krutikJain/android-security-best-practices

Android Security Best Practices

When To Use

• Use this skill when the request is about: android security review, secret handling android app, exported component security android.
• Primary outcome: Apply Android app security guidance around secrets, storage, network trust, exported components, and least privilege.
• Read references/patterns.md when you need the attack-surface checklist or the storage/network/component decision matrix.
• Read references/scenarios.md for manifest, backup, WebView, and release-hardening review paths.
• Handoff skills when the scope expands:
• android-modernization-upgrade
• android-ci-cd-release-playstore

Workflow

1. Inventory the attack surface first: exported components, intent/deep link entry points, file sharing, WebView usage, local storage, logs, backups, and network trust config.
2. Remove avoidable risk before hardening details: prefer platform pickers and choosers, internal storage, server-issued short-lived tokens, and least-privilege permissions instead of shipping broad access or long-lived secrets.
3. Lock the remaining boundaries explicitly with android:exported, component permissions, FileProvider, networkSecurityConfig, debug-only trust anchors, and immutable PendingIntents.
4. Review sensitive surfaces that often regress in Android apps: WebView JavaScript bridges, backup/data extraction rules, cleartext exceptions, log redaction, and same-developer IPC assumptions.
5. Validate the release posture with reproducible checks, then document residual risks and whether backend enforcement or Play Integrity is advisory or blocking.

Guardrails

• Treat client-side secrets as recoverable by attackers; move trust decisions and privileged API access server-side whenever possible.
• Export components only when there is a real external caller, and permission-protect or signature-protect them when the contract is private.
• Use network security config to scope debug trust anchors or cleartext exceptions instead of broad manifest toggles.
• Redact logs, review backups, and keep sensitive data out of shared external storage by default.

Anti-Patterns

• Hiding API keys in resources, the NDK, or obfuscation and calling that secure.
• Leaving android:exported or intent filters ambiguous on launchable or IPC components.
• Sharing files through raw file paths or overly broad storage permissions instead of FileProvider and system surfaces.
• Pinning certificates without an operational rotation story or fallback plan.

Review Focus

• Exported activities, services, receivers, and providers with clear ownership and caller expectations.
• Secrets, tokens, and backend trust assumptions.
• Network trust, debug overrides, cleartext usage, and certificate handling.
• File sharing, backups, logs, and user-data leakage paths.
• Abuse signals such as Play Integrity only as layered defense, never as the sole authorization model.

Examples

Happy path

• Scenario: Audit manifests and sharing surfaces for explicit exports, permissions, and FileProvider usage.
• Command: rg -n "android:exported|android:permission|FileProvider|grantUriPermissions" examples

Edge case

• Scenario: Catch insecure backup or network defaults before a release candidate goes out.
• Command: rg -n "networkSecurityConfig|usesCleartextTraffic|allowBackup|fullBackupContent|dataExtractionRules" examples

Failure recovery

• Scenario: Separate app hardening from modernization or release-pipeline requests.
• Command: python3 scripts/eval_triggers.py --skill android-security-best-practices

Done Checklist

• Every externally reachable component has explicit exposure and caller constraints.
• Secrets, tokens, and trust decisions are not relying on obscurity in the client app.
• Network, backup, logging, and sharing behavior have explicit release-safe defaults.
• Residual risks and any backend dependencies are documented with clear follow-up work.

Official References

• https://developer.android.com/privacy-and-security/security-best-practices
• https://developer.android.com/privacy-and-security/security-tips
• https://developer.android.com/privacy-and-security/risks/unsafe-exported-components
• https://developer.android.com/privacy-and-security/risks/access-control-to-exported-components
• https://developer.android.com/privacy-and-security/security-config
• https://developer.android.com/privacy-and-security/minimize-permission-requests
• https://developer.android.com/google/play/integrity/overview