Re: Possible system call interface for LSM

From: jmjonesat_private
Date: Fri Aug 10 2001 - 18:15:48 PDT

  • Next message: jmjonesat_private: "Re: Possible system call interface for LSM"

    On 11 Aug 2001, David Wagner wrote:
    
    > Greg KH  wrote:
    > >Ah, but Stephans program should first validate that the kernel is
    > >running SELinux by some other method than the syscall [...]
    > 
    > Are there race conditions here?  What if someone does a
    > 'rmmod selinux; insmod subdomain' between the time when
    > you check for the presence of SELinux and use the syscall?
    > 
    > It might be that an advantage of having the invoker of the
    > syscall explicitly specify which module they expect to be
    > handling this is that it rules out attacks like this where
    > you might get unexpected (and hence undesired) behavior.
    > 
    
    Yes.  There are possible race conditions.  The application can check to
    see if the appropriate module is loaded and then assume that everafter.
    
    I don't think this is actually a PROBLEM though.  The module should verify
    that it is listening to the proper application, not the kernel, not the
    application. 
    
    Security, if any, resides in the module.
    
    THIS (module side verification) does not require a specific argument
    outside default channels to maintain, imho.
    
    As a vulnerabilty, it is an extreme long-shot proposition. :)
    J. Melvin Jones
    
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    ||  J. MELVIN JONES            jmjonesat_private 
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