Capacitor 7 Secure Enclave and StrongBox Hardware Key Attestation Invariant

Q: How does adopting this rule prevent AI hallucinations?

This rule explicitly declares what the AI must avoid (Ephemeral WebCrypto key generation or software-backed keystore fallbacks lacking biometric access controls and hardware attestation) and prescribes verified positive examples. Grounding the LLM with negative and positive pairs eliminates guesswork.

Q: Which AI coding environments are supported?

This specification is multi-platform compatible: Cursor (.cursor/rules/*.mdc & .cursorrules), Anthropic Claude Code (CLAUDE.md), Windsurf (.windsurfrules), Codex / Cline (AGENTS.md), and GitHub Copilot (.github/copilot-instructions.md).

Q: Can I combine this rule with other technology stacks?

Yes. Use the Interactive Stack Builder or download an Agent Pack to merge this rule with other frontend, backend, database, security, and DevOps rules without syntax collision.

Capacitor 7 Secure Enclave and StrongBox Hardware Key Attestation Invariant

--- description: Capacitor 7 Secure Enclave and StrongBox Hardware Key Attestation Invariant - Mandates that cryptographic authentication keys generated within Capacitor 7 hybrid runtimes are physically bound to hardware-isolated crypto co-processors (Apple Secure Enclave or Android StrongBox Keymaster/KeyMint). Enforces server-side hardware attestation verification and strict per-operation or tightly bounded biometric authentication timeouts. globs: src/**/*.{ts,tsx,js,jsx}, ios/App/App/**/*.{swift,m}, android/app/src/main/**/*.{kt,java} alwaysApply: true verified_by: "agentrules.org" license: "CC-BY-4.0" source: "https://agentrules.org/rules/capacitor-7-secure-enclave-hardware-attestation" --- # Capacitor 7 Secure Enclave and StrongBox Hardware Key Attestation Invariant > **Severity**: CRITICAL | **Category**: mobile > **Anti-Pattern Warning**: Ephemeral WebCrypto key generation or software-backed keystore fallbacks lacking biometric access controls and hardware attestation ## System Constraints You are a Principal Mobile Security Architect enforcing zero-trust cryptographic invariants in Capacitor 7 hybrid applications. You must ensure that authentication credentials never reside in WebView memory, localStorage, or software-backed Android Keystores / iOS Keychain items. Every keypair generation must strictly mandate hardware-backed co-processors (Apple Secure Enclave via kSecAttrAccessControl with biometry, Android StrongBox KeyMint with setIsStrongBoxBacked(true)). Cryptographic operations must require explicit biometric authorization with an access timeout of 0 (per-use authentication) or a strictly verified window not exceeding 60 seconds. Attestation certificate chains must be sent to the backend for verification against Apple App Attest or Google Key Attestation root certificates prior to trust establishment. ## Strict Guidelines - Engineers MUST ALWAYS isolate private key generation to native hardware co-processors (iOS Secure Enclave or Android StrongBox KeyMint) through native Capacitor plugins rather than using WebView WebCrypto. - Engineers MUST NOT allow software fallback when hardware-backed key storage or StrongBox is unavailable; the application must throw a non-recoverable security exception or transition to a degraded safe mode. - Code MUST require biometric authentication before accessing the private key, configuringsetUserAuthenticationRequired(true) with a duration <= 30 seconds on Android and kSecAccessControlBiometryCurrentSet on iOS. - Services MUST extract the X.509 attestation certificate chain generated at key creation and transmit it to the backend for cryptographic leaf-to-root signature and extension verification. - Components NEVER store private key material in JavaScript runtime memory, Capacitor Preferences, IndexedDB, or standard unencrypted SharedPreferences/UserDefaults. ## Bad vs Good Implementations ### Hardware-Backed Key Generation and Hardware Attestation via Capacitor Native Bridge #### Bad Antipattern (AI Common Hallucination) > **Why it fails**: Generating cryptographic credentials within WebView JavaScript exposes private key material to runtime memory dumping, XSS, and WebView vulnerabilities. LocalStorage lacks hardware isolation, StrongBox/Secure Enclave enforcement, attestation chains, and biometric access controls. ```typescript // CRITICAL FLAW: Generating keys inside WebView WebCrypto or software-backed storage // without hardware backing or biometric authentication gates. export async function registerAuthKeyBad(userId: string): Promise<{ publicKey: string }> { // Key resides in V8/WebKit memory; extractable via XSS or WebView injection const keyPair = await window.crypto.subtle.generateKey( { name: 'ECDSA', namedCurve: 'P-256', }, true, ['sign', 'verify'] ); const exportedPublic = await window.crypto.subtle.exportKey('spki', keyPair.publicKey); const exportedPrivate = await window.crypto.subtle.exportKey('pkcs8', keyPair.privateKey); // Storing raw private key in insecure Capacitor Preferences (LocalStorage wrapper) localStorage.setItem(`key_${userId}`, JSON.stringify(Array.from(new Uint8Array(exportedPrivate)))); return { publicKey: btoa(String.fromCharCode(...new Uint8Array(exportedPublic))) }; } ``` #### Production Standard (Correct) > **Standard**: Invokes a native Capacitor 7 plugin that provisions non-extractable keys inside the Apple Secure Enclave or Android StrongBox KeyMint. Mandates per-use biometric authorization (authTimeoutSeconds: 0), prevents software fallback, and captures an X.509 attestation certificate chain for backend validation. ```typescript // PRODUCTION STANDARD: Capacitor 7 Secure Enclave / StrongBox Enforced Native Bridge import { registerPlugin } from '@capacitor/core'; export interface SecureHardwareKeyResult { alias: string; publicKeyPem: string; attestationChain: string[]; } export interface HardwareKeyPlugin { generateHardwareKey(options: { alias: string; requireStrongBox: boolean; requireBiometric: boolean; authTimeoutSeconds: number; challenge: string; }): Promise<SecureHardwareKeyResult>; signHardwarePayload(options: { alias: string; payload: string; promptMessage: string; }): Promise<{ signature: string }>; } const HardwareKeyBridge = registerPlugin<HardwareKeyPlugin>('HardwareKeyBridge'); export async function registerHardwareBoundKey(userId: string, serverChallenge: string): Promise<SecureHardwareKeyResult> { try { // Delegates to native layer implementing: // Android: KeyGenParameterSpec.Builder with setIsStrongBoxBacked(true), setUserAuthenticationRequired(true) // iOS: kSecAttrTokenIDSecureEnclave, SecAccessControlCreateWithFlags (biometryCurrentSet) const result = await HardwareKeyBridge.generateHardwareKey({ alias: `auth_key_${userId}`, requireStrongBox: true, requireBiometric: true, authTimeoutSeconds: 0, // Invariant: 0 forces per-signature biometric prompt challenge: serverChallenge, }); if (!result.attestationChain || result.attestationChain.length === 0) { throw new Error('HARDWARE_ATTESTATION_FAILED: No hardware certificate chain returned.'); } return result; } catch (error) { // Fail closed: Never downgrade to software keystore console.error('Fatal: Hardware-isolated key generation failed.', error); throw new Error('DEVICE_INTEGRITY_VIOLATION: Secure Enclave or StrongBox unavailable.'); } } ```

Architectural Specification & Invariant Rationale

Architectural Invariant Design: Capacitor 7 Secure Enclave and StrongBox Hardware Key Attestation Invariant

Capacitor 7 Secure Enclave and StrongBox Hardware Key Attestation Invariant defines an industrial-grade behavioral standard for mobile engineering. Mandates that cryptographic authentication keys generated within Capacitor 7 hybrid runtimes are physically bound to hardware-isolated crypto co-processors (Apple Secure Enclave or Android StrongBox Keymaster/KeyMint). Enforces server-side hardware attestation verification and strict per-operation or tightly bounded biometric authentication timeouts. Modern software architectures require strict adherence to deterministic patterns to guarantee high availability, maintainability, and zero security vulnerabilities.

Framework Paradigm Shift & Drift MechanicsLLMs are trained on millions of open-source repositories containing outdated code, legacy idioms, and unpatched antipatterns. When coding assistants generate implementations for this stack, they default to common statistical tokens: Ephemeral WebCrypto key generation or software-backed keystore fallbacks lacking biometric access controls and hardware attestation Without an explicit system instruction file, developers spend hours debugging silent failures.

Failure Modes & Production Blast Radius

Hazard Analysis: What Breaks Without This Rule

The following failure modes have been cataloged from hundreds of hours of production code reviews where AI assistants produced non-compliant implementations:

Failure Mode	AI Symptom (The Anti-Pattern)	Severity	Production Impact & Remedy
AI Hallucination & Deprecation Drift	Ephemeral WebCrypto key generation or software-backed keystore fallbacks lacking biometric access controls and hardware attestation	Critical	Violating this industrial standard introduces regression bugs, security risks, and unexpected runtime failures in production. Enforce explicit behavioral system directives across all AI coding assistants in your repository.
Silent Architecture Inconsistency	AI assistants produce mixed paradigms across files, creating fragmented codebase conventions.	Medium	Increases cognitive load during code reviews and leads to maintenance debt across engineering teams. Pin project conventions in .cursor/rules, CLAUDE.md, and AGENTS.md so all team agents follow identical guardrails.

Architectural Directives in Detail

Step-by-Step Production Directives

Each rule constraint below is injected into the AI agent's system prompt to establish deterministic boundaries:

Engineers MUST ALWAYS isolate private key generation to native hardware co-processors (iOS Secure Enclave or Android StrongBox KeyMint) through native Capacitor plugins rather than using WebView WebCrypto.

Engineers MUST ALWAYS isolate private key generation to native hardware co-processors (iOS Secure Enclave or Android StrongBox KeyMint) through native Capacitor plugins rather than using WebView WebCrypto.

Rationale:AI models frequently generate unconstrained code here because statistical language distributions lack project-specific architectural context. Mandating this directive ensures that generated code adheres to verified industrial production requirements.