4
4
- Have your cake and eat it too!
6
You know how it is. You’ve heard of it happening. The Man comes
7
and takes away your servers, your friends’ servers, the servers of
6
You know how it is. You've heard of it happening. The Man comes
7
and takes away your servers, your friends' servers, the servers of
8
8
everybody in the same hosting facility. The servers of their
9
neighbors, and their neighbors’ friends. The servers of people who
10
owe them money. And like *that*, they’re gone. And you doubt
11
you’ll ever see them again.
9
neighbors, and their neighbors' friends. The servers of people who
10
owe them money. And like *that*, they're gone. And you doubt
11
you'll ever see them again.
13
13
That is why your servers have encrypted root file systems. However,
14
there’s a downside. There’s no going around it: rebooting is a
14
there's a downside. There's no going around it: rebooting is a
15
15
pain. Dragging out that rarely-used keyboard and screen and
16
16
unraveling cables behind your servers to plug them in to type in
17
17
that password is messy, especially if you have many servers. There
48
48
the root file, and continue booting.
50
50
Now, of course the initial RAM disk image is not on the encrypted
51
root file system, so anyone who had physical access could take the
52
Mandos client computer offline and read the disk with their own
53
tools to get the authentication keys used by a client. *But*, by
54
then the Mandos server should notice that the original server has
55
been offline for too long, and will no longer give out the encrypted
56
key. The timing here is the only real weak point, and the method,
57
frequency and timeout of the server’s checking can be adjusted to
58
any desired level of paranoia
51
root file system, so anyone who would come and take the the whole
52
computer would have the Mandos client key when they took the server
53
offline and read the disk with their own tools. *But*, by then the
54
Mandos server will have detected that the original server is no
55
longer online and will no longer give out the encrypted key. The
56
timing here is the only real weak point, and the method, frequency
57
and timeout of checking can be adjusted to any desired level of
60
60
(The encrypted keys on the Mandos server is on its normal file
61
system, so those are safe, provided the root file system of *that*
61
system, so those are safe, provided the root file system of that
62
62
server is encrypted.)
64
64
* FAQ - couldn’t the security be defeated by...
69
69
to do. An attacker would have to physically disassemble the client
70
70
computer, extract the key from the initial RAM disk image, and then
71
71
connect to a *still online* Mandos server to get the encrypted key,
72
and do all this *before* the Mandos server timeout kicks in and the
73
Mandos server refuses to give out the key to anyone.
75
Now, as the typical procedure seems to be to barge in and turn off
76
and grab *all* computers, to maybe look at them months later, this
77
is not likely. If someone does that, the whole system *will* lock
78
itself up completely, since Mandos servers are no longer running.
80
For sophisticated attackers who *could* do the clever thing, *and*
81
had physical access to the server for enough time, it would be
82
simpler to get a key for an encrypted file system by using hardware
83
memory scanners and reading it right off the memory bus.
72
all *before* the Mandos server timeout kicks in and the Mandos
73
server refuses to give out the key to anyone.
75
As the typical SOP seems to be to barge in and turn off and grab
76
*all* computers to maybe look at them months later, this is not
86
80
Nope, the network stuff is all done over TLS, which provides
94
88
** Physically grabbing the Mandos server computer?
95
89
You could protect *that* computer the old-fashioned way, with a
96
90
must-type-in-the-password-at-boot method. Or you could have two
97
computers be the Mandos server for each other.
99
Multiple Mandos servers can coexist on a network without any
100
trouble. They do not clash, and clients will try all available
101
servers. This means that if just one reboots then the other can
102
bring it back up, but if both reboot at the same time they will
103
stay down until someone types in the password on one of them.
91
computers be the Mandos server for each other. (Multiple Mandos
92
servers can coexist on a network without any trouble. They do not
93
clash, and clients will try all available servers.)
105
95
** Faking ping replies?
106
96
The default for the server is to use "fping", the replies to which
122
112
these attributes, they do not, probably, constitute the majority.
124
114
If you *do* face such opponents, you must figure that they could
125
just as well open your servers and read the file system keys right
126
off the memory by running wires to the memory bus.
128
What Mandos is designed to protect against is *not* such determined,
129
focused, and competent attacks, but against the early morning knock
130
on your door and the sudden absence of all the servers in your
131
server room. Which it does nicely.
134
In the early designs, the mandos-client(8mandos) program (which
135
retrieves a password from the Mandos server) also prompted for a
136
password on the terminal, in case a Mandos server could not be
137
found. Other ways of retrieving a password could easily be
138
envisoned, but this multiplicity of purpose was seen to be too
139
complex to be a viable way to continue. Instead, the original
140
program was separated into mandos-client(8mandos) and
141
password-prompt(8mandos), and a plugin-runner(8mandos) exist to run
142
them both in parallel, allowing the first successful plugin to
143
provide the password. This opened up for any number of additional
144
plugins to run, all competing to be the first to find a password and
145
provide it to the plugin runner.
147
Four additional plugins are provided:
149
This prompts for a password when using plymouth(8).
151
This prompts for a password when using usplash(8).
153
This prompts for a password when using splashy(8).
154
* askpass-fifo(8mandos)
155
To provide compatibility with the "askpass" program from
156
cryptsetup, this plugin listens to the same FIFO as askpass would
159
More plugins can easily be written and added by the system
160
administrator; see the section called "WRITING PLUGINS" in
161
plugin-runner(8mandos) to learn the plugin requirements.
165
Copyright © 2008-2010 Teddy Hogeborn
166
Copyright © 2008-2010 Björn Påhlsson
170
This program is free software: you can redistribute it and/or
171
modify it under the terms of the GNU General Public License as
172
published by the Free Software Foundation, either version 3 of the
173
License, or (at your option) any later version.
175
This program is distributed in the hope that it will be useful, but
176
WITHOUT ANY WARRANTY; without even the implied warranty of
177
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
178
General Public License for more details.
180
You should have received a copy of the GNU General Public License
181
along with this program. If not, see
182
<http://www.gnu.org/licenses/>.
115
just as well open your servers and read the keys right off the
116
memory by running wires to the memory bus.
118
What this system is designed to protect against is *not* such
119
determined, focused, and competent attacks, but against the early
120
morning knock on your door and the sudden absence of all servers in
added
removed
README
