1 Monkeysphere Server Administrator README
2 ========================================
4 Note: This documentation is for Monkeysphere version 0.23 or later.
5 If you are running a version prior to 0.23, we recommend that you upgrade.
7 As the administrator of an SSH server, you can take advantage of the
8 Monkeysphere in two ways:
10 1. you can publish the host key of your machine to the Web of Trust
11 (WoT) so that your users can automatically verify it, and
13 2. you can set up your machine to automatically identify connecting
14 users by their presence in the OpenPGP Web of Trust.
16 These two pieces are independent: you can do one without the other.
18 Monkeysphere for host verification (monkeysphere-host)
19 ======================================================
21 Server host key publication
22 ---------------------------
24 To begin, you must first import an ssh host key. This assumes that
25 you have the ssh server installed, and that you have generated a host
26 RSA key. Once that has been done, import the key:
28 # monkeysphere-host import-key /etc/ssh/ssh_host_rsa_key server.example.net
30 This will generate an OpenPGP certificate for the server. The primary
31 user ID for this certificate will be the ssh service URI for the host,
32 (eg. `ssh://server.example.net`). Remember that the name you provide
33 here should probably be a fully qualified domain name for the host in
34 order for your users to find it.
36 Now you can display information about the host key's certificate with
37 the 'show-key' command:
39 # monkeysphere-host show-key
41 Once the host key's certificate has been generated, you'll probably
42 want to publish it to the public keyservers which distribute the Web
45 # monkeysphere-host publish-key
47 But anyone could publish a simple self-signed certificate to the WoT
48 with any name attached. Your users should be able to tell that
49 someone they know and trust with the machine (e.g. *you*, the
50 administrator) has verified that this particular key is indeed the
51 correct key. So your next step is to sign the host's key with your
54 On your (the admin's) local machine retrieve the host key (it may take
55 several minutes for the key to propagate across the keyserver
56 network), and sign it:
58 $ gpg --search '=ssh://server.example.net'
59 $ gpg --sign-key '=ssh://server.example.net'
61 Make sure you compare the fingerprint of the retrieved certificate
62 with the output from the 'show-key' command above!
64 Next, find out your key's Key ID, which is a hexadecimal string like "ABCDEF19"
66 $ gpg --list-keys '=ssh://server.example.net'
68 which will output something like:
70 pub 2048R/ABCDEF19 2009-05-07
71 uid [ full ] ssh://server.example.net
73 Finally, publish your signatures back to the keyservers, so that your
74 users can automatically verify your machine when they connect:
76 $ gpg --send-key ABCDEF19
78 See http://web.monkeysphere.info/signing-host-keys/ for more info
81 Monkeysphere for user authentication (monkeysphere-authentication)
82 ==================================================================
84 A host can maintain ssh-style `authorized_keys` files automatically
85 for its users with the Monkeysphere. This frees you (the
86 administrator) from the task of manually checking/placing SSH keys,
87 and enables users to do relatively painless key transitions, and to
88 quickly and universally revoke access if they find that their ssh key
89 has become compromised.
91 You simply tell the system what *person* (identified by her OpenPGP
92 User ID) should have access to an account, the Monkeysphere takes care
93 of generating the proper `authorized_keys` file and keeping it
94 up-to-date, and `sshd` reads the generated `authorized_keys` files
97 Monkeysphere authorized_keys maintenance
98 ----------------------------------------
100 For each user account on the server, the userids of people authorized
101 to log into that account would be placed, one per line, in:
103 ~/.monkeysphere/authorized_user_ids
105 For example, this file could contain:
107 Joe User <joe@example.net>
108 Joe User at Work <joe@example.org>
110 Provided that those exact strings are among the uids for which the user's gpg
113 The server will use the Monkeysphere to look up matching OpenPGP
114 certificates, validate them, and generate an `authorized_keys` file.
116 To validate the OpenPGP certificates, the server needs to know who it
117 can trust to correctly identify users. The individuals trusted to
118 identify users like this are known in the Monkeysphere as "Identity
119 Certifiers". One obvious choice is to trust *you*, the administrator,
120 to be an Identity Certifier.
122 You will need to know your full 40 hex character gpg fingerprint. This can be learned by doing:
124 gpg --with-colons --fingerprint user@example.org
126 Replacing "user@example.org" with either your gpg key id, or your gpg uid.
127 The output of this command is very long and difficult to read. Look for a line like:
129 fpr:::::::::D8E6414012D371BFC5AB8E2540D6B49E0E708ADF:
131 The portion between the ":::::::::" and ":" is your 40 digit fingerprint.
133 With your OpenPGP 40-digit hex fingerprint replacing `$GPGFPR`, then
134 run the following command on the server:
136 # monkeysphere-authentication add-identity-certifier $GPGFPR
138 You'll probably only set up Identity Certifiers when you set up the
139 machine. After that, you'll only need to add or remove Identity
140 Certifiers when the roster of admins on the machine changes, or when
141 one of the admins switches OpenPGP keys.
143 Now that the server knows who to trust to identify users, the
144 Monkeysphere can generate ssh-style `authorized_keys` quickly and
147 To update the Monkeysphere-generated `authorized_keys` file for user
150 # monkeysphere-authentication update-users bob
152 To update the monkeysphere `authorized_keys` file for all users on the
153 the system, run the same command with no arguments:
155 # monkeysphere-authentication update-users
157 You probably want to set up a regularly scheduled job (e.g. with cron)
158 to do this automatically.
160 Update OpenSSH server AuthorizedKeysFile configuration
161 ------------------------------------------------------
163 Generating the `authorized_keys` files is not quite enough, because
164 `sshd` needs to know where to find the generated keys.
167 You can do this by adding the following line to
168 `/etc/ssh/sshd_config`, commenting out any other `AuthorizedKeysFile`
171 AuthorizedKeysFile /var/lib/monkeysphere/authorized_keys/%u
173 Warning: Be aware that with this change in configuration, only those users whose
174 authorized keys files appear under the above path will be able to log in via
175 ssh. This includes the root user if root has ssh access. Remember to run
176 'monkeysphere-authentication update-users' if you are unsure whether any users'
177 authorized_keys files have been updated.
179 You'll need to restart `sshd` to have your changes take effect. As
180 with any change to `sshd_config`, if you're doing this remotely, be
181 sure to retain an existing session to the machine while you test your
182 changes so you don't get locked out if something went wrong.