Remote command execution using perl client-server (socket) - perl

Question

My client.pl
#!/usr/bin/perl
use IO::Socket::INET;
use strict;
my $name = '172.20.10.189'; #Server IP
my $port = '7890';
my $socket = IO::Socket::INET->new('PeerAddr' => $name,
'PeerPort' => $port,
'Proto' => 'tcp') or die "Can't create socket ($!)\n";
print "Client sending\n";
while (1) {
my $msg = <STDIN>;
print $socket $msg;
print scalar <$socket>;
}
close $socket
or die "Can't close socket ($!)\n";
My server.pl
#!/usr/bin/perl
use IO::Socket::INET;
use strict;
my $port = "7890";
my $socket = IO::Socket::INET->new('LocalPort' => $port,
'Proto' => 'tcp',
'Listen' => SOMAXCONN)
or die "Can't create socket ($!)\n";
while (my $client = $socket->accept) {
my $name = gethostbyaddr($client->peeraddr, AF_INET);
my $port = $client->peerport;
while (<$client>) {
print "[$name $port] $_";
my #out = `$_`;
print #out;
print $client "$.: #out";
}
close $client
or die "Can't close ($!)\n";
}
die "Can't accept socket ($!)\n";
My client is sending a command (ls -lrt /) to the server and Server is supposed to run that command and send output to the client back.
Problem:-
The command is executed successfully on the server but it sends only first line to the client. If I press any key from client again the next line of output is sent to the client.
Or tell me how to send multiple line output to back to client.
Any help would be appreciated.
Thanks
Abhishek

Answer 1

The Server sends all lines to the client, the client however chooses to read only one line:
print scalar <$socket>;
If you remove the scalar, it should work. However, your architecture is still a security nightmare.
All servers should run in taint mode (-T switch).
Never blindly execute commands that a clients sends you. Only execute commands that pass a very strict validation test, do not run commands that just don't look malicious.
Perhaps you are trying to duplicate SSH, you might want to look at that program instead.
Your server doesn't do any kind of authentication. At least it logs all inputs.

Answer 2

It was a silly mistake... and I have fixed the first issue as follows and got multi-line output on the client side...
Client.pl
#!/usr/bin/perl
use IO::Socket::INET;
use strict;
my $name = '172.20.10.189'; #Server IP
my $port = '7890';
my $socket = IO::Socket::INET->new('PeerAddr' => $name,
'PeerPort' => $port,
'Proto' => 'tcp')
or die "Can't create socket ($!)\n";
print "Client sending\n";
while (1) {
my $msg = <STDIN>;
print $socket $msg;
while (<$socket>)
{
print "\n$_";
}
}
close $socket
or die "Can't close socket ($!)\n";
BUT there is one more issue -
I want my client to keep sending few other commands one after another until I close the client manually and receive output.
The problem is - It receives output of the first command only..
Can anyone now help me on this?