Configuring cross-origin resource sharing (CORS) - Amazon Simple Storage Service

Configuring cross-origin resource sharing (CORS)

Cross-origin resource sharing (CORS) defines a way for client web applications that are loaded in one domain to interact with resources in a different domain. With CORS support, you can build rich client-side web applications with Amazon S3 and selectively allow cross-origin access to your Amazon S3 resources.

This section shows you how to enable CORS using the Amazon S3 console, the Amazon S3 REST API, and the AWS SDKs. To configure your bucket to allow cross-origin requests, you add a CORS configuration to the bucket. A CORS configuration is a document that defines rules that identify the origins that you will allow to access your bucket, the operations (HTTP methods) supported for each origin, and other operation-specific information. In the S3 console, the CORS configuration must be a JSON document.

For example CORS configurations in JSON and XML, see Elements of a CORS configuration.

This section explains how to use the Amazon S3 console to add a cross-origin resource sharing (CORS) configuration to an S3 bucket.

When you enable CORS on the bucket, the access control lists (ACLs) and other access permission policies continue to apply.

Important

In the S3 console, the CORS configuration must be JSON. For examples CORS configurations in JSON and XML, see Elements of a CORS configuration.

To add a CORS configuration to an S3 bucket

  1. Sign in to the AWS Management Console and open the Amazon S3 console at https://console.aws.amazon.com/s3/.

  2. In the Buckets list, choose the name of the bucket that you want to create a bucket policy for.

  3. Choose Permissions.

  4. In the Cross-origin resource sharing (CORS) section, choose Edit.

  5. In the CORS configuration editor text box, type or copy and paste a new CORS configuration, or edit an existing configuration.

    The CORS configuration is a JSON file. The text that you type in the editor must be valid JSON. For more information, see Elements of a CORS configuration.

  6. Choose Save changes.

    Note

    Amazon S3 displays the Amazon Resource Name (ARN) for the bucket next to the CORS configuration editor title. For more information about ARNs, see Amazon Resource Names (ARNs) and AWS Service Namespaces in the Amazon Web Services General Reference.

You can use the AWS SDK to manage cross-origin resource sharing (CORS) for a bucket. For more information about CORS, see Using cross-origin resource sharing (CORS).

The following examples:

  • Creates a CORS configuration and sets the configuration on a bucket

  • Retrieves the configuration and modifies it by adding a rule

  • Adds the modified configuration to the bucket

  • Deletes the configuration

Java

For instructions on how to create and test a working sample, see Getting Started in the AWS SDK for Java Developer Guide.


import com.amazonaws.AmazonServiceException;
import com.amazonaws.SdkClientException;
import com.amazonaws.auth.profile.ProfileCredentialsProvider;
import com.amazonaws.regions.Regions;
import com.amazonaws.services.s3.AmazonS3;
import com.amazonaws.services.s3.AmazonS3ClientBuilder;
import com.amazonaws.services.s3.model.BucketCrossOriginConfiguration;
import com.amazonaws.services.s3.model.CORSRule;

import java.io.IOException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

public class CORS {

    public static void main(String[] args) throws IOException {
        Regions clientRegion = Regions.DEFAULT_REGION;
        String bucketName = "*** Bucket name ***";

        // Create two CORS rules.
        List<CORSRule.AllowedMethods> rule1AM = new ArrayList<CORSRule.AllowedMethods>();
        rule1AM.add(CORSRule.AllowedMethods.PUT);
        rule1AM.add(CORSRule.AllowedMethods.POST);
        rule1AM.add(CORSRule.AllowedMethods.DELETE);
        CORSRule rule1 = new CORSRule().withId("CORSRule1").withAllowedMethods(rule1AM)
                .withAllowedOrigins(Arrays.asList("http://*.example.com"));

        List<CORSRule.AllowedMethods> rule2AM = new ArrayList<CORSRule.AllowedMethods>();
        rule2AM.add(CORSRule.AllowedMethods.GET);
        CORSRule rule2 = new CORSRule().withId("CORSRule2").withAllowedMethods(rule2AM)
                .withAllowedOrigins(Arrays.asList("*")).withMaxAgeSeconds(3000)
                .withExposedHeaders(Arrays.asList("x-amz-server-side-encryption"));

        List<CORSRule> rules = new ArrayList<CORSRule>();
        rules.add(rule1);
        rules.add(rule2);

        // Add the rules to a new CORS configuration.
        BucketCrossOriginConfiguration configuration = new BucketCrossOriginConfiguration();
        configuration.setRules(rules);

        try {
            AmazonS3 s3Client = AmazonS3ClientBuilder.standard()
                    .withCredentials(new ProfileCredentialsProvider())
                    .withRegion(clientRegion)
                    .build();

            // Add the configuration to the bucket.
            s3Client.setBucketCrossOriginConfiguration(bucketName, configuration);

            // Retrieve and display the configuration.
            configuration = s3Client.getBucketCrossOriginConfiguration(bucketName);
            printCORSConfiguration(configuration);

            // Add another new rule.
            List<CORSRule.AllowedMethods> rule3AM = new ArrayList<CORSRule.AllowedMethods>();
            rule3AM.add(CORSRule.AllowedMethods.HEAD);
            CORSRule rule3 = new CORSRule().withId("CORSRule3").withAllowedMethods(rule3AM)
                    .withAllowedOrigins(Arrays.asList("http://www.example.com"));

            rules = configuration.getRules();
            rules.add(rule3);
            configuration.setRules(rules);
            s3Client.setBucketCrossOriginConfiguration(bucketName, configuration);

            // Verify that the new rule was added by checking the number of rules in the
            // configuration.
            configuration = s3Client.getBucketCrossOriginConfiguration(bucketName);
            System.out.println("Expected # of rules = 3, found " + configuration.getRules().size());

            // Delete the configuration.
            s3Client.deleteBucketCrossOriginConfiguration(bucketName);
            System.out.println("Removed CORS configuration.");

            // Retrieve and display the configuration to verify that it was
            // successfully deleted.
            configuration = s3Client.getBucketCrossOriginConfiguration(bucketName);
            printCORSConfiguration(configuration);
        } catch (AmazonServiceException e) {
            // The call was transmitted successfully, but Amazon S3 couldn't process
            // it, so it returned an error response.
            e.printStackTrace();
        } catch (SdkClientException e) {
            // Amazon S3 couldn't be contacted for a response, or the client
            // couldn't parse the response from Amazon S3.
            e.printStackTrace();
        }
    }

    private static void printCORSConfiguration(BucketCrossOriginConfiguration configuration) {
        if (configuration == null) {
            System.out.println("Configuration is null.");
        } else {
            System.out.println("Configuration has " + configuration.getRules().size() + " rules\n");

            for (CORSRule rule : configuration.getRules()) {
                System.out.println("Rule ID: " + rule.getId());
                System.out.println("MaxAgeSeconds: " + rule.getMaxAgeSeconds());
                System.out.println("AllowedMethod: " + rule.getAllowedMethods());
                System.out.println("AllowedOrigins: " + rule.getAllowedOrigins());
                System.out.println("AllowedHeaders: " + rule.getAllowedHeaders());
                System.out.println("ExposeHeader: " + rule.getExposedHeaders());
                System.out.println();
            }
        }
    }
}
.NET

For information about setting up and running the code examples, see Getting Started with the AWS SDK for .NET in the AWS SDK for .NET Developer Guide. 

using Amazon;
using Amazon.S3;
using Amazon.S3.Model;
using System;
using System.Collections.Generic;
using System.Threading.Tasks;

namespace Amazon.DocSamples.S3
{
    class CORSTest
    {
        private const string bucketName = "*** bucket name ***";
        // Specify your bucket region (an example region is shown).
        private static readonly RegionEndpoint bucketRegion = RegionEndpoint.USWest2; 
        private static IAmazonS3 s3Client;

        public static void Main()
        {
            s3Client = new AmazonS3Client(bucketRegion);
            CORSConfigTestAsync().Wait();
        }
        private static async Task CORSConfigTestAsync()
        {
            try
            {
                // Create a new configuration request and add two rules    
                CORSConfiguration configuration = new CORSConfiguration
                {
                    Rules = new System.Collections.Generic.List<CORSRule>
                        {
                          new CORSRule
                          {
                            Id = "CORSRule1",
                            AllowedMethods = new List<string> {"PUT", "POST", "DELETE"},
                            AllowedOrigins = new List<string> {"http://*.example.com"}
                          },
                          new CORSRule
                          {
                            Id = "CORSRule2",
                            AllowedMethods = new List<string> {"GET"},
                            AllowedOrigins = new List<string> {"*"},
                            MaxAgeSeconds = 3000,
                            ExposeHeaders = new List<string> {"x-amz-server-side-encryption"}
                          }
                        }
                };

                // Add the configuration to the bucket. 
                await PutCORSConfigurationAsync(configuration);

                // Retrieve an existing configuration. 
                configuration = await RetrieveCORSConfigurationAsync();

                // Add a new rule.
                configuration.Rules.Add(new CORSRule
                {
                    Id = "CORSRule3",
                    AllowedMethods = new List<string> { "HEAD" },
                    AllowedOrigins = new List<string> { "http://www.example.com" }
                });

                // Add the configuration to the bucket. 
                await PutCORSConfigurationAsync(configuration);

                // Verify that there are now three rules.
                configuration = await RetrieveCORSConfigurationAsync();
                Console.WriteLine();
                Console.WriteLine("Expected # of rulest=3; found:{0}", configuration.Rules.Count);
                Console.WriteLine();
                Console.WriteLine("Pause before configuration delete. To continue, click Enter...");
                Console.ReadKey();

                // Delete the configuration.
                await DeleteCORSConfigurationAsync();

                // Retrieve a nonexistent configuration.
                configuration = await RetrieveCORSConfigurationAsync();
            }
            catch (AmazonS3Exception e)
            {
                Console.WriteLine("Error encountered on server. Message:'{0}' when writing an object", e.Message);
            }
            catch (Exception e)
            {
                Console.WriteLine("Unknown encountered on server. Message:'{0}' when writing an object", e.Message);
            }
        }

        static async Task PutCORSConfigurationAsync(CORSConfiguration configuration)
        {

            PutCORSConfigurationRequest request = new PutCORSConfigurationRequest
            {
                BucketName = bucketName,
                Configuration = configuration
            };

            var response = await s3Client.PutCORSConfigurationAsync(request);
        }

        static async Task<CORSConfiguration> RetrieveCORSConfigurationAsync()
        {
            GetCORSConfigurationRequest request = new GetCORSConfigurationRequest
            {
                BucketName = bucketName

            };
            var response = await s3Client.GetCORSConfigurationAsync(request);
            var configuration = response.Configuration;
            PrintCORSRules(configuration);
            return configuration;
        }

        static async Task DeleteCORSConfigurationAsync()
        {
            DeleteCORSConfigurationRequest request = new DeleteCORSConfigurationRequest
            {
                BucketName = bucketName
            };
            await s3Client.DeleteCORSConfigurationAsync(request);
        }

        static void PrintCORSRules(CORSConfiguration configuration)
        {
            Console.WriteLine();

            if (configuration == null)
            {
                Console.WriteLine("\nConfiguration is null");
                return;
            }

            Console.WriteLine("Configuration has {0} rules:", configuration.Rules.Count);
            foreach (CORSRule rule in configuration.Rules)
            {
                Console.WriteLine("Rule ID: {0}", rule.Id);
                Console.WriteLine("MaxAgeSeconds: {0}", rule.MaxAgeSeconds);
                Console.WriteLine("AllowedMethod: {0}", string.Join(", ", rule.AllowedMethods.ToArray()));
                Console.WriteLine("AllowedOrigins: {0}", string.Join(", ", rule.AllowedOrigins.ToArray()));
                Console.WriteLine("AllowedHeaders: {0}", string.Join(", ", rule.AllowedHeaders.ToArray()));
                Console.WriteLine("ExposeHeader: {0}", string.Join(", ", rule.ExposeHeaders.ToArray()));
            }
        }
    }
}

To set a CORS configuration on your bucket, you can use the AWS Management Console. If your application requires it, you can also send REST requests directly. The following sections in the Amazon Simple Storage Service API Reference describe the REST API actions related to the CORS configuration: