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resolved: don't query domain-limited DNS servers for other domains (#3621)

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DNS servers which have route-only domains should only be used for
the specified domains. Routing queries about other domains there is a privacy
violation, prone to fail (as that DNS server was not meant to be used for other
domains), and puts unnecessary load onto that server.

Introduce a new helper function dns_server_limited_domains() that checks if the
DNS server should only be used for some selected domains, i. e. has some
route-only domains without "~.". Use that when determining whether to query it
in the scope, and when writing resolv.conf.

Extend the test_route_only_dns() case to ensure that the DNS server limited to
~company does not appear in resolv.conf. Add test_route_only_dns_all_domains()
to ensure that a server that also has ~. does appear in resolv.conf as global
name server. These reproduce #3420.

Add a new test_resolved_domain_restricted_dns() test case that verifies that
domain-limited DNS servers are only being used for those domains. This
reproduces #3421.

Clarify what a "routing domain" is in the manpage.

Fixes #3420
Fixes #3421
This commit is contained in:
Martin Pitt
2016-09-30 09:30:08 +02:00
committed by Zbigniew Jędrzejewski-Szmek
parent a86b76753d
commit b9fe94cad9
6 changed files with 152 additions and 3 deletions
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110
test/networkd-test.py
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@ -250,6 +250,38 @@ Domains= ~company''')
self.assertNotRegex(contents, 'search.*company')
# our global server should appear
self.assertIn('nameserver 192.168.5.1\n', contents)
# should not have domain-restricted server as global server
self.assertNotIn('nameserver 192.168.42.1\n', contents)
def test_route_only_dns_all_domains(self):
with open('/run/systemd/network/myvpn.netdev', 'w') as f:
f.write('''[NetDev]
Name=dummy0
Kind=dummy
MACAddress=12:34:56:78:9a:bc''')
with open('/run/systemd/network/myvpn.network', 'w') as f:
f.write('''[Match]
Name=dummy0
[Network]
Address=192.168.42.100
DNS=192.168.42.1
Domains= ~company ~.''')
self.addCleanup(os.remove, '/run/systemd/network/myvpn.netdev')
self.addCleanup(os.remove, '/run/systemd/network/myvpn.network')
self.do_test(coldplug=True, ipv6=False,
extra_opts='IPv6AcceptRouterAdvertisements=False')
with open(RESOLV_CONF) as f:
contents = f.read()
# ~company is not a search domain, only a routing domain
self.assertNotRegex(contents, 'search.*company')
# our global server should appear
self.assertIn('nameserver 192.168.5.1\n', contents)
# should have company server as global server due to ~.
self.assertIn('nameserver 192.168.42.1\n', contents)
@unittest.skipUnless(have_dnsmasq, 'dnsmasq not installed')
@ -260,7 +292,7 @@ class DnsmasqClientTest(ClientTestBase, unittest.TestCase):
super().setUp()
self.dnsmasq = None
def create_iface(self, ipv6=False):
def create_iface(self, ipv6=False, dnsmasq_opts=None):
'''Create test interface with DHCP server behind it'''
# add veth pair
@ -281,6 +313,8 @@ class DnsmasqClientTest(ClientTestBase, unittest.TestCase):
extra_opts = ['--enable-ra', '--dhcp-range=2600::10,2600::20']
else:
extra_opts = []
if dnsmasq_opts:
extra_opts += dnsmasq_opts
self.dnsmasq = subprocess.Popen(
['dnsmasq', '--keep-in-foreground', '--log-queries',
'--log-facility=' + self.dnsmasq_log, '--conf-file=/dev/null',
@ -305,6 +339,80 @@ class DnsmasqClientTest(ClientTestBase, unittest.TestCase):
with open(self.dnsmasq_log) as f:
sys.stdout.write('\n\n---- dnsmasq log ----\n%s\n------\n\n' % f.read())
def test_resolved_domain_restricted_dns(self):
'''resolved: domain-restricted DNS servers'''
# create interface for generic connections; this will map all DNS names
# to 192.168.42.1
self.create_iface(dnsmasq_opts=['--address=/#/192.168.42.1'])
self.writeConfig('/run/systemd/network/general.network', '''\
[Match]
Name=%s
[Network]
DHCP=ipv4
IPv6AcceptRA=False''' % self.iface)
# create second device/dnsmasq for a .company/.lab VPN interface
# static IPs for simplicity
subprocess.check_call(['ip', 'link', 'add', 'name', 'testvpnclient', 'type',
'veth', 'peer', 'name', 'testvpnrouter'])
self.addCleanup(subprocess.call, ['ip', 'link', 'del', 'dev', 'testvpnrouter'])
subprocess.check_call(['ip', 'a', 'flush', 'dev', 'testvpnrouter'])
subprocess.check_call(['ip', 'a', 'add', '10.241.3.1/24', 'dev', 'testvpnrouter'])
subprocess.check_call(['ip', 'link', 'set', 'testvpnrouter', 'up'])
vpn_dnsmasq_log = os.path.join(self.workdir, 'dnsmasq-vpn.log')
vpn_dnsmasq = subprocess.Popen(
['dnsmasq', '--keep-in-foreground', '--log-queries',
'--log-facility=' + vpn_dnsmasq_log, '--conf-file=/dev/null',
'--dhcp-leasefile=/dev/null', '--bind-interfaces',
'--interface=testvpnrouter', '--except-interface=lo',
'--address=/math.lab/10.241.3.3', '--address=/cantina.company/10.241.4.4'])
self.addCleanup(vpn_dnsmasq.wait)
self.addCleanup(vpn_dnsmasq.kill)
self.writeConfig('/run/systemd/network/vpn.network', '''\
[Match]
Name=testvpnclient
[Network]
IPv6AcceptRA=False
Address=10.241.3.2/24
DNS=10.241.3.1
Domains= ~company ~lab''')
subprocess.check_call(['systemctl', 'start', 'systemd-networkd'])
subprocess.check_call([self.networkd_wait_online, '--interface', self.iface,
'--interface=testvpnclient', '--timeout=20'])
# ensure we start fresh with every test
subprocess.check_call(['systemctl', 'restart', 'systemd-resolved'])
# test vpnclient specific domains; these should *not* be answered by
# the general DNS
out = subprocess.check_output(['systemd-resolve', 'math.lab'])
self.assertIn(b'math.lab: 10.241.3.3', out)
out = subprocess.check_output(['systemd-resolve', 'kettle.cantina.company'])
self.assertIn(b'kettle.cantina.company: 10.241.4.4', out)
# test general domains
out = subprocess.check_output(['systemd-resolve', 'megasearch.net'])
self.assertIn(b'megasearch.net: 192.168.42.1', out)
with open(self.dnsmasq_log) as f:
general_log = f.read()
with open(vpn_dnsmasq_log) as f:
vpn_log = f.read()
# VPN domains should only be sent to VPN DNS
self.assertRegex(vpn_log, 'query.*math.lab')
self.assertRegex(vpn_log, 'query.*cantina.company')
self.assertNotIn('lab', general_log)
self.assertNotIn('company', general_log)
# general domains should not be sent to the VPN DNS
self.assertRegex(general_log, 'query.*megasearch.net')
self.assertNotIn('megasearch.net', vpn_log)
class NetworkdClientTest(ClientTestBase, unittest.TestCase):
'''Test networkd client against networkd server'''