Re: uid change in sock_alloc breaks identd

Miquel van Smoorenburg (miquels@cistron.nl)
Tue, 21 Sep 1999 23:00:06 +0200

According to Alan Cox:
> > - inode->i_uid = current->uid;
> > - inode->i_gid = current->gid;
> > + inode->i_uid = current->fsuid;
> > + inode->i_gid = current->fsgid;
> >
> > Now in the case of a setuid client like rlogin, the real uid is ther user
>
> Well your rlogin should have dropped back to the real user except for
> the call to bind() 8).

Well the problem is that rlogin and rsh call the library function
rcmd(). That function _has_ to be called with euid == 0.

The above change in 2.2.7 simply broke GNU libc. All versions ..
For apparently no reason (AFAICS, IMHO etc)

> The above also fixes well designed apps where if you
> ran them under su you got a wrong report 8)

I don't understand, whatever you run under su runs with
uid == suid == euid == fsuid, right ?

Anyway, a Linux-specific fix in rlogin and rsh is possible by doing

setfsuid(getuid());
.. rcmd() ..
setfsuid(geteuid());

That will work under all kernels, and will not break stuff
when the rcmd() function in glibc is fixed (or the kernel.....)

So Herbert, please fix rlogin and rsh :]

Mike.

-- 
... somehow I have a feeling the hurting hasn't even begun yet
	-- Bill, "The Terrible Thunderlizards"


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