CPANization

1 files changed, 91 insertions, 0 deletions

diff --git a/bin/ssh-forcecommand b/bin/ssh-forcecommand
new file mode 100755
index 0000000..c1b37eb
--- /dev/null
+++ b/bin/ssh-forcecommand
@@ -0,0 +1,91 @@
+#!/usr/bin/env perl
+use strict;
+use warnings;
+
+my $conffile = shift or die("Usage: $0 <configfile>\n");
+my %commands;
+my $input = $ENV{'SSH_ORIGINAL_COMMAND'} or die("No command\n");;
+
+my $VERSION = '0.0';
+
+open(my $conf, '<', $conffile) or die("Can't open $conffile: $!\n");
+
+while (my $line = <$conf>) {
+	my ($key, $value) = ($line =~ m{ ^ ([^=]+?) \s* = \s* (.+) $ }x);
+	if ($key and $value) {
+		$commands{$key} = $value;
+	}
+}
+close($conf) or die("Cannot close $conffile: $!\n");
+
+if (exists $commands{$input}) {
+	exec($commands{$input});
+	exit 1;
+}
+
+die("Unknown command\n");
+
+__END__
+
+=head1 NAME
+
+ssh-forcecommand - Whitelist remote commands via ssh config
+
+=head1 SYNOPSIS
+
+In .ssh/authorized_keys:
+
+    command="/usr/local/lib/ssh-forcecommand /etc/forcecommand/backup",no-agent-forwarding,no-port-
+    forwarding,no-pty,no-X11-forwarding $key
+
+=head1 DESCRIPTION
+
+B<ssh-forcecommand> is a trivial script to safely execute remote commands via
+ssh.  It is especially aimed at automated remote commands (so, ssh keys not
+secured via password), where a compromise of the remote system (-> private
+key) could also compromise the local system.
+
+To prevent this, you can put the forcecommand into the ssh config
+(authorized_keys, to be precise), so the remote system can only execute a set
+of statically defined commands.  This way, compromising the local system is
+made much more difficult.
+
+=head1 CONFIGURATION
+
+For every public key you want to restrict to the forcecommand, add a line like
+in SYNOPSIS to the F<.ssh/authorized_keys>.
+
+command="..." sets the forcecommand, the other options disable potentially
+dangerous stuff like port forwardig (Though that is not meant to be an
+exhaustive list).
+
+As you see, the forcecommand accepts exactly one argument, which is the config
+defining the allowed commands.  This way, you can restrict different ssh keys
+to different sets of commands.  A few example configs are provided with this
+script, see the examples directory.
+
+=head1 USAGE
+
+Assume you have the following line in your forcecommand config:
+
+    home = tar -C / -cf - home
+
+Now, on the remote system, run this:
+
+    ssh user@yourhost home
+
+On your system, this will translate to:
+
+    tar -C / -cf - home
+
+The forcecommand is 100% static, variables or appending of stuff is not
+supported.  No part of the original ssh command will be dynamically used in
+the resulting command.  This makes ssh-forcecommand quite secure.
+
+=head1 AUTHOR
+
+Copyright (C) 2011 by Daniel Friesel E<gt>derf@finalrewind.orgE<lt>
+
+=head1 LICENSE
+
+  0. You just DO WHAT THE FUCK YOU WANT TO.