cross-referencing cloudformation not working - aws-cloudformation

Question

I have created a policy template and outputted the ARN:
Resources:
# Codebuild Policies
CodeBuildServiceRolePolicy1:
Type: AWS::IAM::ManagedPolicy
Properties:
Description: 'This service role enables AWS CodePipeline to interact with other AWS services, including AWS CodeBuild, on your behalf'
Path: "/"
PolicyDocument:
Version: "2012-10-17"
Statement:
- Resource: "*"
Effect: "Allow"
Action:
...
Outputs:
StackName:
Value: !Ref AWS::StackName
CodeBuildServiceRolePolicy:
Description: The ARN of the ManagedPolicy1
Value: !Ref CodeBuildServiceRolePolicy1
Export:
Name: !Sub '${EnvironmentName}-CodeBuildServiceRolePolicy1'
Now I want o import these Policy into a template with Roles and
# Codebuilding service role
CodeBuildRole:
Type: AWS::IAM::Role
Properties:
RoleName: !Sub ${EnvironmentName}-CodeBuildRole
AssumeRolePolicyDocument:
Statement:
- Action: ["sts:AssumeRole"]
Effect: Allow
Principal:
Service: [codebuild.amazonaws.com]
Version: "2012-10-17"
Path: /
Policies:
- PolicyDocument:
Fn::ImportValue:
!Sub ${EnvironmentName}-CodeBuildServiceRolePolicy1'
But this fails. I'm getting an error, what is wrong?
merci in advance
A

Answer 1

Have you tried to reference the Managed Policy you created with your first stack, using the !Ref function?
The CF for the policy:
AWSTemplateFormatVersion: "2010-09-09"
Resources:
CodeBuildServiceRolePolicy1:
Type: AWS::IAM::ManagedPolicy
Properties:
Path: "/"
PolicyDocument:
...
Outputs:
CodeBuildServiceRolePolicy:
Value: !Ref CodeBuildServiceRolePolicy1.Arn
The CF for the role:
AWSTemplateFormatVersion: "2010-09-09"
Parameters:
PolicyName:
Type: String
Resources:
CodeBuildRole:
Type: "AWS::IAM::Role"
Properties:
Path: "/"
Policies: !Ref PolicyName
Also checkout the docs for Cloudformation IAM an CloudFormation Functions

Answer 2

The solution is to use the AWS resource Type: AWS::IAM::ManagedPolicy instead of AWS::IAM::Policy .
If you use AWS::IAM::ManagedPolicy you can export the policy ARN like this
CodeBuildServiceRolePolicy:
Description: ARN of the managed policy
Value: !Ref CodeBuildServiceRolePolicy
and import it into another template with fn::ImportValue or fn::GetAtt
Using AWS::IAM::Policy only allows to create inline policies which cannot be referenced.