gplay-signing-setup

What this skill does

# Android App Signing Setup

Use this skill when you need to set up or manage app signing for Google Play.

## Understanding Android App Signing

Android apps must be signed with a certificate before upload. Two signing approaches:

1. **App Signing by Google Play** (Recommended) - Google manages your signing key
2. **Manual Signing** (Legacy) - You manage your signing key

## Create a New Keystore

### Generate keystore
```bash
keytool -genkey -v \
  -keystore release.keystore \
  -alias my-app-key \
  -keyalg RSA \
  -keysize 2048 \
  -validity 10000
```

**You'll be prompted for:**
- Keystore password (store securely!)
- Key password (can be same as keystore password)
- Your name/organization details

### Keystore file location
- **Development**: Keep locally, never commit to git
- **Production**: Store in secure location (password manager, secrets vault)
- **CI/CD**: Use encrypted secrets

## Configure Gradle Signing

### gradle.properties (gitignored)
```properties
KEYSTORE_FILE=/path/to/release.keystore
KEYSTORE_PASSWORD=your_keystore_password
KEY_ALIAS=my-app-key
KEY_PASSWORD=your_key_password
```

### app/build.gradle
```groovy
android {
    signingConfigs {
        release {
            storeFile file(project.property('KEYSTORE_FILE'))
            storePassword project.property('KEYSTORE_PASSWORD')
            keyAlias project.property('KEY_ALIAS')
            keyPassword project.property('KEY_PASSWORD')
        }
    }

    buildTypes {
        release {
            signingConfig signingConfigs.release
        }
    }
}
```

### Using environment variables (CI/CD)
```groovy
android {
    signingConfigs {
        release {
            storeFile file(System.getenv("KEYSTORE_FILE") ?: "release.keystore")
            storePassword System.getenv("KEYSTORE_PASSWORD")
            keyAlias System.getenv("KEY_ALIAS")
            keyPassword System.getenv("KEY_PASSWORD")
        }
    }
}
```

## Play App Signing Setup

### Enable Play App Signing (New App)

1. **Build and sign AAB** with upload key:
   ```bash
   ./gradlew bundleRelease
   ```

2. **Upload AAB** to Play Console:
   ```bash
   gplay release \
     --package com.example.app \
     --track internal \
     --bundle app-release.aab
   ```

3. **Google Play generates app signing key** automatically

4. **Download upload certificate**:
   - Go to Play Console → App → Setup → App signing
   - Download "Upload certificate" (will be used for future uploads)

### Migrate Existing App to Play App Signing

If your app uses manual signing:

1. **Export upload key**:
   ```bash
   keytool -export -rfc \
     -keystore release.keystore \
     -alias my-app-key \
     -file upload_cert.pem
   ```

2. **Encrypt private key** (required by Google):
   ```bash
   # Generate password for encryption
   openssl rand -base64 32 > encryption_password.txt

   # Export and encrypt private key
   keytool -importkeystore \
     -srckeystore release.keystore \
     -destkeystore encrypted.p12 \
     -deststoretype PKCS12 \
     -srcalias my-app-key \
     -deststorepass $(cat encryption_password.txt)
   ```

3. **Upload to Play Console**:
   - Go to Play Console → App → Setup → App signing
   - Choose "Export and upload a key"
   - Upload encrypted.p12 and encryption_password.txt

4. **Download new upload key**:
   - After migration, download new upload certificate
   - Use this for all future uploads

## Verify Keystore

### List keys in keystore
```bash
keytool -list -v -keystore release.keystore
```

### Check certificate validity
```bash
keytool -list -v \
  -keystore release.keystore \
  -alias my-app-key \
  | grep Valid
```

### Extract certificate fingerprint
```bash
# SHA-256 (for Firebase, etc.)
keytool -list -v \
  -keystore release.keystore \
  -alias my-app-key \
  | grep SHA256
```

## Verify APK/AAB Signature

### Check AAB signature
```bash
jarsigner -verify -verbose -certs app-release.aab
```

### Check APK signature
```bash
jarsigner -verify -verbose -certs app-release.apk
```

## CI/CD Signing

### GitHub Actions Example
```yaml
- name: Decode keystore
  run: |
    echo "${{ secrets.KEYSTORE_BASE64 }}" | base64 -d > release.keystore

- name: Build signed AAB
  env:
    KEYSTORE_FILE: release.keystore
    KEYSTORE_PASSWORD: ${{ secrets.KEYSTORE_PASSWORD }}
    KEY_ALIAS: ${{ secrets.KEY_ALIAS }}
    KEY_PASSWORD: ${{ secrets.KEY_PASSWORD }}
  run: |
    ./gradlew bundleRelease

- name: Clean up keystore
  if: always()
  run: rm -f release.keystore
```

### Store keystore as base64
```bash
# Encode keystore to base64
base64 -i release.keystore -o keystore_base64.txt

# Add to GitHub Secrets as KEYSTORE_BASE64
```

## Upload Certificate Management

### Register upload certificate for existing app
If you lose your upload key:

1. **Generate new keystore** (as shown above)

2. **Export certificate**:
   ```bash
   keytool -export -rfc \
     -keystore new-upload.keystore \
     -alias my-app-key \
     -file new_upload_cert.pem
   ```

3. **Contact Google Play support** to reset upload key:
   - Go to Play Console → Help
   - Request upload certificate reset
   - Provide new_upload_cert.pem

## Security Best Practices

### DO:
- ✅ Use strong passwords (16+ characters)
- ✅ Store keystore in multiple secure locations
- ✅ Use different keys for different apps
- ✅ Enable Play App Signing
- ✅ Keep upload key separate from production
- ✅ Document key details securely (not passwords!)
- ✅ Set calendar reminder for key expiration (10-25 years)

### DON'T:
- ❌ Commit keystores to git
- ❌ Share keystores via email/chat
- ❌ Use weak or obvious passwords
- ❌ Store passwords in code
- ❌ Forget to backup keystores
- ❌ Use same key for debug and release

## Keystore Backup Strategy

### What to backup:
1. Keystore file (`release.keystore`)
2. Key alias name
3. Keystore password (in password manager)
4. Key password (in password manager)

### Where to backup:
- Password manager (1Password, LastPass, etc.)
- Encrypted cloud storage
- Company secrets vault
- Physical secure storage (for enterprise)

### Test restore process:
```bash
# Verify you can use the backup
keytool -list -v -keystore backup/release.keystore
```

## Troubleshooting

### "jarsigner: unable to sign jar"
- Check keystore password is correct
- Verify keystore file path
- Ensure keystore alias exists

### "Failed to read key from keystore"
- Key alias might be wrong
- Key password might be wrong
- Keystore might be corrupted

### "Upload certificate doesn't match"
- You're using wrong keystore
- Keystore was regenerated (contact support)
- Using app signing key instead of upload key

### Lost keystore?
- If using Play App Signing: Contact Google to reset upload key
- If not using Play App Signing: Cannot recover, must publish new app

## Multiple Apps, Multiple Keys

### Organize multiple keystores
```
~/keystores/
├── app1-release.keystore
├── app2-release.keystore
└── app3-release.keystore
```

### Use different gradle.properties per app
```properties
# app1/gradle.properties
KEYSTORE_FILE=~/keystores/app1-release.keystore
KEY_ALIAS=app1-key

# app2/gradle.properties
KEYSTORE_FILE=~/keystores/app2-release.keystore
KEY_ALIAS=app2-key
```

## Key Rotation

Android apps are typically signed with long-lived keys (10-25 years), but if you need to rotate:

1. **Only possible with Play App Signing enabled**
2. **Contact Google Play Support** to rotate app signing key
3. **Upload new upload certificate** when prompted
4. **All future builds** must use new upload key

## Documentation Template

Keep this info in your password manager:

```
App Name: My Awesome App
Package: com.example.app
Keystore File: release.keystore (backed up in Dropbox)
Keystore Password: [IN PASSWORD MANAGER]
Key Alias: my-app-key
Key Password: [IN PASSWORD MANAGER]
Certificate Validity: Valid until 2035-02-05
SHA-256 Fingerprint: AB:CD:EF:12:...
Play App Signing: Enabled
Notes: Upload key only, Google manages app signing key
```