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Skillsandroid-apk-patch

android-apk-patch

Coding & development

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Updated 10-16 05:02

About this skill

Table of Contents

  1. Toolchain Setup
  2. Decompile/Recompile Workflow
  3. Signing
  4. Deep Dives

1. Toolchain Setup & Version Requirements

1.1 Mandatory Tools

Tool Version Purpose URL
Apktool v2.11.0 Decompile/recompile APKs https://github.com/iBotPeaches/Apktool
jadx v1.5.1 Read-only Java decompiler https://github.com/skylot/jadx
smali/baksmali v3.0.9 DEX bytecode assembly/disassembly https://github.com/baksmali/smali
APKEditor Latest Merge/split APK handling https://github.com/pxb1988/APKEditor
apksigner SDK Build Tools 35.0.x APK signing (v1/v2/v3/v4) Part of Android SDK
zipalign SDK Build Tools 35.0.x APK alignment before signing Part of Android SDK
Frida v17.9.0 Dynamic instrumentation https://frida.re
ADB Platform Tools 35.0.x Device/emulator communication Part of Android SDK

1.2 Version Requirements

  • Apktool < 2.9.0 — Cannot handle API 34+ resources
  • Apktool < 2.6.0 — Uses legacy AAPT (v1) instead of AAPT2
  • smali < 3.0.5 — Cannot disassemble DEX format 038+ (Android 13+)
  • jarsigner — Only produces v1 signatures; modern Android requires v2

1.3 Environment Setup

# Java 11+ required (Java 17 recommended)
export JAVA_HOME=/usr/lib/jvm/java-17-openjdk

# Install Android SDK Build Tools
sdkmanager "build-tools;35.0.0"
sdkmanager "platform-tools"

# Install Frida
pip install frida-tools

2. Decompile/Recompile Workflow

2.1 Standard Workflow

# Step 1: Analyze with jadx
jadx-gui target.apk  # GUI
jadx -d analysis_output/ target.apk  # CLI

# Step 2: Decompile with apktool
apktool d target.apk -o decompiled/ -f

# Step 3: Make modifications (smali, resources, manifest)

# Step 4: Recompile
apktool b decompiled/ -o rebuilt.apk

# Step 5: Align (CRITICAL - must be BEFORE signing)
zipalign -v -p 4 rebuilt.apk rebuilt_aligned.apk

# Step 6: Sign
apksigner sign --ks ~/.android/debug.keystore \
    --ks-pass pass:android --key-pass pass:android \
    rebuilt_aligned.apk

# Step 7: Verify
apksigner verify --verbose --print-certs rebuilt_aligned.apk

# Step 8: Install
adb install -r rebuilt_aligned.apk

2.2 Decompilation Flags

# Force specific API level
apktool d target.apk -o out/ -f --api 35

# Ignore missing resources (Apktool 2.11.x)
apktool d target.apk -o out/ -f --ignore-missing-resources

# Skip resources (faster, Java-only)
apktool d target.apk -o out/ -f -s

# Decode only resources
apktool d target.apk -o out/ -f -r

# Use custom framework (OEM system APKs)
apktool if /path/to/oem-framework.apk
apktool d system_app.apk -o out/ -f

2.3 Decompiled Structure

decompiled/
├── AndroidManifest.xml
├── apktool.yml
├── assets/
├── lib/              # Native .so files
│   ├── arm64-v8a/
│   ├── armeabi-v7a/
│   └── x86_64/
├── res/              # Resources
│   ├── values/
│   ├── layout/
│   └── drawable/
├── smali/            # Main code (DEX bytecode)
│   └── com/example/app/
└── smali_classes2/   # Multi-DEX apps

2.4 Smali Editing Basics

# Force boolean method to return true
.method public isPremium()Z
    .registers 2
    const/4 v0, 0x1
    return v0
.end method

# NOP out a method call
# Replace: invoke-virtual {v0}, Lcom/example/Payroll;->show()V
# With:    nop

# Remove permission check
# Replace: if-eqz v0, :cond_deny
# With:    nop

2.5 Resource Editing

<!-- res/values/strings.xml -->
<string name="app_name">Patched App</string>

<!-- AndroidManifest.xml - Add permission -->
<uses-permission android:name="android.permission.QUERY_ALL_PACKAGES" />

<!-- AndroidManifest.xml - Export activity -->
<activity android:name=".HiddenActivity" android:exported="true">
    <intent-filter>
        <action android:name="android.intent.action.MAIN" />
        <category android:name="android.intent.category.LAUNCHER" />
    </intent-filter>
</activity>

3. Signing: Schemes, Pitfalls, and Procedures

3.1 Signature Schemes

Scheme Since Mechanism
v1 (JAR) API 1 Signs individual files in META-INF/
v2 API 24 Binary signature block; verifies entire APK
v3 API 28 v2 + key rotation support
v4 API 30 Merkle hash tree; streaming verification

Critical: v2/v3 are whole-APK signatures. Any byte modification invalidates them.

3.2 apksigner vs jarsigner

Feature apksigner jarsigner
Schemes v1, v2, v3, v4 v1 only
Whole-APK verification Yes No
Required for API 24+ Yes No — rejected

NEVER use jarsigner for APK signing.

3.3 Signing Procedure

# Create custom keystore (one-time)
keytool -genkey -v -keystore ~/release.keystore \
    -alias myapp -keyalg RSA -keysize 2048 -validity 10000

# Debug keystore (testing only)
# Location: ~/.android/debug.keystore
# Password: android
# Alias: androiddebugkey

# Full workflow
# Step 1: ALIGN first (critical!)
zipalign -v -p 4 rebuilt.apk rebuilt_aligned.apk

# Step 2: Sign
apksigner sign \
    --ks ~/release.keystore \
    --ks-key-alias myapp \
    --ks-pass pass:your_password \
    --key-pass pass:your_password \
    --v1-signing-enabled true \
    --v2-signing-enabled true \
    --v3-signing-enabled true \
    rebuilt_aligned.apk

# Step 3: Verify
apksigner verify --verbose --print-certs rebuilt_aligned.apk

3.4 uber-apk-signer (Alternative)

# Download from https://github.com/patrickfav/uber-apk-signer/releases

# Quick debug signing
java -jar uber-apk-signer.jar --apks rebuilt.apk

# With custom keystore
java -jar uber-apk-signer.jar \
    --apks rebuilt.apk \
    --ks ~/apk-testing.keystore \
    --ksAlias testing \
    --ksPass your_password

3.5 Common Signing Errors

Error Cause Fix
INSTALL_FAILED_UPDATE_INCOMPATIBLE Different signing key adb uninstall then reinstall
INSTALL_PARSE_FAILED_NO_CERTIFICATES Not signed Sign with apksigner
INSTALL_FAILED_SESSION_INVALID Splits with different keys Sign ALL splits with same keystore
zipalign after sign Signature broken Always zipalign first

3.6 Key Rotation (v3)

# Sign with new key, providing old key's lineage
apksigner sign \
    --ks new-release.keystore \
    --ks-key-alias newkey \
    --v3-signing-enabled true \
    --lineage /path/to/lineage-file \
    rebuilt_aligned.apk

4. Deep Dives

The following reference files contain detailed information on specific topics. Load them on demand based on your task:

Topic File Covers
Split APKs & GApps references/split-and-gapps.md Split APK formats, merging, MicroG, signature spoofing, Play Integrity
Testing & Containers references/testing-containers.md Redroid, Waydroid setup and workflows
Emulator Testing references/emulator-testing.md AVD setup, Frida, ADB commands, x86/ARM translation
Troubleshooting references/troubleshooting.md AAPT2 errors, advanced patching, delivery, E2E workflow

References