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Amazon KMS condition keys for Amazon Nitro Enclaves

Amazon Nitro Enclaves is an Amazon EC2 capability that lets you create isolated compute environments called enclaves to protect and process highly sensitive data. Amazon KMS provides condition keys to support Amazon Nitro Enclaves. These conditions keys work only when a request for an Amazon KMS operation originates in an enclave.

When you call the kms-decrypt, kms-generate-data-key, or kms-generate-random Amazon Nitro Enclaves SDK APIs from an enclave, these APIs call the corresponding Amazon KMS operation with a parameter that includes a signed attestation document from the enclave. The signed attestation document proves the enclave's identity to Amazon KMS.

The following condition keys let you limit the permissions for these operations based on the contents of the signed attestation document. Before allowing an operation, Amazon KMS compares the attestation document from the enclave to the values in these Amazon KMS condition keys.

kms:RecipientAttestation:ImageSha384

The kms:RecipientAttestation:ImageSha384 condition key allows kms-decrypt, kms-generate-data-key, and kms-generate-random requests from an enclave only when the image hash from the signed attestation document in the request matches the value in the condition key. The ImageSha384 value corresponds to PCR[0] in the attestation document. This condition key is effective only when you call the Amazon Nitro Enclaves SDK APIs from an enclave.

For example, the following key policy statement allows the data-processing role to use the KMS key for the kms-decrypt (Decrypt), kms-generate-data-key (GenerateDataKey), and kms-generate-random (GenerateRandom) operations. The kms:RecipientAttestation:ImageSha384 condition key allows the operations only when the image hash value (PCR[0]) of the attestation document in the request matches the image hash value in the condition.

If the request doesn't include any attestation document, permission is denied because this condition isn't satisfied.

{
  "Sid" : "Enable enclave data processing",
  "Effect" : "Allow",
  "Principal" : {
    "AWS" : "arn:aws:iam::111122223333:role/data-processing"
  },
  "Action": [
    "kms:Decrypt",
    "kms:GenerateDataKey",
    "kms:GenerateRandom"
  ],
  "Resource" : "*",
  "Condition": {
    "StringEqualsIgnoreCase": {
      "kms:RecipientAttestation:ImageSha384": "9fedcba8abcdef7abcdef6abcdef5abcdef4abcdef3abcdef2abcdef1abcdef1abcdef0abcdef1abcdef2abcdef3abcdef4abcdef5abcdef6abcdef7abcdef99"
    }
  }
}

kms:RecipientAttestation:PCR<PCR_ID>

The kms:RecipientAttestation:PCR<PCR_ID> condition key allows kms-decrypt, kms-generate-data-key, and kms-generate-random requests from an enclave only when the platform configuration registers (PCRs) from the signed attestation document in the request match the PCRs in the condition key. This condition key is effective only when you call the Amazon Nitro Enclaves SDK APIs from an enclave.

To specify a PCR value, use the following format. Concatenate the PCR ID to the condition key name. The PCR value must be a lower-case hexadecimal string of up to 96 bytes.

"kms:RecipientAttestation:PCRPCR_ID": "PCR_value"

For example, the following condition key specifies a particular value for PCR[1], which corresponds to the hash of the kernel used for the enclave and the bootstrap process.

kms:RecipientAttestation:PCR1: "0x1abcdef2abcdef3abcdef4abcdef5abcdef6abcdef7abcdef8abcdef9abcdef8abcdef7abcdef6abcdef5abcdef4abcdef3abcdef2abcdef1abcdef0abcde"

The following example key policy statement allows the data-processing role to use the KMS key for the kms-decrypt (Decrypt) operation.

The kms:RecipientAttestation:PCR condition key in this statement allows the operation only when the PCR1 value in the signed attestation document in the request matches kms:RecipientAttestation:PCR1 value in the condition. Use the StringEqualsIgnoreCase policy operator to require a case-insensitive comparison of the PCR values.

If the request doesn't include an attestation document, permission is denied because this condition isn't satisfied.

{
  "Sid" : "Enable enclave data processing",
  "Effect" : "Allow",
  "Principal" : {
    "AWS" : "arn:aws:iam::111122223333:role/data-processing"
  },
  "Action": "kms:Decrypt",
  "Resource" : "*",
  "Condition": {
    "StringEqualsIgnoreCase": {
      "kms:RecipientAttestation:PCR1": "0x1de4f2dcf774f6e3b679f62e5f120065b2e408dcea327bd1c9dddaea6664e7af7935581474844767453082c6f1586116376cede396a30a39a611b9aad7966c87"
    }
  }
}