AWS CDK Cross Account Lambda Deployment Permission Issue - aws-lambda

Question

I followed the following tutorial to create a Lambda deploy pipeline using CDK. When I try to keep everything in the same account it works well.
https://docs.aws.amazon.com/cdk/latest/guide/codepipeline_example.html
But my scenario is slightly different from the example because it involves two AWS accounts instead one. I maintain application source code and pipeline
in the OPS account and this pipeline will deploy the Lambda application to the UAT account.
OPS Account (12345678) - CodeCommit repo & CodePipeline
UAT Account (87654321) - Lambda application
As per the aws following aws documentation (Cross-account actions section) I made the following changes to source code.
https://docs.aws.amazon.com/cdk/api/latest/docs/aws-codepipeline-actions-readme.html
Lambda stack expose deploy action role as follows
export class LambdaStack extends cdk.Stack {
public readonly deployActionRole: iam.Role;
constructor(scope: cdk.Construct, id: string, props?: cdk.StackProps) {
...
this.deployActionRole = new iam.Role(this, 'ActionRole', {
assumedBy: new iam.AccountPrincipal('12345678'), //pipeline account
// the role has to have a physical name set
roleName: 'DeployActionRole',
});
}
}
In the pipeline stack,
new codePipeline.Pipeline(this, 'MicroServicePipeline', {
pipelineName: 'MicroServicePipeline',
stages: [
{
stageName: 'Deploy',
actions: [
new codePipelineAction.CloudFormationCreateUpdateStackAction({
role: props.deployActionRole,
....
})
]
}
]
});
Following is how I initiate stacks
const app = new cdk.App();
const opsEnv: cdk.Environment = {account: '12345678', region: 'ap-southeast-2'};
const uatEnv: cdk.Environment = {account: '87654321', region: 'ap-southeast-2'};
const lambdaStack = new LambdaStack(app, 'LambdaStack', {env: uatEnv});
const lambdaCode = lambdaStack.lambdaCode;
const deployActionRole = lambdaStack.deployActionRole;
new MicroServicePipelineStack(app, 'MicroServicePipelineStack', {
env: opsEnv,
stackName: 'MicroServicePipelineStack',
lambdaCode,
deployActionRole
});
app.synth();
AWS credentials profiles looks liks
[profile uatadmin]
role_arn=arn:aws:iam::87654321:role/PigletUatAdminRole
source_profile=opsadmin
region=ap-southeast-2
when I run cdk diff or deploy I get an error saying,
➜ infra git:(master) ✗ cdk diff MicroServicePipelineStack --profile uatadmin
Including dependency stacks: LambdaStack
Stack LambdaStack
Need to perform AWS calls for account 87654321, but no credentials have been configured.
What have I done wrong here? Is it my CDK code or is it the way I have configured my AWS profile?
Thanks,
Kasun

Answer 1

The problem is with your AWS CLI configuration. You cannot use the CDK CLI natively to deploy resources in two separate accounts with one CLI command. There is a recent blog post on how to tell CDK which credentials to use, depending on the stack environment parameter:
https://aws.amazon.com/blogs/devops/cdk-credential-plugin/
The way we use it is to deploy stacks into separate accounts with multiple CLI commands specifying the required profile. All parameters that need to be exchanged (such as the location of your lambdaCode) is passed via e.g. environment variables.

Answer 2

Just try to use using the environment variables:
AWS_ACCESS_KEY_ID
AWS_SECRET_ACCESS_KEY
AWS_DEFAULT_REGION
https://docs.aws.amazon.com/cli/latest/userguide/cli-configure-envvars.html
Or
~/.aws/credentials
[default]
aws_access_key_id=****
aws_secret_access_key=****
~/.aws/config
[default]
region=us-west-2
output=json
https://docs.aws.amazon.com/cli/latest/userguide/cli-configure-files.html
It works for me.
I'm using cdk version 1.57.0

Answer 3

The issue is in the fact that you have resources that exist in multiple accounts and hence there are different credentials required to create those resources. However, CDK does not understand natively how to get credentials for those different accounts or when to swap between the different credentials. One way to fix this is to use cdk-assume-role-credential-plugin, which will allow you to use a single CDK deploy command to deploy to many different accounts.
I wrote a detailed tutorial here: https://johntipper.org/aws-cdk-cross-account-deployments-with-cdk-pipelines-and-cdk-assume-role-credential-plugin/