components/service/attestation/client/psa/iat_client.c

/*
 * Copyright (c) 2021, Arm Limited and Contributors. All rights reserved.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

#include <stddef.h>
#include <string.h>
#include "iat_client.h"
#include <common/tlv/tlv.h>
#include <psa/initial_attestation.h>
#include <protocols/service/attestation/packed-c/get_token.h>
#include <protocols/service/attestation/packed-c/get_token_size.h>
#include <protocols/service/attestation/packed-c/opcodes.h>
#include <protocols/rpc/common/packed-c/status.h>

/**
 * @brief      The singleton psa_iat_client instance
 *
 * The psa attestation C API assumes a single backend service provider.  This
 * structure defines the state used by the psa_iat_client that communicates
 * with a remote provider using the provided rpc caller.
 */
static struct psa_iat_client
{
    struct rpc_caller *caller;
    int rpc_status;
} instance;


psa_status_t psa_iat_client_init(struct rpc_caller *caller)
{
	instance.caller = caller;
	instance.rpc_status = TS_RPC_CALL_ACCEPTED;

	return PSA_SUCCESS;
}

void psa_iat_client_deinit(void)
{
	instance.caller = NULL;
}

int psa_iat_client_rpc_status(void)
{
	return instance.rpc_status;
}

psa_status_t psa_initial_attest_get_token(
	const uint8_t *auth_challenge, size_t challenge_size,
    uint8_t *token_buf, size_t token_buf_size, size_t *token_size)
{
    psa_status_t psa_status = PSA_ERROR_INVALID_ARGUMENT;
    size_t req_len = tlv_required_space(challenge_size);

    if (!token_buf || !token_buf_size) return PSA_ERROR_INVALID_ARGUMENT;

    struct tlv_record challenge_record;
    challenge_record.tag = TS_ATTESTATION_GET_TOKEN_IN_TAG_AUTH_CHALLENGE;
    challenge_record.length = challenge_size;
    challenge_record.value = auth_challenge;

    rpc_call_handle call_handle;
    uint8_t *req_buf;

	*token_size = 0;

    call_handle = rpc_caller_begin(instance.caller, &req_buf, req_len);

    if (call_handle) {

        uint8_t *resp_buf;
        size_t resp_len;
        int opstatus;
        struct tlv_iterator req_iter;

        tlv_iterator_begin(&req_iter, req_buf, req_len);
        tlv_encode(&req_iter, &challenge_record);

        instance.rpc_status = rpc_caller_invoke(instance.caller, call_handle,
            TS_ATTESTATION_OPCODE_GET_TOKEN, &opstatus, &resp_buf, &resp_len);

        if (instance.rpc_status == TS_RPC_CALL_ACCEPTED) {

            psa_status = opstatus;

            if (psa_status == PSA_SUCCESS) {

                struct tlv_const_iterator resp_iter;
                struct tlv_record decoded_record;
                tlv_const_iterator_begin(&resp_iter, resp_buf, resp_len);

                if (tlv_find_decode(&resp_iter,
						TS_ATTESTATION_GET_TOKEN_OUT_TAG_TOKEN, &decoded_record)) {

                    if (decoded_record.length <= token_buf_size) {

                        memcpy(token_buf, decoded_record.value, decoded_record.length);
                        *token_size = decoded_record.length;
                    }
                    else {
                        /* Provided buffer is too small */
                        psa_status = PSA_ERROR_BUFFER_TOO_SMALL;
                    }
                }
                else {
                    /* Mandatory response parameter missing */
                    psa_status = PSA_ERROR_GENERIC_ERROR;
                }
			}
        }

        rpc_caller_end(instance.caller, call_handle);
    }

    return psa_status;
}

psa_status_t psa_initial_attest_get_token_size(
	size_t challenge_size, size_t *token_size)
{
    psa_status_t psa_status = PSA_ERROR_INVALID_ARGUMENT;
    struct ts_attestation_get_token_size_in req_msg;
    size_t req_len = sizeof(struct ts_attestation_get_token_size_in);

    *token_size = 0;  /* For failure case */

    req_msg.challenge_size = challenge_size;

    rpc_call_handle call_handle;
    uint8_t *req_buf;

    call_handle = rpc_caller_begin(instance.caller, &req_buf, req_len);

    if (call_handle) {

        uint8_t *resp_buf;
        size_t resp_len;
        int opstatus;
        struct tlv_iterator req_iter;

        memcpy(req_buf, &req_msg, req_len);

        instance.rpc_status = rpc_caller_invoke(instance.caller, call_handle,
                    TS_ATTESTATION_OPCODE_GET_TOKEN_SIZE, &opstatus, &resp_buf, &resp_len);

        if (instance.rpc_status == TS_RPC_CALL_ACCEPTED) {

            psa_status = opstatus;

            if (psa_status == PSA_SUCCESS) {

				if (resp_len >= sizeof(struct ts_attestation_get_token_size_out)) {

					struct ts_attestation_get_token_size_out resp_msg;
					memcpy(&resp_msg, resp_buf, sizeof(struct ts_attestation_get_token_size_out));
					*token_size = resp_msg.token_size;
				}
				else {
					/* Failed to decode response message */
					psa_status = PSA_ERROR_GENERIC_ERROR;
				}
            }
        }

        rpc_caller_end(instance.caller, call_handle);
    }

    return psa_status;
}