[Expectperl-discuss] using Expect.pm with su?

[Ed A. <er...@uc...>]

I'm looking for someone who knows the internals of Expect.pm well
enough to tell me if there is a mod I can make which will cause the
following program to work.  The environment is: solaris-9, Expect-1.15,
IO-Stty-.02, IO-Tty-1.02, perl-5.6.0.
 
The following program forks /bin/su and feeds it a password in the
hopes of getting a shell with the permissions of another user, in
this case user "test".  No, this isn't what I really want to do; the
application I need this for is a challenge-response thing.  I cut
the c-r code down to the simpler example below, which reproduces the
problem.

The problem is that the /bin/sh exec-ed by /bin/su dies almost
immediately, as evidenced by control exiting from interact() immediately.
I can see the '$ ' prompt from sh, but that's about it.  In the
debug output, I see an "Attempting interconnection" followed by
setting of tty modes on fd 4, and then an immediate close of fd 4 & 5.
I tried fooling around with IO::Stty to try to set the tty modes
back to cooked, but that didn't help.  Perhaps su does something
horrible with file descriptors?

The petulant code is:

#!/local/s/perl-5.6.0/bin/perl

 use Expect;
 use IO::Stty;

 $ENV{PATH} = "/bin";  $ENV{SHELL} = "/bin/sh";
 my $user = "test";
 my $passwd = "pop,eye";
 my $exp = new Expect();
#$exp->manual_stty(1);
#$ostty = IO::Stty::stty(\*STDIN,'-g');
 $exp->slave->clone_winsize_from(\*STDIN);
 $exp->log_stdout(0);
 $exp->exp_internal(0);
 $Expect::Debug = 1;
#$exp->raw_pty(1);		# don't go there
 $exp->spawn("/bin/su",$user);
 $expstr = "Password: ";
 $exp->expect(4,$expstr);
 $got = $exp->exp_match();  print "$expstr TILT!\n" if $got ne $expstr; 
 $exp->send("$passwd\n");
 $expstr = "\$ ";
 $exp->expect(4,$expstr);
 $got = $exp->exp_match();  print "$expstr TILT!\n" if $got ne $expstr;
 print "$expstr";		# print sh prompt and interact
 $exp->interact();