tim.culhane has asked for the wisdom of the Perl Monks concerning the following question:

hi, I'm trying to use Net::OpenSSH to su to another user account, issue a command and capture the output of that command in my perl script. I need to use sudo for the su command in order to get permission to switch users. The code I have right now is: 


#!/usr/bin/perl

use Net::OpenSSH;

my $host = "enfcdb01";
my $user = "loguser";
my $password = "cIhyv46iPL8092t";


##-- set up a new connection
my $ssh = Net::OpenSSH->new($host, user => "loguser");

  $ssh->error and die "Couldn't establish SSH connection: ". $ssh->err
+or;

  my @ls = $ssh->capture("ls");
  $ssh->error and
    die "remote ls command failed: " . $ssh->error;

print @ls;

  my @out = $ssh->capture({tty => 1, stdin_data => "$password\n"},
                          'sudo', '-Sk',
'-p', '',
                          '--',
                          'su - imail; ls');


print "the value of out is \n";
print "$out[0]";

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and the output I get is:

loguser@enflog01 check_apps$ ./check_mx_app.pl id_rsa.pub muxserver_accept_control: tcgetattr: Invalid argument tcgetattr: Invalid argument the value of out is

Anybody know what is wrong with my capture call? Thanks, Tim

Replies are listed 'Best First'.
Re: Problem using Net::OpenSSH->capture to su to another user
by salva (Canon) on May 30, 2014 at 06:37 UTC
    su doesn't change the UID of the current shell but creates a new one.

    Try as follows: 

    my @out = $ssh->capture({ stdin_data => "$password\n" },
                         'sudo', '-Sk',
                         '-p', '',
                         '--',
                         'su -c "ls" imail');

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      Hi Salva,

      Thanks for your response.

      Unfortunately when I try your code I get:

      sudo: sorry, you must have a tty to run sudo

      When I add:

      tty => 1,

      I get my original error back again:

      muxserver_accept_control: tcgetattr: Invalid argument tcgetattr: Invalid argument

      If I ssh to the remote server and manually issue some 'sudo su' commands I get output like the below:

      loguser@enfcdb01 ~$ sudo su imail We trust you have received the usual lecture from the local System Administrator. It usually boils down to these three things: #1) Respect the privacy of others. #2) Think before you type. #3) With great power comes great responsibility. sudo password for loguser: imail@enfcdb01 loguser$

      So this works and I'm now able to operate as the imail user.

      Using the '-c' option to su I get:

      loguser@enfcdb01 ~$ sudo su -c "ls" imail ls: cannot open directory .: Permission denied

      Trying the same using the 'pwd' command:

      loguser@enfcdb01 ~$ sudo su -c "pwd" imail /home/loguser

      This seems to just report the current working directory of the loguser user, i.e. it has not changed to the imail home directory (which is perhaps expected with the '-c' option to su?)

      Any additional ideas on how I can get this to work?

      Thanks,

      Tim

[reply]
        Any additional ideas on how I can get this to work?

        You could try using in conjuction with Expect; 

        #!/usr/bin/perl
use strict;
use warnings;
use Net::OpenSSH;
use Expect;

select STDOUT; $| = 1;
select STDERR; $| = 1;
my $timeout  = 5;
my $password = '';
my $user     = '';
my $host     = '';

my $ssh = Net::OpenSSH->new(host=>$host, 
                            user=>$user,
                        password=>$password);

my ($pty, $pid) = $ssh->open2pty("sudo -k; sudo su - imail -c ls")
    or die "open2pty failed: " . $ssh->error . "\n";

my $expect = Expect->init($pty);
$expect->raw_pty(1);
$expect->expect($timeout, ':')
    or die "expect failed\n";
$expect->send("$password\n");
$expect->expect($timeout, "\n")
    or die "bad password\n";

while(<$pty>) {
  print "$. $_"
}

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        poj
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        sudo: sorry, you must have a tty to run sudo

        You are using an old version of sudo. Update it if you can.

        I get my original error back again: 
        muxserver_accept_control: tcgetattr: Invalid argument tcgetattr: Inval
+id argument

        [download]

        This error is harmless, you can safely ignore it. Also, you can silence it adding the following option into the constructor call: master_stderr_discard => 1 

        sudo su -c "pwd" imail
/home/loguser

        [download]
        This seems to just report the current working directory of the loguser user

        Add the flag -l to the su command: sudo su -lc "pwd" imail

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