my network because setnetgrent() was trying to do a lookup on group "".
It seems that an attempt to do a yp_match() (and possible yp_next())
on a null or empty key causes Sun's ypserv in SunOS 4.1.3 to exit
suddenly (and without warning). Our ypserv behaves badly in this
situation too, thoush it doesn't appear to crash. In any event, getpwent,
getnetgrent and yp_match() and yp_next() are now extra careful not to
accidentally pass on null or empty arguments.
Also made a small change to getpwent.c to allow +::::::::: wildcarding,
which I had disabled previously.
- Have the +@netgroup/-@netgroup caches handle the +user/-user cases too.
- Clean up getpwent() to take advantage of the improved +user/-user handling.
as an NIS client. The pw_breakout_yp routines that are used to populate the
_pw_passwd structire only do anything if the bits in the pw_fields member
_pw_passwd are cleared. Unfortunately, we can get into a state where
pw_fields has garbage in it right before the YP lookup functions are
called, which causes the breakout functions to screw up in a big way.
Here's how to duplicate the problem:
- Configure FreeBSD as an NIS client
- Log in as a user who's password database records reside only in
the NIS passwd maps.
- Type ps -aux
Result: your processes appear to be owned by 'root' or 'deamon.'
/bin/ls can exhibit the same problem.
The reason this happens:
- When ps(1) needs to match a username to a UID, it calls getpwuid().
- root is in the local password file, so getpwuid() calls __hashpw()
and __hashpw() populates the _pw_passwd struct, including the pw_fields
member. This happens before NIS lookups take place because, by coincidence,
ps(1) tends to display processes owned by root before it happens upon
a proccess owned by you.
- When your UID comes up, __hashpw() fails to find your entry in the
local password database, so it bails out, BUT THE BITS IN THE pw_fields
STRUCTURE OF _pw_passwd ARE NEVER CLEARED AND STILL CONTAIN INFORMATION
FROM THE PREVIOUS CALL TO __hash_pw()!!
- If we have NIS enabled, the NIS lookup functions are called.
- The pw_breakout_yp routines see that the pw_fields bits are set and
decline to place the data retrieved from the NIS passwd maps into the
_pw_passwd structure.
- getpwuid() returns the results of the last __hashpw() lookup instead
of the valid NIS data.
- Hijinxs ensue when user_from_uid() caches this bogus information and
starts handing out the wrong usernames.
AAAARRRRRRRRRGGGGGGHHHHHHHHHH!!!
*Please* don't tell me I'm the only person to have noticed this.
Fixed by having __hashpw() check the state of pw_fields just before
bailing out on a failed lookup and clearing away any leftover garbage.
What a fun way to spend an afternoon.
- FreeBSD's NIS server can supply a master.passwd map, which has
more fields in it than a standard passwd map, so we need a
_master_pw_breakout() fuction.
- When doing passwd map lookups, look for master.passwd.* by attempting
a _yp_first() on master.passwd.byname. If it exists, we're being served
by a FreeBSD NIS server and we should use this map.
- If we aren't the superuser, retrieve only the standard passwd maps.
If we're being served by a FreeBSD system, then the passwd map has
no passwords in it, and it won't serve us the master.passwd map unless
we're superuser anyway.
There's a small speed hit for the superuser inherent in the check for
the master.passwd map, but this lets us dynamically decide what to do
rather than rely on a non-standard config file somewhere. Since all
of this is bypassed for normal users, they shouldn't notice the
difference.
YP by disallowing `+' entries as logins in all cases. (This handles the
case of a `+' entry in the password file but YP not running, which should
never happen but is easy enough to check for so we'll apply some
prophylaxis.)
