HTTP Auth with CORS

HTTP function that supports CORS requests with credentials.

Code sample

Go

To authenticate to Cloud Functions, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

// Package http provides a set of HTTP Cloud Functions samples.
package http

import (
	"fmt"
	"net/http"

	"github.com/GoogleCloudPlatform/functions-framework-go/functions"
)

// CORSEnabledFunctionAuth is an example of setting CORS headers with
// authentication enabled.
// For more information about CORS and CORS preflight requests, see
// https://developer.mozilla.org/en-US/docs/Glossary/Preflight_request.
func CORSEnabledFunctionAuth(w http.ResponseWriter, r *http.Request) {
	// Set CORS headers for the preflight request
	if r.Method == http.MethodOptions {
		w.Header().Set("Access-Control-Allow-Credentials", "true")
		w.Header().Set("Access-Control-Allow-Headers", "Authorization")
		w.Header().Set("Access-Control-Allow-Methods", "POST")
		w.Header().Set("Access-Control-Allow-Origin", "https://example.com")
		w.Header().Set("Access-Control-Max-Age", "3600")
		w.WriteHeader(http.StatusNoContent)
		return
	}
	// Set CORS headers for the main request.
	w.Header().Set("Access-Control-Allow-Credentials", "true")
	w.Header().Set("Access-Control-Allow-Origin", "https://example.com")
	fmt.Fprint(w, "Hello World!")
}

func init() {
	functions.HTTP("CORSEnabledFunctionAuth", CORSEnabledFunctionAuth)
}

Java

To authenticate to Cloud Functions, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

import com.google.cloud.functions.HttpFunction;
import com.google.cloud.functions.HttpRequest;
import com.google.cloud.functions.HttpResponse;
import java.io.BufferedWriter;
import java.io.IOException;
import java.net.HttpURLConnection;

public class CorsEnabledAuth implements HttpFunction {
  // corsEnabledAuth is an example of setting CORS headers.
  // For more information about CORS and CORS preflight requests, see
  // https://developer.mozilla.org/en-US/docs/Glossary/Preflight_request.
  @Override
  public void service(HttpRequest request, HttpResponse response)
      throws IOException {
    // Set CORS headers
    //   Allows GETs from origin https://mydomain.com
    //   with the Authorization header present
    response.appendHeader("Access-Control-Allow-Origin", "https://mydomain.com");
    response.appendHeader("Access-Control-Allow-Credentials", "true");

    if ("OPTIONS".equals(request.getMethod())) {
      response.appendHeader("Access-Control-Allow-Methods", "GET");
      response.appendHeader("Access-Control-Allow-Headers", "Authorization");
      response.appendHeader("Access-Control-Max-Age", "3600");
      response.setStatusCode(HttpURLConnection.HTTP_NO_CONTENT);
      return;
    }

    // Handle the main request
    BufferedWriter writer = response.getWriter();
    writer.write("CORS headers set successfully!");
  }
}

Node.js

To authenticate to Cloud Functions, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

const functions = require('@google-cloud/functions-framework');

/**
 * HTTP function that supports CORS requests with credentials.
 *
 * @param {Object} req Cloud Function request context.
 * @param {Object} res Cloud Function response context.
 */
functions.http('corsEnabledFunctionAuth', (req, res) => {
  // Set CORS headers for preflight requests
  // Allows GETs from origin https://mydomain.com with Authorization header

  res.set('Access-Control-Allow-Origin', 'https://mydomain.com');
  res.set('Access-Control-Allow-Credentials', 'true');

  if (req.method === 'OPTIONS') {
    // Send response to OPTIONS requests
    res.set('Access-Control-Allow-Methods', 'GET');
    res.set('Access-Control-Allow-Headers', 'Authorization');
    res.set('Access-Control-Max-Age', '3600');
    res.status(204).send('');
  } else {
    res.send('Hello World!');
  }
});

Python

To authenticate to Cloud Functions, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

import functions_framework

@functions_framework.http
def cors_enabled_function_auth(request):
    # For more information about CORS and CORS preflight requests, see
    # https://developer.mozilla.org/en-US/docs/Glossary/Preflight_request
    # for more information.

    # Set CORS headers for preflight requests
    if request.method == "OPTIONS":
        # Allows GET requests from origin https://mydomain.com with
        # Authorization header
        headers = {
            "Access-Control-Allow-Origin": "https://mydomain.com",
            "Access-Control-Allow-Methods": "GET",
            "Access-Control-Allow-Headers": "Authorization",
            "Access-Control-Max-Age": "3600",
            "Access-Control-Allow-Credentials": "true",
        }
        return ("", 204, headers)

    # Set CORS headers for main requests
    headers = {
        "Access-Control-Allow-Origin": "https://mydomain.com",
        "Access-Control-Allow-Credentials": "true",
    }

    return ("Hello World!", 200, headers)

Ruby

To authenticate to Cloud Functions, set up Application Default Credentials. For more information, see Set up authentication for a local development environment.

FunctionsFramework.http "cors_enabled_function_auth" do |request|
  # For more information about CORS and CORS preflight requests, see
  # https://developer.mozilla.org/en-US/docs/Glossary/Preflight_request
  # for more information.

  # Set CORS headers for preflight requests
  if request.options?
    # Allows GET requests from origin https://mydomain.com with
    # Authorization header
    headers = {
      "Access-Control-Allow-Origin"      => "https://mydomain.com",
      "Access-Control-Allow-Methods"     => "GET",
      "Access-Control-Allow-Headers"     => "Authorization",
      "Access-Control-Max-Age"           => "3600",
      "Access-Control-Allow-Credentials" => "true"
    }
    [204, headers, []]
  else
    # Set CORS headers for main requests
    headers = {
      "Access-Control-Allow-Origin"      => "https://mydomain.com",
      "Access-Control-Allow-Credentials" => "true"
    }

    [200, headers, ["Hello World!"]]
  end
end

What's next

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