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82 lines
4.1 KiB
Markdown
82 lines
4.1 KiB
Markdown
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# Components
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Constellation takes care of bootstrapping and initializing a Confidential Kubernetes cluster.
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During the lifetime of the cluster, it handles day 2 operations such as key management, remote attestation, and updates.
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These features are provided by several components:
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* The [Bootstrapper](components.md#bootstrapper) initializes a Constellation node and bootstraps the cluster
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* The [JoinService](components.md#joinservice) joins new nodes to an existing cluster
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* The [VerificationService](components.md#verificationservice) provides remote attestation functionality
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* The [Key Management Service (KMS)](components.md#kms) manages Constellation-internal keys
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* The [AccessManager](components.md#accessmanager) manages node SSH access
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The relations between components are shown in the following diagram:
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```mermaid
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flowchart LR
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subgraph admin [Admin's machine]
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A[Constellation CLI]
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end
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subgraph img [CoreOS image]
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B[CoreOS]
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C[Bootstrapper]
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end
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subgraph Kubernetes
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D[AccessManager]
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E[JoinService]
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F[KMS]
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G[VerificationService]
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end
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A -- deploys -->
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B -- starts --> C
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C -- deploys --> D
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C -- deploys --> E
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C -- deploys --> F
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C -- deploys --> G
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```
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## Bootstrapper
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The *Bootstrapper* is the first component launched after booting a Constellation node image.
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It sets up that machine as a Kubernetes node and integrates that node into the Kubernetes cluster.
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To this end, the *Bootstrapper* first downloads and [verifies](https://blog.sigstore.dev/kubernetes-signals-massive-adoption-of-sigstore-for-protecting-open-source-ecosystem-73a6757da73) the [Kubernetes components](https://kubernetes.io/docs/concepts/overview/components/) at the [configured](../reference/config.md) versions.
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The *Bootstrapper* tries to find an existing cluster and if successful, communicates with the [JoinService](components.md#joinservice) to join the node.
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Otherwise, it waits for an initialization request to create a new Kubernetes cluster.
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## JoinService
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The *JoinService* runs as [DaemonSet](https://kubernetes.io/docs/concepts/workloads/controllers/daemonset/) on each control-plane node.
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New nodes (at cluster start, or later through autoscaling) send a request to the service over [attested TLS (aTLS)](attestation.md#attested-tls-atls).
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The *JoinService* verifies the new node's certificate and attestation statement.
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If attestation is successful, the new node is supplied with an encryption key from the [*KMS*](components.md#kms) for its state disk, and a Kubernetes bootstrap token.
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```mermaid
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sequenceDiagram
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participant New node
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participant JoinService
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New node->>JoinService: aTLS handshake (server side verification)
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JoinService-->>New node: #
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New node->>+JoinService: IssueJoinTicket(DiskUUID, NodeName, IsControlPlane)
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JoinService->>+KMS: GetDataKey(DiskUUID)
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KMS-->>-JoinService: DiskEncryptionKey
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JoinService-->>-New node: DiskEncryptionKey, KubernetesJoinToken, ...
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```
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## VerificationService
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The *VerificationService* runs as DaemonSet on each node.
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It provides user-facing functionality for remote attestation during the cluster's lifetime via an endpoint for [verifying the cluster](attestation.md#cluster-attestation).
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Read more about the hardware-based [attestation feature](attestation.md) of Constellation and how to [verify](../workflows/verify.md) a cluster on the client side.
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## KMS
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The *KMS* runs as DaemonSet on each control-plane node.
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It implements the key management for the [storage encryption keys](keys.md#storage-encryption) in Constellation. These keys are used for the [state disk](images.md#state-disk) of each node and the [transparently encrypted storage](encrypted-storage.md) for Kubernetes.
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Depending on wether the [constellation-managed](keys.md#constellation-managed-key-management) or [user-managed](keys.md#user-managed-key-management) mode is used, the *KMS* holds the key encryption key (KEK) directly or calls an external service for key derivation respectively.
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## AccessManager
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The *AccessManager* runs as DaemonSet on each node.
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It manages the user's SSH access to nodes as specified in the [configuration](../reference/config.md).
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