Capacitor 7 Deep-Link Intent Cryptographic Verification and Payload Sanitization

--- description: Capacitor 7 Deep-Link Intent Cryptographic Verification and Payload Sanitization - Enforces strict origin validation, HMAC/Ed25519 signature verification, and schema sanitization on all incoming Capacitor 7 deep links, universal links, and app intent payloads before bridge dispatch. Prevents open intent redirection, parameter injection, and cross-site scripting (XSS) attacks across the native-to-web dynamic bridge boundary. globs: src/app/**/*.{ts,tsx}, src/router/**/*.{ts,tsx}, src/listeners/**/*.{ts,tsx}, ios/App/App/**/*.{swift,m}, android/app/src/main/**/*.{java,kt} alwaysApply: true verified_by: "agentrules.org" license: "CC-BY-4.0" source: "https://agentrules.org/rules/capacitor-7-deep-link-verification-sanitization" --- # Capacitor 7 Deep-Link Intent Cryptographic Verification and Payload Sanitization > **Severity**: CRITICAL | **Category**: mobile > **Anti-Pattern Warning**: Unvalidated Ingress Routing & Dynamic Bridge Execution from Untrusted Native Intents ## System Constraints You are a Principal Mobile Security Architect enforcing the Capacitor 7 Deep-Link Intent Verification & Payload Sanitization Standard. Untrusted external actors can trigger arbitrary custom URL schemes and manipulate intent payloads. You must enforce zero-trust validation: never pass raw deep-link URLs, intent query parameters, or state payloads to web routers, native plugins, or dynamic evaluation bridges without cryptographic signature verification (HMAC-SHA256/Ed25519) and strict runtime schema filtering using canonical Zod parsers. ## Strict Guidelines - Engineers MUST ALWAYS register App.addListener('appUrlOpen', ...) inside a centralized, hardened IngressGateway service before triggering any navigation or bridge calls. - Engineers MUST ALWAYS validate the incoming URL host, scheme, and pathname against a strict compile-time allowlist; wildcards or substring checks like .includes() are strictly forbidden. - Engineers MUST ALWAYS verify cryptographic signatures (e.g., HMAC-SHA256 token or signed nonce) on sensitive action parameters (such as auth tokens, payment flows, or state reset) before routing. - Engineers MUST NOT pass raw deep-link query parameters directly into window.location, Capacitor bridge calls, or client-side routers (e.g., React Router, Vue Router, Ionic Nav). - Code MUST parse and sanitize all route parameters using strict runtime schemas (e.g., Zod with .strip() or .strict()) to reject prototype pollution or unexpected injection vectors. - Services MUST reject and log any universal links or deep links whose origin fails RFC 3986 canonicalization or violates expected multi-tenant tenant-ID bounds. ## Bad vs Good Implementations ### Vulnerable Direct Router Dispatch vs. Cryptographically Verified & Sanitized Ingress Handler #### Bad Antipattern (AI Common Hallucination) > **Why it fails**: Directly trusting event.url enables attackers to hijack custom URL schemes, inject arbitrary auth tokens into persistent storage, and trigger open redirects leading to phishing or sensitive context extraction. ```typescript import { App, URLOpenListenerEvent } from '@capacitor/app'; import { Router } from './router'; // VULNERABLE: Direct dispatch of untrusted native intent payload to dynamic router export function initializeDeepLinks(): void { App.addListener('appUrlOpen', (event: URLOpenListenerEvent) => { const url = new URL(event.url); const targetPath = url.searchParams.get('redirectUrl'); const authToken = url.searchParams.get('token'); if (targetPath) { // CRITICAL: Open redirect vulnerability & token injection via custom URL scheme if (authToken) { localStorage.setItem('auth_session', authToken); } Router.navigate(targetPath); } }); } ``` #### Production Standard (Correct) > **Standard**: Validates origin against an immutable allowlist, enforces RFC 3986 parsing, validates expiration timestamps, enforces strict schema matching via Zod, and cryptographically proves authenticity using HMAC-SHA256 prior to routing. ```typescript import { App, URLOpenListenerEvent } from '@capacitor/app'; import { z } from 'zod'; import { hmacSha256Verify } from './crypto-utils'; import { Router } from './router'; const ALLOWED_HOSTS = new Set(['app.example.com']); const ALLOWED_SCHEMES = new Set(['https:', 'com.example.app:']); const DeepLinkPayloadSchema = z.object({ targetRoute: z.string().regex(/^\/[a-zA-Z0-9_-]+(\?.*)?$/), timestamp: z.coerce.number().refine(ts => Math.abs(Date.now() - ts) < 300000, 'Expired link'), signature: z.string().min(64).max(64) }).strict(); export function initializeDeepLinks(sharedHmacKey: string): void { App.addListener('appUrlOpen', async (event: URLOpenListenerEvent) => { try { const parsedUrl = new URL(event.url); if (!ALLOWED_SCHEMES.has(parsedUrl.protocol) || !ALLOWED_HOSTS.has(parsedUrl.hostname)) { console.error('Security Violation: Disallowed deep-link origin', parsedUrl.origin); return; } const rawParams = Object.fromEntries(parsedUrl.searchParams.entries()); const validated = DeepLinkPayloadSchema.parse(rawParams); const dataToVerify = `route=${validated.targetRoute}&ts=${validated.timestamp}`; const isValid = await hmacSha256Verify(sharedHmacKey, dataToVerify, validated.signature); if (!isValid) { console.error('Security Violation: Invalid payload signature'); return; } Router.navigate(validated.targetRoute); } catch (err) { console.error('Failed to safely process deep-link intent', err); } }); } ```

Architectural Specification & Invariant Rationale

Architectural Invariant Design: Capacitor 7 Deep-Link Intent Cryptographic Verification and Payload Sanitization

Capacitor 7 Deep-Link Intent Cryptographic Verification and Payload Sanitization defines an industrial-grade behavioral standard for mobile engineering. Enforces strict origin validation, HMAC/Ed25519 signature verification, and schema sanitization on all incoming Capacitor 7 deep links, universal links, and app intent payloads before bridge dispatch. Prevents open intent redirection, parameter injection, and cross-site scripting (XSS) attacks across the native-to-web dynamic bridge boundary. 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: Unvalidated Ingress Routing & Dynamic Bridge Execution from Untrusted Native Intents 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	Unvalidated Ingress Routing & Dynamic Bridge Execution from Untrusted Native Intents	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 register App.addListener('appUrlOpen', ...) inside a centralized, hardened IngressGateway service before triggering any navigation or bridge calls.

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.