Grant access to read a subdirectory within an Amazon S3 bucket - amazon-web-services

Question

I've never used AWS S3 before. We use it to automatically backup call recordings for clients. One of our clients for audit purposes needs access to their recordings.
I am using the client CyberDuck as a way to access the files.
I want to give them access to only their files.
Our file structure is as follows:
recordings/12345/COMPANYNAMEHERE/
I just learned that you build and do things based on scripts and policies. So I did some research and tried to build one but I get an access denied on listing.
Just curious if I am going about this correctly.
{
"Version": "2012-10-17",
"Statement": [
{
"Effect": "Allow",
"Action": "s3:ListAllMyBuckets",
"Resource": "arn:aws:s3:::*"
},
{
"Effect": "Allow",
"Action": "s3:*",
"Resource": [
"arn:aws:s3:::recordings/12345/COMPANYNAMEHERE",
"arn:aws:s3:::recordings/12345/COMPANYNAMEHERE/*"
]
}
]
}

Answer 1

You have only given them permission to ListAllMyBuckets, which means they can only list the names of your buckets, and can't do anything else.
If you have already created an IAM User for them, then giving them this policy would allow them to list and retrieve their files, but only from the given directory (or, more accurately, with the given prefix):
{
"Version": "2012-10-17",
"Statement": [
{
"Action": [
"s3:ListBucket"
],
"Effect": "Allow",
"Resource": [
"arn:aws:s3:::my-bucket"
],
"Condition": {
"StringLike": {
"s3:prefix": [
"recordings/123/*"
]
}
}
},
{
"Action": [
"s3:GetObject"
],
"Effect": "Allow",
"Resource": [
"arn:aws:s3:::my-bucket/recordings/123/*"
]
}
]
}
If you do this a lot with customers, then you can use IAM Policy Variables to create a rule that substitutes their username:
{
"Version": "2012-10-17",
"Statement": [
{
"Action": [
"s3:ListBucket"
],
"Effect": "Allow",
"Resource": [
"arn:aws:s3:::my-bucket"
],
"Condition": {
"StringLike": {
"s3:prefix": [
"recordings/${aws:username}/*"
]
}
}
},
{
"Action": [
"s3:GetObject"
],
"Effect": "Allow",
"Resource": [
"arn:aws:s3:::my-bucket/recordings/${aws:username}/*"
]
}
]
}