[ddns.git] / src / ddns / system.py

#!/usr/bin/python
###############################################################################
#                                                                             #
# ddns - A dynamic DNS client for IPFire                                      #
# Copyright (C) 2012 IPFire development team                                  #
#                                                                             #
# This program is free software: you can redistribute it and/or modify        #
# it under the terms of the GNU General Public License as published by        #
# the Free Software Foundation, either version 3 of the License, or           #
# (at your option) any later version.                                         #
#                                                                             #
# This program is distributed in the hope that it will be useful,             #
# but WITHOUT ANY WARRANTY; without even the implied warranty of              #
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the               #
# GNU General Public License for more details.                                #
#                                                                             #
# You should have received a copy of the GNU General Public License           #
# along with this program.  If not, see <http://www.gnu.org/licenses/>.       #
#                                                                             #
###############################################################################

import base64
import re
import socket
import urllib
import urllib2

from __version__ import CLIENT_VERSION
from .errors import *
from i18n import _

# Initialize the logger.
import logging
logger = logging.getLogger("ddns.system")
logger.propagate = 1

class DDNSSystem(object):
	"""
		The DDNSSystem class adds a layer of abstraction
		between the ddns software and the system.
	"""

	# The default useragent.
	USER_AGENT = "IPFireDDNSUpdater/%s" % CLIENT_VERSION

	def __init__(self, core):
		# Connection to the core of the program.
		self.core = core

		# Address cache.
		self.__addresses = {}

		# Find out on which distribution we are running.
		self.distro = self._get_distro_identifier()
		logger.debug(_("Running on distribution: %s") % self.distro)

	@property
	def proxy(self):
		proxy = self.core.settings.get("proxy")

		# Strip http:// at the beginning.
		if proxy and proxy.startswith("http://"):
			proxy = proxy[7:]

		return proxy

	def get_local_ip_address(self, proto):
		# Legacy code for IPFire 2.
		if self.distro == "ipfire-2" and proto == "ipv4":
			try:
				with open("/var/ipfire/red/local-ipaddress") as f:
					return f.readline()

			except IOError, e:
				# File not found
				if e.errno == 2:
					return

				raise

		# XXX TODO
		raise NotImplementedError

	def _guess_external_ip_address(self, url, timeout=10):
		"""
			Sends a request to an external web server
			to determine the current default IP address.
		"""
		try:
			response = self.send_request(url, timeout=timeout)

		# If the server could not be reached, we will return nothing.
		except DDNSNetworkError:
			return

		if not response.code == 200:
			return

		match = re.search(r"^Your IP address is: (.*)$", response.read())
		if match is None:
			return

		return match.group(1)

	def guess_external_ip_address(self, family, **kwargs):
		if family == "ipv6":
			url = "http://checkip6.dns.lightningwirelabs.com"
		elif family == "ipv4":
			url = "http://checkip4.dns.lightningwirelabs.com"
		else:
			raise ValueError("unknown address family")

		return self._guess_external_ip_address(url, **kwargs)

	def send_request(self, url, method="GET", data=None, username=None, password=None, timeout=30):
		assert method in ("GET", "POST")

		# Add all arguments in the data dict to the URL and escape them properly.
		if method == "GET" and data:
			query_args = self._format_query_args(data)
			data = None

			if "?" in url:
				url = "%s&%s" % (url, query_args)
			else:
				url = "%s?%s" % (url, query_args)

		logger.debug("Sending request (%s): %s" % (method, url))
		if data:
			logger.debug("  data: %s" % data)

		req = urllib2.Request(url, data=data)

		if username and password:
			basic_auth_header = self._make_basic_auth_header(username, password)
			req.add_header("Authorization", "Basic %s" % basic_auth_header)

		# Set the user agent.
		req.add_header("User-Agent", self.USER_AGENT)

		# All requests should not be cached anywhere.
		req.add_header("Pragma", "no-cache")

		# Set the upstream proxy if needed.
		if self.proxy:
			logger.debug("Using proxy: %s" % self.proxy)

			# Configure the proxy for this request.
			req.set_proxy(self.proxy, "http")

		assert req.get_method() == method

		logger.debug(_("Request header:"))
		for k, v in req.headers.items():
			logger.debug("  %s: %s" % (k, v))

		try:
			resp = urllib2.urlopen(req, timeout=timeout)

			# Log response header.
			logger.debug(_("Response header (Status Code %s):") % resp.code)
			for k, v in resp.info().items():
				logger.debug("  %s: %s" % (k, v))

			# Return the entire response object.
			return resp

		except urllib2.HTTPError, e:
			# Log response header.
			logger.debug(_("Response header (Status Code %s):") % e.code)
			for k, v in e.hdrs.items():
				logger.debug("  %s: %s" % (k, v))

			# 400 - Bad request
			if e.code == 400:
				raise DDNSRequestError(e.reason)

			# 401 - Authorization Required
			# 403 - Forbidden
			elif e.code in (401, 403):
				raise DDNSAuthenticationError(e.reason)

			# 500 - Internal Server Error
			elif e.code == 500:
				raise DDNSInternalServerError(e.reason)

			# 503 - Service Unavailable
			elif e.code == 503:
				raise DDNSServiceUnavailableError(e.reason)

			# Raise all other unhandled exceptions.
			raise

		except urllib2.URLError, e:
			if e.reason:
				# Name or service not known
				if e.reason.errno == -2:
					raise DDNSResolveError

				# Network Unreachable (e.g. no IPv6 access)
				if e.reason.errno == 101:
					raise DDNSNetworkUnreachableError

				# Connection Refused
				elif e.reason.errno == 111:
					raise DDNSConnectionRefusedError

			# Raise all other unhandled exceptions.
			raise

		except socket.timeout, e:
			logger.debug(_("Connection timeout"))

			raise DDNSConnectionTimeoutError

	def _format_query_args(self, data):
		args = []

		for k, v in data.items():
			arg = "%s=%s" % (k, urllib.quote(v))
			args.append(arg)

		return "&".join(args)

	def _make_basic_auth_header(self, username, password):
		authstring = "%s:%s" % (username, password)

		# Encode authorization data in base64.
		authstring = base64.encodestring(authstring)

		# Remove any newline characters.
		authstring = authstring.replace("\n", "")

		return authstring

	def get_address(self, proto):
		"""
			Returns the current IP address for
			the given IP protocol.
		"""
		try:
			return self.__addresses[proto]

		# IP is currently unknown and needs to be retrieved.
		except KeyError:
			self.__addresses[proto] = address = \
				self._get_address(proto)

			return address

	def _get_address(self, proto):
		assert proto in ("ipv6", "ipv4")

		# IPFire 2 does not support IPv6.
		if self.distro == "ipfire-2" and proto == "ipv6":
			return

		# Check if the external IP address should be guessed from
		# a remote server.
		guess_ip = self.core.settings.get("guess_external_ip", "true")
		guess_ip = guess_ip in ("true", "yes", "1")

		# If the external IP address should be used, we just do that.
		if guess_ip:
			return self.guess_external_ip_address(proto)

		# Get the local IP address.
		local_ip_address = self.get_local_ip_address(proto)

		# If the local IP address is not usable, we must guess
		# the correct IP address...
		if not self._is_usable_ip_address(proto, local_ip_address):
			local_ip_address = self.guess_external_ip_address(proto)

		return local_ip_address

	def _is_usable_ip_address(self, proto, address):
		"""
			Returns True is the local IP address is usable
			for dynamic DNS (i.e. is not a RFC1918 address or similar).
		"""
		if proto == "ipv4":
			# This is not the most perfect solution to match
			# these addresses, but instead of pulling in an entire
			# library to handle the IP addresses better, we match
			# with regular expressions instead.
			matches = (
				# RFC1918 address space
				r"^10\.\d+\.\d+\.\d+$",
				r"^192\.168\.\d+\.\d+$",
				r"^172\.(1[6-9]|2[0-9]|31)\.\d+\.\d+$",

				# Dual Stack Lite address space
				r"^100\.(6[4-9]|[7-9][0-9]|1[01][0-9]|12[0-7])\.\d+\.\d+$",
			)

			for match in matches:
				m = re.match(match, address)
				if m is None:
					continue

				# Found a match. IP address is not usable.
				return False

		# In all other cases, return OK.
		return True

	def resolve(self, hostname, proto=None):
		addresses = []

		if proto is None:
			family = 0
		elif proto == "ipv6":
			family = socket.AF_INET6
		elif proto == "ipv4":
			family = socket.AF_INET
		else:
			raise ValueError("Protocol not supported: %s" % proto)

		# Resolve the host address.
		try:
			response = socket.getaddrinfo(hostname, None, family)
		except socket.gaierror, e:
			# Name or service not known
			if e.errno == -2:
				return []

			# Temporary failure in name resolution
			elif e.errno == -3:
				raise DDNSResolveError(hostname)

			# No record for requested family available (e.g. no AAAA)
			elif e.errno == -5:
				return []

			raise

		# Handle responses.
		for family, socktype, proto, canonname, sockaddr in response:
			# IPv6
			if family == socket.AF_INET6:
				address, port, flow_info, scope_id = sockaddr

				# Only use the global scope.
				if not scope_id == 0:
					continue

			# IPv4
			elif family == socket.AF_INET:
				address, port = sockaddr

			# Ignore everything else...
			else:
				continue

			# Add to repsonse list if not already in there.
			if not address in addresses:
				addresses.append(address)

		return addresses

	def _get_distro_identifier(self):
		"""
			Returns a unique identifier for the distribution
			we are running on.
		"""
		os_release = self.__parse_os_release()
		if os_release:
			return os_release

		system_release = self.__parse_system_release()
		if system_release:
			return system_release

		# If nothing else could be found, we return
		# just "unknown".
		return "unknown"

	def __parse_os_release(self):
		"""
			Tries to parse /etc/os-release and
			returns a unique distribution identifier
			if the file exists.
		"""
		try:
			f = open("/etc/os-release", "r")
		except IOError, e:
			# File not found
			if e.errno == 2:
				return

			raise

		os_release = {}
		with f:
			for line in f.readlines():
				m = re.match(r"^([A-Z\_]+)=(.*)$", line)
				if m is None:
					continue

				os_release[m.group(1)] = m.group(2)

		try:
			return "%(ID)s-%(VERSION_ID)s" % os_release
		except KeyError:
			return

	def __parse_system_release(self):
		"""
			Tries to parse /etc/system-release and
			returns a unique distribution identifier
			if the file exists.
		"""
		try:
			f = open("/etc/system-release", "r")
		except IOError, e:
			# File not found
			if e.errno == 2:
				return

			raise

		with f:
			# Read first line
			line = f.readline()

			# Check for IPFire systems
			m = re.match(r"^IPFire (\d).(\d+)", line)
			if m:
				return "ipfire-%s" % m.group(1)
Commit	Line	Data
f22ab085	1	#!/usr/bin/python
3fdcb9d1 MT	2	###############################################################################
	3	# #
	4	# ddns - A dynamic DNS client for IPFire #
	5	# Copyright (C) 2012 IPFire development team #
	6	# #
	7	# This program is free software: you can redistribute it and/or modify #
	8	# it under the terms of the GNU General Public License as published by #
	9	# the Free Software Foundation, either version 3 of the License, or #
	10	# (at your option) any later version. #
	11	# #
	12	# This program is distributed in the hope that it will be useful, #
	13	# but WITHOUT ANY WARRANTY; without even the implied warranty of #
	14	# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the #
	15	# GNU General Public License for more details. #
	16	# #
	17	# You should have received a copy of the GNU General Public License #
	18	# along with this program. If not, see <http://www.gnu.org/licenses/>. #
	19	# #
	20	###############################################################################
f22ab085	21
d4c5c0d5	22	import base64
f22ab085	23	import re
6cecd141	24	import socket
adb124d0	25	import urllib
f22ab085 MT	26	import urllib2
	27
	28	from __version__ import CLIENT_VERSION
7a909224	29	from .errors import *
f22ab085 MT	30	from i18n import _
	31
	32	# Initialize the logger.
	33	import logging
	34	logger = logging.getLogger("ddns.system")
	35	logger.propagate = 1
	36
	37	class DDNSSystem(object):
	38	"""
	39	The DDNSSystem class adds a layer of abstraction
	40	between the ddns software and the system.
	41	"""
	42
	43	# The default useragent.
	44	USER_AGENT = "IPFireDDNSUpdater/%s" % CLIENT_VERSION
	45
	46	def __init__(self, core):
	47	# Connection to the core of the program.
	48	self.core = core
	49
91a8ff83 MT	50	# Address cache.
	51	self.__addresses = {}
	52
2780b6bb MT	53	# Find out on which distribution we are running.
	54	self.distro = self._get_distro_identifier()
	55	logger.debug(_("Running on distribution: %s") % self.distro)
	56
f22ab085 MT	57	@property
	58	def proxy(self):
	59	proxy = self.core.settings.get("proxy")
	60
	61	# Strip http:// at the beginning.
fd898828	62	if proxy and proxy.startswith("http://"):
f22ab085 MT	63	proxy = proxy[7:]
	64
	65	return proxy
	66
eba7100b MT	67	def get_local_ip_address(self, proto):
	68	# Legacy code for IPFire 2.
	69	if self.distro == "ipfire-2" and proto == "ipv4":
7f75b957 MT	70	try:
	71	with open("/var/ipfire/red/local-ipaddress") as f:
	72	return f.readline()
	73
	74	except IOError, e:
	75	# File not found
	76	if e.errno == 2:
	77	return
	78
	79	raise
	80
eba7100b MT	81	# XXX TODO
eba7100b MT	82	raise NotImplementedError
7f75b957	83
46c23a71	84	def _guess_external_ip_address(self, url, timeout=10):
30270391 MT	85	"""
	86	Sends a request to an external web server
	87	to determine the current default IP address.
	88	"""
7a909224	89	try:
46c23a71	90	response = self.send_request(url, timeout=timeout)
7a909224 MT	91
	92	# If the server could not be reached, we will return nothing.
	93	except DDNSNetworkError:
	94	return
30270391 MT	95
	96	if not response.code == 200:
	97	return
	98
	99	match = re.search(r"^Your IP address is: (.*)$", response.read())
	100	if match is None:
	101	return
	102
	103	return match.group(1)
	104
022003bc MT	105	def guess_external_ip_address(self, family, **kwargs):
	106	if family == "ipv6":
	107	url = "http://checkip6.dns.lightningwirelabs.com"
	108	elif family == "ipv4":
	109	url = "http://checkip4.dns.lightningwirelabs.com"
	110	else:
	111	raise ValueError("unknown address family")
f22ab085	112
022003bc	113	return self._guess_external_ip_address(url, **kwargs)
f22ab085	114
d4c5c0d5	115	def send_request(self, url, method="GET", data=None, username=None, password=None, timeout=30):
adb124d0 MT	116	assert method in ("GET", "POST")
	117
	118	# Add all arguments in the data dict to the URL and escape them properly.
	119	if method == "GET" and data:
	120	query_args = self._format_query_args(data)
	121	data = None
	122
4c1b0d25 SS	123	if "?" in url:
	124	url = "%s&%s" % (url, query_args)
	125	else:
	126	url = "%s?%s" % (url, query_args)
adb124d0 MT	127
adb124d0 MT	128	logger.debug("Sending request (%s): %s" % (method, url))
f22ab085 MT	129	if data:
	130	logger.debug(" data: %s" % data)
	131
	132	req = urllib2.Request(url, data=data)
	133
d4c5c0d5 SS	134	if username and password:
d4c5c0d5 SS	135	basic_auth_header = self._make_basic_auth_header(username, password)
d4c5c0d5 SS	136	req.add_header("Authorization", "Basic %s" % basic_auth_header)
d4c5c0d5 SS	137
f22ab085 MT	138	# Set the user agent.
	139	req.add_header("User-Agent", self.USER_AGENT)
	140
	141	# All requests should not be cached anywhere.
	142	req.add_header("Pragma", "no-cache")
	143
	144	# Set the upstream proxy if needed.
	145	if self.proxy:
	146	logger.debug("Using proxy: %s" % self.proxy)
	147
	148	# Configure the proxy for this request.
	149	req.set_proxy(self.proxy, "http")
	150
adb124d0 MT	151	assert req.get_method() == method
adb124d0 MT	152
f22ab085 MT	153	logger.debug(_("Request header:"))
	154	for k, v in req.headers.items():
	155	logger.debug(" %s: %s" % (k, v))
	156
	157	try:
7a909224	158	resp = urllib2.urlopen(req, timeout=timeout)
f22ab085 MT	159
f22ab085 MT	160	# Log response header.
09c496c5	161	logger.debug(_("Response header (Status Code %s):") % resp.code)
f22ab085 MT	162	for k, v in resp.info().items():
	163	logger.debug(" %s: %s" % (k, v))
	164
	165	# Return the entire response object.
	166	return resp
	167
7a909224	168	except urllib2.HTTPError, e:
3bc79bff MT	169	# Log response header.
	170	logger.debug(_("Response header (Status Code %s):") % e.code)
	171	for k, v in e.hdrs.items():
	172	logger.debug(" %s: %s" % (k, v))
	173
536e87d1 MT	174	# 400 - Bad request
	175	if e.code == 400:
	176	raise DDNSRequestError(e.reason)
	177
	178	# 401 - Authorization Required
	179	# 403 - Forbidden
	180	elif e.code in (401, 403):
	181	raise DDNSAuthenticationError(e.reason)
	182
	183	# 500 - Internal Server Error
	184	elif e.code == 500:
	185	raise DDNSInternalServerError(e.reason)
	186
7a909224	187	# 503 - Service Unavailable
536e87d1 MT	188	elif e.code == 503:
536e87d1 MT	189	raise DDNSServiceUnavailableError(e.reason)
7a909224 MT	190
	191	# Raise all other unhandled exceptions.
	192	raise
	193
f22ab085	194	except urllib2.URLError, e:
7a909224	195	if e.reason:
694d8485 MT	196	# Name or service not known
	197	if e.reason.errno == -2:
	198	raise DDNSResolveError
	199
7a909224 MT	200	# Network Unreachable (e.g. no IPv6 access)
	201	if e.reason.errno == 101:
	202	raise DDNSNetworkUnreachableError
a96ab398 MT	203
a96ab398 MT	204	# Connection Refused
7a909224 MT	205	elif e.reason.errno == 111:
	206	raise DDNSConnectionRefusedError
	207
	208	# Raise all other unhandled exceptions.
f22ab085 MT	209	raise
f22ab085 MT	210
7a909224 MT	211	except socket.timeout, e:
	212	logger.debug(_("Connection timeout"))
	213
	214	raise DDNSConnectionTimeoutError
	215
adb124d0 MT	216	def _format_query_args(self, data):
	217	args = []
	218
	219	for k, v in data.items():
	220	arg = "%s=%s" % (k, urllib.quote(v))
	221	args.append(arg)
	222
	223	return "&".join(args)
	224
d4c5c0d5 SS	225	def _make_basic_auth_header(self, username, password):
	226	authstring = "%s:%s" % (username, password)
	227
	228	# Encode authorization data in base64.
	229	authstring = base64.encodestring(authstring)
	230
	231	# Remove any newline characters.
	232	authstring = authstring.replace("\n", "")
	233
	234	return authstring
	235
f22ab085	236	def get_address(self, proto):
91a8ff83 MT	237	"""
	238	Returns the current IP address for
	239	the given IP protocol.
	240	"""
	241	try:
	242	return self.__addresses[proto]
	243
	244	# IP is currently unknown and needs to be retrieved.
	245	except KeyError:
	246	self.__addresses[proto] = address = \
	247	self._get_address(proto)
	248
	249	return address
	250
	251	def _get_address(self, proto):
f22ab085 MT	252	assert proto in ("ipv6", "ipv4")
f22ab085 MT	253
afca6b38 MT	254	# IPFire 2 does not support IPv6.
	255	if self.distro == "ipfire-2" and proto == "ipv6":
	256	return
	257
30270391 MT	258	# Check if the external IP address should be guessed from
	259	# a remote server.
	260	guess_ip = self.core.settings.get("guess_external_ip", "true")
3a061b71	261	guess_ip = guess_ip in ("true", "yes", "1")
30270391	262
3a061b71 MT	263	# If the external IP address should be used, we just do that.
3a061b71 MT	264	if guess_ip:
022003bc	265	return self.guess_external_ip_address(proto)
f22ab085	266
3a061b71 MT	267	# Get the local IP address.
	268	local_ip_address = self.get_local_ip_address(proto)
	269
	270	# If the local IP address is not usable, we must guess
	271	# the correct IP address...
	272	if not self._is_usable_ip_address(proto, local_ip_address):
	273	local_ip_address = self.guess_external_ip_address(proto)
	274
	275	return local_ip_address
	276
	277	def _is_usable_ip_address(self, proto, address):
	278	"""
	279	Returns True is the local IP address is usable
	280	for dynamic DNS (i.e. is not a RFC1918 address or similar).
	281	"""
	282	if proto == "ipv4":
	283	# This is not the most perfect solution to match
	284	# these addresses, but instead of pulling in an entire
	285	# library to handle the IP addresses better, we match
	286	# with regular expressions instead.
	287	matches = (
	288	# RFC1918 address space
	289	r"^10\.\d+\.\d+\.\d+$",
	290	r"^192\.168\.\d+\.\d+$",
	291	r"^172\.(1[6-9]\|2[0-9]\|31)\.\d+\.\d+$",
	292
	293	# Dual Stack Lite address space
580f98e8	294	r"^100\.(6[4-9]\|[7-9][0-9]\|1[01][0-9]\|12[0-7])\.\d+\.\d+$",
3a061b71 MT	295	)
	296
	297	for match in matches:
	298	m = re.match(match, address)
	299	if m is None:
	300	continue
	301
	302	# Found a match. IP address is not usable.
	303	return False
	304
	305	# In all other cases, return OK.
	306	return True
6cecd141 MT	307
	308	def resolve(self, hostname, proto=None):
	309	addresses = []
	310
	311	if proto is None:
	312	family = 0
	313	elif proto == "ipv6":
	314	family = socket.AF_INET6
	315	elif proto == "ipv4":
	316	family = socket.AF_INET
	317	else:
	318	raise ValueError("Protocol not supported: %s" % proto)
	319
	320	# Resolve the host address.
73f2bc0b MT	321	try:
	322	response = socket.getaddrinfo(hostname, None, family)
	323	except socket.gaierror, e:
	324	# Name or service not known
	325	if e.errno == -2:
	326	return []
	327
694d8485 MT	328	# Temporary failure in name resolution
	329	elif e.errno == -3:
	330	raise DDNSResolveError(hostname)
	331
aac65fab MT	332	# No record for requested family available (e.g. no AAAA)
	333	elif e.errno == -5:
	334	return []
	335
73f2bc0b	336	raise
6cecd141 MT	337
	338	# Handle responses.
	339	for family, socktype, proto, canonname, sockaddr in response:
	340	# IPv6
	341	if family == socket.AF_INET6:
	342	address, port, flow_info, scope_id = sockaddr
	343
	344	# Only use the global scope.
	345	if not scope_id == 0:
	346	continue
	347
	348	# IPv4
	349	elif family == socket.AF_INET:
	350	address, port = sockaddr
	351
	352	# Ignore everything else...
	353	else:
	354	continue
	355
	356	# Add to repsonse list if not already in there.
	357	if not address in addresses:
	358	addresses.append(address)
	359
	360	return addresses
2780b6bb MT	361
	362	def _get_distro_identifier(self):
	363	"""
	364	Returns a unique identifier for the distribution
	365	we are running on.
	366	"""
	367	os_release = self.__parse_os_release()
	368	if os_release:
	369	return os_release
	370
	371	system_release = self.__parse_system_release()
	372	if system_release:
	373	return system_release
	374
	375	# If nothing else could be found, we return
	376	# just "unknown".
	377	return "unknown"
	378
	379	def __parse_os_release(self):
	380	"""
	381	Tries to parse /etc/os-release and
	382	returns a unique distribution identifier
	383	if the file exists.
	384	"""
	385	try:
	386	f = open("/etc/os-release", "r")
	387	except IOError, e:
	388	# File not found
	389	if e.errno == 2:
	390	return
	391
	392	raise
	393
	394	os_release = {}
	395	with f:
	396	for line in f.readlines():
	397	m = re.match(r"^([A-Z\_]+)=(.*)$", line)
	398	if m is None:
	399	continue
	400
	401	os_release[m.group(1)] = m.group(2)
	402
	403	try:
	404	return "%(ID)s-%(VERSION_ID)s" % os_release
	405	except KeyError:
	406	return
	407
	408	def __parse_system_release(self):
	409	"""
	410	Tries to parse /etc/system-release and
	411	returns a unique distribution identifier
	412	if the file exists.
	413	"""
	414	try:
	415	f = open("/etc/system-release", "r")
	416	except IOError, e:
	417	# File not found
	418	if e.errno == 2:
	419	return
	420
	421	raise
	422
	423	with f:
	424	# Read first line
425	line = f.readline()
426
427	# Check for IPFire systems
428	m = re.match(r"^IPFire (\d).(\d+)", line)
429	if m:
430	return "ipfire-%s" % m.group(1)