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Aucbvax.2880 fa.unix-wizards utzoo!decvax!ucbvax!unix-wizards Mon Aug 31 22:18:29 1981 setuid not working if user is root >From Wales@UCLA-SECURITY Mon Aug 31 22:12:44 1981 We took the "ignore setuid if root" code out of our 4bsd system on our VAX 11/780 with no ill effects. After doing an inventory of all system programs which used setuid, and discovering that (at least here) the only ones which were not owned by root were the UUCP programs, we concluded that no lossage would result by making root honor setuid.

I was trying to close up some of the security holes in UUCP file transfer and UUX command execution, you see, and it soon became evident that the proper solution was to make setuid work even when root was doing the executing.

I don't claim to know why this code was put into UNIX, but the best guess I can hazard is something to the effect that setuid programs are supposed to give someone additional privileges he didn't already have (such as accessing normally protected data or issuing privileged system calls in a controlled environment), and the superuser already has all the privileges in the world, so there's (supposedly) no reason you would ever need to setuid to someone else if you were the superuser. (Remember that almost all setuid programs setuid to root anyway!) Clearly, no one had UUCP in mind when UNIX was first written.

I vote to declare the test in question a bug -- or, if that's too harsh for some, a misguided misfeature -- and take it out.

-- Rich Wales -------

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