request-filtering-agent

request-filtering-agent

An http(s).Agent implementation that block request Private IP address.

It help to prevent server-side request forgery (SSRF) attack.

• What is SSRF (Server-side request forgery)? Tutorial & Examples

Install

Install with npm:

npm install request-filtering-agent

Usage

useAgent(url) return an agent for the url. request-filtering-agent disallow to request to Private network.

const fetch = require("node-fetch");
const { useAgent } = require("request-filtering-agent");
const url = 'http://127.0.0.1:8080/';
fetch(url, {
    // use http or https agent for url
    agent: useAgent(url)
}).catch(err => {
    console.err(err); // DNS lookup 127.0.0.1(family:4, host:127.0.0.1.xip.io) is not allowed. Because, It is private IP address.
});

request-filtering-agent support loopback domain like xip.io and nip.io. This library detect the IP adpress that is dns lookup-ed.

$ dig 127.0.0.1.xip.io

;127.0.0.1.xip.io.		IN	A

;; ANSWER SECTION:
127.0.0.1.xip.io.	300	IN	A	127.0.0.1

Example code:

const fetch = require("node-fetch");
const { useAgent } = require("request-filtering-agent");
const url = 'http://127.0.0.1.xip.io:8080/';
fetch(url, {
    agent: useAgent(url)
}).catch(err => {
    console.err(err); // DNS lookup 127.0.0.1(family:4, host:127.0.0.1.xip.io) is not allowed. Because, It is private IP address.
});

It will prevent DNS rebinding

API

export interface RequestFilteringAgentOptions {
    // Allow to connect private IP address
    // Example, http://127.0.0.1/, http://localhost/
    // Default: false
    allowPrivateIPAddress?: boolean;
    // Allow to connect meta address 0.0.0.0
    // 0.0.0.0 (IPv4) and :: (IPv6) a meta address that routing another address
    // https://en.wikipedia.org/wiki/Reserved_IP_addresses
    // https://tools.ietf.org/html/rfc6890
    // Default: false
    allowMetaIPAddress?: boolean;
    // Allow address list
    // This values are preferred than denyAddressList
    // Default: []
    allowIPAddressList?: string[];
    // Deny address list
    // Default: []
    denyIPAddressList?: string[]
}
/**
 * Apply request filter to http(s).Agent instance
 */
export declare function applyRequestFilter<T extends http.Agent | http.Agent>(agent: T, options?: RequestFilteringAgentOptions): T;
/**
 * A subclsss of http.Agent with request filtering
 */
export declare class RequestFilteringHttpAgent extends http.Agent {
    constructor(options?: http.AgentOptions & RequestFilteringAgentOptions);
}
/**
 * A subclsss of https.Agent with request filtering
 */
export declare class RequestFilteringHttpsAgent extends https.Agent {
    constructor(options?: https.AgentOptions & RequestFilteringAgentOptions);
}
export declare const globalHttpAgent: RequestFilteringHttpAgent;
export declare const globalHttpsAgent: RequestFilteringHttpsAgent;
/**
 * get right an agent for the url
 * @param url
 */
export declare const useAgent: (url: string) => RequestFilteringHttpAgent | RequestFilteringHttpsAgent;

Example: Create an Agent with options

An agent that allow to request 127.0.0.1, but it dissllow other Private IP.

const fetch = require("node-fetch");
const { RequestFilteringHttpAgent } = require("request-filtering-agent");

// Create http agent that allow 127.0.0.1, but it disallow other private ip
const agent = new RequestFilteringHttpAgent({
    allowIPAddressList: ["127.0.0.1"], // it is preferred than allowPrivateIPAddress option
    allowPrivateIPAddress: false, // Default: false
});
// 127.0.0.1 is private ip address, but it is allowed
const url = 'http://127.0.0.1:8080/';
fetch(url, {
    agent: agent
}).then(res => {
    console.log(res); // OK
})

Example: Apply request filtering to exising http.Agent

You can apply request filtering to http.Agent or https.Agent using applyRequestFilter method.

const http = require("http")
const fetch = require("node-fetch");
const { applyRequestFilter } = require("request-filtering-agent");

// Create http agent with keepAlive option
const agent = new http.Agent({
    keepAlive: true,
});
// Apply request filtering to http.Agent
const agentWithFiltering = applyRequestFilter(agent, {
    allowPrivateIPAddress: false // Default: false
});
// 127.0.0.1 is private ip address
const url = 'http://127.0.0.1:8080/';
fetch(url, {
    agent: agentWithFiltering
}).catch(error => {
    console.error(error); // Dis-allowed
})

http.Agent libraries

http.Agent is supported by popular library.

• node-fetch
• Request
• node-http-proxy
• axios

request-filtering-agent work with these libraries.

Related

• welefen/ssrf-agent: make http(s) request to prevent SSRF
  • It provide only high level wrapper

Changelog

See Releases page.

Running tests

Install devDependencies and Run npm test:

npm test

Contributing

Pull requests and stars are always welcome.

For bugs and feature requests, please create an issue.

1. Fork it!
2. Create your feature branch: git checkout -b my-new-feature
3. Commit your changes: git commit -am 'Add some feature'
4. Push to the branch: git push origin my-new-feature
5. Submit a pull request :D

Author

• github/azu
• twitter/azu_re

License

MIT © azu