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Update after feedback on Mbed-TLS#3492
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* Updated wording
* Split out buffer allocation to a convenience function
* Moved variable declarations to beginning of their code block

Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
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@stevew817 @shangjiaxuan
stevew817 authored and shangjiaxuan committed Aug 20, 2020
1 parent 36d1a3f commit be4b1d7
Showing 1 changed file with 58 additions and 37 deletions.
95 changes: 58 additions & 37 deletions library/psa_crypto.c
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Original file line number Diff line number Diff line change
Expand Up @@ -605,8 +605,8 @@ static psa_status_t psa_export_rsa_key( psa_key_type_t type,
pk.pk_ctx = rsa;

/* PSA Crypto API defines the format of an RSA key as a DER-encoded
* representation of respectively the non-encrypted PKCS#1 RSAPrivateKey
* or the RFC3279 RSAPublicKey for a private key or a public key. */
* representation of the non-encrypted PKCS#1 RSAPrivateKey for a
* private key and of the RFC3279 RSAPublicKey for a public key. */
if( PSA_KEY_TYPE_IS_KEY_PAIR( type ) )
ret = mbedtls_pk_write_key_der( &pk, data, data_size );
else
Expand Down Expand Up @@ -670,8 +670,10 @@ static psa_status_t psa_import_rsa_key( psa_key_slot_t *slot,
slot->attr.bits = (psa_key_bits_t) PSA_BYTES_TO_BITS(
mbedtls_rsa_get_len( &rsa ) );

/* Re-export the data to PSA export format, which in case of RSA is the
* smallest representation we can parse. */
/* Re-export the data to PSA export format, such that we can store export
* representation in the key slot. Export representation in case of RSA is
* the smallest representation that's allowed as input, so a straight-up
* allocation of the same size as the input buffer will be large enough. */
output = mbedtls_calloc( 1, data_length );

if( output == NULL )
Expand All @@ -680,11 +682,6 @@ static psa_status_t psa_import_rsa_key( psa_key_slot_t *slot,
goto exit;
}

/* PSA Crypto API defines the format of an RSA key as a DER-encoded
* representation of respectively the non-encrypted PKCS#1 RSAPrivateKey
* or the RFC3279 RSAPublicKey for a private key or a public key. That
* means we have no other choice then to run an import to verify the key
* size. */
status = psa_export_rsa_key( slot->attr.type,
&rsa,
output,
Expand Down Expand Up @@ -905,6 +902,32 @@ static inline size_t psa_get_key_slot_bits( const psa_key_slot_t *slot )
return( slot->attr.bits );
}

/** Try to allocate a buffer to an empty key slot.
*
* \param[in,out] slot Key slot to attach buffer to.
* \param[in] buffer_length Requested size of the buffer.
*
* \retval #PSA_SUCCESS
* The buffer has been successfully allocated.
* \retval #PSA_ERROR_INSUFFICIENT_MEMORY
* Not enough memory was available for allocation.
* \retval #PSA_ERROR_ALREADY_EXISTS
* Trying to allocate a buffer to a non-empty key slot.
*/
static psa_status_t psa_allocate_buffer_to_slot( psa_key_slot_t *slot,
size_t buffer_length )
{
if( slot->data.key.data != NULL )
return PSA_ERROR_ALREADY_EXISTS;

slot->data.key.data = mbedtls_calloc( 1, buffer_length );
if( slot->data.key.data == NULL )
return PSA_ERROR_INSUFFICIENT_MEMORY;

slot->data.key.bytes = buffer_length;
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. */
Expand All @@ -918,14 +941,14 @@ psa_status_t psa_import_key_into_slot( psa_key_slot_t *slot,
if( data_length == 0 )
return( PSA_ERROR_NOT_SUPPORTED );

/* Ensure that the bytes-to-bit conversion never overflows. */
if( data_length > SIZE_MAX / 8 )
return( PSA_ERROR_NOT_SUPPORTED );

if( key_type_is_raw_bytes( slot->attr.type ) )
{
size_t bit_size = PSA_BYTES_TO_BITS( data_length );

/* Ensure that the bytes-to-bits conversion hasn't overflown. */
if( data_length > SIZE_MAX / 8 )
return( PSA_ERROR_NOT_SUPPORTED );

/* Enforce a size limit, and in particular ensure that the bit
* size fits in its representation type. */
if( bit_size > PSA_MAX_KEY_BITS )
Expand All @@ -936,12 +959,9 @@ psa_status_t psa_import_key_into_slot( psa_key_slot_t *slot,
return status;

/* Allocate memory for the key */
slot->data.key.data = mbedtls_calloc( 1, data_length );
if( slot->data.key.data == NULL )
{
return( PSA_ERROR_INSUFFICIENT_MEMORY );
}
slot->data.key.bytes = data_length;
status = psa_allocate_buffer_to_slot( slot, data_length );
if( status != PSA_SUCCESS )
return status;

/* copy key into allocated buffer */
memcpy(slot->data.key.data, data, data_length);
Expand Down Expand Up @@ -1135,6 +1155,10 @@ static psa_status_t psa_get_transparent_key( psa_key_handle_t handle,
/** Wipe key data from a slot. Preserve metadata such as the policy. */
static psa_status_t psa_remove_key_data_from_memory( psa_key_slot_t *slot )
{
/* Check whether key is already clean */
if( slot->data.key.data == NULL )
return PSA_SUCCESS;

#if defined(MBEDTLS_PSA_CRYPTO_SE_C)
if( psa_key_slot_is_external( slot ) )
{
Expand Down Expand Up @@ -1958,11 +1982,12 @@ static psa_status_t psa_validate_optional_attributes(
{
mbedtls_rsa_context rsa;
mbedtls_rsa_init( &rsa, MBEDTLS_RSA_PKCS_V15, MBEDTLS_MD_NONE );
mbedtls_mpi actual, required;

psa_status_t status = psa_load_rsa_representation( slot, &rsa );
if( status != PSA_SUCCESS )
return status;
mbedtls_mpi actual, required;

int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
mbedtls_mpi_init( &actual );
mbedtls_mpi_init( &required );
Expand Down Expand Up @@ -3808,11 +3833,11 @@ psa_status_t psa_asymmetric_encrypt( psa_key_handle_t handle,
{
mbedtls_rsa_context rsa;
mbedtls_rsa_init( &rsa, MBEDTLS_RSA_PKCS_V15, MBEDTLS_MD_NONE );
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

status = psa_load_rsa_representation( slot, &rsa );
if( status != PSA_SUCCESS )
return status;
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
if( output_size < mbedtls_rsa_get_len( &rsa ) )
{
mbedtls_rsa_free( &rsa );
Expand Down Expand Up @@ -3898,11 +3923,11 @@ psa_status_t psa_asymmetric_decrypt( psa_key_handle_t handle,
{
mbedtls_rsa_context rsa;
mbedtls_rsa_init( &rsa, MBEDTLS_RSA_PKCS_V15, MBEDTLS_MD_NONE );
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

status = psa_load_rsa_representation( slot, &rsa );
if( status != PSA_SUCCESS )
return status;
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;

if( input_length != mbedtls_rsa_get_len( &rsa ) )
{
Expand Down Expand Up @@ -5773,13 +5798,9 @@ static psa_status_t psa_generate_key_internal(
return( status );

/* Allocate memory for the key */
slot->data.key.bytes = PSA_BITS_TO_BYTES( bits );
slot->data.key.data = mbedtls_calloc( 1, slot->data.key.bytes );
if( slot->data.key.data == NULL )
{
slot->data.key.bytes = 0;
return( PSA_ERROR_INSUFFICIENT_MEMORY );
}
status = psa_allocate_buffer_to_slot( slot, PSA_BITS_TO_BYTES( bits ) );
if( status != PSA_SUCCESS )
return status;

status = psa_generate_random( slot->data.key.data,
slot->data.key.bytes );
Expand Down Expand Up @@ -5825,11 +5846,11 @@ static psa_status_t psa_generate_key_internal(
/* Make sure to always have an export representation available */
size_t bytes = PSA_KEY_EXPORT_RSA_KEY_PAIR_MAX_SIZE( bits );

slot->data.key.data = mbedtls_calloc( 1, bytes );
if( slot->data.key.data == NULL )
status = psa_allocate_buffer_to_slot( slot, bytes );
if( status != PSA_SUCCESS )
{
mbedtls_rsa_free( &rsa );
return( PSA_ERROR_INSUFFICIENT_MEMORY );
return status;
}

status = psa_export_rsa_key( type,
Expand Down Expand Up @@ -5874,14 +5895,14 @@ static psa_status_t psa_generate_key_internal(

/* Make sure to always have an export representation available */
size_t bytes = PSA_BITS_TO_BYTES( bits );
slot->data.key.data = mbedtls_calloc( 1, bytes );
if( slot->data.key.data == NULL )
psa_status_t status = psa_allocate_buffer_to_slot( slot, bytes );
if( status != PSA_SUCCESS )
{
mbedtls_ecp_keypair_free( &ecp );
return( PSA_ERROR_INSUFFICIENT_MEMORY );
return status;
}
slot->data.key.bytes = bytes;
psa_status_t status = mbedtls_to_psa_error(

status = mbedtls_to_psa_error(
mbedtls_ecp_write_key( &ecp, slot->data.key.data, bytes ) );

mbedtls_ecp_keypair_free( &ecp );
Expand Down

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