Possible bug in NFSv4 with krb5p security?

[Rick Macklem]

Elias Martenson wrote:
> On 17 February 2013 22:58, Rick Macklem <rmacklem at uoguelph.ca> wrote:
> 
> I think the Makefiles are in the kerberos5 directory.
> >
> > Since the only function you care about is the one in
> > kerberos5/lib/libgssapi_krb5/pname_to_uid.c, I'd
> > just put a copy of that file in usr.sbin/gssd and
> > modify the Makefile there to compile it and link
> > its .o into gssd, avoiding rebuilding any libraries.
> >
> > I'd put a couple of fprintf(stderr, ...) in it and
> > then run "gssd -d" and see what it says.
> >
> > Just how I'd attack it, rick
> 
> 
> Good news! The problem is solved!
> 
> You were right, the problem was in pname_to_uid.c. In it, the
> following
> code can be found:
> 
> char lname[MAXLOGNAME + 1], buf[1024];
> 
> /* some code snipped for brevity... */
> 
> getpwnam_r(lname, &pwd, buf, sizeof(buf), &pw);
> if (pw) {
> *uidp = pw->pw_uid;
> return (GSS_S_COMPLETE);
> } else {
> return (GSS_S_FAILURE);
> }
> 
> As it turns out, the getpwnam_r() call fails with ERANGE (I had to
> check
> the return value from getpwnam_r() in order to determine this, as pw
> is set
> to NULL both if there was an error or if the user name can't be
> found).
> 
> Now, increasing the size of buf to 1024 solved the problem, and now
> the
> lookup works correctly.
> 
> I wrote a small test program that issued the same call to getpwnam_r()
> and
> it worked. Until I su'ed to root, and then it failed.
> 
> It seems as though the buffer needs to be bigger if you're root. I
> have no
> idea why, but there you have it. Problem solved.
> 
> Should this be fixed in the main codebase?
> 
Yes, I would definitely say so.

I won't be able to do a commit until April, but meybe someone else
can do a commit sooner?

> Oh, and thanks so much to all of you for being patient with me while
> solving this. I really appreciate it. Also, I'd like to say that the
> code
> base was quite pleasant to work with. Thanks for that too. :-)
> 
And thanks for working through this, so we now have a fix, rick

> Regards,
> Elias
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