Inline policies are attached to an ECS service

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Metadata

Id: 9e8c89b3-7997-4d15-93e4-7911b9db99fd

Cloud Provider: AWS

Platform: CloudFormation

Severity: Low

Category: Insecure Configurations

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Description

ECS services must reference an IAM role, not an IAM policy, because pointing the service Role property to a policy resource can break permission binding, make access controls harder to manage and audit, and increase the chance of privilege misconfiguration. Check AWS::ECS::Service resources’ Properties.Role. The value must be a reference to an AWS::IAM::Role (logical ID or ARN) and must not be the logical ID of an AWS::IAM::Policy resource. Attach permissions to that role using ManagedPolicyArns, an AWS::IAM::ManagedPolicy, or inline policies defined on the AWS::IAM::Role itself. ECS services whose Role property refers to an AWS::IAM::Policy logical ID will be flagged.

Secure configuration example:

MyEcsRole:
  Type: AWS::IAM::Role
  Properties:
    AssumeRolePolicyDocument:
      Statement:
        - Effect: Allow
          Principal:
            Service: ecs-tasks.amazonaws.com
          Action: sts:AssumeRole
    ManagedPolicyArns:
      - arn:aws:iam::aws:policy/service-role/AmazonECSTaskExecutionRolePolicy

MyEcsService:
  Type: AWS::ECS::Service
  Properties:
    Role: !Ref MyEcsRole

Compliant Code Examples


Resources:
  InlinePolicy:
    Type: AWS::ECS::Service
    DependsOn:
    - Listener
    Properties:
      LoadBalancers:
      - TargetGroupArn:
          Ref: TargetGroup
        ContainerPort: 80
        ContainerName: sample-app
      Cluster:
        Ref: ECSCluster
  IAMPolicy:
    Type: 'AWS::IAM::Policy'
    Properties:
      PolicyName: root
      PolicyDocument:
        Version: 2012-10-17
        Statement:
          - Effect: Allow
            Action: '*'
            Resource: '*'

{
  "Resources": {
    "IAMPolicy": {
      "Properties": {
        "PolicyName": "root",
        "PolicyDocument": {
          "Version": "2012-10-17T00:00:00Z",
          "Statement": [
            {
              "Effect": "Allow",
              "Action": "*",
              "Resource": "*"
            }
          ]
        }
      },
      "Type": "AWS::IAM::Policy"
    },
    "InlinePolicy": {
      "DependsOn": [
        "Listener"
      ],
      "Properties": {
        "LoadBalancers": [
          {
            "TargetGroupArn": {
              "Ref": "TargetGroup"
            },
            "ContainerPort": 80,
            "ContainerName": "sample-app"
          }
        ],
        "Cluster": {
          "Ref": "ECSCluster"
        }
      },
      "Type": "AWS::ECS::Service"
    }
  }
}

Non-Compliant Code Examples

{
  "Resources": {
    "InlinePolicy": {
      "Type": "AWS::ECS::Service",
      "DependsOn": [
        "Listener"
      ],
      "Properties": {
        "Role": {
          "Ref": "IAMPolicy"
        },
        "LoadBalancers": [
          {
            "TargetGroupArn": {
              "Ref": "TargetGroup"
            },
            "ContainerPort": 80,
            "ContainerName": "sample-app"
          }
        ],
        "Cluster": {
          "Ref": "ECSCluster"
        }
      }
    },
    "IAMPolicy": {
      "Type": "AWS::IAM::Policy",
      "Properties": {
        "PolicyName": "root",
        "PolicyDocument": {
          "Version": "2012-10-17T00:00:00Z",
          "Statement": [
            {
              "Effect": "Allow",
              "Action": "*",
              "Resource": "*"
            }
          ]
        }
      }
    }
  }
}

Resources:
  InlinePolicy:
    Type: AWS::ECS::Service
    DependsOn:
    - Listener
    Properties:
      Role:
        Ref: IAMPolicy
      LoadBalancers:
      - TargetGroupArn:
          Ref: TargetGroup
        ContainerPort: 80
        ContainerName: sample-app
      Cluster:
        Ref: ECSCluster
  IAMPolicy:
    Type: 'AWS::IAM::Policy'
    Properties:
      PolicyName: root
      PolicyDocument:
        Version: 2012-10-17
        Statement:
          - Effect: Allow
            Action: '*'
            Resource: '*'