Switch the API to use a Unix Domain Socket

This drops support for the TCP port and switches to using a socket at
/var/run/weldr/api.socket

Also add the start of some docs for lorax-composer.

--host and --port argument have been removed.

--group sets the group name to use for access to the socket and its
parent directory. Defaults to 'weldr'

--socket sets the full path to the socket to create. Defaults to
'/var/run/weldr/api.socket'

docs/index.rst

@@ -14,6 +14,7 @@ Contents:
    intro
    lorax
    livemedia-creator
+   lorax-composer
    product-images
    modules
 

docs/lorax-composer.rst

@@ -0,0 +1,37 @@
+lorax-composer
+==============
+
+:Authors:
+    Brian C. Lane <bcl@redhat.com>
+
+lorax-composer is an API server that is compatible with the Weldr project's
+bdcs-api REST protocol. More information on Weldr can be found [on the Weldr
+blog](https://www.weldr.io).
+
+The server runs as root, and communication with it is via a unix domain socket
+(``/run/weldr/api.socket`` by default). The directory and socket are owned by
+root:weldr so that any user in the weldr group can use the API to control
+lorax-composer.
+
+When starting the server it will check for the correct permissions and
+ownership of pre-existing directory, or it will create a new one if none exist.
+The socket path and group owner's name can be changed from the cmdline by
+passing it the ``--socket`` and ``--group`` arguments.
+
+Logs
+----
+
+Logs are stored under ``/var/log/lorax-composer/`` and includes all console
+messages as well as extra debugging info and API requests.
+
+Quickstart
+----------
+
+1. Create a ``weldr`` group by running ``groupadd weldr``
+2. Remove any pre-existing socket directory with ``rm -rf /run/weldr/``
+   A new directory with correct permissions will be created the first time the server runs.
+3. Either start it via systemd with ``systemctl start lorax-composer`` or
+   run it directly with ``lorax-composer /path/to/recipes/``
+
+The ``/path/to/recipes/`` is where the recipe's git repo will be created, and all
+the recipes created with the ``/api/v0/recipes/new`` route will be stored.

src/sbin/lorax-composer

@@ -25,9 +25,11 @@ server_log = logging.getLogger("server")
 yum_log = logging.getLogger("yum")
 
 import argparse
+import grp
 import os
 import sys
 from threading import Lock
+from gevent import socket
 from gevent.wsgi import WSGIServer
 
 from pylorax import vernum
@@ -44,10 +46,10 @@ def get_parser():
     parser = argparse.ArgumentParser(description="Lorax Composer API Server",
                                      fromfile_prefix_chars="@")
 
-    parser.add_argument("--host", default="127.0.0.1", metavar="HOST",
-                        help="Host or IP to bind to (127.0.0.1)")
-    parser.add_argument("--port", default=4000, metavar="PORT",
-                        help="Port to bind to (4000)")
+    parser.add_argument("--socket", default="/run/weldr/api.socket", metavar="SOCKET",
+                        help="Path to the socket file to listen on")
+    parser.add_argument("--group", default="weldr", metavar="GROUP",
+                        help="Group to set ownership of the socket to")
     parser.add_argument("--log", dest="logfile", default="/var/log/lorax-composer/composer.log", metavar="LOG",
                         help="Path to logfile (/var/log/lorax-composer/composer.log)")
     parser.add_argument("--mockfiles", default="/var/tmp/bdcs-mockfiles/", metavar="MOCKFILES",
@@ -129,6 +131,29 @@ if __name__ == '__main__':
     setup_logging(opts.logfile)
     log.debug("opts=%s", opts)
 
+    # Check to make sure the group exists and get its gid
+    try:
+        gid = grp.getgrnam(opts.group).gr_gid
+    except KeyError:
+        log.error("Missing group '%s'", opts.group)
+        sys.exit(1)
+
+    # Check the socket path to make sure it exists, and that ownership and permissions are correct.
+    socket_dir = os.path.dirname(opts.socket)
+    if not os.path.exists(socket_dir):
+        # Create the directory and set permissions and ownership
+        os.makedirs(socket_dir, 0o750)
+        os.chown(socket_dir, 0, gid)
+
+    sockdir_stat = os.stat(socket_dir)
+    if sockdir_stat.st_mode & 0o007 != 0:
+        log.error("Incorrect permissions on %s, no 'other' permissions are allowed.")
+        sys.exit(1)
+
+    if sockdir_stat.st_gid != gid or sockdir_stat.st_uid != 0:
+        log.error("%s should be owned by root:%s", socket_dir, opts.group)
+        sys.exit(1)
+
     if not os.path.isdir(opts.RECIPES):
         log.warn("Creating empty recipe directory at %s", opts.RECIPES)
         os.makedirs(opts.RECIPES)
@@ -149,8 +174,16 @@ if __name__ == '__main__':
     # Import example recipes
     commit_recipe_directory(server.config["GITLOCK"].repo, "master", opts.RECIPES)
 
-    log.info("Starting %s on %s:%d with recipes from %s", VERSION, opts.host, opts.port, opts.RECIPES)
+    # Setup the Unix Domain Socket, remove old one, set ownership and permissions
+    if os.path.exists(opts.socket):
+        os.unlink(opts.socket)
+    listener = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+    listener.bind(opts.socket)
+    os.chmod(opts.socket, 0o660)
+    os.chown(opts.socket, 0, gid)
+    listener.listen(1)
 
-    http_server = WSGIServer((opts.host, opts.port), server, log=LogWrapper(server_log))
+    log.info("Starting %s on %s with recipes from %s", VERSION, opts.socket, opts.RECIPES)
+    http_server = WSGIServer(listener, server, log=LogWrapper(server_log))
     # The server writes directly to a file object, so point to our log directory
     http_server.serve_forever()