Aloha monks! I was recently stuck with trying to solve a problem for a friend; he was using rsync, specifically, File::Rsync, to rsync files over to and from a remote host; however, he couldn't perform any authentication because he was not able to use the command line, due to some restriction. So I spoke with him and we came up with the idea that what he could do would be to simply just key the remote host with his public key, and this is the script I wrote to take care of that:

#!/usr/bin/env perl

use strict;
use warnings;
use Net::SSH::Perl;

my ($username, $hostname, $password) = @ARGV;
my $die = 0;
if(!defined $username) {
        print "It seems you forgot to provide a username.\n";
        $die = 1;
}
if(!defined $hostname) {
        print "It seems you forgot to provide a hostname.\n";
        $die= 1;
}
if(!defined $password) {
        print "It seems that you forgot to provide a password.\n";
        $die = 1;
}
if($die) {
        print "Usage: key <username> <hostname> <password>\n";
        exit;
}

my $filename;
if(-f $ENV{"HOME"}."/.ssh/id_rsa.pub") {
        $filename = "id_rsa.pub";
} elsif(-f $ENV{"HOME"}."/.ssh/id_dsa.pub") {
        $filename = "id_dsa.pub";
} else {
       print "I couldn't find an SSH public key generated. Try running
+ ssh-keygen then run me again.";
       exit
}
my $key = &slurp($ENV{"HOME"}."/.ssh/$filename");
my $ssh = Net::SSH::Perl->new($hostname);
$ssh->login($username,$password);
$ssh->cmd("mkdir ~/.ssh");
my ($out,$err,$exit) = $ssh->cmd("cat ~/.ssh/authorized_keys");
my $suc;
$suc = has_key($key,$out);
if($suc) {
        print "$username\@$hostname is already keyed with your key.\n"
+;
        exit;
}
$ssh->cmd("cat >> ~/.ssh/authorized_keys",$key);
($out,$err,$exit) = $ssh->cmd("cat ~/.ssh/authorized_keys");
if(has_key($key,$out)) {
        print "Your public key has been successfully added; try runnin
+g ssh $username\@$hostname to see if it works.\n";
} else {
        print "Your key could not be added.\n";
        print "Try connecting manually, then adding the contents of ".
+$ENV{"HOME"}."/.ssh/$filename manually to /home/$username/.ssh/author
+ized_keys\n";
        exit;
}
print "\n";

sub slurp {
        my $fname = shift;
        open my $FILE, '<', $fname;
        local $/;
        my $key = <$FILE>;
close $FILE;
        return $key;
}
sub has_key {
        my ($key, $keys) = @_;
        chomp($key);
        my $suc = 0;
        my @keys = split /\n/,$keys;
        my $i = 1;
        foreach my $k (@keys) {
                chomp($k);
                if($key eq $k) {
                        $suc = 1;
                        last;
                } else {
                        $suc = 0;
                }
                $i++;
        }
        return $suc;
}
[download]

Hopefully someone else will find this as interesting as I did.

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