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Aucbvax.5047 fa.unix-wizards utzoo!decvax!ucbvax!unix-wizards Mon Nov 9 22:32:08 1981 Group ID's and bit mask >From z@CCA-UNIX Mon Nov 9 21:54:33 1981

I was away for three weeks and am just catching up on my news, which is why this message is a little late.

I am an old Tenex veteran, and one of the first things I did a year and a half ago after bringing up 3BSD on our VAX was to make the groups feature more usable. Access is done on the basis of a bit mask, but using one which may span several words, so that the number of possible groups can be changed at compile time. We use 256 maximum, though this can be easily changed up or down. The bit mask allows each user to always have the permissions of all his groups simultaneously. Newly created files are created with the group of their parent directory. In addition, we have fixed "chgrp" so that the user may change the group of any of his files to any other group of which he is a member. This does not seem to be an additional security problem, since he could always do this in a roundabout way anyway. Mkdir was also changed slightly so that new directories are created with the group of their parent.

This scheme has worked very well for us. Although it is implemented for 4BSD, the changes to the kernel are quite small and fairly trivial, and I'm sure it would work with little or no modification for V6 and V7. I also understand that Berkeley plans to implement either this scheme or something very close to it in their next release. I have a short memo prepared on how to imlement this change; if you are interested in it, I'd be happy to send you an (electronic) copy. I can be reached either as z@cca-unix or decvax!cca!z.

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