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date: detect underflow/overflow when parsing dates with timezone offset

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Overriding the date of a commit to be close to "1970-01-01 00:00:00"
with a large enough positive timezone for the equivelant GMT time to be
before the epoch is considered valid by `parse_date_basic`. Similar
behaviour occurs when using a date close to "2099-12-31 23:59:59" (the
maximum date allowed by `tm_to_time_t`) with a large enough negative
timezone offset.

This leads to an integer underflow or underflow respectively in the
commit timestamp, which is not caught by `git-commit`, but will cause
other services to fail, such as `git-fsck`, which, for the first case,
reports "badDateOverflow: invalid author/committer line - date causes
integer overflow".

Instead check the timezone offset and fail if the resulting time comes
before the epoch "1970-01-01T00:00:00Z" or after the maximum date
"2099-12-31T23:59:59Z".

Using the REQUIRE_64BIT_TIME prerequisite, make sure that the tests
near the end of Git time (aka end of year 2099) are not attempted on
purely 32-bit systems, as they cannot express timestamp beyond 2038
anyway.

Signed-off-by: Darcy Burke <acednes@gmail.com>
[jc: fixups for 32-bit platforms]
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Darcy Burke
2024-06-25 16:12:48 -07:00
committed by Junio C Hamano
parent a59275d5d6
commit 9d69789770
2 changed files with 44 additions and 1 deletions
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12
date.c
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@ -868,6 +868,10 @@ static int match_object_header_date(const char *date, timestamp_t *timestamp, in
return 0;
}
/* timestamp of 2099-12-31T23:59:59Z, including 32 leap days */
static const timestamp_t timestamp_max = (((timestamp_t)2100 - 1970) * 365 + 32) * 24 * 60 * 60 - 1;
/* Gr. strptime is crap for this; it doesn't have a way to require RFC2822
(i.e. English) day/month names, and it doesn't work correctly with %z. */
int parse_date_basic(const char *date, timestamp_t *timestamp, int *offset)
@ -937,8 +941,14 @@ int parse_date_basic(const char *date, timestamp_t *timestamp, int *offset)
}
}
if (!tm_gmt)
if (!tm_gmt) {
if (*offset > 0 && *offset * 60 > *timestamp)
return -1;
if (*offset < 0 && -*offset * 60 > timestamp_max - *timestamp)
return -1;
*timestamp -= *offset * 60;
}
return 0; /* success */
}