Provided by: mandos_1.6.0-1_all 
NAME
mandos - Gives encrypted passwords to authenticated Mandos clients
SYNOPSIS
mandos [--interface NAME | -i NAME]
[--address ADDRESS | -a ADDRESS]
[--port PORT | -p PORT]
[--priority PRIORITY]
[--servicename NAME]
[--configdir DIRECTORY]
[--debug]
[--debuglevel LEVEL]
[--no-dbus]
[--no-ipv6]
[--no-restore]
[--statedir DIRECTORY]
[--socket FD]
[--foreground]
mandos {--help | -h}
mandos --version
mandos --check
DESCRIPTION
mandos is a server daemon which handles incoming request for passwords for a pre-defined
list of client host computers. For an introduction, see intro(8mandos). The Mandos server
uses Zeroconf to announce itself on the local network, and uses TLS to communicate
securely with and to authenticate the clients. The Mandos server uses IPv6 to allow Mandos
clients to use IPv6 link-local addresses, since the clients will probably not have any
other addresses configured (see the section called “OVERVIEW”). Any authenticated client
is then given the stored pre-encrypted password for that specific client.
PURPOSE
The purpose of this is to enable remote and unattended rebooting of client host computer
with an encrypted root file system. See the section called “OVERVIEW” for details.
OPTIONS
--help, -h
Show a help message and exit
--interface NAME, -i NAME
If this is specified, the server will only announce the service and listen to requests
on the specified network interface. Default is to use all available interfaces. Note:
a failure to bind to the specified interface is not considered critical, and the
server will not exit, but instead continue normally.
--address ADDRESS, -a ADDRESS
If this option is used, the server will only listen to the specified IPv6 address. If
a link-local address is specified, an interface should be set, since a link-local
address is only valid on a single interface. By default, the server will listen to all
available addresses. If set, this must normally be an IPv6 address; an IPv4 address
can only be specified using IPv4-mapped IPv6 address syntax: “::FFFF:192.0.2.3”. (Only
if IPv6 usage is disabled (see below) must this be an IPv4 address.)
--port PORT, -p PORT
If this option is used, the server will bind to that port. By default, the server will
listen to an arbitrary port given by the operating system.
--check
Run the server’s self-tests. This includes any unit tests, etc.
--debug
If the server is run in debug mode, it will run in the foreground and print a lot of
debugging information. The default is to not run in debug mode.
--debuglevel LEVEL
Set the debugging log level. LEVEL is a string, one of “CRITICAL”, “ERROR”,
“WARNING”, “INFO”, or “DEBUG”, in order of increasing verbosity. The default level is
“WARNING”.
--priority PRIORITY
GnuTLS priority string for the TLS handshake. The default is
“SECURE256:!CTYPE-X.509:+CTYPE-OPENPGP”. See gnutls_priority_init(3) for the syntax.
Warning: changing this may make the TLS handshake fail, making server-client
communication impossible.
--servicename NAME
Zeroconf service name. The default is “Mandos”. This only needs to be changed if for
some reason is would be necessary to run more than one server on the same host. This
would not normally be useful. If there are name collisions on the same network, the
newer server will automatically rename itself to “Mandos #2”, and so on; therefore,
this option is not needed in that case.
--configdir DIRECTORY
Directory to search for configuration files. Default is “/etc/mandos”. See
mandos.conf(5) and mandos-clients.conf(5).
--version
Prints the program version and exit.
--no-dbus
This option controls whether the server will provide a D-Bus system bus interface. The
default is to provide such an interface.
See also the section called “D-BUS INTERFACE”.
--no-ipv6
This option controls whether the server will use IPv6 sockets and addresses. The
default is to use IPv6. This option should never normally be turned off, even in
IPv4-only environments. This is because mandos-client(8mandos) will normally use IPv6
link-local addresses, and will not be able to find or connect to the server if this
option is turned off. Only advanced users should consider changing this option.
--no-restore
This option controls whether the server will restore its state from the last time it
ran. Default is to restore last state.
See also the section called “PERSISTENT STATE”.
--statedir DIRECTORY
Directory to save (and restore) state in. Default is “/var/lib/mandos”.
--socket FD
If this option is used, the server will not create a new network socket, but will
instead use the supplied file descriptor. By default, the server will create a new
network socket.
--foreground
This option will make the server run in the foreground and not write a PID file. The
default is to not run in the foreground, except in debug mode, which implies this
option.
OVERVIEW
This is part of the Mandos system for allowing computers to have encrypted root file
systems and at the same time be capable of remote and/or unattended reboots. The computers
run a small client program in the initial RAM disk environment which will communicate with
a server over a network. All network communication is encrypted using TLS. The clients are
identified by the server using an OpenPGP key; each client has one unique to it. The
server sends the clients an encrypted password. The encrypted password is decrypted by the
clients using the same OpenPGP key, and the password is then used to unlock the root file
system, whereupon the computers can continue booting normally.
This program is the server part. It is a normal server program and will run in a normal
system environment, not in an initial RAM disk environment.
NETWORK PROTOCOL
The Mandos server announces itself as a Zeroconf service of type “_mandos._tcp”. The
Mandos client connects to the announced address and port, and sends a line of text where
the first whitespace-separated field is the protocol version, which currently is “1”. The
client and server then start a TLS protocol handshake with a slight quirk: the Mandos
server program acts as a TLS “client” while the connecting Mandos client acts as a TLS
“server”. The Mandos client must supply an OpenPGP certificate, and the fingerprint of
this certificate is used by the Mandos server to look up (in a list read from clients.conf
at start time) which binary blob to give the client. No other authentication or
authorization is done by the server.
Table 1. Mandos Protocol (Version 1)
┌─────────────────────────┬───────────┬──────────────────────────┐
│Mandos Client │ Direction │ Mandos Server │
├─────────────────────────┼───────────┼──────────────────────────┤
│Connect │ -> │ │
├─────────────────────────┼───────────┼──────────────────────────┤
│“1\r\n” │ -> │ │
├─────────────────────────┼───────────┼──────────────────────────┤
│TLS handshake as TLS │ <-> │ TLS handshake as TLS │
│“server” │ │ “client” │
├─────────────────────────┼───────────┼──────────────────────────┤
│OpenPGP public key (part │ -> │ │
│of TLS handshake) │ │ │
├─────────────────────────┼───────────┼──────────────────────────┤
│ │ <- │ Binary blob (client will │
│ │ │ assume OpenPGP data) │
├─────────────────────────┼───────────┼──────────────────────────┤
│ │ <- │ Close │
└─────────────────────────┴───────────┴──────────────────────────┘
CHECKING
The server will, by default, continually check that the clients are still up. If a client
has not been confirmed as being up for some time, the client is assumed to be compromised
and is no longer eligible to receive the encrypted password. (Manual intervention is
required to re-enable a client.) The timeout, extended timeout, checker program, and
interval between checks can be configured both globally and per client; see mandos-
clients.conf(5).
APPROVAL
The server can be configured to require manual approval for a client before it is sent its
secret. The delay to wait for such approval and the default action (approve or deny) can
be configured both globally and per client; see mandos-clients.conf(5). By default all
clients will be approved immediately without delay.
This can be used to deny a client its secret if not manually approved within a specified
time. It can also be used to make the server delay before giving a client its secret,
allowing optional manual denying of this specific client.
LOGGING
The server will send log message with various severity levels to /dev/log. With the
--debug option, it will log even more messages, and also show them on the console.
PERSISTENT STATE
Client settings, initially read from clients.conf, are persistent across restarts, and
run-time changes will override settings in clients.conf. However, if a setting is changed
(or a client added, or removed) in clients.conf, this will take precedence.
D-BUS INTERFACE
The server will by default provide a D-Bus system bus interface. This interface will only
be accessible by the root user or a Mandos-specific user, if such a user exists. For
documentation of the D-Bus API, see the file DBUS-API.
EXIT STATUS
The server will exit with a non-zero exit status only when a critical error is
encountered.
ENVIRONMENT
PATH
To start the configured checker (see the section called “CHECKING”), the server uses
/bin/sh, which in turn uses PATH to search for matching commands if an absolute path
is not given. See sh(1).
FILES
Use the --configdir option to change where mandos looks for its configurations files. The
default file names are listed here.
/etc/mandos/mandos.conf
Server-global settings. See mandos.conf(5) for details.
/etc/mandos/clients.conf
List of clients and client-specific settings. See mandos-clients.conf(5) for details.
/var/run/mandos.pid
The file containing the process id of the mandos process started last.
/dev/log
/var/lib/mandos
Directory where persistent state will be saved. Change this with the --statedir
option. See also the --no-restore option.
/dev/log
The Unix domain socket to where local syslog messages are sent.
/bin/sh
This is used to start the configured checker command for each client. See mandos-
clients.conf(5) for details.
BUGS
This server might, on especially fatal errors, emit a Python backtrace. This could be
considered a feature.
There is no fine-grained control over logging and debug output.
This server does not check the expire time of clients’ OpenPGP keys.
EXAMPLE
Normal invocation needs no options:
mandos
Run the server in debug mode, read configuration files from the ~/mandos directory, and
use the Zeroconf service name “Test” to not collide with any other official Mandos server
on this host:
mandos --debug --configdir ~/mandos --servicename Test
Run the server normally, but only listen to one interface and only on the link-local
address on that interface:
mandos --interface eth7 --address fe80::aede:48ff:fe71:f6f2
SECURITY
SERVER
Running this mandos server program should not in itself present any security risk to the
host computer running it. The program switches to a non-root user soon after startup.
CLIENTS
The server only gives out its stored data to clients which does have the OpenPGP key of
the stored fingerprint. This is guaranteed by the fact that the client sends its OpenPGP
public key in the TLS handshake; this ensures it to be genuine. The server computes the
fingerprint of the key itself and looks up the fingerprint in its list of clients. The
clients.conf file (see mandos-clients.conf(5)) must be made non-readable by anyone except
the user starting the server (usually root).
As detailed in the section called “CHECKING”, the status of all client computers will
continually be checked and be assumed compromised if they are gone for too long.
For more details on client-side security, see mandos-client(8mandos).
SEE ALSO
intro(8mandos), mandos-clients.conf(5), mandos.conf(5), mandos-client(8mandos), sh(1)
Zeroconf[1]
Zeroconf is the network protocol standard used by clients for finding this Mandos
server on the local network.
Avahi[2]
Avahi is the library this server calls to implement Zeroconf service announcements.
GnuTLS[3]
GnuTLS is the library this server uses to implement TLS for communicating securely
with the client, and at the same time confidently get the client’s public OpenPGP key.
RFC 4291: IP Version 6 Addressing Architecture
Section 2.2: Text Representation of Addresses
Section 2.5.5.2: IPv4-Mapped IPv6 Address
Section 2.5.6, Link-Local IPv6 Unicast Addresses
The clients use IPv6 link-local addresses, which are immediately usable since a
link-local addresses is automatically assigned to a network interfaces when it is
brought up.
RFC 4346: The Transport Layer Security (TLS) Protocol Version 1.1
TLS 1.1 is the protocol implemented by GnuTLS.
RFC 4880: OpenPGP Message Format
The data sent to clients is binary encrypted OpenPGP data.
RFC 5081: Using OpenPGP Keys for Transport Layer Security
This is implemented by GnuTLS and used by this server so that OpenPGP keys can be
used.
COPYRIGHT
Copyright © 2008-2012 Teddy Hogeborn, Björn Påhlsson
This manual page is free software: you can redistribute it and/or modify it under the
terms of the GNU General Public License as published by the Free Software Foundation,
either version 3 of the License, or (at your option) any later version.
This manual page is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR
PURPOSE. See the GNU General Public License for more details.
You should have received a copy of the GNU General Public License along with this program.
If not, see http://www.gnu.org/licenses/.
NOTES
1. Zeroconf
http://www.zeroconf.org/
2. Avahi
http://www.avahi.org/
3. GnuTLS
http://www.gnu.org/software/gnutls/