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    SubjectRe: Capabilities
    On Thu, 10 Feb 2000, Peter Benie wrote:

    > > If a process has its capabilities changed via sys_capset(), it is marked
    > > as capability aware. When a "capability aware" process does setuid(0 ->
    > > !=0), capabilities are not cleared. The "capability aware" flag is cleared
    > > on exec().

    > in that the side-effect of sys_capset is extremely non-obvious; I'd
    > probably be happier making the state change explicit with prctl().

    FW(L)IW, so would I.

    > Capabilities don't solve the inability to change which port is bound
    > since cap_net_bind_service is equivalent to root on most machines.

    Please explain? If bind has only CNBS and runs as user "named",
    then there is no root equivalence that I can see.

    > 1) Permitted capability set for setuid programs
    >
    > I want setuid root programs not to have all capabilites. cap_bound is
    > not the answer since I still want some programs that are started from
    > the system initialisation scripts to run with all capabilities.

    Mmm.. I'd like that too.

    > 2) Inherited capability set for setuid programs
    >
    > It is possible to run a non-capability-aware setuid-root program from
    > an environment that has cap_setuid-i. This prevents the program from
    > using setuid() to demote privilege back to a non-zero uid (unless that
    > uid was the real, effective or saved uid). This is a security risk
    > since the program might retain the ability to write to any file on the
    > system owned by root. When doing setuid root emulation, the inherited
    > rights mask should not be honoured.

    The whole lot, or merely CAP_SETUID?

    I see no reason that these two shouldn't be sysctls. Want
    a patch?

    Matthew.


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