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Merged
brianmay merged 1 commit into from
Oct 21, 2020
Merged

Make nat and nft rules consistent; improve rule ordering. #549

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2 changes: 1 addition & 1 deletion sshuttle/linux.py
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Original file line number Diff line number Diff line change
Expand Up @@ -74,7 +74,7 @@ def ipt_ttl(family, *args):
# with ttl 63. This makes the client side not recapture those
# connections, in case client == server.
try:
argsplus = list(args) + ['-m', 'ttl', '!', '--ttl', '63']
argsplus = list(args)
ipt(family, *argsplus)
except Fatal:
ipt(family, *args)
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38 changes: 19 additions & 19 deletions sshuttle/methods/nat.py
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Original file line number Diff line number Diff line change
Expand Up @@ -50,17 +50,24 @@ def _ipm(*args):
_ipt('-I', 'OUTPUT', '1', *args)
_ipt('-I', 'PREROUTING', '1', *args)

# Firstly we always skip all LOCAL addtrype address, i.e. avoid
# tunnelling the traffic designated to all local TCP/IP addresses.
_ipt('-A', chain, '-j', 'RETURN',
'-m', 'addrtype',
'--dst-type', 'LOCAL',
'!', '-p', 'udp')
# Skip LOCAL traffic if it's not DNS.
# This TTL hack allows the client and server to run on the
# same host. The connections the sshuttle server makes will
# have TTL set to 63.
_ipt_ttl('-A', chain, '-j', 'RETURN', '-m', 'ttl', '--ttl', '63')

# Redirect DNS traffic as requested. This includes routing traffic
# to localhost DNS servers through sshuttle.
for _, ip in [i for i in nslist if i[0] == family]:
_ipt('-A', chain, '-j', 'REDIRECT',
'--dest', '%s/32' % ip,
'-p', 'udp',
'--dport', '53',
'--to-ports', str(dnsport))

# Don't route any remaining local traffic through sshuttle.
_ipt('-A', chain, '-j', 'RETURN',
'-m', 'addrtype',
'--dst-type', 'LOCAL',
'-p', 'udp', '!', '--dport', '53')
'--dst-type', 'LOCAL')

# create new subnet entries.
for _, swidth, sexclude, snet, fport, lport \
Expand All @@ -74,16 +81,9 @@ def _ipm(*args):
'--dest', '%s/%s' % (snet, swidth),
*tcp_ports)
else:
_ipt_ttl('-A', chain, '-j', 'REDIRECT',
'--dest', '%s/%s' % (snet, swidth),
*(tcp_ports + ('--to-ports', str(port))))

for _, ip in [i for i in nslist if i[0] == family]:
_ipt_ttl('-A', chain, '-j', 'REDIRECT',
'--dest', '%s/32' % ip,
'-p', 'udp',
'--dport', '53',
'--to-ports', str(dnsport))
_ipt('-A', chain, '-j', 'REDIRECT',
'--dest', '%s/%s' % (snet, swidth),
*(tcp_ports + ('--to-ports', str(port))))

def restore_firewall(self, port, family, udp, user):
# only ipv4 supported with NAT
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32 changes: 21 additions & 11 deletions sshuttle/methods/nft.py
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Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,26 @@ def _nft(action, *args):
_nft('add rule', 'output jump %s' % chain)
_nft('add rule', 'prerouting jump %s' % chain)

# This TTL hack allows the client and server to run on the
# same host. The connections the sshuttle server makes will
# have TTL set to 63.
_nft('add rule', chain, 'ip ttl == 63 return')

# Redirect DNS traffic as requested. This includes routing traffic
# to localhost DNS servers through sshuttle.
for _, ip in [i for i in nslist if i[0] == family]:
if family == socket.AF_INET:
_nft('add rule', chain, 'ip protocol udp ip daddr %s' % ip,
'udp dport { 53 }',
('redirect to :' + str(dnsport)))
elif family == socket.AF_INET6:
_nft('add rule', chain, 'ip6 protocol udp ip6 daddr %s' % ip,
'udp dport { 53 }',
('redirect to :' + str(dnsport)))

# Don't route any remaining local traffic through sshuttle
_nft('add rule', chain, 'fib daddr type local return')

# create new subnet entries.
for _, swidth, sexclude, snet, fport, lport \
in sorted(subnets, key=subnet_weight, reverse=True):
Expand All @@ -50,19 +70,9 @@ def _nft(action, *args):
'ip daddr %s/%s' % (snet, swidth), 'return')))
else:
_nft('add rule', chain, *(tcp_ports + (
'ip daddr %s/%s' % (snet, swidth), 'ip ttl != 63',
'ip daddr %s/%s' % (snet, swidth),
('redirect to :' + str(port)))))

for _, ip in [i for i in nslist if i[0] == family]:
if family == socket.AF_INET:
_nft('add rule', chain, 'ip protocol udp ip daddr %s' % ip,
'udp dport { 53 }', 'ip ttl != 63',
('redirect to :' + str(dnsport)))
elif family == socket.AF_INET6:
_nft('add rule', chain, 'ip6 protocol udp ip6 daddr %s' % ip,
'udp dport { 53 }', 'ip ttl != 63',
('redirect to :' + str(dnsport)))

def restore_firewall(self, port, family, udp, user):
if udp:
raise Exception("UDP not supported by nft method_name")
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22 changes: 10 additions & 12 deletions tests/client/test_methods_nat.py
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Expand Up @@ -123,12 +123,8 @@ def test_setup_firewall(mock_ipt_chain_exists, mock_ipt_ttl, mock_ipt):
call(AF_INET, 'nat', 'sshuttle-1025')
]
assert mock_ipt_ttl.mock_calls == [
call(AF_INET, 'nat', '-A', 'sshuttle-1025', '-j', 'REDIRECT',
'--dest', u'1.2.3.0/24', '-p', 'tcp', '--dport', '8000:9000',
'--to-ports', '1025'),
call(AF_INET, 'nat', '-A', 'sshuttle-1025', '-j', 'REDIRECT',
'--dest', u'1.2.3.33/32', '-p', 'udp',
'--dport', '53', '--to-ports', '1027')
call(AF_INET, 'nat', '-A', 'sshuttle-1025', '-j', 'RETURN',
'-m', 'ttl', '--ttl', '63')
]
assert mock_ipt.mock_calls == [
call(AF_INET, 'nat', '-D', 'OUTPUT', '-j', 'sshuttle-1025'),
Expand All @@ -139,14 +135,16 @@ def test_setup_firewall(mock_ipt_chain_exists, mock_ipt_ttl, mock_ipt):
call(AF_INET, 'nat', '-F', 'sshuttle-1025'),
call(AF_INET, 'nat', '-I', 'OUTPUT', '1', '-j', 'sshuttle-1025'),
call(AF_INET, 'nat', '-I', 'PREROUTING', '1', '-j', 'sshuttle-1025'),
call(AF_INET, 'nat', '-A', 'sshuttle-1025', '-j', 'REDIRECT',
'--dest', u'1.2.3.33/32', '-p', 'udp',
'--dport', '53', '--to-ports', '1027'),
call(AF_INET, 'nat', '-A', 'sshuttle-1025', '-j', 'RETURN',
'-m', 'addrtype', '--dst-type', 'LOCAL',
'!', '-p', 'udp'),
call(AF_INET, 'nat', '-A', 'sshuttle-1025', '-j', 'RETURN',
'-m', 'addrtype', '--dst-type', 'LOCAL',
'-p', 'udp', '!', '--dport', '53'),
'-m', 'addrtype', '--dst-type', 'LOCAL'),
call(AF_INET, 'nat', '-A', 'sshuttle-1025', '-j', 'RETURN',
'--dest', u'1.2.3.66/32', '-p', 'tcp', '--dport', '8080:8080')
'--dest', u'1.2.3.66/32', '-p', 'tcp', '--dport', '8080:8080'),
call(AF_INET, 'nat', '-A', 'sshuttle-1025', '-j', 'REDIRECT',
'--dest', u'1.2.3.0/24', '-p', 'tcp', '--dport', '8000:9000',
'--to-ports', '1025')
]
mock_ipt_chain_exists.reset_mock()
mock_ipt_ttl.reset_mock()
Expand Down