AWS Cloudformation Role is not authorized to perform AssumeRole on Role

Question

I am trying to execute a cloudformation stack which contains the following resources:

• Codebuild project
• Codepipeline pipeline
• Roles needed

While trying to execute the stack, it fails with the following error:

arn:aws:iam::ACCOUNT_ID:role/CodePipelineRole is not authorized to perform AssumeRole on role arn:aws:iam::ACCOUNT_ID:role/CodePipelineRole (Service: AWSCodePipeline; Status Code: 400; Error Code: InvalidStructureException; Request ID: 7de2b1c6-a432-47e6-8208-2c0072ebaf4b)

I created the role using a managed policy, but I have already tried with a normal policy and it does not work neither.

This is the Role Policy:

CodePipelinePolicy:
Type: AWS::IAM::ManagedPolicy
Properties:
  Description: 'This policy grants permissions to a service role to enable Codepipeline to use multiple AWS Resources on the users behalf'
  Path: "/"
  PolicyDocument:
    Version: "2012-10-17"
    Statement:
      - Resource: "*"
        Effect: "Allow"
        Condition: {}
        Action:
          - autoscaling:*
          - cloudwatch:*
          - cloudtrail:*
          - cloudformation:*
          - codebuild:*
          - codecommit:*
          - codedeploy:*
          - codepipeline:*
          - ec2:*
          - ecs:*
          - ecr:*
          - elasticbeanstalk:*
          - elasticloadbalancing:*
          - iam:*
          - lambda:*
          - logs:*
          - rds:*
          - s3:*
          - sns:*
          - ssm:*
          - sqs:*
          - kms:*

This is the Role

CodePipelineRole:
Type: "AWS::IAM::Role"
Properties:
  RoleName: !Sub ${EnvironmentName}-CodePipelineRole
  AssumeRolePolicyDocument:
    Version: '2012-10-17'
    Statement:
      - Action:
        - 'sts:AssumeRole'
        Effect: Allow
        Principal:
          Service:
          - codepipeline.amazonaws.com
  Path: /
  ManagedPolicyArns:
    - !Ref CodePipelinePolicy

What intrigues me the most is that it seems like CodePipelineRole is trying to AssumeRole to itself. I'm not understanding what can be happening here.

And when I set the policy's action to *, it works! I don't know what permissions could be missing.

Thanks

Answer 1

It is to do with the trust relationship for the role you have created i.e. CodePipelineRole

1. Go to the Role in IAM

2. Select the Trust Relationships tab ...

3. Then Edit Trust Relationship to include codepipeline

     "Version": "2012-10-17",
     "Statement": [
       {
         "Effect": "Allow",
         "Principal": {
           "Service": [
             "codepipeline.amazonaws.com"
           ]
         },
         "Action": "sts:AssumeRole"
       }
     ]
   }```
   

Answer 2

It seems like, behind the scenes, AWS services keep some kind of role cache. If you try to make a role, attach a policy and create a new CodeBuild project sequentially, CodeBuild will give an unauthorized error because it can't find the role. It's similar to getting a forbidden access error on a non-existing bucket (instead of a 404). If you separate the stack in two other stacks: first you create the roles and then you create the CodeBuild, it works. I don't understand why the CLI command works instantly though.