Tauri 2.0 Capability-Based IPC Permission Boundary Guardrail

--- description: Tauri 2.0 Capability-Based IPC Permission Boundary Guardrail - Enforces strict principle-of-least-privilege boundaries between untrusted webview DOM contexts and native host plugins in Tauri 2.0 applications. Prohibits wildcard plugin capabilities, mandates path-scoped filesystem permissions, and enforces defensive validation on custom host IPC commands. globs: src-tauri/capabilities/**/*.json, src-tauri/tauri.conf.json, src-tauri/src/**/*.rs, src/**/*.{ts,tsx} alwaysApply: true verified_by: "agentrules.org" license: "CC-BY-4.0" source: "https://agentrules.org/rules/tauri-v2-capability-ipc-permission-guardrail" --- # Tauri 2.0 Capability-Based IPC Permission Boundary Guardrail > **Severity**: CRITICAL | **Category**: mobile > **Anti-Pattern Warning**: Over-Permissive Wildcard Capabilities and Path-Traversal Vulnerable IPC Handlers in Tauri 2.0 ## System Constraints You are a Principal Software Architect enforcing Tauri 2.0 Capability-Based Security and IPC Boundary Invariants. Tauri 2.0 replaces the legacy monolithic v1 allowlist with fine-grained capabilities mapped to specific windows and webviews. You must guarantee that no untrusted webview execution context can invoke unconstrained native host operations, traverse host filesystems outside sandboxed directories, or execute arbitrary shell processes. ## Strict Guidelines - Engineers MUST ALWAYS isolate permissions into declarative capability sets within `src-tauri/capabilities/*.json` targeting explicit window labels. - Engineers MUST NOT grant blanket or wildcard permissions such as `fs:allow-all`, `shell:allow-all`, or `http:default` without strict domain or path constraints. - Code MUST restrict filesystem operations exclusively to application sandboxes (`$APPDATA`, `$RESOURCE`, `$TEMP`) using explicit scope definitions in capability manifests. - Services MUST canonicalize and sanitize incoming path and command arguments inside custom Rust `#[tauri::command]` handlers to prevent path traversal attacks. - Components NEVER execute raw shell commands directly from the DOM; all native orchestration MUST be mediated by domain-specific host-side commands with fixed parameter validation. ## Bad vs Good Implementations ### Tauri 2.0 Capability Definition & Front-End IPC Scoping #### Bad Antipattern (AI Common Hallucination) > **Why it fails**: Declaring wildcard permissions like `fs:allow-all` grants a compromised webview full access to read and write arbitrary sensitive host files. Invoking unconstrained shell commands from the client-side allows remote code execution if any XSS vulnerability exists. ```typescript // Capability Anti-Pattern: Wildcard permissions allow unconstrained native access // src-tauri/capabilities/default.json // { // "permissions": ["core:default", "fs:allow-all", "shell:allow-execute"] // } import { invoke } from '@tauri-apps/api/core'; import { readFile } from '@tauri-apps/plugin-fs'; export async function loadUserDocument(untrustedPath: string): Promise<string> { // VULNERABLE: Direct access to arbitrary host paths via unconstrained fs capability const contents = await readFile(untrustedPath); return new TextDecoder().decode(contents); } export async function runHostProcess(command: string): Promise<void> { // VULNERABLE: Front-end controls arbitrary execution await invoke('execute_arbitrary_command', { command }); } ``` #### Production Standard (Correct) > **Standard**: Defines a strict capability scope restricting the webview to `$APPDATA/documents/*`. Validates input in the frontend to block directory traversal sequences before calling the IPC boundary, ensuring defense-in-depth across the webview-host boundary. ```typescript // Capability Production Invariant: Sandboxed scopes & domain-specific host command // src-tauri/capabilities/mobile-user-docs.json // { // "identifier": "mobile-user-docs", // "windows": ["main"], // "permissions": [ // "core:default", // { // "identifier": "fs:allow-read-file", // "allow": [{ "path": "$APPDATA/documents/*" }] // } // ] // } import { appDataDir, join } from '@tauri-apps/api/path'; import { readTextFile } from '@tauri-apps/plugin-fs'; const FILENAME_REGEX = /^[a-zA-Z0-9_-]+\.json$/; export async function loadUserDocument(fileName: string): Promise<string> { if (!FILENAME_REGEX.test(fileName)) { throw new Error('Invalid document name: Path traversal characters forbidden'); } const appDir = await appDataDir(); const safePath = await join(appDir, 'documents', fileName); // SAFE: Guarded by client validation AND the native Tauri 2.0 capability scope ($APPDATA/documents/*) return await readTextFile(safePath); } ```

Architectural Specification & Invariant Rationale

Architectural Invariant Design: Tauri 2.0 Capability-Based IPC Permission Boundary Guardrail

Tauri 2.0 Capability-Based IPC Permission Boundary Guardrail defines an industrial-grade behavioral standard for mobile engineering. Enforces strict principle-of-least-privilege boundaries between untrusted webview DOM contexts and native host plugins in Tauri 2.0 applications. Prohibits wildcard plugin capabilities, mandates path-scoped filesystem permissions, and enforces defensive validation on custom host IPC commands. 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: Over-Permissive Wildcard Capabilities and Path-Traversal Vulnerable IPC Handlers in Tauri 2.0 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	Over-Permissive Wildcard Capabilities and Path-Traversal Vulnerable IPC Handlers in Tauri 2.0	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 permissions into declarative capability sets within `src-tauri/capabilities/*.json` targeting explicit window labels.

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.