ssh-audit/test/test_policy.py

import hashlib
import pytest
from datetime import date


class TestPolicy:
    @pytest.fixture(autouse=True)
    def init(self, ssh_audit):
        self.Policy = ssh_audit.Policy
        self.wbuf = ssh_audit.WriteBuf
        self.ssh2 = ssh_audit.SSH2


    def _get_kex(self):
        '''Returns an SSH2.Kex object to simulate a server connection.'''

        w = self.wbuf()
        w.write(b'\x00\x11\x22\x33\x44\x55\x66\x77\x88\x99\xaa\xbb\xcc\xdd\xee\xff')
        w.write_list(['kex_alg1', 'kex_alg2'])
        w.write_list(['key_alg1', 'key_alg2'])
        w.write_list(['cipher_alg1', 'cipher_alg2', 'cipher_alg3'])
        w.write_list(['cipher_alg1', 'cipher_alg2', 'cipher_alg3'])
        w.write_list(['mac_alg1', 'mac_alg2', 'mac_alg3'])
        w.write_list(['mac_alg1', 'mac_alg2', 'mac_alg3'])
        w.write_list(['comp_alg1', 'comp_alg2'])
        w.write_list(['comp_alg1', 'comp_alg2'])
        w.write_list([''])
        w.write_list([''])
        w.write_byte(False)
        w.write_int(0)
        return self.ssh2.Kex.parse(w.write_flush())


    def test_policy_basic(self):
        '''Ensure that a basic policy can be parsed correctly.'''

        policy_data = '''# This is a comment
name = "Test Policy"
version = 1

compressions = comp_alg1
host keys = key_alg1
key exchanges = kex_alg1, kex_alg2
ciphers = cipher_alg1, cipher_alg2, cipher_alg3
macs = mac_alg1, mac_alg2, mac_alg3'''

        policy = self.Policy(policy_data=policy_data)
        assert str(policy) == "Name: [Test Policy]\nVersion: [1]\nBanner: {undefined}\nHeader: {undefined}\nCompressions: comp_alg1\nHost Keys: key_alg1\nKey Exchanges: kex_alg1, kex_alg2\nCiphers: cipher_alg1, cipher_alg2, cipher_alg3\nMACs: mac_alg1, mac_alg2, mac_alg3"


    def test_policy_invalid_1(self):
        '''Basic policy, but with 'ciphersx' instead of 'ciphers'.'''

        policy_data = '''# This is a comment
name = "Test Policy"
version = 1

compressions = comp_alg1
host keys = key_alg1
key exchanges = kex_alg1, kex_alg2
ciphersx = cipher_alg1, cipher_alg2, cipher_alg3
macs = mac_alg1, mac_alg2, mac_alg3'''

        failed = False
        try:
            self.Policy(policy_data=policy_data)
        except ValueError:
            failed = True

        assert failed, "Invalid policy did not cause Policy object to throw exception"


    def test_policy_invalid_2(self):
        '''Basic policy, but is missing the required name field.'''

        policy_data = '''# This is a comment
#name = "Test Policy"
version = 1

compressions = comp_alg1
host keys = key_alg1
key exchanges = kex_alg1, kex_alg2
ciphers = cipher_alg1, cipher_alg2, cipher_alg3
macs = mac_alg1, mac_alg2, mac_alg3'''

        failed = False
        try:
            self.Policy(policy_data=policy_data)
        except ValueError:
            failed = True

        assert failed, "Invalid policy did not cause Policy object to throw exception"


    def test_policy_invalid_3(self):
        '''Basic policy, but is missing the required version field.'''

        policy_data = '''# This is a comment
name = "Test Policy"
#version = 1

compressions = comp_alg1
host keys = key_alg1
key exchanges = kex_alg1, kex_alg2
ciphers = cipher_alg1, cipher_alg2, cipher_alg3
macs = mac_alg1, mac_alg2, mac_alg3'''

        failed = False
        try:
            self.Policy(policy_data=policy_data)
        except ValueError:
            failed = True

        assert failed, "Invalid policy did not cause Policy object to throw exception"


    def test_policy_invalid_4(self):
        '''Basic policy, but is missing quotes in the name field.'''

        policy_data = '''# This is a comment
name = Test Policy
version = 1

compressions = comp_alg1
host keys = key_alg1
key exchanges = kex_alg1, kex_alg2
ciphers = cipher_alg1, cipher_alg2, cipher_alg3
macs = mac_alg1, mac_alg2, mac_alg3'''

        failed = False
        try:
            self.Policy(policy_data=policy_data)
        except ValueError:
            failed = True

        assert failed, "Invalid policy did not cause Policy object to throw exception"


    def test_policy_invalid_5(self):
        '''Basic policy, but is missing quotes in the banner field.'''

        policy_data = '''# This is a comment
name = "Test Policy"
version = 1

banner = 0mg
compressions = comp_alg1
host keys = key_alg1
key exchanges = kex_alg1, kex_alg2
ciphers = cipher_alg1, cipher_alg2, cipher_alg3
macs = mac_alg1, mac_alg2, mac_alg3'''

        failed = False
        try:
            self.Policy(policy_data=policy_data)
        except ValueError:
            failed = True

        assert failed, "Invalid policy did not cause Policy object to throw exception"


    def test_policy_invalid_6(self):
        '''Basic policy, but is missing quotes in the header field.'''

        policy_data = '''# This is a comment
name = "Test Policy"
version = 1

header = 0mg
compressions = comp_alg1
host keys = key_alg1
key exchanges = kex_alg1, kex_alg2
ciphers = cipher_alg1, cipher_alg2, cipher_alg3
macs = mac_alg1, mac_alg2, mac_alg3'''

        failed = False
        try:
            self.Policy(policy_data=policy_data)
        except ValueError:
            failed = True

        assert failed, "Invalid policy did not cause Policy object to throw exception"


    def test_policy_create_1(self):
        '''Creates a policy from a kex and ensures it is generated exactly as expected.'''

        kex = self._get_kex()
        pol_data = self.Policy.create('www.l0l.com', 'bannerX', 'headerX', kex)

        # Today's date is embedded in the policy, so filter it out to get repeatable results.
        pol_data = pol_data.replace(date.today().strftime('%Y/%m/%d'), '[todays date]')

        # Instead of writing out the entire expected policy--line by line--just check that it has the expected hash.
        assert hashlib.sha256(pol_data.encode('ascii')).hexdigest() == 'e830fb9e5731995e5e4858b2b6d16704d7e5c2769d3a8d9acdd023a83ab337c5'


    def test_policy_evaluate_passing_1(self):
        '''Creates a policy and evaluates it against the same server'''

        kex = self._get_kex()
        policy_data = self.Policy.create('www.l0l.com', None, None, kex)
        policy = self.Policy(policy_data=policy_data)

        ret, errors = policy.evaluate('SSH Server 1.0', None, kex)
        assert ret is True
        assert len(errors) == 0


    def test_policy_evaluate_failing_1(self):
        '''Ensure that a policy with a specified banner fails against a server with a different banner'''

        policy_data = '''name = "Test Policy"
version = 1
banner = "XXX mismatched banner XXX"
compressions = comp_alg1, comp_alg2
host keys = key_alg1, key_alg2
key exchanges = kex_alg1, kex_alg2
ciphers = cipher_alg1, cipher_alg2, cipher_alg3
macs = mac_alg1, mac_alg2, mac_alg3'''

        policy = self.Policy(policy_data=policy_data)
        ret, errors = policy.evaluate('SSH Server 1.0', None, self._get_kex())
        assert ret is False
        assert len(errors) == 1
        assert errors[0].find('Banner did not match.') != -1


    def test_policy_evaluate_failing_2(self):
        '''Ensure that a mismatched compressions list results in a failure'''

        policy_data = '''name = "Test Policy"
version = 1
compressions = XXXmismatchedXXX, comp_alg1, comp_alg2
host keys = key_alg1, key_alg2
key exchanges = kex_alg1, kex_alg2
ciphers = cipher_alg1, cipher_alg2, cipher_alg3
macs = mac_alg1, mac_alg2, mac_alg3'''

        policy = self.Policy(policy_data=policy_data)
        ret, errors = policy.evaluate('SSH Server 1.0', None, self._get_kex())
        assert ret is False
        assert len(errors) == 1
        assert errors[0].find('Compression types did not match.') != -1


    def test_policy_evaluate_failing_3(self):
        '''Ensure that a mismatched host keys results in a failure'''

        policy_data = '''name = "Test Policy"
version = 1
compressions = comp_alg1, comp_alg2
host keys = XXXmismatchedXXX, key_alg1, key_alg2
key exchanges = kex_alg1, kex_alg2
ciphers = cipher_alg1, cipher_alg2, cipher_alg3
macs = mac_alg1, mac_alg2, mac_alg3'''

        policy = self.Policy(policy_data=policy_data)
        ret, errors = policy.evaluate('SSH Server 1.0', None, self._get_kex())
        assert ret is False
        assert len(errors) == 1
        assert errors[0].find('Host key types did not match.') != -1


    def test_policy_evaluate_failing_4(self):
        '''Ensure that a mismatched key exchange list results in a failure'''

        policy_data = '''name = "Test Policy"
version = 1
compressions = comp_alg1, comp_alg2
host keys = key_alg1, key_alg2
key exchanges = XXXmismatchedXXX, kex_alg1, kex_alg2
ciphers = cipher_alg1, cipher_alg2, cipher_alg3
macs = mac_alg1, mac_alg2, mac_alg3'''

        policy = self.Policy(policy_data=policy_data)
        ret, errors = policy.evaluate('SSH Server 1.0', None, self._get_kex())
        assert ret is False
        assert len(errors) == 1
        assert errors[0].find('Key exchanges did not match.') != -1


    def test_policy_evaluate_failing_5(self):
        '''Ensure that a mismatched cipher list results in a failure'''

        policy_data = '''name = "Test Policy"
version = 1
compressions = comp_alg1, comp_alg2
host keys = key_alg1, key_alg2
key exchanges = kex_alg1, kex_alg2
ciphers = cipher_alg1, XXXmismatched, cipher_alg2, cipher_alg3
macs = mac_alg1, mac_alg2, mac_alg3'''

        policy = self.Policy(policy_data=policy_data)
        ret, errors = policy.evaluate('SSH Server 1.0', None, self._get_kex())
        assert ret is False
        assert len(errors) == 1
        assert errors[0].find('Ciphers did not match.') != -1


    def test_policy_evaluate_failing_6(self):
        '''Ensure that a mismatched MAC list results in a failure'''

        policy_data = '''name = "Test Policy"
version = 1
compressions = comp_alg1, comp_alg2
host keys = key_alg1, key_alg2
key exchanges = kex_alg1, kex_alg2
ciphers = cipher_alg1, cipher_alg2, cipher_alg3
macs = mac_alg1, mac_alg2, XXXmismatched, mac_alg3'''

        policy = self.Policy(policy_data=policy_data)
        ret, errors = policy.evaluate('SSH Server 1.0', None, self._get_kex())
        assert ret is False
        assert len(errors) == 1
        assert errors[0].find('MACs did not match.') != -1


    def test_policy_evaluate_failing_7(self):
        '''Ensure that a mismatched host keys and MACs results in a failure'''

        policy_data = '''name = "Test Policy"
version = 1
compressions = comp_alg1, comp_alg2
host keys = key_alg1, key_alg2, XXXmismatchedXXX
key exchanges = kex_alg1, kex_alg2
ciphers = cipher_alg1, cipher_alg2, cipher_alg3
macs = mac_alg1, mac_alg2, XXXmismatchedXXX, mac_alg3'''

        policy = self.Policy(policy_data=policy_data)
        ret, errors = policy.evaluate('SSH Server 1.0', None, self._get_kex())
        assert ret is False
        assert len(errors) == 2

        errors_str = ', '.join(errors)
        assert errors_str.find('Host key types did not match.') != -1
        assert errors_str.find('MACs did not match.') != -1