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Refacor code for HKDF-Extract algorithm

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Solution provided by @mpg.

Signed-off-by: Przemek Stekiel <przemyslaw.stekiel@mobica.com>
This commit is contained in:
Przemek Stekiel 2022-05-19 11:45:20 +02:00
parent 2fb0dcd403
commit 03d948c47f
1 changed files with 43 additions and 39 deletions
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82
library/psa_crypto.c
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@ -4377,8 +4377,7 @@ psa_status_t psa_key_derivation_set_capacity( psa_key_derivation_operation_t *op
} }
#if defined(MBEDTLS_PSA_BUILTIN_ALG_HKDF) #if defined(MBEDTLS_PSA_BUILTIN_ALG_HKDF)
/* Read some bytes from an HKDF-based operation. This performs a chunk /* Read some bytes from an HKDF-based operation. */
* of the expand phase of the HKDF algorithm. */
static psa_status_t psa_key_derivation_hkdf_read( psa_hkdf_key_derivation_t *hkdf, static psa_status_t psa_key_derivation_hkdf_read( psa_hkdf_key_derivation_t *hkdf,
psa_algorithm_t kdf_alg, psa_algorithm_t kdf_alg,
uint8_t *output, uint8_t *output,
@ -4388,6 +4387,7 @@ static psa_status_t psa_key_derivation_hkdf_read( psa_hkdf_key_derivation_t *hkd
uint8_t hash_length = PSA_HASH_LENGTH( hash_alg ); uint8_t hash_length = PSA_HASH_LENGTH( hash_alg );
size_t hmac_output_length; size_t hmac_output_length;
psa_status_t status; psa_status_t status;
const uint8_t last_block = PSA_ALG_IS_HKDF_EXTRACT( kdf_alg ) ? 0 : 0xff;
if( hkdf->state < HKDF_STATE_KEYED || if( hkdf->state < HKDF_STATE_KEYED ||
( ! hkdf->info_set && ! PSA_ALG_IS_HKDF_EXTRACT( kdf_alg ) ) ) ( ! hkdf->info_set && ! PSA_ALG_IS_HKDF_EXTRACT( kdf_alg ) ) )
@ -4406,57 +4406,49 @@ static psa_status_t psa_key_derivation_hkdf_read( psa_hkdf_key_derivation_t *hkd
hkdf->offset_in_block += n; hkdf->offset_in_block += n;
if( output_length == 0 ) if( output_length == 0 )
break; break;
/* We can't be wanting more output after block 0xff, otherwise /* We can't be wanting more output after the last block, otherwise
* the capacity check in psa_key_derivation_output_bytes() would have * the capacity check in psa_key_derivation_output_bytes() would have
* prevented this call. It could happen only if the operation * prevented this call. It could happen only if the operation
* object was corrupted or if this function is called directly * object was corrupted or if this function is called directly
* inside the library. */ * inside the library. */
if( hkdf->block_number == 0xff ) if( hkdf->block_number == last_block )
return( PSA_ERROR_BAD_STATE ); return( PSA_ERROR_BAD_STATE );
if( PSA_ALG_IS_HKDF_EXTRACT( kdf_alg ) && hkdf->block_number == 0 )
{
memcpy( hkdf->output_block, hkdf->prk, hash_length );
}
/* We need a new block */ /* We need a new block */
++hkdf->block_number; ++hkdf->block_number;
hkdf->offset_in_block = 0; hkdf->offset_in_block = 0;
if( ! PSA_ALG_IS_HKDF_EXTRACT( kdf_alg ) ) status = psa_key_derivation_start_hmac( &hkdf->hmac,
{ hash_alg,
status = psa_key_derivation_start_hmac( &hkdf->hmac, hkdf->prk,
hash_alg, hash_length );
hkdf->prk, if( status != PSA_SUCCESS )
hash_length ); return( status );
if( status != PSA_SUCCESS )
return( status );
if( hkdf->block_number != 1 ) if( hkdf->block_number != 1 )
{ {
status = psa_mac_update( &hkdf->hmac,
hkdf->output_block,
hash_length );
if( status != PSA_SUCCESS )
return( status );
}
status = psa_mac_update( &hkdf->hmac, status = psa_mac_update( &hkdf->hmac,
hkdf->info, hkdf->output_block,
hkdf->info_length ); hash_length );
if( status != PSA_SUCCESS )
return( status );
status = psa_mac_update( &hkdf->hmac,
&hkdf->block_number, 1 );
if( status != PSA_SUCCESS )
return( status );
status = psa_mac_sign_finish( &hkdf->hmac,
hkdf->output_block,
sizeof( hkdf->output_block ),
&hmac_output_length );
if( status != PSA_SUCCESS ) if( status != PSA_SUCCESS )
return( status ); return( status );
} }
status = psa_mac_update( &hkdf->hmac,
hkdf->info,
hkdf->info_length );
if( status != PSA_SUCCESS )
return( status );
status = psa_mac_update( &hkdf->hmac,
&hkdf->block_number, 1 );
if( status != PSA_SUCCESS )
return( status );
status = psa_mac_sign_finish( &hkdf->hmac,
hkdf->output_block,
sizeof( hkdf->output_block ),
&hmac_output_length );
if( status != PSA_SUCCESS )
return( status );
} }
return( PSA_SUCCESS ); return( PSA_SUCCESS );
@ -5235,9 +5227,21 @@ static psa_status_t psa_hkdf_input( psa_hkdf_key_derivation_t *hkdf,
return( status ); return( status );
} }
hkdf->offset_in_block = PSA_HASH_LENGTH( hash_alg );
hkdf->block_number = 0;
hkdf->state = HKDF_STATE_KEYED; hkdf->state = HKDF_STATE_KEYED;
hkdf->block_number = 0;
if( PSA_ALG_IS_HKDF_EXTRACT( kdf_alg ) )
{
/* The only block of output is the PRK. */
memcpy( hkdf->output_block, hkdf->prk, PSA_HASH_LENGTH( hash_alg ) );
hkdf->offset_in_block = 0;
}
else
{
/* Block 0 is empty, and the next block will be
* generated by psa_key_derivation_hkdf_read(). */
hkdf->offset_in_block = PSA_HASH_LENGTH( hash_alg );
}
return( PSA_SUCCESS ); return( PSA_SUCCESS );
case PSA_KEY_DERIVATION_INPUT_INFO: case PSA_KEY_DERIVATION_INPUT_INFO:
if( PSA_ALG_IS_HKDF_EXTRACT( kdf_alg ) ) if( PSA_ALG_IS_HKDF_EXTRACT( kdf_alg ) )