/vault-kube-cloud-credentials

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vault-kube-cloud-credentials

Vault Kube Cloud Credentials (lovingly VKCC - shorthand) - is an application that runs in two modes - operator and sidecar.

As an operator - it watches for Kubernetes annotations in ServiceAccounts and creates Vault objects - mapping that SA to the Cloud provider role or service account value inside the annotation.

It uses a config file to define which namespaces are allowed to map to which cloud provider roles/service accounts.

Cloud providers supported:

  • AWS
  • GCP

As a sidecar - it runs next to you application container and exposes HTTP endpoint that contains cloud provider credentials. Libraries such as AWS SDK can consume such HTTP endpoint to always have up-to-date credentials. In case if you would like to get GCP service account key file instead, the sidecar will fetch the key and make the file available to your application container.

Cloud providers supported:

  • AWS
  • GCP

Operator

Requirements

  • A Vault server with:
    • Kubernetes auth method, enabled and configured
    • AWS or GCP secrets engine, enabled and configured

Usage

./vault-kube-cloud-credentials operator -provider={aws|gcp} [-config-file=PATH_TO_CONFIG_FILE]

Refer to the example for a reference Kubernetes deployment.

Annotate your ServiceAccounts and the operator will create the corresponding login role and AWS secret role at auth/kubernetes/roles/<prefix>_aws_<namespace>_<name> and aws/role/<prefix>_aws_<namespace>_<name>
or, in case with GCP, will create a GCP static account at gcp/static-account/<prefix>_gcp_<namespace>_<name> respectively, where <prefix> is the value of prefix in the configuration file (default: vkcc).

AWS kube serviceAccount example:

apiVersion: v1
kind: ServiceAccount
metadata:
  name: foobar
  annotations:
    vault.uw.systems/aws-role: "arn:aws:iam::000000000000:role/some-role-name"
    vault.uw.systems/default-sts-ttl: "6h"

optional default-sts-ttl annotation, can be used to set custom ttl on aws token and lease time. Valid Range for this value is Minimum value of 900s, Maximum value of 43200s. this value should be lower then maxLeaseTTL of vault or max_lease_ttl on AWS backend config otherwise it will be capped at maxTTL.

if custom TTL is set then make sure max_session_duration is updated in assume Role policy for the role if required, as it defaults to 1h.

GCP service account keys and access tokens have a default TTL of 1 hour.

GCP kube serviceAccount example:

apiVersion: v1
kind: ServiceAccount
metadata:
  name: foobar
  annotations:
    vault.uw.systems/gcp-service-account: "foo@bar.iam.gserviceaccount.com"
    vault.uw.systems/gcp-token-scopes: "https://www.googleapis.com/auth/cloud-platform"

If you specify vault.uw.systems/gcp-token-scopes annotation you will receive GCP credentials in a form of access tokens. You can specify multiple scopes separated by comma. If that annotation is omitted the sidecar will fetch service account key in a form of JSON file and save that to the path specified in GOOGLE_APPLICATION_CREDENTIALS env var (/gcp/sa.json by default). vault.uw.systems/default-gcp-key-ttl annotation can be used to set initial lease ttl for the key. if this key is not renewed and expired then vault will delete key from GCP.

Config file

The operator can be configured by a yaml file passed to the operator with the flag -config-file.

If no file is provided then the defaults are used. Any omitted values revert to their defaults.

Refer to the defaultFileConfig in operator/config.go.

Rules

You can control which service accounts can assume/use which roles based on their namespace by setting rules under aws.rules and gcp.rules.

For example, the following configuration allows service accounts in kube-system and namespaces prefixed with system- to assume roles under the sysadmin/* path, roles that begin with sysadmin- or a specific org/s3-admin role in the accounts 000000000000 and 111111111111.

aws:
  rules:
    - namespacePatterns:
        - kube-system
        - system-*
      roleNamePatterns:
        - sysadmin-*
        - sysadmin/*
        - org/s3-admin
      accountIDs:
        - 000000000000
        - 111111111111

If accountIDs is omitted or empty then any account is permitted. The other two parameters are required.

The following GCP configuration allows service accounts in kube-system get access to foo@bar.iam.gserviceaccount.com GCP service account and all accounts that start with baz in bar project.

gcp:
  rules:
    - namespacePatterns:
        - kube-system
      serviceAccountEmailPatterns:
        - foo@bar.iam.gserviceaccount.com
        - baz-*@bar.iam.gserviceaccount.com

The pattern matching supports shell file name patterns.

Role names

The operator creates objects in Vault with the following name structure:

<prefix>_<provider>_<namespace>_<serviceaccount>

The <prefix> portion is defined by the -prefix flag (default: vkcc) and serves as an identifier that can be useful when you have multiple Vault instances creating resources in the same cloud provider account. The prefix used here may be included in the name of the resources, allowing you to identify which Vault instance they belong to.

Including <provider> avoids the potential for clashes in the situation where a service account requires credentials from multiple providers.

The <namespace> and <serviceaccount> parts are self-explanatory.

Sidecars

Usage

Refer to the examples for reference Kubernetes deployments.

Or manifests to use with https://github.com/utilitywarehouse/k8s-sidecar-injector at manifests/sidecar-injector

Supported providers (secret engines):

  • aws
  • gcp
# AWS
./vault-kube-cloud-credentials sidecar \
    -vault-role=<prefix>_<provider>_<namespace>_<serviceaccount>
# GCP
./vault-kube-cloud-credentials sidecar \
    -vault-static-account=<prefix>_<provider>_<namespace>_<serviceaccount> \
    -secret-type=access_token

Refer to the usage for more options:

./vault-kube-cloud-credentials -h

Additionally, you can use any of the environment variables supported by the Vault client, most applicably:

  • VAULT_ADDR: the address of the Vault server (default: https://127.0.0.1:8200)
  • VAULT_CACERT: path to a CA certificate file used to verify the Vault server's certificate

Renewal

The sidecar will retrieve new credentials after 1/3 of the current TTL has elapsed. So, if the credentials are valid for an hour then the sidecar will attempt to fetch a new set after about 20 minutes. A random jitter is applied to the refresh period to avoid tight synchronisation between multiple sidecar instances.

If the refresh fails then the sidecar will continue to make attempts at renewal, with an exponential backoff.