# AWS KMS condition keys for attested platforms AWS KMS provides condition keys to support cryptographic attestation for [AWS Nitro Enclaves](https://docs.aws.amazon.com/enclaves/latest/user/) and NitroTPM. AWS Nitro Enclaves is an Amazon EC2 capability that lets you create isolated compute environments called [enclaves](https://docs.aws.amazon.com/enclaves/latest/user/nitro-enclave-concepts.html#term-enclave) to protect and process highly sensitive data. NitroTPM extends similar attestation functionality to EC2 instances. When you call the [Decrypt](https://docs.aws.amazon.com/kms/latest/APIReference/API_Decrypt.html), [DeriveSharedSecret](https://docs.aws.amazon.com/kms/latest/APIReference/API_DeriveSharedSecret), [GenerateDataKey](https://docs.aws.amazon.com/kms/latest/APIReference/API_GenerateDataKey.html), [GenerateDataKeyPair](https://docs.aws.amazon.com/kms/latest/APIReference/API_GenerateDataKeyPair.html), or [GenerateRandom](https://docs.aws.amazon.com/kms/latest/APIReference/API_GenerateRandom.html) API operations with a signed attestation document, these APIs encrypt the plaintext in the response under the public key from the attestation document, and return ciphertext instead of plaintext. This ciphertext can be decrypted only by using the private key in the enclave. For more information, see [Cryptographic attestation support in AWS KMS](cryptographic-attestation.md). **Note** If you don't provide a key policy when you create an AWS KMS key, AWS creates one for you. This [default key policy](key-policy-default.md) grants the AWS accounts that own the KMS key full access to the key and allows the account to use IAM policies to allow access to the key. This policy allows all actions like [Decrypt](https://docs.aws.amazon.com/kms/latest/APIReference/API_Decrypt.html). AWS recommends applying principal of [Least-privilege permissions](least-privilege.md) to your KMS key policies. You can also restrict access by [modifying the KMS key policy](key-policy-modifying.md) action for `kms:*` to `[NotAction:](https://docs.aws.amazon.com/IAM/latest/UserGuide/reference_policies_elements_notaction.html)kms:Decrypt`. 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, AWS KMS compares the attestation document to the values in these AWS KMS condition keys. # Condition keys for Nitro Enclaves The following condition keys are specific to Nitro Enclaves attestation: ## kms:RecipientAttestation:ImageSha384 | AWS KMS Condition Keys | Condition Type | Value type | API Operations | Policy Type | | --- | --- | --- | --- | --- | | `kms:RecipientAttestation:ImageSha384` | String | Single-valued | `Decrypt` `DeriveSharedSecret` `GenerateDataKey` `GenerateDataKeyPair` `GenerateRandom` | Key policies and IAM policies | The `kms:RecipientAttestation:ImageSha384` condition key controls access to `Decrypt`, `DeriveSharedSecret`, `GenerateDataKey`, `GenerateDataKeyPair`, and `GenerateRandom` with a KMS key when the image digest from the signed attestation document in the request matches the value in the condition key. The `ImageSha384` value corresponds to PCR0 in the attestation document. This condition key is effective only when the `Recipient` parameter in the request specifies a signed attestation document for an AWS Nitro enclave. This value is also included in [CloudTrail events](ct-nitro-enclave.md) for requests to AWS KMS for Nitro enclaves. For example, the following key policy statement allows the `data-processing` role to use the KMS key for [Decrypt](https://docs.aws.amazon.com/kms/latest/APIReference/API_Decrypt.html), [DeriveSharedSecret](https://docs.aws.amazon.com/kms/latest/APIReference/API_DeriveSharedSecret), [GenerateDataKey](https://docs.aws.amazon.com/kms/latest/APIReference/API_GenerateDataKey.html), [GenerateDataKeyPair](https://docs.aws.amazon.com/kms/latest/APIReference/API_GenerateDataKeyPair.html), and [GenerateRandom](https://docs.aws.amazon.com/kms/latest/APIReference/API_GenerateRandom.html) operations. The `kms:RecipientAttestation:ImageSha384` condition key allows the operations only when the image digest value (PCR0) of the attestation document in the request matches the image digest value in the condition. This condition key is effective only when the `Recipient` parameter in the request specifies a signed attestation document for an AWS Nitro enclave. If the request does not include a valid attestation document from an AWS Nitro enclave, permission is denied because this condition is not satisfied. ``` { "Sid" : "Enable enclave data processing", "Effect" : "Allow", "Principal" : { "AWS" : "arn:aws:iam::111122223333:role/data-processing" }, "Action": [ "kms:Decrypt", "kms:DeriveSharedSecret", "kms:GenerateDataKey", "kms:GenerateDataKeyPair", "kms:GenerateRandom" ], "Resource" : "*", "Condition": { "StringEqualsIgnoreCase": { "kms:RecipientAttestation:ImageSha384": "9fedcba8abcdef7abcdef6abcdef5abcdef4abcdef3abcdef2abcdef1abcdef1abcdef0abcdef1abcdef2abcdef3abcdef4abcdef5abcdef6abcdef7abcdef99" } } } ``` ## kms:RecipientAttestation:PCR | AWS KMS Condition Keys | Condition Type | Value type | API Operations | Policy Type | | --- | --- | --- | --- | --- | | `kms:RecipientAttestation:PCR` | String | Single-valued | `Decrypt` `DeriveSharedSecret` `GenerateDataKey` `GenerateDataKeyPair` `GenerateRandom` | Key policies and IAM policies | The `kms:RecipientAttestation:PCR` condition key controls access to `Decrypt`, `DeriveSharedSecret`, `GenerateDataKey`, `GenerateDataKeyPair`, and `GenerateRandom` with a KMS key 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 the `Recipient` parameter in the request specifies a signed attestation document from an AWS Nitro enclave. This value is also included in [CloudTrail events](ct-nitro-enclave.md) that represent requests to AWS KMS for Nitro enclaves. To specify a PCR value, use the following format. Concatenate the PCR ID to the condition key name. You can specify a PCR ID that identifies one of the [six enclave measurements](https://docs.aws.amazon.com/enclaves/latest/user/set-up-attestation.html#where) or a custom PCR ID that you defined for a specific use case. 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 PCR1, which corresponds to the hash of the kernel used for the enclave and the bootstrap process. ``` kms:RecipientAttestation:PCR1: "abc1abcdef2abcdef3abcdef4abcdef5abcdef6abcdef7abcdef8abcdef9abcdef8abcdef7abcdef6abcdef5abcdef4abcdef3abcdef2abcdef1abcdef0abcde" ``` The following example key policy statement allows the `data-processing` role to use the KMS key for the [Decrypt](https://docs.aws.amazon.com/kms/latest/APIReference/API_Decrypt.html) 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 does not include an attestation document, permission is denied because this condition is not 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": "abc1de4f2dcf774f6e3b679f62e5f120065b2e408dcea327bd1c9dddaea6664e7af7935581474844767453082c6f1586116376cede396a30a39a611b9aad7966c87" } } } ``` # Condition keys for NitroTPM The following condition keys are specific to NitroTPM attestation: ## kms:RecipientAttestation:NitroTPMPCR | AWS KMS Condition Keys | Condition Type | Value type | API Operations | Policy Type | | --- | --- | --- | --- | --- | | `kms:RecipientAttestation:NitroTPMPCR` | String | Single-valued | `Decrypt` `DeriveSharedSecret` `GenerateDataKey` `GenerateDataKeyPair` `GenerateRandom` | Key policies and IAM policies | The `kms:RecipientAttestation:NitroTPMPCR` condition key controls access to `Decrypt`, `DeriveSharedSecret`, `GenerateDataKey`, `GenerateDataKeyPair`, and `GenerateRandom` with a KMS key 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 the `Recipient` parameter in the request specifies a signed attestation document from NitroTPM. This value is also included in [CloudTrail events](ct-nitro-tpm.md) that represent requests to AWS KMS for NitroTPM. 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:NitroTPMPCRPCR_ID": "PCR_value" ``` For example, the following condition key specifies a particular value for PCR4: ``` kms:RecipientAttestation:NitroTPMPCR4: "abc1abcdef2abcdef3abcdef4abcdef5abcdef6abcdef7abcdef8abcdef9abcdef8abcdef7abcdef6abcdef5abcdef4abcdef3abcdef2abcdef1abcdef0abcde" ``` The following example key policy statement allows the `data-processing` role to use the KMS key for the [Decrypt](https://docs.aws.amazon.com/kms/latest/APIReference/API_Decrypt.html) operation. The `kms:RecipientAttestation:NitroTPMPCR` condition key in this statement allows the operation only when the PCR4 value in the signed attestation document in the request matches `kms:RecipientAttestation:NitroTPMPCR4` value in the condition. Use the `StringEqualsIgnoreCase` policy operator to require a case-insensitive comparison of the PCR values. If the request does not include an attestation document, permission is denied because this condition is not satisfied. ``` { "Sid" : "Enable NitroTPM data processing", "Effect" : "Allow", "Principal" : { "AWS" : "arn:aws:iam::111122223333:role/data-processing" }, "Action": "kms:Decrypt", "Resource" : "*", "Condition": { "StringEqualsIgnoreCase": { "kms:RecipientAttestation:NitroTPMPCR4": "abc1de4f2dcf774f6e3b679f62e5f120065b2e408dcea327bd1c9dddaea6664e7af7935581474844767453082c6f1586116376cede396a30a39a611b9aad7966c87" } } } ```