Cuserid() is a security hole

[Karel van Houten]

In article <4563 at cheviot.newcastle.ac.uk>  writes:
>
>Can  anyone  see  anything  wrong  with  adding something like this to
>getlogin(), to avoid confusion?
>
>        stat( ttyslot_result, statbuf);
>        if (statbuf.st_uid != getuid())
>                return(0);

Sometimes you want to know the login name, even if someone has su-ed to
someonme else.

I have written my own getlogin(), that tries to find a tty on
fd 0, 1, or 2, but ALSO checks that the process has READ permission on that
file descriptor. Getty insures that a tty is in mode 622, so you can
not fake your login name by redirecting input from someone else's tty.


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