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Implement mbedtls_cipher_setkey() for PSA-based cipher contexts

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This commit implements the internal key slot management performed
by PSA-based cipher contexts. Specifically, `mbedtls_cipher_setkey()`
wraps the provided raw key material into a key slot, and
`mbedtls_cipher_free()` destroys that key slot.
This commit is contained in:
Hanno Becker 2018-11-12 11:59:30 +00:00
parent 6118e43d15
commit edda8b8830
2 changed files with 75 additions and 7 deletions
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1
include/mbedtls/cipher_internal.h
View file

@ -121,6 +121,7 @@ typedef struct
#if defined(MBEDTLS_USE_PSA_CRYPTO)
typedef struct
{
psa_algorithm_t alg;
psa_key_slot_t slot;
unsigned char slot_state; /*!< 0: The slot is unset.
* 1: The slot is set and we own it.

81
library/cipher.c
View file

@ -60,6 +60,7 @@
#if defined(MBEDTLS_USE_PSA_CRYPTO)
#include "psa/crypto.h"
#include "mbedtls/psa_util.h"
#endif /* MBEDTLS_USE_PSA_CRYPTO */
#if defined(MBEDTLS_PLATFORM_C)
@ -176,7 +177,8 @@ void mbedtls_cipher_free( mbedtls_cipher_context_t *ctx )
if( cipher_psa->slot_state == 1 )
{
/* TODO: Destroy PSA key */
/* xxx_free() doesn't allow to return failures. */
(void) psa_destroy_key( cipher_psa->slot );
}
mbedtls_platform_zeroize( cipher_psa, sizeof( *cipher_psa ) );
@ -234,15 +236,23 @@ int mbedtls_cipher_setup( mbedtls_cipher_context_t *ctx,
int mbedtls_cipher_setup_psa( mbedtls_cipher_context_t *ctx,
const mbedtls_cipher_info_t *cipher_info )
{
psa_algorithm_t alg;
mbedtls_cipher_context_psa *cipher_psa;
if( NULL == cipher_info || NULL == ctx )
return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
ctx->cipher_ctx = mbedtls_calloc( 1, sizeof(mbedtls_cipher_context_psa ) );
if( ctx->cipher_ctx == NULL )
return( MBEDTLS_ERR_CIPHER_ALLOC_FAILED );
alg = mbedtls_psa_translate_cipher_mode( cipher_info->mode );
if( alg == 0)
return( MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE );
memset( ctx, 0, sizeof( mbedtls_cipher_context_t ) );
cipher_psa = mbedtls_calloc( 1, sizeof(mbedtls_cipher_context_psa ) );
if( cipher_psa == NULL )
return( MBEDTLS_ERR_CIPHER_ALLOC_FAILED );
cipher_psa->alg = alg;
ctx->cipher_ctx = cipher_psa;
ctx->cipher_info = cipher_info;
ctx->psa_enabled = 1;
return( 0 );
@ -254,14 +264,71 @@ int mbedtls_cipher_setkey( mbedtls_cipher_context_t *ctx,
int key_bitlen,
const mbedtls_operation_t operation )
{
if( NULL == ctx || NULL == ctx->cipher_info )
if( NULL == ctx || NULL == ctx->cipher_info ||
NULL == ctx->cipher_ctx )
{
return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
}
if( operation != MBEDTLS_DECRYPT &&
operation != MBEDTLS_ENCRYPT )
{
return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
}
#if defined(MBEDTLS_USE_PSA_CRYPTO)
if( ctx->psa_enabled == 1 )
{
/* TODO: Allocate and setup PSA key slot from raw key material. */
return( MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE );
mbedtls_cipher_context_psa * const cipher_psa =
(mbedtls_cipher_context_psa *) ctx->cipher_ctx;
size_t const key_bytelen = ( (size_t) key_bitlen + 7 ) / 8;
psa_status_t status;
psa_key_type_t key_type;
psa_key_usage_t key_usage;
psa_key_policy_t key_policy;
/* PSA Crypto API only accepts byte-aligned keys. */
if( key_bitlen % 8 != 0 )
return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
/* Don't allow keys to be set multiple times. */
if( cipher_psa->slot_state != 0 )
return( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
/* Find a fresh key slot to use. */
status = mbedtls_psa_get_free_key_slot( &cipher_psa->slot );
if( status != PSA_SUCCESS )
return( MBEDTLS_ERR_CIPHER_HW_ACCEL_FAILED );
cipher_psa->slot_state = 1; /* Indicate that we own the key slot. */
/* From that point on, the responsibility for destroying the
* key slot is on mbedtls_cipher_free(). This includes the case
* where the policy setup or key import below fail, as
* mbedtls_cipher_free() needs to be called in any case. */
/* Setup policy for the new key slot. */
psa_key_policy_init( &key_policy );
key_usage = mbedtls_psa_translate_cipher_operation( operation );
psa_key_policy_set_usage( &key_policy, key_usage, cipher_psa->alg );
status = psa_set_key_policy( cipher_psa->slot, &key_policy );
if( status != PSA_SUCCESS )
return( MBEDTLS_ERR_CIPHER_HW_ACCEL_FAILED );
/* Populate new key slot. */
key_type = mbedtls_psa_translate_cipher_type(
ctx->cipher_info->type );
if( key_type == 0 )
return( MBEDTLS_ERR_CIPHER_HW_ACCEL_FAILED );
status = psa_import_key( cipher_psa->slot,
key_type, key, key_bytelen );
if( status != PSA_SUCCESS )
return( MBEDTLS_ERR_CIPHER_HW_ACCEL_FAILED );
ctx->key_bitlen = key_bitlen;
ctx->operation = operation;
return( 0 );
}
#endif /* MBEDTLS_USE_PSA_CRYPTO */