Crypto Middleware

@sebastienrousseau/crypto-middleware

Framework-agnostic cryptographic middleware for Express, Fastify, and Koa applications.

Getting started

Install — installation via pnpm, npm, or yarn
Requirements — runtime floor and environment prerequisites
Quick Start — minimal working usage sample

The Crypto Service ecosystem

The Crypto Service ecosystem — full 14-package suite overview

Package reference

Reference & Usage — features, configuration, and capabilities
Examples — runnable sample code

Operational

Development — build, lint, format, and test targets
Security — vulnerability disclosure and cryptographic invariants
Documentation — TypeDoc API docs and ecosystem guides
Stability guarantees — SemVer axis and release policy
License

Install

pnpm add @sebastienrousseau/crypto-middleware
# or
npm install @sebastienrousseau/crypto-middleware
# or
yarn add @sebastienrousseau/crypto-middleware

Requirements

Node.js: ^22.0.0 or >=24.0.0 (active and maintenance LTS releases)
Package Manager: pnpm >=9 (recommended) or npm >=10
TypeScript: >=5.0 (when compiling with TypeScript)

Quick Start

import express from "express";
import { createCryptoMiddleware } from "@sebastienrousseau/crypto-middleware";

const app = express();
app.use(express.json());

app.use(
  createCryptoMiddleware({
    key: process.env.CRYPTO_KEY, // 256-bit hex key
    operations: ["decrypt-request", "encrypt-response"],
  }),
);

app.post("/api/data", (req, res) => {
  // req.body is already decrypted
  res.json({ received: req.body });
  // response is automatically encrypted
});

app.listen(3000);

The Crypto Service ecosystem

Crypto Service provides a complete cryptography stack across 14 specialized packages:

Package	Role	Description
`@sebastienrousseau/crypto-api`	API Schemas	Shared TypeScript types and utilities for the Crypto Service Suite, defining the canonical API surface.
`@sebastienrousseau/crypto-cli`	Terminal CLI	An interactive command-line interface for cryptographic operations, supporting both legacy OpenPGP and modern post-quantum algorithms.
`@sebastienrousseau/crypto-edge`	Edge Runtime	Edge-runtime cryptographic operations using the Web Crypto API, optimized for Cloudflare Workers, Vercel Edge, and Deno.
`@sebastienrousseau/crypto-kms`	Cloud KMS	Unified Key Management Service interface for AWS KMS, GCP Cloud KMS, Azure Key Vault, and HashiCorp Vault.
`@sebastienrousseau/crypto-lib`	Core Library	A modern cryptographic library for TypeScript, with post-quantum support, zero unsafe dependencies, and 100% test coverage.
`@sebastienrousseau/crypto-middleware` (this package)	Middleware	Framework-agnostic cryptographic middleware for Express, Fastify, and Koa applications.
`@sebastienrousseau/crypto-prisma`	ORM Adapter	Transparent field-level encryption extension for Prisma Client, powered by AES-256-GCM.
`@sebastienrousseau/crypto-react`	React Hooks	React hooks and context provider for client-side cryptographic operations with zero boilerplate.
`@sebastienrousseau/crypto-sdk`	Client SDK	A zero-dependency, typed HTTP client for the Crypto Service REST API, with full post-quantum support.
`@sebastienrousseau/crypto-server`	HTTP API	A hardened Fastify REST API for cryptographic operations, with rate limiting, OpenAPI schemas, and post-quantum endpoints.
`@sebastienrousseau/crypto-testing`	Test Support	Deterministic keys, fast mocks, and test fixtures for crypto-lib
`@sebastienrousseau/crypto-typeorm`	ORM Adapter	TypeORM column-level encryption with a single decorator, powered by crypto-lib.
`@sebastienrousseau/crypto-vue`	Vue Composables	Vue 3 composables for client-side cryptography
`@sebastienrousseau/crypto-wasm`	Acceleration	WebAssembly performance accelerator for crypto-lib

Overview

crypto-middleware provides transparent cryptographic operations for Express and Fastify applications. It can auto-decrypt incoming request bodies, encrypt outgoing responses, verify HMAC signatures on webhooks, and validate HS256 JWT bearer tokens -- all via a single middleware registration. Route matching via glob patterns lets you scope protection to specific endpoints.

## Express

Configuration

Option	Type	Required	Description
`key`	`string`	*	Hex-encoded 256-bit key for encryption/decryption
`routes`	`string[]`	No	Glob patterns for routes to apply middleware to
`operations`	`string[]`	No	Operations to perform (see below)
`hmacKey`	`string`	*	Hex-encoded HMAC key for signature verification
`jwtSecret`	`string`	*	Secret for HS256 JWT verification

* Required when the corresponding operation is enabled.

Operations

Operation	Description
`decrypt-request`	Decrypts incoming JSON bodies
`encrypt-response`	Encrypts outgoing JSON responses
`verify-signature`	Verifies HMAC-SHA256 from `x-signature` header
`verify-jwt`	Verifies HS256 JWT from `Authorization: Bearer` header

Route Matching

Pattern	Matches
`/api/data`	Exact match only
`/api/*`	One path segment: `/api/users`, `/api/1`
`/api/**`	Any depth: `/api/users/1/profile`

When routes is omitted or empty, middleware applies to all routes.

## Fastify

import Fastify from "fastify";
import { cryptoPlugin } from "@sebastienrousseau/crypto-middleware";

const app = Fastify();

app.register(cryptoPlugin, {
  key: process.env.CRYPTO_KEY,
  operations: ["decrypt-request", "encrypt-response"],
});

app.post("/api/data", async (request) => {
  return { received: request.body };
});

app.listen({ port: 3000 });

The cryptoPlugin accepts the same configuration options as createCryptoMiddleware.

## Examples

All examples are self-contained TypeScript files in the examples/ directory. Run any example with:

npx ts-node examples/<name>.ts

Category	Example	Purpose
Express	express.ts	Full Express setup with encrypt/decrypt
Fastify	fastify.ts	Fastify plugin registration
Webhook	webhook.ts	HMAC signature verification for webhooks
JWT	jwt.ts	JWT Bearer token verification
Encrypted	encrypted.ts	Full encrypted request/response pipeline

Development

pnpm --filter @sebastienrousseau/crypto-middleware run build
pnpm --filter @sebastienrousseau/crypto-middleware run test
pnpm --filter @sebastienrousseau/crypto-middleware run lint
pnpm --filter @sebastienrousseau/crypto-middleware run format

All 14 packages in the Crypto Service workspace maintain a 100% coverage floor across statements, branches, functions, and lines.

Security

Report vulnerabilities privately via GitHub Security Advisories or according to SECURITY.md. Never report security issues publicly.

All cryptographic operations leverage audited primitives, enforce constant-time execution where applicable, and zero sensitive key material upon disposal.

Documentation

Stability guarantees

Versions advance strictly one step at a time on the 0.0.x line (v0.0.1 → v0.0.2 → v0.0.3 ... → v0.0.999 → v0.1.0). Work for every release iteration begins on a dedicated feat/v<version> branch.

All 14 packages in the workspace move in lockstep. Public API signatures, cipher output formats, and serialization schemas are strictly versioned. Breaking changes to serialized formats or algorithm defaults are considered major breaking changes. Minimum toolchain upgrades (e.g. Node.js LTS floor) are governed by POLICIES.md.

License

Dual-licensed under Apache 2.0 or MIT, at your option.