Framework Patch

Modify framework.jar to build a valid certificate chain.

Requirements

• Intermediate Windows and Linux knowledge.
• Intermediate Java and Smali knowledge.
• WSL (only in Windows).
• Java.
• 7zip.

In GNU/Linux distro, install these packages (I use Ubuntu in WSL2):

sudo apt update
sudo apt full-upgrade -y
sudo apt install -y default-jdk zipalign

WARNING

This is for advanced users, if you don't know about programming either Linux, this is not for you...

No support will be provided.

How can I make my system rw?

If you don't know how to do that just use a module for Magisk, KernelSU or APatch.

Also, in modern devices, you must format data because modifying super partition breaks AVB.

Tutorial

First, cd to a working (and clean) directory.

Pull framework.jar from your device:

adb pull /system/framework/framework.jar

Now, compile smali: (Use WSL if you are in Windows)

git clone --depth=1 https://github.com/google/smali.git
cd smali
./gradlew build

Then pick smali and baksmali fatJars and paste to working dir.

Using 7zip, extract framework.jar to framework/ directory.

Now using jadx, open framework.jar and check these classes:

• android.security.keystore2.AndroidKeyStoreSpi
• android.app.Instrumentation
• android.app.ApplicationPackageManager

You must check for the .dex they are in. You can know that by checking the text in the class declaration, something like this:

/* loaded from: classes3.dex */
public class AndroidKeyStoreSpi extends KeyStoreSpi

/* loaded from: classes.dex */
public class Instrumentation

/* loaded from: classes.dex */
public class ApplicationPackageManager extends PackageManager

Now using baksmali.jar, decompile all .dex files:

java -jar baksmali.jar d -a (ANDROID API LEVEL) framework/classes.dex -o classes
java -jar baksmali.jar d -a (ANDROID API LEVEL) framework/classes2.dex -o classes2
java -jar baksmali.jar d -a (ANDROID API LEVEL) framework/classes3.dex -o classes3
...

After all .dex files are decompiled, you must search in folders for these files and modify like this:

• AndroidKeyStoreSpi.smali:

Search for method "engineGetCertificateChain" and there should be a line near the end like this:

const/4 v4, 0x0
aput-object v2, v3, v4
return-object v3

In this example:

v2 -> leaf cert. v3 -> certificate chain. v4 -> 0, the position to insert the leaf cert in certificate chain.

It may be different in your .smali file. Do not copy and paste...

After aput operation, you must add this:

invoke-static {XX}, Lcom/android/internal/util/framework/Android;->engineGetCertificateChain([Ljava/security/cert/Certificate;)[Ljava/security/cert/Certificate;
move-result-object XX

Replace XX with the leaf certificate register.

So the final code (in this example) should be this:

const/4 v4, 0x0
aput-object v2, v3, v4
invoke-static {v3}, Lcom/android/internal/util/framework/Android;->engineGetCertificateChain([Ljava/security/cert/Certificate;)[Ljava/security/cert/Certificate;
move-result-object v3
return-object v3

• Instrumentation.smali:

Search for "newApplication" methods and before the return operation, add this:

invoke-static {XX}, Lcom/android/internal/util/framework/Android;->newApplication(Landroid/content/Context;)V

Replace XX with the Context register.

• ApplicationPackageManager.smali

Search for "hasSystemFeature" method:

.method public whitelist hasSystemFeature(Ljava/lang/String;)Z
    .registers 3
    .param p1, "name"    # Ljava/lang/String;

    .line 768
    const/4 v0, 0x0

    invoke-virtual {p0, p1, v0}, Landroid/app/ApplicationPackageManager;->hasSystemFeature(Ljava/lang/String;I)Z

    move-result p1

    return p1
.end method

And modify like this:

.method public whitelist hasSystemFeature(Ljava/lang/String;)Z
    .registers 3
    .param p1, "name"    # Ljava/lang/String;

    .line 768
    const/4 v0, 0x0

    invoke-virtual {p0, p1, v0}, Landroid/app/ApplicationPackageManager;->hasSystemFeature(Ljava/lang/String;I)Z

    move-result v0

    invoke-static {v0, p1}, Lcom/android/internal/util/framework/Android;->hasSystemFeature(ZLjava/lang/String;)Z

    move-result v0

    return v0
.end method

This hook is optional, but I recommend it if your device has Strongbox or app attest key support.

Now compile all dex:

java -jar smali.jar a -a (ANDROID API LEVEL) classes -o framework/classes.dex
java -jar smali.jar a -a (ANDROID API LEVEL) classes2 -o framework/classes2.dex
java -jar smali.jar a -a (ANDROID API LEVEL) classes3 -o framework/classes3.dex
...

Open this project in Android Studio and change EC and RSA keys, you must provide keybox private keys. Build project as release-build.

Using 7zip, extract classes.dex from the project release .apk file.

Rename extracted classes.dex to classesX.dex where X is (the number of .dex files in framework/ directory) + 1.

Copy renamed classesX.dex into framework/ directory.

Using 7zip, add all framework/ files to .zip archive without compression (Compression level: 0 - Store).

After you have the framework.zip, use zipalign:

zipalign -f -p -v -z 4 framework.zip framework.jar

Now move framework.jar to /system/framework, you can use a module to replace it or mount /system as read-write and replace it.

Very important! Remove all "boot-framework.*" files!