Fix an integer wrap around bug and add a couple more tests
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2 changed files with 38 additions and 1 deletions
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@ -116,7 +116,11 @@ void megolm_advance_to(Megolm *megolm, uint32_t advance_to) {
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((advance_to >> shift) - (megolm->counter >> shift)) & 0xff;
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if (steps == 0) {
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continue;
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if (advance_to < megolm->counter) {
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steps = 0x100;
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} else {
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continue;
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}
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}
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/* for all but the last step, we can just bump R(j) without regard
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@ -98,4 +98,37 @@ std::uint8_t random_bytes[] =
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assert_equals(megolm_get_data(&mr2), megolm_get_data(&mr1), MEGOLM_RATCHET_LENGTH);
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}
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{
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TestCase test_case("Megolm::advance overflow by one");
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Megolm mr1, mr2;
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megolm_init(&mr1, random_bytes, 0xffffffffUL);
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megolm_advance_to(&mr1, 0x0);
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assert_equals(0x0U, mr1.counter);
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megolm_init(&mr2, random_bytes, 0xffffffffUL);
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megolm_advance(&mr2);
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assert_equals(0x0U, mr2.counter);
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assert_equals(megolm_get_data(&mr2), megolm_get_data(&mr1), MEGOLM_RATCHET_LENGTH);
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}
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{
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TestCase test_case("Megolm::advance overflow");
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Megolm mr1, mr2;
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megolm_init(&mr1, random_bytes, 0x1UL);
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megolm_advance_to(&mr1, 0x80000000UL);
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megolm_advance_to(&mr1, 0x0);
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assert_equals(0x0U, mr1.counter);
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megolm_init(&mr2, random_bytes, 0x1UL);
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megolm_advance_to(&mr2, 0x0UL);
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assert_equals(0x0U, mr2.counter);
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assert_equals(megolm_get_data(&mr2), megolm_get_data(&mr1), MEGOLM_RATCHET_LENGTH);
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}
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}
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