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Start Jon8RFC's readme portion

Docker setup on Windows

I use this batch file I made to keep things simple and quick:
https://github.com/Jon8RFC/nfcscreenoffpatcher/blob/master/container_setup.bat
You can do steps 1-2, then use the batch file.

  1. Install Docker, update WSL if instructed
    • 🟥 do NOT click on restart when Docker prompts--close applications and use the start menu to restart! 🟥
  2. Download and unzip this repo
  3. Run in cmd docker build --no-cache "C:\nfcscreenoffpatcher-master" -t patcher/patcher:latest (builds, names, tags the image)
  4. Run in cmd docker run -p 8000:8000 --name patcher patcher/patcher (binds the port, creates & starts the container)
  5. Stop the container in Docker (unsure if it gracefully closes from cmd)
  6. Run in cmd docker builder prune (cleans up remnants/junk from any vestigial or failed builds)
  7. Start the container in Docker whenever you want it
    • (optional) Run in cmd docker update --restart always patcher (starts the container when you run docker)

File locations of WSL and Docker configs:
"C:\Users\%USERNAME%\.wslconfig"
"C:\Users\%USERNAME%\AppData\Roaming\Docker\settings.json"
You'd create .wslconfig yourself, maybe with:

[wsl2]
memory=4GB
processors=8
#swap=0 #swap memory max, defaults to 25% of memory size on Windows rounded up to the nearest GB

NFCScreenOff magisk module

Edit the customize.sh file's PATCH_URL to your computer's IP running the Docker patcher, such as: http://192.168.1.30:8000

Manual apk viewing

I like apktool and notepad++, but you can use dex2jar and something like JD-GUI (github) for a different and conglomerated viewing of the decompiled apk.

  • Run in cmd apktool d NfcNci.apk, then edit files in text viewer
  • Run in cmd d2j-dex2jar.bat -f -o NfcNci.jar NfcNci.apk, then open in JD-GUI

⠀⠀ ⠀⠀ ⠀⠀

Start Lapwat's NfcScreenOffPie readme from 2019-11-15:

Tools

  • adb
  • apktool
  • smali / baksmali v2.3+
  • zip / unzip
  • zipalign
  • jarsigner

Enable ADB on phone in developper options.

Decompile process

# copy original sources
$ adb pull /system/app/NfcNci/NfcNci.apk
$ adb pull /system/framework/framework-res.apk

# create a backup for recovery
$ cp NfcNci.apk NfcNci_bak.apk

# decompile
$ apktool d -f NfcNci.apk -o NfcNci/

Modding

This is the part where you reverse engineer the source code of the app by modifying smali files.

For NfcNci, apply those changes.

Files to edit are located at:

  • NfcNci/smali/com/android/nfc/NfcService.smali
  • NfcNci/smali/com/android/nfc/ScreenStateHelper.smali

Compile process

# load framework
$ apktool if framework-res.apk

# compile
$ apktool b -f NfcNci/ -o NfcNci_mod.apk

# sign
$ keytool -genkey -v -keystore ~/.android/debug.keystore -storepass android -alias androiddebugkey -keypass android -keyalg RSA -keysize 2048 -validity 10000
$ jarsigner -verbose -sigalg MD5withRSA -digestalg SHA1 -keystore ~/.android/debug.keystore -storepass android NfcNci_mod.apk androiddebugkey

# align
zipalign -v 4 NfcNci_mod.apk NfcNci_align.apk

Load modded APK on your phone

adb push NfcNci_align.apk /sdcard/
adb shell

# android shell
su
cd /system/app/NfcNci
busybox mount -o remount,rw $PWD
cp /sdcard/NfcNci_align.apk NfcNci.apk
chmod 644 NfcNci.apk

Something went wrong?

You can restore the original APK file at any time with those commands.

adb push NfcNci_bak.apk /sdcard/
adb shell

# android shell
su
cd /system/app/NfcNci
busybox mount -o remount,rw $PWD
cp /sdcard/NfcNci_bak.apk NfcNci.apk
chmod 644 NfcNci.apk

Sources

Java versions of smali files for reverse engineering

https://android.googlesource.com/platform/packages/apps/Nfc/+/refs/tags/android-9.0.0_r48/src/com/android/nfc/

Big up to Lasse Hyldahl Jensen for his version for Android N

https://lasse-it.dk/2017/01/how-to-modifying-nfcnci-apk-to-run-when-screen-is-turned-off-on-android-nougat/

Understanding the signing process

https://reverseengineering.stackexchange.com/a/9185