Using cryptographic attestation with Amazon KMS
This section explains how to set up attestation to work with Amazon Key Management Service. Amazon KMS integrates with Nitro Enclaves to provide built-in attestation support.
Secret data preparation
Before using Nitro Enclaves with Amazon KMS, it is important that you encrypt your sensitive data before sending it to the parent instance or the enclave. This section provides an overview of the steps needed to prepare your sensitive data for processing inside the enclave.
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Create a Amazon KMS key. For more information, see Creating Keys in the Amazon Key Management Service Developer Guide.
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Generate a plaintext and encrypted data key using the KMS key. For more information, see generate-data-key in the Amazon KMS Amazon CLI Command Reference.
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Encrypt the secret data under the KMS key using the plaintext data key and a client-side cryptographic library, such as the Amazon Encryption SDK. For more information, see Encrypt data with a data key in the Amazon Key Management Service Developer Guide. You must modify the KMS key policy to grant the IAM principal that you’re using in your client permission to call the GenerateDataKey API action.
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Upload the encrypted secret data and the encrypted data key to a storage location, such as Amazon S3. If you’re using the Amazon Encryption SDK, the encrypted data key is automatically included in the header of the encrypted message.
KMS key preparation
After you have created your KMS key and you have encrypted your sensitive data under it, you need to ensure that only the enclave can access it to decrypt the encrypted data.
Amazon KMS enables you to create KMS key policies with condition keys that are based on an enclave's measurements. For more information about using condition keys in KMS key policies, see Amazon KMS condition keys for Amazon Nitro Enclaves in the Amazon Key Management Service Developer Guide.
The Nitro Enclaves SDK includes some APIs (kms-decrypt,
kms-generate-data-key, and kms-generate-random) that
integrate with Amazon KMS. When these APIs are called against a specific key, the
enclave's attestation document, which includes its measurements, is attached to the
request. Amazon KMS receives the request and validates the measurements in the provided
attestation document against the measurements specified in the condition keys of the
KMS key policy. It uses this information to determine whether the enclave should be
granted permission to perform the requested action using the requested KMS key.
To prepare Amazon KMS for attestation you must have the enclave's measurements. When you have the measurements, you can create a KMS key policy that includes condition keys that are based on those measurements.
Amazon KMS provides kms:RecipientAttestation:ImageSha384 and
kms:RecipientAttestation:PCR condition keys that enable you to create
attestation-based condition keys for KMS key policies. These policies ensure that Amazon KMS only allows operations using the
KMS key if the enclave provides a signed attestation document that contains measurements that match
the measurements specified in the KMS key policy's condition keys. For more information about the condition keys,
see
kms:RecipientAttestation:ImageSha384 and kms:RecipientAttestation:PCR
in the Amazon Key Management Service Developer Guide.
For example, the following KMS key policy allows enclaves running on instances that have the
data-processing instance profile to use the KMS key for the
Decrypt, GenerateDataKey, and
GenerateRandom actions. The condition key allows the operation only
when measurements in the attestation document in the request matches the
measurements in the condition. If the request doesn't include an attestation
document, the role doesn't have permission to call the operation because this
condition cannot be satisfied.