Feb 23, 2007
ds: daylight saving time ... and the impatient user
a talented ad guru brought this up to my attention. i thought it was something strange and important enough for everyone (the three of you that may actually read my blog) ... you may be aware of this but dst doesn't affect kerberos at all since kerberos only uses utc. there is still potential for problems, however. if a user moves their clock forward (or backward) instead of letting the dst rules adjust it, then they'll run into kerberos failures in the form of krb_err_time_skew. anything beyond a 5 minute skew is determined to be a replay attack... and subsequently not honored. so with that in mind, you think... domain-joined resources will reset their times to the domain time. unfortunately, this only occurs in 8 hour intervals. of course, if the user just manages to change their time zone, this will not cause the same effect. they'll be fine. the time zone is a local offset which does not affect the utc value like utilizing the date/time applet to change the time forward/backward. hope this helps!