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Remove ttl hack & require -r option.

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Previously, it was possible to run sshuttle locally without using ssh
and connecting to a remote server. In this configuration, traffic was
redirected to the sshuttle server running on the localhost. However,
the firewall needed to distinguish between traffic leaving the
sshuttle server and traffic that originated from the machine that
still needed to be routed through the sshuttle server. The TTL of the
packets leaving the sshuttle server were manipulated to indicate to
the firewall what should happen. The TTL was adjusted for all packets
leaving the sshuttle server (even if it wasn't necessary because the
server and client were running on different machines).

Changing the TTL caused trouble and some machines, and
the --ttl option was added as a workaround to change how the TTL was
set for traffic leaving sshuttle. All of this added complexity to the
code for a feature (running the server on localhost) that is likely
only used for testing and rarely used by others.

This commit updates the associated documentation, but doesn't fully
fix the ipfw method since I am unable to test that.

This change will also make sshuttle fail to work if -r is used to
specify a localhost. Pull request #610 partially addresses that issue.

For example, see: #240, #490, #660, #606.
This commit is contained in:
Scott Kuhl
2021-05-31 23:33:55 -04:00
parent 6ae0b51c61
commit bc065e368d
20 changed files with 66 additions and 160 deletions
Download Patch File Download Diff File Expand all files Collapse all files

26
tests/client/test_methods_nat.py
View File

@ -85,15 +85,13 @@ def test_firewall_command():
@patch('sshuttle.methods.nat.ipt')
@patch('sshuttle.methods.nat.ipt_ttl')
@patch('sshuttle.methods.nat.ipt_chain_exists')
def test_setup_firewall(mock_ipt_chain_exists, mock_ipt_ttl, mock_ipt):
def test_setup_firewall(mock_ipt_chain_exists, mock_ipt):
mock_ipt_chain_exists.return_value = True
method = get_method('nat')
assert method.name == 'nat'
assert mock_ipt_chain_exists.mock_calls == []
assert mock_ipt_ttl.mock_calls == []
assert mock_ipt.mock_calls == []
method.setup_firewall(
1024, 1026,
@ -103,15 +101,11 @@ def test_setup_firewall(mock_ipt_chain_exists, mock_ipt_ttl, mock_ipt):
(AF_INET6, 128, True, u'2404:6800:4004:80c::101f', 80, 80)],
False,
None,
63, '0x01')
'0x01')
assert mock_ipt_chain_exists.mock_calls == [
call(AF_INET6, 'nat', 'sshuttle-1024')
]
assert mock_ipt_ttl.mock_calls == [
call(AF_INET6, 'nat', '-A', 'sshuttle-1024', '-j', 'RETURN',
'-m', 'hl', '--hl-eq', '63')
]
assert mock_ipt.mock_calls == [
call(AF_INET6, 'nat', '-D', 'OUTPUT', '-j', 'sshuttle-1024'),
call(AF_INET6, 'nat', '-D', 'PREROUTING', '-j', 'sshuttle-1024'),
@ -134,11 +128,9 @@ def test_setup_firewall(mock_ipt_chain_exists, mock_ipt_ttl, mock_ipt):
'--to-ports', '1024')
]
mock_ipt_chain_exists.reset_mock()
mock_ipt_ttl.reset_mock()
mock_ipt.reset_mock()
assert mock_ipt_chain_exists.mock_calls == []
assert mock_ipt_ttl.mock_calls == []
assert mock_ipt.mock_calls == []
with pytest.raises(Exception) as excinfo:
@ -150,10 +142,9 @@ def test_setup_firewall(mock_ipt_chain_exists, mock_ipt_ttl, mock_ipt):
(AF_INET, 32, True, u'1.2.3.66', 8080, 8080)],
True,
None,
63, '0x01')
'0x01')
assert str(excinfo.value) == 'UDP not supported by nat method_name'
assert mock_ipt_chain_exists.mock_calls == []
assert mock_ipt_ttl.mock_calls == []
assert mock_ipt.mock_calls == []
method.setup_firewall(
@ -164,14 +155,10 @@ def test_setup_firewall(mock_ipt_chain_exists, mock_ipt_ttl, mock_ipt):
(AF_INET, 32, True, u'1.2.3.66', 8080, 8080)],
False,
None,
63, '0x01')
'0x01')
assert mock_ipt_chain_exists.mock_calls == [
call(AF_INET, 'nat', 'sshuttle-1025')
]
assert mock_ipt_ttl.mock_calls == [
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'),
call(AF_INET, 'nat', '-D', 'PREROUTING', '-j', 'sshuttle-1025'),
@ -193,14 +180,12 @@ def test_setup_firewall(mock_ipt_chain_exists, mock_ipt_ttl, mock_ipt):
'--to-ports', '1025')
]
mock_ipt_chain_exists.reset_mock()
mock_ipt_ttl.reset_mock()
mock_ipt.reset_mock()
method.restore_firewall(1025, AF_INET, False, None)
assert mock_ipt_chain_exists.mock_calls == [
call(AF_INET, 'nat', 'sshuttle-1025')
]
assert mock_ipt_ttl.mock_calls == []
assert mock_ipt.mock_calls == [
call(AF_INET, 'nat', '-D', 'OUTPUT', '-j',
'sshuttle-1025'),
@ -210,14 +195,12 @@ def test_setup_firewall(mock_ipt_chain_exists, mock_ipt_ttl, mock_ipt):
call(AF_INET, 'nat', '-X', 'sshuttle-1025')
]
mock_ipt_chain_exists.reset_mock()
mock_ipt_ttl.reset_mock()
mock_ipt.reset_mock()
method.restore_firewall(1025, AF_INET6, False, None)
assert mock_ipt_chain_exists.mock_calls == [
call(AF_INET6, 'nat', 'sshuttle-1025')
]
assert mock_ipt_ttl.mock_calls == []
assert mock_ipt.mock_calls == [
call(AF_INET6, 'nat', '-D', 'OUTPUT', '-j', 'sshuttle-1025'),
call(AF_INET6, 'nat', '-D', 'PREROUTING', '-j',
@ -226,5 +209,4 @@ def test_setup_firewall(mock_ipt_chain_exists, mock_ipt_ttl, mock_ipt):
call(AF_INET6, 'nat', '-X', 'sshuttle-1025')
]
mock_ipt_chain_exists.reset_mock()
mock_ipt_ttl.reset_mock()
mock_ipt.reset_mock()