1
1
<?xml version="1.0" encoding="UTF-8"?>
2
2
<!DOCTYPE refentry PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
3
3
"http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
4
<!ENTITY TIMESTAMP "2012-01-01">
4
<!ENTITY TIMESTAMP "2019-04-10">
5
5
<!ENTITY % common SYSTEM "common.ent">
61
68
The computers run a small client program in the initial RAM disk
62
69
environment which will communicate with a server over a network.
63
70
All network communication is encrypted using TLS. The clients
64
are identified by the server using an OpenPGP key; each client
71
are identified by the server using a TLS public key; each client
65
72
has one unique to it. The server sends the clients an encrypted
66
73
password. The encrypted password is decrypted by the clients
67
using the same OpenPGP key, and the password is then used to
74
using a separate OpenPGP key, and the password is then used to
68
75
unlock the root file system, whereupon the computers can
69
76
continue booting normally.
73
80
<refsect1 id="introduction">
74
81
<title>INTRODUCTION</title>
83
<!-- This paragraph is a combination and paraphrase of two
84
quotes from the 1995 movie “The Usual Suspects”. -->
76
85
You know how it is. You’ve heard of it happening. The Man
77
86
comes and takes away your servers, your friends’ servers, the
78
87
servers of everybody in the same hosting facility. The servers
124
133
So, at boot time, the Mandos client will ask for its encrypted
125
data over the network, decrypt it to get the password, use it to
126
decrypt the root file, and continue booting.
134
data over the network, decrypt it to get the password, use the
135
password to decrypt the root file system, and continue booting.
129
138
Now, of course the initial RAM disk image is not on the
135
144
long, and will no longer give out the encrypted key. The timing
136
145
here is the only real weak point, and the method, frequency and
137
146
timeout of the server’s checking can be adjusted to any desired
141
150
(The encrypted keys on the Mandos server is on its normal file
193
202
No. The server only gives out the passwords to clients which
194
203
have <emphasis>in the TLS handshake</emphasis> proven that
195
they do indeed hold the OpenPGP private key corresponding to
204
they do indeed hold the private key corresponding to that
209
<refsect2 id="sniff">
210
<title>How about sniffing the network traffic and decrypting it
211
later by physically grabbing the Mandos client and using its
214
We only use <acronym>PFS</acronym> (Perfect Forward Security)
215
key exchange algorithms in TLS, which protects against this.
218
<refsect2 id="fakeping">
219
<title>Faking ping replies?</title>
237
<refsect2 id="fakecheck">
238
<title>Faking checker results?</title>
221
The default for the server is to use
240
If the Mandos client does not have an SSH server, the default
241
is for the Mandos server to use
222
242
<quote><literal>fping</literal></quote>, the replies to which
223
243
could be faked to eliminate the timeout. But this could
224
244
easily be changed to any shell command, with any security
225
measures you like. It could, for instance, be changed to an
226
SSH command with strict keychecking, which could not be faked.
227
Or IPsec could be used for the ping packets, making them
245
measures you like. If the Mandos client
246
<emphasis>has</emphasis> an SSH server, the default
247
configuration (as generated by
248
<command>mandos-keygen</command> with the
249
<option>--password</option> option) is for the Mandos server
250
to use an <command>ssh-keyscan</command> command with strict
251
keychecking, which can not be faked. Alternatively, IPsec
252
could be used for the ping packets, making them secure.
added
removed
intro.xml
