Concatenate AWS Secrets in aws-cdk for ECS container

Question

how do you go about making a postgres URI connection string from a Credentials.fromGeneratedSecret() call without writing the secrets out using toString()?

I think I read somewhere making a lambda that does that, but man that seems kinda overkill-ish

  const dbCreds = Credentials.fromGeneratedSecret("postgres")
  const username = dbCreds.username
  const password = dbCreds.password
  const uri = `postgresql://${username}:${password}@somerdurl/mydb?schema=public`

Pretty sure I can't do the above. However my hasura and api ECS containers need connection strings like the above, so I figure this is probably a solved thing?

user_6286627 · Answer

If you want to import a secret that already exists in the Secret's Manager you could just do a lookup of the secret by name or ARN. Take a look at the documentation referring how to get a value from AWS Secrets Manager.

Once you have your secret in the code it is easy to pass it on as an environment variable to your application. With CDK it is even possible to pass secrets from Secrets Manager or AWS Systems Manager Param Store directly onto the CDK construct. One such example would be (as pointed in the documentation):

taskDefinition.addContainer('container', {
  image: ecs.ContainerImage.fromRegistry("amazon/amazon-ecs-sample"),
  memoryLimitMiB: 1024,
  environment: { // clear text, not for sensitive data
    STAGE: 'prod',
  },
  environmentFiles: [ // list of environment files hosted either on local disk or S3
    ecs.EnvironmentFile.fromAsset('./demo-env-file.env'),
    ecs.EnvironmentFile.fromBucket(s3Bucket, 'assets/demo-env-file.env'),
  ],
  secrets: { // Retrieved from AWS Secrets Manager or AWS Systems Manager Parameter Store at container start-up.
    SECRET: ecs.Secret.fromSecretsManager(secret),
    DB_PASSWORD: ecs.Secret.fromSecretsManager(dbSecret, 'password'), // Reference a specific JSON field, (requires platform version 1.4.0 or later for Fargate tasks)
    PARAMETER: ecs.Secret.fromSsmParameter(parameter),
  }
});

Overall, in this case, you would not have to do any parsing or printing of the actual secret within the CDK. You can handle all of that processing within you application using properly set environment variables.

However, only from your question it is not clear what exactly you are trying to do. Still, the provided resources should get you in the correct direction.

Concatenate AWS Secrets in aws-cdk for ECS container

1 Answers