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sudoers: fix leap year calculation in getdate() - #595
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get_date() counts the days between EPOCH and the requested year with Julian += 365 + (i % 4 == 0); which treats every year divisible by 4 as a leap year. Century years that are not divisible by 400 (2100, 2200, 2300, ...) are therefore counted with an extra day. Any date in a later year is then computed too large by one day for every such year that has passed, e.g. "Jan 1, 2101" is returned as Jan 2, and "Jan 1, 2300" is off by two days. Use the full Gregorian rule, as is already done for DaysInMonth[1]. The generated getdate.c contains a copy of the same function, so update it as well. Fixes: sudo-project#446 Signed-off-by: mahailiang <[email protected]>
millert
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Nov 12, 2026
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Looks correct. I guess this counts as "future-proofing".
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Summary
get_date()(inplugins/sudoers/getdate.y) counts the days betweenEPOCH and the requested year with:
Every year divisible by 4 is treated as a leap year. Century years not
divisible by 400 (2100, 2200, 2300, ...) are counted with one extra day,
so dates in later years are computed too large by one day per such year
that has passed. For example:
The
DaysInMonth[1]calculation a few lines above already uses the fullGregorian rule; the day-count loop was missed.
Fix
Use the same rule for the year loop:
getdate.cis a generated file but is checked in, and it carries a copyof
Convert(), so both files are updated identically.This function is used by
sudoreplayto parsefromdate/todate.Testing
Built
sudofrom this branch in a mock UOS 25 x86_64 chroot withgcc 12.3.1 (
configure --disable-nls --disable-python && make -j),with no new warnings.
For a behavior test, a small harness was linked against the generated
getdate.oand the old implementation (the singlei % 4 == 0expression) was compiled side by side. Results with
TZ=UTC, comparedwith GNU
date -u:The old values are exactly one day (86400 s) too large per non-leap
century year; the patched values match GNU date. Note that 2100 itself
is still correct in the old code because the loop only counts years
before the requested one; the error starts with 2101, when 2100 is
included in the sum.
Fixes #446