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    SubjectRe: [PATCH 2/3] Security: Implement disablenetwork semantics. (v4)
    On Sun, 10 Jan 2010, Michael Stone wrote:

    >
    > Pavel's position is that disablenetwork is likely to permit some attacker
    > somewhere to deny network access to some setuid app some day in a way that
    > violates some security policy.
    >
    > He has mentioned specific concern over scenarios like:
    >
    > Alice configures PAM auth to 'fail open' by checking login credentials
    > against a restrictive LDAP server and, if the server is unavailable, against
    > a very permissive files database.
    >
    > Alice updates her kernel to a version with disablenetwork.
    >
    > Mallory calls disablenetwork, calls su -, and vanquishes all.
    >
    > My position is that better isolation facilities like disablenetwork will
    > prevent far more grievous security faults than they (theoretically) cause.
    >
    > What is your perspective on the matter?

    Unexpected failure modes for privileged apps using security interfaces has
    already proven to be a problem (e.g. the sendmail capabilities bug), so it
    seems prudent to try and mitigate that as well. I don't think we need to
    look at this as an either-or situation -- it seems we can do both, and get
    something useful in its own right from the mitigation.


    --
    James Morris
    <jmorris@namei.org>


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