boot/cypress/MCUBootApp/image_ec256_mbedtls.c

/*
 * Licensed to the Apache Software Foundation (ASF) under one
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 * distributed with this work for additional information
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 * to you under the Apache License, Version 2.0 (the
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 *
 *  http://www.apache.org/licenses/LICENSE-2.0
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 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

/*******************************************************************************
* \copyright
*
* (c) 2019, Cypress Semiconductor Corporation
* or a subsidiary of Cypress Semiconductor Corporation. All rights
* reserved.
*
* This software is a port of the open source MCUBoot project.
*
* This file was modified to fit PSoC6-based MCUBoot applications.
*
* Portions of this software, including source code, documentation and related
* materials ("Software"), are owned by Cypress Semiconductor
* Corporation or one of its subsidiaries ("Cypress") and is protected by
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* United States copyright laws and international treaty provisions.
* Therefore, you may use this Software only as provided in the license
* agreement accompanying the software package from which you
* obtained this Software ("EULA").
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* If no EULA applies, Cypress hereby grants you a personal, non-
* exclusive, non-transferable license to copy, modify, and compile the
* Software source code solely for use in connection with Cypress's
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* above is prohibited without the express written permission of Cypress.
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********************************************************************************/

#include "mcuboot_config/mcuboot_config.h"

#ifdef MCUBOOT_SIGN_EC256

#include "bootutil/sign_key.h"

#ifdef MCUBOOT_USE_MBED_TLS

#include "mbedtls/oid.h"
#include "mbedtls/asn1.h"
#include "mbedtls/ecdsa.h"

#include "bootutil_priv.h"

#include <string.h>

/*
 * Declaring these like this adds NULL termination.
 */
static const uint8_t ec_pubkey_oid[] = MBEDTLS_OID_EC_ALG_UNRESTRICTED;
static const uint8_t ec_secp256r1_oid[] = MBEDTLS_OID_EC_GRP_SECP256R1;

/*
 * Parse the public key used for signing.
 */
static int
bootutil_parse_eckey(mbedtls_ecdsa_context *ctx, uint8_t **p, uint8_t *end)
{
    size_t len;
    mbedtls_asn1_buf alg;
    mbedtls_asn1_buf param;

    if (mbedtls_asn1_get_tag(p, end, &len,
        MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE)) {
        return -1;
    }
    end = *p + len;

    if (mbedtls_asn1_get_alg(p, end, &alg, &param)) {
        return -2;
    }
    if (alg.len != sizeof(ec_pubkey_oid) - 1 ||
      memcmp(alg.p, ec_pubkey_oid, sizeof(ec_pubkey_oid) - 1)) {
        return -3;
    }
    if (param.len != sizeof(ec_secp256r1_oid) - 1||
      memcmp(param.p, ec_secp256r1_oid, sizeof(ec_secp256r1_oid) - 1)) {
        return -4;
    }

    if (mbedtls_ecp_group_load(&ctx->grp, MBEDTLS_ECP_DP_SECP256R1)) {
        return -5;
    }

    if (mbedtls_asn1_get_bitstring_null(p, end, &len)) {
        return -6;
    }
    if (*p + len != end) {
        return -7;
    }

    if (mbedtls_ecp_point_read_binary(&ctx->grp, &ctx->Q, *p, end - *p)) {
        return -8;
    }

    if (mbedtls_ecp_check_pubkey(&ctx->grp, &ctx->Q)) {
        return -9;
    }
    return 0;
}

int
bootutil_verify_sig(uint8_t *hash, uint32_t hlen, uint8_t *sig, size_t slen, uint8_t key_id)
{
    int rc;
    uint8_t *cp;
    uint8_t *end;
    mbedtls_ecdsa_context ctx;

    mbedtls_ecdsa_init(&ctx);

    cp = (uint8_t *)bootutil_keys[key_id].key;
    end = cp + *bootutil_keys[key_id].len;

    rc = bootutil_parse_eckey(&ctx, &cp, end);
    if (rc) {
        return -1;
    }

    while (sig[slen - 1] == '\0') {
        slen--;
    }

    rc = mbedtls_ecdsa_read_signature(&ctx, hash, hlen, sig, slen);

    mbedtls_ecdsa_free(&ctx);

    return rc;
}

#endif /* MCUBOOT_USE_MBED_TLS */

#endif /* MCUBOOT_SIGN_EC256 */