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Separate 'import' from 'load into slot'

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Now that there's a validate_key entry point for drivers, it becomes
much more important to separate the import action (where a key needs
to be validated) from the load action (where a key has been
previously validated, and thus re-validating it would be a waste of
time).

This also exposes why not storing the 'bits' attribute persistently
was a bad idea. The only reason there's a rather large function to
detect bit size is because loading from persistent storage requires
it.

Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
This commit is contained in:
Steven Cooreman 2020-10-23 11:37:05 +02:00
parent f7cebd4a2b
commit 3ea0ce450f
3 changed files with 263 additions and 47 deletions
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234
library/psa_crypto.c
View file

@ -739,7 +739,7 @@ static psa_status_t psa_load_ecp_representation( psa_key_type_t type,
* - The byte 0x04;
* - `x_P` as a `ceiling(m/8)`-byte string, big-endian;
* - `y_P` as a `ceiling(m/8)`-byte string, big-endian.
* So its data length is 2m+1 where n is the key size in bits.
* So its data length is 2m+1 where m is the curve size in bits.
*/
if( ( data_length & 1 ) == 0 )
return( PSA_ERROR_INVALID_ARGUMENT );
@ -982,10 +982,195 @@ psa_status_t psa_copy_key_material_into_slot( psa_key_slot_t *slot,
return( PSA_SUCCESS );
}
/** Import key data into a slot. `slot->attr.type` must have been set
* previously. This function assumes that the slot does not contain
* any key material yet. On failure, the slot content is unchanged. */
psa_status_t psa_import_key_into_slot( psa_key_slot_t *slot,
psa_status_t psa_detect_bit_size_in_slot( psa_key_slot_t *slot )
{
if( slot->attr.bits != 0 )
return( PSA_SUCCESS );
if( key_type_is_raw_bytes( slot->attr.type ) )
{
slot->attr.bits =
(psa_key_bits_t) PSA_BYTES_TO_BITS( slot->data.key.bytes );
return( PSA_SUCCESS );
}
else if( PSA_KEY_TYPE_IS_ECC( slot->attr.type ) )
{
/* Keys are stored in export format, and we are currently
* restricted to known curves, so do the reverse lookup based
* on data length. */
size_t byte_length = slot->data.key.bytes;
if( PSA_KEY_TYPE_IS_PUBLIC_KEY( slot->attr.type ) &&
PSA_KEY_TYPE_ECC_GET_FAMILY( slot->attr.type ) !=
PSA_ECC_FAMILY_MONTGOMERY )
{
/* A Weierstrass public key is represented as:
* - The byte 0x04;
* - `x_P` as a `ceiling(m/8)`-byte string, big-endian;
* - `y_P` as a `ceiling(m/8)`-byte string, big-endian.
* So its data length is 2m+1 where m is the curve size in bits.
*/
if( ( byte_length & 1 ) == 0 )
return( PSA_ERROR_BAD_STATE );
byte_length = byte_length / 2;
/* Montgomery public keys are represented in compressed format,
* meaning their curve_size is equal to the amount of input. */
/* Private keys are represented in uncompressed private random
* integer format, meaning their curve_size is equal to the
* amount of input. */
}
switch( PSA_KEY_TYPE_ECC_GET_FAMILY( slot->attr.type ) )
{
case PSA_ECC_FAMILY_SECP_R1:
switch( byte_length )
{
case PSA_BITS_TO_BYTES( 192 ):
slot->attr.bits = 192;
break;
case PSA_BITS_TO_BYTES( 224 ):
slot->attr.bits = 224;
break;
case PSA_BITS_TO_BYTES( 256 ):
slot->attr.bits = 256;
break;
case PSA_BITS_TO_BYTES( 384 ):
slot->attr.bits = 384;
break;
case PSA_BITS_TO_BYTES( 521 ):
slot->attr.bits = 521;
break;
default:
return( PSA_ERROR_BAD_STATE );
}
break;
case PSA_ECC_FAMILY_BRAINPOOL_P_R1:
switch( byte_length )
{
case PSA_BITS_TO_BYTES( 256 ):
slot->attr.bits = 256;
break;
case PSA_BITS_TO_BYTES( 384 ):
slot->attr.bits = 384;
break;
case PSA_BITS_TO_BYTES( 512 ):
slot->attr.bits = 512;
break;
default:
return( PSA_ERROR_BAD_STATE );
}
break;
case PSA_ECC_FAMILY_MONTGOMERY:
switch( byte_length )
{
case PSA_BITS_TO_BYTES( 255 ):
slot->attr.bits = 255;
break;
case PSA_BITS_TO_BYTES( 448 ):
slot->attr.bits = 448;
break;
default:
return( PSA_ERROR_BAD_STATE );
}
break;
case PSA_ECC_FAMILY_SECP_K1:
switch( byte_length )
{
case PSA_BITS_TO_BYTES( 192 ):
slot->attr.bits = 192;
break;
case PSA_BITS_TO_BYTES( 224 ):
slot->attr.bits = 224;
break;
case PSA_BITS_TO_BYTES( 256 ):
slot->attr.bits = 256;
break;
default:
return( PSA_ERROR_BAD_STATE );
}
break;
default:
return( PSA_ERROR_BAD_STATE );
}
return( PSA_SUCCESS );
}
else if( PSA_KEY_TYPE_IS_RSA( slot->attr.type ) )
{
/* There's no easy way of figuring out the RSA bit size from
* the data length of the export representation. For now, use
* the mbed TLS software implementation to figure it out. */
psa_key_attributes_t attributes = {
.core = slot->attr
};
size_t bits;
psa_status_t status = psa_driver_wrapper_validate_key(
&attributes,
slot->data.key.data,
slot->data.key.bytes,
&bits );
if( status == PSA_SUCCESS )
slot->attr.bits = (psa_key_bits_t) bits;
if( status != PSA_ERROR_NOT_SUPPORTED )
return( status );
/* If no accelerator was able to figure it out, try software. */
#if defined(MBEDTLS_RSA_C)
mbedtls_rsa_context *rsa = NULL;
/* Parse input */
status = psa_load_rsa_representation( slot->attr.type,
slot->data.key.data,
slot->data.key.bytes,
&rsa );
if( status != PSA_SUCCESS )
{
mbedtls_rsa_free( rsa );
mbedtls_free( rsa );
return( status );
}
slot->attr.bits = (psa_key_bits_t) PSA_BYTES_TO_BITS(
mbedtls_rsa_get_len( rsa ) );
mbedtls_rsa_free( rsa );
mbedtls_free( rsa );
return( PSA_SUCCESS );
#else
return( PSA_ERROR_NOT_SUPPORTED );
#endif
}
else
return( PSA_ERROR_NOT_SUPPORTED );
}
/** Import key data into a slot.
*
* `slot->type` must have been set previously.
* This function assumes that the slot does not contain any key material yet.
* On failure, the slot content is unchanged.
*
* Persistent storage is not affected.
*
* \param[in,out] slot The key slot to import data into.
* Its `type` field must have previously been set to
* the desired key type.
* It must not contain any key material yet.
* \param[in] data Buffer containing the key material to parse and import.
* \param data_length Size of \p data in bytes.
*
* \retval #PSA_SUCCESS
* \retval #PSA_ERROR_INVALID_ARGUMENT
* \retval #PSA_ERROR_NOT_SUPPORTED
* \retval #PSA_ERROR_INSUFFICIENT_MEMORY
*/
static psa_status_t psa_import_key_into_slot( psa_key_slot_t *slot,
const uint8_t *data,
size_t data_length )
{
@ -1023,7 +1208,34 @@ psa_status_t psa_import_key_into_slot( psa_key_slot_t *slot,
* caller, which may be 0 (meaning unspecified) or wrong. */
slot->attr.bits = (psa_key_bits_t) bit_size;
}
else if( PSA_KEY_TYPE_IS_ECC( slot->attr.type ) )
else if( PSA_KEY_TYPE_IS_ASYMMETRIC( slot->attr.type ) )
{
/* Try validation through accelerators first. */
bit_size = slot->attr.bits;
psa_key_attributes_t attributes = {
.core = slot->attr
};
status = psa_driver_wrapper_validate_key( &attributes,
data,
data_length,
&bit_size );
if( status == PSA_SUCCESS )
{
/* Key has been validated successfully by an accelerator.
* Copy key material into slot. */
status = psa_copy_key_material_into_slot( slot, data, data_length );
if( status != PSA_SUCCESS )
return( status );
slot->attr.bits = (psa_key_bits_t) bit_size;
return( PSA_SUCCESS );
}
else if( status != PSA_ERROR_NOT_SUPPORTED )
return( status );
/* Key format is not supported by any accelerator, try software fallback
* if present. */
if( PSA_KEY_TYPE_IS_ECC( slot->attr.type ) )
{
#if defined(MBEDTLS_ECP_C)
status = psa_import_ecp_key( slot,
@ -1031,7 +1243,7 @@ psa_status_t psa_import_key_into_slot( psa_key_slot_t *slot,
#else
/* No drivers have been implemented yet, so without mbed TLS backing
* there's no way to do ECP with the current library. */
return( PSA_ERROR_NOT_SUPPORTED );
status = PSA_ERROR_NOT_SUPPORTED;
#endif /* defined(MBEDTLS_ECP_C) */
}
else if( PSA_KEY_TYPE_IS_RSA( slot->attr.type ) )
@ -1046,9 +1258,15 @@ psa_status_t psa_import_key_into_slot( psa_key_slot_t *slot,
#endif /* defined(MBEDTLS_RSA_C) */
}
else
{
/* Unsupported asymmetric key type */
status = PSA_ERROR_NOT_SUPPORTED;
}
}
else
{
/* Unknown key type */
return( PSA_ERROR_NOT_SUPPORTED );
status = PSA_ERROR_NOT_SUPPORTED;
}
return( status );

42
library/psa_crypto_core.h
View file

@ -137,30 +137,6 @@ static inline void psa_key_slot_clear_bits( psa_key_slot_t *slot,
*/
psa_status_t psa_wipe_key_slot( psa_key_slot_t *slot );
/** Import key data into a slot.
*
* `slot->type` must have been set previously.
* This function assumes that the slot does not contain any key material yet.
* On failure, the slot content is unchanged.
*
* Persistent storage is not affected.
*
* \param[in,out] slot The key slot to import data into.
* Its `type` field must have previously been set to
* the desired key type.
* It must not contain any key material yet.
* \param[in] data Buffer containing the key material to parse and import.
* \param data_length Size of \p data in bytes.
*
* \retval PSA_SUCCESS
* \retval PSA_ERROR_INVALID_ARGUMENT
* \retval PSA_ERROR_NOT_SUPPORTED
* \retval PSA_ERROR_INSUFFICIENT_MEMORY
*/
psa_status_t psa_import_key_into_slot( psa_key_slot_t *slot,
const uint8_t *data,
size_t data_length );
/** Copy key data (in export format) into an empty key slot.
*
* This function assumes that the slot does not contain
@ -182,6 +158,24 @@ psa_status_t psa_copy_key_material_into_slot( psa_key_slot_t *slot,
const uint8_t *data,
size_t data_length );
/** Detect the key bit size for a key in a slot where bit size
* is unset.
*
* This function assumes that the slot contains key material in
* export format.
*
* \param[in,out] slot Key slot to detect and set the bit size in.
*
* \retval #PSA_SUCCESS
* The key bit size was already set, or has been detected
* and set accordingly.
* \retval #PSA_ERROR_BAD_STATE
* The size of the key material in the slot doesn't match
* with the declared key type.
* \retval #PSA_ERROR_NOT_SUPPORTED
* The key type is unknown to the implementation.
*/
psa_status_t psa_detect_bit_size_in_slot( psa_key_slot_t *slot );
/** Convert an mbed TLS error code to a PSA error code
*

6
library/psa_crypto_slot_management.c
View file

@ -141,7 +141,11 @@ static psa_status_t psa_load_persistent_key_into_slot( psa_key_slot_t *slot )
else
#endif /* MBEDTLS_PSA_CRYPTO_SE_C */
{
status = psa_import_key_into_slot( slot, key_data, key_data_length );
status = psa_copy_key_material_into_slot( slot, key_data, key_data_length );
if( status != PSA_SUCCESS )
goto exit;
status = psa_detect_bit_size_in_slot( slot );
}
exit: