How to download file from others S3 bucket

Hello,

Ensure that an IAM user has a required permissions to make calls to S3 API.

Changing permissions for an IAM user: https://docs.aws.amazon.com/IAM/latest/UserGuide/id_users_change-permissions.html

The minimum required permissions to access all the objects in a bucket might look like this:

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

Yes, you need to ask the person who gave you the key pairs to make sure the IAM user has proper permission. You can also ask the other bucket owner to set up replication so everything under his\her bucket will be replicated to your bucket (you would need to have a bucket policy to allow the replication on your bucket as well)

https://docs.aws.amazon.com/AmazonS3/latest/userguide/replication.html

Another option for you to download files directly from that bucket without using key pairs is to use Presigned URL. This requires the bucket owner to set it up and share the URL with you.