3rdparty/p256-m/p256-m_driver_entrypoints.c

#include "mbedtls/platform.h"
#include "p256-m_driver_entrypoints.h"
#include "p256-m/p256-m.h"
#include "psa/crypto.h"
#include "psa_crypto_driver_wrappers.h"

#if defined(MBEDTLS_P256M_EXAMPLE_DRIVER_ENABLED)

psa_status_t p256m_to_psa_error( int ret )
{
    switch( ret )
    {
        case P256_SUCCESS:
            return( PSA_SUCCESS );
        case P256_INVALID_PUBKEY:
        case P256_INVALID_PRIVKEY:
            return( PSA_ERROR_INVALID_ARGUMENT );
        case P256_INVALID_SIGNATURE:
            return( PSA_ERROR_INVALID_SIGNATURE );
        case P256_RANDOM_FAILED:
        default:
            return( PSA_ERROR_GENERIC_ERROR );
    }
}

psa_status_t p256m_transparent_generate_key(
    const psa_key_attributes_t *attributes,
    uint8_t *key_buffer,
    size_t key_buffer_size,
    size_t *key_buffer_length )
{
    /* We don't use this argument, but the specification mandates the signature
     * of driver entry-points. (void) used to avoid compiler warning. */
    (void) attributes;

    psa_status_t status = PSA_ERROR_NOT_SUPPORTED;

    /*
     *  p256-m generates a 32 byte private key, and expects to write to a buffer
     *   that is of that size. */
    if( key_buffer_size != 32 )
        return( status );

    /*
     *  p256-m's keypair generation function outputs both public and private
     *  keys. Allocate a buffer to which the public key will be written. The
     *  private key will be written to key_buffer, which is passed to this
     *  function as an argument. */
    uint8_t *public_key_buffer = NULL;
    public_key_buffer = mbedtls_calloc( 1, 64);
    if( public_key_buffer == NULL)
        return( PSA_ERROR_INSUFFICIENT_MEMORY );

    status = p256m_to_psa_error(
                p256_gen_keypair(key_buffer, public_key_buffer) );
    if( status == PSA_SUCCESS )
        *key_buffer_length = 32;

    /*
     *  The storage format for a SECP256R1 keypair is just the private key, so
     *  the public key does not need to be passed back to the caller. Therefore
     *  the buffer containing it can be freed. */
    free( public_key_buffer );

    return status;
}

psa_status_t p256m_transparent_key_agreement(
    const psa_key_attributes_t *attributes,
    const uint8_t *key_buffer,
    size_t key_buffer_size,
    psa_algorithm_t alg,
    const uint8_t *peer_key,
    size_t peer_key_length,
    uint8_t *shared_secret,
    size_t shared_secret_size,
    size_t *shared_secret_length )
{
    /* We don't use these arguments, but the specification mandates the
     * sginature of driver entry-points. (void) used to avoid compiler
     * warning. */
    (void) attributes;
    (void) alg;

    /*
     *  Check that private key = 32 bytes, peer public key = 65 bytes,
     *  and that the shared secret buffer is big enough. */
    psa_status_t status = PSA_ERROR_NOT_SUPPORTED;
    if( key_buffer_size != 32 || shared_secret_size < 32 ||
        peer_key_length != 65 )
        return ( status );

    status = p256m_to_psa_error(
                p256_ecdh_shared_secret(shared_secret, key_buffer, peer_key+1) );
    if( status == PSA_SUCCESS )
        *shared_secret_length = 32;

    return status;
}

psa_status_t p256m_transparent_sign_hash(
    const psa_key_attributes_t *attributes,
    const uint8_t *key_buffer,
    size_t key_buffer_size,
    psa_algorithm_t alg,
    const uint8_t *hash,
    size_t hash_length,
    uint8_t *signature,
    size_t signature_size,
    size_t *signature_length )
{
    /* We don't use these arguments, but the specification mandates the
     * sginature of driver entry-points. (void) used to avoid compiler
     * warning. */
    (void) attributes;
    (void) alg;

    psa_status_t status = PSA_ERROR_NOT_SUPPORTED;
    if( key_buffer_size != 32 || signature_size != 64)
        return( status );

    status = p256m_to_psa_error(
            p256_ecdsa_sign(signature, key_buffer, hash, hash_length) );
    if( status == PSA_SUCCESS )
        *signature_length = 64;

    return status;
}

/*  This function expects the key buffer to contain a 65 byte public key,
 *  as exported by psa_export_public_key() */
static psa_status_t p256m_verify_hash_with_public_key(
    const uint8_t *key_buffer,
    size_t key_buffer_size,
    const uint8_t *hash,
    size_t hash_length,
    const uint8_t *signature,
    size_t signature_length )
{
    psa_status_t status = PSA_ERROR_NOT_SUPPORTED;
    if( key_buffer_size != 65 || signature_length != 64 || *key_buffer != 0x04 )
        return status;

    const uint8_t *public_key_buffer = key_buffer + 1;
    status = p256m_to_psa_error(
            p256_ecdsa_verify( signature, public_key_buffer, hash, hash_length) );

    return status;
}

psa_status_t p256m_transparent_verify_hash(
    const psa_key_attributes_t *attributes,
    const uint8_t *key_buffer,
    size_t key_buffer_size,
    psa_algorithm_t alg,
    const uint8_t *hash,
    size_t hash_length,
    const uint8_t *signature,
    size_t signature_length )
{
    /* We don't use this argument, but the specification mandates the signature
     * of driver entry-points. (void) used to avoid compiler warning. */
    (void) alg;

    psa_status_t status;
    uint8_t *public_key_buffer = NULL;
    size_t public_key_buffer_size = 65;
    public_key_buffer = mbedtls_calloc( 1, public_key_buffer_size);
    if( public_key_buffer == NULL)
        return( PSA_ERROR_INSUFFICIENT_MEMORY );
    size_t *public_key_length = NULL;
    public_key_length = mbedtls_calloc( 1, sizeof(size_t) );
    if( public_key_length == NULL)
        return( PSA_ERROR_INSUFFICIENT_MEMORY );
    *public_key_length = 65;

    /*  The contents of key_buffer may either be the 32 byte private key
     *  (keypair representation), or the 65 byte public key. To ensure the
     *  latter is obtained, the public key is exported. */
    status = psa_driver_wrapper_export_public_key(
                attributes,
                key_buffer,
                key_buffer_size,
                public_key_buffer,
                public_key_buffer_size,
                public_key_length );
    if( status != PSA_SUCCESS )
        goto exit;

    status = p256m_verify_hash_with_public_key(
                public_key_buffer,
                public_key_buffer_size,
                hash,
                hash_length,
                signature,
                signature_length );

exit:
    free( public_key_buffer );
    free( public_key_length );
    return ( status );
}

#endif /* MBEDTLS_P256M_EXAMPLE_DRIVER_ENABLED */