Re: [PATCH] settime hooks (1/1)

From: Valdis.Kletnieks@private
Date: Mon Aug 09 2004 - 18:37:12 PDT


On Mon, 09 Aug 2004 12:04:53 EDT, James Morris said:

> Is there a good paper describing the threat model for Secure Levels?  Or 
> can you explain why specifically decrementing the system time is something 
> you would want to stop root from doing?

Anybody who's had a cron job run twice at 2:30AM on a Daylight Savings change
day knows exactly why you want a monotonically increasing system clock. ;)

(Yes, the cron example is due to $TZ brain damage - but more generally, a backwards
step of the clock can potentially be exploited - Really Dumb Example:

1) log on at 03:01
2) Kick system time back to 16:59 the previous day
3) Run bogus copy of "must run inside 8-5" payroll job or similar time-locked app.
4) Kick system time back to 03:01

Ponder pam_time.so and pam_timestamp.so.... ;)






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