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diff --git a/doc/appdev/y2038.rst b/doc/appdev/y2038.rst new file mode 100644 index 000000000000..bc4122dad0a4 --- /dev/null +++ b/doc/appdev/y2038.rst @@ -0,0 +1,28 @@ +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 +: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. |