Re: Current network-password-saving feature needs improvement.

[David Wheeler <dwheeler ida org>]

The more I think about it, the more useful a
general "password saving" feature appears
for open source operating systems.

All web browsers need to store passwords for
later use, and obviously more and more applets
need to store passwords for later use too.
"Shrouding" doesn't help protect against
people who steal your laptop.  Having
"master passwords" helps, but currently people
have to enter multiple master passwords
(one for GNOME, one for SSH, one for Mozilla, ...).
That's annoying.

It'd be great if there was a simple, standard mechanism
to support "single sign-on" for Unix-like systems.
Just log in once, and the system can automatically
encrypt and store all the other passwords you'd like it
to using your login password.  Sounds user-friendly to me.

Perhaps a small "secret server" could be created
that ran on behalf of a user, and could get and store
secrets on behalf of that user.
Here are a few ideas:
* Given an application name and key it could get a secret
  (e.g., "I'm Mozilla, what's the password for
   bogus wazoo com?" returns "sugob").  That way you could
  disambiguate between different applications.
  Perhaps you could limit requests so only certain applications could
  get certain keys, but you'd have to find a way to
  trust the application name - I'm not sure how to do that
  nicely.
* Given an application name, key, and secret, it could be
  stored.
* It should be startable via PAM or GDM, so the
  login password could be used to generate the
  encryption key.  However, the password itself shouldn't
  be encryption key, since if a nasty application takes over
  the machine that would reveal the login password.
  Thus, use a cryptographic hash of the login password plus
  a nice large salt (which is stored as plaintext in the
  keyfile)... an attacker gets the other passwords, but
  possibly not the login password.  By only using the
  password and salt to determine the encryption key, the
  master key file could be later moved and used on other machines.
* It shouldn't REQUIRE being started with PAM or GDM - if
  it's not started by login, or the user wants to use a
  separate password when accessing the keyfile, then it should
  gracefully ask (like ssh can do now).  Thus, the master keyfile
  should have some indicator that says "ask separately".
* Perhaps start with ssh-agent.
* It should be small and work for EVERYONE.  Then Mozilla,
  GNOME applets, etc. should all be modified to work with it
  when available.


Comments?  Thoughts?


--- David A. Wheeler
    dwheeler ida org