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AK: Fix signed overflow in unix time parts parsing

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Ben Wiederhake 2023-05-24 22:06:39 +02:00 committed by Jelle Raaijmakers
parent 815ea06d2c
commit 9d40ecacb5
Notes: sideshowbarker 2024-07-17 03:00:02 +09:00 
Author: https://github.com/BenWiederhake
Commit: https://github.com/SerenityOS/serenity/commit/9d40ecacb5
Pull-request: https://github.com/SerenityOS/serenity/pull/19029
Reviewed-by: https://github.com/gmta ✅
Reviewed-by: https://github.com/kleinesfilmroellchen ✅
2 changed files with 49 additions and 11 deletions
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22
AK/Time.h
View file

@ -381,20 +381,20 @@ public:
// Note that the returned time is probably not equivalent to the same timestamp in UTC time, since UNIX time does not observe leap seconds.
[[nodiscard]] constexpr static UnixDateTime from_unix_time_parts(i32 year, u8 month, u8 day, u8 hour, u8 minute, u8 second, u16 millisecond)
{
constexpr auto milliseconds_per_day = 86'400'000;
constexpr auto milliseconds_per_hour = 3'600'000;
constexpr auto milliseconds_per_minute = 60'000;
constexpr auto milliseconds_per_second = 1'000;
constexpr auto seconds_per_day = 86'400;
constexpr auto seconds_per_hour = 3'600;
constexpr auto seconds_per_minute = 60;
i64 days = days_since_epoch(year, month, day);
i64 milliseconds_since_epoch = days * milliseconds_per_day;
// With year=2'147'483'648, we can end up with days=569'603'931'504.
// Expressing that in milliseconds would require more than 64 bits,
// so we must choose seconds here, and not milliseconds.
i64 seconds_since_epoch = days * seconds_per_day;
milliseconds_since_epoch += hour * milliseconds_per_hour;
milliseconds_since_epoch += minute * milliseconds_per_minute;
milliseconds_since_epoch += second * milliseconds_per_second;
milliseconds_since_epoch += millisecond;
return from_milliseconds_since_epoch(milliseconds_since_epoch);
seconds_since_epoch += hour * seconds_per_hour;
seconds_since_epoch += minute * seconds_per_minute;
seconds_since_epoch += second;
return from_seconds_since_epoch(seconds_since_epoch) + Duration::from_milliseconds(millisecond);
}
[[nodiscard]] constexpr static UnixDateTime from_seconds_since_epoch(i64 seconds)

38
Tests/AK/TestDuration.cpp
View file

@ -608,3 +608,41 @@ TEST_CASE(from_milliseconds)
EXPECT_DURATION(Duration::from_milliseconds(9223372036854775807), 9223372036854775, 807'000'000);
EXPECT_DURATION(Duration::from_milliseconds((i64)-0x8000'0000'0000'0000), -9223372036854776, 192'000'000);
}
TEST_CASE(from_unix_time_parts_overflow)
{
// Negative overflow
// I can't easily verify that these values are perfectly exact and correct, but they're close enough.
// Also, for these "years" the most important thing is to avoid crashing (i.e. signed overflow UB).
EXPECT_DURATION(UnixDateTime::from_unix_time_parts(0, 1, 1, 0, 0, 0, 0).offset_to_epoch(), -62167219200, 0); // Guess: -62167195440, off by 23760 seconds
EXPECT_DURATION(UnixDateTime::from_unix_time_parts(-1'000'000, 1, 1, 0, 0, 0, 0).offset_to_epoch(), -31619119219200, 0); // Guess: -31619119195440, off by the same 23760 seconds
EXPECT_DURATION(UnixDateTime::from_unix_time_parts(-2'147'483'648, 1, 1, 0, 0, 0, 0).offset_to_epoch(), -67768100567971200, 0); // Guess: -67768100567916336, off by 54864 seconds
EXPECT_DURATION(UnixDateTime::from_unix_time_parts(-2'147'483'648, 1, 0, 0, 0, 0, 0).offset_to_epoch(), -67768100568057600, 0); // Guess: -67768100568002736, off by the same 54864 seconds
// EXPECT_DURATION(UnixDateTime::from_unix_time_parts(-2'147'483'648, 0, 0, 0, 0, 0, 0).offset_to_epoch(), -67768100568006336, 0); // Guess: -67768100568006336
EXPECT_CRASH("Month 0 currently not allowed", [] {
(void)UnixDateTime::from_unix_time_parts(-2'147'483'648, 0, 0, 0, 0, 0, 0);
return Test::Crash::Failure::DidNotCrash;
});
// Positive overflow
EXPECT_DURATION(UnixDateTime::from_unix_time_parts(1970, 1, 1, 0, 0, 0, 65535).offset_to_epoch(), 65, 535'000'000);
EXPECT_DURATION(UnixDateTime::from_unix_time_parts(1970, 1, 1, 0, 0, 255, 0).offset_to_epoch(), 255, 0);
EXPECT_DURATION(UnixDateTime::from_unix_time_parts(1970, 1, 1, 0, 255, 0, 0).offset_to_epoch(), 15300, 0);
EXPECT_DURATION(UnixDateTime::from_unix_time_parts(1970, 1, 1, 255, 0, 0, 0).offset_to_epoch(), 918000, 0);
EXPECT_DURATION(UnixDateTime::from_unix_time_parts(1970, 1, 255, 0, 0, 0, 0).offset_to_epoch(), 21945600, 0);
EXPECT_DURATION(UnixDateTime::from_unix_time_parts(1970, 12, 1, 0, 0, 0, 0).offset_to_epoch(), 28857600, 0);
// EXPECT_DURATION(UnixDateTime::from_unix_time_parts(1970, 255, 1, 0, 0, 0, 0).offset_to_epoch(), 670585230, 0);
EXPECT_CRASH("Month 255 currently crashes", [] {
(void)UnixDateTime::from_unix_time_parts(1970, 255, 1, 0, 0, 0, 0);
return Test::Crash::Failure::DidNotCrash;
});
EXPECT_DURATION(UnixDateTime::from_unix_time_parts(1'000'000, 1, 1, 0, 0, 0, 0).offset_to_epoch(), 31494784780800, 0);
EXPECT_DURATION(UnixDateTime::from_unix_time_parts(2'147'483'647, 1, 1, 0, 0, 0, 0).offset_to_epoch(), 67767976201996800, 0);
EXPECT_DURATION(UnixDateTime::from_unix_time_parts(2'147'483'647, 12, 255, 0, 0, 0, 0).offset_to_epoch(), 67767976252800000, 0);
EXPECT_DURATION(UnixDateTime::from_unix_time_parts(2'147'483'647, 12, 255, 255, 255, 255, 65535).offset_to_epoch(), 67767976253733620, 535'000'000);
// EXPECT_DURATION(UnixDateTime::from_unix_time_parts(2'147'483'647, 255, 255, 255, 255, 255, 65535).offset_to_epoch(), ????, 535'000'000);
EXPECT_CRASH("Month 255 currently crashes", [] {
(void)UnixDateTime::from_unix_time_parts(2'147'483'647, 255, 255, 255, 255, 255, 65535);
return Test::Crash::Failure::DidNotCrash;
});
}