mbedtls/tests/suites/test_suite_constant_time.function

/* BEGIN_HEADER */
/** \file test_suite_constant_time.function
 *
 * Functional testing of functions in the constant_time module.
 *
 * The tests are instrumented with #TEST_CF_SECRET and #TEST_CF_PUBLIC
 * (see tests/include/test/constant_flow.h) so that running the tests
 * under MSan or Valgrind will detect a non-constant-time implementation.
 */

#include <stdio.h>

#include <limits.h>
#include <stdlib.h>
#include <errno.h>

#include <mbedtls/bignum.h>
#include <mbedtls/constant_time.h>
#include <constant_time_internal.h>

#include <test/constant_flow.h>
/* END_HEADER */

/* BEGIN_CASE */
void mbedtls_ct_memcmp_null()
{
    uint32_t x = 0;
    TEST_ASSERT(mbedtls_ct_memcmp(&x, NULL, 0) == 0);
    TEST_ASSERT(mbedtls_ct_memcmp(NULL, &x, 0) == 0);
    TEST_ASSERT(mbedtls_ct_memcmp(NULL, NULL, 0) == 0);
}
/* END_CASE */

/* BEGIN_CASE */
void mbedtls_ct_bool(char *input)
{
    mbedtls_ct_uint_t v = (mbedtls_ct_uint_t) strtoull(input, NULL, 16);
    TEST_ASSERT(errno == 0);

    mbedtls_ct_condition_t expected = (v != 0) ? MBEDTLS_CT_TRUE : MBEDTLS_CT_FALSE;
    TEST_CF_SECRET(&v, sizeof(v));
    TEST_EQUAL(mbedtls_ct_bool(v), expected);
    TEST_CF_PUBLIC(&v, sizeof(v));
}
/* END_CASE */

/* BEGIN_CASE */
void mbedtls_ct_bool_xxx(char *x_str, char *y_str)
{
    mbedtls_ct_uint_t x = strtoull(x_str, NULL, 0);
    mbedtls_ct_uint_t y = strtoull(y_str, NULL, 0);

    mbedtls_ct_uint_t x1 = x;
    mbedtls_ct_uint_t y1 = y;

    TEST_CF_SECRET(&x, sizeof(x));
    TEST_CF_SECRET(&y, sizeof(y));

    mbedtls_ct_condition_t expected = x1 ? MBEDTLS_CT_FALSE : MBEDTLS_CT_TRUE;
    TEST_EQUAL(mbedtls_ct_bool_not(mbedtls_ct_bool(x)), expected);

    expected = x1 != y1 ? MBEDTLS_CT_TRUE : MBEDTLS_CT_FALSE;
    TEST_EQUAL(mbedtls_ct_uint_ne(x, y), expected);

    expected = x1 == y1 ? MBEDTLS_CT_TRUE : MBEDTLS_CT_FALSE;
    TEST_EQUAL(mbedtls_ct_uint_eq(x, y), expected);

    expected = x1 > y1 ? MBEDTLS_CT_TRUE : MBEDTLS_CT_FALSE;
    TEST_EQUAL(mbedtls_ct_uint_gt(x, y), expected);

    expected = x1 < y1 ? MBEDTLS_CT_TRUE : MBEDTLS_CT_FALSE;
    TEST_EQUAL(mbedtls_ct_uint_lt(x, y), expected);

    expected = x1 >= y1 ? MBEDTLS_CT_TRUE : MBEDTLS_CT_FALSE;
    TEST_EQUAL(mbedtls_ct_uint_ge(x, y), expected);

    expected = x1 <= y1 ? MBEDTLS_CT_TRUE : MBEDTLS_CT_FALSE;
    TEST_EQUAL(mbedtls_ct_uint_le(x, y), expected);

    expected = (!!x1) != (!!y1) ? MBEDTLS_CT_TRUE : MBEDTLS_CT_FALSE;
    TEST_EQUAL(mbedtls_ct_bool_ne(mbedtls_ct_bool(x), mbedtls_ct_bool(y)), expected);

    expected = (!!x1) && (!!y1) ? MBEDTLS_CT_TRUE : MBEDTLS_CT_FALSE;
    TEST_EQUAL(mbedtls_ct_bool_and(mbedtls_ct_bool(x), mbedtls_ct_bool(y)), expected);

    expected = (!!x1) || (!!y1) ? MBEDTLS_CT_TRUE : MBEDTLS_CT_FALSE;
    TEST_EQUAL(mbedtls_ct_bool_or(mbedtls_ct_bool(x), mbedtls_ct_bool(y)), expected);

    TEST_CF_PUBLIC(&x, sizeof(x));
    TEST_CF_PUBLIC(&y, sizeof(y));
}
/* END_CASE */

/* BEGIN_CASE depends_on:MBEDTLS_BASE64_C */
void mbedtls_ct_uchar_in_range_if(int li, int hi, int ti)
{
    unsigned char l = li, h = hi, t = ti;

    for (unsigned x = 0; x <= 255; x++) {
        unsigned char expected = (x >= l) && (x <= h) ? t : 0;

        TEST_CF_SECRET(&x, sizeof(x));
        TEST_CF_SECRET(&l, sizeof(l));
        TEST_CF_SECRET(&h, sizeof(h));
        TEST_CF_SECRET(&t, sizeof(t));

        TEST_EQUAL(mbedtls_ct_uchar_in_range_if(l, h, (unsigned char) x, t), expected);

        TEST_CF_PUBLIC(&x, sizeof(x));
        TEST_CF_PUBLIC(&l, sizeof(l));
        TEST_CF_PUBLIC(&h, sizeof(h));
        TEST_CF_PUBLIC(&t, sizeof(t));
    }
}
/* END_CASE */

/* BEGIN_CASE */
void mbedtls_ct_if(char *c_str, char *t_str, char *f_str)
{
    mbedtls_ct_condition_t c = mbedtls_ct_bool(strtoull(c_str, NULL, 16));
    mbedtls_ct_uint_t t = (mbedtls_ct_uint_t) strtoull(t_str, NULL, 16);
    mbedtls_ct_uint_t f = (mbedtls_ct_uint_t) strtoull(f_str, NULL, 16);

    mbedtls_ct_uint_t expected = c ? t : f;
    mbedtls_ct_uint_t expected0 = c ? t : 0;

    TEST_CF_SECRET(&c, sizeof(c));
    TEST_CF_SECRET(&t, sizeof(t));
    TEST_CF_SECRET(&f, sizeof(f));

    TEST_EQUAL(mbedtls_ct_if(c, t, f), expected);
    TEST_EQUAL(mbedtls_ct_size_if(c, t, f), (size_t) expected);
    TEST_EQUAL(mbedtls_ct_uint_if(c, t, f), (unsigned) expected);
#if defined(MBEDTLS_BIGNUM_C)
    TEST_EQUAL(mbedtls_ct_mpi_uint_if(c, t, f), (mbedtls_mpi_uint) expected);
#endif

    TEST_EQUAL(mbedtls_ct_uint_if_else_0(c, t), (unsigned) expected0);
    TEST_EQUAL(mbedtls_ct_size_if_else_0(c, (size_t) t), (size_t) expected0);
#if defined(MBEDTLS_BIGNUM_C)
    TEST_EQUAL(mbedtls_ct_mpi_uint_if_else_0(c, t), (mbedtls_mpi_uint) expected0);
#endif

    TEST_CF_PUBLIC(&c, sizeof(c));
    TEST_CF_PUBLIC(&t, sizeof(t));
    TEST_CF_PUBLIC(&f, sizeof(f));
}
/* END_CASE */

/* BEGIN_CASE depends_on:MBEDTLS_PKCS1_V15:MBEDTLS_RSA_C:!MBEDTLS_RSA_ALT */
void mbedtls_ct_zeroize_if(char *c_str, int len)
{
    uint8_t *buf = NULL;
    mbedtls_ct_condition_t c = mbedtls_ct_bool(strtoull(c_str, NULL, 16));

    TEST_CALLOC(buf, len);
    for (size_t i = 0; i < (size_t) len; i++) {
        buf[i] = 1;
    }

    TEST_CF_SECRET(&c, sizeof(c));
    TEST_CF_SECRET(buf, len);
    mbedtls_ct_zeroize_if(c, buf, len);
    TEST_CF_PUBLIC(&c, sizeof(c));
    TEST_CF_PUBLIC(buf, len);

    for (size_t i = 0; i < (size_t) len; i++) {
        TEST_EQUAL(buf[i], c != 0 ? 0 : 1);
    }
exit:
    mbedtls_free(buf);
}
/* END_CASE */

/* BEGIN_CASE */
void mbedtls_ct_memcmp_single_bit_diff()
{
    uint8_t *a = NULL, *b = NULL;
    size_t size = 32;
    TEST_CALLOC(a, size);
    TEST_CALLOC(b, size);

    TEST_CF_SECRET(a, size);
    TEST_CF_SECRET(b, size);
    int result = mbedtls_ct_memcmp(a, b, size);
    TEST_CF_PUBLIC(a, size);
    TEST_CF_PUBLIC(b, size);
    TEST_CF_PUBLIC(&result, sizeof(result));

    TEST_EQUAL(result, 0);

    for (size_t offset = 0; offset < size; offset++) {
        for (size_t bit_offset = 0; bit_offset < 8; bit_offset++) {
            /* Set a single bit to be different at given offset, to test that we
               detect single-bit differences */
            a[offset] = 1 << bit_offset;

            TEST_CF_SECRET(a, size);
            TEST_CF_SECRET(b, size);
            result = mbedtls_ct_memcmp(a, b, size);
            TEST_CF_PUBLIC(a, size);
            TEST_CF_PUBLIC(b, size);
            TEST_CF_PUBLIC(&result, sizeof(result));

            TEST_ASSERT(result != 0);

            a[offset] = 0;
        }
    }


exit:
    mbedtls_free(a);
    mbedtls_free(b);
}
/* END_CASE */

/* BEGIN_CASE */
void mbedtls_ct_memcmp(int same, int size, int offset)
{
    uint8_t *a = NULL, *b = NULL;
    TEST_CALLOC(a, size + offset);
    TEST_CALLOC(b, size + offset);

    /* Construct data that matches, if same == -1, otherwise
     * same gives the number of bytes (after the initial offset)
     * that will match; after that it will differ.
     */
    for (int i = 0; i < size + offset; i++) {
        a[i] = i & 0xff;
        if (same == -1 || (i - offset) < same) {
            b[i] = a[i];
        } else {
            b[i] = (i + 1) & 0xff;
        }
    }

    int reference = memcmp(a + offset, b + offset, size);

    TEST_CF_SECRET(a, size + offset);
    TEST_CF_SECRET(b, size + offset);

    int actual = mbedtls_ct_memcmp(a + offset, b + offset, size);

    TEST_CF_PUBLIC(a, size + offset);
    TEST_CF_PUBLIC(b, size + offset);
    TEST_CF_PUBLIC(&actual, sizeof(actual));

    if (same == -1 || same >= size) {
        TEST_ASSERT(reference == 0);
        TEST_ASSERT(actual == 0);
    } else {
        TEST_ASSERT(reference != 0);
        TEST_ASSERT(actual != 0);
    }
exit:
    mbedtls_free(a);
    mbedtls_free(b);
}
/* END_CASE */

/* BEGIN_CASE depends_on:MBEDTLS_NIST_KW_C */

/**
 * Generate two arrays of the given size, and test mbedtls_ct_memcmp_partial
 * over them. The arrays will be identical, except that one byte may be specified
 * to be different.
 *
 * \p diff      Index of byte that differs (if out of range, the arrays will match).
 * \p size      Size of arrays to compare
 * \p skip_head Leading bytes to skip, as per mbedtls_ct_memcmp_partial
 * \p skip_tail Trailing bytes to skip, as per mbedtls_ct_memcmp_partial
 */
void mbedtls_ct_memcmp_partial(int diff, int size, int skip_head, int skip_tail)
{
    uint8_t *a = NULL, *b = NULL;

    TEST_CALLOC_NONNULL(a, size);
    TEST_CALLOC_NONNULL(b, size);

    TEST_ASSERT((skip_head + skip_tail) <= size);

    /* Construct data that matches, except for specified byte (if in range). */
    for (int i = 0; i < size; i++) {
        a[i] = i & 0xff;
        b[i] = a[i];
        if (i == diff) {
            // modify the specified byte
            b[i] ^= 1;
        }
    }

    int reference = memcmp(a + skip_head, b + skip_head, size - skip_head - skip_tail);

    TEST_CF_SECRET(a, size);
    TEST_CF_SECRET(b, size);

    int actual = mbedtls_ct_memcmp_partial(a, b, size, skip_head, skip_tail);

    TEST_CF_PUBLIC(a, size);
    TEST_CF_PUBLIC(b, size);
    TEST_CF_PUBLIC(&actual, sizeof(actual));

    TEST_EQUAL(!!reference, !!actual);
exit:
    mbedtls_free(a);
    mbedtls_free(b);
}
/* END_CASE */

/* BEGIN_CASE */
void mbedtls_ct_memcpy_if(int eq, int size, int offset)
{
    uint8_t *src = NULL, *src2 = NULL, *result = NULL, *expected = NULL;
    TEST_CALLOC(src, size + offset);
    TEST_CALLOC(src2, size + offset);
    TEST_CALLOC(result, size + offset);
    TEST_CALLOC(expected, size + offset);

    /* Apply offset to result only */
    for (int i = 0; i < size + offset; i++) {
        src[i]      = 1;
        result[i]   = 0xff;
        expected[i] = eq ? 1 : 0xff;
    }

    int secret_eq = eq;
    TEST_CF_SECRET(&secret_eq, sizeof(secret_eq));
    TEST_CF_SECRET(src, size + offset);
    TEST_CF_SECRET(result, size + offset);

    mbedtls_ct_memcpy_if(mbedtls_ct_bool(secret_eq), result + offset, src, NULL, size);

    TEST_CF_PUBLIC(&secret_eq, sizeof(secret_eq));
    TEST_CF_PUBLIC(src, size + offset);
    TEST_CF_PUBLIC(result, size + offset);

    TEST_MEMORY_COMPARE(expected, size, result + offset, size);


    /* Apply offset to src only */
    for (int i = 0; i < size + offset; i++) {
        src[i]    = 1;
        result[i] = 0xff;
        expected[i] = eq ? 1 : 0xff;
    }

    TEST_CF_SECRET(&secret_eq, sizeof(secret_eq));
    TEST_CF_SECRET(src, size + offset);
    TEST_CF_SECRET(result, size + offset);

    mbedtls_ct_memcpy_if(mbedtls_ct_bool(secret_eq), result, src + offset, NULL, size);

    TEST_CF_PUBLIC(&secret_eq, sizeof(secret_eq));
    TEST_CF_PUBLIC(src, size + offset);
    TEST_CF_PUBLIC(result, size + offset);

    TEST_MEMORY_COMPARE(expected, size, result, size);


    /* Apply offset to src and src2 */
    for (int i = 0; i < size + offset; i++) {
        src[i]      = 1;
        src2[i]     = 2;
        result[i]   = 0xff;
        expected[i] = eq ? 1 : 2;
    }

    TEST_CF_SECRET(&secret_eq, sizeof(secret_eq));
    TEST_CF_SECRET(src, size + offset);
    TEST_CF_SECRET(src2, size + offset);
    TEST_CF_SECRET(result, size + offset);

    mbedtls_ct_memcpy_if(mbedtls_ct_bool(secret_eq), result, src + offset, src2 + offset, size);

    TEST_CF_PUBLIC(&secret_eq, sizeof(secret_eq));
    TEST_CF_PUBLIC(src, size + offset);
    TEST_CF_SECRET(src2, size + offset);
    TEST_CF_PUBLIC(result, size + offset);

    TEST_MEMORY_COMPARE(expected, size, result, size);


    /* result == src == dest */
    for (int i = 0; i < size + offset; i++) {
        src[i]      = 2;
        expected[i] = 2;
    }

    TEST_CF_SECRET(&secret_eq, sizeof(secret_eq));
    TEST_CF_SECRET(src, size + offset);
    TEST_CF_SECRET(result, size + offset);

    mbedtls_ct_memcpy_if(mbedtls_ct_bool(secret_eq), src + offset, src + offset, src + offset,
                         size);

    TEST_CF_PUBLIC(&secret_eq, sizeof(secret_eq));
    TEST_CF_PUBLIC(src, size + offset);
    TEST_CF_PUBLIC(result, size + offset);

    TEST_MEMORY_COMPARE(expected, size, src + offset, size);
exit:
    mbedtls_free(src);
    mbedtls_free(src2);
    mbedtls_free(result);
    mbedtls_free(expected);
}
/* END_CASE */

/* BEGIN_CASE depends_on:MBEDTLS_PKCS1_V15:MBEDTLS_RSA_C:!MBEDTLS_RSA_ALT */
void mbedtls_ct_memmove_left(int len, int offset)
{
    size_t l = (size_t) len;
    size_t o = (size_t) offset;

    uint8_t *buf = NULL, *buf_expected = NULL;
    TEST_CALLOC(buf, l);
    TEST_CALLOC(buf_expected, l);

    for (size_t i = 0; i < l; i++) {
        buf[i] = (uint8_t) i;
        buf_expected[i] = buf[i];
    }

    TEST_CF_SECRET(&o, sizeof(o));
    TEST_CF_SECRET(buf, l);
    mbedtls_ct_memmove_left(buf, l, o);
    TEST_CF_PUBLIC(&o, sizeof(o));
    TEST_CF_PUBLIC(buf, l);

    if (l > 0) {
        memmove(buf_expected, buf_expected + o, l - o);
        memset(buf_expected + (l - o), 0, o);
        TEST_ASSERT(memcmp(buf, buf_expected, l) == 0);
    }
exit:
    mbedtls_free(buf);
    mbedtls_free(buf_expected);
}
/* END_CASE */

/* BEGIN_CASE */
void mbedtls_ct_memcpy_offset(int offset_min, int offset_max, int len)
{
    unsigned char *dst = NULL;
    unsigned char *src = NULL;
    size_t src_len = offset_max + len;
    size_t secret;

    TEST_CALLOC(dst, len);
    TEST_CALLOC(src, src_len);

    /* Fill src in a way that we can detect if we copied the right bytes */
    mbedtls_test_rnd_std_rand(NULL, src, src_len);

    for (secret = offset_min; secret <= (size_t) offset_max; secret++) {
        mbedtls_test_set_step((int) secret);

        TEST_CF_SECRET(&secret, sizeof(secret));
        TEST_CF_SECRET(src, len);
        TEST_CF_SECRET(dst, len);
        mbedtls_ct_memcpy_offset(dst, src, secret,
                                 offset_min, offset_max, len);
        TEST_CF_PUBLIC(&secret, sizeof(secret));
        TEST_CF_PUBLIC(src, len);
        TEST_CF_PUBLIC(dst, len);

        TEST_MEMORY_COMPARE(dst, len, src + secret, len);
    }

exit:
    mbedtls_free(dst);
    mbedtls_free(src);
}
/* END_CASE */