From 0e6d5dc3689f572e9b7d00a11b851d7afac727d3 Mon Sep 17 00:00:00 2001
From: Antoine Clausse <antoine.clausse@overleaf.com>
Date: Mon, 18 Aug 2025 13:23:13 +0200
Subject: [PATCH] Add utility for converting CIDR ranges to IP ranges (#26904)

* Add utility for converting CIDR ranges to IP ranges

* Add CLI support for IP matcher ranges script

GitOrigin-RevId: 1432bf3efa269c0e8e9d58fce1575bb01d694b2f
---
 services/web/scripts/ip_matcher_ranges.mjs    | 80 +++++++++++++++++++
 .../unit/src/Scripts/IpMatcherRange.test.mjs  | 19 +++++
 2 files changed, 99 insertions(+)
 create mode 100644 services/web/scripts/ip_matcher_ranges.mjs
 create mode 100644 services/web/test/unit/src/Scripts/IpMatcherRange.test.mjs

diff --git a/services/web/scripts/ip_matcher_ranges.mjs b/services/web/scripts/ip_matcher_ranges.mjs
new file mode 100644
index 0000000000..66a170761a
--- /dev/null
+++ b/services/web/scripts/ip_matcher_ranges.mjs
@@ -0,0 +1,80 @@
+#!/usr/bin/env node
+
+// @ts-check
+
+import minimist from 'minimist'
+import { fileURLToPath } from 'node:url'
+
+/**
+ * Converts an integer to its corresponding IPv4 address string representation
+ *
+ * @param {number} int
+ * @returns {string}
+ */
+const intToIp = int =>
+  [
+    (int >>> 24) & 0xff,
+    (int >>> 16) & 0xff,
+    (int >>> 8) & 0xff,
+    int & 0xff,
+  ].join('.')
+
+/**
+ * Convert CIDR to IP range
+ *
+ * @param {string} cidr
+ * @returns {{min: string, max: string}}
+ */
+const cidrToRange = cidr => {
+  const [ip, prefixLength] = cidr.split('/')
+  const prefix = parseInt(prefixLength)
+
+  // Convert IP to 32-bit integer
+  const ipParts = ip.split('.').map(part => parseInt(part))
+  const ipInt =
+    (ipParts[0] << 24) + (ipParts[1] << 16) + (ipParts[2] << 8) + ipParts[3]
+
+  // Calculate network mask
+  const mask = (0xffffffff << (32 - prefix)) >>> 0
+
+  // Calculate network and broadcast addresses
+  const network = (ipInt & mask) >>> 0
+  const broadcast = (network | (0xffffffff >>> prefix)) >>> 0
+
+  return {
+    min: intToIp(network),
+    max: intToIp(broadcast),
+  }
+}
+
+/**
+ * Converts an array of CIDR ranges into a single string representation.
+ * Each CIDR range is converted into its corresponding minimum and maximum IP range,
+ * formatted as "min..max". All resultant ranges are joined by a comma.
+ *
+ * @param {string[]} cidrRanges - An array of CIDR range strings to be converted.
+ * @returns {string} A string representation of the converted ranges where each
+ * range is formatted as "min..max" and joined by commas.
+ */
+export const convertCidrRanges = cidrRanges =>
+  cidrRanges
+    .map(cidr => {
+      const range = cidrToRange(cidr)
+      return `${range.min}..${range.max}`
+    })
+    .join(',')
+
+// Only run CLI if this file is executed directly
+if (fileURLToPath(import.meta.url) === process.argv[1]) {
+  const argv = minimist(process.argv.slice(2))
+
+  if (argv._.length === 0) {
+    console.log('Usage: node scripts/ip_matcher_ranges.mjs <cidr1> [cidr2] ...')
+    console.log(
+      'Example: node scripts/ip_matcher_ranges.mjs 192.168.1.0/24 10.0.0.0/8'
+    )
+    process.exit(1)
+  }
+
+  console.log(convertCidrRanges(argv._))
+}
diff --git a/services/web/test/unit/src/Scripts/IpMatcherRange.test.mjs b/services/web/test/unit/src/Scripts/IpMatcherRange.test.mjs
new file mode 100644
index 0000000000..91594e1bcc
--- /dev/null
+++ b/services/web/test/unit/src/Scripts/IpMatcherRange.test.mjs
@@ -0,0 +1,19 @@
+import { convertCidrRanges } from '../../../../scripts/ip_matcher_ranges.mjs'
+
+describe('IpMatcherRange', function () {
+  it('returns IP ranges from CIDR notation', function () {
+    const ranges = convertCidrRanges(['192.168.1.0/24'])
+    expect(ranges).to.deep.equal('192.168.1.0..192.168.1.255')
+  })
+
+  it('returns IP ranges from a variation CIDR notation', function () {
+    const ranges = convertCidrRanges([
+      '192.168.0.0/24',
+      '10.0.0.0/8',
+      '172.16.0.0/12',
+    ])
+    expect(ranges).to.deep.equal(
+      '192.168.0.0..192.168.0.255,10.0.0.0..10.255.255.255,172.16.0.0..172.31.255.255'
+    )
+  })
+})