How do I migrate to CSP without breaking my site?

Start with Content-Security-Policy-Report-Only (reports violations without enforcing). Use a report-uri or reporting-api to collect violations. Fix violations (move inline scripts to external files, add nonces/hashes). Once violations stop, switch to enforcing CSP. This gradual approach avoids breaking the site.

Nonce: random per-request value in header and script tag — allows any inline script with the nonce. Hash: SHA-256 of the script content in the header — allows only that exact script. Nonces are easier (one per page, not one per script) but require server-side generation. Hashes work for static pages but break when the script content changes (minification, deployment).

Implement Content Sécurité Policy (CSP)

CSP restricts quoi resources (scripts, styles, images) un page peut charger, preventing XSS et données injection. Apprendre policy directives et reporting.

1

CSP is an HTTP header (Content-Security-Policy) that whitelists resource sources. Directives: default-src (fallback), script-src (JavaScript), style-src (CSS), img-src, connect-src (fetch/XHR/WebSocket), font-src, frame-src, object-src. Use 'self' for same-origin, 'none' for nothing, nonces or hashes for inline scripts. CSP prevents XSS by blocking inline scripts and unauthorized sources.
2

Calculatrice de hash →
Générer a SHA-256 hash of inline script content for CSP hash-based allowlisting. The CSP directive: script-src 'sha256-<base64-hash>'. This allows only that specific inline script. Alternatively, use nonces: script-src 'nonce-<random>' and add nonce="<random>" to each script tag. Nonces are preferred (hashes break on minification).
3

Générateur HMAC →
Générer a CSP nonce (number used once) for each page load. The nonce is a random base64 string included in the CSP header and each script tag. This allows inline scripts with the correct nonce while blocking unauthorized ones. Generate a fresh nonce per request — never reuse or hardcode it.

Questions fréquentes

How do I migrate to CSP without breaking my site?: Start with Content-Security-Policy-Report-Only (reports violations without enforcing). Use a report-uri or reporting-api to collect violations. Fix violations (move inline scripts to external files, add nonces/hashes). Once violations stop, switch to enforcing CSP. This gradual approach avoids breaking the site.
CSP nonce vs hash?: Nonce: random per-request value in header and script tag — allows any inline script with the nonce. Hash: SHA-256 of the script content in the header — allows only that exact script. Nonces are easier (one per page, not one per script) but require server-side generation. Hashes work for static pages but break when the script content changes (minification, deployment).