Capacitor 7 Native Bridge Origin Isolation and Scheme Invariant Guardrail

--- description: Capacitor 7 Native Bridge Origin Isolation and Scheme Invariant Guardrail - Capacitor 7 native bridge invocations must be cryptographically bound to immutable custom schemes and verified origin domains. Failure to enforce origin checks and scheme invariants exposes native host plugins (Keychain, Keystore, Camera, Filesystem) to untrusted third-party script injection via DOM XSS, MITM webviews, or arbitrary remote navigations. globs: capacitor.config.ts, android/app/src/main/**/*.kt, android/app/src/main/**/*.java, ios/App/App/**/*.swift, src/**/*.{ts,tsx} alwaysApply: true verified_by: "agentrules.org" license: "CC-BY-4.0" source: "https://agentrules.org/rules/capacitor-7-origin-isolation-scheme-invariant" --- # Capacitor 7 Native Bridge Origin Isolation and Scheme Invariant Guardrail > **Severity**: CRITICAL | **Category**: mobile > **Anti-Pattern Warning**: Permissive Remote Navigation with Unvalidated Native Bridge Invocations Across Arbitrary Origins ## System Constraints You are a Principal Mobile Systems Architect enforcing Capacitor 7 security boundaries. Mandate native bridge origin isolation and scheme invariants across all webview-to-native communication. Never allow wildcard navigations or unverified IPC message origins. ## Strict Guidelines - Engineers MUST ALWAYS restrict `server.allowNavigation` in `capacitor.config.ts` to strictly bounded, explicit production domains and reject wildcards (`*`). - Engineers MUST NOT permit arbitrary HTTP/HTTPS endpoints or remote origins to access the Capacitor native bridge runtime. - Custom native plugins MUST verify the caller origin via the bridge's webview URL before executing privileged native operations (biometrics, secure storage, file I/O). - Native configurations MUST enforce explicit secure scheme pairs (e.g., `androidScheme: 'https'` with custom hostname, or strictly validated custom app schemes) to guarantee Origin header immutability. - Components NEVER execute raw `window.Capacitor.toNative()` or listen to unverified `window.postMessage` channels bypassing Capacitor's internal plugin registry. ## Bad vs Good Implementations ### Capacitor 7 Server Configuration and Scheme Hardening #### Bad Antipattern (AI Common Hallucination) > **Why it fails**: Configuring allowNavigation to '*' and using cleartext HTTP enables any loaded remote resource or injected iframe to access window.Capacitor and invoke sensitive native APIs via the bridge. ```typescript import { CapacitorConfig } from '@capacitor/cli'; // VULNERABLE: Wildcard navigation and unconstrained origins expose bridge const config: CapacitorConfig = { appId: 'com.example.app', appName: 'ExampleApp', webDir: 'dist', server: { // Anti-pattern: Wildcards allow malicious injected frames to call native bridge allowNavigation: ['*'], cleartext: true, androidScheme: 'http' } }; export default config; ``` #### Production Standard (Correct) > **Standard**: Restricts the webview runtime to a sealed, internal HTTPS origin (localapp.internal) and limits external navigations to explicitly enumerated production endpoints with cleartext disabled. ```typescript import { CapacitorConfig } from '@capacitor/cli'; // HARDENED: Strict origin confinement and secure scheme enforcement const config: CapacitorConfig = { appId: 'com.example.app', appName: 'ExampleApp', webDir: 'dist', server: { // Invariant: Navigation is strictly restricted to trusted app origins androidScheme: 'https', hostname: 'localapp.internal', allowNavigation: [ 'https://api.example.com' ], cleartext: false } }; export default config; ``` ### Custom Plugin Origin Verification Invariant #### Bad Antipattern (AI Common Hallucination) > **Why it fails**: The plugin does not verify caller provenance; any script running in the webview (including XSS payloads or third-party webview content) can invoke retrieveMasterKey. ```typescript import { Plugin, PluginCall } from '@capacitor/core'; // VULNERABLE: Plugin executes without checking invoking origin export class SecureVaultPlugin { async retrieveMasterKey(call: PluginCall): Promise<void> { // Anti-pattern: Blindly trusts any caller from the webview context const secret = await fetchSecureKeyFromHardware(); call.resolve({ secret }); } } ``` #### Production Standard (Correct) > **Standard**: Validates the execution origin against the immutable trusted internal scheme before dispatching sensitive hardware-backed operations, preventing malicious web contexts from accessing the native boundary. ```typescript import { Plugin, PluginCall } from '@capacitor/core'; const TRUSTED_ORIGIN = 'https://localapp.internal'; export class SecureVaultPlugin { async retrieveMasterKey(call: PluginCall): Promise<void> { // Invariant: Validate that call originated from the trusted scheme origin const callerUrl = (call as unknown as { _origin?: string })._origin || window.location.origin; if (callerUrl !== TRUSTED_ORIGIN) { call.reject('SecurityException: Bridge call rejected from unauthorized origin: ' + callerUrl); return; } const secret = await fetchSecureKeyFromHardware(); call.resolve({ secret }); } } ```

Architectural Specification & Invariant Rationale

Architectural Invariant Design: Capacitor 7 Native Bridge Origin Isolation and Scheme Invariant Guardrail

Capacitor 7 Native Bridge Origin Isolation and Scheme Invariant Guardrail defines an industrial-grade behavioral standard for mobile engineering. Capacitor 7 native bridge invocations must be cryptographically bound to immutable custom schemes and verified origin domains. Failure to enforce origin checks and scheme invariants exposes native host plugins (Keychain, Keystore, Camera, Filesystem) to untrusted third-party script injection via DOM XSS, MITM webviews, or arbitrary remote navigations. 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: Permissive Remote Navigation with Unvalidated Native Bridge Invocations Across Arbitrary Origins 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	Permissive Remote Navigation with Unvalidated Native Bridge Invocations Across Arbitrary Origins	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 restrict `server.allowNavigation` in `capacitor.config.ts` to strictly bounded, explicit production domains and reject wildcards (`*`).

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.