WIP

examples/auth_daemon_python/muscl-auth-daemon.service

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+[Unit]
+Description=Authorization daemon for Muscl
+
+[Service]
+Type=notify
+ExecStart=/usr/local/bin/muscl_auth_daemon.py
+
+# WatchdogSec=15
+
+User=muscl
+Group=muscl
+DynamicUser=yes
+
+; ConfigurationDirectory=muscl
+; RuntimeDirectory=muscl
+
+; # This is required to read unix user/group details.
+; PrivateUsers=false
+
+; # Needed to communicate with MySQL.
+; PrivateNetwork=false
+; PrivateIPC=false
+
+; AmbientCapabilities=
+; CapabilityBoundingSet=
+; DeviceAllow=
+; DevicePolicy=closed
+; LockPersonality=true
+; MemoryDenyWriteExecute=true
+; NoNewPrivileges=true
+; PrivateDevices=true
+; PrivateMounts=true
+; PrivateTmp=yes
+; ProcSubset=pid
+; ProtectClock=true
+; ProtectControlGroups=strict
+; ProtectHome=true
+; ProtectHostname=true
+; ProtectKernelLogs=true
+; ProtectKernelModules=true
+; ProtectKernelTunables=true
+; ProtectProc=invisible
+; ProtectSystem=strict
+; RemoveIPC=true
+; RestrictAddressFamilies=AF_UNIX AF_INET AF_INET6
+; RestrictNamespaces=true
+; RestrictRealtime=true
+; RestrictSUIDSGID=true
+; SocketBindDeny=any
+; SystemCallArchitectures=native
+; SystemCallFilter=@system-service
+; SystemCallFilter=~@privileged @resources
+; UMask=0777

examples/auth_daemon_python/muscl-auth-daemon.socket

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+[Unit]
+Description=Authorization daemon for Muscl
+WantedBy=sockets.target
+
+[Socket]
+ListenStream=/run/muscl/muscl-auth-daemon.socket
+Accept=no
+SocketMode=0660

examples/auth_daemon_python/muscl_auth_daemon.py

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+#!/usr/bin/env python3
+
+# TODO: create pool of workers to handle requests concurrently
+#       the socket should be a listener socket and each worker should accept connections from it
+#       the socket should accept requests as newline-separated JSON objects
+#       there should be a watchdog to monitor worker health and restart them if they die
+#       graceful shutdown should be implemented for the workers
+#       optional logging of requests and responses
+#       use systemd notify to signal readiness and amount of connections handled
+
+import json
+import os
+from socket import AF_UNIX, SOCK_DGRAM, SOCK_STREAM, fromfd, socket
+from multiprocessing import Pool
+
+
+def get_listener_from_systemd() -> socket:
+    listen_fds = int(os.getenv("LISTEN_FDS", "0"))
+    listen_pid = int(os.getenv("LISTEN_PID", "0"))
+    if listen_fds != 1 or listen_pid != os.getpid():
+        raise RuntimeError("No socket passed from systemd")
+    assert listen_fds == 1
+    sock = fromfd(3, AF_UNIX, SOCK_STREAM)
+    sock.setblocking(False)
+    return sock
+
+
+def get_notify_socket_from_systemd() -> socket:
+    notify_socket_path = os.getenv("NOTIFY_SOCKET")
+    if not notify_socket_path:
+        raise RuntimeError("No notify socket path found in environment")
+    sock = socket(AF_UNIX, SOCK_DGRAM)
+    sock.connect(notify_socket_path)
+    return sock
+
+
+def run_auth_daemon(sock: socket):
+    sock.listen()
+    print("Auth daemon is running and listening for connections...")
+    with Pool() as worker_pool:
+        with get_notify_socket_from_systemd() as notify_socket:
+            notify_socket.sendall(b"READY=1\n")
+        while True:
+            conn, _ = sock.accept()
+            worker_pool.apply_async(session_handler, args=(conn,))
+
+
+def session_handler(sock: socket):
+    buffer = ""
+    while True:
+        data = sock.recv(4096).decode("utf-8")
+        if not data:
+            print("Connection closed by client")
+            break
+        buffer += data
+        if buffer.endswith("\n"):
+            requests = buffer.strip().split("\n")
+            buffer = ""
+            for request in requests:
+                try:
+                    req_json = json.loads(request)
+                    username = req_json.get("username", "")
+                    groups = req_json.get("groups", [])
+                    resource_type = req_json.get("resource_type", "")
+                    resource = req_json.get("resource", "")
+                    allowed = process_request(username, groups, resource_type, resource)
+                    response = {"allowed": allowed}
+                except json.JSONDecodeError:
+                    response = {"error": "Invalid JSON"}
+                sock.sendall((json.dumps(response) + "\n").encode("utf-8"))
+
+
+def process_request(
+    username: str,
+    groups: list[str],
+    resource_type: str,
+    resource: str,
+) -> bool:
+    ...
+
+
+if __name__ == "__main__":
+    listener_socket = get_listener_from_systemd()
+    run_auth_daemon(listener_socket)