mirror of
https://github.com/TokTok/c-toxcore
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iphydf
92 lines
2.9 KiB
C++
92 lines
2.9 KiB
C++
#include "crypto_core.h"
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#include <algorithm>
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#include <gtest/gtest.h>
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namespace {
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enum {
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/**
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* The size of the arrays to compare. This was chosen to take around 2000
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* CPU clocks on x86_64.
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*/
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CRYPTO_TEST_MEMCMP_SIZE = 1024 * 1024, // 1 MiB
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/**
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* The number of times we run memcmp in the test.
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*
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* We compute the median time taken to reduce error margins.
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*/
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CRYPTO_TEST_MEMCMP_ITERATIONS = 500,
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/**
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* The margin of error (in clocks) we allow for this test.
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*
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* Should be within 0.5% of ~2000 CPU clocks. In reality, the code is much
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* more precise and is usually within 1 CPU clock.
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*/
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CRYPTO_TEST_MEMCMP_EPS = 10,
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};
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clock_t memcmp_time(void *a, void *b, size_t len) {
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clock_t start = clock();
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crypto_memcmp(a, b, len);
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return clock() - start;
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}
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/**
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* This function performs the actual timing. It interleaves comparison of
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* equal and non-equal arrays to reduce the influence of external effects
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* such as the machine being a little more busy 1 second later.
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*/
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void memcmp_median(void *src, void *same, void *not_same, size_t len, clock_t *same_median,
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clock_t *not_same_median) {
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clock_t same_results[CRYPTO_TEST_MEMCMP_ITERATIONS];
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clock_t not_same_results[CRYPTO_TEST_MEMCMP_ITERATIONS];
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for (size_t i = 0; i < CRYPTO_TEST_MEMCMP_ITERATIONS; i++) {
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same_results[i] = memcmp_time(src, same, len);
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not_same_results[i] = memcmp_time(src, not_same, len);
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}
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std::sort(same_results, same_results + CRYPTO_TEST_MEMCMP_ITERATIONS);
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*same_median = same_results[CRYPTO_TEST_MEMCMP_ITERATIONS / 2];
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std::sort(not_same_results, not_same_results + CRYPTO_TEST_MEMCMP_ITERATIONS);
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*not_same_median = not_same_results[CRYPTO_TEST_MEMCMP_ITERATIONS / 2];
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}
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/**
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* This test checks whether crypto_memcmp takes the same time for equal and
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* non-equal chunks of memory.
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*/
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TEST(CryptoCore, MemcmpTimingIsDataIndependent) {
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// A random piece of memory.
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auto *src = new uint8_t[CRYPTO_TEST_MEMCMP_SIZE];
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random_bytes(src, CRYPTO_TEST_MEMCMP_SIZE);
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// A separate piece of memory containing the same data.
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auto *same = new uint8_t[CRYPTO_TEST_MEMCMP_SIZE];
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memcpy(same, src, CRYPTO_TEST_MEMCMP_SIZE);
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// Another piece of memory containing different data.
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auto *not_same = new uint8_t[CRYPTO_TEST_MEMCMP_SIZE];
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random_bytes(not_same, CRYPTO_TEST_MEMCMP_SIZE);
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clock_t same_median;
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clock_t not_same_median;
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memcmp_median(src, same, not_same, CRYPTO_TEST_MEMCMP_SIZE, &same_median, ¬_same_median);
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delete[] not_same;
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delete[] same;
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delete[] src;
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clock_t const delta =
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same_median > not_same_median ? same_median - not_same_median : not_same_median - same_median;
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EXPECT_LT(delta, CRYPTO_TEST_MEMCMP_EPS)
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<< "Delta time is too long (" << delta << " >= " << CRYPTO_TEST_MEMCMP_EPS << ")\n"
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<< "Time of the same data comparation: " << same_median << " clocks\n"
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<< "Time of the different data comparation: " << not_same_median << " clocks";
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}
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} // namespace
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