secure-mcserv1

Usage

NAME secure-mcserv

secure-mcserv - secure server for encrypted login, file transfer and socket forwarding.

Overview

secure-mcserv is a server for the Midnight Commander (network) filesystem (mcfs) of the Midnight Commander vfs (virtual file system). It is part of the mirrordir package. In can operate as a substitute to the Midnight Commander's native mcserv daemon, although It has several extensions for use with mirrordir.

security and compression

This is not so much a feature of secure-mcserv as of the transparent secure TCP layer implemented for the whole of mirrordir. This layer can operate in normal mode, compressed (gzipped) mode, encrypted mode, or compressed and encrypted mode. The mode of connection is autodetected from magic numbers at the head of the TCP stream. The Midnight Commander can use secure-mcserv instead of its native mcserv. See the -z, --secure and -K options of mirrordir(1).

Denying access from specific hosts

You can add to your /etc/hosts.allow file lines like the following:

    secure-mcserv:  <source-ip-address> : ALLOW
    secure-mcserv:  212.89.128.0/255.255.255.0 : ALLOW
    secure-mcserv:  ALL : DENY

(This feature was submitted to me by Juergen Kammer <[email protected]> who claims it works.)

logins

You can securely login to secure-mcserv with pslogin which comes with the mirrordir distribution. This is analogous to rlogin(1) working with rlogind(1). See the --login-mode option of mirrordir(1).

TCP socket forwarding

Using the forward-socket(1) command of the mirrordir distribution, you can forward arbitrary TCP socket connections over a secure and/or compressed TCP channel. This is very useful for making encrypted services out of ordinary services. forward-socket(1) has an examples section.

Options

-d

Become a daemon (set -q). This option will almost always be used. Alternative -d can be omitted and -v (see below) set to debug failed connections.

-q

Quiet mode. This is the default.

-f

Try ftp authentication if normal authentication fails.

-v

Verbose mode. Print out various debugging information.

-p port

Specify a port number to listen to. The default is 9876.

-s server[:port]

Specify a password server to use. The password server is just another machine running secure-mcserv albeit without the -s option.

This is a very useful option if you have lots of machines that a group of users have to be able to log into. Create accounts for all these users on each machine and disable them by editing their password fields to * in /etc/password (or /etc/shadow).

Select one machine as your password server (say it is called passerv.my.doma.in). This machine will contain proper password fields in /etc/password. On this machine run secure-mcserv -d as usual. On all other machines, run secure-mcserv -d -s passerv.my.doma.in

Because all intermediate connections use the same encrypted TCP stream, and are all equally secure, you can use this method even if passerv.my.doma.in is across the open internet. In fact the very method to authenticate against the password server is to check the exit status of the command:

pslogin user@passerv.my.doma.in --test-login --read-password-from-stdin

I also see no reason why you cannot use cascading password servers, although there is no advantage to doing this.

Each authentication takes the same time to execute, so using a password server takes twice as long as a normal login, because of the second connection it has to make to the password server. Cascades will take that much time extra for each successive password server.

Files

See mirrordir(1).