/mandos/release

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152 by Teddy Hogeborn
* README: New file.
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-*- org -*-
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* Mandos
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  - Have your cake and eat it too!
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  You know how it is.  Youve heard of it happening.  The Man comes
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  and takes away your servers, your friends servers, the servers of
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* README: New file.
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  everybody in the same hosting facility. The servers of their
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  neighbors, and their neighbors friends.  The servers of people who
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  owe them money.  And like *that*, theyre gone.  And you doubt
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  youll ever see them again.
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  That is why your servers have encrypted root file systems.  However,
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  theres a downside.  Theres no going around it: rebooting is a
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  pain.  Dragging out that rarely-used keyboard and screen and
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  unraveling cables behind your servers to plug them in to type in
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  that password is messy, especially if you have many servers.  There
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  are some people who do clever things like using serial line consoles
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  and daisy-chain it to the next server, and keep all the servers
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  connected in a ring with serial cables, which will work, if your
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  servers are physically close enough.  There are also other
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  out-of-band management solutions, but with *all* these, you still
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  have to be on hand and manually type in the password at boot time.
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  Otherwise the server just sits there, waiting for a password.
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  Wouldnt it be great if you could have the security of encrypted
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  root file systems and still have servers that could boot up
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  automatically if there was a short power outage while you were
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  asleep?  That you could reboot at will, without having someone run
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  over to the server to type in the password?
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  Well, with Mandos, you (almost) can!  The gain in convenience will
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  only be offset by a small loss in security.  The setup is as
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  follows:
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  The server will still have its encrypted root file system.  The
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  password to this file system will be stored on another computer
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  (henceforth known as the Mandos server) on the same local network.
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  The password will *not* be stored in plaintext, but encrypted with
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  OpenPGP.  To decrypt this password, a key is needed.  This key (the
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  Mandos client key) will not be stored there, but back on the
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  original server (henceforth known as the Mandos client) in the
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  initial RAM disk image.  Oh, and all network Mandos client/server
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  communications will be encrypted, using TLS (SSL).
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  So, at boot time, the Mandos client will ask for its encrypted data
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  over the network, decrypt it to get the password, use it to decrypt
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  the root file, and continue booting.
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  Now, of course the initial RAM disk image is not on the encrypted
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  root file system, so anyone who had physical access could take the
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  Mandos client computer offline and read the disk with their own
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  tools to get the authentication keys used by a client.  *But*, by
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  then the Mandos server should notice that the original server has
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  been offline for too long, and will no longer give out the encrypted
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  key.  The timing here is the only real weak point, and the method,
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  frequency and timeout of the servers checking can be adjusted to
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  any desired level of paranoia
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  (The encrypted keys on the Mandos server is on its normal file
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  system, so those are safe, provided the root file system of *that*
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  server is encrypted.)
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* FAQ - couldnt the security be defeated by...
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** Grabbing the Mandos client key from the initrd *really quickly*?
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   This, as mentioned above, is the only real weak point.  But if you
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   set the timing values tight enough, this will be really difficult
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   to do.  An attacker would have to physically disassemble the client
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   computer, extract the key from the initial RAM disk image, and then
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   connect to a *still online* Mandos server to get the encrypted key,
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   and do all this *before* the Mandos server timeout kicks in and the
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   Mandos server refuses to give out the key to anyone.
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   Now, as the typical procedure seems to be to barge in and turn off
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   and grab *all* computers, to maybe look at them months later, this
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   is not likely.  If someone does that, the whole system *will* lock
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   itself up completely, since Mandos servers are no longer running.
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   For sophisticated attackers who *could* do the clever thing, *and*
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   had physical access to the server for enough time, it would be
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   simpler to get a key for an encrypted file system by using hardware
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   memory scanners and reading it right off the memory bus.
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* README: New file.
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** Replay attacks?
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   Nope, the network stuff is all done over TLS, which provides
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   protection against that.
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** Man-in-the-middle?
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   No.  The server only gives out the passwords to clients which have
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   *in the TLS handshake* proven that they do indeed hold the OpenPGP
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   private key corresponding to that client.
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** Physically grabbing the Mandos server computer?
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   You could protect *that* computer the old-fashioned way, with a
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   must-type-in-the-password-at-boot method.  Or you could have two
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   computers be the Mandos server for each other.
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   Multiple Mandos servers can coexist on a network without any
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   trouble.  They do not clash, and clients will try all available
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   servers.  This means that if just one reboots then the other can
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   bring it back up, but if both reboots at the same time they will
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   stay down until someone types in the password on one of them.
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** Faking ping replies?
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   The default for the server is to use "fping", the replies to which
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   could be faked to eliminate the timeout.  But this could easily be
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   changed to any shell command, with any security measures you like.
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   It could, for instance, be changed to an SSH command with strict
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   keychecking, which could not be faked.  Or IPsec could be used for
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   the ping packets, making them secure.
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* Security Summary
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  So, in summary:  The only weakness in the Mandos system is from
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  people who have:
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  1. The power to come in and physically take your servers, *and*
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  2. The cunning and patience to do it carefully, one at a time, and
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     *quickly*, faking Mandos client/server responses for each one
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     before the timeout.
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  While there are some who may be threatened by people who have *both*
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  these attributes, they do not, probably, constitute the majority.
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  If you *do* face such opponents, you must figure that they could
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  just as well open your servers and read the file system keys right
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  off the memory by running wires to the memory bus.
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  What Mandos is designed to protect against is *not* such determined,
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  focused, and competent attacks, but against the early morning knock
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  on your door and the sudden absence of all the servers in your
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  server room.  Which it does nicely.
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216 by Teddy Hogeborn
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* The Plugin System
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  In the early designs, the mandos-client(8mandos) program (which
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  retrieves a password from the Mandos server) also prompted for a
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  password on the terminal, in case a Mandos server could not be
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* README (The Plugin System): Improve wording.
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  found.  Other ways of retrieving a password could easily be
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  envisoned, but this multiplicity of purpose was seen to be too
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  complex to be a viable way to continue.  Instead, the original
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  program was separated into mandos-client(8mandos) and
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  password-prompt(8mandos), and a plugin-runner(8mandos) exist to run
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  them both in parallel, allowing the first successful plugin to
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  provide the password.  This opened up for any number of additional
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  plugins to run, all competing to be the first to find a password and
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  provide it to the plugin runner.
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* Makefile: Add HTML rules for manual pages.
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  Three additional plugins are provided:
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* README: Refer to man pages of usplash, splashy, and askpass-fifo.
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  * usplash(8mandos)
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    This prompts for a password when using usplash(8).
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* README: Refer to man pages of usplash, splashy, and askpass-fifo.
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  * splashy(8mandos)
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    This prompts for a password when using splashy(8).
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* README: Refer to man pages of usplash, splashy, and askpass-fifo.
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  * askpass-fifo(8mandos)
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    To provide compatibility with the "askpass" program from
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    cryptsetup, this plugin listens to the same FIFO as askpass would
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    do.
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  More plugins can easily be written and added by the system
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  administrator; see the section called "WRITING PLUGINS" in
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  plugin-runner(8mandos) to learn the plugin requirements.
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183 by Teddy Hogeborn
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* Copyright
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237.2.9 by Teddy Hogeborn
* README: Update copyright year; add "2009".
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    Copyright © 2008,2009 Teddy Hogeborn
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    Copyright © 2008,2009 Björn Påhlsson
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** License:
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   This program is free software: you can redistribute it and/or
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   modify it under the terms of the GNU General Public License as
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   published by the Free Software Foundation, either version 3 of the
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   License, or (at your option) any later version.
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   This program is distributed in the hope that it will be useful, but
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   WITHOUT ANY WARRANTY; without even the implied warranty of
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   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
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   General Public License for more details.
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   You should have received a copy of the GNU General Public License
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   along with this program.  If not, see
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   <http://www.gnu.org/licenses/>.