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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-ArchitectedCSA-CCMISO-27001SOC-2
  • Snyk IDSNYK-CC-00120
  • creditSnyk 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"
      }
    ]
  })
}