express-ip-filter-middleware

Express middleware for access control using IP / CIDR lists.

Installation

npm install express-ip-filter-middleware 

Usage

import { BlockList } from 'node:net';
import express from 'express';
import { ipFilterMiddleware } from 'express-ip-filter-middleware';

const allow = new BlockList();
allow.addSubnet('192.168.0.0', 16);

const deny = new BlockList();
deny.addAddress('192.168.0.1');

const options = {
    mode: 'whitelist',
    allow,
    deny,
};

const app = express();
app.use(ipFilterMiddleware(options))

express-ip-filter-middleware generates a middleware that allows or blocks access per the specified options.

Options is an object with the following fields:

• mode: 'whitelist' | 'blacklist' (required): operation mode. In blacklist mode, everything is allowed except for the explicitly blacklisted items (specified in deny), unless overridden by allow. In whitelist mode, everything is forbidden except for explicitly allowed items (specified in allow), unless overridden by deny;
• allow: net.BlockList: optional list of the allowed addresses;
• deny: net.BlockList: optional list of the denied addresses;
• ipOverride: (req: express.Request) => string | undefined: optional function to retrieve the IP address to check. If this function is not specified, req.ip is used. If this function returns an invalid IP address, the middleware bails out with an error.

The mode of operation is similar to Apache's mod_access Order directive: whitelist works like Order Allow,Deny: to allow access, the IP address must match the allow list, and must not be listed in the deny list. Consequently, empty allow and deny in allow mode will result in denied access.

blacklist mode works like Order Deny,Allow: the request is allowed if the IP address is listed in the allow list or not listed in the deny list.