Why is my access denied on s3 (using the aws-sdk for Node.js)?

The problem was that my new IAM user didn't have a policy attached to it. I assigned it the AmazonS3FullAccess policy and now it works.

As pointed out in the comments, a more restrictive policy would be much safer

This could also happen if you're trying to set ACL to "public-read" but the bucket is blocking public access. For example if you mean to upload static assets to a misconfigured S3 bucket. You can change it in your bucket settings.

These errors can occur when the object which you are trying to read does not exist. From what I understood the AWS errors are not so clear in these situations.

Validate if your key/bucket is correct and if you are sending the correct params on the API method.

I already got this problem two times:

• when I was replacing the key param with the bucket param and vice versa and I was trying to read an s3 object using the getObject() method.
• when I was trying to copy a file to a location that did not exist using the copyObject() method.

FullAccess in your policy is not required. You can try something like this:

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "VisualEditor0",
            "Effect": "Allow",
            "Action": [
                "s3:Put*",
                "s3:Get*",
                "s3:List*",
                "s3:Delete*"
            ],
            "Resource": [
                "arn:aws:s3:::bucket/*",
                "arn:aws:s3:::bucket"
            ]
        },
        {
            "Sid": "VisualEditor1",
            "Effect": "Allow",
            "Action": "s3:ListAllMyBuckets",
            "Resource": "*"
        }
    ]
}