Re: A Comment from User Space

From: Seth Arnold (sarnoldat_private)
Date: Mon Apr 23 2001 - 20:07:30 PDT

  • Next message: Valdis.Kletnieksat_private: "Re: A Comment from User Space"

    * Valdis.Kletnieksat_private <Valdis.Kletnieksat_private> [010423 19:23]:
    > You've got it backwards.  We *know* that 'access()' is fundementally
    > screwed up.
    > 
    > BUT WHAT IF IT ACTUALLY WORKED?
    
    Errr.. I'll need a lot more convincing before I think an access()-like
    function is a workable security measure.
    
    My reasoning (while I make no claim of originality in this reasoning):
    Program P makes check on "if I executed sequence S in security domain D
    will it succeed?" at time t_0.
    Program P performs sequence S in its own (presumably elevated) security
    domain d at time t_1.
    
    Between t_0 and t_1, program Q could change the floor out from
    underneath P. When t_1 finally roles around, the security domain D
    *would prevent* the execution. But at t_0, the security domain D said it
    *would allow* the execution.
    
    I think the whole idea is fundamentally flawed. Forcing module guys to
    implement an access()-like function (whether for information purposes or
    for broken security checking) doesn't seem right.
    
    If you want to support it in your module, go right ahead. But I don't
    think it should be forced on anyone -- because it cannot promise to be
    correct except in situations where their correctness doesn't matter.
    (i.e., when no one is actively attacking the system.)
    
    If you can present a method for an access()-like system to work reliably
    in all cases, I am sure I am not the only one who would love to see it. :)
    
    Cheers!
    
    -- 
    Earthlink: The #1 provider of unsolicited bulk email to the Internet.
    
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