Re: kernel module loading vs securelevel

[jnemeth%victoria.tc.ca@localhost (John Nemeth)]

On Jan 31,  5:14pm, Paul Goyette wrote:
} On Sat, 16 Oct 2010, Izumi Tsutsui wrote:
} 
} >>> Hmm, what do you think about this feature?
} >>> Only available in INSECURE environment?
} >
} >> We trust modules at the time when they're installed into the trusted
} >> place, same as kernel itself.  I think prohibiting module load  at
} >> run-time is rather pointless.
} >
} > Well I think the point is whether we should require INSECURE or not
} > to use module autoload/autounload after multiuser.
} >
} > If we should I'll enable options INSECURE by default on ports
} > that require options MODULAR (to save kernel file size).
} 
} autoload/autounload does NOT perform any authorization checks - please 
} look at the code!  No checking of securelevel occurs, as far as I can 

     I just did and autoload most certainly does do authorization
checks.

} see.  For autoload, the module name must not contain a '/', so if the 
} module is being loaded from the file system it must be loaded from the 
} "blessed" /stand/${ARCH}/${VERSION}/modules directory.  Including the 
} INSECURE option will have no effect on autoloading of modules.
} 
} Manual loading and unloading of modules does involve calls to 
} kauth_authorize_system() which will check securelevel.

     sys/kern/kern_module.c:module_autoload() makes almost the exact
same call to kauth_authorize_system as does module_load().  The
difference is that the second last parm is (void *)(uintptr_t)1.  What
difference this makes is going to be buried in the bowels of kauth, and
I'm not going to dig through that at this moment.

}-- End of excerpt from Paul Goyette