settings (Settings -> Touch ID and Passcode), and enable the "USB Accessories" switch (it should be green with the virtual switch-button to the right). This enables charging off any connection while locked.

Unfortunately this also disables the privacy/security feature that thwarts hacktools with physical access, so if you enable the USB Accessories option you will want to take extra precautions to prevent unauthorized physical device access and refrain from plugging into dodgy machines.

  • 1
    I would suggest you to add that this security feature (to block data connection when iPhone locked) is failing. As professionnal would say it is “false security” from the same zoo as the doomed “empty extinguisher”. – dan Feb 23 at 10:17
  • Completely agreed. There's common-sense security, and then there's ridiculous paranoia. Blocking charging-only makes about as much sense as welding all the doors in your house shut and placing permanent metal bars over your windows to prevent burglary. Obviously this makes unauthorized access extremely difficult, the problem is that it also makes authorized access difficult. – user1258361 Mar 3 at 17:46
  • Update: Turns out USB restricted mode (disabling USB accessories to require unlocking for USB access including charging) is even more obsolete than previously mentioned, according to a new article where hackers claim they have a "future-proof" way to defeat iOS 12 USB Restricted Mode - see macrumors.com/2018/06/14/grayshift-usb-restricted-mode-solution – user1258361 Apr 14 at 18:56
-1

If you have an extra usb cable for your iPhone you may make a charge only cable by cutting the data wires. In an iPhone Charge&Sync cable, you will find 4 wires (because usb uses 4 wires to communicate, you have the data +/- and the +5v and ground) of various colors. I found a tutorial on how to clip the data lines on a usb cable on inscrutables. The general idea is the same, except it's an ios cord, and not a microusb. Charge Only Cable (Instructables)

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    This receipe will break a data USB cable and thus force the author of the question to buy a new data USB cable. I feel that to buy an USB charger would be easier. But the two ways fail one of the requested condition: to avoid buying new hardware because of an iOS upgrade 😉. – dan Feb 23 at 10:28
  • +1 This rightly suggests the cable can be the problem. I have a cable, that came with the iPhone, that makes me unlock to charge on an ac brick, not even a computer. That's asinine. A cheap aftermarket cable works fine. Obviously the 'charge only' cable is what the op needs, which is suggested by this answer. – Wilbur Whateley Mar 26 at 4:40

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