Allow rewriting of amiibo tags [merged]

[Golem642]

Feature Explanation

Hello, recently got a pack of Ntag215 and i tried writing an amiibo to one of them. Then I tried overwriting for a new Amiibo model but it didn't work, so i searched and i found out you can't rewrite amiibo serial and such because the 3DS would check for the read-only bytes as said in #18

So i decided to make an IPS patch for it (https://github.com/Golem642/NFCheckRem/) so that it wouldn't check those bytes when reading/writing.
So now I'm asking : can you implement a feature so we can write amiibos without locking them to read-only ?

That would be very useful, thx

Usage Confirmation

• I confirm this is a request for a new feature, not an issue

[AbandonedCart]

This would result in a mountain of issues from people not only confused how to use when they had all the right parts, but those thinking they can do it without them.

[Golem642]

This would result in a mountain of issues from people not only confused how to use when they had all the right parts, but those thinking they can do it without them.

Just put a warning or something that tells them that if they want to change the amiibo type they need a special patch for their 3DS and WiiU

Can't do the switch patch cuz I don't have one, the 3DS patch is done and OG amiibo tags can still be recognized so I'll consider this as a win (can't try with read unlocked ones since i don't know how to make one manually), WiiU patch needs to be made but i don't have access to it rn so later i guess

[AbandonedCart]

Just put a warning

The mountain of issues I was talking about was with a warning.

[Golem642]

Like when you want to write an amiibo Tag, on the NFC scan page put a red text somewhere on the bottom that says "Amiibo tags cannot be rewritten, if you want to have write-unlocked tags you need to first install these patches for your console"

And then idk if you enable an option in the settings of the app or something it will write write-unlocked amiibo tags, and the text will be blue and say instead "Currently writing a write-unlocked amiibo tag. These will only be compatible with a modded console and the following patches installed"

Just an idea, but yk it's possible and it would help people a ton imo

[Golem642]

You're basically describing how loading keys works.

No ? It is the first time I'm actually using the app yeah, before that it didn't work with my other tags
But i don't get what you mean, what does it have to do with loading keys ? I'm talking about the page where you scan to write the NFC tag

[AbandonedCart]

Just put a warning or something
put a red text somewhere on the bottom
if you enable an option in the settings of the app or something it will write write-unlocked amiibo tags, and the text will be blue

Change the text from blue to green and you just described keys, but it's still the number one thing reported as "broken"

[AbandonedCart]

I'll look into it, but I'm not making any promises. It may need to be its own separate build not available on Google Play

[Golem642]

Oh this, yeah i know what you mean. I figured it out by myself but i guess not everyone does.
I have to say : the file picker opening as soon as you first start the app isn't very intuitive, like what do we have to do with it ?
That's why people don't find it, then they have to check in the settings but people just want things to work.
You could fix this by adding a dialog box before opening the file picker automatically, one that says "Important information: To decrypt amiibo tags, you must import unfixed-info.bin and locked-secret.bin. How you obtain the files isn't my problem but they are required for everything"
And then this dialog box would popup on every startup if the files still haven't been imported

[AbandonedCart]

I'm sure the app needs more dialogs. Nobody has issues figuring out how to load the keys. They don't understand why they need them. Similarly, the issue with your proposal is that most people aren't going to want to install an app (or custom firmware at all) and will want it on Switch.

[Golem642]

I mean it could probably be implemented on switch as well, i just personnally can't do it since i don't own one. But i'll detail the patch in my repo so it's easy enough to understand

[AbandonedCart]

It's nice to have a solution for everything, but I can't really implement any of it from here. so I'll get back to you.

[AbandonedCart]

92a0be7

Is that the only part you need removed for it to work with your patch?

[Golem642]

Yeah so i tried disabling the writeLockInfo part and rebuilt a new APK, and i found multiple things:

1. Yes it seems to work, I am able to rewrite the tag without any additional modifications to the app
2. Luma3DS problem : the IPS files seem to only apply on boot, and not when the service starts/restarts. So basically my file does nothing at the moment
3. Even if it did, it wouldn't work : i tried multiple things and it turns out it's not a binary logical gate that is used. I decompiled the code and found out they literally do a byte check one by one. So I'm going to look further into this, hopefully it won't take long

[AbandonedCart]

Alright. I looked further into it and found a compromise for making it "safe" by using something like the current "ignore tag ID" checkbox that is opted into manually before a write. Ironically, I think that has a somewhat similar purpose. it's basically a force overwrite.

[Golem642]

Good news : after a month of not having anough time to think about this and a bit more tinkering, i found a working solution !
Currently the patch can only be manually applied by editing the values in the memory using Rosalina's process manager, but i can confirm it allows reading of non write-locked nfc tags (and actual amiibos still work too, but not blanks NTAG215 thankfully)
Gonna test the writing, my excitement is kinda high rn (second time using ghidra, first time doing something useful out of it)

Edit : as expected, writing with the amiibo settings app on my 3ds (which is what i'm using) is working, and it doesn't re-lock the tag. Also tested re-reading it after, and it works as well. Just need to publish everything now !

2nd edit : i forgot that even if the quick custom tagmo build i made allows for rewriting tags, it also removes data inside it so my mii and name was erased from the tag lmao. But it works ! Successfully changed the amiibo type, and my 3ds scans perfectly for it (even though there's no data on it anymore)