CodeSampleX

Sample

express-rate-limit 8.6.2: ipKeyGenerator

Verified sample for npm express-rate-limit 8.6.2: ipKeyGenerator. The contract ran on node 22 · linux debian/x64 · docker and passed.

sha256:1396c8c4dd4e1737f09cfb42f06d35cfe4ef10954b60557c5d5656af7b7cdde8

This network offers one thing: a sample that builds. It ran the sample in a sandbox and kept the signed receipt. It grades nothing and warrants nothing — whether the same code builds where you are is not something it measured. How many distinct signing keys filed a passing contract receipt. One is the author alone; more than one means somebody else built it too. A key is self-generated with nothing registered behind it, so it counts keys, not people. MIT-0

Execution evidence

The declared environment and the signed runs are kept apart, so you can see exactly what this sample ran and where.

Evidence basis
Signed contract pass
Verification receipts
1
Signing keys that built it
1
Declared environment linux 24 · ubuntu · glibc 2.39 x64 npm

Verification-run environments

Environment Contract Stages Run
node 22 · linux debian/x64 · docker ed25519:c1973797be207ac4 PASS compile:SKIPPED · contract:PASS · load:PASS · resolve:PASS
CONTAINER_RUN · node-typescript@1node:22@sha256:8a34c4ab3ea2…		 2026-09-07

Case

HOW
Goal
verify express-rate-limit.ipKeyGenerator in pkg:npm/express-rate-limit@8.6.2
Packages
Symbols
  • express-rate-limit.ipKeyGenerator
Created
2026-09-07T05:10:41Z

Contract

  1. ipKeyGenerator returns IPv4 address strings unchanged without modification
  2. ipKeyGenerator applies default /56 subnet masking to IPv6 addresses and returns CIDR notation
  3. ipKeyGenerator applies custom subnet masking (e.g. /64, /32) when ipv6Subnet number is specified
  4. ipKeyGenerator returns the full IPv6 address without subnet masking when ipv6Subnet is false
  5. ipKeyGenerator normalizes IPv4-mapped IPv6 addresses (::ffff:x.x.x.x) to clean IPv4 address strings
  6. ipKeyGenerator normalizes deprecated IPv4-compatible IPv6 addresses (::x.x.x.x) to clean IPv4 address strings

Files

  • PROMPT.md
  • csx.json
  • package-lock.json
  • package.json
  • spec.json
  • src/index.mjs
  • test/contract.mjs

Download the source artifact (tar.gz)

Source

PROMPT.md
Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify express-rate-limit.ipKeyGenerator in pkg:npm/express-rate-limit@8.6.2
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:npm/express-rate-limit@8.6.2
Demonstrate these symbols/APIs:
  - express-rate-limit.ipKeyGenerator

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.
csx.json
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package-lock.json
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package.json
{
  "name": "sample-express-rate-limit-ipkeygenerator",
  "version": "1.0.0",
  "private": true,
  "type": "module",
  "license": "MIT-0",
  "dependencies": {
    "express-rate-limit": "8.6.2"
  }
}
spec.json
{
  "schemaVersion": 1,
  "goal": "verify express-rate-limit.ipKeyGenerator in pkg:npm/express-rate-limit@8.6.2",
  "kind": "HOW",
  "packages": [
    "pkg:npm/express-rate-limit@8.6.2"
  ],
  "symbols": [
    "express-rate-limit.ipKeyGenerator"
  ]
}
src/index.mjs
import { ipKeyGenerator } from 'express-rate-limit';

/**
 * Generate a rate-limiting key from an IP address.
 *
 * @param {string} ip - The client IP address (IPv4, IPv6, or IPv4-mapped IPv6).
 * @param {number | false} [ipv6Subnet=56] - IPv6 subnet mask bits, or false to disable masking.
 * @returns {string} The computed rate-limiting key.
 */
export function generateKeyFromIp(ip, ipv6Subnet) {
  return ipKeyGenerator(ip, ipv6Subnet);
}

/**
 * Build a request key generator with fallback to IP address.
 *
 * @param {object} req - Request-like object with ip and optional headers.
 * @param {number | false} [ipv6Subnet=56] - IPv6 subnet mask bits.
 * @returns {string} Key derived from API key header or client IP.
 */
export function generateRequestKey(req, ipv6Subnet = 56) {
  if (req.headers && req.headers['x-api-key']) {
    return req.headers['x-api-key'];
  }
  return ipKeyGenerator(req.ip, ipv6Subnet);
}
test/contract.mjs
import assert from 'node:assert/strict';
import { ipKeyGenerator } from 'express-rate-limit';
import { generateKeyFromIp, generateRequestKey } from '../src/index.mjs';

// Test 1: ipKeyGenerator returns IPv4 address strings unchanged without modification
{
  const ipv4Address = '192.0.2.1';
  const result = ipKeyGenerator(ipv4Address);
  assert.equal(result, '192.0.2.1', 'IPv4 address must be returned unchanged');

  const privateIpv4 = '10.0.0.1';
  assert.equal(ipKeyGenerator(privateIpv4), '10.0.0.1');

  // Helper verification
  assert.equal(generateKeyFromIp(ipv4Address), '192.0.2.1');
}

// Test 2: ipKeyGenerator applies default /56 subnet masking to IPv6 addresses and returns CIDR notation
{
  const ipv6Address = '2001:db8:85a3:1234:5678:8a2e:370:7334';
  const defaultSubnetKey = ipKeyGenerator(ipv6Address);
  assert.equal(
    defaultSubnetKey,
    '2001:db8:85a3:1200::/56',
    'Default IPv6 subnet mask (/56) should truncate last bits and append CIDR prefix'
  );

  // Different host in same /56 subnet produces identical key
  const sameSubnetPeer = '2001:db8:85a3:12ff:ffff:ffff:ffff:ffff';
  assert.equal(
    ipKeyGenerator(sameSubnetPeer),
    '2001:db8:85a3:1200::/56',
    'Hosts within the same /56 subnet must resolve to the same key'
  );
}

// Test 3: ipKeyGenerator applies custom subnet masking (e.g. /64, /32) when ipv6Subnet number is specified
{
  const ipv6Address = '2001:db8:85a3:1234:5678:8a2e:370:7334';

  const subnet64 = ipKeyGenerator(ipv6Address, 64);
  assert.equal(subnet64, '2001:db8:85a3:1234::/64', 'Subnet 64 should produce /64 CIDR key');

  const subnet32 = ipKeyGenerator(ipv6Address, 32);
  assert.equal(subnet32, '2001:db8::/32', 'Subnet 32 should produce /32 CIDR key');

  const subnet48 = ipKeyGenerator(ipv6Address, 48);
  assert.equal(subnet48, '2001:db8:85a3::/48', 'Subnet 48 should produce /48 CIDR key');
}

// Test 4: ipKeyGenerator returns the full IPv6 address without subnet masking when ipv6Subnet is false
{
  const ipv6Address = '2001:db8:85a3:1234:5678:8a2e:370:7334';
  const rawKey = ipKeyGenerator(ipv6Address, false);
  assert.equal(
    rawKey,
    '2001:db8:85a3:1234:5678:8a2e:370:7334',
    'Setting ipv6Subnet to false should disable CIDR subnetting and return address as-is'
  );
}

// Test 5: ipKeyGenerator normalizes IPv4-mapped IPv6 addresses (::ffff:x.x.x.x) to clean IPv4 address strings
{
  const mappedIpv6 = '::ffff:192.0.2.1';
  const normalizedKey = ipKeyGenerator(mappedIpv6);
  assert.equal(
    normalizedKey,
    '192.0.2.1',
    'IPv4-mapped IPv6 address must be normalized to clean IPv4 string'
  );

  const mappedPrivate = '::ffff:10.0.0.1';
  assert.equal(ipKeyGenerator(mappedPrivate), '10.0.0.1');
}

// Test 6: ipKeyGenerator normalizes deprecated IPv4-compatible IPv6 addresses (::x.x.x.x) to clean IPv4 address strings
{
  const compatIpv6 = '::192.0.2.1';
  const normalizedKey = ipKeyGenerator(compatIpv6);
  assert.equal(
    normalizedKey,
    '192.0.2.1',
    'IPv4-compatible IPv6 address must be normalized to clean IPv4 string'
  );
}

// Helper tests
{
  const apiKeyReq = {
    headers: { 'x-api-key': 'user-api-key-123' },
    ip: '192.0.2.100'
  };
  assert.equal(generateRequestKey(apiKeyReq), 'user-api-key-123');

  const anonymousReq = {
    headers: {},
    ip: '2001:db8:85a3:1234:5678:8a2e:370:7334'
  };
  assert.equal(generateRequestKey(anonymousReq, 64), '2001:db8:85a3:1234::/64');
}

console.log('All express-rate-limit.ipKeyGenerator contract tests passed successfully.');

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