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Implement MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG

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Implement support for MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG.

For test purposes, write an implementation that uses libc rand().

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This commit is contained in:
Gilles Peskine 2020-11-13 18:47:18 +01:00
parent 1c49f1ac46
commit 4fc21fdeb6
6 changed files with 97 additions and 5 deletions
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5
include/mbedtls/check_config.h
View file

@ -605,6 +605,11 @@
#error "MBEDTLS_PSA_INJECT_ENTROPY is not compatible with actual entropy sources"
#endif
#if defined(MBEDTLS_PSA_INJECT_ENTROPY) && \
!defined(MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG)
#error "MBEDTLS_PSA_INJECT_ENTROPY is not compatible with MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG"
#endif
#if defined(MBEDTLS_PSA_ITS_FILE_C) && \
!defined(MBEDTLS_FS_IO)
#error "MBEDTLS_PSA_ITS_FILE_C defined, but not all prerequisites"

37
library/psa_crypto.c
View file

@ -6297,6 +6297,10 @@ exit:
*/
static void mbedtls_psa_random_init( mbedtls_psa_random_context_t *rng )
{
#if defined(MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG)
memset( rng, 0, sizeof( *rng ) );
#else /* MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG */
/* Set default configuration if
* mbedtls_psa_crypto_configure_entropy_sources() hasn't been called. */
if( rng->entropy_init == NULL )
@ -6316,31 +6320,59 @@ static void mbedtls_psa_random_init( mbedtls_psa_random_context_t *rng )
#endif
mbedtls_psa_drbg_init( mbedtls_psa_random_state( rng ) );
#endif /* MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG */
}
/** Deinitialize the PSA random generator.
*/
static void mbedtls_psa_random_free( mbedtls_psa_random_context_t *rng )
{
#if defined(MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG)
memset( rng, 0, sizeof( *rng ) );
#else /* MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG */
mbedtls_psa_drbg_free( mbedtls_psa_random_state( rng ) );
rng->entropy_free( &rng->entropy );
#endif /* MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG */
}
/** Seed the PSA random generator.
*/
static psa_status_t mbedtls_psa_random_seed( mbedtls_psa_random_context_t *rng )
{
#if defined(MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG)
/* Do nothing: the external RNG seeds itself. */
(void) rng;
return( PSA_SUCCESS );
#else /* MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG */
const unsigned char drbg_seed[] = "PSA";
int ret = mbedtls_psa_drbg_seed( rng, drbg_seed, sizeof( drbg_seed ) - 1 );
return mbedtls_to_psa_error( ret );
#endif /* MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG */
}
psa_status_t psa_generate_random( uint8_t *output,
size_t output_size )
{
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
GUARD_MODULE_INITIALIZED;
#if defined(MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG)
size_t output_length = 0;
psa_status_t status = mbedtls_psa_external_get_random( &global_data.rng,
output, output_size,
&output_length );
if( status != PSA_SUCCESS )
return( status );
/* Breaking up a request into smaller chunks is currently not supported
* for the extrernal RNG interface. */
if( output_length != output_size )
return( PSA_ERROR_INSUFFICIENT_ENTROPY );
return( PSA_SUCCESS );
#else /* MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG */
int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
while( output_size > MBEDTLS_PSA_RANDOM_MAX_REQUEST )
{
ret = mbedtls_psa_get_random(
@ -6355,6 +6387,7 @@ psa_status_t psa_generate_random( uint8_t *output,
ret = mbedtls_psa_get_random( mbedtls_psa_random_state( &global_data.rng ),
output, output_size );
return( mbedtls_to_psa_error( ret ) );
#endif /* MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG */
}
#if defined(MBEDTLS_PSA_INJECT_ENTROPY)
@ -6586,6 +6619,7 @@ exit:
/* Module setup */
/****************************************************************/
#if !defined(MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG)
psa_status_t mbedtls_psa_crypto_configure_entropy_sources(
void (* entropy_init )( mbedtls_entropy_context *ctx ),
void (* entropy_free )( mbedtls_entropy_context *ctx ) )
@ -6596,6 +6630,7 @@ psa_status_t mbedtls_psa_crypto_configure_entropy_sources(
global_data.rng.entropy_free = entropy_free;
return( PSA_SUCCESS );
}
#endif /* !defined(MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG) */
void mbedtls_psa_crypto_free( void )
{

2
library/psa_crypto_invasive.h
View file

@ -38,6 +38,7 @@
#include "mbedtls/entropy.h"
#if !defined(MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG)
/** \brief Configure entropy sources.
*
* This function may only be called before a call to psa_crypto_init(),
@ -73,5 +74,6 @@
psa_status_t mbedtls_psa_crypto_configure_entropy_sources(
void (* entropy_init )( mbedtls_entropy_context *ctx ),
void (* entropy_free )( mbedtls_entropy_context *ctx ) );
#endif /* !defined(MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG) */
#endif /* PSA_CRYPTO_INVASIVE_H */

30
library/psa_crypto_random.h
View file

@ -22,6 +22,34 @@
#ifndef PSA_CRYPTO_RANDOM_H
#define PSA_CRYPTO_RANDOM_H
#if defined(MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG)
#include <string.h>
#include <mbedtls/entropy.h> // only for error codes
#include <psa/crypto.h>
typedef mbedtls_psa_external_random_context_t mbedtls_psa_random_context_t;
static inline int mbedtls_psa_get_random( void *p_rng,
unsigned char *output,
size_t output_size )
{
(void) p_rng;
psa_status_t status = psa_generate_random( output, output_size );
if( status == PSA_SUCCESS )
return( 0 );
else
return( MBEDTLS_ERR_ENTROPY_SOURCE_FAILED );
}
static inline void *mbedtls_psa_random_state( mbedtls_psa_random_context_t *rng )
{
(void) rng;
return( NULL );
}
#else /* MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG */
/* Currently, the only supported RNG is Mbed TLS's CTR_DRBG seeded with
* mbedtls_entropy_func(). */
@ -127,4 +155,6 @@ static inline int mbedtls_psa_drbg_seed(
custom, len ) );
}
#endif /* MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG */
#endif /* PSA_CRYPTO_RANDOM_H */

16
tests/src/psa_crypto_helpers.c
View file

@ -27,4 +27,20 @@
#include <psa/crypto.h>
#if defined(MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG)
#include <test/random.h>
psa_status_t mbedtls_psa_external_get_random(
mbedtls_psa_external_random_context_t *context,
uint8_t *output, size_t output_size, size_t *output_length )
{
/* This implementation is for test purposes only!
* Use the libc non-cryptographic random generator. */
(void) context;
mbedtls_test_rnd_std_rand( NULL, output, output_size );
*output_length = output_size;
return( PSA_SUCCESS );
}
#endif /* MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG */
#endif /* MBEDTLS_PSA_CRYPTO_C */

12
tests/suites/test_suite_psa_crypto_init.function
View file

@ -17,6 +17,8 @@
#include "mbedtls/ctr_drbg.h"
#define ENTROPY_NONCE_LEN MBEDTLS_CTR_DRBG_ENTROPY_NONCE_LEN
#if !defined(MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG)
typedef struct
{
size_t threshold; /* Minimum bytes to make mbedtls_entropy_func happy */
@ -118,6 +120,8 @@ static void custom_entropy_init( mbedtls_entropy_context *ctx )
MBEDTLS_ENTROPY_SOURCE_STRONG );
}
#endif /* !defined(MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG) */
/* END_HEADER */
/* BEGIN_DEPENDENCIES
@ -125,7 +129,7 @@ static void custom_entropy_init( mbedtls_entropy_context *ctx )
* END_DEPENDENCIES
*/
/* BEGIN_CASE depends_on:MBEDTLS_ENTROPY_NV_SEED */
/* BEGIN_CASE depends_on:MBEDTLS_ENTROPY_NV_SEED:!MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG */
void create_nv_seed( )
{
static unsigned char seed[ENTROPY_MIN_NV_SEED_SIZE];
@ -201,7 +205,7 @@ void validate_module_init_key_based( int count )
}
/* END_CASE */
/* BEGIN_CASE */
/* BEGIN_CASE depends_on:!MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG */
void custom_entropy_sources( int sources_arg, int expected_init_status_arg )
{
psa_status_t expected_init_status = expected_init_status_arg;
@ -222,7 +226,7 @@ exit:
}
/* END_CASE */
/* BEGIN_CASE */
/* BEGIN_CASE depends_on:!MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG */
void fake_entropy_source( int threshold,
int amount1,
int amount2,
@ -262,7 +266,7 @@ exit:
}
/* END_CASE */
/* BEGIN_CASE depends_on:MBEDTLS_ENTROPY_NV_SEED */
/* BEGIN_CASE depends_on:MBEDTLS_ENTROPY_NV_SEED:!MBEDTLS_PSA_CRYPTO_EXTERNAL_RNG */
void entropy_from_nv_seed( int seed_size_arg,
int expected_init_status_arg )
{