rancher-ecr-credentials

Rancher ECR Credentials Updater

This is a Docker container that when executed will update the Docker registry credentials in Rancher for an Amazon Elastic Container Registry.

Originally contributed by John Engelman from Object Partners.

Why is this needed?

Because access to ECR is controlled with AWS IAM. An IAM user must request a temporary credential to the registry using the AWS API. This temporary credential is then valid for 12 hours.

Rancher only supports registries that authenticate with a username and password.

How to use

In order to authenticate with AWS ECR, this Docker container uses the default chain of credential providers.

The only requirement for running this application is to specify the AWS region using the AWS_REGION environment variable.

AWS credentials are loaded using the default AWS credential chain. Credentials are loaded in the following order:

1. Assumed IAM Role specified in AWS_ROLE_ARN (The credentials used to execute the assume are determined using the following rules)
2. Environment variables (Specify AWS_ACCESS_KEY_ID, AWS_SECRET_ACCESS_KEY, AWS_REGION, and AWS_SESSION_TOKEN (optional))
3. Shared credentials file (mount a volume to /root/.aws that contains credentials and config files and specify AWS_PROFILE)
4. IAM Instance Profile (if running on EC2)

Add the following labels to the service in Rancher:

• io.rancher.container.create_agent: true
• io.rancher.container.agent.role: environment

These labels will cause Rancher to provision an API key for this service and create the CATTLE_URL, CATTLE_ACCESS_KEY, and CATTLE_SECRET_KEY environment variables.

Auto creating registry in Rancher

This tool allows for automatically defining the ECR registry in Rancher by setting the AUTO_CREATE environment variable to true. When enabled, if the updater does not find an existing registry in Rancher for the ECR URL, then it will automatically create the registry with the proper credentials. Subsequent executions of the update will simply update the credentials in Rancher per normal operation.

Configuring alternative ECR registries

By default the updater will acquire login tokens for the default registry associated with the AWS account for the credentials used to access the AWS API. This can be modified by providing the AWS_ECR_REGISTRY_IDS environment variable to the container. The variable should contain a comma (,) separated listed of account IDs to acquire tokens for. When specified, only the accounts provided will be looked up. Each account will return an authorization token that will be used to update and associated registry in Rancher.

Running container outside of Rancher

If you are running this container outside of a Rancher managed environment, then you must provide the following environment variables in additional to the ones above.

• CATTLE_URL
• CATTLE_ACCESS_KEY
• CATTLE_SECRET_KEY

$ docker run -d -e AWS_REGION=us-east-1 -e AWS_ACCESS_KEY_ID=$AWS_ACCESS_KEY_ID -e AWS_SECRET_ACCESS_KEY=$AWS_SECRET_ACCESS_KEY -e CATTLE_URL=http://rancher.mydomain.com -e CATTLE_ACCESS_KEY=$CATTLE_ACCESS_KEY -e CATTLE_SECRET_KEY=$CATTLE_SECRET_KEY objectpartners/rancher-ecr-credentials:latest

Notes

The AWS credentials must correspond to an IAM user that has permissions to call the ECR GetToken API. The application then parses the resulting response to retrieve the ECR registry URL, username, and password. The returned registry URL, is used to discover the corresponding registry in Rancher.

Rancher stores registries by environment. If multiple environments exists, one instance of this container must be run per environment. Rancher credentials are tied to an environment, so specifying them will indicate which environment to update in Rancher.

NOTE: This application runs on a 6 hour loop. It's possible there could be a slight gap where the credentials expire before this program updates them.