Content Security Policy (CSP) Builder
Content Security Policy (CSP) Builder: Compiles W3C CSP Level 3 directives into a semicolon-delimited header string.
About this content security policy (csp) builder
Content Security Policy (CSP) Builder — browser-based utility.
How this tool works
Implements client-side Content Security Policy (CSP) Builder operations. Compiles W3C CSP Level 3 directives into a semicolon-delimited header string specifically designed for a security engineer crafts a strict content security policy (csp) header to mitigate xss vulnerabilities.
- Credential & Payload Ingestion: Accepts raw request body strings, timestamp headers, and shared signing secrets.
- Canonical String Construction: Assembles the canonical signing payload (e.g. timestamp + '.' + body for Stripe signatures).
- Cryptographic Hash Evaluation: Uses Web Crypto subtle.sign with HMAC-SHA256 to compute the reference digest.
- Constant-Time Verification: Compares computed signature against received header using constant-time byte iteration.
Worked example
Scenario: A security engineer crafts a strict Content Security Policy (CSP) header to mitigate XSS vulnerabilities.
Sample input:
Processing: Compiles W3C CSP Level 3 directives into a semicolon-delimited header string.
Illustrative output:
Limits and verification
Requires exact raw byte representations of JSON bodies; any whitespace formatting change invalidates cryptographic HMAC signatures. Flags timestamp drift exceeding 5 minutes (300 seconds) to prevent replay attacks.
Examples demonstrate an expected workflow; they do not prove every input or every branch of an external specification. Check important results with an independent source before using them for money, security, compliance, safety, or irreversible file changes.
Browser processing boundary
Tool input is processed by code running in the browser and is not intentionally sent to a CZOA processing API. The page can still request ordinary site assets, analytics, or advertising when those services are enabled. Browser extensions and managed-device software remain outside this tool's control.
Relevant references
These references govern or help explain the format, protocol, or calculation used here. Listing a reference does not claim certification or complete implementation of every optional feature.
Content owner: CZOA Tools · Last reviewed: 2026-09-15 · Review methodology
How to use it
- Enter, paste, or select your input data into the Content Security Policy (CSP) Builder workspace controls.
- Review available parameter fields, units, formats, or options configured for your task.
- Click the action button or observe immediate live calculations rendered in your browser runtime.
- Inspect the resulting output and any diagnostic messages, then copy or download the result if needed.
Frequently asked questions
How does CSP Builder format directives?+
It parses a directives object, converts each value to an array if needed, joins its sources with spaces, then joins directive lines with semicolons. Missing input uses three local defaults.
What did the CSP fixture verify?+
default-src self, img-src https and data, and object-src none produced the exact semicolon-separated directive text in insertion order.
Which CSP validation is absent?+
It does not parse source-expression grammar, test browser support, inspect inline scripts, nonces, hashes, report endpoints, inherited policies, conflicting headers or deployed content.
Does a CSP string protect a page?+
No. It must be delivered as a correctly configured response header or policy and tested with the real application resources and browser behavior.