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IAM policies allow broad list actions on S3 buckets Affecting IAM service in AWS

Severity

0.0
low
0
10
    Severity Framework
    Snyk CCSS
    Rule category
    IAM / Least Privilege

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    Frameworks
    AWS-Well-Architected CSA-CCM ISO-27001 SOC-2
  • Snyk ID SNYK-CC-00120
  • credit Snyk Research Team
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Description

If a malicious actor gains access to a role with a policy that includes broad list actions such as ListAllMyBuckets, they would be able to enumerate all buckets and potentially extract sensitive data.

How to fix?

Ensure that the policy attribute is set to a policy that does not have wildcard actions.

Following actions are forbidden when they are combined with an unscoped resource.

Actions:

  • s3:*
  • s3:List*
  • s3:ListAllMyBuckets

Resources:

  • *
  • ^arn:aws[-0-9a-z]*:s3:::[*]$

Example Configuration

resource "aws_iam_policy" "valid" {
  policy = jsonencode({
    Version = "2012-10-17"
    Statement = [
      {
        Action = [
          "s3:PutObject",
          "s3:CreateBucket",
          "s3:GetBucketLocation"
        ]
        Effect   = "Allow"
        Resource = "arn:aws:s3:::foobar"
      }
    ]
  })
}

resource "aws_iam_policy" "valid" {
  policy = jsonencode({
    Version = "2012-10-17"
    Statement = [
      {
        Action = ["s3:List*"]
        Effect   = "Allow"
        Resource = "arn:aws:s3:::my-bucket-0123456789"
      }
    ]
  })
}