mbedtls/tests/suites/test_suite_mps.function

/* BEGIN_HEADER */

#include <stdlib.h>

#include "mps_reader.h"

/*
 * Compile-time configuration for test suite.
 */

/* Comment/Uncomment this to disable/enable the
 * testing of the various MPS layers.
 * This can be useful for time-consuming instrumentation
 * tasks such as the conversion of E-ACSL annotations
 * into runtime assertions. */
#define TEST_SUITE_MPS_READER

/* End of compile-time configuration. */

/* END_HEADER */

/* BEGIN_DEPENDENCIES
 * depends_on:MBEDTLS_SSL_PROTO_TLS1_3
 * END_DEPENDENCIES
 */

/* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER */
void mbedtls_mps_reader_no_pausing_single_step_single_round(int with_acc)
{
    /* This test exercises the most basic use of the MPS reader:
     * - The 'producing' layer provides a buffer
     * - The 'consuming' layer fetches it in a single go.
     * - After processing, the consuming layer commits the data
     *   and the reader is moved back to producing mode.
     *
     * Parameters:
     * - with_acc: 0 if the reader should be initialized without accumulator.
     *             1 if the reader should be initialized with accumulator.
     *
     *             Whether the accumulator is present or not should not matter,
     *             since the consumer's request can be fulfilled from the data
     *             that the producer has provided.
     */
    unsigned char bufA[100];
    unsigned char acc[10];
    unsigned char *tmp;
    int paused;
    mbedtls_mps_reader rd;
    for (size_t i = 0; (unsigned) i < sizeof(bufA); i++) {
        bufA[i] = (unsigned char) i;
    }

    /* Preparation (lower layer) */
    if (with_acc == 0) {
        mbedtls_mps_reader_init(&rd, NULL, 0);
    } else {
        mbedtls_mps_reader_init(&rd, acc, sizeof(acc));
    }
    TEST_ASSERT(mbedtls_mps_reader_feed(&rd, bufA, sizeof(bufA)) == 0);
    /* Consumption (upper layer) */
    /* Consume exactly what's available */
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 100, &tmp, NULL) == 0);
    ASSERT_COMPARE(tmp, 100, bufA, 100);
    TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);
    /* Wrapup (lower layer) */
    TEST_ASSERT(mbedtls_mps_reader_reclaim(&rd, &paused) == 0);
    TEST_ASSERT(paused == 0);
    mbedtls_mps_reader_free(&rd);
}
/* END_CASE */

/* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER */
void mbedtls_mps_reader_no_pausing_single_step_multiple_rounds(int with_acc)
{
    /* This test exercises multiple rounds of the basic use of the MPS reader:
     * - The 'producing' layer provides a buffer
     * - The 'consuming' layer fetches it in a single go.
     * - After processing, the consuming layer commits the data
     *   and the reader is moved back to producing mode.
     *
     * Parameters:
     * - with_acc: 0 if the reader should be initialized without accumulator.
     *             1 if the reader should be initialized with accumulator.
     *
     *             Whether the accumulator is present or not should not matter,
     *             since the consumer's request can be fulfilled from the data
     *             that the producer has provided.
     */

    unsigned char bufA[100], bufB[100];
    unsigned char acc[10];
    unsigned char *tmp;
    mbedtls_mps_reader rd;
    for (size_t i = 0; (unsigned) i < sizeof(bufA); i++) {
        bufA[i] = (unsigned char) i;
    }
    for (size_t i = 0; (unsigned) i < sizeof(bufB); i++) {
        bufB[i] = ~((unsigned char) i);
    }

    /* Preparation (lower layer) */
    if (with_acc == 0) {
        mbedtls_mps_reader_init(&rd, NULL, 0);
    } else {
        mbedtls_mps_reader_init(&rd, acc, sizeof(acc));
    }
    TEST_ASSERT(mbedtls_mps_reader_feed(&rd, bufA, sizeof(bufA)) == 0);
    /* Consumption (upper layer) */
    /* Consume exactly what's available */
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 100, &tmp, NULL) == 0);
    ASSERT_COMPARE(tmp, 100, bufA, 100);
    TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);
    /* Preparation */
    TEST_ASSERT(mbedtls_mps_reader_reclaim(&rd, NULL) == 0);
    TEST_ASSERT(mbedtls_mps_reader_feed(&rd, bufB, sizeof(bufB)) == 0);
    /* Consumption */
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 100, &tmp, NULL) == 0);
    ASSERT_COMPARE(tmp, 100, bufB, 100);
    TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);
    /* Wrapup (lower layer) */
    TEST_ASSERT(mbedtls_mps_reader_reclaim(&rd, NULL) == 0);
    mbedtls_mps_reader_free(&rd);
}
/* END_CASE */

/* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER */
void mbedtls_mps_reader_no_pausing_multiple_steps_single_round(int with_acc)
{
    /* This test exercises one round of the following:
     * - The 'producing' layer provides a buffer
     * - The 'consuming' layer fetches it in multiple calls
     *   to `mbedtls_mps_reader_get()`, without committing in between.
     * - After processing, the consuming layer commits the data
     *   and the reader is moved back to producing mode.
     *
     * Parameters:
     * - with_acc: 0 if the reader should be initialized without accumulator.
     *             1 if the reader should be initialized with accumulator.
     *
     *             Whether the accumulator is present or not should not matter,
     *             since the consumer's requests can be fulfilled from the data
     *             that the producer has provided.
     */

    /* Lower layer provides data that the upper layer fully consumes
     * through multiple `get` calls. */
    unsigned char buf[100];
    unsigned char acc[10];
    unsigned char *tmp;
    mbedtls_mps_size_t tmp_len;
    mbedtls_mps_reader rd;
    for (size_t i = 0; (unsigned) i < sizeof(buf); i++) {
        buf[i] = (unsigned char) i;
    }

    /* Preparation (lower layer) */
    if (with_acc == 0) {
        mbedtls_mps_reader_init(&rd, NULL, 0);
    } else {
        mbedtls_mps_reader_init(&rd, acc, sizeof(acc));
    }
    TEST_ASSERT(mbedtls_mps_reader_feed(&rd, buf, sizeof(buf)) == 0);
    /* Consumption (upper layer) */
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 10, &tmp, NULL) == 0);
    ASSERT_COMPARE(tmp, 10, buf, 10);
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 70, &tmp, NULL) == 0);
    ASSERT_COMPARE(tmp, 70, buf + 10, 70);
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 30, &tmp, &tmp_len) == 0);
    ASSERT_COMPARE(tmp, tmp_len, buf + 80, 20);
    TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);
    /* Wrapup (lower layer) */
    TEST_ASSERT(mbedtls_mps_reader_reclaim(&rd, NULL) == 0);
    mbedtls_mps_reader_free(&rd);
}
/* END_CASE */

/* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER */
void mbedtls_mps_reader_no_pausing_multiple_steps_multiple_rounds(int with_acc)
{
    /* This test exercises one round of fetching a buffer in multiple chunks
     * and passing it back to the producer afterwards, followed by another
     * single-step sequence of feed-fetch-commit-reclaim.
     */
    unsigned char bufA[100], bufB[100];
    unsigned char acc[10];
    unsigned char *tmp;
    mbedtls_mps_size_t tmp_len;
    mbedtls_mps_reader rd;
    for (size_t i = 0; (unsigned) i < sizeof(bufA); i++) {
        bufA[i] = (unsigned char) i;
    }
    for (size_t i = 0; (unsigned) i < sizeof(bufB); i++) {
        bufB[i] = ~((unsigned char) i);
    }

    /* Preparation (lower layer) */
    if (with_acc == 0) {
        mbedtls_mps_reader_init(&rd, NULL, 0);
    } else {
        mbedtls_mps_reader_init(&rd, acc, sizeof(acc));
    }
    TEST_ASSERT(mbedtls_mps_reader_feed(&rd, bufA, sizeof(bufA)) == 0);
    /* Consumption (upper layer) */
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 10, &tmp, NULL) == 0);
    ASSERT_COMPARE(tmp, 10, bufA, 10);
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 70, &tmp, NULL) == 0);
    ASSERT_COMPARE(tmp, 70, bufA + 10, 70);
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 30, &tmp, &tmp_len) == 0);
    ASSERT_COMPARE(tmp, tmp_len, bufA + 80, 20);
    TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);
    /* Preparation */
    TEST_ASSERT(mbedtls_mps_reader_reclaim(&rd, NULL) == 0);
    TEST_ASSERT(mbedtls_mps_reader_feed(&rd, bufB, sizeof(bufB)) == 0);
    /* Consumption */
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 100, &tmp, NULL) == 0);
    ASSERT_COMPARE(tmp, 100, bufB, 100);
    TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);
    /* Wrapup */
    TEST_ASSERT(mbedtls_mps_reader_reclaim(&rd, NULL) == 0);
    mbedtls_mps_reader_free(&rd);
}
/* END_CASE */

/* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER */
void mbedtls_mps_reader_pausing_needed_disabled()
{
    /* This test exercises the behaviour of the MPS reader when a read request
     * of the consumer exceeds what has been provided by the producer, and when
     * no accumulator is available in the reader.
     *
     * In this case, we expect the reader to fail.
     */

    unsigned char buf[100];
    unsigned char *tmp;
    mbedtls_mps_reader rd;
    for (size_t i = 0; (unsigned) i < sizeof(buf); i++) {
        buf[i] = (unsigned char) i;
    }

    /* Preparation (lower layer) */
    mbedtls_mps_reader_init(&rd, NULL, 0);
    TEST_ASSERT(mbedtls_mps_reader_feed(&rd, buf, sizeof(buf)) == 0);
    /* Consumption (upper layer) */
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 50, &tmp, NULL) == 0);
    ASSERT_COMPARE(tmp, 50, buf, 50);
    TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 100, &tmp, NULL) ==
                MBEDTLS_ERR_MPS_READER_OUT_OF_DATA);
    /* Wrapup (lower layer) */
    TEST_ASSERT(mbedtls_mps_reader_reclaim(&rd, NULL) ==
                MBEDTLS_ERR_MPS_READER_NEED_ACCUMULATOR);
    mbedtls_mps_reader_free(&rd);
}
/* END_CASE */

/* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER */
void mbedtls_mps_reader_pausing_needed_buffer_too_small()
{
    /* This test exercises the behaviour of the MPS reader with accumulator
     * in the situation where a read request goes beyond the bounds of the
     * current read buffer, _and_ the reader's accumulator is too small to
     * hold the requested amount of data.
     *
     * In this case, we expect mbedtls_mps_reader_reclaim() to fail,
     * but it should be possible to continue fetching data as if
     * there had been no excess request via mbedtls_mps_reader_get()
     * and the call to mbedtls_mps_reader_reclaim() had been rejected
     * because of data remaining.
     */

    unsigned char buf[100];
    unsigned char acc[10];
    unsigned char *tmp;
    mbedtls_mps_reader rd;
    mbedtls_mps_size_t tmp_len;

    for (size_t i = 0; (unsigned) i < sizeof(buf); i++) {
        buf[i] = (unsigned char) i;
    }

    /* Preparation (lower layer) */
    mbedtls_mps_reader_init(&rd, acc, sizeof(acc));
    TEST_ASSERT(mbedtls_mps_reader_feed(&rd, buf, sizeof(buf)) == 0);
    /* Consumption (upper layer) */
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 50, &tmp, NULL) == 0);
    ASSERT_COMPARE(tmp, 50, buf, 50);
    TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 10, &tmp, NULL) == 0);
    ASSERT_COMPARE(tmp, 10, buf + 50, 10);
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 100, &tmp, NULL) ==
                MBEDTLS_ERR_MPS_READER_OUT_OF_DATA);
    /* Wrapup (lower layer) */
    TEST_ASSERT(mbedtls_mps_reader_reclaim(&rd, NULL) ==
                MBEDTLS_ERR_MPS_READER_ACCUMULATOR_TOO_SMALL);

    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 50, &tmp, &tmp_len) == 0);
    ASSERT_COMPARE(tmp, tmp_len, buf + 50, 50);

    mbedtls_mps_reader_free(&rd);
}
/* END_CASE */

/* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER */
void mbedtls_mps_reader_reclaim_overflow()
{
    /* This test exercises the behaviour of the MPS reader with accumulator
     * in the situation where upon calling mbedtls_mps_reader_reclaim(), the
     * uncommitted data together with the excess data missing in the last
     * call to mbedtls_mps_reader_get() exceeds the bounds of the type
     * holding the buffer length.
     */

    unsigned char buf[100];
    unsigned char acc[50];
    unsigned char *tmp;
    mbedtls_mps_reader rd;

    for (size_t i = 0; (unsigned) i < sizeof(buf); i++) {
        buf[i] = (unsigned char) i;
    }

    /* Preparation (lower layer) */
    mbedtls_mps_reader_init(&rd, acc, sizeof(acc));
    TEST_ASSERT(mbedtls_mps_reader_feed(&rd, buf, sizeof(buf)) == 0);
    /* Consumption (upper layer) */
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 50, &tmp, NULL) == 0);
    ASSERT_COMPARE(tmp, 50, buf, 50);
    /* Excess request */
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, (mbedtls_mps_size_t) -1, &tmp, NULL) ==
                MBEDTLS_ERR_MPS_READER_OUT_OF_DATA);
    /* Wrapup (lower layer) */
    TEST_ASSERT(mbedtls_mps_reader_reclaim(&rd, NULL) ==
                MBEDTLS_ERR_MPS_READER_ACCUMULATOR_TOO_SMALL);

    mbedtls_mps_reader_free(&rd);
}
/* END_CASE */

/* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER */
void mbedtls_mps_reader_pausing(int option)
{
    /* This test exercises the behaviour of the reader when the
     * accumulator is used to fulfill a consumer's request.
     *
     * More detailed:
     * - The producer feeds some data.
     * - The consumer asks for more data than what's available.
     * - The reader remembers the request and goes back to
     *   producing mode, waiting for more data from the producer.
     * - The producer provides another chunk of data which is
     *   sufficient to fulfill the original read request.
     * - The consumer retries the original read request, which
     *   should now succeed.
     *
     * This test comes in multiple variants controlled by the
     * `option` parameter and documented below.
     */

    unsigned char bufA[100], bufB[100];
    unsigned char *tmp;
    unsigned char acc[40];
    int paused;
    mbedtls_mps_reader rd;
    for (size_t i = 0; (unsigned) i < sizeof(bufA); i++) {
        bufA[i] = (unsigned char) i;
    }
    for (size_t i = 0; (unsigned) i < sizeof(bufB); i++) {
        bufB[i] = ~((unsigned char) i);
    }

    /* Preparation (lower layer) */
    mbedtls_mps_reader_init(&rd, acc, sizeof(acc));
    TEST_ASSERT(mbedtls_mps_reader_feed(&rd, bufA, sizeof(bufA)) == 0);

    /* Consumption (upper layer) */
    /* Ask for more than what's available. */
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 80, &tmp, NULL) == 0);
    ASSERT_COMPARE(tmp, 80, bufA, 80);
    TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 10, &tmp, NULL) == 0);
    ASSERT_COMPARE(tmp, 10, bufA + 80, 10);
    switch (option) {
        case 0:  /* Single uncommitted fetch at pausing */
        case 1:
            TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);
            break;
        default: /* Multiple uncommitted fetches at pausing */
            break;
    }
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 20, &tmp, NULL) ==
                MBEDTLS_ERR_MPS_READER_OUT_OF_DATA);

    /* Preparation */
    TEST_ASSERT(mbedtls_mps_reader_reclaim(&rd, &paused) == 0);
    TEST_ASSERT(paused == 1);
    TEST_ASSERT(mbedtls_mps_reader_feed(&rd, bufB, sizeof(bufB)) == 0);

    /* Consumption */
    switch (option) {
        case 0: /* Single fetch at pausing, re-fetch with commit. */
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 20, &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, 10, bufA + 90, 10);
            ASSERT_COMPARE(tmp + 10, 10, bufB, 10);
            TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);
            break;

        case 1: /* Single fetch at pausing, re-fetch without commit. */
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 20, &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, 10, bufA + 90, 10);
            ASSERT_COMPARE(tmp + 10, 10, bufB, 10);
            break;

        case 2: /* Multiple fetches at pausing, repeat without commit. */
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 10, &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, 10, bufA + 80, 10);
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 20, &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, 10, bufA + 90, 10);
            ASSERT_COMPARE(tmp + 10, 10, bufB, 10);
            break;

        case 3: /* Multiple fetches at pausing, repeat with commit 1. */
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 10, &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, 10, bufA + 80, 10);
            TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 20, &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, 10, bufA + 90, 10);
            ASSERT_COMPARE(tmp + 10, 10, bufB, 10);
            break;

        case 4: /* Multiple fetches at pausing, repeat with commit 2. */
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 10, &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, 10, bufA + 80, 10);
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 20, &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, 10, bufA + 90, 10);
            ASSERT_COMPARE(tmp + 10, 10, bufB, 10);
            TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);
            break;

        case 5: /* Multiple fetches at pausing, repeat with commit 3. */
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 10, &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, 10, bufA + 80, 10);
            TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 20, &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, 10, bufA + 90, 10);
            ASSERT_COMPARE(tmp + 10, 10, bufB, 10);
            TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);
            break;

        default:
            TEST_ASSERT(0);
    }

    /* In all cases, fetch the rest of the second buffer. */
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 90, &tmp, NULL) == 0);
    ASSERT_COMPARE(tmp, 90, bufB + 10, 90);
    TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);

    /* Wrapup */
    TEST_ASSERT(mbedtls_mps_reader_reclaim(&rd, NULL) == 0);
    mbedtls_mps_reader_free(&rd);
}
/* END_CASE */

/* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER */
void mbedtls_mps_reader_pausing_multiple_feeds(int option)
{
    /* This test exercises the behaviour of the MPS reader
     * in the following situation:
     * - The consumer has asked for more than what's available, so the
     *   reader pauses and waits for further input data via
     *   `mbedtls_mps_reader_feed()`
     * - Multiple such calls to `mbedtls_mps_reader_feed()` are necessary
     *   to fulfill the original request, and the reader needs to do
     *   the necessary bookkeeping under the hood.
     *
     * This test comes in a few variants differing in the number and
     * size of feed calls that the producer issues while the reader is
     * accumulating the necessary data - see the comments below.
     */

    unsigned char bufA[100], bufB[100];
    unsigned char *tmp;
    unsigned char acc[70];
    mbedtls_mps_reader rd;
    mbedtls_mps_size_t fetch_len;
    for (size_t i = 0; (unsigned) i < sizeof(bufA); i++) {
        bufA[i] = (unsigned char) i;
    }
    for (size_t i = 0; (unsigned) i < sizeof(bufB); i++) {
        bufB[i] = ~((unsigned char) i);
    }

    /* Preparation (lower layer) */
    mbedtls_mps_reader_init(&rd, acc, sizeof(acc));
    TEST_ASSERT(mbedtls_mps_reader_feed(&rd, bufA, sizeof(bufA)) == 0);

    /* Consumption (upper layer) */
    /* Ask for more than what's available. */
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 80, &tmp, NULL) == 0);
    ASSERT_COMPARE(tmp, 80, bufA, 80);
    TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);
    /* 20 left, ask for 70 -> 50 overhead */
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 70, &tmp, NULL) ==
                MBEDTLS_ERR_MPS_READER_OUT_OF_DATA);

    /* Preparation */
    TEST_ASSERT(mbedtls_mps_reader_reclaim(&rd, NULL) == 0);
    switch (option) {
        case 0: /* 10 + 10 + 80 byte feed */
            TEST_ASSERT(mbedtls_mps_reader_feed(&rd, bufB, 10) ==
                        MBEDTLS_ERR_MPS_READER_NEED_MORE);
            TEST_ASSERT(mbedtls_mps_reader_feed(&rd, bufB + 10, 10) ==
                        MBEDTLS_ERR_MPS_READER_NEED_MORE);
            TEST_ASSERT(mbedtls_mps_reader_feed(&rd, bufB + 20, 80) == 0);
            break;

        case 1: /* 50 x 1byte */
            for (size_t num_feed = 0; num_feed < 49; num_feed++) {
                TEST_ASSERT(mbedtls_mps_reader_feed(&rd, bufB + num_feed, 1) ==
                            MBEDTLS_ERR_MPS_READER_NEED_MORE);
            }
            TEST_ASSERT(mbedtls_mps_reader_feed(&rd, bufB + 49, 1) == 0);
            break;

        case 2: /* 49 x 1byte + 51bytes */
            for (size_t num_feed = 0; num_feed < 49; num_feed++) {
                TEST_ASSERT(mbedtls_mps_reader_feed(&rd, bufB + num_feed, 1) ==
                            MBEDTLS_ERR_MPS_READER_NEED_MORE);
            }
            TEST_ASSERT(mbedtls_mps_reader_feed(&rd, bufB + 49, 51) == 0);
            break;

        default:
            TEST_ASSERT(0);
            break;
    }

    /* Consumption */
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 70, &tmp, NULL) == 0);
    ASSERT_COMPARE(tmp, 20, bufA + 80, 20);
    ASSERT_COMPARE(tmp + 20, 50, bufB, 50);
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 1000, &tmp, &fetch_len) == 0);
    switch (option) {
        case 0:
            TEST_ASSERT(fetch_len == 50);
            break;

        case 1:
            TEST_ASSERT(fetch_len == 0);
            break;

        case 2:
            TEST_ASSERT(fetch_len == 50);
            break;

        default:
            TEST_ASSERT(0);
            break;
    }
    TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);

    /* Wrapup */
    TEST_ASSERT(mbedtls_mps_reader_reclaim(&rd, NULL) == 0);
    mbedtls_mps_reader_free(&rd);
}
/* END_CASE */


/* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER */
void mbedtls_mps_reader_reclaim_data_left(int option)
{
    /* This test exercises the behaviour of the MPS reader when a
     * call to mbedtls_mps_reader_reclaim() is made before all data
     * provided by the producer has been fetched and committed. */

    unsigned char buf[100];
    unsigned char *tmp;
    mbedtls_mps_reader rd;
    for (size_t i = 0; (unsigned) i < sizeof(buf); i++) {
        buf[i] = (unsigned char) i;
    }

    /* Preparation (lower layer) */
    mbedtls_mps_reader_init(&rd, NULL, 0);
    TEST_ASSERT(mbedtls_mps_reader_feed(&rd, buf, sizeof(buf)) == 0);

    /* Consumption (upper layer) */
    switch (option) {
        case 0:
            /* Fetch (but not commit) the entire buffer. */
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, sizeof(buf), &tmp, NULL)
                        == 0);
            ASSERT_COMPARE(tmp, 100, buf, 100);
            break;

        case 1:
            /* Fetch (but not commit) parts of the buffer. */
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, sizeof(buf) / 2,
                                               &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, sizeof(buf) / 2, buf, sizeof(buf) / 2);
            break;

        case 2:
            /* Fetch and commit parts of the buffer, then
             * fetch but not commit the rest of the buffer. */
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, sizeof(buf) / 2,
                                               &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, sizeof(buf) / 2, buf, sizeof(buf) / 2);
            TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, sizeof(buf) / 2,
                                               &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, sizeof(buf) / 2,
                           buf + sizeof(buf) / 2,
                           sizeof(buf) / 2);
            break;

        default:
            TEST_ASSERT(0);
            break;
    }

    /* Wrapup */
    TEST_ASSERT(mbedtls_mps_reader_reclaim(&rd, NULL) ==
                MBEDTLS_ERR_MPS_READER_DATA_LEFT);
    mbedtls_mps_reader_free(&rd);
}
/* END_CASE */

/* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER */
void mbedtls_mps_reader_reclaim_data_left_retry()
{
    /* This test exercises the behaviour of the MPS reader when an attempt
     * by the producer to reclaim the reader fails because of more data pending
     * to be processed, and the consumer subsequently fetches more data. */
    unsigned char buf[100];
    unsigned char *tmp;
    mbedtls_mps_reader rd;

    for (size_t i = 0; (unsigned) i < sizeof(buf); i++) {
        buf[i] = (unsigned char) i;
    }

    /* Preparation (lower layer) */
    mbedtls_mps_reader_init(&rd, NULL, 0);
    TEST_ASSERT(mbedtls_mps_reader_feed(&rd, buf, sizeof(buf)) == 0);
    /* Consumption (upper layer) */
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 50, &tmp, NULL) == 0);
    ASSERT_COMPARE(tmp, 50, buf, 50);
    TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 50, &tmp, NULL) == 0);
    ASSERT_COMPARE(tmp, 50, buf + 50, 50);
    /* Preparation */
    TEST_ASSERT(mbedtls_mps_reader_reclaim(&rd, NULL) ==
                MBEDTLS_ERR_MPS_READER_DATA_LEFT);
    /* Consumption */
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 50, &tmp, NULL) == 0);
    ASSERT_COMPARE(tmp, 50, buf + 50, 50);
    TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);
    /* Wrapup */
    TEST_ASSERT(mbedtls_mps_reader_reclaim(&rd, NULL) == 0);
    mbedtls_mps_reader_free(&rd);
}
/* END_CASE */

/* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER */
void mbedtls_mps_reader_multiple_pausing(int option)
{
    /* This test exercises the behaviour of the MPS reader
     * in the following situation:
     * - A read request via `mbedtls_mps_reader_get()` can't
     *   be served and the reader is paused to accumulate
     *   the desired amount of data from the producer.
     * - Once enough data is available, the consumer successfully
     *   reads the data from the reader, but afterwards exceeds
     *   the available data again - pausing is necessary for a
     *   second time.
     */

    unsigned char bufA[100], bufB[20], bufC[10];
    unsigned char *tmp;
    unsigned char acc[50];
    mbedtls_mps_size_t tmp_len;
    mbedtls_mps_reader rd;
    for (size_t i = 0; (unsigned) i < sizeof(bufA); i++) {
        bufA[i] = (unsigned char) i;
    }
    for (size_t i = 0; (unsigned) i < sizeof(bufB); i++) {
        bufB[i] = ~((unsigned char) i);
    }
    for (size_t i = 0; (unsigned) i < sizeof(bufC); i++) {
        bufC[i] = ~((unsigned char) i);
    }

    /* Preparation (lower layer) */
    mbedtls_mps_reader_init(&rd, acc, sizeof(acc));
    TEST_ASSERT(mbedtls_mps_reader_feed(&rd, bufA, sizeof(bufA)) == 0);

    /* Consumption (upper layer) */
    /* Ask for more than what's available. */
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 80, &tmp, NULL) == 0);
    ASSERT_COMPARE(tmp, 80, bufA, 80);
    TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 10, &tmp, NULL) == 0);
    ASSERT_COMPARE(tmp, 10, bufA + 80, 10);
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 20, &tmp, NULL) ==
                MBEDTLS_ERR_MPS_READER_OUT_OF_DATA);

    /* Preparation */
    TEST_ASSERT(mbedtls_mps_reader_reclaim(&rd, NULL) == 0);
    TEST_ASSERT(mbedtls_mps_reader_feed(&rd, bufB, sizeof(bufB)) == 0);

    switch (option) {
        case 0: /* Fetch same chunks, commit afterwards, and
                 * then exceed bounds of new buffer; accumulator
                 * large enough. */

            /* Consume */
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 10, &tmp, &tmp_len) == 0);
            ASSERT_COMPARE(tmp, tmp_len, bufA + 80, 10);
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 20, &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, 10, bufA + 90, 10);
            ASSERT_COMPARE(tmp + 10, 10, bufB, 10);
            TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 20, &tmp, NULL) ==
                        MBEDTLS_ERR_MPS_READER_OUT_OF_DATA);

            /* Prepare */
            TEST_ASSERT(mbedtls_mps_reader_reclaim(&rd, NULL) == 0);
            TEST_ASSERT(mbedtls_mps_reader_feed(&rd, bufC, sizeof(bufC)) == 0);;

            /* Consume */
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 20, &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, 10, bufB + 10, 10);
            ASSERT_COMPARE(tmp + 10, 10, bufC, 10);
            break;

        case 1: /* Fetch same chunks, commit afterwards, and
                 * then exceed bounds of new buffer; accumulator
                 * not large enough. */
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 10, &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, 10, bufA + 80, 10);
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 20, &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, 10, bufA + 90, 10);
            ASSERT_COMPARE(tmp + 10, 10, bufB, 10);
            TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 51, &tmp, NULL) ==
                        MBEDTLS_ERR_MPS_READER_OUT_OF_DATA);

            /* Prepare */
            TEST_ASSERT(mbedtls_mps_reader_reclaim(&rd, NULL) ==
                        MBEDTLS_ERR_MPS_READER_ACCUMULATOR_TOO_SMALL);
            break;

        case 2: /* Fetch same chunks, don't commit afterwards, and
                 * then exceed bounds of new buffer; accumulator
                 * large enough. */
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 10, &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, 10, bufA + 80, 10);
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 20, &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, 10, bufA + 90, 10);
            ASSERT_COMPARE(tmp + 10, 10, bufB, 10);
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 20, &tmp, NULL) ==
                        MBEDTLS_ERR_MPS_READER_OUT_OF_DATA);

            /* Prepare */
            TEST_ASSERT(mbedtls_mps_reader_reclaim(&rd, NULL) == 0);
            TEST_ASSERT(mbedtls_mps_reader_feed(&rd, bufC, sizeof(bufC)) == 0);;

            /* Consume */
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 50, &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, 20, bufA + 80, 20);
            ASSERT_COMPARE(tmp + 20, 20, bufB, 20);
            ASSERT_COMPARE(tmp + 40, 10, bufC, 10);
            break;

        case 3: /* Fetch same chunks, don't commit afterwards, and
                 * then exceed bounds of new buffer; accumulator
                 * not large enough. */
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 10, &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, 10, bufA + 80, 10);
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 20, &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, 10, bufA + 90, 10);
            ASSERT_COMPARE(tmp + 10, 10, bufB, 10);
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 21, &tmp, NULL) ==
                        MBEDTLS_ERR_MPS_READER_OUT_OF_DATA);

            /* Prepare */
            TEST_ASSERT(mbedtls_mps_reader_reclaim(&rd, NULL) ==
                        MBEDTLS_ERR_MPS_READER_ACCUMULATOR_TOO_SMALL);
            break;

        default:
            TEST_ASSERT(0);
            break;
    }

    mbedtls_mps_reader_free(&rd);
}
/* END_CASE */

/* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER:MBEDTLS_MPS_STATE_VALIDATION */
void mbedtls_mps_reader_random_usage(int num_out_chunks,
                                     int max_chunk_size,
                                     int max_request,
                                     int acc_size)

{
    /* Randomly pass a reader object back and forth between lower and
     * upper layer and let each of them call the respective reader API
     * functions in a random fashion.
     *
     * On the lower layer, we're tracking and concatenating
     * the data passed to successful feed calls.
     *
     * For the upper layer, we track and concatenate buffers
     * obtained from successful get calls.
     *
     * As long as the lower layer calls reclaim at least once, (resetting the
     * fetched but not-yet-committed data), this should always lead to the same
     * stream of outgoing/incoming data for the lower/upper layers, even if
     * most of the random calls fail.
     *
     * NOTE: This test uses rand() for random data, which is not optimal.
     *       Instead, it would be better to get the random data from a
     *       static buffer. This both eases reproducibility and allows
     *       simple conversion to a fuzz target.
     */
    int ret;
    unsigned char *acc = NULL;
    unsigned char *outgoing = NULL, *incoming = NULL;
    unsigned char *cur_chunk = NULL;
    size_t cur_out_chunk, out_pos, in_commit, in_fetch;
    int rand_op;  /* Lower layer:
                   * - Reclaim (0)
                   * - Feed (1)
                   * Upper layer:
                   * - Get, do tolerate smaller output (0)
                   * - Get, don't tolerate smaller output (1)
                   * - Commit (2) */
    int mode = 0; /* Lower layer (0) or Upper layer (1) */
    int reclaimed = 1; /* Have to call reclaim at least once before
                        * returning the reader to the upper layer. */
    mbedtls_mps_reader rd;

    if (acc_size > 0) {
        ASSERT_ALLOC(acc, acc_size);
    }

    /* This probably needs to be changed because we want
     * our tests to be deterministic. */
    //    srand( time( NULL ) );

    ASSERT_ALLOC(outgoing, num_out_chunks * max_chunk_size);
    ASSERT_ALLOC(incoming, num_out_chunks * max_chunk_size);

    mbedtls_mps_reader_init(&rd, acc, acc_size);

    cur_out_chunk = 0;
    in_commit = 0;
    in_fetch = 0;
    out_pos = 0;
    while (cur_out_chunk < (unsigned) num_out_chunks) {
        if (mode == 0) {
            /* Choose randomly between reclaim and feed */
            rand_op = rand() % 2;

            if (rand_op == 0) {
                /* Reclaim */
                ret = mbedtls_mps_reader_reclaim(&rd, NULL);

                if (ret == 0) {
                    TEST_ASSERT(cur_chunk != NULL);
                    mbedtls_free(cur_chunk);
                    cur_chunk = NULL;
                }
                reclaimed = 1;
            } else {
                /* Feed reader with a random chunk */
                unsigned char *tmp = NULL;
                size_t tmp_size;
                if (cur_out_chunk == (unsigned) num_out_chunks) {
                    continue;
                }

                tmp_size = (rand() % max_chunk_size) + 1;
                ASSERT_ALLOC(tmp, tmp_size);

                TEST_ASSERT(mbedtls_test_rnd_std_rand(NULL, tmp, tmp_size) == 0);
                ret = mbedtls_mps_reader_feed(&rd, tmp, tmp_size);

                if (ret == 0 || ret == MBEDTLS_ERR_MPS_READER_NEED_MORE) {
                    cur_out_chunk++;
                    memcpy(outgoing + out_pos, tmp, tmp_size);
                    out_pos += tmp_size;
                }

                if (ret == 0) {
                    TEST_ASSERT(cur_chunk == NULL);
                    cur_chunk = tmp;
                } else {
                    mbedtls_free(tmp);
                }

            }

            /* Randomly switch to consumption mode if reclaim
             * was called at least once. */
            if (reclaimed == 1 && rand() % 3 == 0) {
                in_fetch = 0;
                mode = 1;
            }
        } else {
            /* Choose randomly between get tolerating fewer data,
             * get not tolerating fewer data, and commit. */
            rand_op = rand() % 3;
            if (rand_op == 0 || rand_op == 1) {
                mbedtls_mps_size_t get_size, real_size;
                unsigned char *chunk_get;
                get_size = (rand() % max_request) + 1;
                if (rand_op == 0) {
                    ret = mbedtls_mps_reader_get(&rd, get_size, &chunk_get,
                                                 &real_size);
                } else {
                    real_size = get_size;
                    ret = mbedtls_mps_reader_get(&rd, get_size, &chunk_get, NULL);
                }

                /* Check if output is in accordance with what was written */
                if (ret == 0) {
                    memcpy(incoming + in_commit + in_fetch,
                           chunk_get, real_size);
                    TEST_ASSERT(memcmp(incoming + in_commit + in_fetch,
                                       outgoing + in_commit + in_fetch,
                                       real_size) == 0);
                    in_fetch += real_size;
                }
            } else if (rand_op == 2) { /* Commit */
                ret = mbedtls_mps_reader_commit(&rd);
                if (ret == 0) {
                    in_commit += in_fetch;
                    in_fetch = 0;
                }
            }

            /* Randomly switch back to preparation */
            if (rand() % 3 == 0) {
                reclaimed = 0;
                mode = 0;
            }
        }
    }

    /* Cleanup */
    mbedtls_mps_reader_free(&rd);
    mbedtls_free(incoming);
    mbedtls_free(outgoing);
    mbedtls_free(acc);
    mbedtls_free(cur_chunk);
}
/* END_CASE */

/* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER */
void mbedtls_reader_inconsistent_usage(int option)
{
    /* This test exercises the behaviour of the MPS reader
     * in the following situation:
     * - The consumer asks for more data than what's available
     * - The reader is paused and receives more data from the
     *   producer until the original read request can be fulfilled.
     * - The consumer does not repeat the original request but
     *   requests data in a different way.
     *
     * The reader does not guarantee that inconsistent read requests
     * after pausing will succeed, and this test triggers some cases
     * where the request fails.
     */

    unsigned char bufA[100], bufB[100];
    unsigned char *tmp;
    unsigned char acc[40];
    mbedtls_mps_reader rd;
    int success = 0;
    for (size_t i = 0; (unsigned) i < sizeof(bufA); i++) {
        bufA[i] = (unsigned char) i;
    }
    for (size_t i = 0; (unsigned) i < sizeof(bufB); i++) {
        bufB[i] = ~((unsigned char) i);
    }

    /* Preparation (lower layer) */
    mbedtls_mps_reader_init(&rd, acc, sizeof(acc));
    TEST_ASSERT(mbedtls_mps_reader_feed(&rd, bufA, sizeof(bufA)) == 0);
    /* Consumption (upper layer) */
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 80, &tmp, NULL) == 0);
    TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 10, &tmp, NULL) == 0);
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 20, &tmp, NULL) ==
                MBEDTLS_ERR_MPS_READER_OUT_OF_DATA);
    /* Preparation */
    TEST_ASSERT(mbedtls_mps_reader_reclaim(&rd, NULL) == 0);
    TEST_ASSERT(mbedtls_mps_reader_feed(&rd, bufB, sizeof(bufB)) == 0);
    /* Consumption */
    switch (option) {
        case 0:
            /* Ask for buffered data in a single chunk, no commit */
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 30, &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, 20, bufA + 80, 20);
            ASSERT_COMPARE(tmp + 20, 10, bufB, 10);
            success = 1;
            break;

        case 1:
            /* Ask for buffered data in a single chunk, with commit */
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 30, &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, 20, bufA + 80, 20);
            ASSERT_COMPARE(tmp + 20, 10, bufB, 10);
            TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);
            success = 1;
            break;

        case 2:
            /* Ask for more than was requested when pausing, #1 */
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 31, &tmp, NULL) ==
                        MBEDTLS_ERR_MPS_READER_INCONSISTENT_REQUESTS);
            break;

        case 3:
            /* Ask for more than was requested when pausing #2 */
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, (mbedtls_mps_size_t) -1, &tmp, NULL) ==
                        MBEDTLS_ERR_MPS_READER_INCONSISTENT_REQUESTS);
            break;

        case 4:
            /* Asking for buffered data in different
             * chunks than before CAN fail. */
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 15, &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, 15, bufA + 80, 15);
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 10, &tmp, NULL) ==
                        MBEDTLS_ERR_MPS_READER_INCONSISTENT_REQUESTS);
            break;

        case 5:
            /* Asking for buffered data different chunks
             * than before NEED NOT fail - no commits */
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 15, &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, 15, bufA + 80, 15);
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 15, &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, 5, bufA + 95, 5);
            ASSERT_COMPARE(tmp + 5, 10, bufB, 10);
            success = 1;
            break;

        case 6:
            /* Asking for buffered data different chunks
             * than before NEED NOT fail - intermediate commit */
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 15, &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, 15, bufA + 80, 15);
            TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 15, &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, 5, bufA + 95, 5);
            ASSERT_COMPARE(tmp + 5, 10, bufB, 10);
            success = 1;
            break;

        case 7:
            /* Asking for buffered data different chunks
             * than before NEED NOT fail - end commit */
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 15, &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, 15, bufA + 80, 15);
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 15, &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, 5, bufA + 95, 5);
            ASSERT_COMPARE(tmp + 5, 10, bufB, 10);
            TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);
            success = 1;
            break;

        case 8:
            /* Asking for buffered data different chunks
             * than before NEED NOT fail - intermediate & end commit */
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 15, &tmp, NULL) == 0);
            ASSERT_COMPARE(tmp, 15, bufA + 80, 15);
            TEST_ASSERT(mbedtls_mps_reader_get(&rd, 15, &tmp, NULL) == 0);
            TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);
            ASSERT_COMPARE(tmp, 5, bufA + 95, 5);
            ASSERT_COMPARE(tmp + 5, 10, bufB, 10);
            TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);
            success = 1;
            break;

        default:
            TEST_ASSERT(0);
            break;
    }

    if (success == 1) {
        /* In all succeeding cases, fetch the rest of the second buffer. */
        TEST_ASSERT(mbedtls_mps_reader_get(&rd, 90, &tmp, NULL) == 0);
        ASSERT_COMPARE(tmp, 90, bufB + 10, 90);
        TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);

        /* Wrapup */
        TEST_ASSERT(mbedtls_mps_reader_reclaim(&rd, NULL) == 0);
    }

    /* Wrapup */
    mbedtls_mps_reader_free(&rd);
}
/* END_CASE */

/* BEGIN_CASE depends_on:TEST_SUITE_MPS_READER */
void mbedtls_mps_reader_feed_empty()
{
    /* This test exercises the behaviour of the reader when it is
     * fed with a NULL buffer. */
    unsigned char buf[100];
    unsigned char *tmp;
    mbedtls_mps_reader rd;
    for (size_t i = 0; (unsigned) i < sizeof(buf); i++) {
        buf[i] = (unsigned char) i;
    }

    /* Preparation (lower layer) */
    mbedtls_mps_reader_init(&rd, NULL, 0);

    TEST_ASSERT(mbedtls_mps_reader_feed(&rd, NULL, sizeof(buf)) ==
                MBEDTLS_ERR_MPS_READER_INVALID_ARG);

    /* Subsequent feed-calls should still succeed. */
    TEST_ASSERT(mbedtls_mps_reader_feed(&rd, buf, sizeof(buf)) == 0);

    /* Consumption (upper layer) */
    TEST_ASSERT(mbedtls_mps_reader_get(&rd, 100, &tmp, NULL) == 0);
    ASSERT_COMPARE(tmp, 100, buf, 100);
    TEST_ASSERT(mbedtls_mps_reader_commit(&rd) == 0);

    /* Wrapup */
    TEST_ASSERT(mbedtls_mps_reader_reclaim(&rd, NULL) == 0);
    mbedtls_mps_reader_free(&rd);
}
/* END_CASE */