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import sys
import dns._features
if sys.platform == "win32":
from typing import Any
import dns.name
_prefer_wmi = True
import winreg # pylint: disable=import-error
# Keep pylint quiet on non-windows.
try:
_ = WindowsError # pylint: disable=used-before-assignment
except NameError:
WindowsError = Exception
if dns._features.have("wmi"):
import threading
import pythoncom # pylint: disable=import-error
import wmi # pylint: disable=import-error
_have_wmi = True
else:
_have_wmi = False
def _config_domain(domain):
# Sometimes DHCP servers add a '.' prefix to the default domain, and
# Windows just stores such values in the registry (see #687).
# Check for this and fix it.
if domain.startswith("."):
domain = domain[1:]
return dns.name.from_text(domain)
class DnsInfo:
def __init__(self):
self.domain = None
self.nameservers = []
self.search = []
if _have_wmi:
class _WMIGetter(threading.Thread):
# pylint: disable=possibly-used-before-assignment
def __init__(self):
super().__init__()
self.info = DnsInfo()
def run(self):
pythoncom.CoInitialize()
try:
system = wmi.WMI()
for interface in system.Win32_NetworkAdapterConfiguration():
if interface.IPEnabled and interface.DNSServerSearchOrder:
self.info.nameservers = list(interface.DNSServerSearchOrder)
if interface.DNSDomain:
self.info.domain = _config_domain(interface.DNSDomain)
if interface.DNSDomainSuffixSearchOrder:
self.info.search = [
_config_domain(x)
for x in interface.DNSDomainSuffixSearchOrder
]
break
finally:
pythoncom.CoUninitialize()
def get(self):
# We always run in a separate thread to avoid any issues with
# the COM threading model.
self.start()
self.join()
return self.info
else:
class _WMIGetter: # type: ignore
pass
class _RegistryGetter:
def __init__(self):
self.info = DnsInfo()
def _split(self, text):
# The windows registry has used both " " and "," as a delimiter, and while
# it is currently using "," in Windows 10 and later, updates can seemingly
# leave a space in too, e.g. "a, b". So we just convert all commas to
# spaces, and use split() in its default configuration, which splits on
# all whitespace and ignores empty strings.
return text.replace(",", " ").split()
def _config_nameservers(self, nameservers):
for ns in self._split(nameservers):
if ns not in self.info.nameservers:
self.info.nameservers.append(ns)
def _config_search(self, search):
for s in self._split(search):
s = _config_domain(s)
if s not in self.info.search:
self.info.search.append(s)
def _config_fromkey(self, key, always_try_domain):
try:
servers, _ = winreg.QueryValueEx(key, "NameServer")
except WindowsError:
servers = None
if servers:
self._config_nameservers(servers)
if servers or always_try_domain:
try:
dom, _ = winreg.QueryValueEx(key, "Domain")
if dom:
self.info.domain = _config_domain(dom)
except WindowsError:
pass
else:
try:
servers, _ = winreg.QueryValueEx(key, "DhcpNameServer")
except WindowsError:
servers = None
if servers:
self._config_nameservers(servers)
try:
dom, _ = winreg.QueryValueEx(key, "DhcpDomain")
if dom:
self.info.domain = _config_domain(dom)
except WindowsError:
pass
try:
search, _ = winreg.QueryValueEx(key, "SearchList")
except WindowsError:
search = None
if search is None:
try:
search, _ = winreg.QueryValueEx(key, "DhcpSearchList")
except WindowsError:
search = None
if search:
self._config_search(search)
def _is_nic_enabled(self, lm, guid):
# Look in the Windows Registry to determine whether the network
# interface corresponding to the given guid is enabled.
#
# (Code contributed by Paul Marks, thanks!)
#
try:
# This hard-coded location seems to be consistent, at least
# from Windows 2000 through Vista.
connection_key = winreg.OpenKey(
lm,
r"SYSTEM\CurrentControlSet\Control\Network"
r"\{4D36E972-E325-11CE-BFC1-08002BE10318}"
rf"\{guid}\Connection",
)
try:
# The PnpInstanceID points to a key inside Enum
(pnp_id, ttype) = winreg.QueryValueEx(
connection_key, "PnpInstanceID"
)
if ttype != winreg.REG_SZ:
raise ValueError # pragma: no cover
device_key = winreg.OpenKey(
lm, rf"SYSTEM\CurrentControlSet\Enum\{pnp_id}"
)
try:
# Get ConfigFlags for this device
(flags, ttype) = winreg.QueryValueEx(device_key, "ConfigFlags")
if ttype != winreg.REG_DWORD:
raise ValueError # pragma: no cover
# Based on experimentation, bit 0x1 indicates that the
# device is disabled.
#
# XXXRTH I suspect we really want to & with 0x03 so
# that CONFIGFLAGS_REMOVED devices are also ignored,
# but we're shifting to WMI as ConfigFlags is not
# supposed to be used.
return not flags & 0x1
finally:
device_key.Close()
finally:
connection_key.Close()
except Exception: # pragma: no cover
return False
def get(self):
"""Extract resolver configuration from the Windows registry."""
lm = winreg.ConnectRegistry(None, winreg.HKEY_LOCAL_MACHINE)
try:
tcp_params = winreg.OpenKey(
lm, r"SYSTEM\CurrentControlSet\Services\Tcpip\Parameters"
)
try:
self._config_fromkey(tcp_params, True)
finally:
tcp_params.Close()
interfaces = winreg.OpenKey(
lm,
r"SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\Interfaces",
)
try:
i = 0
while True:
try:
guid = winreg.EnumKey(interfaces, i)
i += 1
key = winreg.OpenKey(interfaces, guid)
try:
if not self._is_nic_enabled(lm, guid):
continue
self._config_fromkey(key, False)
finally:
key.Close()
except OSError:
break
finally:
interfaces.Close()
finally:
lm.Close()
return self.info
_getter_class: Any
if _have_wmi and _prefer_wmi:
_getter_class = _WMIGetter
else:
_getter_class = _RegistryGetter
def get_dns_info():
"""Extract resolver configuration."""
getter = _getter_class()
return getter.get()
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