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| -rw-r--r-- | include/lib/psa/delegated_attestation.h | 109 |
1 files changed, 109 insertions, 0 deletions
diff --git a/include/lib/psa/delegated_attestation.h b/include/lib/psa/delegated_attestation.h new file mode 100644 index 0000000..7aaceb3 --- /dev/null +++ b/include/lib/psa/delegated_attestation.h @@ -0,0 +1,109 @@ +/* + * Copyright (c) 2022, Arm Limited. All rights reserved. + * + * SPDX-License-Identifier: BSD-3-Clause + * + */ + +/* This file describes the Delegated Attestation API */ + +#ifndef DELEGATED_ATTESTATION_H +#define DELEGATED_ATTESTATION_H + +#include <stddef.h> +#include <stdint.h> + +#include "psa/error.h" + +/* RSS Delegated Attestation message types that distinguish its services. */ +#define RSS_DELEGATED_ATTEST_GET_DELEGATED_KEY 1001U +#define RSS_DELEGATED_ATTEST_GET_PLATFORM_TOKEN 1002U + +/** + * The aim of these APIs to get a derived signing key (private only) for the + * delegated attestation model and obtain the corresponding platform attestation + * token. In the delegated attestation model the final token consist of more + * than one subtokens which are signed by different entities. There is a + * cryptographical binding between the tokens. The derived delegated attestation + * key is bind to the platform token (details below). + * + * Expected usage model: + * - First rss_delegated_attest_get_delegated_key() API need to be called to + * obtain the private part of the delegated attestation key. The public part + * of key is computed by the cryptographic library when the key is + * registered. + * - Secondly the rss_delegated_attest_get_token() must be called to obtain + * platform attestation token. The hash of the public key (computed by + * the hash_algo indicated in the rss_delegated_attest_get_delegated_key() + * call) must be the input of this call. This ensures that nothing but the + * previously derived delegated key is bindable to the platform token. + */ + +/** + * Get a delegated attestation key (DAK). + * + * The aim of the delegated attestation key is to enable other SW components + * within the system to sign an attestation token which is different than the + * initial/platform token. The initial attestation token MUST contain the hash + * of the public delegated key to make a cryptographical binding (hash lock) + * between the key and the token. + * The initial attestation token has two roles in this scenario: + * - Attest the device boot status and security lifecycle. + * - Attest the delegated attestation key. + * The delegated attestation key is derived from a preprovisioned seed. The + * input for the key derivation is the platform boot status. The system can be + * attestated with the two tokens together. + * + * ecc_curve The type of the elliptic curve to which the requested + * attestation key belongs. Please check the note section for + * limitations. + * key_bits The size of the requested attestation key, in bits. + * key_buf Pointer to the buffer where the delegated attestation key will + * be stored. + * key_buf_size Size of allocated buffer for the key, in bytes. + * key_size Size of the key that has been returned, in bytes. + * hash_algo The hash algorithm that will be used later by the owner of the + * requested delegated key for binding it to the platform + * attestation token. + * + * Returns error code as specified in psa_status_t. + * + * Notes: + * - Currently, only the PSA_ECC_FAMILY_SECP_R1 curve type is supported. + * - The delegated attestation key must be derived before requesting for the + * platform attestation token as they are cryptographically linked together. + */ +psa_status_t +rss_delegated_attest_get_delegated_key(uint8_t ecc_curve, + uint32_t key_bits, + uint8_t *key_buf, + size_t key_buf_size, + size_t *key_size, + uint32_t hash_algo); + +/** + * Get platform attestation token + * + * dak_pub_hash Pointer to buffer where the hash of the public DAK is + * stored. + * dak_pub_hash_size Size of the hash value, in bytes. + * token_buf Pointer to the buffer where the platform attestation token + * will be stored. + * token_buf_size Size of allocated buffer for token, in bytes. + * token_size Size of the token that has been returned, in bytes. + * + * Returns error code as specified in psa_status_t. + * + * A delegated attestation key must be derived before requesting for the + * platform attestation token as they are cryptographically linked together. + * Otherwise, the token request will fail and the PSA_ERROR_INVALID_ARGUMENT + * code will be returned. + */ +psa_status_t +rss_delegated_attest_get_token(const uint8_t *dak_pub_hash, + size_t dak_pub_hash_size, + uint8_t *token_buf, + size_t token_buf_size, + size_t *token_size); + +#endif /* DELEGATED_ATTESTATION_H */ |