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List:       busybox
Subject:    Re: cp bug?
From:       Denys Vlasenko <vda.linux () googlemail ! com>
Date:       2008-03-30 22:32:43
Message-ID: 200803310032.43488.vda.linux () googlemail ! com
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On Monday 31 March 2008 00:17, Bernd Petrovitsch wrote:
> > > > What will happen if user created malicious symlink
> > > > /home/user/somefile -> /dev/sda? Should cp STILL write to
> > > > symlink's target despite it being dangerous?
> > > 
> > > Not necessarily - it could point to some harmless file (still being
> > > owned by that user).
> > > 
> > > Why not "rm /home/user/somefile" before he "cp" if one absolutely cares?
> > 
> > People who insist on "cp file /dev/something" acting as
> > "cat file >/dev/something" will scream murder and will hunt you,
> 
> Sorry, I'm not sure I understand (as my question cou^Wshould have been
> better formulated).
> 
> > and unfortunately they will have big heavy books with "POSIX"
> > on them as weapons. Lost fight.
> 
> Just to make sure we speak of the same (and trying to improve the
> question):
> *If* one fears that sym-link problem of above, he/she can `rm` the
> target (possibly only if it is a sym-link) explicitly before and call
> then `cp` (or `cat >`).

Yes, this is a prudent thing to do. I just feel that it is sort of
strange that such a basic and essential utility as cp requires users
to know and remember these subtle security implications.
--
vda

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