hi, i have been doing reading on NIS and NFS(central-user-accounts).
i noticed what appears to be a gaping problem.
i am hardly a unix network admin, this is all fairly new to me.
an example scenario:
a server is running NIS with it's /home dir shared over NFS to be automounted by all client machines so it can 'replace' the client's /home.
each user in the server's /etc/passwd file has a home directory in the server's NFS-shared /home dir, with permissions of each dir set up accordingly.
say, on the server, user bob has a UID of 501.
now, what if somebody brings another machine into the network(a laptop, maybe), and creates a LOCAL user account with a UID of 501. they then connect to the network, and mount the /home share.
logged in as the new user account, they would be able to access bob's files, because the exported filesystem still works on UIDs for determining file/folder access rights, and the new account shares bob's UID.
also, it's pretty easy to get a server to spit out bob's UID:
it seems like a hell of a lot of control is being given to the client machines here.
is this a real vulnerability, or am I missing something?
Lee.
