On 29 Apr 2009, at 17:29, Jason Davies wrote:
I'm in the finishing stages of writing a cookie-based authentication
handler for CouchDB in Erlang. This is primarily going to be useful
for CouchApps (apps running purely in CouchDB), but this also
touches on a generic way to authenticate users via a CouchDB
database, which could be adopted by the current default HTTP Basic
auth handler.
I've put the code up here: http://github.com/jasondavies/couchdb/tree/master
[snip]
Still to do:
- Use some kind of challenge/response mechanism for logging in via
AJAX. At the moment the login handler just takes a plaintext
username/password combination sent via POST. I was thinking of
using SRP (http://en.wikipedia.org/wiki/Secure_remote_password_protocol
), however I believe this would require state to be stored on the
server, and maybe isn't appropriate for this.
I've now implemented SRP auth and it is working merrily. I'm in
discussions with SRP's inventor, Tom Wu, about a potentially simpler
protocol as SRP implemented in JavaScript is probably overkill for
unencrypted HTTP (it is vulnerable to MITM injection attacks of the
JavaScript code itself, whereas SRP would otherwise protect against
active attacks). It might be worth supporting a simpler protocol sent
over SSL too e.g. plaintext credentials.
Any suggestions for a more appropriate authentication protocol would
be much appreciated.
- Store hashes of passwords in the database. We can already do
this, but we might want to send something like hash(password
+password_salt) to the server, which would involve retrieving the
appropriate password_salt for a given user first.
Done. In SRP, a special non-plaintext-equivalent "verifier" is stored
in the database along with a salt.
- At the moment the cookie is set for Path=/ - this probably needs
to be set to Path=/current_database by default, and be configurable
so that it can be used by a proxy.
- I need to work on making my tests more exhaustive, they're pretty
minimal for the moment.
These still need working on.
- All this auth stuff should probably go into its own module,
couch_httpd_auth or similar.
Also done.
--
Jason Davies
www.jasondavies.com
