Bug in 4.2BSD su

[Steve Lademann]

I posted this once, but I don't think it made it - Try again.

>You probably know all about this one, but here goes, anyway.
>
>There is a bug in VAX 4.2BSD su which occurs if you want to temporarily
>change to a different login using the following shell command:-
>
>		su fred
>
>If the new user doesn't have access to the current directory, su
>appears to exit silently without changing to the new user. If the shell
>prompts for the new and the old user are similar, it's extremely
>difficult to tell what has happened. The reason is that su does not
>check that the current directory is accessible prior to exec-ing the
>new shell, which, on on being exec-ed and finding that it can't read
>the directory, exits ever so quietly with a status of 1. (Or at least,
>csh does - I haven't tried sh.)
>
>The fix is to add a check just prior to shell execing to test
>accessibility of the current directory, having juggled the uid and gid
>set. If it isn't, the friendly thing to do is to shift to the new
>user's home directory. If you're unfriendly, snap his head off and exit.
>
>If this is of a problem to you, please mail me for a diff.
>
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|Steve Lademann		|Phone:	44 727 59292 x326		|
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