Coercing a Magic MIFARE credential into being an iPhone-compatible NFC tag

https://ewpratten.com/blog/iphone-mifare-magic

by ewpratten • 2 years ago

92 67 2 years ago

so cool! anyone have any recs for cheap cards (or hardware) that is scannable on iphones?

walterbell• 2 years ago

The cheapest RFID/NFC "card" tag is an expired tap-to-use transit ticket. It has a unique ID that can be used to trigger an iOS Shortcut to take any action, e.g. speak an audio description, open URL, open app, etc.

For purchase, there are many form factors: https://store.gototags.com/nfc-tags

On Amazon, search NTAG215.

immibis• 2 years ago

If your city doesn't use NFC transit, you can also buy a box of blank cards. They have unique IDs like transit tickets, even without being programmed.

stavros13• 2 years ago

NTAG215 isn't "magic", right? I have a bunch of NTAG215 stickers and I'm not entirely sure what their difference is with magic cards.

ewpratten16• 2 years ago

Many of my cards are just repurposed from other things. Lots of hotel keycards can be rewritten to open URLs on phones for example.

I actually have a hotel keycard taped to my washing machine to do some laundry-based automation with my phone. Maybe I should write about that sometime..

Eisenstein2• 2 years ago

Have you thought about getting one implanted?

fragmede2• 2 years ago

https://www.amazon.com/dp/B0C49SVTCT

are the tags I have, and https://apps.apple.com/us/app/nfc-tools/id1252962749 is the app I used (which is the same as the one used in the post).

lxgr12• 2 years ago

If you only care about static data that you can optionally freeze to a permanent read-only mode, NTAG21[3|5|6] tags are probably among the cheapest ones that reliably work with all iOS and most Android devices.

MIFARE Classic supports (completely broken and for this use case) useless encryption and doesn't work with some Android devices, as they're not really a part of the standardized NFC stack.

If you want to get really fancy, you can also get a Java Card based smartcard and install an NDEF application yourself. You could then also install a FIDO application and use the same card as a "homebrew Yubikey" :)

pm2• 2 years ago

This is cool, but the most interesting part is the part that requires investigation, i.e., what do the compatibility tools write to the card to make it iOS-compatible? I've done some work with iOS NFC, but not enough to have experienced the undocumented quirks.

ewpratten16• 2 years ago

Ya, I have no clue tbh.

This is one of those cases where I know I really should investigate further, but I'm taking this one step at a time. Perhaps digging in to the "why" will become a follow-up post

stavros13• 2 years ago

But what happens if you dump the card with the Proxmark? Surely you should be able to see some differences.

Actually, I have all the components, so I'll try this now and report back.

pm2• 2 years ago

I didn't intend for what I wrote to be a criticism; that's on me. I just found it funny the most interesting step was akin to "... and now you've drawn the animal", if you understand the reference.

EricBetts• 2 years ago

My read of the proxmark code (https://github.com/RfidResearchGroup/proxmark3/blob/master/c...) is that the `ndefformat` formatted the tag MAD (https://www.nxp.com/docs/en/application-note/AN10787.pdf), which you'd do for NDEF, then had a single TLV TERMINATOR at the block where the NDEF message starts. Then he used NFC Tools to write on an NDEF text record (which iOS background reading would ignore) and maybe something else? After that he then used `ndefwrite` to write on a URL record. I wonder if he could have skipped the NFC Tools and written the URL record and gotten the same result. Proxmark dumps before and after using NFC Tools would be insightful.

ChrisMarshallNY• 2 years ago

I suspect the comment (above, at the time I wrote this), where they mention that Apple only wants partners to be usable, is the Ockham's Razor answer.

Probably some "magic key" ID.

But this is not my area of expertise. It's a cool story, though, and why I like hanging here. Considering getting a Proxmark and the NFC Tools app, just to play around.

nippoo• 2 years ago

Has anyone managed the opposite feat, i.e. made a piece of hardware that can recognise an iPhone over NFC? I'm trying to design control system that relies on you touching your phone to various hardware readers (with some kind of unchanging key/identity), but off-the-shelf MFRC522 etc don't seem to work, and the 'official' Apple way requires an NDA...

formerly_proven• 2 years ago

NFC has been opened up more in iOS 16 and 17.

Card emulation is a thing now: https://developer.apple.com/documentation/corenfc/cardsessio... (edit: only in the EU)

And iOS as well as iPadOS now also support USB smart card readers. iPads can actually use them to access NFC FIDO tokens. (Why iPads don't have native NFC is completely beyond me, there are so many obvious use cases for it)

lxgr12• 2 years ago

And iOS as well as iPadOS now also support USB smart card readers.

Oh, that's very cool!

Apple seems to silently be implementing more and more features to make iOS/macOS a full-fledged smart card OS; I've also noticed that FIDO over CCID is now available natively on macOS, and by extension in Firefox and Safari via WebAuthN (which finally lets me use my smartcard form factor FIDO authenticator).

auston• 2 years ago

Here you go: https://github.com/kormax/apple-vas

If you can send/receive APDUs you're good to go.

lxgr12• 2 years ago

Wow, that's neat!

Do you know if Apple requires any special permissions/entitlements to create VAT passes, or does a normal pass certificate suffice?

numpad0• 2 years ago

I think you're supposed to make a "Pass", load it on Wallet app, then load the card with double press of side button. You can't just tap a blank iPhone and get its raw hardware ID.

At least Suica train cards(based on FeliCa/NFC-F) on iOS can be read from third party Android apps, and Apple do advertise iPhone feature to store corporate IDs, so the idea of using iPhone for gate tap-in card should be completely fine.

lxgr12• 2 years ago

None of this is accessible to hobbyists, unfortunately – you'll need a special entitlement, certification, your use case to be an approved one etc.

It's not accessible to "regular" app developers in the way it is for Android.

lxgr12• 2 years ago

Without getting into the weeds of programming for the secure element (some non-EEA markets only, NDAs, tons of certifications etc.) or restricting yourself to HCE (available only in the EEA), you could also "flip the model around":

ISO 14443 reader access has been available globally, so if you're fine with having to open an app before an interaction with a reader, you could have the reader perform card emulation, and the phone "read/write" it like a tag, i.e. send APDUs which the device behind it then interprets.

xyst• 2 years ago

In my experience, the notification you see at the end of article was used to advertise your brand/site.

The number of obnoxious people/guerilla ad companies that printed and programmed NFC tags and stuck them in random places was way too high. In some cases, they would replace the businesses QR code with the NFC tag. In some cases that NFC notification would pop up instead of the business’s menu. Quite annoying.

Then there was a case where the person stuck the raw tags _under the table_, so putting your phone down in random places would spam this notification on your screen.

ewpratten16• 2 years ago

Ah, we did the under-the-table thing with NFC stickers in school! Love rickrolling a well-placed phone on a classroom desk lol.

I'm personally not a huge fan of needing to use NFC tags in the real world (parking meters use them for payment around here), but I do like creating tags.

kweks• 2 years ago

We did extensive research on the subject, there is no mystery. iOS will only read MIFARE tags with NDEF formatted data. If you write NDEF data to a formatted MIFARE card, it will be 'compatible' with iOS.

Otherwise, only the UID can be detected. The real mystery is why Apple refuses to open the low-level read commands. (To read NDEF, or determine that the data is _not_ NDEF, you need to read the card.)

noprocrasted2• 2 years ago

It's not a mystery - it's anti-competitive behavior where they only want to give access to low-level NFC access (required to enable things like door locks, car keys, payment/loyalty card systems, transport, etc) to "partners" who sign an NDA and agree to a rev-share.

privacyking• 2 years ago

Didn't apple announce earlier this year they were going to open NFC up more? What ever happened to that?

lxgr12• 2 years ago

For all the things wrong with/bad about Apple's iron grip on low-level interfaces, in this case that's not the only reason:

MIFARE Classic uses a mandatory, proprietary (presumably still patented) encryption algorithm even for "world-readable" cards, on top of the ISO 14443-3 standard. I'm not even sure whether Apple could legally offer that capability without licensing it from NXP.

On Android, only devices with an NXP chip support these tags for the same reason.

You could argue that Apple could just provide even lower layer access to the contactless interface to allow apps to implement it in software, but I'm not sure if that's feasible (due to timing constraints).

(Note that the article doesn't specify which MIFARE tags it is about. If it's MIFARE Classic, something must have changed, and maybe Apple has licensed the required NXP patents? DESfire should work with iOS without jumping through any hoops, since that implementation is ISO 14443 compliant all the way up to -4.)

HWR_14• 2 years ago

It's not a mystery - NFC features are cool but contactless payments are valuable. Nothing that could possibly interfere with that will be tolerated.

philjohn• 2 years ago

Ah - this brings back memories.

Back in 2015 I was tech lead for a modern (web based) SaaS library management system and getting it to work with RFID tags with a wrapper application was all sorts of fun and games.

We got RFID library tags working on Android, but with iOS locking down NFC access it turned out to be impossible and we had to get libraries to buy bluetooth connected RFID scanners.

Coercing a Magic MIFARE credential into being an iPhone-compatible NFC tag

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