tests/suites/test_suite_ecdsa.function

/* BEGIN_HEADER */
#include "mbedtls/ecdsa.h"
/* END_HEADER */

/* BEGIN_DEPENDENCIES
 * depends_on:MBEDTLS_ECDSA_C
 * END_DEPENDENCIES
 */

/* BEGIN_CASE depends_on:MBEDTLS_CHECK_PARAMS:!MBEDTLS_PARAM_FAILED_ALT */
void ecdsa_invalid_param( )
{
    mbedtls_ecdsa_context ctx;
    mbedtls_ecp_keypair key;
    mbedtls_ecp_group grp;
    mbedtls_ecp_group_id valid_group = MBEDTLS_ECP_DP_SECP192R1;
    mbedtls_ecp_point P;
    mbedtls_md_type_t valid_md = MBEDTLS_MD_SHA256;
    mbedtls_mpi m;
    size_t slen;
    unsigned char buf[42] = { 0 };

    TEST_INVALID_PARAM( mbedtls_ecdsa_init( NULL ) );
    TEST_VALID_PARAM( mbedtls_ecdsa_free( NULL ) );

#if defined(MBEDTLS_ECP_RESTARTABLE)
    TEST_INVALID_PARAM( mbedtls_ecdsa_restart_init( NULL ) );
    TEST_VALID_PARAM( mbedtls_ecdsa_restart_free( NULL ) );
#endif /* MBEDTLS_ECP_RESTARTABLE */

    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                            mbedtls_ecdsa_sign( NULL, &m, &m, &m,
                                                buf, sizeof( buf ),
                                                rnd_std_rand, NULL ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                            mbedtls_ecdsa_sign( &grp, NULL, &m, &m,
                                                buf, sizeof( buf ),
                                                rnd_std_rand, NULL ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_sign( &grp, &m, NULL, &m,
                                                buf, sizeof( buf ),
                                                rnd_std_rand, NULL ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_sign( &grp, &m, &m, NULL,
                                                buf, sizeof( buf ),
                                                rnd_std_rand, NULL ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_sign( &grp, &m, &m, &m,
                                                NULL, sizeof( buf ),
                                                rnd_std_rand, NULL ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_sign( &grp, &m, &m, &m,
                                                buf, sizeof( buf ),
                                                NULL, NULL ) );

#if defined(MBEDTLS_ECDSA_DETERMINISTIC)
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_sign_det( NULL, &m, &m, &m,
                                                buf, sizeof( buf ),
                                                valid_md ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_sign_det( &grp, NULL, &m, &m,
                                                buf, sizeof( buf ),
                                                valid_md ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_sign_det( &grp, &m, NULL, &m,
                                                buf, sizeof( buf ),
                                                valid_md ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_sign_det( &grp, &m, &m, NULL,
                                                buf, sizeof( buf ),
                                                valid_md ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_sign_det( &grp, &m, &m, &m,
                                                NULL, sizeof( buf ),
                                                valid_md ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_sign_det_ext( NULL, &m, &m, &m,
                                                   buf, sizeof( buf ),
                                                   valid_md,
                                                   rnd_std_rand, NULL ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_sign_det_ext( &grp, NULL, &m, &m,
                                                   buf, sizeof( buf ),
                                                   valid_md,
                                                   rnd_std_rand, NULL ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_sign_det_ext( &grp, &m, NULL, &m,
                                                   buf, sizeof( buf ),
                                                   valid_md,
                                                   rnd_std_rand, NULL ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_sign_det_ext( &grp, &m, &m, NULL,
                                                   buf, sizeof( buf ),
                                                   valid_md,
                                                   rnd_std_rand, NULL ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_sign_det_ext( &grp, &m, &m, &m,
                                                   NULL, sizeof( buf ),
                                                   valid_md,
                                                   rnd_std_rand, NULL ) );
#endif /* MBEDTLS_ECDSA_DETERMINISTIC */

    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_verify( NULL,
                                                  buf, sizeof( buf ),
                                                  &P, &m, &m ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_verify( &grp,
                                                  NULL, sizeof( buf ),
                                                  &P, &m, &m ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_verify( &grp,
                                                  buf, sizeof( buf ),
                                                  NULL, &m, &m ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_verify( &grp,
                                                  buf, sizeof( buf ),
                                                  &P, NULL, &m ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_verify( &grp,
                                                  buf, sizeof( buf ),
                                                  &P, &m, NULL ) );

    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_write_signature( NULL,
                                                           valid_md,
                                                           buf, sizeof( buf ),
                                                           buf, &slen,
                                                           rnd_std_rand,
                                                           NULL ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_write_signature( &ctx,
                                                           valid_md,
                                                           NULL, sizeof( buf ),
                                                           buf, &slen,
                                                           rnd_std_rand,
                                                           NULL ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_write_signature( &ctx,
                                                           valid_md,
                                                           buf, sizeof( buf ),
                                                           NULL, &slen,
                                                           rnd_std_rand,
                                                           NULL ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_write_signature( &ctx,
                                                           valid_md,
                                                           buf, sizeof( buf ),
                                                           buf, NULL,
                                                           rnd_std_rand,
                                                           NULL ) );

    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_write_signature_restartable( NULL,
                                                           valid_md,
                                                           buf, sizeof( buf ),
                                                           buf, &slen,
                                                           rnd_std_rand,
                                                           NULL, NULL ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_write_signature_restartable( &ctx,
                                                           valid_md,
                                                           NULL, sizeof( buf ),
                                                           buf, &slen,
                                                           rnd_std_rand,
                                                           NULL, NULL ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_write_signature_restartable( &ctx,
                                                           valid_md,
                                                           buf, sizeof( buf ),
                                                           NULL, &slen,
                                                           rnd_std_rand,
                                                           NULL, NULL ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_write_signature_restartable( &ctx,
                                                           valid_md,
                                                           buf, sizeof( buf ),
                                                           buf, NULL,
                                                           rnd_std_rand,
                                                           NULL, NULL ) );

    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_read_signature( NULL,
                                                        buf, sizeof( buf ),
                                                        buf, sizeof( buf ) ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_read_signature( &ctx,
                                                        NULL, sizeof( buf ),
                                                        buf, sizeof( buf ) ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_read_signature( &ctx,
                                                        buf, sizeof( buf ),
                                                        NULL, sizeof( buf ) ) );

    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_read_signature_restartable( NULL,
                                                        buf, sizeof( buf ),
                                                        buf, sizeof( buf ),
                                                        NULL ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_read_signature_restartable( &ctx,
                                                        NULL, sizeof( buf ),
                                                        buf, sizeof( buf ),
                                                        NULL ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_read_signature_restartable( &ctx,
                                                        buf, sizeof( buf ),
                                                        NULL, sizeof( buf ),
                                                        NULL ) );

    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_genkey( NULL, valid_group,
                                                  rnd_std_rand, NULL ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_genkey( &ctx, valid_group,
                                                  NULL, NULL ) );


    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_from_keypair( NULL, &key ) );
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_ECP_BAD_INPUT_DATA,
                       mbedtls_ecdsa_from_keypair( &ctx, NULL ) );

exit:
    return;
}
/* END_CASE */

/* BEGIN_CASE */
void ecdsa_prim_random( int id )
{
    mbedtls_ecp_group grp;
    mbedtls_ecp_point Q;
    mbedtls_mpi d, r, s;
    rnd_pseudo_info rnd_info;
    unsigned char buf[MBEDTLS_MD_MAX_SIZE];

    mbedtls_ecp_group_init( &grp );
    mbedtls_ecp_point_init( &Q );
    mbedtls_mpi_init( &d ); mbedtls_mpi_init( &r ); mbedtls_mpi_init( &s );
    memset( &rnd_info, 0x00, sizeof( rnd_pseudo_info ) );
    memset( buf, 0, sizeof( buf ) );

    /* prepare material for signature */
    TEST_ASSERT( rnd_pseudo_rand( &rnd_info, buf, sizeof( buf ) ) == 0 );
    TEST_ASSERT( mbedtls_ecp_group_load( &grp, id ) == 0 );
    TEST_ASSERT( mbedtls_ecp_gen_keypair( &grp, &d, &Q, &rnd_pseudo_rand, &rnd_info )
                 == 0 );

    TEST_ASSERT( mbedtls_ecdsa_sign( &grp, &r, &s, &d, buf, sizeof( buf ),
                             &rnd_pseudo_rand, &rnd_info ) == 0 );
    TEST_ASSERT( mbedtls_ecdsa_verify( &grp, buf, sizeof( buf ), &Q, &r, &s ) == 0 );

exit:
    mbedtls_ecp_group_free( &grp );
    mbedtls_ecp_point_free( &Q );
    mbedtls_mpi_free( &d ); mbedtls_mpi_free( &r ); mbedtls_mpi_free( &s );
}
/* END_CASE */

/* BEGIN_CASE */
void ecdsa_prim_test_vectors( int id, char * d_str, char * xQ_str,
                              char * yQ_str, data_t * rnd_buf,
                              data_t * hash, char * r_str, char * s_str,
                              int result )
{
    mbedtls_ecp_group grp;
    mbedtls_ecp_point Q;
    mbedtls_mpi d, r, s, r_check, s_check;
    rnd_buf_info rnd_info;

    mbedtls_ecp_group_init( &grp );
    mbedtls_ecp_point_init( &Q );
    mbedtls_mpi_init( &d ); mbedtls_mpi_init( &r ); mbedtls_mpi_init( &s );
    mbedtls_mpi_init( &r_check ); mbedtls_mpi_init( &s_check );

    TEST_ASSERT( mbedtls_ecp_group_load( &grp, id ) == 0 );
    TEST_ASSERT( mbedtls_ecp_point_read_string( &Q, 16, xQ_str, yQ_str ) == 0 );
    TEST_ASSERT( mbedtls_mpi_read_string( &d, 16, d_str ) == 0 );
    TEST_ASSERT( mbedtls_mpi_read_string( &r_check, 16, r_str ) == 0 );
    TEST_ASSERT( mbedtls_mpi_read_string( &s_check, 16, s_str ) == 0 );
    rnd_info.buf = rnd_buf->x;
    rnd_info.length = rnd_buf->len;

    /* Fix rnd_buf->x by shifting it left if necessary */
    if( grp.nbits % 8 != 0 )
    {
        unsigned char shift = 8 - ( grp.nbits % 8 );
        size_t i;

        for( i = 0; i < rnd_info.length - 1; i++ )
            rnd_buf->x[i] = rnd_buf->x[i] << shift | rnd_buf->x[i+1] >> ( 8 - shift );

        rnd_buf->x[rnd_info.length-1] <<= shift;
    }

    TEST_ASSERT( mbedtls_ecdsa_sign( &grp, &r, &s, &d, hash->x, hash->len,
                 rnd_buffer_rand, &rnd_info ) == result );

    if ( result == 0)
    {
        TEST_ASSERT( mbedtls_mpi_cmp_mpi( &r, &r_check ) == 0 );
        TEST_ASSERT( mbedtls_mpi_cmp_mpi( &s, &s_check ) == 0 );

        TEST_ASSERT( mbedtls_ecdsa_verify( &grp, hash->x, hash->len, &Q, &r_check, &s_check ) == 0 );

        TEST_ASSERT( mbedtls_mpi_sub_int( &r, &r, 1 ) == 0 );
        TEST_ASSERT( mbedtls_mpi_add_int( &s, &s, 1 ) == 0 );

        TEST_ASSERT( mbedtls_ecdsa_verify( &grp, hash->x, hash->len,
                     &Q, &r, &s_check ) == MBEDTLS_ERR_ECP_VERIFY_FAILED );
        TEST_ASSERT( mbedtls_ecdsa_verify( &grp, hash->x, hash->len,
                     &Q, &r_check, &s ) == MBEDTLS_ERR_ECP_VERIFY_FAILED );
        TEST_ASSERT( mbedtls_ecdsa_verify( &grp, hash->x, hash->len,
                     &grp.G, &r_check, &s_check ) == MBEDTLS_ERR_ECP_VERIFY_FAILED );
    }

exit:
    mbedtls_ecp_group_free( &grp );
    mbedtls_ecp_point_free( &Q );
    mbedtls_mpi_free( &d ); mbedtls_mpi_free( &r ); mbedtls_mpi_free( &s );
    mbedtls_mpi_free( &r_check ); mbedtls_mpi_free( &s_check );
}
/* END_CASE */

/* BEGIN_CASE depends_on:MBEDTLS_ECDSA_DETERMINISTIC */
void ecdsa_det_test_vectors( int id, char * d_str, int md_alg, char * msg,
                             char * r_str, char * s_str )
{
    mbedtls_ecp_group grp;
    mbedtls_mpi d, r, s, r_check, s_check;
    unsigned char hash[MBEDTLS_MD_MAX_SIZE];
    size_t hlen;
    const mbedtls_md_info_t *md_info;

    mbedtls_ecp_group_init( &grp );
    mbedtls_mpi_init( &d ); mbedtls_mpi_init( &r ); mbedtls_mpi_init( &s );
    mbedtls_mpi_init( &r_check ); mbedtls_mpi_init( &s_check );
    memset( hash, 0, sizeof( hash ) );

    TEST_ASSERT( mbedtls_ecp_group_load( &grp, id ) == 0 );
    TEST_ASSERT( mbedtls_mpi_read_string( &d, 16, d_str ) == 0 );
    TEST_ASSERT( mbedtls_mpi_read_string( &r_check, 16, r_str ) == 0 );
    TEST_ASSERT( mbedtls_mpi_read_string( &s_check, 16, s_str ) == 0 );

    md_info = mbedtls_md_info_from_type( md_alg );
    TEST_ASSERT( md_info != NULL );
    hlen = mbedtls_md_get_size( md_info );
    TEST_ASSERT( mbedtls_md( md_info, (const unsigned char *) msg,
                 strlen( msg ), hash ) == 0 );

    TEST_ASSERT( mbedtls_ecdsa_sign_det( &grp, &r, &s, &d, hash, hlen, md_alg ) == 0 );

    TEST_ASSERT( mbedtls_mpi_cmp_mpi( &r, &r_check ) == 0 );
    TEST_ASSERT( mbedtls_mpi_cmp_mpi( &s, &s_check ) == 0 );

    mbedtls_mpi_free( &r ); mbedtls_mpi_free( &s );
    mbedtls_mpi_init( &r ); mbedtls_mpi_init( &s );

    TEST_ASSERT(
                mbedtls_ecdsa_sign_det_ext( &grp, &r, &s, &d, hash, hlen,
                                            md_alg, rnd_std_rand, NULL )
                == 0 );

    TEST_ASSERT( mbedtls_mpi_cmp_mpi( &r, &r_check ) == 0 );
    TEST_ASSERT( mbedtls_mpi_cmp_mpi( &s, &s_check ) == 0 );
exit:
    mbedtls_ecp_group_free( &grp );
    mbedtls_mpi_free( &d ); mbedtls_mpi_free( &r ); mbedtls_mpi_free( &s );
    mbedtls_mpi_free( &r_check ); mbedtls_mpi_free( &s_check );
}
/* END_CASE */

/* BEGIN_CASE depends_on:MBEDTLS_SHA256_C */
void ecdsa_write_read_random( int id )
{
    mbedtls_ecdsa_context ctx;
    rnd_pseudo_info rnd_info;
    unsigned char hash[32];
    unsigned char sig[200];
    size_t sig_len, i;

    mbedtls_ecdsa_init( &ctx );
    memset( &rnd_info, 0x00, sizeof( rnd_pseudo_info ) );
    memset( hash, 0, sizeof( hash ) );
    memset( sig, 0x2a, sizeof( sig ) );

    /* prepare material for signature */
    TEST_ASSERT( rnd_pseudo_rand( &rnd_info, hash, sizeof( hash ) ) == 0 );

    /* generate signing key */
    TEST_ASSERT( mbedtls_ecdsa_genkey( &ctx, id, &rnd_pseudo_rand, &rnd_info ) == 0 );

    /* generate and write signature, then read and verify it */
    TEST_ASSERT( mbedtls_ecdsa_write_signature( &ctx, MBEDTLS_MD_SHA256,
                 hash, sizeof( hash ),
                 sig, &sig_len, &rnd_pseudo_rand, &rnd_info ) == 0 );
    TEST_ASSERT( mbedtls_ecdsa_read_signature( &ctx, hash, sizeof( hash ),
                 sig, sig_len ) == 0 );

    /* check we didn't write past the announced length */
    for( i = sig_len; i < sizeof( sig ); i++ )
        TEST_ASSERT( sig[i] == 0x2a );

    /* try verification with invalid length */
    TEST_ASSERT( mbedtls_ecdsa_read_signature( &ctx, hash, sizeof( hash ),
                 sig, sig_len - 1 ) != 0 );
    TEST_ASSERT( mbedtls_ecdsa_read_signature( &ctx, hash, sizeof( hash ),
                 sig, sig_len + 1 ) != 0 );

    /* try invalid sequence tag */
    sig[0]++;
    TEST_ASSERT( mbedtls_ecdsa_read_signature( &ctx, hash, sizeof( hash ),
                 sig, sig_len ) != 0 );
    sig[0]--;

    /* try modifying r */
    sig[10]++;
    TEST_ASSERT( mbedtls_ecdsa_read_signature( &ctx, hash, sizeof( hash ),
                 sig, sig_len ) == MBEDTLS_ERR_ECP_VERIFY_FAILED );
    sig[10]--;

    /* try modifying s */
    sig[sig_len - 1]++;
    TEST_ASSERT( mbedtls_ecdsa_read_signature( &ctx, hash, sizeof( hash ),
                 sig, sig_len ) == MBEDTLS_ERR_ECP_VERIFY_FAILED );
    sig[sig_len - 1]--;

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

/* BEGIN_CASE depends_on:MBEDTLS_ECP_RESTARTABLE */
void ecdsa_read_restart( int id, char *k_str, char *h_str, char *s_str,
                         int max_ops, int min_restart, int max_restart )
{
    mbedtls_ecdsa_context ctx;
    mbedtls_ecdsa_restart_ctx rs_ctx;
    unsigned char hash[64];
    unsigned char sig[200];
    unsigned char pk[65];
    size_t sig_len, hash_len, pk_len;
    int ret, cnt_restart;

    mbedtls_ecdsa_init( &ctx );
    mbedtls_ecdsa_restart_init( &rs_ctx );

    hash_len = unhexify(hash, h_str);
    sig_len = unhexify(sig, s_str);
    pk_len = unhexify(pk, k_str);

    TEST_ASSERT( mbedtls_ecp_group_load( &ctx.grp, id ) == 0 );
    TEST_ASSERT( mbedtls_ecp_point_read_binary( &ctx.grp, &ctx.Q, pk, pk_len ) == 0 );

    mbedtls_ecp_set_max_ops( max_ops );

    cnt_restart = 0;
    do {
        ret = mbedtls_ecdsa_read_signature_restartable( &ctx,
                            hash, hash_len, sig, sig_len, &rs_ctx );
    } while( ret == MBEDTLS_ERR_ECP_IN_PROGRESS && ++cnt_restart );

    TEST_ASSERT( ret == 0 );
    TEST_ASSERT( cnt_restart >= min_restart );
    TEST_ASSERT( cnt_restart <= max_restart );

    /* try modifying r */
    sig[10]++;
    do {
        ret = mbedtls_ecdsa_read_signature_restartable( &ctx,
                            hash, hash_len, sig, sig_len, &rs_ctx );
    } while( ret == MBEDTLS_ERR_ECP_IN_PROGRESS );
    TEST_ASSERT( ret == MBEDTLS_ERR_ECP_VERIFY_FAILED );
    sig[10]--;

    /* try modifying s */
    sig[sig_len - 1]++;
    do {
        ret = mbedtls_ecdsa_read_signature_restartable( &ctx,
                            hash, hash_len, sig, sig_len, &rs_ctx );
    } while( ret == MBEDTLS_ERR_ECP_IN_PROGRESS );
    TEST_ASSERT( ret == MBEDTLS_ERR_ECP_VERIFY_FAILED );
    sig[sig_len - 1]--;

    /* Do we leak memory when aborting an operation?
     * This test only makes sense when we actually restart */
    if( min_restart > 0 )
    {
        ret = mbedtls_ecdsa_read_signature_restartable( &ctx,
                            hash, hash_len, sig, sig_len, &rs_ctx );
        TEST_ASSERT( ret == MBEDTLS_ERR_ECP_IN_PROGRESS );
    }

exit:
    mbedtls_ecdsa_free( &ctx );
    mbedtls_ecdsa_restart_free( &rs_ctx );
}
/* END_CASE */

/* BEGIN_CASE depends_on:MBEDTLS_ECP_RESTARTABLE:MBEDTLS_ECDSA_DETERMINISTIC */
void ecdsa_write_restart( int id, char *d_str, int md_alg,
                          char *msg, char *sig_str,
                          int max_ops, int min_restart, int max_restart )
{
    int ret, cnt_restart;
    mbedtls_ecdsa_restart_ctx rs_ctx;
    mbedtls_ecdsa_context ctx;
    unsigned char hash[MBEDTLS_MD_MAX_SIZE];
    unsigned char sig[MBEDTLS_ECDSA_MAX_LEN];
    unsigned char sig_check[MBEDTLS_ECDSA_MAX_LEN];
    size_t hlen, slen, slen_check;
    const mbedtls_md_info_t *md_info;

    mbedtls_ecdsa_restart_init( &rs_ctx );
    mbedtls_ecdsa_init( &ctx );
    memset( hash, 0, sizeof( hash ) );
    memset( sig, 0, sizeof( sig ) );
    memset( sig_check, 0, sizeof( sig_check ) );

    TEST_ASSERT( mbedtls_ecp_group_load( &ctx.grp, id ) == 0 );
    TEST_ASSERT( mbedtls_mpi_read_string( &ctx.d, 16, d_str ) == 0 );
    slen_check = unhexify( sig_check, sig_str );

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

    hlen = mbedtls_md_get_size( md_info );
    TEST_ASSERT( mbedtls_md( md_info,
                             (const unsigned char *) msg, strlen( msg ),
                             hash ) == 0 );

    mbedtls_ecp_set_max_ops( max_ops );

    slen = sizeof( sig );
    cnt_restart = 0;
    do {
        ret = mbedtls_ecdsa_write_signature_restartable( &ctx,
                md_alg, hash, hlen, sig, &slen, NULL, NULL, &rs_ctx );
    } while( ret == MBEDTLS_ERR_ECP_IN_PROGRESS && ++cnt_restart );

    TEST_ASSERT( ret == 0 );
    TEST_ASSERT( slen == slen_check );
    TEST_ASSERT( memcmp( sig, sig_check, slen ) == 0 );

    TEST_ASSERT( cnt_restart >= min_restart );
    TEST_ASSERT( cnt_restart <= max_restart );

    /* Do we leak memory when aborting an operation?
     * This test only makes sense when we actually restart */
    if( min_restart > 0 )
    {
        ret = mbedtls_ecdsa_write_signature_restartable( &ctx,
                md_alg, hash, hlen, sig, &slen, NULL, NULL, &rs_ctx );
        TEST_ASSERT( ret == MBEDTLS_ERR_ECP_IN_PROGRESS );
    }

exit:
    mbedtls_ecdsa_restart_free( &rs_ctx );
    mbedtls_ecdsa_free( &ctx );
}
/* END_CASE */