You can now enable this in CouchDB using the built-in couch_peruser option.
couchperuser is a CouchDB daemon that ensures that a private per-user database exists for each document in _users. These databases are writable only by the corresponding user.
Currently this is very much purpose-built for CodeCosmos. Databases are in the form:
userdb-{hex encoded username}
For example, the user bob will have a database named userdb-626f62.
The reason for hex encoding is that CouchDB usernames have no restrictions, but CouchDB databases have restrictions. Hex encoding the UTF-8 representation of the username is a transformation that's easy to correctly implement in just about any language, especially JavaScript and Erlang. Other encodings would be possible, but would require additional client and server-side code to support that encoding. This is the simplest scheme that is obviously correct.
Install any dependencies. couchperuser requires rebar, e.g.
$ brew install rebar
Ensure the plugins directory exists, e.g.
$ mkdir /usr/local/Cellar/couchdb/1.6.0_1/lib/couchdb/plugins
Clone (download) the repo:
$ git clone https://github.com/etrepum/couchperuser.git
Move the plugin files:
$ mv couchperuser /usr/local/Cellar/couchdb/1.6.0_1/lib/couchdb/plugins
Build the plugin files:
$ cd /usr/local/Cellar/couchdb/1.6.0_1/lib/couchdb/plugins/couchperuser
$ make
Restart couchdb