Monkeysphere User README
You don't have to be an OpenSSH or OpenPGP expert to use the
Monkeysphere. However, you should be comfortable using secure shell
(ssh), and you should already have GnuPG installed and an OpenPGP key
pair before you begin.
As a regular user on a system where the monkeysphere package is
installed, you probably want to do a few things:
Keep your keyring up-to-date
Regularly refresh your GnuPG keyring from the keyservers. This can be
done with a simple cronjob. An example of crontab line to do this is:
0 12 * * * /usr/bin/gpg --refresh-keys > /dev/null 2>&1
This would refresh your keychain every day at noon.
Install the monkeysphere software on your system
If you haven't installed monkeysphere yet, you will need to download
and install before continuing.
Make sure that you have the GnuTLS library version 2.6 or later
installed on your system. If you can't (or don't want to) upgrade to
GnuTLS 2.6 or later, there are patches for GnuTLS 2.4 available in
the Monkeysphere git repo.
Keeping your known_hosts file in sync with your keyring
With your keyring updated, you want to make sure that OpenSSH can
still see the most recent trusted information about who the various
hosts are. This can be done with the monkeysphere-ssh-proxycommand
(see next section) or with the update-known_hosts command:
$ monkeysphere update-known_hosts
This command will check to see if there is an OpenPGP key for each
(non-hashed) host listed in the known_hosts file, and then add the
key for that host to the known_hosts file if one is found. This
command could be added to a crontab as well, if desired.
Using monkeysphere-ssh-proxycommand(1)
The best way to handle host keys is to use the monkeysphere ssh proxy
command. This command will make sure the known_hosts file is
up-to-date for the host you are connecting to with ssh. The best way
to integrate this is to add the following line to the "Host *" section
of your ~/.ssh/config file:
ProxyCommand monkeysphere ssh-proxycommand %h %p
The "Host *" section specifies what ssh options to use for all
connections. If you don't already have a "Host *" line, you can add it
by entering:
Host *
On a line by itself. Add the ProxyCommand line just below it.
Once you've completed this step - you are half-way there. You will now
be able to verify servers participating in the monkeysphere provided
their keys have been signed by someone that you trust.
FIXME: We should setup a way for someone to download a test gpg key and
then connect to a test server that is signed by this gpg key so users
can establish that they are setup correctly.
The remaining steps will complete the second half: allowing servers to
verify you based on your OpenPGP key.
Setting up an OpenPGP authentication key
First things first: you'll need to have a OpenPGP "authentication"
subkey for your current key, if you don't already have one. If you
already have a GPG key, you can generate an authentication subkey with
the gen-subkey command:
$ monkeysphere gen-subkey
If you have more than one secret key, you'll need to specify the key
you want to add the subkey to on the command line. It have already
have an ssh pub key that you use regularly, you can import this key
into GPG with the import-subkey command:
$ monkeysphere import-subkey ~/.ssh/id_rsa
Using your OpenPGP authentication key for SSH
Once you have created an OpenPGP authentication subkey, you will need
to feed it to your ssh agent.
The GnuTLS library supports this operation as of version 2.6, but
earlier versions do not. With a recent version of GnuTLS installed,
you can feed your authentication subkey to your ssh agent by running:
$ monkeysphere subkey-to-ssh-agent
FIXME: using the key with a single ssh connection?
Establish trust
Now that you have the above setup, you will need to establish an
acceptable trust path to the admin(s) of a monkeysphere-enabled server
that you will be connecting to. You need to do this because the admin
is certifying the host, and you need a mechanism to validate that
certification. The only way to do that is by indicating who you trust
to certify hosts. This is a two step process: first you must sign the
key, and then you have to indicate a trust level.
The process of signing another key is outside the scope of this
document, however the gnupg
README
details the signing process and you can find good documentation
online detailing this
process.
If you have signed your admins' key, you need to denote some kind of
trust to that key. To do this you should edit the key and use the
'trust' command. For the Monkeysphere to trust the assertions that are
made about a host, you need full calculated validity to the host
certifiers. This can be done either by giving full trust to one
host-certifying key, or by giving marginal trust to three different
host-certifiers. In the following we demonstrate how to add full trust
validity to a host-certifying key:
$ gpg --edit-key 'Jane Admin'
gpg (GnuPG) 1.4.9; Copyright (C) 2008 Free Software Foundation, Inc.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
pub 4096R/ABCD123A created: 2007-06-02 expires: 2012-05-31 usage: SC
trust: unknown validity: full
sub 2048R/01DECAF7 created: 2007-06-02 expires: 2012-05-31 usage: E
[ full ] (1). Jane Admin <jane_admin@example.net>
Command> trust
pub 4096R/ABCD123A created: 2007-06-02 expires: 2012-05-31 usage: SC
trust: unknown validity: full
sub 2048R/01DECAF7 created: 2007-06-02 expires: 2012-05-31 usage: E
[ full ] (1). Jane Admin <jane_admin@example.net>
Please decide how far you trust this user to correctly verify other users' keys
(by looking at passports, checking fingerprints from different sources, etc.)
1 = I don't know or won't say
2 = I do NOT trust
3 = I trust marginally
4 = I trust fully
5 = I trust ultimately
m = back to the main menu
Your decision? 4
pub 4096R/ABCD123A created: 2007-06-02 expires: 2012-05-31 usage: SC
trust: full validity: full
sub 2048R/01DECAF7 created: 2007-06-02 expires: 2012-05-31 usage: E
[ full ] (1). Jane Admin <jane_admin@example.net>
Please note that the shown key validity is not necessarily correct
unless you restart the program.
Command> save
Key not changed so no update needed.
$
Note: Due to a limitation with gnupg, it is not currently possible to
limit the domain scope properly, which means that if you fully trust
an admin, you'll trust all their certifications.
Because the Monkeysphre relies on GPG's definition of the OpenPGP web
of trust, it is important to understand how GPG calculates User ID
validity for a key.
Miscellaneous
Users can also maintain their own ~/.ssh/authorized_keys files with
the Monkeysphere. This is primarily useful for accounts on hosts that
are not already systematically using the Monkeysphere for user
authentication. If you're not sure whether this is the case for your
host, ask your system administrator.
If you want to do this as a regular user, use the
update-authorized_keys command:
$ monkeysphere update-authorized_keys
This command will take all the user IDs listed in the
~/.monkeysphere/authorized_user_ids file and check to see if
there are acceptable keys for those user IDs available. If so, they
will be added to the ~/.ssh/authorized_keys file.
You must have indicated reasonable ownertrust in some key for this
account, or no keys will be found with trusted certification paths.
If you find this useful, you might want to place this command in your
crontab so that revocations and rekeyings can take place
automatically.
