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Split off psa_key_derivation_internal

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Refactor psa_key_derivation to prepare for key agreement algorithms
which need to plug into key derivation after argument validation.
This commit is contained in:
Gilles Peskine 2018-09-18 12:03:52 +02:00
parent 93098fd996
commit cce18aec4c
1 changed files with 65 additions and 35 deletions
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100
library/psa_crypto.c
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@ -3432,7 +3432,8 @@ exit:
/* Set up an HKDF-based generator. This is exactly the extract phase
* of the HKDF algorithm. */
static psa_status_t psa_generator_hkdf_setup( psa_hkdf_generator_t *hkdf,
key_slot_t *slot,
const uint8_t *secret,
size_t secret_length,
psa_algorithm_t hash_alg,
const uint8_t *salt,
size_t salt_length,
@ -3445,9 +3446,7 @@ static psa_status_t psa_generator_hkdf_setup( psa_hkdf_generator_t *hkdf,
PSA_ALG_HMAC_GET_HASH( hash_alg ) );
if( status != PSA_SUCCESS )
return( status );
status = psa_hash_update( &hkdf->hmac.hash_ctx,
slot->data.raw.data,
slot->data.raw.bytes );
status = psa_hash_update( &hkdf->hmac.hash_ctx, secret, secret_length );
if( status != PSA_SUCCESS )
return( status );
status = psa_hmac_finish_internal( &hkdf->hmac,
@ -3468,6 +3467,51 @@ static psa_status_t psa_generator_hkdf_setup( psa_hkdf_generator_t *hkdf,
return( PSA_SUCCESS );
}
static psa_status_t psa_key_derivation_internal(
psa_crypto_generator_t *generator,
const uint8_t *secret, size_t secret_length,
psa_algorithm_t alg,
const uint8_t *salt, size_t salt_length,
const uint8_t *label, size_t label_length,
size_t capacity )
{
psa_status_t status;
size_t max_capacity;
/* Set generator->alg even on failure so that abort knows what to do. */
generator->alg = alg;
#if defined(MBEDTLS_MD_C)
if( PSA_ALG_IS_HKDF( alg ) )
{
psa_algorithm_t hash_alg = PSA_ALG_HKDF_GET_HASH( alg );
size_t hash_size = PSA_HASH_SIZE( hash_alg );
if( hash_size == 0 )
return( PSA_ERROR_NOT_SUPPORTED );
max_capacity = 255 * hash_size;
status = psa_generator_hkdf_setup( &generator->ctx.hkdf,
secret, secret_length,
hash_alg,
salt, salt_length,
label, label_length );
}
else
#endif
{
return( PSA_ERROR_NOT_SUPPORTED );
}
if( status != PSA_SUCCESS )
return( status );
if( capacity <= max_capacity )
generator->capacity = capacity;
else
return( PSA_ERROR_INVALID_ARGUMENT );
return( PSA_SUCCESS );
}
psa_status_t psa_key_derivation( psa_crypto_generator_t *generator,
psa_key_slot_t key,
psa_algorithm_t alg,
@ -3483,41 +3527,27 @@ psa_status_t psa_key_derivation( psa_crypto_generator_t *generator,
if( generator->alg != 0 )
return( PSA_ERROR_BAD_STATE );
status = psa_get_key_from_slot( key, &slot, PSA_KEY_USAGE_DERIVE, alg );
if( status != PSA_SUCCESS )
return( status );
if( slot->type != PSA_KEY_TYPE_DERIVE )
return( PSA_ERROR_INVALID_ARGUMENT );
/* Make sure that alg is a key derivation algorithm. This prevents
* key selection algorithms, which psa_key_derivation_internal
* accepts for the sake of key agreement. */
if( ! PSA_ALG_IS_KEY_DERIVATION( alg ) )
return( PSA_ERROR_INVALID_ARGUMENT );
#if defined(MBEDTLS_MD_C)
if( PSA_ALG_IS_HKDF( alg ) )
{
psa_algorithm_t hash_alg = PSA_ALG_HKDF_GET_HASH( alg );
size_t hash_size = PSA_HASH_SIZE( hash_alg );
if( hash_size == 0 )
return( PSA_ERROR_NOT_SUPPORTED );
if( capacity > 255 * hash_size )
return( PSA_ERROR_INVALID_ARGUMENT );
status = psa_generator_hkdf_setup( &generator->ctx.hkdf,
slot,
hash_alg,
salt, salt_length,
label, label_length );
}
else
#endif
{
return( PSA_ERROR_NOT_SUPPORTED );
}
status = psa_get_key_from_slot( key, &slot, PSA_KEY_USAGE_DERIVE, alg );
if( status != PSA_SUCCESS )
return( status );
/* Set generator->alg even on failure so that abort knows what to do. */
generator->alg = alg;
if( status == PSA_SUCCESS )
generator->capacity = capacity;
else
if( slot->type != PSA_KEY_TYPE_DERIVE )
return( PSA_ERROR_INVALID_ARGUMENT );
status = psa_key_derivation_internal( generator,
slot->data.raw.data,
slot->data.raw.bytes,
alg,
salt, salt_length,
label, label_length,
capacity );
if( status != PSA_SUCCESS )
psa_generator_abort( generator );
return( status );
}