Multi-user, access-controlled Darcs

Exercise: grant darcs access to users connecting over SSH with the following specification:

• they should be able to access only that is definitely needed;
• repository access (read or read-write) should be easy to set up per user and per repository.

The key of the solution is a wrapper that allows only the appropriate darcs commands to be used; this simply excludes browsing though SFTP as well. Setup is trivial: upload the attached script to /usr/local/bin dir of the server as darcs-shell, and create a shared account (practically called darcs) that will be used for all server-side stuff. The shell of this user must be /usr/local/bin/darcs-shell. Access for developers can be set up pretty straightforward: add the public SSH key of any given developer to the darcs account's ~/.ssh/authorized_keys2 file, with the following trick:

command="darcs-shell developername" the_original_ssh_key

Write/read-only access is governed by the /usr/local/darcs/access file with the following format (do not forget the trailing slashes in repo paths):

developer1:/path/to/repo/:rw
developer2:/path/to/repo2/:r


I was offered a hand by Miklós Vajna and used his git-shell2 script.