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psa_generate_derived_key_internal, psa_generate_derived_ecc_key_weierstrass_helper: optimize the code

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Perform the following optimizations:
- fix used flags for conditional compilation
- remove redundant N variable
- move loop used to generate valid k value to helper function
- fix initial value of status
- fix comments

Signed-off-by: Przemyslaw Stekiel <przemyslaw.stekiel@mobica.com>
This commit is contained in:
Przemyslaw Stekiel 2022-01-20 22:41:17 +01:00
parent 924815982a
commit 6d3d18b2dc
2 changed files with 51 additions and 50 deletions
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3
include/psa/crypto_values.h
View File

@ -553,6 +553,9 @@
((type) & PSA_KEY_TYPE_ECC_CURVE_MASK) : \
0))
/** Check if the curve of given family is Weierstrass elliptic curve. */
#define PSA_ECC_FAMILY_IS_WEIERSTRASS(family) ((family & 0xc0) == 0)
/** SEC Koblitz curves over prime fields.
*
* This family comprises the following curves:

98
library/psa_crypto.c
View File

@ -4853,25 +4853,24 @@ static void psa_des_set_key_parity( uint8_t *data, size_t data_size )
*/
#if defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_ECC_KEY_PAIR) || \
defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_ECC_PUBLIC_KEY) || \
defined(MBEDTLS_PSA_BUILTIN_ALG_ECDSA) || \
defined(MBEDTLS_PSA_BUILTIN_ALG_DETERMINISTIC_ECDSA) || \
defined(MBEDTLS_PSA_BUILTIN_ALG_ECDH)
defined(MBEDTLS_PSA_ACCEL_KEY_TYPE_ECC_KEY_PAIR) || \
defined(MBEDTLS_PSA_ACCEL_KEY_TYPE_ECC_PUBLIC_KEY)
static psa_status_t psa_generate_derived_ecc_key_weierstrass_helper(
psa_key_slot_t *slot,
size_t bits,
psa_key_derivation_operation_t *operation,
uint8_t **data,
unsigned *key_out_of_range)
uint8_t **data
)
{
mbedtls_mpi N;
unsigned key_out_of_range = 1;
mbedtls_mpi k;
mbedtls_mpi diff_N_2;
/* ret variable is used by MBEDTLS_MPI_CHK macro */
/* ret variable is initialized to 0 as it is
used only by MBEDTLS_MPI_CHK macro */
int ret = 0;
psa_status_t status = PSA_SUCCESS;
psa_status_t status = PSA_ERROR_GENERIC_ERROR;
mbedtls_mpi_init( &k );
mbedtls_mpi_init( &N );
mbedtls_mpi_init( &diff_N_2 );
psa_ecc_family_t curve = PSA_KEY_TYPE_ECC_GET_FAMILY(
@ -4891,47 +4890,52 @@ static psa_status_t psa_generate_derived_ecc_key_weierstrass_helper(
if( ( status = mbedtls_to_psa_error( mbedtls_ecp_group_load( &ecp_group, grp_id ) ) ) != 0 )
goto cleanup;
/* N is the boundary of the private key domain. */
MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &N, &ecp_group.N ) );
/* N is the boundary of the private key domain (ecp_group.N). */
/* Let m be the bit size of N. */
size_t m = ecp_group.nbits;
size_t m_bytes = PSA_BITS_TO_BYTES( m );
if (*data == NULL)
*data = mbedtls_calloc( 1, m_bytes );
/* Note: This function is always called with *data == NULL and it
* allocates memory for the data buffer. */
*data = mbedtls_calloc( 1, m_bytes );
if( *data == NULL )
{
status = PSA_ERROR_INSUFFICIENT_MEMORY;
goto cleanup;
}
/* 1. Draw a byte string of length ceiling(m/8) bytes. */
if ( ( status = psa_key_derivation_output_bytes( operation, *data, m_bytes ) ) != 0 )
goto cleanup;
/* 2. If m is not a multiple of 8 */
if (m % 8)
while ( key_out_of_range )
{
/* Set the most significant
* (8 * ceiling(m/8) - m) bits of the first byte in
* the string to zero.
*/
uint8_t clear_bit_mask = (1 << (m % 8)) - 1;
*data[0] &= clear_bit_mask;
/* 1. Draw a byte string of length ceiling(m/8) bytes. */
if ( ( status = psa_key_derivation_output_bytes( operation, *data, m_bytes ) ) != 0 )
goto cleanup;
/* 2. If m is not a multiple of 8 */
if (m % 8)
{
/* Set the most significant
* (8 * ceiling(m/8) - m) bits of the first byte in
* the string to zero.
*/
uint8_t clear_bit_mask = (1 << (m % 8)) - 1;
*data[0] &= clear_bit_mask;
}
/* 3. Convert the string to integer k by decoding it as a
* big-endian byte string.
*/
MBEDTLS_MPI_CHK(mbedtls_mpi_read_binary( &k, *data, m_bytes));
/* 4. If k > N - 2, discard the result and return to step 1.
* Result of comparison is returned. When it indicates error
* then this fuction is called again.
*/
MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &diff_N_2, &ecp_group.N, 2) );
MBEDTLS_MPI_CHK( mbedtls_mpi_grow( &k, diff_N_2.n ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_lt_mpi_ct( &diff_N_2, &k, &key_out_of_range ) );
}
/* 3. Convert the string to integer k by decoding it as a
* big-endian byte string.
*/
MBEDTLS_MPI_CHK(mbedtls_mpi_read_binary( &k, *data, m_bytes));
/* 4. If k > N - 2, discard the result and return to step 1.
* Result of comparison is returned. When it indicates error
* then this fuction is called again.
*/
MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( &diff_N_2, &N, 2) );
MBEDTLS_MPI_CHK( mbedtls_mpi_grow( &k, diff_N_2.n ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_lt_mpi_ct( &diff_N_2, &k, key_out_of_range ) );
/* 5. Output k + 1 as the private key. */
MBEDTLS_MPI_CHK( mbedtls_mpi_add_int( &k, &k, 1));
MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &k, *data, m_bytes) );
@ -4943,7 +4947,6 @@ cleanup:
*data = NULL;
}
mbedtls_mpi_free( &k );
mbedtls_mpi_free( &N );
mbedtls_mpi_free( &diff_N_2 );
return( status );
}
@ -4961,22 +4964,17 @@ static psa_status_t psa_generate_derived_key_internal(
#if defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_ECC_KEY_PAIR) || \
defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_ECC_PUBLIC_KEY) || \
defined(MBEDTLS_PSA_BUILTIN_ALG_ECDSA) || \
defined(MBEDTLS_PSA_BUILTIN_ALG_DETERMINISTIC_ECDSA) || \
defined(MBEDTLS_PSA_BUILTIN_ALG_ECDH)
defined(MBEDTLS_PSA_ACCEL_KEY_TYPE_ECC_KEY_PAIR) || \
defined(MBEDTLS_PSA_ACCEL_KEY_TYPE_ECC_PUBLIC_KEY)
if ( PSA_KEY_TYPE_IS_ECC( slot->attr.type ) )
{
psa_ecc_family_t curve = PSA_KEY_TYPE_ECC_GET_FAMILY( slot->attr.type );
if ( curve != PSA_ECC_FAMILY_MONTGOMERY )
if ( PSA_ECC_FAMILY_IS_WEIERSTRASS( curve ) )
{
/* Weierstrass elliptic curve */
unsigned key_out_of_range = 0;
do
{
status = psa_generate_derived_ecc_key_weierstrass_helper(slot, bits, operation, &data, &key_out_of_range);
if( status != PSA_SUCCESS )
goto exit;
} while ( key_out_of_range );
status = psa_generate_derived_ecc_key_weierstrass_helper(slot, bits, operation, &data);
if( status != PSA_SUCCESS )
goto exit;
}
else
{
@ -5016,7 +5014,7 @@ static psa_status_t psa_generate_derived_key_internal(
data[55] |= 128;
break;
default:
/* already handled */
/* should never happen */
break;
}
}