Year 2038 considerations for uses of krb5_timestamp

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 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.