How principal works when restrictingS 3 access by bucket policy

Question

Currently my S3 policy is like this below.

What I want to do is restrict read/write S3 access from a lambda. And enable public read access to S3.

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Principal": {
                "AWS": "*"
            },
            "Action": "s3:GetObject",
            "Resource": "arn:aws:s3:::s3-static-resource-v/*"
        },
        {
            "Effect": "Allow",
            "Principal": {
                "AWS": "arn:aws:iam::678100228133:role/vr-resource-CustomS3AutoDeleteObjectsCustomRes-1H51E87NWQJ81"
            },
            "Action": [
                "s3:GetBucket*",
                "s3:List*",
                "s3:DeleteObject*"
            ],
            "Resource": [
                
                "arn:aws:s3:::s3-static-resource-v",
                "arn:aws:s3:::s3-static-resource-v/*"
            ]
        }
    ]
}

I guess I should add the lambda arn in Principal,

so I changed,

        "Principal": {
            "AWS": "*"
        },

to lambda arn, but

        "Principal": {
            "AWS": "arn:aws:lambda:ap-northeast-1:67810022843r:function:vr-dev-lambda"
        },

but it shows

Invalid principal in policy

How can I set here?

Answer 1

Lambdas have an execution roles attached to them. For example:

If you want to limit the S3 access to your Lambda, you would want to specify the ARN of this execution role.