Summary:
Fixes T2229. This sets the stage for a patch similar to D7417, but for SSH. In particular, SSH 6.2 introduced an `AuthorizedKeysCommand` directive, which lets us do this in a mostly-reasonable way without needing users to patch sshd (if they have a recent enough version, at least).
The way the `AuthorizedKeysCommand` works is that it gets run and produces an `authorized_keys`-style file fragment. This isn't ideal, because we have to dump every key into the result, but should be fine for most installs. The earlier patch against `sshd` passes the public key itself, which allows the script to just look up the key. We might use this eventually, since it can scale much better, so I haven't removed it.
Generally, auth is split into two scripts now which mostly do the same thing:
- `ssh-auth` is the AuthorizedKeysCommand auth, which takes nothing and dumps the whole keyfile.
- `ssh-auth-key` is the slightly cleaner and more scalable (but patch-dependent) version, which takes the public key and dumps only matching options.
I also reworked the argument parsing to be a bit more sane.
Test Plan:
This is somewhat-intentionally a bit obtuse since I don't really want anyone using it yet, but basically:
- Copy `phabricator-ssh-hook.sh` to somewhere like `/usr/libexec/openssh/`, chown it `root` and chmod it `500`.
- This script should probably also do a username check in the future.
- Create a copy of `sshd_config` and fix the paths/etc. Point the KeyScript at your copy of the hook.
- Start a copy of sshd (6.2 or newer) with `-f <your config file>` and maybe `-d -d -d` to foreground and debug.
- Run `ssh -p 2222 localhost` or similar.
Specifically, I did this setup and then ran a bunch of commands like:
- `ssh host` (denied, no command)
- `ssh host ls` (denied, not supported)
- `echo '{}' | ssh host conduit conduit.ping` (works)
Reviewers: btrahan
Reviewed By: btrahan
CC: hach-que, aran
Maniphest Tasks: T2229, T2230
Differential Revision: https://secure.phabricator.com/D7419
