Tauri Security Csp

Tauri v2 Content-Security-Policy

Tauri injects a CSP into every loaded HTML page by setting an HTTP header (custom protocol) and a <meta http-equiv> tag (fallback). It is opt-in but strongly recommended: missing CSP allows any XSS bug in your frontend to talk to anything reachable from the WebView. Tauri's command ACL still protects Rust, but XSS could exfiltrate from a remote API your frontend uses, manipulate the DOM into clicking trusted commands, etc.

Two configs, one stack

// tauri.conf.json
{
  "app": {
    "security": {
      "csp":     "...prod policy...",
      "devCsp":  "...dev policy (looser)...",
      "dangerousDisableAssetCspModification": false,
      "freezePrototype": true
    }
  }
}

• csp — applied in production (tauri build) and as a baseline.
• devCsp — applied in tauri dev only. If omitted, csp is used in dev too. Use this to add Vite/HMR origins without weakening prod.
• dangerousDisableAssetCspModification — when false (default), Tauri augments your csp to include the directives it needs (see below). When true, your policy ships verbatim — you are responsible for every directive. Only set true if you fully understand the asset/IPC protocols.
• freezePrototype — locks Object.prototype etc. before user JS runs. Cheap defense-in-depth, leave on.

Tauri-specific directives

Even a perfect web CSP will break Tauri without these:

When dangerousDisableAssetCspModification: false, Tauri injects the ipc:, asset:, and https://*.localhost parts of connect-src/img-src/media-src automatically. You still write the rest.

Hash auto-injection

If your bundler emits inline <script> or <style> tags, you'd normally need either 'unsafe-inline' (XSS hole) or SHA-256 hashes in your CSP. Tauri computes the hashes for every inline script/style in the bundled index.html at build time and injects them into the CSP automatically. You write:

script-src 'self'

and Tauri emits:

script-src 'self' 'sha256-abc...=' 'sha256-def...='

For this to work the script/style must be statically present in the bundled HTML — runtime-injected tags still need a different strategy (use nonces, see below). Disabled when dangerousDisableAssetCspModification: true.

Nonces

Tauri does not auto-generate nonces (they need server-side per-request randomness, and Tauri's custom protocol returns static bundles). If you need a nonce for a runtime-injected script (e.g. an analytics tag you splice in after load), you'll have to:

1. Disable CSP modification.
2. Generate a nonce in Rust, inject it into HTML via a custom asset transformer, return that policy in csp_response.

This is rare. Most apps just hash-allow the small set of inline scripts at build time.

frame-ancestors

By default Tauri pages can be embedded as an iframe by any page loaded into another Tauri webview. To prevent that:

frame-ancestors 'self'

If you use the isolation pattern, this directive must also allow the isolation app's origin (http://isolation.localhost or the configured dir) — Tauri handles this automatically when dangerousDisableAssetCspModification is false.

Dev vs prod

In tauri dev with Vite, you need:

• connect-src to include ws://localhost:<port> (HMR socket),
• script-src to include 'unsafe-eval' if your dev bundle uses eval() (most don't anymore, but some HMR runtimes do),
• style-src to include 'unsafe-inline' (Vite injects inline styles for HMR).

Put these only in devCsp. Production should stay strict. See templates/csp-dev.json.

Red flags

• 'unsafe-inline' in script-src for prod — defeats CSP's XSS protection. Use hash injection.
• 'unsafe-eval' in prod — only if a hard dep needs it; document why.
• default-src * — defeats the policy.
• dangerousDisableAssetCspModification: true without a matching audited policy — every release has to re-verify the ipc:/asset: allowances are present.
• Wildcard remote hosts (https://*) — narrow to known API origins.

Reporting

Tauri respects report-uri and report-to. With a custom command endpoint you can sink violations to disk for triage:

report-uri tauri://csp-violation

…and register a custom URI scheme handler that logs the JSON report.

Templates

• templates/csp-strict.json — production-grade CSP fragment, Tauri-aware, hash injection assumed, no unsafe-*.
• templates/csp-dev.json — dev CSP with Vite HMR origins added.

Debugging

• Open devtools → Console for Refused to ... because it violates the Content Security Policy directive ... — the directive name tells you which family.
• A blank window with Refused to connect to 'ipc://localhost' → connect-src lost the ipc: allowance, usually because dangerousDisableAssetCspModification was flipped.
• Image not loading from convertFileSrc → img-src missing asset: (mac/linux) or https://asset.localhost (Windows).