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# Copyright (C) 2026 Danilo M. <danix@danix.xyz>
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License version 2 as
# published by the Free Software Foundation.
#
# 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, write to the Free Software
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
"""Tests for the Received-chain trust boundary walk."""
import pathlib
import unittest
from abusectl import parse
FIXTURES = pathlib.Path(__file__).parent / "fixtures"
def load(name: str) -> bytes:
return (FIXTURES / name).read_bytes()
class TestReceivedChain(unittest.TestCase):
def test_hops_are_returned_outermost_first(self):
hops = parse.received_hops(load("simple.eml"))
self.assertEqual([h.ip for h in hops], ["192.0.2.11", "203.0.113.42"])
def test_the_first_untrusted_hop_is_the_sender(self):
ip = parse.sending_ip(load("simple.eml"), trusted=["192.0.2.0/24"])
self.assertEqual(ip, "203.0.113.42")
def test_a_forged_chain_stops_at_the_first_untrusted_hop(self):
# The attacker prepended two hops naming an innocent third party.
# Walking past the boundary would report 198.51.100.7, which is
# someone else's address in a header the attacker wrote.
ip = parse.sending_ip(load("forged-chain.eml"), trusted=["192.0.2.0/24"])
self.assertEqual(ip, "203.0.113.99")
def test_hops_below_the_boundary_are_still_recorded(self):
# Recorded, but as untrusted: they may be useful and must not be
# presented as fact.
hops = parse.received_hops(load("forged-chain.eml"))
self.assertEqual(
[h.ip for h in hops],
["192.0.2.11", "203.0.113.99", "198.51.100.7", "198.51.100.8"],
)
def test_no_trusted_relays_is_an_error_not_a_guess(self):
# Guessing the outermost public IP is wrong in exactly the case that
# matters, and a confident wrong answer gets a third party reported.
with self.assertRaises(parse.NoTrustBoundary):
parse.sending_ip(load("simple.eml"), trusted=[])
def test_a_chain_entirely_inside_the_boundary_has_no_sender(self):
ip = parse.sending_ip(
load("simple.eml"), trusted=["192.0.2.0/24", "203.0.113.0/24"]
)
self.assertIsNone(ip)
class TestSenderDomains(unittest.TestCase):
def test_the_three_sender_headers_are_collected(self):
domains = parse.sender_domains(load("simple.eml"))
self.assertEqual(
domains,
{
"return_path": "sender.example.invalid",
"from": "bank.example.invalid",
"reply_to": "drop.example.invalid",
},
)
def test_reply_to_is_absent_when_it_matches_from(self):
# Only a DIFFERING Reply-To is an indicator; repeating From adds noise.
domains = parse.sender_domains(load("with-attachment.eml"))
self.assertNotIn("reply_to", domains)
def test_recipient_headers_are_never_returned(self):
# The safety property, asserted rather than assumed.
domains = parse.sender_domains(load("simple.eml"))
self.assertNotIn("example.org", domains.values())
class TestAuthResults(unittest.TestCase):
def test_verdicts_are_read_as_the_server_recorded_them(self):
auth = parse.auth_results(load("simple.eml"))
self.assertEqual(auth, {"spf": "fail", "dkim": "none", "dmarc": "fail"})
def test_a_message_with_no_auth_header_reports_nothing(self):
self.assertEqual(parse.auth_results(load("with-attachment.eml")), {})
if __name__ == "__main__":
unittest.main()
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