Re: [PATCH] BSD Secure Levels LSM

From: Chris Wright (chrisw@private)
Date: Mon Dec 01 2003 - 11:41:44 PST

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    * Serge E. Hallyn (hallyn@private) wrote:
    > > > to implement some of the Secure Levels policies.  Note that a settime
    > > > hook currently exists in the LSM BK tree.  It is not, however, in the
    > > 
    > > Yes, it's in the LSM BK tree, and it's done slightly differently.  The
    > > warp_clock() bit is not done until after it's passed the hook in the BK
    > > tree.
    > 
    > That seemed counter-productive.  Do we really want to have to privately
    > mimick that functionality?
    
    No, but warp_clock() will change the time, so it would be a bad
    side-effect for a module to recreate.  It's only called, typically,
    during boot when setting the timezone.  Since it changes time, it should
    be done after the hook.
    
    > > The reason all three of these hooks were rejected is because they are
    > > too redundant with the existing capability check.  In these cases, the
    > > right thing to do is to collapse the capability check into the hook.  So
    > > this means, the security_module_delete() hook implementation in the
    > > capability code would be a simple cap_capable(current, CAP_SYS_MODULE)
    > > or smth. like that.
    > 
    > Rats.  On the whole, forcing modules to treat module load the same as
    > module unload seems like a terrible idea.  Well, hopefully there'll be
    > more justification for reintroducing the security_module hooks soon...
    
    Yes, it's a bit coarse grained, however seems it is sufficient for this
    module's needs.  The alternative is to collapse the capable() check into
    a new hook.
    
    > As for the settime hook, securelevel only refuses decrement of the
    > system clock.  That can't be mimicked with the capability hooks, can
    > it?  It would have to refuse all CAP_SYS_TIME calls.
    
    Yes, the hook is required.
    
    thanks,
    -chris
    -- 
    Linux Security Modules     http://lsm.immunix.org     http://lsm.bkbits.net
    



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