tests/suites/test_suite_hmac_drbg.function - security/mbedtls - Rivoreo Source Code Repositories

 /* BEGIN_HEADER */
 #include "mbedtls/hmac_drbg.h"

 typedef struct
 {
     unsigned char *p;
     size_t len;
 } entropy_ctx;

 int mbedtls_entropy_func( void *data, unsigned char *buf, size_t len )
 {
     entropy_ctx *ctx = (entropy_ctx *) data;

     if( len > ctx->len )
         return( -1 );

     memcpy( buf, ctx->p, len );

     ctx->p += len;
     ctx->len -= len;

     return( 0 );
 }
 /* END_HEADER */

 /* BEGIN_DEPENDENCIES
  * depends_on:MBEDTLS_HMAC_DRBG_C
  * END_DEPENDENCIES
  */

 /* BEGIN_CASE */
 void hmac_drbg_entropy_usage( int md_alg )
 {
     unsigned char out[16];
     unsigned char buf[1024];
     const mbedtls_md_info_t *md_info;
     mbedtls_hmac_drbg_context ctx;
     entropy_ctx entropy;
     size_t last_len, i, reps = 10;

     mbedtls_hmac_drbg_init( &ctx );
     memset( buf, 0, sizeof( buf ) );
     memset( out, 0, sizeof( out ) );

     entropy.len = sizeof( buf );
     entropy.p = buf;

     md_info = mbedtls_md_info_from_type( md_alg );
     TEST_ASSERT( md_info != NULL );

     /* Init must use entropy */
     last_len = entropy.len;
     TEST_ASSERT( mbedtls_hmac_drbg_seed( &ctx, md_info, mbedtls_entropy_func, &entropy,
                                  NULL, 0 ) == 0 );
     TEST_ASSERT( entropy.len < last_len );

     /* By default, PR is off and reseed_interval is large,
      * so the next few calls should not use entropy */
     last_len = entropy.len;
     for( i = 0; i < reps; i++ )
     {
         TEST_ASSERT( mbedtls_hmac_drbg_random( &ctx, out, sizeof( out ) - 4 ) == 0 );
         TEST_ASSERT( mbedtls_hmac_drbg_random_with_add( &ctx, out, sizeof( out ) - 4,
                                                 buf, 16 ) == 0 );
     }
     TEST_ASSERT( entropy.len == last_len );

     /* While at it, make sure we didn't write past the requested length */
     TEST_ASSERT( out[sizeof( out ) - 4] == 0 );
     TEST_ASSERT( out[sizeof( out ) - 3] == 0 );
     TEST_ASSERT( out[sizeof( out ) - 2] == 0 );
     TEST_ASSERT( out[sizeof( out ) - 1] == 0 );

     /* Set reseed_interval to the number of calls done,
      * so the next call should reseed */
     mbedtls_hmac_drbg_set_reseed_interval( &ctx, 2 * reps );
     TEST_ASSERT( mbedtls_hmac_drbg_random( &ctx, out, sizeof( out ) ) == 0 );
     TEST_ASSERT( entropy.len < last_len );

     /* The new few calls should not reseed */
     last_len = entropy.len;
     for( i = 0; i < reps / 2; i++ )
     {
         TEST_ASSERT( mbedtls_hmac_drbg_random( &ctx, out, sizeof( out ) ) == 0 );
         TEST_ASSERT( mbedtls_hmac_drbg_random_with_add( &ctx, out, sizeof( out ) ,
                                                 buf, 16 ) == 0 );
     }
     TEST_ASSERT( entropy.len == last_len );

     /* Now enable PR, so the next few calls should all reseed */
     mbedtls_hmac_drbg_set_prediction_resistance( &ctx, MBEDTLS_HMAC_DRBG_PR_ON );
     TEST_ASSERT( mbedtls_hmac_drbg_random( &ctx, out, sizeof( out ) ) == 0 );
     TEST_ASSERT( entropy.len < last_len );

     /* Finally, check setting entropy_len */
     mbedtls_hmac_drbg_set_entropy_len( &ctx, 42 );
     last_len = entropy.len;
     TEST_ASSERT( mbedtls_hmac_drbg_random( &ctx, out, sizeof( out ) ) == 0 );
     TEST_ASSERT( (int) last_len - entropy.len == 42 );

     mbedtls_hmac_drbg_set_entropy_len( &ctx, 13 );
     last_len = entropy.len;
     TEST_ASSERT( mbedtls_hmac_drbg_random( &ctx, out, sizeof( out ) ) == 0 );
     TEST_ASSERT( (int) last_len - entropy.len == 13 );

 exit:
     mbedtls_hmac_drbg_free( &ctx );
 }
 /* END_CASE */

 /* BEGIN_CASE depends_on:MBEDTLS_FS_IO */
 void hmac_drbg_seed_file( int md_alg, char *path, int ret )
 {
     const mbedtls_md_info_t *md_info;
     mbedtls_hmac_drbg_context ctx;

     mbedtls_hmac_drbg_init( &ctx );

     md_info = mbedtls_md_info_from_type( md_alg );
     TEST_ASSERT( md_info != NULL );

     TEST_ASSERT( mbedtls_hmac_drbg_seed( &ctx, md_info, rnd_std_rand, NULL,
                                  NULL, 0 ) == 0 );

     TEST_ASSERT( mbedtls_hmac_drbg_write_seed_file( &ctx, path ) == ret );
     TEST_ASSERT( mbedtls_hmac_drbg_update_seed_file( &ctx, path ) == ret );

 exit:
     mbedtls_hmac_drbg_free( &ctx );
 }
 /* END_CASE */

 /* BEGIN_CASE */
 void hmac_drbg_buf( int md_alg )
 {
     unsigned char out[16];
     unsigned char buf[100];
     const mbedtls_md_info_t *md_info;
     mbedtls_hmac_drbg_context ctx;
     size_t i;

     mbedtls_hmac_drbg_init( &ctx );
     memset( buf, 0, sizeof( buf ) );
     memset( out, 0, sizeof( out ) );

     md_info = mbedtls_md_info_from_type( md_alg );
     TEST_ASSERT( md_info != NULL );
     TEST_ASSERT( mbedtls_hmac_drbg_seed_buf( &ctx, md_info, buf, sizeof( buf ) ) == 0 );

     /* Make sure it never tries to reseed (would segfault otherwise) */
     mbedtls_hmac_drbg_set_reseed_interval( &ctx, 3 );
     mbedtls_hmac_drbg_set_prediction_resistance( &ctx, MBEDTLS_HMAC_DRBG_PR_ON );

     for( i = 0; i < 30; i++ )
         TEST_ASSERT( mbedtls_hmac_drbg_random( &ctx, out, sizeof( out ) ) == 0 );

 exit:
     mbedtls_hmac_drbg_free( &ctx );
 }
 /* END_CASE */

 /* BEGIN_CASE */
 void hmac_drbg_no_reseed( int md_alg,
                           char *entropy_hex, char *custom_hex,
                           char *add1_hex, char *add2_hex,
                           char *output_hex )
 {
     unsigned char data[1024];
     unsigned char entropy[512];
     unsigned char custom[512];
     unsigned char add1[512];
     unsigned char add2[512];
     unsigned char output[512];
     unsigned char my_output[512];
     size_t custom_len, add1_len, add2_len, out_len;
     entropy_ctx p_entropy;
     const mbedtls_md_info_t *md_info;
     mbedtls_hmac_drbg_context ctx;

     mbedtls_hmac_drbg_init( &ctx );
     memset( my_output, 0, sizeof my_output );

     custom_len = unhexify( custom, custom_hex );
     add1_len = unhexify( add1, add1_hex );
     add2_len = unhexify( add2, add2_hex );
     out_len = unhexify( output, output_hex );
     p_entropy.len = unhexify( entropy, entropy_hex );
     p_entropy.p = entropy;

     md_info = mbedtls_md_info_from_type( md_alg );
     TEST_ASSERT( md_info != NULL );

     /* Test the simplified buffer-based variant */
     memcpy( data, entropy, p_entropy.len );
     memcpy( data + p_entropy.len, custom, custom_len );
     TEST_ASSERT( mbedtls_hmac_drbg_seed_buf( &ctx, md_info,
                                      data, p_entropy.len + custom_len ) == 0 );
     TEST_ASSERT( mbedtls_hmac_drbg_random_with_add( &ctx, my_output, out_len,
                                             add1, add1_len ) == 0 );
     TEST_ASSERT( mbedtls_hmac_drbg_random_with_add( &ctx, my_output, out_len,
                                             add2, add2_len ) == 0 );

     /* clear for second run */
     mbedtls_hmac_drbg_free( &ctx );

     TEST_ASSERT( memcmp( my_output, output, out_len ) == 0 );

     /* And now the normal entropy-based variant */
     TEST_ASSERT( mbedtls_hmac_drbg_seed( &ctx, md_info, mbedtls_entropy_func, &p_entropy,
                                  custom, custom_len ) == 0 );
     TEST_ASSERT( mbedtls_hmac_drbg_random_with_add( &ctx, my_output, out_len,
                                             add1, add1_len ) == 0 );
     TEST_ASSERT( mbedtls_hmac_drbg_random_with_add( &ctx, my_output, out_len,
                                             add2, add2_len ) == 0 );
     TEST_ASSERT( memcmp( my_output, output, out_len ) == 0 );

 exit:
     mbedtls_hmac_drbg_free( &ctx );
 }
 /* END_CASE */

 /* BEGIN_CASE */
 void hmac_drbg_nopr( int md_alg,
                      char *entropy_hex, char *custom_hex,
                      char *add1_hex, char *add2_hex, char *add3_hex,
                      char *output_hex )
 {
     unsigned char entropy[512];
     unsigned char custom[512];
     unsigned char add1[512];
     unsigned char add2[512];
     unsigned char add3[512];
     unsigned char output[512];
     unsigned char my_output[512];
     size_t custom_len, add1_len, add2_len, add3_len, out_len;
     entropy_ctx p_entropy;
     const mbedtls_md_info_t *md_info;
     mbedtls_hmac_drbg_context ctx;

     mbedtls_hmac_drbg_init( &ctx );
     memset( my_output, 0, sizeof my_output );

     custom_len = unhexify( custom, custom_hex );
     add1_len = unhexify( add1, add1_hex );
     add2_len = unhexify( add2, add2_hex );
     add3_len = unhexify( add3, add3_hex );
     out_len = unhexify( output, output_hex );
     p_entropy.len = unhexify( entropy, entropy_hex );
     p_entropy.p = entropy;

     md_info = mbedtls_md_info_from_type( md_alg );
     TEST_ASSERT( md_info != NULL );

     TEST_ASSERT( mbedtls_hmac_drbg_seed( &ctx, md_info, mbedtls_entropy_func, &p_entropy,
                                  custom, custom_len ) == 0 );
     TEST_ASSERT( mbedtls_hmac_drbg_reseed( &ctx, add1, add1_len ) == 0 );
     TEST_ASSERT( mbedtls_hmac_drbg_random_with_add( &ctx, my_output, out_len,
                                             add2, add2_len ) == 0 );
     TEST_ASSERT( mbedtls_hmac_drbg_random_with_add( &ctx, my_output, out_len,
                                             add3, add3_len ) == 0 );

     TEST_ASSERT( memcmp( my_output, output, out_len ) == 0 );

 exit:
     mbedtls_hmac_drbg_free( &ctx );
 }
 /* END_CASE */

 /* BEGIN_CASE */
 void hmac_drbg_pr( int md_alg,
                    char *entropy_hex, char *custom_hex,
                    char *add1_hex, char *add2_hex,
                    char *output_hex )
 {
     unsigned char entropy[512];
     unsigned char custom[512];
     unsigned char add1[512];
     unsigned char add2[512];
     unsigned char output[512];
     unsigned char my_output[512];
     size_t custom_len, add1_len, add2_len, out_len;
     entropy_ctx p_entropy;
     const mbedtls_md_info_t *md_info;
     mbedtls_hmac_drbg_context ctx;

     mbedtls_hmac_drbg_init( &ctx );
     memset( my_output, 0, sizeof my_output );

     custom_len = unhexify( custom, custom_hex );
     add1_len = unhexify( add1, add1_hex );
     add2_len = unhexify( add2, add2_hex );
     out_len = unhexify( output, output_hex );
     p_entropy.len = unhexify( entropy, entropy_hex );
     p_entropy.p = entropy;

     md_info = mbedtls_md_info_from_type( md_alg );
     TEST_ASSERT( md_info != NULL );

     TEST_ASSERT( mbedtls_hmac_drbg_seed( &ctx, md_info, mbedtls_entropy_func, &p_entropy,
                                  custom, custom_len ) == 0 );
     mbedtls_hmac_drbg_set_prediction_resistance( &ctx, MBEDTLS_HMAC_DRBG_PR_ON );
     TEST_ASSERT( mbedtls_hmac_drbg_random_with_add( &ctx, my_output, out_len,
                                             add1, add1_len ) == 0 );
     TEST_ASSERT( mbedtls_hmac_drbg_random_with_add( &ctx, my_output, out_len,
                                             add2, add2_len ) == 0 );

     TEST_ASSERT( memcmp( my_output, output, out_len ) == 0 );

 exit:
     mbedtls_hmac_drbg_free( &ctx );
 }
 /* END_CASE */

 /* BEGIN_CASE depends_on:MBEDTLS_SELF_TEST */
 void hmac_drbg_selftest( )
 {
     TEST_ASSERT( mbedtls_hmac_drbg_self_test( 1 ) == 0 );
 }
 /* END_CASE */
	/* BEGIN_HEADER */
	#include "mbedtls/hmac_drbg.h"

	typedef struct
	{
	unsigned char *p;
	size_t len;
	} entropy_ctx;

	int mbedtls_entropy_func( void data, unsigned char buf, size_t len )
	{
	entropy_ctx ctx = (entropy_ctx ) data;

	if( len > ctx->len )
	return( -1 );

	memcpy( buf, ctx->p, len );

	ctx->p += len;
	ctx->len -= len;

	return( 0 );
	}
	/* END_HEADER */

	/* BEGIN_DEPENDENCIES
	* depends_on:MBEDTLS_HMAC_DRBG_C
	* END_DEPENDENCIES
	*/

	/* BEGIN_CASE */
	void hmac_drbg_entropy_usage( int md_alg )
	{
	unsigned char out[16];
	unsigned char buf[1024];
	const mbedtls_md_info_t *md_info;
	mbedtls_hmac_drbg_context ctx;
	entropy_ctx entropy;
	size_t last_len, i, reps = 10;

	mbedtls_hmac_drbg_init( &ctx );
	memset( buf, 0, sizeof( buf ) );
	memset( out, 0, sizeof( out ) );

	entropy.len = sizeof( buf );
	entropy.p = buf;

	md_info = mbedtls_md_info_from_type( md_alg );
	TEST_ASSERT( md_info != NULL );

	/* Init must use entropy */
	last_len = entropy.len;
	TEST_ASSERT( mbedtls_hmac_drbg_seed( &ctx, md_info, mbedtls_entropy_func, &entropy,
	NULL, 0 ) == 0 );
	TEST_ASSERT( entropy.len < last_len );

	/* By default, PR is off and reseed_interval is large,
	* so the next few calls should not use entropy */
	last_len = entropy.len;
	for( i = 0; i < reps; i++ )
	{
	TEST_ASSERT( mbedtls_hmac_drbg_random( &ctx, out, sizeof( out ) - 4 ) == 0 );
	TEST_ASSERT( mbedtls_hmac_drbg_random_with_add( &ctx, out, sizeof( out ) - 4,
	buf, 16 ) == 0 );
	}
	TEST_ASSERT( entropy.len == last_len );

	/* While at it, make sure we didn't write past the requested length */
	TEST_ASSERT( out[sizeof( out ) - 4] == 0 );
	TEST_ASSERT( out[sizeof( out ) - 3] == 0 );
	TEST_ASSERT( out[sizeof( out ) - 2] == 0 );
	TEST_ASSERT( out[sizeof( out ) - 1] == 0 );

	/* Set reseed_interval to the number of calls done,
	* so the next call should reseed */
	mbedtls_hmac_drbg_set_reseed_interval( &ctx, 2 * reps );
	TEST_ASSERT( mbedtls_hmac_drbg_random( &ctx, out, sizeof( out ) ) == 0 );
	TEST_ASSERT( entropy.len < last_len );

	/* The new few calls should not reseed */
	last_len = entropy.len;
	for( i = 0; i < reps / 2; i++ )
	{
	TEST_ASSERT( mbedtls_hmac_drbg_random( &ctx, out, sizeof( out ) ) == 0 );
	TEST_ASSERT( mbedtls_hmac_drbg_random_with_add( &ctx, out, sizeof( out ) ,
	buf, 16 ) == 0 );
	}
	TEST_ASSERT( entropy.len == last_len );

	/* Now enable PR, so the next few calls should all reseed */
	mbedtls_hmac_drbg_set_prediction_resistance( &ctx, MBEDTLS_HMAC_DRBG_PR_ON );
	TEST_ASSERT( mbedtls_hmac_drbg_random( &ctx, out, sizeof( out ) ) == 0 );
	TEST_ASSERT( entropy.len < last_len );

	/* Finally, check setting entropy_len */
	mbedtls_hmac_drbg_set_entropy_len( &ctx, 42 );
	last_len = entropy.len;
	TEST_ASSERT( mbedtls_hmac_drbg_random( &ctx, out, sizeof( out ) ) == 0 );
	TEST_ASSERT( (int) last_len - entropy.len == 42 );

	mbedtls_hmac_drbg_set_entropy_len( &ctx, 13 );
	last_len = entropy.len;
	TEST_ASSERT( mbedtls_hmac_drbg_random( &ctx, out, sizeof( out ) ) == 0 );
	TEST_ASSERT( (int) last_len - entropy.len == 13 );

	exit:
	mbedtls_hmac_drbg_free( &ctx );
	}
	/* END_CASE */

	/* BEGIN_CASE depends_on:MBEDTLS_FS_IO */
	void hmac_drbg_seed_file( int md_alg, char *path, int ret )
	{
	const mbedtls_md_info_t *md_info;
	mbedtls_hmac_drbg_context ctx;

	mbedtls_hmac_drbg_init( &ctx );

	md_info = mbedtls_md_info_from_type( md_alg );
	TEST_ASSERT( md_info != NULL );

	TEST_ASSERT( mbedtls_hmac_drbg_seed( &ctx, md_info, rnd_std_rand, NULL,
	NULL, 0 ) == 0 );

	TEST_ASSERT( mbedtls_hmac_drbg_write_seed_file( &ctx, path ) == ret );
	TEST_ASSERT( mbedtls_hmac_drbg_update_seed_file( &ctx, path ) == ret );

	exit:
	mbedtls_hmac_drbg_free( &ctx );
	}
	/* END_CASE */

	/* BEGIN_CASE */
	void hmac_drbg_buf( int md_alg )
	{
	unsigned char out[16];
	unsigned char buf[100];
	const mbedtls_md_info_t *md_info;
	mbedtls_hmac_drbg_context ctx;
	size_t i;

	mbedtls_hmac_drbg_init( &ctx );
	memset( buf, 0, sizeof( buf ) );
	memset( out, 0, sizeof( out ) );

	md_info = mbedtls_md_info_from_type( md_alg );
	TEST_ASSERT( md_info != NULL );
	TEST_ASSERT( mbedtls_hmac_drbg_seed_buf( &ctx, md_info, buf, sizeof( buf ) ) == 0 );

	/* Make sure it never tries to reseed (would segfault otherwise) */
	mbedtls_hmac_drbg_set_reseed_interval( &ctx, 3 );
	mbedtls_hmac_drbg_set_prediction_resistance( &ctx, MBEDTLS_HMAC_DRBG_PR_ON );

	for( i = 0; i < 30; i++ )
	TEST_ASSERT( mbedtls_hmac_drbg_random( &ctx, out, sizeof( out ) ) == 0 );

	exit:
	mbedtls_hmac_drbg_free( &ctx );
	}
	/* END_CASE */

	/* BEGIN_CASE */
	void hmac_drbg_no_reseed( int md_alg,
	char entropy_hex, char custom_hex,
	char add1_hex, char add2_hex,
	char *output_hex )
	{
	unsigned char data[1024];
	unsigned char entropy[512];
	unsigned char custom[512];
	unsigned char add1[512];
	unsigned char add2[512];
	unsigned char output[512];
	unsigned char my_output[512];
	size_t custom_len, add1_len, add2_len, out_len;
	entropy_ctx p_entropy;
	const mbedtls_md_info_t *md_info;
	mbedtls_hmac_drbg_context ctx;

	mbedtls_hmac_drbg_init( &ctx );
	memset( my_output, 0, sizeof my_output );

	custom_len = unhexify( custom, custom_hex );
	add1_len = unhexify( add1, add1_hex );
	add2_len = unhexify( add2, add2_hex );
	out_len = unhexify( output, output_hex );
	p_entropy.len = unhexify( entropy, entropy_hex );
	p_entropy.p = entropy;

	md_info = mbedtls_md_info_from_type( md_alg );
	TEST_ASSERT( md_info != NULL );

	/* Test the simplified buffer-based variant */
	memcpy( data, entropy, p_entropy.len );
	memcpy( data + p_entropy.len, custom, custom_len );
	TEST_ASSERT( mbedtls_hmac_drbg_seed_buf( &ctx, md_info,
	data, p_entropy.len + custom_len ) == 0 );
	TEST_ASSERT( mbedtls_hmac_drbg_random_with_add( &ctx, my_output, out_len,
	add1, add1_len ) == 0 );
	TEST_ASSERT( mbedtls_hmac_drbg_random_with_add( &ctx, my_output, out_len,
	add2, add2_len ) == 0 );

	/* clear for second run */
	mbedtls_hmac_drbg_free( &ctx );

	TEST_ASSERT( memcmp( my_output, output, out_len ) == 0 );

	/* And now the normal entropy-based variant */
	TEST_ASSERT( mbedtls_hmac_drbg_seed( &ctx, md_info, mbedtls_entropy_func, &p_entropy,
	custom, custom_len ) == 0 );
	TEST_ASSERT( mbedtls_hmac_drbg_random_with_add( &ctx, my_output, out_len,
	add1, add1_len ) == 0 );
	TEST_ASSERT( mbedtls_hmac_drbg_random_with_add( &ctx, my_output, out_len,
	add2, add2_len ) == 0 );
	TEST_ASSERT( memcmp( my_output, output, out_len ) == 0 );

	exit:
	mbedtls_hmac_drbg_free( &ctx );
	}
	/* END_CASE */

	/* BEGIN_CASE */
	void hmac_drbg_nopr( int md_alg,
	char entropy_hex, char custom_hex,
	char add1_hex, char add2_hex, char *add3_hex,
	char *output_hex )
	{
	unsigned char entropy[512];
	unsigned char custom[512];
	unsigned char add1[512];
	unsigned char add2[512];
	unsigned char add3[512];
	unsigned char output[512];
	unsigned char my_output[512];
	size_t custom_len, add1_len, add2_len, add3_len, out_len;
	entropy_ctx p_entropy;
	const mbedtls_md_info_t *md_info;
	mbedtls_hmac_drbg_context ctx;

	mbedtls_hmac_drbg_init( &ctx );
	memset( my_output, 0, sizeof my_output );

	custom_len = unhexify( custom, custom_hex );
	add1_len = unhexify( add1, add1_hex );
	add2_len = unhexify( add2, add2_hex );
	add3_len = unhexify( add3, add3_hex );
	out_len = unhexify( output, output_hex );
	p_entropy.len = unhexify( entropy, entropy_hex );
	p_entropy.p = entropy;

	md_info = mbedtls_md_info_from_type( md_alg );
	TEST_ASSERT( md_info != NULL );

	TEST_ASSERT( mbedtls_hmac_drbg_seed( &ctx, md_info, mbedtls_entropy_func, &p_entropy,
	custom, custom_len ) == 0 );
	TEST_ASSERT( mbedtls_hmac_drbg_reseed( &ctx, add1, add1_len ) == 0 );
	TEST_ASSERT( mbedtls_hmac_drbg_random_with_add( &ctx, my_output, out_len,
	add2, add2_len ) == 0 );
	TEST_ASSERT( mbedtls_hmac_drbg_random_with_add( &ctx, my_output, out_len,
	add3, add3_len ) == 0 );

	TEST_ASSERT( memcmp( my_output, output, out_len ) == 0 );

	exit:
	mbedtls_hmac_drbg_free( &ctx );
	}
	/* END_CASE */

	/* BEGIN_CASE */
	void hmac_drbg_pr( int md_alg,
	char entropy_hex, char custom_hex,
	char add1_hex, char add2_hex,
	char *output_hex )
	{
	unsigned char entropy[512];
	unsigned char custom[512];
	unsigned char add1[512];
	unsigned char add2[512];
	unsigned char output[512];
	unsigned char my_output[512];
	size_t custom_len, add1_len, add2_len, out_len;
	entropy_ctx p_entropy;
	const mbedtls_md_info_t *md_info;
	mbedtls_hmac_drbg_context ctx;

	mbedtls_hmac_drbg_init( &ctx );
	memset( my_output, 0, sizeof my_output );

	custom_len = unhexify( custom, custom_hex );
	add1_len = unhexify( add1, add1_hex );
	add2_len = unhexify( add2, add2_hex );
	out_len = unhexify( output, output_hex );
	p_entropy.len = unhexify( entropy, entropy_hex );
	p_entropy.p = entropy;

	md_info = mbedtls_md_info_from_type( md_alg );
	TEST_ASSERT( md_info != NULL );

	TEST_ASSERT( mbedtls_hmac_drbg_seed( &ctx, md_info, mbedtls_entropy_func, &p_entropy,
	custom, custom_len ) == 0 );
	mbedtls_hmac_drbg_set_prediction_resistance( &ctx, MBEDTLS_HMAC_DRBG_PR_ON );
	TEST_ASSERT( mbedtls_hmac_drbg_random_with_add( &ctx, my_output, out_len,
	add1, add1_len ) == 0 );
	TEST_ASSERT( mbedtls_hmac_drbg_random_with_add( &ctx, my_output, out_len,
	add2, add2_len ) == 0 );

	TEST_ASSERT( memcmp( my_output, output, out_len ) == 0 );

	exit:
	mbedtls_hmac_drbg_free( &ctx );
	}
	/* END_CASE */

	/* BEGIN_CASE depends_on:MBEDTLS_SELF_TEST */
	void hmac_drbg_selftest( )
	{
	TEST_ASSERT( mbedtls_hmac_drbg_self_test( 1 ) == 0 );
	}
	/* END_CASE */