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Strengthen CSP by removing unsafe-inline and unsafe-eval from script-src #393

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48c0fb1
Remove unsafe-inline and unsafe-eval from parent page script-src CSP
claude Mar 14, 2026
7d74278
Move remaining inline scripts and event handlers to external files
claude Mar 15, 2026
0d4849a
Fix CSP violation from SES inline-text injection into same-origin iframe
claude Mar 15, 2026
5bffd2c
Pre-initialize manifold-3d to bypass InitializeCSG2Async inline script
claude Mar 15, 2026
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14 changes: 10 additions & 4 deletions docs/CSP_POLICY.md
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Original file line number Diff line number Diff line change
Expand Up @@ -35,7 +35,7 @@ default-src 'self';
base-uri 'self';
form-action 'self';
object-src 'none';
script-src 'self' 'unsafe-inline' 'unsafe-eval' 'wasm-unsafe-eval' https://www.googletagmanager.com https://unpkg.com;
script-src 'self' 'wasm-unsafe-eval' https://www.googletagmanager.com https://unpkg.com;
style-src 'self' 'unsafe-inline';
img-src 'self' data: blob: https://www.google-analytics.com https://www.googletagmanager.com;
font-src 'self' data:;
Expand All @@ -53,10 +53,16 @@ Meta fallback policy (for static hosting without headers): same as above but wit

The policy uses strict defaults (`default-src 'self'`, `object-src 'none'`, explicit `connect-src`/`script-src`/`worker-src`) while preserving required runtime behavior.

Two allowances remain intentionally broad enough for current implementation:
One allowance remains intentionally broad:

- `'unsafe-inline'` in `script-src` / `style-src` due to inline scripts/styles in `index.html` and iframe sandbox bootstrap.
- `'unsafe-eval'` + `'wasm-unsafe-eval'` in `script-src` to support current sandbox/runtime execution stack.
- `'unsafe-inline'` in `style-src` — required for Blockly's runtime-injected inline styles (block colours, toolbox layout). Dynamically injected styles cannot be hashed, so this cannot be removed without modifying Blockly's theming internals.

`script-src` no longer requires `'unsafe-inline'` or `'unsafe-eval'`:

- The Google Analytics initialisation script was moved from an inline `<script>` block to `ga-init.js` (served from `self`), eliminating the only inline script in `index.html`.
- The `new Function(code)` syntax-check in `validateCode()` was removed; the AST-based `validateUserCodeAST()` already provides a stricter check before code reaches the sandbox.
- WASM execution (Draco, Manifold) is covered by `'wasm-unsafe-eval'`, which allows only WASM compilation rather than arbitrary JS `eval`.
- The sandbox iframe sets its own CSP (`script-src 'unsafe-inline' 'unsafe-eval'`) inside the iframe document — this is separate from the parent page's policy and governs only sandboxed user-code execution.

## CSP regression checks before merge

Expand Down
51 changes: 30 additions & 21 deletions flock.js
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@
// Flip Computing Limited - flipcomputing.com

import * as acorn from "acorn";
import ManifoldInit from "manifold-3d";
import * as walk from "acorn-walk";
import HavokPhysics from "@babylonjs/havok";
import * as BABYLON from "@babylonjs/core";
Expand Down Expand Up @@ -386,13 +387,6 @@ export const flock = {
throw new Error("Code too long (max 100KB)");
}

// Basic syntax check
try {
new Function(code); // Just check if it parses
} catch (e) {
throw new Error(`Syntax error: ${e.message}`);
}

// Optional: Warn about patterns (don't block)
const warnings = [];
if (/eval\s*\(/.test(code)) {
Expand Down Expand Up @@ -670,19 +664,24 @@ export const flock = {
sameOrigin: true,
});

// --- load SES text in parent and inject inline into iframe (CSP allows inline) ---
const sesResp = await fetch(
"vendor/ses/lockdown.umd.min.js",
);
if (!sesResp.ok)
throw new Error(
`Failed to fetch SES: ${sesResp.status}`,
);
const sesText = await sesResp.text();
const sesScript = doc.createElement("script");
sesScript.type = "text/javascript";
sesScript.text = sesText;
doc.head.appendChild(sesScript);
// Load SES lockdown via src= so the parent's script-src 'self' policy
// is satisfied — injecting inline text would require 'unsafe-inline'.
await new Promise((resolve, reject) => {
const sesScript = doc.createElement("script");
sesScript.type = "text/javascript";
sesScript.onload = resolve;
sesScript.onerror = () =>
reject(
new Error(
"Failed to load SES lockdown",
),
);
sesScript.src = new URL(
"vendor/ses/lockdown.umd.min.js",
document.baseURI,
).href;
doc.head.appendChild(sesScript);
});
Comment on lines +667 to +684
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⚠️ Potential issue | 🔴 Critical

🧩 Analysis chain

🏁 Script executed:

#!/bin/bash
# Verify iframe CSP and SES external loading code paths
rg -n -C2 "const csp =|script-src|sesScript\\.src|lockdown\\.umd\\.min\\.js" flock.js

Repository: flipcomputing/flock

Length of output: 1005

🏁 Script executed:

#!/bin/bash
# Check CSP application context and SES script location
echo "=== Checking CSP context (around line 1176) ==="
sed -n '1170,1185p' flock.js

echo -e "\n=== Checking if vendor/ses/lockdown.umd.min.js exists ==="
find . -name "lockdown.umd.min.js" 2>/dev/null || echo "File not found in current search"

echo -e "\n=== Checking SES loading code context (around line 666) ==="
sed -n '660,690p' flock.js

Repository: flipcomputing/flock

Length of output: 2720

🏁 Script executed:

#!/bin/bash
# Check vendor directory and SES files
echo "=== Checking for vendor directory ==="
ls -la vendor/ 2>/dev/null || echo "vendor/ directory does not exist"

echo -e "\n=== Searching for any SES-related files ==="
find . -iname "*ses*" -o -iname "*lockdown*" 2>/dev/null | head -20

echo -e "\n=== Checking package.json for SES dependency ==="
grep -i "ses" package.json 2>/dev/null || echo "No SES mention in package.json"

echo -e "\n=== Checking if this code path is executed/tested ==="
rg -n "replaceSandboxIframe\|lockdown\(\)" flock.js | head -10

Repository: flipcomputing/flock

Length of output: 316

🏁 Script executed:

#!/bin/bash
# Check where replaceSandboxIframe is defined and called
echo "=== Finding replaceSandboxIframe definition ==="
rg -n "replaceSandboxIframe\s*[=:(]" flock.js | head -5

echo -e "\n=== Checking SES npm package installation ==="
ls -la node_modules/ses 2>/dev/null | head -5 || echo "SES not in node_modules"

echo -e "\n=== Checking actual SES file locations ==="
find node_modules/ses -name "lockdown*" 2>/dev/null | head -10

echo -e "\n=== Checking if vendor is built/created elsewhere ==="
rg -n "vendor.*ses\|lockdown.*umd" --type js | head -10

Repository: flipcomputing/flock

Length of output: 382

CSP blocks the SES script load — add 'self' to script-src.

The iframe CSP at line 1176 is script-src 'unsafe-inline' 'unsafe-eval', which blocks external scripts. Line 666-683 loads SES via sesScript.src, requiring the 'self' directive to allow same-origin external scripts. The promise will reject with a CSP violation.

Add 'self' to the script-src policy:

Minimal fix 
-const csp = `default-src 'none'; style-src 'unsafe-inline'; script-src 'unsafe-inline' 'unsafe-eval'`;
+const csp = `default-src 'none'; style-src 'unsafe-inline'; script-src 'self' 'unsafe-inline' 'unsafe-eval'`;

Note: Verify the SES file path vendor/ses/lockdown.umd.min.js exists in your build output, as the vendor directory is not in the source repo. The SES package is listed as a dependency ("ses": "^1.14.0").

🤖 Prompt for AI Agents 
Verify each finding against the current code and only fix it if needed.

In `@flock.js` around lines 666 - 683, The iframe Content-Security-Policy used
when creating the iframe must include 'self' in its script-src so the
externally-loaded SES script (sesScript.src -> "vendor/ses/lockdown.umd.min.js"
resolved via document.baseURI) is allowed; update the CSP string/attribute that
sets script-src (where you currently have "script-src 'unsafe-inline'
'unsafe-eval'") to include 'self' (e.g., "script-src 'self' 'unsafe-inline'
'unsafe-eval'"), and verify the vendor/ses/lockdown.umd.min.js file is present
in the build output so the dynamic load via doc.createElement("script")
succeeds.


// lockdown the iframe realm
win.lockdown();
Expand Down Expand Up @@ -1258,7 +1257,17 @@ export const flock = {
flock.abortController = new AbortController();

try {
await flock.BABYLON.InitializeCSG2Async();
// Pre-initialize manifold-3d here so we can pass the instances
// directly to InitializeCSG2Async, bypassing its _LoadScriptModuleAsync
// path which injects an inline <script type="module"> — blocked by CSP.
const manifoldWasm = await ManifoldInit({
locateFile: (f) => "./wasm/" + f,
});
manifoldWasm.setup();
await flock.BABYLON.InitializeCSG2Async({
manifoldInstance: manifoldWasm.Manifold,
manifoldMeshInstance: manifoldWasm.Mesh,
});
} catch (error) {
console.error("Error initializing CSG2:", error);
}
Expand Down
7 changes: 7 additions & 0 deletions ga-init.js
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Original file line number Diff line number Diff line change
@@ -0,0 +1,7 @@
window.dataLayer = window.dataLayer || [];
function gtag() { dataLayer.push(arguments); }
gtag('js', new Date());
gtag('config', 'G-QCGT3X072N', {
client_storage: 'none', // Prevents setting cookies
anonymize_ip: true // Hides IP addresses for privacy
});
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