ECR Image Tag Not Immutable

• Query id: 33f41d31-86b1-46a4-81f7-9c9a671f59ac
• Query name: ECR Image Tag Not Immutable
• Platform: CloudFormation
• Severity: Medium
• Category: Insecure Configurations
• URL: Github

Description

ECR should have an image tag be immutable. This prevents image tags from being overwritten.
Documentation

Code samples

Code samples with security vulnerabilities

Postitive test num. 1 - yaml file

Resources:
  MyRepository3:
    Type: AWS::ECR::Repository
    Properties:
      ImageTagMutability: "MUTABLE"
      RepositoryName: "test-repository"
      RepositoryPolicyText:
        Version: "2012-10-17"
        Statement:
          -
            Sid: AllowPushPull
            Effect: Allow
            Principal:
              AWS:
                - "arn:aws:iam::123456789012:user/Bob"
                - "arn:aws:iam::123456789012:user/Alice"
            Action:
              - "ecr:GetDownloadUrlForLayer"
              - "ecr:BatchGetImage"
              - "ecr:BatchCheckLayerAvailability"
              - "ecr:PutImage"
              - "ecr:InitiateLayerUpload"
              - "ecr:UploadLayerPart"
              - "ecr:CompleteLayerUpload"
  MyRepository4:
    Type: AWS::ECR::Repository
    Properties:
      RepositoryName: "test-repository"
      RepositoryPolicyText:
        Version: "2012-10-17"
        Statement:
          -
            Sid: AllowPushPull
            Effect: Allow
            Principal:
              AWS:
                - "arn:aws:iam::123456789012:user/Bob"
                - "arn:aws:iam::123456789012:user/Alice"
            Action:
              - "ecr:GetDownloadUrlForLayer"
              - "ecr:BatchGetImage"
              - "ecr:BatchCheckLayerAvailability"
              - "ecr:PutImage"
              - "ecr:InitiateLayerUpload"
              - "ecr:UploadLayerPart"
              - "ecr:CompleteLayerUpload"

Postitive test num. 2 - json file

{
  "Resources": {
    "MyRepository5": {
      "Type": "AWS::ECR::Repository",
      "Properties": {
        "ImageTagMutability": "MUTABLE",
        "RepositoryName": "test-repository",
        "RepositoryPolicyText": {
          "Version": "2008-10-17",
          "Statement": [
            {
              "Sid": "AllowPushPull",
              "Effect": "Allow",
              "Principal": {
                "AWS": [
                  "arn:aws:iam::123456789012:user/Bob",
                  "arn:aws:iam::123456789012:user/Alice"
                ]
              },
              "Action": [
                "ecr:GetDownloadUrlForLayer",
                "ecr:BatchGetImage",
                "ecr:BatchCheckLayerAvailability",
                "ecr:PutImage",
                "ecr:InitiateLayerUpload",
                "ecr:UploadLayerPart",
                "ecr:CompleteLayerUpload"
              ]
            }
          ]
        }
      }
    },
    "MyRepository6": {
      "Type": "AWS::ECR::Repository",
      "Properties": {
        "RepositoryName": "test-repository",
        "RepositoryPolicyText": {
          "Version": "2008-10-17",
          "Statement": [
            {
              "Sid": "AllowPushPull",
              "Effect": "Allow",
              "Principal": {
                "AWS": [
                  "arn:aws:iam::123456789012:user/Bob",
                  "arn:aws:iam::123456789012:user/Alice"
                ]
              },
              "Action": [
                "ecr:GetDownloadUrlForLayer",
                "ecr:BatchGetImage",
                "ecr:BatchCheckLayerAvailability",
                "ecr:PutImage",
                "ecr:InitiateLayerUpload",
                "ecr:UploadLayerPart",
                "ecr:CompleteLayerUpload"
              ]
            }
          ]
        }
      }
    }
  }
}

Code samples without security vulnerabilities

Negative test num. 1 - yaml file

Resources:
  MyRepository:
    Type: AWS::ECR::Repository
    Properties:
      ImageTagMutability: "IMMUTABLE"
      RepositoryName: "test-repository"
      RepositoryPolicyText:
        Version: "2012-10-17"
        Statement:
          -
            Sid: AllowPushPull
            Effect: Allow
            Principal:
              AWS:
                - "arn:aws:iam::123456789012:user/Bob"
                - "arn:aws:iam::123456789012:user/Alice"
            Action:
              - "ecr:GetDownloadUrlForLayer"
              - "ecr:BatchGetImage"
              - "ecr:BatchCheckLayerAvailability"
              - "ecr:PutImage"
              - "ecr:InitiateLayerUpload"
              - "ecr:UploadLayerPart"
              - "ecr:CompleteLayerUpload"

Negative test num. 2 - json file

{
  "Resources": {
    "MyRepository2": {
      "Type": "AWS::ECR::Repository",
      "Properties": {
        "ImageTagMutability": "IMMUTABLE",
        "RepositoryName": "test-repository",
        "RepositoryPolicyText": {
          "Version": "2008-10-17",
          "Statement": [
            {
              "Sid": "AllowPushPull",
              "Effect": "Allow",
              "Principal": {
                "AWS": [
                  "arn:aws:iam::123456789012:user/Bob",
                  "arn:aws:iam::123456789012:user/Alice"
                ]
              },
              "Action": [
                "ecr:GetDownloadUrlForLayer",
                "ecr:BatchGetImage",
                "ecr:BatchCheckLayerAvailability",
                "ecr:PutImage",
                "ecr:InitiateLayerUpload",
                "ecr:UploadLayerPart",
                "ecr:CompleteLayerUpload"
              ]
            }
          ]
        }
      }
    }
  }
}