Year 2038 considerations for uses of krb5_timestamp

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POSIX time values, which measure the number of seconds since January 1

1970, will exceed the maximum value representable in a signed 32-bit

integer in January 2038.  This documentation describes considerations

for consumers of the MIT krb5 libraries.

Applications or libraries which use libkrb5 and consume the timestamps

included in credentials or other structures make use of the

:c:type:`krb5_timestamp` type.  For historical reasons, krb5_timestamp

is a signed 32-bit integer, even on platforms where a larger type is

natively used to represent time values.  To behave properly for time

values after January 2038, calling code should cast krb5_timestamp

values to uint32_t, and then to time_t::

    (time_t)(uint32_t)timestamp

Used in this way, krb5_timestamp values can represent time values up

until February 2106, provided that the platform uses a 64-bit or

larger time_t type.  This usage will also remain safe if a later

version of MIT krb5 changes krb5_timestamp to an unsigned 32-bit

integer.

The GSSAPI only uses representations of time intervals, not absolute

times.  Callers of the GSSAPI should require no changes to behave

correctly after January 2038, provided that they use MIT krb5 release

1.16 or later.