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    SubjectRe: varlinks! ((in)security?)
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    Illuminatus Primus wrote:
    >
    >
    > On Wed, 29 Apr 1998, Rogier Wolff wrote:
    >
    > >
    > > > No, no, no... you could potentially trick an app into indirecting
    > > > though a symlink it otherwise wouldn't have indirected through,
    > > > getting unauthorized access to a file.
    > >
    > > So, I still don't get it. Explain please....
    > >
    >
    > I don't think the security concerns with varlinks are any different from
    > dealing with symlink races. If a program doesn't trust a symlink (or
    > varlink) to remain constant, it should fopen() the file and then fstat()
    > it, or whatever it likes once it has the file referenced by inode.
    > Varlinks could only make changing the link destination something triggered
    > internally instead of a crap shoot.. But I'm guessing that most programs
    > don't modify varlink-dependant variables in between access checks and
    > actual access. If so, they were doing things insecurely anyway :).
    >
    > Separate subject (TMPDIR):
    > How would TMPDIR interact with suid programs? It seems like being able to
    > make a suid program write it's temp files to a directory you have complete
    > access to (as opposed to sticky access) wouldn't be a Good Thing.

    The answer is simple. A setuid program should simply take care not to write
    anything to /tmp or to $TMPDIR. Both are terribly wrong.

    I've suggested "/etc/tmp" as a root-only tmpdir. Or /stmp (analogous to
    /sbin).

    I'm hoping varlinks will "solve" this. But I'm biased. Shoot ahead.


    Roger.


    --
    If it's there and you can see it, it's REAL |___R.E.Wolff@BitWizard.nl |
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    If it's not there and you can see it, it's VIRTUAL |__FAX:_+31-15-2138217 |
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