mbedtls/tests/suites/test_suite_entropy.function

/* BEGIN_HEADER */
#include "mbedtls/entropy.h"
#include "entropy_poll.h"
#include "mbedtls/md.h"
#include "string.h"

typedef enum {
    DUMMY_CONSTANT_LENGTH, /* Output context->length bytes */
    DUMMY_REQUESTED_LENGTH, /* Output whatever length was requested */
    DUMMY_FAIL, /* Return an error code */
} entropy_dummy_instruction;

typedef struct {
    entropy_dummy_instruction instruction;
    size_t length; /* Length to return for DUMMY_CONSTANT_LENGTH */
    size_t calls; /* Incremented at each call */
} entropy_dummy_context;

/*
 * Dummy entropy source
 *
 * If data is NULL, write exactly the requested length.
 * Otherwise, write the length indicated by data or error if negative
 */
static int entropy_dummy_source(void *arg, unsigned char *output,
                                size_t len, size_t *olen)
{
    entropy_dummy_context *context = arg;
    ++context->calls;

    switch (context->instruction) {
        case DUMMY_CONSTANT_LENGTH:
            *olen = context->length;
            break;
        case DUMMY_REQUESTED_LENGTH:
            *olen = len;
            break;
        case DUMMY_FAIL:
            return MBEDTLS_ERR_ENTROPY_SOURCE_FAILED;
    }

    memset(output, 0x2a, *olen);
    return 0;
}

/*
 * Ability to clear entropy sources to allow testing with just predefined
 * entropy sources. This function or tests depending on it might break if there
 * are internal changes to how entropy sources are registered.
 *
 * To be called immediately after mbedtls_entropy_init().
 *
 * Just resetting the counter. New sources will overwrite existing ones.
 * This might break memory checks in the future if sources need 'free-ing' then
 * as well.
 */
static void entropy_clear_sources(mbedtls_entropy_context *ctx)
{
    ctx->source_count = 0;
}

#if defined(MBEDTLS_ENTROPY_NV_SEED)
/*
 * NV seed read/write functions that use a buffer instead of a file
 */
static unsigned char buffer_seed[MBEDTLS_ENTROPY_BLOCK_SIZE];

int buffer_nv_seed_read(unsigned char *buf, size_t buf_len)
{
    if (buf_len != MBEDTLS_ENTROPY_BLOCK_SIZE) {
        return -1;
    }

    memcpy(buf, buffer_seed, MBEDTLS_ENTROPY_BLOCK_SIZE);
    return 0;
}

int buffer_nv_seed_write(unsigned char *buf, size_t buf_len)
{
    if (buf_len != MBEDTLS_ENTROPY_BLOCK_SIZE) {
        return -1;
    }

    memcpy(buffer_seed, buf, MBEDTLS_ENTROPY_BLOCK_SIZE);
    return 0;
}

/*
 * NV seed read/write helpers that fill the base seedfile
 */
static int write_nv_seed(unsigned char *buf, size_t buf_len)
{
    FILE *f;

    if (buf_len != MBEDTLS_ENTROPY_BLOCK_SIZE) {
        return -1;
    }

    if ((f = fopen(MBEDTLS_PLATFORM_STD_NV_SEED_FILE, "w")) == NULL) {
        return -1;
    }

    if (fwrite(buf, 1, MBEDTLS_ENTROPY_BLOCK_SIZE, f) !=
        MBEDTLS_ENTROPY_BLOCK_SIZE) {
        return -1;
    }

    fclose(f);

    return 0;
}

int read_nv_seed(unsigned char *buf, size_t buf_len)
{
    FILE *f;

    if (buf_len != MBEDTLS_ENTROPY_BLOCK_SIZE) {
        return -1;
    }

    if ((f = fopen(MBEDTLS_PLATFORM_STD_NV_SEED_FILE, "rb")) == NULL) {
        return -1;
    }

    if (fread(buf, 1, MBEDTLS_ENTROPY_BLOCK_SIZE, f) !=
        MBEDTLS_ENTROPY_BLOCK_SIZE) {
        return -1;
    }

    fclose(f);

    return 0;
}
#endif /* MBEDTLS_ENTROPY_NV_SEED */
/* END_HEADER */

/* BEGIN_DEPENDENCIES
 * depends_on:MBEDTLS_ENTROPY_C
 * END_DEPENDENCIES
 */

/* BEGIN_CASE */
void entropy_init_free(int reinit)
{
    mbedtls_entropy_context ctx;

    /* Double free is not explicitly documented to work, but it is convenient
     * to call mbedtls_entropy_free() unconditionally on an error path without
     * checking whether it has already been called in the success path. */

    mbedtls_entropy_init(&ctx);
    mbedtls_entropy_free(&ctx);

    if (reinit) {
        mbedtls_entropy_init(&ctx);
    }
    mbedtls_entropy_free(&ctx);

    /* This test case always succeeds, functionally speaking. A plausible
     * bug might trigger an invalid pointer dereference or a memory leak. */
    goto exit;
}
/* END_CASE */

/* BEGIN_CASE depends_on:MBEDTLS_ENTROPY_NV_SEED:MBEDTLS_FS_IO */
void entropy_seed_file(char *path, int ret)
{
    mbedtls_entropy_context ctx;

    mbedtls_entropy_init(&ctx);

    TEST_ASSERT(mbedtls_entropy_write_seed_file(&ctx, path) == ret);
    TEST_ASSERT(mbedtls_entropy_update_seed_file(&ctx, path) == ret);

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

/* BEGIN_CASE depends_on:MBEDTLS_ENTROPY_NV_SEED:MBEDTLS_FS_IO */
void entropy_write_base_seed_file(int ret)
{
    mbedtls_entropy_context ctx;

    mbedtls_entropy_init(&ctx);

    TEST_ASSERT(mbedtls_entropy_write_seed_file(&ctx, MBEDTLS_PLATFORM_STD_NV_SEED_FILE) == ret);
    TEST_ASSERT(mbedtls_entropy_update_seed_file(&ctx, MBEDTLS_PLATFORM_STD_NV_SEED_FILE) == ret);

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

/* BEGIN_CASE */
void entropy_no_sources()
{
    mbedtls_entropy_context ctx;
    unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];

    mbedtls_entropy_init(&ctx);
    entropy_clear_sources(&ctx);
    TEST_EQUAL(mbedtls_entropy_func(&ctx, buf, sizeof(buf)),
               MBEDTLS_ERR_ENTROPY_NO_SOURCES_DEFINED);

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

/* BEGIN_CASE */
void entropy_too_many_sources()
{
    mbedtls_entropy_context ctx;
    size_t i;
    entropy_dummy_context dummy = { DUMMY_REQUESTED_LENGTH, 0, 0 };

    mbedtls_entropy_init(&ctx);

    /*
     * It's hard to tell precisely when the error will occur,
     * since we don't know how many sources were automatically added.
     */
    for (i = 0; i < MBEDTLS_ENTROPY_MAX_SOURCES; i++) {
        (void) mbedtls_entropy_add_source(&ctx, entropy_dummy_source, &dummy,
                                          16, MBEDTLS_ENTROPY_SOURCE_WEAK);
    }

    TEST_ASSERT(mbedtls_entropy_add_source(&ctx, entropy_dummy_source, &dummy,
                                           16, MBEDTLS_ENTROPY_SOURCE_WEAK)
                == MBEDTLS_ERR_ENTROPY_MAX_SOURCES);

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

/* BEGIN_CASE depends_on:ENTROPY_HAVE_STRONG */
void entropy_func_len(int len, int ret)
{
    mbedtls_entropy_context ctx;
    unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE + 10] = { 0 };
    unsigned char acc[MBEDTLS_ENTROPY_BLOCK_SIZE + 10] = { 0 };
    size_t i, j;

    mbedtls_entropy_init(&ctx);

    /*
     * See comments in mbedtls_entropy_self_test()
     */
    for (i = 0; i < 8; i++) {
        TEST_ASSERT(mbedtls_entropy_func(&ctx, buf, len) == ret);
        for (j = 0; j < sizeof(buf); j++) {
            acc[j] |= buf[j];
        }
    }

    if (ret == 0) {
        for (j = 0; j < (size_t) len; j++) {
            TEST_ASSERT(acc[j] != 0);
        }
    }

    for (j = len; j < sizeof(buf); j++) {
        TEST_ASSERT(acc[j] == 0);
    }

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

/* BEGIN_CASE */
void entropy_source_fail(char *path)
{
    mbedtls_entropy_context ctx;
    unsigned char buf[16];
    entropy_dummy_context dummy = { DUMMY_FAIL, 0, 0 };

    mbedtls_entropy_init(&ctx);

    TEST_ASSERT(mbedtls_entropy_add_source(&ctx, entropy_dummy_source,
                                           &dummy, 16,
                                           MBEDTLS_ENTROPY_SOURCE_WEAK)
                == 0);

    TEST_ASSERT(mbedtls_entropy_func(&ctx, buf, sizeof(buf))
                == MBEDTLS_ERR_ENTROPY_SOURCE_FAILED);
    TEST_ASSERT(mbedtls_entropy_gather(&ctx)
                == MBEDTLS_ERR_ENTROPY_SOURCE_FAILED);
#if defined(MBEDTLS_FS_IO) && defined(MBEDTLS_ENTROPY_NV_SEED)
    TEST_ASSERT(mbedtls_entropy_write_seed_file(&ctx, path)
                == MBEDTLS_ERR_ENTROPY_SOURCE_FAILED);
    TEST_ASSERT(mbedtls_entropy_update_seed_file(&ctx, path)
                == MBEDTLS_ERR_ENTROPY_SOURCE_FAILED);
#else
    ((void) path);
#endif

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

/* BEGIN_CASE */
void entropy_threshold(int threshold, int chunk_size, int result)
{
    mbedtls_entropy_context ctx;
    entropy_dummy_context strong =
    { DUMMY_CONSTANT_LENGTH, MBEDTLS_ENTROPY_BLOCK_SIZE, 0 };
    entropy_dummy_context weak = { DUMMY_CONSTANT_LENGTH, chunk_size, 0 };
    unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE] = { 0 };
    int ret;

    mbedtls_entropy_init(&ctx);
    entropy_clear_sources(&ctx);

    /* Set strong source that reaches its threshold immediately and
     * a weak source whose threshold is a test parameter. */
    TEST_ASSERT(mbedtls_entropy_add_source(&ctx, entropy_dummy_source,
                                           &strong, 1,
                                           MBEDTLS_ENTROPY_SOURCE_STRONG) == 0);
    TEST_ASSERT(mbedtls_entropy_add_source(&ctx, entropy_dummy_source,
                                           &weak, threshold,
                                           MBEDTLS_ENTROPY_SOURCE_WEAK) == 0);

    ret = mbedtls_entropy_func(&ctx, buf, sizeof(buf));

    if (result >= 0) {
        TEST_ASSERT(ret == 0);
#if defined(MBEDTLS_ENTROPY_NV_SEED)
        /* If the NV seed functionality is enabled, there are two entropy
         * updates: before and after updating the NV seed. */
        result *= 2;
#endif
        TEST_ASSERT(weak.calls == (size_t) result);
    } else {
        TEST_ASSERT(ret == result);
    }

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

/* BEGIN_CASE */
void entropy_calls(int strength1, int strength2,
                   int threshold, int chunk_size,
                   int result)
{
    /*
     * if result >= 0: result = expected number of calls to source 1
     * if result < 0: result = expected return code from mbedtls_entropy_func()
     */

    mbedtls_entropy_context ctx;
    entropy_dummy_context dummy1 = { DUMMY_CONSTANT_LENGTH, chunk_size, 0 };
    entropy_dummy_context dummy2 = { DUMMY_CONSTANT_LENGTH, chunk_size, 0 };
    unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE] = { 0 };
    int ret;

    mbedtls_entropy_init(&ctx);
    entropy_clear_sources(&ctx);

    TEST_ASSERT(mbedtls_entropy_add_source(&ctx, entropy_dummy_source,
                                           &dummy1, threshold,
                                           strength1) == 0);
    TEST_ASSERT(mbedtls_entropy_add_source(&ctx, entropy_dummy_source,
                                           &dummy2, threshold,
                                           strength2) == 0);

    ret = mbedtls_entropy_func(&ctx, buf, sizeof(buf));

    if (result >= 0) {
        TEST_ASSERT(ret == 0);
#if defined(MBEDTLS_ENTROPY_NV_SEED)
        /* If the NV seed functionality is enabled, there are two entropy
         * updates: before and after updating the NV seed. */
        result *= 2;
#endif
        TEST_ASSERT(dummy1.calls == (size_t) result);
    } else {
        TEST_ASSERT(ret == result);
    }

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

/* BEGIN_CASE depends_on:MBEDTLS_ENTROPY_NV_SEED:MBEDTLS_FS_IO */
void nv_seed_file_create()
{
    unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];

    memset(buf, 0, MBEDTLS_ENTROPY_BLOCK_SIZE);

    TEST_ASSERT(write_nv_seed(buf, MBEDTLS_ENTROPY_BLOCK_SIZE) == 0);
}
/* END_CASE */

/* BEGIN_CASE depends_on:MBEDTLS_ENTROPY_NV_SEED:MBEDTLS_FS_IO:MBEDTLS_PLATFORM_NV_SEED_ALT */
void entropy_nv_seed_std_io()
{
    unsigned char io_seed[MBEDTLS_ENTROPY_BLOCK_SIZE];
    unsigned char check_seed[MBEDTLS_ENTROPY_BLOCK_SIZE];

    memset(io_seed, 1, MBEDTLS_ENTROPY_BLOCK_SIZE);
    memset(check_seed, 0, MBEDTLS_ENTROPY_BLOCK_SIZE);

    mbedtls_platform_set_nv_seed(mbedtls_platform_std_nv_seed_read,
                                 mbedtls_platform_std_nv_seed_write);

    /* Check if platform NV read and write manipulate the same data */
    TEST_ASSERT(write_nv_seed(io_seed, MBEDTLS_ENTROPY_BLOCK_SIZE) == 0);
    TEST_ASSERT(mbedtls_nv_seed_read(check_seed, MBEDTLS_ENTROPY_BLOCK_SIZE) ==
                MBEDTLS_ENTROPY_BLOCK_SIZE);

    TEST_ASSERT(memcmp(io_seed, check_seed, MBEDTLS_ENTROPY_BLOCK_SIZE) == 0);

    memset(check_seed, 0, MBEDTLS_ENTROPY_BLOCK_SIZE);

    /* Check if platform NV write and raw read manipulate the same data */
    TEST_ASSERT(mbedtls_nv_seed_write(io_seed, MBEDTLS_ENTROPY_BLOCK_SIZE) ==
                MBEDTLS_ENTROPY_BLOCK_SIZE);
    TEST_ASSERT(read_nv_seed(check_seed, MBEDTLS_ENTROPY_BLOCK_SIZE) == 0);

    TEST_ASSERT(memcmp(io_seed, check_seed, MBEDTLS_ENTROPY_BLOCK_SIZE) == 0);
}
/* END_CASE */

/* BEGIN_CASE depends_on:MBEDTLS_MD_C:MBEDTLS_ENTROPY_NV_SEED:MBEDTLS_PLATFORM_NV_SEED_ALT */
void entropy_nv_seed(data_t *read_seed)
{
#if defined(MBEDTLS_ENTROPY_SHA512_ACCUMULATOR)
    const mbedtls_md_info_t *md_info =
        mbedtls_md_info_from_type(MBEDTLS_MD_SHA512);
#elif defined(MBEDTLS_ENTROPY_SHA256_ACCUMULATOR)
    const mbedtls_md_info_t *md_info =
        mbedtls_md_info_from_type(MBEDTLS_MD_SHA256);
#else
#error "Unsupported entropy accumulator"
#endif
    mbedtls_md_context_t accumulator;
    mbedtls_entropy_context ctx;
    int (*original_mbedtls_nv_seed_read)(unsigned char *buf, size_t buf_len) =
        mbedtls_nv_seed_read;
    int (*original_mbedtls_nv_seed_write)(unsigned char *buf, size_t buf_len) =
        mbedtls_nv_seed_write;

    unsigned char header[2];
    unsigned char entropy[MBEDTLS_ENTROPY_BLOCK_SIZE];
    unsigned char buf[MBEDTLS_ENTROPY_BLOCK_SIZE];
    unsigned char empty[MBEDTLS_ENTROPY_BLOCK_SIZE];
    unsigned char check_seed[MBEDTLS_ENTROPY_BLOCK_SIZE];
    unsigned char check_entropy[MBEDTLS_ENTROPY_BLOCK_SIZE];

    memset(entropy, 0, MBEDTLS_ENTROPY_BLOCK_SIZE);
    memset(buf, 0, MBEDTLS_ENTROPY_BLOCK_SIZE);
    memset(empty, 0, MBEDTLS_ENTROPY_BLOCK_SIZE);
    memset(check_seed, 2, MBEDTLS_ENTROPY_BLOCK_SIZE);
    memset(check_entropy, 3, MBEDTLS_ENTROPY_BLOCK_SIZE);

    // Make sure we read/write NV seed from our buffers
    mbedtls_platform_set_nv_seed(buffer_nv_seed_read, buffer_nv_seed_write);

    mbedtls_md_init(&accumulator);
    mbedtls_entropy_init(&ctx);
    entropy_clear_sources(&ctx);

    TEST_ASSERT(mbedtls_entropy_add_source(&ctx, mbedtls_nv_seed_poll, NULL,
                                           MBEDTLS_ENTROPY_BLOCK_SIZE,
                                           MBEDTLS_ENTROPY_SOURCE_STRONG) == 0);

    // Set the initial NV seed to read
    TEST_ASSERT(read_seed->len >= MBEDTLS_ENTROPY_BLOCK_SIZE);
    memcpy(buffer_seed, read_seed->x, MBEDTLS_ENTROPY_BLOCK_SIZE);

    // Do an entropy run
    TEST_ASSERT(mbedtls_entropy_func(&ctx, entropy, sizeof(entropy)) == 0);
    // Determine what should have happened with manual entropy internal logic

    // Init accumulator
    header[1] = MBEDTLS_ENTROPY_BLOCK_SIZE;
    TEST_ASSERT(mbedtls_md_setup(&accumulator, md_info, 0) == 0);

    // First run for updating write_seed
    header[0] = 0;
    TEST_ASSERT(mbedtls_md_starts(&accumulator) == 0);
    TEST_ASSERT(mbedtls_md_update(&accumulator, header, 2) == 0);
    TEST_ASSERT(mbedtls_md_update(&accumulator,
                                  read_seed->x, MBEDTLS_ENTROPY_BLOCK_SIZE) == 0);
    TEST_ASSERT(mbedtls_md_finish(&accumulator, buf) == 0);

    TEST_ASSERT(mbedtls_md_starts(&accumulator) == 0);
    TEST_ASSERT(mbedtls_md_update(&accumulator,
                                  buf, MBEDTLS_ENTROPY_BLOCK_SIZE) == 0);

    TEST_ASSERT(mbedtls_md(md_info, buf, MBEDTLS_ENTROPY_BLOCK_SIZE,
                           check_seed) == 0);

    // Second run for actual entropy (triggers mbedtls_entropy_update_nv_seed)
    header[0] = MBEDTLS_ENTROPY_SOURCE_MANUAL;
    TEST_ASSERT(mbedtls_md_update(&accumulator, header, 2) == 0);
    TEST_ASSERT(mbedtls_md_update(&accumulator,
                                  empty, MBEDTLS_ENTROPY_BLOCK_SIZE) == 0);

    header[0] = 0;
    TEST_ASSERT(mbedtls_md_update(&accumulator, header, 2) == 0);
    TEST_ASSERT(mbedtls_md_update(&accumulator,
                                  check_seed, MBEDTLS_ENTROPY_BLOCK_SIZE) == 0);
    TEST_ASSERT(mbedtls_md_finish(&accumulator, buf) == 0);

    TEST_ASSERT(mbedtls_md(md_info, buf, MBEDTLS_ENTROPY_BLOCK_SIZE,
                           check_entropy) == 0);

    // Check result of both NV file and entropy received with the manual calculations
    TEST_ASSERT(memcmp(check_seed, buffer_seed, MBEDTLS_ENTROPY_BLOCK_SIZE) == 0);
    TEST_ASSERT(memcmp(check_entropy, entropy, MBEDTLS_ENTROPY_BLOCK_SIZE) == 0);

exit:
    mbedtls_md_free(&accumulator);
    mbedtls_entropy_free(&ctx);
    mbedtls_nv_seed_read = original_mbedtls_nv_seed_read;
    mbedtls_nv_seed_write = original_mbedtls_nv_seed_write;
}
/* END_CASE */

/* BEGIN_CASE depends_on:ENTROPY_HAVE_STRONG:MBEDTLS_SELF_TEST */
void entropy_selftest(int result)
{
    TEST_ASSERT(mbedtls_entropy_self_test(1) == result);
}
/* END_CASE */