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Add comments to the HMAC (non-)PSA examples

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Also clean up / align the structure on existing examples.

Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
This commit is contained in:
Manuel Pégourié-Gonnard 2022-01-31 12:06:07 +01:00
parent fd1d13c8bd
commit f392a02c50
2 changed files with 130 additions and 72 deletions
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81
programs/psa/hmac_non_psa.c
View File

@ -1,8 +1,24 @@
/*
/**
* MD API multi-part HMAC demonstration.
*
* This programs computes the HMAC of two messages using the multi-part API.
*
* This is a companion to hmac_psa.c, doing the same operations with the
* legacy MD API. The goal is that comparing the two programs will help people
* migrating to the PSA Crypto API.
*
* When it comes to multi-part HMAC operations, the `mbedtls_md_context`
* serves a dual purpose (1) hold the key, and (2) save progress information
* for the current operation. With PSA those roles are held by two disinct
* objects: (1) a psa_key_id_t to hold the key, and (2) a psa_operation_t for
* multi-part progress.
*
* This program and its companion hmac_non_psa.c illustrate this by doing the
* same sequence of multi-part HMAC computation with both APIs; looking at the
* two side by side should make the differences and similarities clear.
*/
/*
* Copyright The Mbed TLS Contributors
* SPDX-License-Identifier: Apache-2.0
*
@ -19,22 +35,17 @@
* limitations under the License.
*/
/*
* When in comes to multi-part HMAC operations, the `mbedtls_md_context`
* serves a dual purpose (1) hold the key, and (2) save progress information
* for the current operation. With PSA those roles are held by two disinct
* objects: (1) a psa_key_id_t to hold the key, and (2) a psa_operation_t for
* multi-part progress.
*
* This program and its companion hmac_psa.c illustrate this by doing the
* same sequence of multi-part HMAC computation with both APIs; looking at the
* two side by side should make the differences and similarities clear.
*/
#include <stdio.h>
/* First include Mbed TLS headers to get the Mbed TLS configuration and
* platform definitions that we'll use in this program. Also include
* standard C headers for functions we'll use here. */
#include "mbedtls/build_info.h"
#include "mbedtls/md.h"
#include <stdlib.h>
#include <stdio.h>
/* If the build options we need are not enabled, compile a placeholder. */
#if !defined(MBEDTLS_MD_C)
int main( void )
{
@ -43,20 +54,22 @@ int main( void )
}
#else
#include "mbedtls/md.h"
/* The real program starts here. */
/*
* Dummy inputs for HMAC
*/
/* Dummy inputs for HMAC */
const unsigned char msg1_part1[] = { 0x01, 0x02 };
const unsigned char msg1_part2[] = { 0x03, 0x04 };
const unsigned char msg2_part1[] = { 0x05, 0x05 };
const unsigned char msg2_part2[] = { 0x06, 0x06 };
/* Dummy key material - never do this in production!
* This example program uses SHA-256, so a 32-byte key makes sense. */
const unsigned char key_bytes[32] = { 0 };
/* Buffer for the output - using SHA-256, so 32-byte output */
unsigned char out[32];
/* Print the contents of the output buffer in hex */
void print_out( const char *title )
{
printf( "%s:", title );
@ -65,13 +78,25 @@ void print_out( const char *title )
printf( "\n" );
}
#define CHK( code ) \
do { \
ret = code; \
if( ret != 0 ) \
goto exit; \
/* Run an Mbed TLS function and bail out if it fails. */
#define CHK( expr ) \
do \
{ \
ret = ( expr ); \
if( ret != 0 ) \
{ \
printf( "Error %d at line %d: %s\n", \
ret, \
__LINE__, \
#expr ); \
goto exit; \
} \
} while( 0 )
/*
* This function demonstrates computation of the HMAC of two messages using
* the multipart API.
*/
int hmac_demo(void)
{
int ret;
@ -104,10 +129,12 @@ exit:
int main(void)
{
int ret = hmac_demo();
if( ret != 0 )
printf( "ret = %d (-0x%04x)\n", ret, (unsigned) -ret );
int ret;
CHK( hmac_demo() );
exit:
return( ret == 0 ? EXIT_SUCCESS : EXIT_FAILURE );
}
#endif

121
programs/psa/hmac_psa.c
View File

@ -1,9 +1,24 @@
/*
* This is a simple example of multi-part HMAC computation using the PSA
* Crypto API. It comes with a companion program hmac_non_psa.c, which does
* the same operations with the legacy MD API. The goal is that comparing the
* two programs will help people migrating to the PSA Crypto API.
/**
* PSA API multi-part HMAC demonstration.
*
* This programs computes the HMAC of two messages using the multi-part API.
*
* It comes with a companion program hmac_non_psa.c, which does the same
* operations with the legacy MD API. The goal is that comparing the two
* programs will help people migrating to the PSA Crypto API.
*
* When it comes to multi-part HMAC operations, the `mbedtls_md_context`
* serves a dual purpose (1) hold the key, and (2) save progress information
* for the current operation. With PSA those roles are held by two disinct
* objects: (1) a psa_key_id_t to hold the key, and (2) a psa_operation_t for
* multi-part progress.
*
* This program and its companion hmac_non_psa.c illustrate this by doing the
* same sequence of multi-part HMAC computation with both APIs; looking at the
* two side by side should make the differences and similarities clear.
*/
/*
* Copyright The Mbed TLS Contributors
* SPDX-License-Identifier: Apache-2.0
*
@ -20,22 +35,17 @@
* limitations under the License.
*/
/*
* When in comes to multi-part HMAC operations, the `mbedtls_md_context`
* serves a dual purpose (1) hold the key, and (2) save progress information
* for the current operation. With PSA those roles are held by two disinct
* objects: (1) a psa_key_id_t to hold the key, and (2) a psa_operation_t for
* multi-part progress.
*
* This program and its companion hmac_non_psa.c illustrate this by doing the
* same sequence of multi-part HMAC computation with both APIs; looking at the
* two side by side should make the differences and similarities clear.
*/
#include <stdio.h>
/* First include Mbed TLS headers to get the Mbed TLS configuration and
* platform definitions that we'll use in this program. Also include
* standard C headers for functions we'll use here. */
#include "mbedtls/build_info.h"
#include "psa/crypto.h"
#include <stdlib.h>
#include <stdio.h>
/* If the build options we need are not enabled, compile a placeholder. */
#if !defined(MBEDTLS_PSA_CRYPTO_C) || \
defined(MBEDTLS_PSA_CRYPTO_KEY_ID_ENCODES_OWNER)
int main( void )
@ -46,20 +56,22 @@ int main( void )
}
#else
#include "psa/crypto.h"
/* The real program starts here. */
/*
* Dummy inputs for HMAC
*/
/* Dummy inputs for HMAC */
const unsigned char msg1_part1[] = { 0x01, 0x02 };
const unsigned char msg1_part2[] = { 0x03, 0x04 };
const unsigned char msg2_part1[] = { 0x05, 0x05 };
const unsigned char msg2_part2[] = { 0x06, 0x06 };
/* Dummy key material - never do this in production!
* This example program uses SHA-256, so a 32-byte key makes sense. */
const unsigned char key_bytes[32] = { 0 };
/* Buffer for the output - using SHA-256, so 32-byte output */
unsigned char out[32];
/* Print the contents of the output buffer in hex */
void print_out( const char *title )
{
printf( "%s:", title );
@ -68,13 +80,26 @@ void print_out( const char *title )
printf( "\n" );
}
#define CHK( code ) \
do { \
status = code; \
if( status != PSA_SUCCESS ) \
goto exit; \
} while( 0 )
/* Run a PSA function and bail out if it fails. */
#define PSA_CHECK( expr ) \
do \
{ \
status = ( expr ); \
if( status != PSA_SUCCESS ) \
{ \
printf( "Error %d at line %d: %s\n", \
(int) status, \
__LINE__, \
#expr ); \
goto exit; \
} \
} \
while( 0 )
/*
* This function demonstrates computation of the HMAC of two messages using
* the multipart API.
*/
psa_status_t hmac_demo(void)
{
psa_status_t status;
@ -86,7 +111,7 @@ psa_status_t hmac_demo(void)
psa_set_key_usage_flags( &attributes, PSA_KEY_USAGE_SIGN_MESSAGE );
psa_set_key_algorithm( &attributes, alg );
psa_set_key_type( &attributes, PSA_KEY_TYPE_HMAC );
psa_set_key_bits( &attributes, 8 * sizeof( key_bytes ) );
psa_set_key_bits( &attributes, 8 * sizeof( key_bytes ) ); // optional
status = psa_import_key( &attributes, key_bytes, sizeof( key_bytes ), &key );
if( status != PSA_SUCCESS )
@ -97,21 +122,21 @@ psa_status_t hmac_demo(void)
size_t out_len = 0;
/* compute HMAC(key, msg1_part1 | msg1_part2) */
CHK( psa_mac_sign_setup( &op, key, alg ) );
CHK( psa_mac_update( &op, msg1_part1, sizeof( msg1_part1 ) ) );
CHK( psa_mac_update( &op, msg1_part2, sizeof( msg1_part2 ) ) );
CHK( psa_mac_sign_finish( &op, out, sizeof( out ), &out_len ) );
PSA_CHECK( psa_mac_sign_setup( &op, key, alg ) );
PSA_CHECK( psa_mac_update( &op, msg1_part1, sizeof( msg1_part1 ) ) );
PSA_CHECK( psa_mac_update( &op, msg1_part2, sizeof( msg1_part2 ) ) );
PSA_CHECK( psa_mac_sign_finish( &op, out, sizeof( out ), &out_len ) );
print_out( "msg1" );
/* compute HMAC(key, msg2_part1 | msg2_part2) */
CHK( psa_mac_sign_setup( &op, key, alg ) );
CHK( psa_mac_update( &op, msg2_part1, sizeof( msg2_part1 ) ) );
CHK( psa_mac_update( &op, msg2_part2, sizeof( msg2_part2 ) ) );
CHK( psa_mac_sign_finish( &op, out, sizeof( out ), &out_len ) );
PSA_CHECK( psa_mac_sign_setup( &op, key, alg ) );
PSA_CHECK( psa_mac_update( &op, msg2_part1, sizeof( msg2_part1 ) ) );
PSA_CHECK( psa_mac_update( &op, msg2_part2, sizeof( msg2_part2 ) ) );
PSA_CHECK( psa_mac_sign_finish( &op, out, sizeof( out ), &out_len ) );
print_out( "msg2" );
exit:
psa_mac_abort( &op );
psa_mac_abort( &op ); // needed on error, harmless on success
psa_destroy_key( key );
return( status );
@ -119,13 +144,19 @@ exit:
int main(void)
{
psa_status_t status = psa_crypto_init();
if( status != PSA_SUCCESS )
printf( "psa init: %d\n", status );
psa_status_t status = PSA_SUCCESS;
status = hmac_demo();
if( status != PSA_SUCCESS )
printf( "hmac_demo: %d\n", status );
/* Initialize the PSA crypto library. */
PSA_CHECK( psa_crypto_init( ) );
/* Run the demo */
PSA_CHECK( hmac_demo() );
/* Deinitialize the PSA crypto library. */
mbedtls_psa_crypto_free( );
exit:
return( status == PSA_SUCCESS ? EXIT_SUCCESS : EXIT_FAILURE );
}
#endif