AWS Q&A: "Access Denied" Errors When Uploading Files to S3 Bucket

Question

Hi, My name is Jurgen.  I’m new to AWS, and I’m trying to upload files to an S3 bucket using the AWS CLI, but I keep getting an “Access Denied” error. I’ve already created the bucket, but I’m not sure if my permissions are set up correctly. How can I troubleshoot this issue and fix the permissions so I can successfully upload files?

Greeting

Hi Jurgen, thanks for your question! I see you’re trying to upload files to your S3 bucket but are getting “Access Denied” errors. No worries—let’s get you up and running quickly so you can store your files securely! 😊

Clarifying the Issue

From what you’ve shared, it sounds like you’ve set up an S3 bucket and are trying to upload files, but the operation fails due to a permissions issue. This often happens when the IAM policy associated with your user or role doesn’t grant the necessary actions for uploading files.

When this issue occurs, you might encounter the following:

AWS CLI:

If you’re uploading a file with the CLI, you might see:

An error occurred (AccessDenied) when calling the PutObject operation: Access Denied

AWS Management Console:

When uploading directly through the console, you might see an alert:

Error: Access Denied. You do not have permissions to perform this action.

Application Logs:

If you’re using an AWS SDK in an application, you might find logs like:

JSON

{
    "Error": {
        "Code": "AccessDenied",
        "Message": "Access Denied",
        "RequestId": "1234567890ABCDEF",
        "HostId": "abcdefghijklmnopqrstuvwxyz=="
    }
}

These messages indicate that your IAM policy may lack the necessary s3:PutObject permission. Let’s walk through how to fix this step-by-step.

Key Terms

Here are some key terms to help you understand the solution:

• S3 (Simple Storage Service): AWS’s scalable object storage service, ideal for files, backups, and more.
• IAM (Identity and Access Management): The AWS service that manages permissions and access to resources.
• Policy: A JSON document that defines which AWS actions are allowed or denied for a user or role.
• ARN (Amazon Resource Name): A unique identifier for AWS resources, used to specify permissions in policies.
• PutObject: The S3 action that allows file uploads to a bucket.

The Solution (Our Recipe)

Steps at a Glance:

1. Verify the IAM policy for S3 access.
2. Update the IAM policy to grant PutObject permissions.
3. Apply the updated policy and test the upload.

Step-by-Step Guide:

1. Verify the IAM Policy for S3 Access:

• Go to the IAM Console in AWS.
• Select the user or role you’re using to upload files.
• Inspect the attached policies. Look for s3:PutObject in the JSON policy editor or visual summary.

Example of a restrictive policy missing PutObject:

JSON

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": "s3:ListBucket",
            "Resource": "arn:aws:s3:::my-example-bucket"
        }
    ]
}

2. Update the IAM Policy:

• Edit the existing policy or create a new one.
• Add permissions for s3:PutObject, ensuring the Resource specifies your bucket and includes /* for objects.

Example policy for file uploads:

JSON

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "s3:PutObject",
                "s3:GetObject" 
            ],
            "Resource": "arn:aws:s3:::my-example-bucket/*"
        }
    ]
}

3. Apply the Updated Policy and Test the Upload:

• Save and attach the updated policy to your user or role.
• Test the upload via AWS CLI: aws s3 cp myfile.txt s3://my-example-bucket/
• If successful, the file will appear in your bucket without errors. If issues persist, double-check your policy’s Resource ARN for accuracy.

Closing Thoughts

By granting the correct permissions with s3:PutObject, you should now be able to upload files successfully. For added security and visibility, consider enabling CloudTrail to log actions taken in your S3 bucket.

Helpful AWS documentation links:

• Amazon S3 Permissions Overview
• IAM JSON Policy Reference
• AWS CloudTrail Guide
• Using AWS CLI with S3

Farewell

I hope this solves your issue, Jurgen! Let us know if you have any further questions—always happy to help. Best of luck with your AWS journey! 🚀😊

Image:  Pete Linforth from Pixabay