THE MONKEYSPHERE ================ Monkeysphere is authentication layer that allows the sysadmin to perform authorization on OpenPGP user identities instead of on keys. It also allows end users to authenticate/identify the ssh server they are connecting to by checking the sysadmin's certification. * GENERAL GOAL - use openpgp web-of-trust to authenticate ppl for SSH * SPECIFIC GOAL - allow openssh to tie into pgp web-of-trust without modifying the openpgp spec, gpg or openssh * DESIGN GOALS - authentication, use the existing generic OpenSSH client, the admin can make it default, although end-user should be decide to use monkeysphere or not * DESIGN GOAL - use of monkeysphere should not radically change connecting-to-server experience Host identity piece of monkeysphere could be used without buying into the user authentication component. USE CASE ======== Dramatis Personae: http://en.wikipedia.org/wiki/Alice_and_Bob Backstory: http://www.conceptlabs.co.uk/alicebob.html Bob wants to sign on to the computer "mangabey.example.org" via monkeysphere framework. He doesn't yet have access to the machine, but he knows Alice, who is the admin of mangabey. Alice and Bob, being the conscientious netizens that they are, have already published their personal gpg keys to the web of trust, and being good friends, have both signed each other's keys and marked each others keys with "full" ownertrust. When Alice set up mangabey initially, she published an OpenPGP key for the machine with the special userid of "ssh://mangabey.example.org". She also signed mangabey's OpenPGP key and published this certification to commonly-used keyservers. Alice also configured mangabey to treat her own key with full ownertrust, so that it knows how to identify connecting users. Now, Alice creates a user account "bob" on mangabey, and puts Bob's userid ("Bob ") in the authorized_user_ids file for user bob on mangabey. The monkeysphere automatically (via cron or inotify hook) takes each userid in bob's authorized_user_ids file, and looks on a keyserver to find all public keys associated with that user ID, with the goal of populating the authorized_keys file for bob@mangabey. In particular: for each key found, the server evaluates the calculated validity of the specified user ID based on the ownertrust rules it has configured ("trust alice's certifications fully", in this example). For each key for which the user ID in question is fully-valid, it extracts all DSA- or RSA-based primary or secondary keys marked with the authentication usage flag, and converts these OpenPGP public keys into ssh public keys. These keys are automatically placed into the authorized_keys file for bob. Bob now attempts to connect, by firing up a terminal and invoking: "ssh bob@mangabey.example.org". Bob's monkeysphere-enabled ssh client notices that mangabey.example.org isn't already available in bob's known_hosts file, and fetches the host key for mangabey from the public keyservers, with the goal of populating Bob's local known_hosts file. In particular: the monkeysphere queries its configured keyservers to find all public keys with User ID ssh://mangabey.example.org. For each public key found, it checks the relevant User ID's validity, converts any authentication-capable OpenPGP public keys into ssh public keys if the User ID validity is acceptable, and finally insert those keys into Bob's known_hosts file. On Bob's side, since mangabey's key had "full" validity (it was signed by Alice, whom he fully trusts), Bob's ssh client deems mangabey "known" and no further host key checking is required. On mangabey's side, since Bob's key has "full" validity (it had been signed by Alice, mangabey's trusted administrator), Bob is authenticated and therefore authorized to log into his account.