No Policy Wildcards | Vulnerability Database

IAM policy should avoid use of wildcards and instead apply the principle of least privilege

You should use the principle of least privilege when defining your IAM policies. This means you should specify each exact permission required without using wildcards, as this could cause the granting of access to certain undesired actions, resources and principals.

Impact

Overly permissive policies may grant access to sensitive resources

Recommended Actions

Follow the appropriate remediation steps below to resolve the issue.

Specify the exact permissions required, and to which resources they should apply instead of using wildcards.

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AWSTemplateFormatVersion: 2010-09-09
Description: Good example of policy
Resources:
  GoodPolicy:
    Type: 'AWS::IAM::Policy'
    Properties:
      PolicyName: CFNUsers
      PolicyDocument:
        Version: "2012-10-17"
        Statement:
          - Effect: Allow
            Action:
              - 's3:ListBuckets'
            Resource: 'specific-bucket'

Specify the exact permissions required, and to which resources they should apply instead of using wildcards.

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 resource "aws_iam_role_policy" "test_policy" {
 	name = "test_policy"
 	role = aws_iam_role.test_role.id
 
 	policy = data.aws_iam_policy_document.s3_policy.json
 }
 
 resource "aws_iam_role" "test_role" {
 	name = "test_role"
 	assume_role_policy = jsonencode({
 		Version = "2012-10-17"
 		Statement = [
 		{
 			Action = "sts:AssumeRole"
 			Effect = "Allow"
 			Sid    = ""
 			Principal = {
 			Service = "s3.amazonaws.com"
 			}
 		},
 		]
 	})
 }
 
 data "aws_iam_policy_document" "s3_policy" {
   statement {
     principals {
       type        = "AWS"
       identifiers = ["arn:aws:iam::${data.aws_caller_identity.current.account_id}:root"]
     }
     actions   = ["s3:GetObject"]
     resources = [aws_s3_bucket.example.arn]
   }
 }
 

Remediation Links

https://registry.terraform.io/providers/hashicorp/aws/latest/docs/data-sources/iam_policy_document