S3 Bucket Does Not Allow ACLs Error

The "The bucket does not allow ACLs" error occurs when attempting to upload objects to an Amazon S3 bucket with ACL (Access Control List) settings, but the bucket configuration prevents ACL usage. This is a common issue due to Amazon's shift from ACLs to bucket policies for access control.

Problem Overview

When AWS S3 buckets are created after April 2023, they default to using bucket policies rather than ACLs for access control. The error typically appears when:

• Using CannedACL properties in SDK calls (like S3CannedACL.PublicRead)
• Setting public visibility flags during upload operations
• The bucket has ACLs disabled at the ownership level

Solution 1: Enable ACLs in Bucket Settings (Quick Fix)

The most straightforward solution is to enable ACLs in your S3 bucket settings:

1. Navigate to your S3 bucket in the AWS Console
2. Go to the Permissions tab
3. Find the Object Ownership section and click Edit
4. Select ACLs enabled (instead of Bucket owner enforced)
5. Save changes

WARNING

Enabling ACLs may not be the recommended approach for new implementations. Consider Solution 2 for a more modern approach.

Solution 2: Use Bucket Policies Instead of ACLs (Recommended)

The preferred method is to disable ACLs and use bucket policies exclusively:

Step 1: Configure Bucket to Disable ACLs

Use the AWS CLI to configure your bucket properly:

aws s3api put-public-access-block --bucket YOUR_BUCKET_NAME \
  --public-access-block-configuration '{
    "BlockPublicAcls": true,
    "IgnorePublicAcls": true,
    "BlockPublicPolicy": false,
    "RestrictPublicBuckets": false
  }'

aws s3api put-bucket-ownership-controls --bucket YOUR_BUCKET_NAME \
  --ownership-controls 'Rules=[{ObjectOwnership="BucketOwnerEnforced"}]'

Step 2: Create a Comprehensive Bucket Policy

Implement a bucket policy that handles both authentication and public access:

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Sid": "AllowAuthenticatedUsers",
      "Effect": "Allow",
      "Principal": {
        "AWS": "arn:aws:iam::YOUR_ACCOUNT_ID:user/YOUR_USER"
      },
      "Action": [
        "s3:PutObject",
        "s3:GetObject",
        "s3:ListBucket",
        "s3:DeleteObject",
        "s3:PutObjectAcl",
        "s3:GetObjectAcl"
      ],
      "Resource": [
        "arn:aws:s3:::YOUR_BUCKET_NAME/*",
        "arn:aws:s3:::YOUR_BUCKET_NAME"
      ]
    },
    {
      "Sid": "AllowPublicRead",
      "Effect": "Allow",
      "Principal": "*",
      "Action": "s3:GetObject",
      "Resource": "arn:aws:s3:::YOUR_BUCKET_NAME/*"
    }
  ]
}

Step 3: Modify Your Upload Code

Remove the ACL specification from your upload code:

[HttpPost]
public bool UploadFile(string file)
{
    var s3Client = new AmazonS3Client(accesskey, secretkey, RegionEndpoint.APSoutheast1);
    
    var fileTransferUtility = new TransferUtility(s3Client);
    if (file.Length > 0)
    {
        var filePath = file;
        var fileTransferUtilityRequest = new TransferUtilityUploadRequest
        {
            BucketName = bucketName,
            FilePath = filePath,
            StorageClass = S3StorageClass.StandardInfrequentAccess,
            PartSize = 6291456, // 6 MB
            Key = keyName
            // Removed: CannedACL = S3CannedACL.PublicRead
        };
        fileTransferUtilityRequest.Metadata.Add("param1", "Value1");
        fileTransferUtilityRequest.Metadata.Add("param2", "Value2");
        fileTransferUtility.Upload(fileTransferUtilityRequest);
        fileTransferUtility.Dispose();
    }
    return true;
}

Solution 3: Framework-Specific Configuration

For Laravel and other frameworks, ensure your configuration doesn't specify ACLs:

's3' => [
    'driver' => 's3',
    'key' => env('AWS_ACCESS_KEY_ID'),
    'secret' => env('AWS_SECRET_ACCESS_KEY'),
    'region' => env('AWS_DEFAULT_REGION'),
    'bucket' => env('AWS_BUCKET'),
    'url' => env('AWS_URL'),
    'endpoint' => env('AWS_ENDPOINT'),
    'options' => [
        'ACL' => '', // Empty string instead of 'public'
    ],
]

Best Practices and Recommendations

1. Prefer bucket policies over ACLs for new implementations
2. Use IAM roles and policies for fine-grained access control
3. Avoid public access unless absolutely necessary
4. Regularly audit your bucket policies and access patterns
5. Use AWS CloudTrail to monitor access attempts and errors

TIP

When working with S3 buckets created after April 2023, AWS recommends using bucket policies rather than object ACLs for access control. This provides better security management and auditing capabilities.

Troubleshooting Existing Objects

If you have existing objects that need their permissions updated:

1. Select the objects in the S3 console
2. Choose Actions → Make public using ACL
3. Confirm the action

This will update the visibility settings for existing objects while you transition to bucket policies.

Conclusion

The "bucket does not allow ACLs" error indicates a mismatch between your upload configuration and bucket settings. While enabling ACLs provides a quick fix, migrating to bucket policies offers better security and maintainability. Choose the solution that best fits your use case, with Solution 2 being the recommended approach for new applications.