Share buckets in Amazon S3 so that multiple users see them in their management console

I was struggling with this, too, but I found an answer over here https://stackoverflow.com/a/17162973/1750869 that helped resolve this issue for me. Reposting answer below.

You don't have to open permissions to everyone. Use the below Bucket policies on source and destination for copying from a bucket in one account to another using an IAM user

Bucket to Copy from – SourceBucket

Bucket to Copy to – DestinationBucket

Source AWS Account ID - XXXX–XXXX-XXXX

Source IAM User - src–iam-user

The below policy means – the IAM user - XXXX–XXXX-XXXX:src–iam-user has s3:ListBucket and s3:GetObject privileges on SourceBucket/* and s3:ListBucket and s3:PutObject privileges on DestinationBucket/*

On the SourceBucket the policy should be like:

{
"Id": "Policy1357935677554",
"Statement": [
    {
        "Sid": "Stmt1357935647218",
        "Action": [
            "s3:ListBucket"
        ],
        "Effect": "Allow",
        "Resource": "arn:aws:s3:::SourceBucket",
        "Principal": {"AWS": "arn:aws:iam::XXXXXXXXXXXX:user/src–iam-user"}
    },
    {
        "Sid": "Stmt1357935676138",
        "Action": ["s3:GetObject"],
        "Effect": "Allow",
        "Resource": "arn:aws:s3::: SourceBucket/*",
        "Principal": {"AWS": "arn:aws:iam::XXXXXXXXXXXX:user/src–iam-user"}
   }
]
}

On the DestinationBucket the policy should be:

{
"Id": "Policy1357935677554",
"Statement": [
    {
        "Sid": "Stmt1357935647218",
        "Action": [
            "s3:ListBucket"
        ],
        "Effect": "Allow",
        "Resource": "arn:aws:s3::: DestinationBucket",
        "Principal": {"AWS": "arn:aws:iam::XXXXXXXXXXXX:user/src–iam-user"}
    },
    {
        "Sid": "Stmt1357935676138",
        "Action": ["s3:PutObject"],
        "Effect": "Allow",
        "Resource": "arn:aws:s3::: DestinationBucket/*",
        "Principal": {"AWS": "arn:aws:iam::XXXXXXXXXXXX:user/src–iam-user"}
   }
]
}

command to be run is s3cmd cp s3://SourceBucket/File1 s3://DestinationBucket/File1

It sounds like you might need to specify both the bucket and its contents in the Resource tag - some permissions apply directly to the bucket only and other permissions apply to objects only, e.g.

"Resource": [
            "arn:aws:s3:::test33333",
            "arn:aws:s3:::test33333/*"
        ]

https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_policies_elements_notprincipal.html#specifying-notprincipal