AWS S3 bucket – Allow download files to every IAM and Users from specific AWS Account

The AWS CLI now supports the --query parameter which takes a JMESPath expressions.

This means you can sum the size values given by list-objects using sum(Contents[].Size) and count like length(Contents[]).

This can be be run using the official AWS CLI as below and was introduced in Feb 2014

 aws s3api list-objects --bucket BUCKETNAME --output json --query "[sum(Contents[].Size), length(Contents[])]"

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