首先，在CloudFormation中，您需要提供Lambda函数的执行角色，并将其赋予事件桥接目标中的Lambda函数，就像这样：

Resources:
  MyFunction:
    Type: 'AWS::Lambda::Function'
    Properties:
      Code:
        S3Bucket: mybucket
        S3Key: myfunction.zip
      Handler: index.handler
      Role: !GetAtt MyExecutionRole.Arn
      Runtime: nodejs12.x

  MyExecutionRole:
    Type: 'AWS::IAM::Role'
    Properties:
      AssumeRolePolicyDocument:
        Version: '2012-10-17'
        Statement:
          - Effect: Allow
            Principal:
              Service: lambda.amazonaws.com
            Action: sts:AssumeRole
      ManagedPolicyArns:
        - 'arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole'
        - 'arn:aws:iam::aws:policy/AmazonEventBridgeInvocationAccess'

现在，我们需要使用Lambda函数的执行角色来创建事件桥接目标。这就需要使用RoleArn参数，如下所示：

  MyRule:
    Type: 'AWS::Events::Rule'
    Properties:
      Description: 'My scheduled rule'
      ScheduleExpression: 'cron(0 4 * * ? *)'
      State: ENABLED
      Targets:
        - Arn: !GetAtt MyFunction.Arn
          Id: 'MyTarget'
          RoleArn: !GetAtt MyExecutionRole.Arn

这将确保在Lambda函数执行事件时，它将拥有所需的权限。