Re: [Expectperl-discuss] ssh works from console but not once daemonized

[Chris M. <mut...@mc...>]

Hi,

I am running;
Perl 5.8
Expect 1.15
IO::Tty 1.02
IO::Stty .02
Linux 2.2.20

I am not sure how cron figures into this, I am not using it for this=
 script.

As I mentioned in my original post, I had kind of thought that the problem=
 was that
ssh was not working properly with expect/my script once daemonized.

Am I correct in guessing that ssh opening /dev/tty to read the password=
 because that
is more secure than simply reading stdin?  If this is the case, I might be=
 able to simply
modify ssh to just read from stdin.

What do you think?

Thanks,
Chris Muth

On 9/16/03 at 3:53 PM Roland Giersig wrote:

>What system are you running on? You ARE using the latest version of 
>IO::Tty, I suppose...
>
>The problem is: ssh is opening /dev/tty to read the password. If the 
>script is started in a terminal session, /dev/tty is defined and Expect 
>will redirect it for the spawned program to the pty, so the password 
>prompt is seen.
>
>When the script is started via cron, there is no controlling terminal 
>and obviously Expect cannot take control of it (it would have to create 
>it), so ssh cannot get the password and thus fails.
>
>Even though I've had my share at kernel hacking, I do not know how to 
>resolve this, especially given that this is probably highly 
>system-dependend...
>
>Workaround: set up public key authentication for ssh, so ssh doesn't ask 
>for a password.  But then you'd probably won't need Expect at all...
>
>Hope this helps,
>
>Roland
>
>Chris Muth wrote:
>
>> Hi,
>> 
>> I am working on a script that daemonizes and then uses
>> ssh to login/operate/logout of a remote machine.
>> 
>> The code works perfectly when it is not demonized, (with the=
 demonization
>> code commented out).  The script will run and partially work if the
>> code (the lines indicated below) is left in,-- it will fork, detach, and
>> sleep but fail to get the command prompt on the remote machine.
>> I have it log to a file (LOG_FILE), because when it is daemonized I
>cannot
>> see the output.
>> 
>> The only thing I can think of is that ssh must do something to the
>> terminal/console that works
>> when I run it manually on the console, but when the program
>> is daemonized, ssh cannot do whatever it is trying to do and fails.
>> 
>> The segment below fails saying "never got command prompt".  This means
>that
>> it got the password prompt from the remote machine
>> and sent the password, but never got the command prompt after that.
>> 
>> I don't think this is an expect problem, I think that it is a problem
>with
>> how ssh and expect work together.
>> My guess is that ssh is not intentionally failing, but it is trying to=
 do
>> something that does not work with the terminal that expect uses.
>> 
>> I have even tried "ssh -l root" to specify the username, "ssh -T" so ssh
>> won't allocate a pseudo-tty, and not setting the pty to raw; all to no
>> avail.
>> 
>> Does anyone have any ideas?
>> Below is the code segment.
>> 
>> Thanks,
>> -Chris Muth
>> 
>> 
>> #!/usr/bin/perl5.8 -w
>> 
>> #prompt user for host to login to, and password
>> print"host: ";$host=3D<STDIN>;chomp$host;
>> print"pass: ";$pass=3D<STDIN>;chomp$pass;
>> 
>> use Expect;
>> use POSIX;
>> 
>> #  Comment out daemonizing code starting here
>> #######################################
>> $pid =3D fork();
>> exit 0 if ($pid);
>> 
>> POSIX::setsid();
>> close STDIN;
>> close STDOUT;
>> close STDERR;
>> 
>> sleep 5;
>> #######################################
>> # comment out daemonizing code ending here
>> 
>> open (LOG_FILE, "> output"); # open log file
>> 
>> $exp =3D new Expect;
>> $exp->raw_pty(1);
>> 
>> # login to the remote host
>> #$exp->spawn("/usr/local/bin/ssh",'-T',"$host");  # Even tried ssh -T
>> $exp->spawn("/usr/local/bin/ssh","$host");
>> 
>> # wait for Password: prompt
>> $retval =3D $exp->expect(30,'-re','word:\s$');
>> if (!defined $retval){
>>    print LOG_FILE "Never got password prompt\n"; flush LOG_FILE;
>> } else {
>>    $exp->send("$pass\n");
>>    #($retval,undef,$retstr,undef,undef) =3D $exp->expect(30,'stdin: is=
 not
>a tty'); # for ssh -T
>>    ($retval,undef,$retstr,undef,undef) =3D $exp->expect(30,'# ');
>> 
>>    # do something on the remote machine, test results
>>    if (!defined $retval){
>>       print LOG_FILE "Never got command prompt\n"; flush LOG_FILE;
>>    } else {
>>       print LOG_FILE "\"$retstr\"\n"; flush LOG_FILE;
>>       $exp->send("echo Hello World\n");
>>       $exp->expect(5,'This will make expect sleep for 5 seconds');
>>       $exp->send("logout\n");
>>       print LOG_FILE "It worked\n"; flush LOG_FILE;
>>    }
>> }
>> $exp->hard_close();
>> print LOG_FILE "\n"; flush LOG_FILE;
>> close LOG_FILE;
>> exit 0;
>> 
>> 
>> 
>> 
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