https://etherarp.net/lets-encrypt-and-amazon-s3/

s3-certbot-policy.json

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "AllowCertbot",
            "Effect": "Allow",
            "Action": [
                "s3:GetObject",
                "s3:PutObject",
                "s3:PutObjectACL",
                "s3:DeleteObject"
            ],
            "Condition": {
                "IpAddress": {
                    "aws:SourceIp": "0.0.0.0/0"
                }
            },
            "Resource": [
                "arn:aws:s3:::*/.well-known/acme-challenge/*"
            ]
        }
    ]
}