mbedtls/tests/suites/test_suite_ecdsa.function

/* BEGIN_HEADER */
#include "mbedtls/ecdsa.h"
#include "legacy_or_psa.h"
#if ( defined(MBEDTLS_ECDSA_DETERMINISTIC) && defined(MBEDTLS_SHA256_C) ) || \
    ( !defined(MBEDTLS_ECDSA_DETERMINISTIC) && defined(MBEDTLS_HAS_ALG_SHA_256_VIA_LOWLEVEL_OR_PSA) )
#define MBEDTLS_HAS_ALG_SHA_256_VIA_MD_IF_DETERMINISTIC
#endif
#define MBEDTLS_TEST_HASH_MAX_SIZE 64
/* END_HEADER */

/* BEGIN_DEPENDENCIES
 * depends_on:MBEDTLS_ECDSA_C
 * END_DEPENDENCIES
 */

/* BEGIN_CASE */
void ecdsa_prim_zero( int id )
{
    mbedtls_ecp_group grp;
    mbedtls_ecp_point Q;
    mbedtls_mpi d, r, s;
    mbedtls_test_rnd_pseudo_info rnd_info;
    unsigned char buf[MBEDTLS_TEST_HASH_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( mbedtls_test_rnd_pseudo_info ) );
    memset( buf, 0, sizeof( buf ) );

    TEST_ASSERT( mbedtls_ecp_group_load( &grp, id ) == 0 );
    TEST_ASSERT( mbedtls_ecp_gen_keypair( &grp, &d, &Q,
                                          &mbedtls_test_rnd_pseudo_rand,
                                          &rnd_info ) == 0 );

    TEST_ASSERT( mbedtls_ecdsa_sign( &grp, &r, &s, &d, buf, sizeof( buf ),
                                     &mbedtls_test_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_random( int id )
{
    mbedtls_ecp_group grp;
    mbedtls_ecp_point Q;
    mbedtls_mpi d, r, s;
    mbedtls_test_rnd_pseudo_info rnd_info;
    unsigned char buf[MBEDTLS_TEST_HASH_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( mbedtls_test_rnd_pseudo_info ) );
    memset( buf, 0, sizeof( buf ) );

    /* prepare material for signature */
    TEST_ASSERT( mbedtls_test_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,
                                          &mbedtls_test_rnd_pseudo_rand,
                                          &rnd_info ) == 0 );

    TEST_ASSERT( mbedtls_ecdsa_sign( &grp, &r, &s, &d, buf, sizeof( buf ),
                                     &mbedtls_test_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, zero;
    mbedtls_test_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 );
    mbedtls_mpi_init( &zero );

    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_test_read_mpi( &d, d_str ) == 0 );
    TEST_ASSERT( mbedtls_test_read_mpi( &r_check, r_str ) == 0 );
    TEST_ASSERT( mbedtls_test_read_mpi( &s_check, s_str ) == 0 );
    rnd_info.fallback_f_rng = mbedtls_test_rnd_std_rand;
    rnd_info.fallback_p_rng = NULL;
    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,
                 mbedtls_test_rnd_buffer_rand, &rnd_info ) == result );

    if ( result == 0)
    {
        /* Check we generated the expected values */
        TEST_EQUAL( mbedtls_mpi_cmp_mpi( &r, &r_check ), 0 );
        TEST_EQUAL( mbedtls_mpi_cmp_mpi( &s, &s_check ), 0 );

        /* Valid signature */
        TEST_EQUAL( mbedtls_ecdsa_verify( &grp, hash->x, hash->len,
                                          &Q, &r_check, &s_check ), 0 );

        /* Invalid signature: wrong public key (G instead of Q) */
        TEST_EQUAL( mbedtls_ecdsa_verify( &grp, hash->x, hash->len,
                    &grp.G, &r_check, &s_check ), MBEDTLS_ERR_ECP_VERIFY_FAILED );

        /* Invalid signatures: r or s or both one off */
        TEST_EQUAL( mbedtls_mpi_sub_int( &r, &r_check, 1 ), 0 );
        TEST_EQUAL( mbedtls_mpi_add_int( &s, &s_check, 1 ), 0 );

        TEST_EQUAL( mbedtls_ecdsa_verify( &grp, hash->x, hash->len, &Q,
                    &r, &s_check ), MBEDTLS_ERR_ECP_VERIFY_FAILED );
        TEST_EQUAL( mbedtls_ecdsa_verify( &grp, hash->x, hash->len, &Q,
                    &r_check, &s ), MBEDTLS_ERR_ECP_VERIFY_FAILED );
        TEST_EQUAL( mbedtls_ecdsa_verify( &grp, hash->x, hash->len, &Q,
                    &r, &s ), MBEDTLS_ERR_ECP_VERIFY_FAILED );

        /* Invalid signatures: r, s or both (CVE-2022-21449) are zero */
        TEST_EQUAL( mbedtls_mpi_lset( &zero, 0 ), 0 );

        TEST_EQUAL( mbedtls_ecdsa_verify( &grp, hash->x, hash->len, &Q,
                    &zero, &s_check ), MBEDTLS_ERR_ECP_VERIFY_FAILED );
        TEST_EQUAL( mbedtls_ecdsa_verify( &grp, hash->x, hash->len, &Q,
                    &r_check, &zero ), MBEDTLS_ERR_ECP_VERIFY_FAILED );
        TEST_EQUAL( mbedtls_ecdsa_verify( &grp, hash->x, hash->len, &Q,
                    &zero, &zero ), MBEDTLS_ERR_ECP_VERIFY_FAILED );

        /* Invalid signatures: r, s or both are == N */
        TEST_EQUAL( mbedtls_ecdsa_verify( &grp, hash->x, hash->len, &Q,
                    &grp.N, &s_check ), MBEDTLS_ERR_ECP_VERIFY_FAILED );
        TEST_EQUAL( mbedtls_ecdsa_verify( &grp, hash->x, hash->len, &Q,
                    &r_check, &grp.N ), MBEDTLS_ERR_ECP_VERIFY_FAILED );
        TEST_EQUAL( mbedtls_ecdsa_verify( &grp, hash->x, hash->len, &Q,
                    &grp.N, &grp.N ), MBEDTLS_ERR_ECP_VERIFY_FAILED );

        /* Invalid signatures: r, s or both are negative */
        TEST_EQUAL( mbedtls_mpi_sub_mpi( &r, &r_check, &grp.N ), 0 );
        TEST_EQUAL( mbedtls_mpi_sub_mpi( &s, &s_check, &grp.N ), 0 );

        TEST_EQUAL( mbedtls_ecdsa_verify( &grp, hash->x, hash->len, &Q,
                    &r, &s_check ), MBEDTLS_ERR_ECP_VERIFY_FAILED );
        TEST_EQUAL( mbedtls_ecdsa_verify( &grp, hash->x, hash->len, &Q,
                    &r_check, &s ), MBEDTLS_ERR_ECP_VERIFY_FAILED );
        TEST_EQUAL( mbedtls_ecdsa_verify( &grp, hash->x, hash->len, &Q,
                    &r, &s ), MBEDTLS_ERR_ECP_VERIFY_FAILED );

        /* Invalid signatures: r or s or both are > N */
        TEST_EQUAL( mbedtls_mpi_add_mpi( &r, &r_check, &grp.N ), 0 );
        TEST_EQUAL( mbedtls_mpi_add_mpi( &s, &s_check, &grp.N ), 0 );

        TEST_EQUAL( mbedtls_ecdsa_verify( &grp, hash->x, hash->len, &Q,
                    &r, &s_check ), MBEDTLS_ERR_ECP_VERIFY_FAILED );
        TEST_EQUAL( mbedtls_ecdsa_verify( &grp, hash->x, hash->len, &Q,
                    &r_check, &s ), MBEDTLS_ERR_ECP_VERIFY_FAILED );
        TEST_EQUAL( mbedtls_ecdsa_verify( &grp, hash->x, hash->len, &Q,
                    &r, &s ), 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 );
    mbedtls_mpi_free( &zero );
}
/* END_CASE */

/* BEGIN_CASE depends_on:MBEDTLS_ECDSA_DETERMINISTIC */
void ecdsa_det_test_vectors( int id, char * d_str, int md_alg, data_t * hash,
                             char * r_str, char * s_str )
{
    mbedtls_ecp_group grp;
    mbedtls_mpi d, r, s, r_check, s_check;

    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 );

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

    TEST_ASSERT(
                mbedtls_ecdsa_sign_det_ext( &grp, &r, &s, &d,
                                            hash->x, hash->len, md_alg,
                                            mbedtls_test_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_HAS_ALG_SHA_256_VIA_MD_IF_DETERMINISTIC */
void ecdsa_write_read_zero( int id )
{
    mbedtls_ecdsa_context ctx;
    mbedtls_test_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( mbedtls_test_rnd_pseudo_info ) );
    memset( hash, 0, sizeof( hash ) );
    memset( sig, 0x2a, sizeof( sig ) );

    /* generate signing key */
    TEST_ASSERT( mbedtls_ecdsa_genkey( &ctx, id,
                                       &mbedtls_test_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, sizeof( sig ), &sig_len, &mbedtls_test_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_HAS_ALG_SHA_256_VIA_MD_IF_DETERMINISTIC */
void ecdsa_write_read_random( int id )
{
    mbedtls_ecdsa_context ctx;
    mbedtls_test_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( mbedtls_test_rnd_pseudo_info ) );
    memset( hash, 0, sizeof( hash ) );
    memset( sig, 0x2a, sizeof( sig ) );

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

    /* generate signing key */
    TEST_ASSERT( mbedtls_ecdsa_genkey( &ctx, id,
                                       &mbedtls_test_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, sizeof( sig ), &sig_len, &mbedtls_test_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, data_t *pk, data_t *hash, data_t *sig,
                         int max_ops, int min_restart, int max_restart )
{
    mbedtls_ecdsa_context ctx;
    mbedtls_ecdsa_restart_ctx rs_ctx;
    int ret, cnt_restart;

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

    TEST_ASSERT( mbedtls_ecp_group_load( &ctx.grp, id ) == 0 );
    TEST_ASSERT( mbedtls_ecp_point_read_binary( &ctx.grp, &ctx.Q,
                                                pk->x, pk->len ) == 0 );

    mbedtls_ecp_set_max_ops( max_ops );

    cnt_restart = 0;
    do {
        ret = mbedtls_ecdsa_read_signature_restartable( &ctx,
                            hash->x, hash->len, sig->x, 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 */

    TEST_ASSERT( sig->len > 10 );
    sig->x[10]++;
    do {
        ret = mbedtls_ecdsa_read_signature_restartable( &ctx,
                            hash->x, hash->len, sig->x, sig->len, &rs_ctx );
    } while( ret == MBEDTLS_ERR_ECP_IN_PROGRESS );
    TEST_ASSERT( ret == MBEDTLS_ERR_ECP_VERIFY_FAILED );
    sig->x[10]--;

    /* try modifying s */
    sig->x[sig->len - 1]++;
    do {
        ret = mbedtls_ecdsa_read_signature_restartable( &ctx,
                            hash->x, hash->len, sig->x, sig->len, &rs_ctx );
    } while( ret == MBEDTLS_ERR_ECP_IN_PROGRESS );
    TEST_ASSERT( ret == MBEDTLS_ERR_ECP_VERIFY_FAILED );
    sig->x[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->x, hash->len, sig->x, 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,
                          data_t *hash, data_t *sig_check,
                          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 sig[MBEDTLS_ECDSA_MAX_LEN];
    size_t slen;

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

    TEST_ASSERT( mbedtls_ecp_group_load( &ctx.grp, id ) == 0 );
    TEST_ASSERT( mbedtls_test_read_mpi( &ctx.d, d_str ) == 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->x, hash->len, sig, sizeof( sig ), &slen,
                mbedtls_test_rnd_std_rand, NULL, &rs_ctx );
    } while( ret == MBEDTLS_ERR_ECP_IN_PROGRESS && ++cnt_restart );

    TEST_ASSERT( ret == 0 );
    TEST_ASSERT( slen == sig_check->len );
    TEST_ASSERT( memcmp( sig, sig_check->x, 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->x, hash->len, sig, sizeof( sig ), &slen,
                mbedtls_test_rnd_std_rand, NULL, &rs_ctx );
        TEST_ASSERT( ret == MBEDTLS_ERR_ECP_IN_PROGRESS );
    }

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

/* BEGIN_CASE */
void ecdsa_verify( int grp_id, char * x, char * y, char * r, char * s, data_t * content, int expected )
{
    mbedtls_ecdsa_context ctx;
    mbedtls_mpi sig_r, sig_s;
    const mbedtls_ecp_curve_info *curve_info;

    mbedtls_ecdsa_init( &ctx );
    mbedtls_mpi_init( &sig_r );
    mbedtls_mpi_init( &sig_s );

    /* Prepare ECP group context */
    TEST_EQUAL( mbedtls_ecp_group_load( &ctx.grp, grp_id ), 0 );

    /* Prepare public key */
    TEST_EQUAL( mbedtls_test_read_mpi( &ctx.Q.X, x ), 0 );
    TEST_EQUAL( mbedtls_test_read_mpi( &ctx.Q.Y, y ), 0 );
    TEST_EQUAL( mbedtls_mpi_lset( &ctx.Q.Z, 1 ), 0 );

    /* Prepare signature R & S */
    TEST_EQUAL( mbedtls_test_read_mpi( &sig_r, r ), 0 );
    TEST_EQUAL( mbedtls_test_read_mpi( &sig_s, s ), 0 );

    /* Test whether public key has expected validity */
    TEST_EQUAL( mbedtls_ecp_check_pubkey( &ctx.grp, &ctx.Q ),
        expected == MBEDTLS_ERR_ECP_INVALID_KEY ? MBEDTLS_ERR_ECP_INVALID_KEY : 0 );

    /* Verification */
    int result = mbedtls_ecdsa_verify( &ctx.grp, content->x, content->len, &ctx.Q, &sig_r, &sig_s );

    TEST_EQUAL( result, expected );
exit:
    mbedtls_ecdsa_free( &ctx );
    mbedtls_mpi_free( &sig_r );
    mbedtls_mpi_free( &sig_s );
}
/* END_CASE */