mbedtls/tests/suites/test_suite_ctr_drbg.function

/* BEGIN_HEADER */
#include "mbedtls/entropy.h"
#include "mbedtls/ctr_drbg.h"
#include "string.h"

/* Modes for ctr_drbg_validate */
enum reseed_mode {
    RESEED_NEVER, /* never reseed */
    RESEED_FIRST, /* instantiate, reseed, generate, generate */
    RESEED_SECOND, /* instantiate, generate, reseed, generate */
    RESEED_ALWAYS /* prediction resistance, no explicit reseed */
};

static size_t test_offset_idx = 0;
static size_t test_max_idx  = 0;
static int mbedtls_test_entropy_func(void *data, unsigned char *buf, size_t len)
{
    const unsigned char *p = (unsigned char *) data;
    if (test_offset_idx + len > test_max_idx) {
        return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
    }
    memcpy(buf, p + test_offset_idx, len);
    test_offset_idx += len;
    return 0;
}

static void ctr_drbg_validate_internal(int reseed_mode, data_t *nonce,
                                       int entropy_len_arg, data_t *entropy,
                                       data_t *reseed,
                                       data_t *add1, data_t *add2,
                                       data_t *result)
{
    mbedtls_ctr_drbg_context ctx;
    unsigned char buf[64];

    size_t entropy_chunk_len = (size_t) entropy_len_arg;

    TEST_ASSERT(entropy_chunk_len <= sizeof(buf));

    test_offset_idx = 0;
    mbedtls_ctr_drbg_init(&ctx);

    test_max_idx = entropy->len;

    /* CTR_DRBG_Instantiate(entropy[:entropy->len], nonce, perso, <ignored>)
     * where nonce||perso = nonce[nonce->len] */
    mbedtls_ctr_drbg_set_entropy_len(&ctx, entropy_chunk_len);
    mbedtls_ctr_drbg_set_nonce_len(&ctx, 0);
    TEST_ASSERT(mbedtls_ctr_drbg_seed(
                    &ctx,
                    mbedtls_test_entropy_func, entropy->x,
                    nonce->x, nonce->len) == 0);
    if (reseed_mode == RESEED_ALWAYS) {
        mbedtls_ctr_drbg_set_prediction_resistance(
            &ctx,
            MBEDTLS_CTR_DRBG_PR_ON);
    }

    if (reseed_mode == RESEED_FIRST) {
        /* CTR_DRBG_Reseed(entropy[idx:idx+entropy->len],
         *                 reseed[:reseed->len]) */
        TEST_ASSERT(mbedtls_ctr_drbg_reseed(
                        &ctx,
                        reseed->x, reseed->len) == 0);
    }

    /* CTR_DRBG_Generate(result->len * 8 bits, add1[:add1->len]) -> buf */
    /* Then reseed if prediction resistance is enabled. */
    TEST_ASSERT(mbedtls_ctr_drbg_random_with_add(
                    &ctx,
                    buf, result->len,
                    add1->x, add1->len) == 0);


    if (reseed_mode == RESEED_SECOND) {
        /* CTR_DRBG_Reseed(entropy[idx:idx+entropy->len],
         *                 reseed[:reseed->len]) */
        TEST_ASSERT(mbedtls_ctr_drbg_reseed(
                        &ctx,
                        reseed->x, reseed->len) == 0);
    }

    /* CTR_DRBG_Generate(result->len * 8 bits, add2->x[:add2->len]) -> buf */
    /* Then reseed if prediction resistance is enabled. */
    TEST_ASSERT(mbedtls_ctr_drbg_random_with_add(
                    &ctx,
                    buf, result->len,
                    add2->x, add2->len) == 0);
    TEST_ASSERT(memcmp(buf, result->x, result->len) == 0);

exit:
    mbedtls_ctr_drbg_free(&ctx);
}

/* END_HEADER */

/* BEGIN_DEPENDENCIES
 * depends_on:MBEDTLS_CTR_DRBG_C
 * END_DEPENDENCIES
 */

/* BEGIN_CASE */
void ctr_drbg_special_behaviours()
{
    mbedtls_ctr_drbg_context ctx;
    unsigned char output[512];
    unsigned char additional[512];

    mbedtls_ctr_drbg_init(&ctx);
    memset(output, 0, sizeof(output));
    memset(additional, 0, sizeof(additional));

    TEST_ASSERT(mbedtls_ctr_drbg_random_with_add(&ctx,
                                                 output, MBEDTLS_CTR_DRBG_MAX_REQUEST + 1,
                                                 additional, 16) ==
                MBEDTLS_ERR_CTR_DRBG_REQUEST_TOO_BIG);
    TEST_ASSERT(mbedtls_ctr_drbg_random_with_add(&ctx,
                                                 output, 16,
                                                 additional, MBEDTLS_CTR_DRBG_MAX_INPUT + 1) ==
                MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG);

    TEST_ASSERT(mbedtls_ctr_drbg_reseed(&ctx, additional,
                                        MBEDTLS_CTR_DRBG_MAX_SEED_INPUT + 1) ==
                MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG);

    mbedtls_ctr_drbg_set_entropy_len(&ctx, ~0);
    TEST_ASSERT(mbedtls_ctr_drbg_reseed(&ctx, additional,
                                        MBEDTLS_CTR_DRBG_MAX_SEED_INPUT) ==
                MBEDTLS_ERR_CTR_DRBG_INPUT_TOO_BIG);
exit:
    mbedtls_ctr_drbg_free(&ctx);
}
/* END_CASE */


/* BEGIN_CASE */
void ctr_drbg_validate_no_reseed(data_t *add_init, data_t *entropy,
                                 data_t *add1, data_t *add2,
                                 data_t *result_string)
{
    data_t empty = { 0, 0 };
    ctr_drbg_validate_internal(RESEED_NEVER, add_init,
                               entropy->len, entropy,
                               &empty, add1, add2,
                               result_string);
    goto exit; // goto is needed to avoid warning ( no test assertions in func)
}
/* END_CASE */

/* BEGIN_CASE */
void ctr_drbg_validate_pr(data_t *add_init, data_t *entropy,
                          data_t *add1, data_t *add2,
                          data_t *result_string)
{
    data_t empty = { 0, 0 };
    ctr_drbg_validate_internal(RESEED_ALWAYS, add_init,
                               entropy->len / 3, entropy,
                               &empty, add1, add2,
                               result_string);
    goto exit; // goto is needed to avoid warning ( no test assertions in func)
}
/* END_CASE */

/* BEGIN_CASE */
void ctr_drbg_validate_reseed_between(data_t *add_init, data_t *entropy,
                                      data_t *add1, data_t *add_reseed,
                                      data_t *add2, data_t *result_string)
{
    ctr_drbg_validate_internal(RESEED_SECOND, add_init,
                               entropy->len / 2, entropy,
                               add_reseed, add1, add2,
                               result_string);
    goto exit; // goto is needed to avoid warning ( no test assertions in func)
}
/* END_CASE */

/* BEGIN_CASE */
void ctr_drbg_validate_reseed_first(data_t *add_init, data_t *entropy,
                                    data_t *add1, data_t *add_reseed,
                                    data_t *add2, data_t *result_string)
{
    ctr_drbg_validate_internal(RESEED_FIRST, add_init,
                               entropy->len / 2, entropy,
                               add_reseed, add1, add2,
                               result_string);
    goto exit; // goto is needed to avoid warning ( no test assertions in func)
}
/* END_CASE */

/* BEGIN_CASE */
void ctr_drbg_entropy_strength(int expected_bit_strength)
{
    unsigned char entropy[/*initial entropy*/ MBEDTLS_CTR_DRBG_ENTROPY_LEN +
                          /*nonce*/ MBEDTLS_CTR_DRBG_ENTROPY_NONCE_LEN +
                          /*reseed*/ MBEDTLS_CTR_DRBG_ENTROPY_LEN];
    mbedtls_ctr_drbg_context ctx;
    size_t last_idx;
    size_t byte_strength = expected_bit_strength / 8;

    mbedtls_ctr_drbg_init(&ctx);
    test_offset_idx = 0;
    test_max_idx = sizeof(entropy);
    memset(entropy, 0, sizeof(entropy));

    /* The initial seeding must grab at least byte_strength bytes of entropy
     * for the entropy input and byte_strength/2 bytes for a nonce. */
    TEST_ASSERT(mbedtls_ctr_drbg_seed(&ctx,
                                      mbedtls_test_entropy_func, entropy,
                                      NULL, 0) == 0);
    TEST_ASSERT(test_offset_idx >= (byte_strength * 3 + 1) / 2);
    last_idx = test_offset_idx;

    /* A reseed must grab at least byte_strength bytes of entropy. */
    TEST_ASSERT(mbedtls_ctr_drbg_reseed(&ctx, NULL, 0) == 0);
    TEST_ASSERT(test_offset_idx - last_idx >= byte_strength);

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

/* BEGIN_CASE */
void ctr_drbg_entropy_usage(int entropy_nonce_len)
{
    unsigned char out[16];
    unsigned char add[16];
    unsigned char entropy[1024];
    mbedtls_ctr_drbg_context ctx;
    size_t i, reps = 10;
    size_t expected_idx = 0;

    mbedtls_ctr_drbg_init(&ctx);
    test_offset_idx = 0;
    test_max_idx = sizeof(entropy);
    memset(entropy, 0, sizeof(entropy));
    memset(out, 0, sizeof(out));
    memset(add, 0, sizeof(add));

    if (entropy_nonce_len >= 0) {
        TEST_ASSERT(mbedtls_ctr_drbg_set_nonce_len(&ctx, entropy_nonce_len) == 0);
    }

    /* Set reseed interval before seed */
    mbedtls_ctr_drbg_set_reseed_interval(&ctx, 2 * reps);

    /* Init must use entropy */
    TEST_ASSERT(mbedtls_ctr_drbg_seed(&ctx, mbedtls_test_entropy_func, entropy, NULL, 0) == 0);
    expected_idx += MBEDTLS_CTR_DRBG_ENTROPY_LEN;
    if (entropy_nonce_len >= 0) {
        expected_idx += entropy_nonce_len;
    } else {
        expected_idx += MBEDTLS_CTR_DRBG_ENTROPY_NONCE_LEN;
    }
    TEST_EQUAL(test_offset_idx, expected_idx);

    /* By default, PR is off, and reseed interval was set to
     * 2 * reps so the next few calls should not use entropy */
    for (i = 0; i < reps; i++) {
        TEST_ASSERT(mbedtls_ctr_drbg_random(&ctx, out, sizeof(out) - 4) == 0);
        TEST_ASSERT(mbedtls_ctr_drbg_random_with_add(&ctx, out, sizeof(out) - 4,
                                                     add, sizeof(add)) == 0);
    }
    TEST_EQUAL(test_offset_idx, expected_idx);

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

    /* There have been 2 * reps calls to random. The next call should reseed */
    TEST_ASSERT(mbedtls_ctr_drbg_random(&ctx, out, sizeof(out)) == 0);
    expected_idx += MBEDTLS_CTR_DRBG_ENTROPY_LEN;
    TEST_EQUAL(test_offset_idx, expected_idx);

    /* Set reseed interval after seed */
    mbedtls_ctr_drbg_set_reseed_interval(&ctx, 4 * reps + 1);

    /* The next few calls should not reseed */
    for (i = 0; i < (2 * reps); i++) {
        TEST_ASSERT(mbedtls_ctr_drbg_random(&ctx, out, sizeof(out)) == 0);
        TEST_ASSERT(mbedtls_ctr_drbg_random_with_add(&ctx, out, sizeof(out),
                                                     add, sizeof(add)) == 0);
    }
    TEST_EQUAL(test_offset_idx, expected_idx);

    /* Call update with too much data (sizeof(entropy) > MAX(_SEED)_INPUT).
     * Make sure it's detected as an error and doesn't cause memory
     * corruption. */
    TEST_ASSERT(mbedtls_ctr_drbg_update(
                    &ctx, entropy, sizeof(entropy)) != 0);

    /* Now enable PR, so the next few calls should all reseed */
    mbedtls_ctr_drbg_set_prediction_resistance(&ctx, MBEDTLS_CTR_DRBG_PR_ON);
    TEST_ASSERT(mbedtls_ctr_drbg_random(&ctx, out, sizeof(out)) == 0);
    expected_idx += MBEDTLS_CTR_DRBG_ENTROPY_LEN;
    TEST_EQUAL(test_offset_idx, expected_idx);

    /* Finally, check setting entropy_len */
    mbedtls_ctr_drbg_set_entropy_len(&ctx, 42);
    TEST_ASSERT(mbedtls_ctr_drbg_random(&ctx, out, sizeof(out)) == 0);
    expected_idx += 42;
    TEST_EQUAL(test_offset_idx, expected_idx);

    mbedtls_ctr_drbg_set_entropy_len(&ctx, 13);
    TEST_ASSERT(mbedtls_ctr_drbg_random(&ctx, out, sizeof(out)) == 0);
    expected_idx += 13;
    TEST_EQUAL(test_offset_idx, expected_idx);

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

/* BEGIN_CASE depends_on:MBEDTLS_FS_IO */
void ctr_drbg_seed_file(char *path, int ret)
{
    mbedtls_ctr_drbg_context ctx;

    mbedtls_ctr_drbg_init(&ctx);

    TEST_ASSERT(mbedtls_ctr_drbg_seed(&ctx, mbedtls_test_rnd_std_rand,
                                      NULL, NULL, 0) == 0);
    TEST_ASSERT(mbedtls_ctr_drbg_write_seed_file(&ctx, path) == ret);
    TEST_ASSERT(mbedtls_ctr_drbg_update_seed_file(&ctx, path) == ret);

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

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