How to set time.

[Scott Bennett]

     On Wed, 22 Jul 2009 22:41:14 -0700 Kyle Williams <kyle.kwilliams at gmail.com>
wrote: 
>Your Tor client will tell you that you have a time set that is too far off
>what it should be.  It will report this in minutes.Read that line and adjust
>your time by X minutes.

     For someone wishing to make a portable image for use on a USB flash
device or even a CD and designed to be as simple to use as possible, it
would be a useful feature for a *client* to be able to get a current time
and date from one of its chosen entry guards (or perhaps a choice from
among the responses from all entry guards selected (default of 3).  (This
would, of course, require that entry guards be used, but that is currently
the default option anyway.)  Relays currently need to have correct (or
nearly correct) system clocks anyway, and as the nearest nodes to the client,
they would be the obvious candidates for the clients to ask.
     A problem may result if the client, having gotten a current time and
date from a tor entry node, tries to set the system time and date a) using
an inappropriate method for the combination of user id and operating system
or b) coding errors in a valid method, either of which would obviously
detract from simplicity and ease of use. :-)
     On systems that distinguish clearly among userids (ahem) and especially
ones where different userids have different security privileges, tor normally
changes its userid to something specific to tor during initialization,
usually as soon as any privileged operations have completed and before any
ordinary tor operations have begun.  An attempt to set the system time and
date on a system that associates privileges with userids may fail if it takes
place after tor has relinquished extra privileges.  An  hypothetical
alternative method would involve tor keeping its own clock to use in the
form of an offset from the system clock, but such an approach may well be
impractical.


                                  Scott Bennett, Comm. ASMELG, CFIAG
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