you create a Cross Account Function in CloudFormation

To create a cross-account function in CloudFormation, you’ll be able to comply with these steps:

1. Create a CloudFormation template

Create a brand new CloudFormation template in YAML or JSON format. This template will outline the assets, together with the cross-account function, that you simply wish to create.

2. Outline the cross-account function

Inside your CloudFormation template, outline the cross-account function utilizing the AWS::IAM::Function useful resource kind. Specify the required properties akin to RoleName, AssumeRolePolicyDocument, and ManagedPolicyArns.

• RoleName: Present a reputation for the cross-account function.
• AssumeRolePolicyDocument: Specify the belief coverage that determines which accounts are allowed to imagine this function. It ought to embody the AWS account ID or ARN of the trusted account(s) that can assume the function.
• ManagedPolicyArns: Optionally, you’ll be able to connect managed insurance policies to the function by specifying their Amazon Useful resource Names (ARNs). These insurance policies outline the permissions and entry rights for the function.

3. Grant permissions for cross-account entry

Within the account that will likely be assuming the cross-account function, that you must grant permissions to the trusted account to imagine the function. That is sometimes executed by creating an IAM coverage within the trusted account and attaching it to a consumer, group, or function.

4. Deploy the CloudFormation stack

Use the AWS Administration Console, AWS CLI, or SDKs to deploy the CloudFormation stack utilizing your template. Guarantee that you’ve got the required permissions in each the trusted and trusting accounts.

When the CloudFormation stack is deployed, it’s going to create the cross-account function within the trusting account. The trusted account(s) can then assume the function and entry assets within the trusting account based mostly on the permissions granted to the function.

It’s vital to make sure that the suitable belief relationships and permissions are in place to securely set up cross-account entry.

Instance of CloudFormation code

Right here’s an instance of CloudFormation code to create a cross-account function:

AWSTemplateFormatVersion: '2010-09-09'
Sources:
  CrossAccountRole:
    Kind: 'AWS::IAM::Function'
    Properties:
      RoleName: MyCrossAccountRole
      AssumeRolePolicyDocument:
        Model: '2012-10-17'
        Assertion:
          - Impact: Enable
            Principal:
              AWS:
                - 'arn:aws:iam::TRUSTED_ACCOUNT_ID:root'
            Motion: 'sts:AssumeRole'
      ManagedPolicyArns:
        - 'arn:aws:iam::AWS_MANAGED_POLICY_ARN'
        - 'arn:aws:iam::ANOTHER_MANAGED_POLICY_ARN'

On this instance:

• The RoleName property units the identify of the cross-account function to “MyCrossAccountRole”. You may change it as per your desire.
• The AssumeRolePolicyDocument specifies the belief coverage permitting solely the trusted account with the required TRUSTED_ACCOUNT_ID to imagine the function. Modify TRUSTED_ACCOUNT_ID to the precise AWS account ID or ARN of the trusted account.
• The ManagedPolicyArns property permits you to connect a number of managed insurance policies to the function. The instance consists of two instance ARNs (AWS_MANAGED_POLICY_ARN and ANOTHER_MANAGED_POLICY_ARN) you could substitute with the precise ARNs of the managed insurance policies you wish to connect.

Within the different account (the trusted account), that you must create an IAM coverage that grants permissions to imagine the cross-account function created within the trusting account. Right here’s an instance of CloudFormation code you could run within the trusted account:

AWSTemplateFormatVersion: '2010-09-09'
Sources:
  CrossAccountAccessPolicy:
    Kind: 'AWS::IAM::Coverage'
    Properties:
      PolicyName: CrossAccountAccessPolicy
      PolicyDocument:
        Model: '2012-10-17'
        Assertion:
          - Impact: Enable
            Motion: 'sts:AssumeRole'
            Useful resource: 'arn:aws:iam::TRUSTING_ACCOUNT_ID:function/MyCrossAccountRole'
      Roles:
        - Ref: CrossAccountAccessRole
  CrossAccountAccessRole:
    Kind: 'AWS::IAM::Function'
    Properties:
      RoleName: CrossAccountAccessRole
      AssumeRolePolicyDocument:
        Model: '2012-10-17'
        Assertion:
          - Impact: Enable
            Principal:
              AWS:
                - 'arn:aws:iam::TRUSTED_ACCOUNT_ID:root'
            Motion: 'sts:AssumeRole'

On this instance:

• The CrossAccountAccessPolicy useful resource defines an IAM coverage named “CrossAccountAccessPolicy” that enables the trusted account to imagine the function created within the trusting account.
• The PolicyDocument specifies the permissions granted by the coverage. On this case, it permits the trusted account to carry out the sts:AssumeRole motion on the function with the ARN 'arn:aws:iam::TRUSTING_ACCOUNT_ID:function/MyCrossAccountRole'. Modify TRUSTING_ACCOUNT_ID to the precise AWS account ID or ARN of the trusting account, and regulate the function ARN in case you have custom-made the function identify.
• The CrossAccountAccessRole useful resource creates a placeholder IAM function with the identify “CrossAccountAccessRole” within the trusted account. The trusted account assumes this function to entry assets within the trusting account.

Bear in mind to interchange the placeholder values and modify the code to suit your particular account IDs, function names, and any further permissions or insurance policies required.