proxy-from-env

What is proxy-from-env?

The proxy-from-env npm package is a utility for determining the proxy server to use for HTTP or HTTPS requests, based on environment variables. It interprets standard proxy environment variables like HTTP_PROXY, HTTPS_PROXY, and NO_PROXY, and provides a simple API to retrieve the correct proxy based on a given URL.

What are proxy-from-env's main functionalities?

Get proxy for URL

This feature allows you to determine the appropriate proxy for a given URL by considering the environment variables. The function `getProxyForUrl` returns the URL of the proxy server that should be used for the provided URL.

const getProxyForUrl = require('proxy-from-env').getProxyForUrl;
const url = 'http://example.com';
const proxy = getProxyForUrl(url);
console.log(proxy);

Other packages similar to proxy-from-env

global-agent

The global-agent package provides a global HTTP/HTTPS proxy agent that can be used to route HTTP/HTTPS requests through a specified proxy server. It is similar to proxy-from-env in that it respects standard proxy environment variables, but it also provides a bootstrap function to enable proxying globally in an application.

proxy-agent

Proxy-agent is a module that maps proxy configuration to various proxy agent implementations. It supports HTTP, HTTPS, SOCKS, and PAC file proxy configurations. Unlike proxy-from-env, which only determines the proxy URL, proxy-agent actually returns an agent that can be used directly with the HTTP/HTTPS request modules.

https-proxy-agent

The https-proxy-agent package provides an HTTP(s) proxy `Agent` implementation for HTTPS requests. It is designed to work with the built-in `https` module. This package is more focused on providing an agent for HTTPS proxying, whereas proxy-from-env is more about determining the proxy URL from the environment.

README

proxy-from-env

proxy-from-env is a Node.js package that exports a function (getProxyForUrl) that takes an input URL (a string) and returns the desired proxy URL (also a string) based on standard proxy environment variables. If no proxy is set, an empty string is returned.

It is your responsibility to actually proxy the request using the given URL.

Installation:

npm install proxy-from-env

Example

This example shows how the data for a URL can be fetched via the http module, in a proxy-aware way.

var http = require('http');
var parseUrl = require('url').parse;
var getProxyForUrl = require('proxy-from-env').getProxyForUrl;

var some_url = 'https://example.com/something';

var proxy_url = getProxyForUrl(some_url);  // <-- Our magic.
if (proxy_url) {
  // Should be proxied through proxy_url.
  var parsed_some_url = parseUrl(some_url);
  var parsed_proxy_url = parseUrl(proxy_url);
  // A HTTP proxy is quite simple. It is similar to a normal request, except the
  // path is an absolute URL, and the proxied URL's host is put in the header
  // instead of the server's actual host.
  httpOptions = {
    protocol: parsed_proxy_url.protocol,
    hostname: parsed_proxy_url.hostname,
    port: parsed_proxy_url.port,
    path: parsed_some_url.href,
    headers: {
      Host: parsed_some_url.host,  // = host name + optional port.
    },
  };
} else {
  // Direct request.
  httpOptions = some_url;
}
http.get(httpOptions, function(res) {
  var responses = [];
  res.on('data', function() { responses.push(chunk); });
  res.on('end', function() { console.log(responses.join(''));  });
});

Environment variables

The environment variables can be specified in lowercase or uppercase, with the lowercase name having precedence over the uppercase variant. A variable that is not set has the same meaning as a variable that is set but has no value.

NO_PROXY

NO_PROXY is a list of host names (optionally with a port). If the input URL matches any of the entries in NO_PROXY, then the input URL should be fetched by a direct request (i.e. without a proxy).

Matching follows the following rules:

• NO_PROXY=* disables all proxies.
• Space and commas may be used to separate the entries in the NO_PROXY list.
• If NO_PROXY does not contain any entries, then proxies are never disabled.
• If a port is added after the host name, then the ports must match. If the URL does not have an explicit port name, the protocol's default port is used.
• Generally, the proxy is only disabled if the host name is an exact match for an entry in the NO_PROXY list. The only exceptions are entries that start with a dot or with a wildcard; then the proxy is disabled if the host name ends with the entry.

See test.js for examples of what should match and what does not.

*_PROXY

The environment variable used for the proxy depends on the protocol of the URL. For example, https://example,com uses the "https" protocol, and therefore the proxy to be used is HTTPS_PROXY (NOT HTTP_PROXY, which is only used for http:-URLs).

The library is not limited to http(s), other schemes such as FTP_PROXY (ftp:), WSS_PROXY (wss:), WS_PROXY (ws:) are also supported.

If present, ALL_PROXY is used as fallback if there is no other match.

External resources

The exact way of parsing the environment variables is not codified in any standard. This library is designed to be compatible with formats as expected by existing software. The following resources were used to determine the desired behavior:

• cURL: https://curl.haxx.se/docs/manpage.html#ENVIRONMENT
  https://github.com/curl/curl/blob/4af40b3646d3b09f68e419f7ca866ff395d1f897/lib/url.c#L4446-L4514

• wget: https://www.gnu.org/software/wget/manual/wget.html#Proxies
  http://git.savannah.gnu.org/cgit/wget.git/tree/src/init.c?id=636a5f9a1c508aa39e35a3a8e9e54520a284d93d#n383
  http://git.savannah.gnu.org/cgit/wget.git/tree/src/retr.c?id=93c1517c4071c4288ba5a4b038e7634e4c6b5482#n1278

• W3: https://www.w3.org/Daemon/User/Proxies/ProxyClients.html

• Python's urllib: https://github.com/python/cpython/blob/936135bb97fe04223aa30ca6e98eac8f3ed6b349/Lib/urllib/request.py#L2444-L2479