Subresource Integrity & Supply Chain Hardening

Subresource Integrity (SRI) is a browser security mechanism that allows you to cryptographically verify that resources loaded from third-party sources — scripts, stylesheets, fonts — have not been tampered with. By embedding a base64-encoded cryptographic hash in your HTML, you guarantee that only the exact file you tested reaches your users.

Modern applications ingest hundreds of external packages per deployment. Every CDN-hosted library, every npm dependency, every third-party widget is a potential injection vector. Supply chain attacks bypass traditional perimeter defenses by exploiting implicit trust in upstream registries and delivery networks: a single compromised CDN or maintainer account can silently backdoor millions of sites.

This guide covers the full stack of supply chain hardening — from the cryptographic foundations of SHA-256 and SHA-384 hashing, through automated hash generation in Webpack and Vite pipelines, CDN trust mapping, dynamic script injection security, to dependency auditing with SBOMs, lockfile analysis, Sigstore provenance verification, and vulnerability triage. Whether you’re a frontend engineer integrating SRI for the first time, a security engineer defining policy, or a DevOps lead automating supply chain controls in CI/CD, you’ll find actionable guidance here.