Re: [PATCH v2] libuuid: Fix pre-1970 UUID v1 timestamp wraparound

Yes I could work on this. I'll change pre-Unix-epoch v1/v6 UUID
timestamps to be treated as an error. uuid_time_v1() and
uuid_time_v6() will detect underflow, return failure, and
__uuid_time() will propagate it by returning -1 and setting tv_sec =
tv_usec = -1, unless you have any objections.


On Tue, Dec 16, 2025 at 8:08 AM Thomas Weißschuh <[email protected]> wrote:
>
> On 2025-12-13 20:01:08-0500, Kiran Rangoon wrote:
> > gregorian_to_unix now returns -1 and sets errno=EOVERFLOW
> > for timestamps before the Unix epoch. uuid_time_v1 and uuid_time_v6
> > now use signed arithmetic to prevent unsigned wraparound.
> >
> > This fixes uuidparse displaying far-future dates for historical UUIDs.
> >
> > The regression test has been updated to show actual result instead of hardcoded wrong
> > date.
>
> Thanks!
>
> >
> > Example output:
> >     $ ./build/uuidparse bf2eb110-d788-1003-aa59-ce1e9e293641
> > Before:
> >     60041-08-13 16:41:36,271592-04:00
> > After:
> >     1969-12-31 19:00:00,000000-05:00
> >
> > Handling negative timestamps gracefully would require broader changes,
> > so I’ve kept this patch focused on preventing pre-1970 wraparound.
>
> IMO we should to this properly. Is this something you want to work on?
>
> > Signed-off-by: Kiran Rangoon <[email protected]>
> > ---
> >  libuuid/src/uuid_time.c       | 15 +++++++++++----
> >  tests/expected/uuid/uuidparse |  2 +-
> >  2 files changed, 12 insertions(+), 5 deletions(-)
> >
> > diff --git a/libuuid/src/uuid_time.c b/libuuid/src/uuid_time.c
> > index c7516152b..f0d2c8f36 100644
> > --- a/libuuid/src/uuid_time.c
> > +++ b/libuuid/src/uuid_time.c
> > @@ -60,15 +60,22 @@
> >  /* prototype to make compiler happy */
> >  time_t __uuid_time(const uuid_t uu, struct timeval *ret_tv);
> >
> > -static uint64_t gregorian_to_unix(uint64_t ts)
> > +static int64_t gregorian_to_unix(uint64_t ts)
> >  {
> > -     return ts - ((((uint64_t) 0x01B21DD2) << 32) + 0x13814000);
> > +    const uint64_t offset = 0x01B21DD213814000ULL;
> > +
> > +    if (ts < offset) {
> > +        errno = EOVERFLOW;
> > +        return -1;
>
> The callers do not check for errors. Instead this gets converted to the
> epoch only by chance.
>
> > +    }
> > +
> > +    return ts - offset;
> >  }
> >
> >  static void uuid_time_v1(const struct uuid *uuid, struct timeval *tv)
> >  {
> >       uint32_t high;
> > -     uint64_t clock_reg;
> > +     int64_t clock_reg;
> >
> >       high = uuid->time_mid | ((uuid->time_hi_and_version & 0xFFF) << 16);
> >       clock_reg = uuid->time_low | ((uint64_t) high << 32);
> > @@ -80,7 +87,7 @@ static void uuid_time_v1(const struct uuid *uuid, struct timeval *tv)
> >
> >  static void uuid_time_v6(const struct uuid *uuid, struct timeval *tv)
> >  {
> > -     uint64_t clock_reg;
> > +     int64_t clock_reg;
> >
> >       clock_reg = uuid->time_low;
> >       clock_reg <<= 16;
> > diff --git a/tests/expected/uuid/uuidparse b/tests/expected/uuid/uuidparse
> > index 9edb05e4e..0f521a760 100644
> > --- a/tests/expected/uuid/uuidparse
> > +++ b/tests/expected/uuid/uuidparse
> > @@ -11,7 +11,7 @@ UUID                                  VARIANT   TYPE       TIME
> >  00000000-0000-3000-8000-000000000000  DCE       name-based
> >  00000000-0000-4000-8000-000000000000  DCE       random
> >  00000000-0000-5000-8000-000000000000  DCE       sha1-based
> > -00000000-0000-6000-8000-000000000000  DCE       time-v6    60038-03-11 05:36:10,955161+00:00
> > +00000000-0000-6000-8000-000000000000  DCE       time-v6    1970-01-01 00:00:00,000000+00:00
>
> If it is an error, the output should be empty.
>
> >  00000000-0000-0000-d000-000000000000  Microsoft
> >  00000000-0000-1000-d000-000000000000  Microsoft
> >  00000000-0000-2000-d000-000000000000  Microsoft
> > --
> > 2.47.3