Cron
From UGCS
(Difference between revisions)
| Line 13: | Line 13: | ||
* If the user's job takes more than the time before it would get run again, kill it | * If the user's job takes more than the time before it would get run again, kill it | ||
* Send the output to the user | * Send the output to the user | ||
| + | |||
| + | ==Security== | ||
| + | * User security is maintained because a new keytab is generated each time. This prevents an old keytab from being stolen and re-used. | ||
| + | * The remctl script has a number of security checks to prevent unauthorized users from using it. | ||
| + | * If a shellserver gets rooted, then they will be able to steal the user/cron keytab and modify a user's files. This could be mitigated by running cron jobs only on non-login machines... which defeats the point of this system to some extent. | ||
[[Category:Sysadmin_Documentation]] | [[Category:Sysadmin_Documentation]] | ||
Revision as of 07:35, 19 January 2010
Getting cron services available to users is a work in progress. Presently, cron is being architected with a central server that calls a Remctl script on shellservers which takes care of running the user's cron program.
Daemon
- Figures out which jobs need to be run
- Gets a new keytab for username/cron
- Sends the job id as well as keytab to a remctl script via command-line arguments
Client-side portion
- Figure out which user we are trying to be and which job we are running
- Change to that user's home dir and UID/GID
- Create a tempfile with the keytab we were given and get kerberos stuff for it
- Run the user's job
- If the user's job takes more than the time before it would get run again, kill it
- Send the output to the user
Security
- User security is maintained because a new keytab is generated each time. This prevents an old keytab from being stolen and re-used.
- The remctl script has a number of security checks to prevent unauthorized users from using it.
- If a shellserver gets rooted, then they will be able to steal the user/cron keytab and modify a user's files. This could be mitigated by running cron jobs only on non-login machines... which defeats the point of this system to some extent.
