Monkeysphere is a framework to leverage the OpenPGP web of trust
for OpenSSH and TLS key-based authentication. OpenPGP keys are
tracked via GnuPG, and added to the authorized_keys and known_hosts
files used by OpenSSH for connection authentication. Monkeysphere can
also be used by a validation agent to validate TLS connections
monkeysphere is the Monkeysphere client utility.
monkeysphere takes various subcommands:
Update the known_hosts file. For each specified host, gpg will be
queried for a key associated with the host URI (see HOST
optionally querying a keyserver.
If an acceptable key is found for the host (see KEY ACCEPTABILITY in
the key is added to the user's known_hosts file. If a key is found
but is unacceptable for the host, any matching keys are removed from
the user's known_hosts file. If no gpg key is found for the host,
nothing is done. If no hosts are specified, all hosts listed in the
known_hosts file will be processed. This subcommand will exit with a
status of 0 if at least one acceptable key was found for a specified
host, 1 if no matching keys were found at all, and 2 if matching keys
were found but none were acceptable. `k' may be used in place of
Update the authorized_keys file for the user executing the command
(see MONKEYSPHERE_AUTHORIZED_KEYS in ENVIRONMENT, below). First all
monkeysphere keys are cleared from the authorized_keys file. Then,
for each user ID in the user's authorized_user_ids file, gpg will be
queried for keys associated with that user ID, optionally querying a
keyserver. If an acceptable key is found (see KEY ACCEPTABILITY in
the key is added to the user's authorized_keys file.
If a key is found but is unacceptable for the user ID, any matching
keys are removed from the user's authorized_keys file. If no gpg key
is found for the user ID, nothing is done. This subcommand will exit
with a status of 0 if at least one acceptable key was found for a user
ID, 1 if no matching keys were found at all, and 2 if matching keys
were found but none were acceptable. `a' may be used in place of
Generate an authentication subkey for a private key in your GnuPG
keyring. KEYID is the key ID for the primary key for which the subkey
with "authentication" capability will be generated. If no key ID is
specified, but only one key exists in the secret keyring, that key
will be used. The length of the generated key can be specified with
the `--length' or `-l' option. `g' may be used in place of
ssh-proxycommand [--no-connect] HOST [PORT]
An ssh ProxyCommand that can be used to trigger a monkeysphere update
of the ssh known_hosts file for a host that is being connected to with
ssh. This works by updating the known_hosts file for the host first,
before an attempted connection to the host is made. Once the
known_hosts file has been updated, a TCP connection to the host is
made by exec'ing netcat(1). Regular ssh communication is then done
over this netcat TCP connection (see ProxyCommand in ssh_config(5) for
This command is meant to be run as the ssh "ProxyCommand". This can
either be done by specifying the proxy command on the command line:
This will run everything except the final exec of netcat to make the
TCP connection to the host. In this way this command can be added to
another proxy command that does other stuff, and then makes the
connection to the host itself.
The proxy command has a fairly nuanced policy for when keyservers are
queried when processing a host. If the host userID is not found in
either the user's keyring or in the known_hosts file, then the
keyserver is queried for the host userID. If the host userID is found
in the user's keyring, then the keyserver is not checked. This
assumes that the keyring is kept up-to-date, in a cronjob or the like,
so that revocations are properly handled. If the host userID is not
found in the user's keyring, but the host is listed in the known_hosts
file, then the keyserver is not checked. This last policy might
change in the future, possibly by adding a deferred check, so that
hosts that go from non-monkeysphere-enabled to monkeysphere-enabled
will be properly checked.
Setting the CHECK_KEYSERVER variable in the config file or the
MONKEYSPHERE_CHECK_KEYSERVER environment variable to either `true' or
`false' will override the keyserver-checking policy defined above and
either always or never check the keyserver for host key updates.
subkey-to-ssh-agent [ssh-add arguments]
Push all authentication-capable subkeys in your GnuPG secret keyring
into your running ssh-agent. Additional arguments are passed through
For example, to remove the authentication subkeys, pass an additional
`-d' argument. To require confirmation on each use of the key, pass
`-c'. The MONKEYSPHERE_SUBKEYS_FOR_AGENT environment can be used to
specify the full fingerprints of specific keys to add to the agent
(space separated), instead of adding them all. `s' may be used in
place of `subkey-to-ssh-agent'.
Output to stdout all acceptable keys for a given user ID.
`u' may be used in place of `keys-for-userid'.
Output the ssh fingerprints of acceptable keys for a given user ID.
Show the monkeysphere version number. `v' may be used in place of
Output a brief usage summary. `h' or `?' may be used in place of
The following environment variables will override those specified in
the monkeysphere.conf configuration file (defaults in parentheses):
Set the log level. Can be SILENT, ERROR, INFO, VERBOSE, DEBUG,
in increasing order of verbosity. (INFO)
GnuPG home directory. (~/.gnupg)
OpenPGP keyserver to use. (pool.sks-keyservers.net)
Whether or not to check keyserver when making gpg queries. (true)
Path to ssh known_hosts file. (~/.ssh/known_hosts)
Whether or not to hash to the known_hosts file entries. (true)
Path to ssh authorized_keys file. (~/.ssh/authorized_keys)
If set to `false', never prompt the user for confirmation. (true)
If set to `false', ignore too-loose permissions on known_hosts,
authorized_keys, and authorized_user_ids files. NOTE: setting this to
false may expose you to abuse by other users on the system. (true)
A space-separated list of authentication-capable subkeys to add to the
ssh agent with subkey-to-ssh-agent.
User monkeysphere config file.
System-wide monkeysphere config file.
A list of OpenPGP user IDs, one per line. OpenPGP keys with an
exactly-matching User ID (calculated valid by the designated identity
certifiers), will have any valid authorization-capable keys or subkeys
added to the given user's authorized_keys file.