mbedtls/tests/suites/test_suite_cipher.function

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

#if defined(MBEDTLS_GCM_C)
#include "mbedtls/gcm.h"
#endif
/* END_HEADER */

/* BEGIN_DEPENDENCIES
 * depends_on:MBEDTLS_CIPHER_C
 * END_DEPENDENCIES
 */

/* BEGIN_CASE */
void mbedtls_cipher_list(  )
{
    const int *cipher_type;

    for( cipher_type = mbedtls_cipher_list(); *cipher_type != 0; cipher_type++ )
        TEST_ASSERT( mbedtls_cipher_info_from_type( *cipher_type ) != NULL );
}
/* END_CASE */

/* BEGIN_CASE */
void cipher_invalid_param_unconditional( )
{
    mbedtls_cipher_context_t valid_ctx;
    mbedtls_cipher_context_t invalid_ctx;
    mbedtls_operation_t valid_operation = MBEDTLS_ENCRYPT;
    mbedtls_cipher_padding_t valid_mode = MBEDTLS_PADDING_ZEROS;
    unsigned char valid_buffer[] = { 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07 };
    int valid_size = sizeof(valid_buffer);
    int valid_bitlen = valid_size * 8;
    const mbedtls_cipher_info_t *valid_info = mbedtls_cipher_info_from_type(
        *( mbedtls_cipher_list() ) );
    size_t size_t_var;

    (void)valid_mode; /* In some configurations this is unused */

    mbedtls_cipher_init( &valid_ctx );
    mbedtls_cipher_setup( &valid_ctx, valid_info );
    mbedtls_cipher_init( &invalid_ctx );

    /* mbedtls_cipher_setup() */
    TEST_ASSERT( mbedtls_cipher_setup( &valid_ctx, NULL ) ==
                 MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );

    /* mbedtls_cipher_get_block_size() */
    TEST_ASSERT( mbedtls_cipher_get_block_size( &invalid_ctx ) == 0 );

    /* mbedtls_cipher_get_cipher_mode() */
    TEST_ASSERT( mbedtls_cipher_get_cipher_mode( &invalid_ctx ) ==
                 MBEDTLS_MODE_NONE );

    /* mbedtls_cipher_get_iv_size() */
    TEST_ASSERT( mbedtls_cipher_get_iv_size( &invalid_ctx ) == 0 );

    /* mbedtls_cipher_get_type() */
    TEST_ASSERT(
        mbedtls_cipher_get_type( &invalid_ctx ) ==
        MBEDTLS_CIPHER_NONE);

    /* mbedtls_cipher_get_name() */
    TEST_ASSERT( mbedtls_cipher_get_name( &invalid_ctx ) == 0 );

    /* mbedtls_cipher_get_key_bitlen() */
    TEST_ASSERT( mbedtls_cipher_get_key_bitlen( &invalid_ctx ) ==
                 MBEDTLS_KEY_LENGTH_NONE );

    /* mbedtls_cipher_get_operation() */
    TEST_ASSERT( mbedtls_cipher_get_operation( &invalid_ctx ) ==
                 MBEDTLS_OPERATION_NONE );

    /* mbedtls_cipher_setkey() */
    TEST_ASSERT(
        mbedtls_cipher_setkey( &invalid_ctx,
                               valid_buffer,
                               valid_bitlen,
                               valid_operation ) ==
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );

    /* mbedtls_cipher_set_iv() */
    TEST_ASSERT(
        mbedtls_cipher_set_iv( &invalid_ctx,
                               valid_buffer,
                               valid_size ) ==
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );

    /* mbedtls_cipher_reset() */
    TEST_ASSERT( mbedtls_cipher_reset( &invalid_ctx ) ==
                 MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );

#if defined(MBEDTLS_GCM_C) || defined(MBEDTLS_CHACHAPOLY_C)
    /* mbedtls_cipher_update_ad() */
    TEST_ASSERT(
        mbedtls_cipher_update_ad( &invalid_ctx,
                                  valid_buffer,
                                  valid_size ) ==
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
#endif /* defined(MBEDTLS_GCM_C) || defined(MBEDTLS_CHACHAPOLY_C) */

#if defined(MBEDTLS_CIPHER_MODE_WITH_PADDING)
    /* mbedtls_cipher_set_padding_mode() */
    TEST_ASSERT( mbedtls_cipher_set_padding_mode( &invalid_ctx, valid_mode ) ==
                 MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
#endif

    /* mbedtls_cipher_update() */
    TEST_ASSERT(
        mbedtls_cipher_update( &invalid_ctx,
                               valid_buffer,
                               valid_size,
                               valid_buffer,
                               &size_t_var ) ==
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );

    /* mbedtls_cipher_finish() */
    TEST_ASSERT(
        mbedtls_cipher_finish( &invalid_ctx,
                               valid_buffer,
                               &size_t_var ) ==
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );

#if defined(MBEDTLS_GCM_C) || defined(MBEDTLS_CHACHAPOLY_C)
    /* mbedtls_cipher_write_tag() */
    TEST_ASSERT(
        mbedtls_cipher_write_tag( &invalid_ctx,
                                  valid_buffer,
                                  valid_size ) ==
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );

    /* mbedtls_cipher_check_tag() */
    TEST_ASSERT(
        mbedtls_cipher_check_tag( &invalid_ctx,
                                  valid_buffer,
                                  valid_size ) ==
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );
#endif /* defined(MBEDTLS_GCM_C) || defined(MBEDTLS_CHACHAPOLY_C) */

exit:
    mbedtls_cipher_free( &invalid_ctx );
    mbedtls_cipher_free( &valid_ctx );
}
/* END_CASE */

/* BEGIN_CASE depends_on:MBEDTLS_CHECK_PARAMS:!MBEDTLS_PARAM_FAILED_ALT */
void cipher_invalid_param_conditional( )
{
    mbedtls_cipher_context_t valid_ctx;

    mbedtls_operation_t valid_operation = MBEDTLS_ENCRYPT;
    mbedtls_operation_t invalid_operation = 100;
    mbedtls_cipher_padding_t valid_mode = MBEDTLS_PADDING_ZEROS;
    unsigned char valid_buffer[] = { 0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07 };
    int valid_size = sizeof(valid_buffer);
    int valid_bitlen = valid_size * 8;
    const mbedtls_cipher_info_t *valid_info = mbedtls_cipher_info_from_type(
        *( mbedtls_cipher_list() ) );

    size_t size_t_var;

    (void)valid_mode; /* In some configurations this is unused */

    /* mbedtls_cipher_init() */
    TEST_VALID_PARAM( mbedtls_cipher_init( &valid_ctx ) );
    TEST_INVALID_PARAM( mbedtls_cipher_init( NULL ) );

    /* mbedtls_cipher_setup() */
    TEST_VALID_PARAM( mbedtls_cipher_setup( &valid_ctx, valid_info ) );
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_setup( NULL, valid_info ) );

    /* mbedtls_cipher_get_block_size() */
    TEST_INVALID_PARAM_RET( 0, mbedtls_cipher_get_block_size( NULL ) );

    /* mbedtls_cipher_get_cipher_mode() */
    TEST_INVALID_PARAM_RET(
        MBEDTLS_MODE_NONE,
        mbedtls_cipher_get_cipher_mode( NULL ) );

    /* mbedtls_cipher_get_iv_size() */
    TEST_INVALID_PARAM_RET( 0, mbedtls_cipher_get_iv_size( NULL ) );

    /* mbedtls_cipher_get_type() */
    TEST_INVALID_PARAM_RET(
        MBEDTLS_CIPHER_NONE,
        mbedtls_cipher_get_type( NULL ) );

    /* mbedtls_cipher_get_name() */
    TEST_INVALID_PARAM_RET( 0, mbedtls_cipher_get_name( NULL ) );

    /* mbedtls_cipher_get_key_bitlen() */
    TEST_INVALID_PARAM_RET(
        MBEDTLS_KEY_LENGTH_NONE,
        mbedtls_cipher_get_key_bitlen( NULL ) );

    /* mbedtls_cipher_get_operation() */
    TEST_INVALID_PARAM_RET(
        MBEDTLS_OPERATION_NONE,
        mbedtls_cipher_get_operation( NULL ) );

    /* mbedtls_cipher_setkey() */
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_setkey( NULL,
                               valid_buffer,
                               valid_bitlen,
                               valid_operation ) );
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_setkey( &valid_ctx,
                               NULL,
                               valid_bitlen,
                               valid_operation ) );
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_setkey( &valid_ctx,
                               valid_buffer,
                               valid_bitlen,
                               invalid_operation ) );

    /* mbedtls_cipher_set_iv() */
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_set_iv( NULL,
                               valid_buffer,
                               valid_size ) );
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_set_iv( &valid_ctx,
                               NULL,
                               valid_size ) );

    /* mbedtls_cipher_reset() */
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
                            mbedtls_cipher_reset( NULL ) );

#if defined(MBEDTLS_GCM_C) || defined(MBEDTLS_CHACHAPOLY_C)
    /* mbedtls_cipher_update_ad() */
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_update_ad( NULL,
                                  valid_buffer,
                                  valid_size ) );
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_update_ad( &valid_ctx,
                                  NULL,
                                  valid_size ) );
#endif /* defined(MBEDTLS_GCM_C) || defined(MBEDTLS_CHACHAPOLY_C) */

#if defined(MBEDTLS_CIPHER_MODE_WITH_PADDING)
    /* mbedtls_cipher_set_padding_mode() */
    TEST_INVALID_PARAM_RET( MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
                            mbedtls_cipher_set_padding_mode( NULL, valid_mode ) );
#endif

    /* mbedtls_cipher_update() */
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_update( NULL,
                               valid_buffer,
                               valid_size,
                               valid_buffer,
                               &size_t_var ) );
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_update( &valid_ctx,
                               NULL, valid_size,
                               valid_buffer,
                               &size_t_var ) );
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_update( &valid_ctx,
                               valid_buffer, valid_size,
                               NULL,
                               &size_t_var ) );
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_update( &valid_ctx,
                               valid_buffer, valid_size,
                               valid_buffer,
                               NULL ) );

    /* mbedtls_cipher_finish() */
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_finish( NULL,
                               valid_buffer,
                               &size_t_var ) );
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_finish( &valid_ctx,
                               NULL,
                               &size_t_var ) );
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_finish( &valid_ctx,
                               valid_buffer,
                               NULL ) );

#if defined(MBEDTLS_GCM_C) || defined(MBEDTLS_CHACHAPOLY_C)
    /* mbedtls_cipher_write_tag() */
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_write_tag( NULL,
                                  valid_buffer,
                                  valid_size ) );
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_write_tag( &valid_ctx,
                                  NULL,
                                  valid_size ) );

    /* mbedtls_cipher_check_tag() */
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_check_tag( NULL,
                                  valid_buffer,
                                  valid_size ) );
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_check_tag( &valid_ctx,
                                  NULL,
                                  valid_size ) );
#endif /* defined(MBEDTLS_GCM_C) || defined(MBEDTLS_CHACHAPOLY_C) */

    /* mbedtls_cipher_crypt() */
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_crypt( NULL,
                              valid_buffer, valid_size,
                              valid_buffer, valid_size,
                              valid_buffer, &size_t_var ) );
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_crypt( &valid_ctx,
                              NULL, valid_size,
                              valid_buffer, valid_size,
                              valid_buffer, &size_t_var ) );
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_crypt( &valid_ctx,
                              valid_buffer, valid_size,
                              NULL, valid_size,
                              valid_buffer, &size_t_var ) );
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_crypt( &valid_ctx,
                              valid_buffer, valid_size,
                              valid_buffer, valid_size,
                              NULL, &size_t_var ) );
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_crypt( &valid_ctx,
                              valid_buffer, valid_size,
                              valid_buffer, valid_size,
                              valid_buffer, NULL ) );

#if defined(MBEDTLS_CIPHER_MODE_AEAD)
    /* mbedtls_cipher_auth_encrypt() */
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_auth_encrypt( NULL,
                                     valid_buffer, valid_size,
                                     valid_buffer, valid_size,
                                     valid_buffer, valid_size,
                                     valid_buffer, &size_t_var,
                                     valid_buffer, valid_size ) );
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_auth_encrypt( &valid_ctx,
                                     NULL, valid_size,
                                     valid_buffer, valid_size,
                                     valid_buffer, valid_size,
                                     valid_buffer, &size_t_var,
                                     valid_buffer, valid_size ) );
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_auth_encrypt( &valid_ctx,
                                     valid_buffer, valid_size,
                                     NULL, valid_size,
                                     valid_buffer, valid_size,
                                     valid_buffer, &size_t_var,
                                     valid_buffer, valid_size ) );
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_auth_encrypt( &valid_ctx,
                                     valid_buffer, valid_size,
                                     valid_buffer, valid_size,
                                     NULL, valid_size,
                                     valid_buffer, &size_t_var,
                                     valid_buffer, valid_size ) );
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_auth_encrypt( &valid_ctx,
                                     valid_buffer, valid_size,
                                     valid_buffer, valid_size,
                                     valid_buffer, valid_size,
                                     NULL, &size_t_var,
                                     valid_buffer, valid_size ) );
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_auth_encrypt( &valid_ctx,
                                     valid_buffer, valid_size,
                                     valid_buffer, valid_size,
                                     valid_buffer, valid_size,
                                     valid_buffer, NULL,
                                     valid_buffer, valid_size ) );
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_auth_encrypt( &valid_ctx,
                                     valid_buffer, valid_size,
                                     valid_buffer, valid_size,
                                     valid_buffer, valid_size,
                                     valid_buffer, &size_t_var,
                                     NULL, valid_size ) );

    /* mbedtls_cipher_auth_decrypt() */
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_auth_decrypt( NULL,
                                     valid_buffer, valid_size,
                                     valid_buffer, valid_size,
                                     valid_buffer, valid_size,
                                     valid_buffer, &size_t_var,
                                     valid_buffer, valid_size ) );
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_auth_decrypt( &valid_ctx,
                                     NULL, valid_size,
                                     valid_buffer, valid_size,
                                     valid_buffer, valid_size,
                                     valid_buffer, &size_t_var,
                                     valid_buffer, valid_size ) );
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_auth_decrypt( &valid_ctx,
                                     valid_buffer, valid_size,
                                     NULL, valid_size,
                                     valid_buffer, valid_size,
                                     valid_buffer, &size_t_var,
                                     valid_buffer, valid_size ) );
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_auth_decrypt( &valid_ctx,
                                     valid_buffer, valid_size,
                                     valid_buffer, valid_size,
                                     NULL, valid_size,
                                     valid_buffer, &size_t_var,
                                     valid_buffer, valid_size ) );
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_auth_decrypt( &valid_ctx,
                                     valid_buffer, valid_size,
                                     valid_buffer, valid_size,
                                     valid_buffer, valid_size,
                                     NULL, &size_t_var,
                                     valid_buffer, valid_size ) );
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_auth_decrypt( &valid_ctx,
                                     valid_buffer, valid_size,
                                     valid_buffer, valid_size,
                                     valid_buffer, valid_size,
                                     valid_buffer, NULL,
                                     valid_buffer, valid_size ) );
    TEST_INVALID_PARAM_RET(
        MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA,
        mbedtls_cipher_auth_decrypt( &valid_ctx,
                                     valid_buffer, valid_size,
                                     valid_buffer, valid_size,
                                     valid_buffer, valid_size,
                                     valid_buffer, &size_t_var,
                                     NULL, valid_size ) );
#endif /* defined(MBEDTLS_CIPHER_MODE_AEAD) */

    /* mbedtls_cipher_free() */
    TEST_VALID_PARAM( mbedtls_cipher_free( NULL ) );
exit:
    TEST_VALID_PARAM( mbedtls_cipher_free( &valid_ctx ) );
}
/* END_CASE */

/* BEGIN_CASE depends_on:MBEDTLS_AES_C */
void cipher_special_behaviours(  )
{
    const mbedtls_cipher_info_t *cipher_info;
    mbedtls_cipher_context_t ctx;
    unsigned char input[32];
    unsigned char output[32];
#if defined (MBEDTLS_CIPHER_MODE_CBC)
    unsigned char iv[32];
#endif
    size_t olen = 0;

    mbedtls_cipher_init( &ctx );
    memset( input, 0, sizeof( input ) );
    memset( output, 0, sizeof( output ) );
#if defined(MBEDTLS_CIPHER_MODE_CBC)
    memset( iv, 0, sizeof( iv ) );

    /* Check and get info structures */
    cipher_info = mbedtls_cipher_info_from_type( MBEDTLS_CIPHER_AES_128_CBC );
    TEST_ASSERT( NULL != cipher_info );

    TEST_ASSERT( 0 == mbedtls_cipher_setup( &ctx, cipher_info ) );

    /* IV too big */
    TEST_ASSERT( mbedtls_cipher_set_iv( &ctx, iv, MBEDTLS_MAX_IV_LENGTH + 1 )
                 == MBEDTLS_ERR_CIPHER_FEATURE_UNAVAILABLE );

    /* IV too small */
    TEST_ASSERT( mbedtls_cipher_set_iv( &ctx, iv, 0 )
                 == MBEDTLS_ERR_CIPHER_BAD_INPUT_DATA );

    mbedtls_cipher_free( &ctx );
    mbedtls_cipher_init( &ctx );
#endif /* MBEDTLS_CIPHER_MODE_CBC */
    cipher_info = mbedtls_cipher_info_from_type( MBEDTLS_CIPHER_AES_128_ECB );
    TEST_ASSERT( NULL != cipher_info );

    TEST_ASSERT( 0 == mbedtls_cipher_setup( &ctx, cipher_info ) );

    /* Update ECB with partial block */
    TEST_ASSERT( mbedtls_cipher_update( &ctx, input, 1, output, &olen )
                 == MBEDTLS_ERR_CIPHER_FULL_BLOCK_EXPECTED );

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

/* BEGIN_CASE */
void enc_dec_buf( int cipher_id, char * cipher_string, int key_len,
                  int length_val, int pad_mode )
{
    size_t length = length_val, outlen, total_len, i, block_size;
    unsigned char key[64];
    unsigned char iv[16];
    unsigned char ad[13];
    unsigned char tag[16];
    unsigned char inbuf[64];
    unsigned char encbuf[64];
    unsigned char decbuf[64];

    const mbedtls_cipher_info_t *cipher_info;
    mbedtls_cipher_context_t ctx_dec;
    mbedtls_cipher_context_t ctx_enc;

    /*
     * Prepare contexts
     */
    mbedtls_cipher_init( &ctx_dec );
    mbedtls_cipher_init( &ctx_enc );

    memset( key, 0x2a, sizeof( key ) );

    /* Check and get info structures */
    cipher_info = mbedtls_cipher_info_from_type( cipher_id );
    TEST_ASSERT( NULL != cipher_info );
    TEST_ASSERT( mbedtls_cipher_info_from_string( cipher_string ) == cipher_info );

    /* Initialise enc and dec contexts */
    TEST_ASSERT( 0 == mbedtls_cipher_setup( &ctx_dec, cipher_info ) );
    TEST_ASSERT( 0 == mbedtls_cipher_setup( &ctx_enc, cipher_info ) );

    TEST_ASSERT( 0 == mbedtls_cipher_setkey( &ctx_dec, key, key_len, MBEDTLS_DECRYPT ) );
    TEST_ASSERT( 0 == mbedtls_cipher_setkey( &ctx_enc, key, key_len, MBEDTLS_ENCRYPT ) );

#if defined(MBEDTLS_CIPHER_MODE_WITH_PADDING)
    if( -1 != pad_mode )
    {
        TEST_ASSERT( 0 == mbedtls_cipher_set_padding_mode( &ctx_dec, pad_mode ) );
        TEST_ASSERT( 0 == mbedtls_cipher_set_padding_mode( &ctx_enc, pad_mode ) );
    }
#else
    (void) pad_mode;
#endif /* MBEDTLS_CIPHER_MODE_WITH_PADDING */

    /*
     * Do a few encode/decode cycles
     */
    for( i = 0; i < 3; i++ )
    {
    memset( iv , 0x00 + i, sizeof( iv ) );
    memset( ad, 0x10 + i, sizeof( ad ) );
    memset( inbuf, 0x20 + i, sizeof( inbuf ) );

    memset( encbuf, 0, sizeof( encbuf ) );
    memset( decbuf, 0, sizeof( decbuf ) );
    memset( tag, 0, sizeof( tag ) );

    TEST_ASSERT( 0 == mbedtls_cipher_set_iv( &ctx_dec, iv, sizeof( iv ) ) );
    TEST_ASSERT( 0 == mbedtls_cipher_set_iv( &ctx_enc, iv, sizeof( iv ) ) );

    TEST_ASSERT( 0 == mbedtls_cipher_reset( &ctx_dec ) );
    TEST_ASSERT( 0 == mbedtls_cipher_reset( &ctx_enc ) );

#if defined(MBEDTLS_GCM_C) || defined(MBEDTLS_CHACHAPOLY_C)
    TEST_ASSERT( 0 == mbedtls_cipher_update_ad( &ctx_dec, ad, sizeof( ad ) - i ) );
    TEST_ASSERT( 0 == mbedtls_cipher_update_ad( &ctx_enc, ad, sizeof( ad ) - i ) );
#endif

    block_size = mbedtls_cipher_get_block_size( &ctx_enc );
    TEST_ASSERT( block_size != 0 );

    /* encode length number of bytes from inbuf */
    TEST_ASSERT( 0 == mbedtls_cipher_update( &ctx_enc, inbuf, length, encbuf, &outlen ) );
    total_len = outlen;

    TEST_ASSERT( total_len == length ||
                 ( total_len % block_size == 0 &&
                   total_len < length &&
                   total_len + block_size > length ) );

    TEST_ASSERT( 0 == mbedtls_cipher_finish( &ctx_enc, encbuf + outlen, &outlen ) );
    total_len += outlen;

#if defined(MBEDTLS_GCM_C) || defined(MBEDTLS_CHACHAPOLY_C)
    TEST_ASSERT( 0 == mbedtls_cipher_write_tag( &ctx_enc, tag, sizeof( tag ) ) );
#endif

    TEST_ASSERT( total_len == length ||
                 ( total_len % block_size == 0 &&
                   total_len > length &&
                   total_len <= length + block_size ) );

    /* decode the previously encoded string */
    TEST_ASSERT( 0 == mbedtls_cipher_update( &ctx_dec, encbuf, total_len, decbuf, &outlen ) );
    total_len = outlen;

    TEST_ASSERT( total_len == length ||
                 ( total_len % block_size == 0 &&
                   total_len < length &&
                   total_len + block_size >= length ) );

    TEST_ASSERT( 0 == mbedtls_cipher_finish( &ctx_dec, decbuf + outlen, &outlen ) );
    total_len += outlen;

#if defined(MBEDTLS_GCM_C) || defined(MBEDTLS_CHACHAPOLY_C)
    TEST_ASSERT( 0 == mbedtls_cipher_check_tag( &ctx_dec, tag, sizeof( tag ) ) );
#endif

    /* check result */
    TEST_ASSERT( total_len == length );
    TEST_ASSERT( 0 == memcmp(inbuf, decbuf, length) );
    }

    /*
     * Done
     */
exit:
    mbedtls_cipher_free( &ctx_dec );
    mbedtls_cipher_free( &ctx_enc );
}
/* END_CASE */

/* BEGIN_CASE */
void enc_fail( int cipher_id, int pad_mode, int key_len, int length_val,
               int ret )
{
    size_t length = length_val;
    unsigned char key[32];
    unsigned char iv[16];

    const mbedtls_cipher_info_t *cipher_info;
    mbedtls_cipher_context_t ctx;

    unsigned char inbuf[64];
    unsigned char encbuf[64];

    size_t outlen = 0;

    memset( key, 0, 32 );
    memset( iv , 0, 16 );

    mbedtls_cipher_init( &ctx );

    memset( inbuf, 5, 64 );
    memset( encbuf, 0, 64 );

    /* Check and get info structures */
    cipher_info = mbedtls_cipher_info_from_type( cipher_id );
    TEST_ASSERT( NULL != cipher_info );

    /* Initialise context */
    TEST_ASSERT( 0 == mbedtls_cipher_setup( &ctx, cipher_info ) );
    TEST_ASSERT( 0 == mbedtls_cipher_setkey( &ctx, key, key_len, MBEDTLS_ENCRYPT ) );
#if defined(MBEDTLS_CIPHER_MODE_WITH_PADDING)
    TEST_ASSERT( 0 == mbedtls_cipher_set_padding_mode( &ctx, pad_mode ) );
#else
    (void) pad_mode;
#endif /* MBEDTLS_CIPHER_MODE_WITH_PADDING */
    TEST_ASSERT( 0 == mbedtls_cipher_set_iv( &ctx, iv, 16 ) );
    TEST_ASSERT( 0 == mbedtls_cipher_reset( &ctx ) );
#if defined(MBEDTLS_GCM_C) || defined(MBEDTLS_CHACHAPOLY_C)
    TEST_ASSERT( 0 == mbedtls_cipher_update_ad( &ctx, NULL, 0 ) );
#endif

    /* encode length number of bytes from inbuf */
    TEST_ASSERT( 0 == mbedtls_cipher_update( &ctx, inbuf, length, encbuf, &outlen ) );
    TEST_ASSERT( ret == mbedtls_cipher_finish( &ctx, encbuf + outlen, &outlen ) );

    /* done */
exit:
    mbedtls_cipher_free( &ctx );
}
/* END_CASE */

/* BEGIN_CASE */
void dec_empty_buf( int cipher )
{
    unsigned char key[32];
    unsigned char iv[16];

    mbedtls_cipher_context_t ctx_dec;
    const mbedtls_cipher_info_t *cipher_info;

    unsigned char encbuf[64];
    unsigned char decbuf[64];

    size_t outlen = 0;

    int expected_ret;

    memset( key, 0, 32 );
    memset( iv , 0, 16 );

    mbedtls_cipher_init( &ctx_dec );

    memset( encbuf, 0, 64 );
    memset( decbuf, 0, 64 );

    /* Initialise context */
    cipher_info = mbedtls_cipher_info_from_type( cipher );
    TEST_ASSERT( NULL != cipher_info);
    TEST_ASSERT( sizeof(key) * 8 >= cipher_info->key_bitlen );

    TEST_ASSERT( 0 == mbedtls_cipher_setup( &ctx_dec, cipher_info ) );

    TEST_ASSERT( 0 == mbedtls_cipher_setkey( &ctx_dec,
                                             key, cipher_info->key_bitlen,
                                             MBEDTLS_DECRYPT ) );

    TEST_ASSERT( 0 == mbedtls_cipher_set_iv( &ctx_dec, iv, 16 ) );

    TEST_ASSERT( 0 == mbedtls_cipher_reset( &ctx_dec ) );

#if defined(MBEDTLS_GCM_C) || defined(MBEDTLS_CHACHAPOLY_C)
    TEST_ASSERT( 0 == mbedtls_cipher_update_ad( &ctx_dec, NULL, 0 ) );
#endif

    /* decode 0-byte string */
    TEST_ASSERT( 0 == mbedtls_cipher_update( &ctx_dec, encbuf, 0, decbuf, &outlen ) );
    TEST_ASSERT( 0 == outlen );

    if ( cipher_info->mode == MBEDTLS_MODE_CBC ||
         cipher_info->mode == MBEDTLS_MODE_ECB )
    {
        /* CBC and ECB ciphers need a full block of input. */
        expected_ret = MBEDTLS_ERR_CIPHER_FULL_BLOCK_EXPECTED;
    }
    else
    {
        /* Non-CBC and non-ECB ciphers are OK with decrypting empty buffers and
         * return success, not MBEDTLS_ERR_CIPHER_FULL_BLOCK_EXPECTED, when
         * decrypting an empty buffer. */
        expected_ret = 0;
    }

    TEST_ASSERT( expected_ret == mbedtls_cipher_finish(
                                    &ctx_dec, decbuf + outlen, &outlen ) );
    TEST_ASSERT( 0 == outlen );

exit:
    mbedtls_cipher_free( &ctx_dec );
}
/* END_CASE */

/* BEGIN_CASE */
void enc_dec_buf_multipart( int cipher_id, int key_len, int first_length_val,
                            int second_length_val, int pad_mode,
                            int first_encrypt_output_len, int second_encrypt_output_len,
                            int first_decrypt_output_len, int second_decrypt_output_len )
{
    size_t first_length = first_length_val;
    size_t second_length = second_length_val;
    size_t length = first_length + second_length;
    size_t block_size;
    unsigned char key[32];
    unsigned char iv[16];

    mbedtls_cipher_context_t ctx_dec;
    mbedtls_cipher_context_t ctx_enc;
    const mbedtls_cipher_info_t *cipher_info;

    unsigned char inbuf[64];
    unsigned char encbuf[64];
    unsigned char decbuf[64];

    size_t outlen = 0;
    size_t totaloutlen = 0;

    memset( key, 0, 32 );
    memset( iv , 0, 16 );

    mbedtls_cipher_init( &ctx_dec );
    mbedtls_cipher_init( &ctx_enc );

    memset( inbuf, 5, 64 );
    memset( encbuf, 0, 64 );
    memset( decbuf, 0, 64 );

    /* Initialise enc and dec contexts */
    cipher_info = mbedtls_cipher_info_from_type( cipher_id );
    TEST_ASSERT( NULL != cipher_info);

    TEST_ASSERT( 0 == mbedtls_cipher_setup( &ctx_dec, cipher_info ) );
    TEST_ASSERT( 0 == mbedtls_cipher_setup( &ctx_enc, cipher_info ) );

    TEST_ASSERT( 0 == mbedtls_cipher_setkey( &ctx_dec, key, key_len, MBEDTLS_DECRYPT ) );
    TEST_ASSERT( 0 == mbedtls_cipher_setkey( &ctx_enc, key, key_len, MBEDTLS_ENCRYPT ) );

#if defined(MBEDTLS_CIPHER_MODE_WITH_PADDING)
    if( -1 != pad_mode )
    {
        TEST_ASSERT( 0 == mbedtls_cipher_set_padding_mode( &ctx_dec, pad_mode ) );
        TEST_ASSERT( 0 == mbedtls_cipher_set_padding_mode( &ctx_enc, pad_mode ) );
    }
#else
    (void) pad_mode;
#endif /* MBEDTLS_CIPHER_MODE_WITH_PADDING */

    TEST_ASSERT( 0 == mbedtls_cipher_set_iv( &ctx_dec, iv, 16 ) );
    TEST_ASSERT( 0 == mbedtls_cipher_set_iv( &ctx_enc, iv, 16 ) );

    TEST_ASSERT( 0 == mbedtls_cipher_reset( &ctx_dec ) );
    TEST_ASSERT( 0 == mbedtls_cipher_reset( &ctx_enc ) );

#if defined(MBEDTLS_GCM_C) || defined(MBEDTLS_CHACHAPOLY_C)
    TEST_ASSERT( 0 == mbedtls_cipher_update_ad( &ctx_dec, NULL, 0 ) );
    TEST_ASSERT( 0 == mbedtls_cipher_update_ad( &ctx_enc, NULL, 0 ) );
#endif

    block_size = mbedtls_cipher_get_block_size( &ctx_enc );
    TEST_ASSERT( block_size != 0 );

    /* encode length number of bytes from inbuf */
    TEST_ASSERT( 0 == mbedtls_cipher_update( &ctx_enc, inbuf, first_length, encbuf, &outlen ) );
    TEST_ASSERT( (size_t)first_encrypt_output_len == outlen );
    totaloutlen = outlen;
    TEST_ASSERT( 0 == mbedtls_cipher_update( &ctx_enc, inbuf + first_length, second_length, encbuf + totaloutlen, &outlen ) );
    TEST_ASSERT( (size_t)second_encrypt_output_len == outlen );
    totaloutlen += outlen;
    TEST_ASSERT( totaloutlen == length ||
                 ( totaloutlen % block_size == 0 &&
                   totaloutlen < length &&
                   totaloutlen + block_size > length ) );

    TEST_ASSERT( 0 == mbedtls_cipher_finish( &ctx_enc, encbuf + totaloutlen, &outlen ) );
    totaloutlen += outlen;
    TEST_ASSERT( totaloutlen == length ||
                 ( totaloutlen % block_size == 0 &&
                   totaloutlen > length &&
                   totaloutlen <= length + block_size ) );

    /* decode the previously encoded string */
    second_length = totaloutlen - first_length;
    TEST_ASSERT( 0 == mbedtls_cipher_update( &ctx_dec, encbuf, first_length, decbuf, &outlen ) );
    TEST_ASSERT( (size_t)first_decrypt_output_len == outlen );
    totaloutlen = outlen;
    TEST_ASSERT( 0 == mbedtls_cipher_update( &ctx_dec, encbuf + first_length, second_length, decbuf + totaloutlen, &outlen ) );
    TEST_ASSERT( (size_t)second_decrypt_output_len == outlen );
    totaloutlen += outlen;

    TEST_ASSERT( totaloutlen == length ||
                 ( totaloutlen % block_size == 0 &&
                   totaloutlen < length &&
                   totaloutlen + block_size >= length ) );

    TEST_ASSERT( 0 == mbedtls_cipher_finish( &ctx_dec, decbuf + totaloutlen, &outlen ) );
    totaloutlen += outlen;

    TEST_ASSERT( totaloutlen == length );

    TEST_ASSERT( 0 == memcmp(inbuf, decbuf, length) );

exit:
    mbedtls_cipher_free( &ctx_dec );
    mbedtls_cipher_free( &ctx_enc );
}
/* END_CASE */

/* BEGIN_CASE */
void decrypt_test_vec( int cipher_id, int pad_mode, data_t * key,
                       data_t * iv, data_t * cipher,
                       data_t * clear, data_t * ad, data_t * tag,
                       int finish_result, int tag_result )
{
    unsigned char output[265];
    mbedtls_cipher_context_t ctx;
    size_t outlen, total_len;

    mbedtls_cipher_init( &ctx );

    memset( output, 0x00, sizeof( output ) );

#if !defined(MBEDTLS_GCM_C) && !defined(MBEDTLS_CHACHAPOLY_C)
    ((void) ad);
    ((void) tag);
#endif

    /* Prepare context */
    TEST_ASSERT( 0 == mbedtls_cipher_setup( &ctx,
                                       mbedtls_cipher_info_from_type( cipher_id ) ) );
    TEST_ASSERT( 0 == mbedtls_cipher_setkey( &ctx, key->x, 8 * key->len, MBEDTLS_DECRYPT ) );
#if defined(MBEDTLS_CIPHER_MODE_WITH_PADDING)
    if( pad_mode != -1 )
        TEST_ASSERT( 0 == mbedtls_cipher_set_padding_mode( &ctx, pad_mode ) );
#else
    (void) pad_mode;
#endif /* MBEDTLS_CIPHER_MODE_WITH_PADDING */
    TEST_ASSERT( 0 == mbedtls_cipher_set_iv( &ctx, iv->x, iv->len ) );
    TEST_ASSERT( 0 == mbedtls_cipher_reset( &ctx ) );
#if defined(MBEDTLS_GCM_C) || defined(MBEDTLS_CHACHAPOLY_C)
    TEST_ASSERT( 0 == mbedtls_cipher_update_ad( &ctx, ad->x, ad->len ) );
#endif

    /* decode buffer and check tag->x */
    total_len = 0;
    TEST_ASSERT( 0 == mbedtls_cipher_update( &ctx, cipher->x, cipher->len, output, &outlen ) );
    total_len += outlen;
    TEST_ASSERT( finish_result == mbedtls_cipher_finish( &ctx, output + outlen,
                                                 &outlen ) );
    total_len += outlen;
#if defined(MBEDTLS_GCM_C) || defined(MBEDTLS_CHACHAPOLY_C)
    TEST_ASSERT( tag_result == mbedtls_cipher_check_tag( &ctx, tag->x, tag->len ) );
#endif

    /* check plaintext only if everything went fine */
    if( 0 == finish_result && 0 == tag_result )
    {
        TEST_ASSERT( total_len == clear->len );
        TEST_ASSERT( 0 == memcmp( output, clear->x, clear->len ) );
    }

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

/* BEGIN_CASE depends_on:MBEDTLS_CIPHER_MODE_AEAD */
void auth_crypt_tv( int cipher_id, data_t * key, data_t * iv,
                    data_t * ad, data_t * cipher, data_t * tag,
                    char * result, data_t * clear )
{
    int ret;
    unsigned char output[267]; /* above + 2 (overwrite check) */
    unsigned char my_tag[20];
    mbedtls_cipher_context_t ctx;
    size_t outlen;

    mbedtls_cipher_init( &ctx );

    memset( output, 0xFF, sizeof( output ) );
    memset( my_tag, 0xFF, sizeof( my_tag ) );


    /* Prepare context */
    TEST_ASSERT( 0 == mbedtls_cipher_setup( &ctx,
                                       mbedtls_cipher_info_from_type( cipher_id ) ) );
    TEST_ASSERT( 0 == mbedtls_cipher_setkey( &ctx, key->x, 8 * key->len, MBEDTLS_DECRYPT ) );

    /* decode buffer and check tag->x */
    ret = mbedtls_cipher_auth_decrypt( &ctx, iv->x, iv->len, ad->x, ad->len,
                               cipher->x, cipher->len, output, &outlen,
                               tag->x, tag->len );

    /* make sure we didn't overwrite */
    TEST_ASSERT( output[outlen + 0] == 0xFF );
    TEST_ASSERT( output[outlen + 1] == 0xFF );

    /* make sure the message is rejected if it should be */
    if( strcmp( result, "FAIL" ) == 0 )
    {
        TEST_ASSERT( ret == MBEDTLS_ERR_CIPHER_AUTH_FAILED );
        goto exit;
    }

    /* otherwise, make sure it was decrypted properly */
    TEST_ASSERT( ret == 0 );

    TEST_ASSERT( outlen == clear->len );
    TEST_ASSERT( memcmp( output, clear->x, clear->len ) == 0 );

    /* then encrypt the clear->x and make sure we get the same ciphertext and tag->x */
    TEST_ASSERT( 0 == mbedtls_cipher_setkey( &ctx, key->x, 8 * key->len,
                                             MBEDTLS_ENCRYPT ) );

    memset( output, 0xFF, sizeof( output ) );
    outlen = 0;

    ret = mbedtls_cipher_auth_encrypt( &ctx, iv->x, iv->len, ad->x, ad->len,
                               clear->x, clear->len, output, &outlen,
                               my_tag, tag->len );
    TEST_ASSERT( ret == 0 );

    TEST_ASSERT( outlen == cipher->len );
    TEST_ASSERT( memcmp( output, cipher->x, cipher->len ) == 0 );
    TEST_ASSERT( memcmp( my_tag, tag->x, tag->len ) == 0 );

    /* make sure we didn't overwrite */
    TEST_ASSERT( output[outlen + 0] == 0xFF );
    TEST_ASSERT( output[outlen + 1] == 0xFF );
    TEST_ASSERT( my_tag[tag->len + 0] == 0xFF );
    TEST_ASSERT( my_tag[tag->len + 1] == 0xFF );


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

/* BEGIN_CASE */
void test_vec_ecb( int cipher_id, int operation, data_t * key,
                   data_t * input, data_t * result, int finish_result
                   )
{
    mbedtls_cipher_context_t ctx;
    unsigned char output[32];
    size_t outlen;

    mbedtls_cipher_init( &ctx );

    memset( output, 0x00, sizeof( output ) );

    /* Prepare context */
    TEST_ASSERT( 0 == mbedtls_cipher_setup( &ctx,
                                       mbedtls_cipher_info_from_type( cipher_id ) ) );


    TEST_ASSERT( 0 == mbedtls_cipher_setkey( &ctx, key->x, 8 * key->len, operation ) );

    TEST_ASSERT( 0 == mbedtls_cipher_update( &ctx, input->x,
                                     mbedtls_cipher_get_block_size( &ctx ),
                                     output, &outlen ) );
    TEST_ASSERT( outlen == mbedtls_cipher_get_block_size( &ctx ) );
    TEST_ASSERT( finish_result == mbedtls_cipher_finish( &ctx, output + outlen,
                                                 &outlen ) );
    TEST_ASSERT( 0 == outlen );

    /* check plaintext only if everything went fine */
    if( 0 == finish_result )
        TEST_ASSERT( 0 == memcmp( output, result->x,
                                  mbedtls_cipher_get_block_size( &ctx ) ) );

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

/* BEGIN_CASE depends_on:MBEDTLS_CIPHER_MODE_WITH_PADDING */
void test_vec_crypt( int cipher_id, int operation, data_t *key,
                     data_t *iv, data_t *input, data_t *result,
                     int finish_result )
{
    mbedtls_cipher_context_t ctx;
    unsigned char output[32];
    size_t outlen;

    mbedtls_cipher_init( &ctx );

    memset( output, 0x00, sizeof( output ) );

    /* Prepare context */
    TEST_ASSERT( 0 == mbedtls_cipher_setup( &ctx,
                                       mbedtls_cipher_info_from_type( cipher_id ) ) );

    TEST_ASSERT( 0 == mbedtls_cipher_setkey( &ctx, key->x, 8 * key->len, operation ) );
    if( MBEDTLS_MODE_CBC == ctx.cipher_info->mode )
        TEST_ASSERT( 0 == mbedtls_cipher_set_padding_mode( &ctx, MBEDTLS_PADDING_NONE ) );

    TEST_ASSERT( finish_result == mbedtls_cipher_crypt( &ctx, iv->len ? iv->x : NULL,
                                                        iv->len, input->x, input->len,
                                                        output, &outlen ) );
    TEST_ASSERT( result->len == outlen );
    /* check plaintext only if everything went fine */
    if( 0 == finish_result )
        TEST_ASSERT( 0 == memcmp( output, result->x, outlen ) );

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

/* BEGIN_CASE depends_on:MBEDTLS_CIPHER_MODE_WITH_PADDING */
void set_padding( int cipher_id, int pad_mode, int ret )
{
    const mbedtls_cipher_info_t *cipher_info;
    mbedtls_cipher_context_t ctx;

    mbedtls_cipher_init( &ctx );

    cipher_info = mbedtls_cipher_info_from_type( cipher_id );
    TEST_ASSERT( NULL != cipher_info );
    TEST_ASSERT( 0 == mbedtls_cipher_setup( &ctx, cipher_info ) );

    TEST_ASSERT( ret == mbedtls_cipher_set_padding_mode( &ctx, pad_mode ) );

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

/* BEGIN_CASE depends_on:MBEDTLS_CIPHER_MODE_CBC */
void check_padding( int pad_mode, data_t * input, int ret, int dlen_check
                    )
{
    mbedtls_cipher_info_t cipher_info;
    mbedtls_cipher_context_t ctx;
    size_t dlen;

    /* build a fake context just for getting access to get_padding */
    mbedtls_cipher_init( &ctx );
    cipher_info.mode = MBEDTLS_MODE_CBC;
    ctx.cipher_info = &cipher_info;

    TEST_ASSERT( 0 == mbedtls_cipher_set_padding_mode( &ctx, pad_mode ) );


    TEST_ASSERT( ret == ctx.get_padding( input->x, input->len, &dlen ) );
    if( 0 == ret )
        TEST_ASSERT( dlen == (size_t) dlen_check );
}
/* END_CASE */