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105 lines
3.6 KiB
Markdown
105 lines
3.6 KiB
Markdown
# Key Management Service backend implementation
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This library provides an interface for the key management services used by Constellation.
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Its intended to be used for secure managing for data encryption keys and other symmetric secrets.
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## [kms](./kms/)
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A Key Management Service (KMS) is where we store our key encryption key (KEK).
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We differentiate between two cases:
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* cluster KMS (cKMS):
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The Constellation cluster itself holds the master secret (KEK) and manages key derivation.
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The KEK is generated by an admin on `constellation apply`.
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Once send to the cluster, the KEK never leaves the confidential computing context.
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As keys are only derived on demand, no DEK is ever persisted to memory by the cKMS.
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* external KMS (eKMS):
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An external KMS solution is used to hold and manage the KEK.
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DEKs are encrypted and persisted to cloud storage solutions.
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An admin is required to set up and configure the KMS before use.
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### KMS Credentials
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This section covers how credentials are used by the KMS plugins.
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#### AWS KMS
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The client requires the region the KMS is located, an access key ID, and an access key secret.
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Read the [access key documentation](https://docs.aws.amazon.com/IAM/latest/UserGuide/id_credentials_access-keys.html) for more details.
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The IAM role requires the following permissions on the key:
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* `kms:DescribeKey`
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* `kms:Encrypt`
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* `kms:Decrypt`
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#### Azure Key Vault / Azure managed HSM
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Authorization for Azure Key Vault happens through the use of manged identities.
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The managed identity used by the client needs the following permissions on the KEK:
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* `keys/get`
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* `keys/wrapKey`
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* `keys/unwrapKey`
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The client is set up using the tenant ID, client ID, and client secret tuple.
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Further, the vault type is chosen to configure whether or not the Key Vault is a managed HSM.
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### Google KMS
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Providing credentials to your application for Google's Cloud KMS happens through the usage of service accounts.
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A credentials file for the service account is used to authorize the client.
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Note that the service account used for authentication requires the following permissions:
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* `cloudkms.cryptoKeyVersions.get`
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* `cloudkms.cryptoKeyVersions.useToDecrypt`
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* `cloudkms.cryptoKeyVersions.useToEncrypt`
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## [storage](./storage/)
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Storage is where the CSI Plugin stores the encrypted DEKs.
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Supported are:
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* In-memory (used for testing only)
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* AWS S3, SSP
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* GCP GCS
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* Azure Blob
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### Storage Credentials
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Each Plugin requires credentials to authenticate itself to a CSP.
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#### AWS S3 Bucket
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For authentication an access key ID and an access key secret is used.
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As a fallback, the client may try to automatically fetch the data from the local AWS directory.
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#### Azure Blob Storage
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Authorization for Azure Blob Storage happens through the use of manged identities.
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The managed identity requires the following permissions:
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* `Microsoft.Storage/storageAccounts/blobServices/containers/write` (only if a storage container is not set up in advance)
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* `Microsoft.Storage/storageAccounts/blobServices/containers/blobs/write`
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* `Microsoft.Storage/storageAccounts/blobServices/containers/blobs/read`
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* `Microsoft.Storage/storageAccounts/blobServices/containers/blobs/add/action`
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#### Google Cloud Storage
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Providing credentials to your application for Google's Cloud Storage happens through the usage of service accounts.
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A credentials file for the service account is used to authorize the client.
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Note that the service account requires the following permissions:
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* `storage.buckets.create` (only if a bucket is not set up in advance)
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* `storage.buckets.get`
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* `storage.objects.create`
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* `storage.objects.get`
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* `storage.objects.update`
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