312 lines
10 KiB
C
312 lines
10 KiB
C
/*
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* Driver entry points for p256-m
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*/
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/*
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* Copyright The Mbed TLS Contributors
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* SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
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*/
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#include "mbedtls/platform.h"
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#include "p256-m_driver_entrypoints.h"
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#include "p256-m/p256-m.h"
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#include "psa/crypto.h"
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#include <stddef.h>
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#include <string.h>
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#include "psa_crypto_driver_wrappers_no_static.h"
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#if defined(MBEDTLS_PSA_P256M_DRIVER_ENABLED)
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/* INFORMATION ON PSA KEY EXPORT FORMATS:
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*
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* PSA exports SECP256R1 keys in two formats:
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* 1. Keypair format: 32 byte string which is just the private key (public key
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* can be calculated from the private key)
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* 2. Public Key format: A leading byte 0x04 (indicating uncompressed format),
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* followed by the 64 byte public key. This results in a
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* total of 65 bytes.
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*
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* p256-m's internal format for private keys matches PSA. Its format for public
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* keys is only 64 bytes: the same as PSA but without the leading byte (0x04).
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* Hence, when passing public keys from PSA to p256-m, the leading byte is
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* removed.
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*
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* Shared secret and signature have the same format between PSA and p256-m.
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*/
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#define PSA_PUBKEY_SIZE 65
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#define PSA_PUBKEY_HEADER_BYTE 0x04
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#define P256_PUBKEY_SIZE 64
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#define PRIVKEY_SIZE 32
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#define SHARED_SECRET_SIZE 32
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#define SIGNATURE_SIZE 64
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#define CURVE_BITS 256
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/* Convert between p256-m and PSA error codes */
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static psa_status_t p256_to_psa_error(int ret)
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{
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switch (ret) {
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case P256_SUCCESS:
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return PSA_SUCCESS;
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case P256_INVALID_PUBKEY:
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case P256_INVALID_PRIVKEY:
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return PSA_ERROR_INVALID_ARGUMENT;
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case P256_INVALID_SIGNATURE:
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return PSA_ERROR_INVALID_SIGNATURE;
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case P256_RANDOM_FAILED:
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default:
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return PSA_ERROR_GENERIC_ERROR;
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}
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}
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psa_status_t p256_transparent_import_key(const psa_key_attributes_t *attributes,
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const uint8_t *data,
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size_t data_length,
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uint8_t *key_buffer,
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size_t key_buffer_size,
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size_t *key_buffer_length,
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size_t *bits)
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{
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/* Check the key size */
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if (*bits != 0 && *bits != CURVE_BITS) {
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return PSA_ERROR_NOT_SUPPORTED;
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}
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/* Validate the key (and its type and size) */
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psa_key_type_t type = psa_get_key_type(attributes);
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if (type == PSA_KEY_TYPE_ECC_PUBLIC_KEY(PSA_ECC_FAMILY_SECP_R1)) {
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if (data_length != PSA_PUBKEY_SIZE) {
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return *bits == 0 ? PSA_ERROR_NOT_SUPPORTED : PSA_ERROR_INVALID_ARGUMENT;
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}
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/* See INFORMATION ON PSA KEY EXPORT FORMATS near top of file */
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if (p256_validate_pubkey(data + 1) != P256_SUCCESS) {
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return PSA_ERROR_INVALID_ARGUMENT;
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}
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} else if (type == PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_SECP_R1)) {
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if (data_length != PRIVKEY_SIZE) {
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return *bits == 0 ? PSA_ERROR_NOT_SUPPORTED : PSA_ERROR_INVALID_ARGUMENT;
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}
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if (p256_validate_privkey(data) != P256_SUCCESS) {
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return PSA_ERROR_INVALID_ARGUMENT;
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}
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} else {
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return PSA_ERROR_NOT_SUPPORTED;
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}
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*bits = CURVE_BITS;
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/* We only support the export format for input, so just copy. */
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if (key_buffer_size < data_length) {
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return PSA_ERROR_BUFFER_TOO_SMALL;
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}
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memcpy(key_buffer, data, data_length);
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*key_buffer_length = data_length;
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return PSA_SUCCESS;
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}
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psa_status_t p256_transparent_export_public_key(const psa_key_attributes_t *attributes,
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const uint8_t *key_buffer,
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size_t key_buffer_size,
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uint8_t *data,
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size_t data_size,
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size_t *data_length)
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{
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/* Is this the right curve? */
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size_t bits = psa_get_key_bits(attributes);
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psa_key_type_t type = psa_get_key_type(attributes);
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if (bits != CURVE_BITS || type != PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_FAMILY_SECP_R1)) {
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return PSA_ERROR_NOT_SUPPORTED;
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}
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/* Validate sizes, as p256-m expects fixed-size buffers */
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if (key_buffer_size != PRIVKEY_SIZE) {
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return PSA_ERROR_INVALID_ARGUMENT;
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}
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if (data_size < PSA_PUBKEY_SIZE) {
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return PSA_ERROR_BUFFER_TOO_SMALL;
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}
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/* See INFORMATION ON PSA KEY EXPORT FORMATS near top of file */
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data[0] = PSA_PUBKEY_HEADER_BYTE;
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int ret = p256_public_from_private(data + 1, key_buffer);
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if (ret == P256_SUCCESS) {
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*data_length = PSA_PUBKEY_SIZE;
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}
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return p256_to_psa_error(ret);
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}
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psa_status_t p256_transparent_generate_key(
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const psa_key_attributes_t *attributes,
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uint8_t *key_buffer,
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size_t key_buffer_size,
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size_t *key_buffer_length)
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{
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/* We don't use this argument, but the specification mandates the signature
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* of driver entry-points. (void) used to avoid compiler warning. */
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(void) attributes;
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/* Validate sizes, as p256-m expects fixed-size buffers */
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if (key_buffer_size != PRIVKEY_SIZE) {
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return PSA_ERROR_BUFFER_TOO_SMALL;
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}
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/*
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* p256-m's keypair generation function outputs both public and private
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* keys. Allocate a buffer to which the public key will be written. The
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* private key will be written to key_buffer, which is passed to this
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* function as an argument. */
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uint8_t public_key_buffer[P256_PUBKEY_SIZE];
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int ret = p256_gen_keypair(key_buffer, public_key_buffer);
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if (ret == P256_SUCCESS) {
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*key_buffer_length = PRIVKEY_SIZE;
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}
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return p256_to_psa_error(ret);
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}
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psa_status_t p256_transparent_key_agreement(
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const psa_key_attributes_t *attributes,
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const uint8_t *key_buffer,
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size_t key_buffer_size,
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psa_algorithm_t alg,
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const uint8_t *peer_key,
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size_t peer_key_length,
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uint8_t *shared_secret,
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size_t shared_secret_size,
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size_t *shared_secret_length)
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{
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/* We don't use these arguments, but the specification mandates the
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* sginature of driver entry-points. (void) used to avoid compiler
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* warning. */
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(void) attributes;
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(void) alg;
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/* Validate sizes, as p256-m expects fixed-size buffers */
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if (key_buffer_size != PRIVKEY_SIZE || peer_key_length != PSA_PUBKEY_SIZE) {
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return PSA_ERROR_INVALID_ARGUMENT;
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}
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if (shared_secret_size < SHARED_SECRET_SIZE) {
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return PSA_ERROR_BUFFER_TOO_SMALL;
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}
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/* See INFORMATION ON PSA KEY EXPORT FORMATS near top of file */
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const uint8_t *peer_key_p256m = peer_key + 1;
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int ret = p256_ecdh_shared_secret(shared_secret, key_buffer, peer_key_p256m);
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if (ret == P256_SUCCESS) {
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*shared_secret_length = SHARED_SECRET_SIZE;
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}
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return p256_to_psa_error(ret);
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}
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psa_status_t p256_transparent_sign_hash(
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const psa_key_attributes_t *attributes,
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const uint8_t *key_buffer,
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size_t key_buffer_size,
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psa_algorithm_t alg,
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const uint8_t *hash,
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size_t hash_length,
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uint8_t *signature,
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size_t signature_size,
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size_t *signature_length)
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{
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/* We don't use these arguments, but the specification mandates the
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* sginature of driver entry-points. (void) used to avoid compiler
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* warning. */
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(void) attributes;
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(void) alg;
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/* Validate sizes, as p256-m expects fixed-size buffers */
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if (key_buffer_size != PRIVKEY_SIZE) {
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return PSA_ERROR_INVALID_ARGUMENT;
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}
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if (signature_size < SIGNATURE_SIZE) {
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return PSA_ERROR_BUFFER_TOO_SMALL;
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}
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int ret = p256_ecdsa_sign(signature, key_buffer, hash, hash_length);
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if (ret == P256_SUCCESS) {
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*signature_length = SIGNATURE_SIZE;
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}
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return p256_to_psa_error(ret);
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}
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/* This function expects the key buffer to contain a PSA public key,
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* as exported by psa_export_public_key() */
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static psa_status_t p256_verify_hash_with_public_key(
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const uint8_t *key_buffer,
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size_t key_buffer_size,
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const uint8_t *hash,
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size_t hash_length,
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const uint8_t *signature,
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size_t signature_length)
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{
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/* Validate sizes, as p256-m expects fixed-size buffers */
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if (key_buffer_size != PSA_PUBKEY_SIZE || *key_buffer != PSA_PUBKEY_HEADER_BYTE) {
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return PSA_ERROR_INVALID_ARGUMENT;
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}
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if (signature_length != SIGNATURE_SIZE) {
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return PSA_ERROR_INVALID_SIGNATURE;
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}
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/* See INFORMATION ON PSA KEY EXPORT FORMATS near top of file */
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const uint8_t *public_key_p256m = key_buffer + 1;
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int ret = p256_ecdsa_verify(signature, public_key_p256m, hash, hash_length);
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return p256_to_psa_error(ret);
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}
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psa_status_t p256_transparent_verify_hash(
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const psa_key_attributes_t *attributes,
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const uint8_t *key_buffer,
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size_t key_buffer_size,
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psa_algorithm_t alg,
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const uint8_t *hash,
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size_t hash_length,
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const uint8_t *signature,
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size_t signature_length)
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{
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/* We don't use this argument, but the specification mandates the signature
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* of driver entry-points. (void) used to avoid compiler warning. */
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(void) alg;
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psa_status_t status;
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uint8_t public_key_buffer[PSA_PUBKEY_SIZE];
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size_t public_key_buffer_size = PSA_PUBKEY_SIZE;
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size_t public_key_length = PSA_PUBKEY_SIZE;
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/* As p256-m doesn't require dynamic allocation, we want to avoid it in
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* the entrypoint functions as well. psa_driver_wrapper_export_public_key()
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* requires size_t*, so we use a pointer to a stack variable. */
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size_t *public_key_length_ptr = &public_key_length;
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/* The contents of key_buffer may either be the 32 byte private key
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* (keypair format), or 0x04 followed by the 64 byte public key (public
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* key format). To ensure the key is in the latter format, the public key
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* is exported. */
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status = psa_driver_wrapper_export_public_key(
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attributes,
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key_buffer,
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key_buffer_size,
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public_key_buffer,
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public_key_buffer_size,
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public_key_length_ptr);
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if (status != PSA_SUCCESS) {
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goto exit;
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}
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status = p256_verify_hash_with_public_key(
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public_key_buffer,
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public_key_buffer_size,
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hash,
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hash_length,
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signature,
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signature_length);
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exit:
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return status;
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}
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#endif /* MBEDTLS_PSA_P256M_DRIVER_ENABLED */
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