Add unit tests for GSSAPI authentication

.github/workflows/install-krb5.sh

@@ -0,0 +1,10 @@
+#!/bin/bash
+
+set -Eexuo pipefail
+
+if [ "$RUNNER_OS" == "Linux" ]; then
+    # Assume Ubuntu since this is the only Linux used in CI.
+    sudo apt-get update
+    sudo apt-get install -y --no-install-recommends \
+        libkrb5-dev krb5-user krb5-kdc krb5-admin-server
+fi

.github/workflows/tests.yml

@@ -62,6 +62,7 @@ jobs:
     - name: Install Python Deps
       if: steps.release.outputs.version == 0
       run: |
+        .github/workflows/install-krb5.sh
         python -m pip install -U pip setuptools wheel
         python -m pip install -e .[test]
 
@@ -122,6 +123,7 @@ jobs:
     - name: Install Python Deps
       if: steps.release.outputs.version == 0
       run: |
+        .github/workflows/install-krb5.sh
         python -m pip install -U pip setuptools wheel
         python -m pip install -e .[test]
 

asyncpg/protocol/coreproto.pyx

@@ -719,17 +719,18 @@ cdef class CoreProtocol:
             import gssapi
         except ModuleNotFoundError:
             raise RuntimeError(
-                'gssapi module not found; please install asyncpg[gss] to use '
-                'asyncpg with Kerberos or GSSAPI authentication'
+                'gssapi module not found; please install asyncpg[gssapi] to '
+                'use asyncpg with Kerberos or GSSAPI authentication'
             ) from None
 
         service_name = self.con_params.krbsrvname or 'postgres'
         # find the canonical name of the server host
         if isinstance(self.address, str):
-            host = socket.gethostname()
-        else:
-            host = self.address[0]
-        host_cname = socket.gethostbyname_ex(host)[0].rstrip('.')
+            raise RuntimeError('GSSAPI authentication is only supported for '
+                               'TCP/IP connections')
+
+        host = self.address[0]
+        host_cname = socket.gethostbyname_ex(host)[0]
         gss_name = gssapi.Name(f'{service_name}/{host_cname}')
         self.gss_ctx = gssapi.SecurityContext(name=gss_name, usage='initiate')
 

pyproject.toml

@@ -35,12 +35,14 @@ dependencies = [
 github = "https://github.com/MagicStack/asyncpg"
 
 [project.optional-dependencies]
-gss = [
+gssapi = [
     'gssapi',
 ]
 test = [
     'flake8~=6.1',
     'uvloop>=0.15.3; platform_system != "Windows" and python_version < "3.12.0"',
+    'gssapi; platform_system == "Linux"',
+    'k5test; platform_system == "Linux"',
 ]
 docs = [
     'Sphinx~=5.3.0',

tests/test_connect.py

@@ -130,30 +130,22 @@ def test_server_version_02(self):
 CORRECT_PASSWORD = 'correct\u1680password'
 
 
-class TestAuthentication(tb.ConnectedTestCase):
+class BaseTestAuthentication(tb.ConnectedTestCase):
+    USERS = []
+
     def setUp(self):
         super().setUp()
 
         if not self.cluster.is_managed():
             self.skipTest('unmanaged cluster')
 
-        methods = [
-            ('trust', None),
-            ('reject', None),
-            ('scram-sha-256', CORRECT_PASSWORD),
-            ('md5', CORRECT_PASSWORD),
-            ('password', CORRECT_PASSWORD),
-        ]
-
         self.cluster.reset_hba()
 
         create_script = []
-        for method, password in methods:
+        for username, method, password in self.USERS:
             if method == 'scram-sha-256' and self.server_version.major < 10:
                 continue
 
-            username = method.replace('-', '_')
-
             # if this is a SCRAM password, we need to set the encryption method
             # to "scram-sha-256" in order to properly hash the password
             if method == 'scram-sha-256':
@@ -162,7 +154,7 @@ def setUp(self):
                 )
 
             create_script.append(
-                'CREATE ROLE {}_user WITH LOGIN{};'.format(
+                'CREATE ROLE "{}" WITH LOGIN{};'.format(
                     username,
                     f' PASSWORD E{(password or "")!r}'
                 )
@@ -175,20 +167,20 @@ def setUp(self):
                     "SET password_encryption = 'md5';"
                 )
 
-            if _system != 'Windows':
+            if _system != 'Windows' and method != 'gss':
                 self.cluster.add_hba_entry(
                     type='local',
-                    database='postgres', user='{}_user'.format(username),
+                    database='postgres', user=username,
                     auth_method=method)
 
             self.cluster.add_hba_entry(
                 type='host', address=ipaddress.ip_network('127.0.0.0/24'),
-                database='postgres', user='{}_user'.format(username),
+                database='postgres', user=username,
                 auth_method=method)
 
             self.cluster.add_hba_entry(
                 type='host', address=ipaddress.ip_network('::1/128'),
-                database='postgres', user='{}_user'.format(username),
+                database='postgres', user=username,
                 auth_method=method)
 
         # Put hba changes into effect
@@ -201,28 +193,28 @@ def tearDown(self):
         # Reset cluster's pg_hba.conf since we've meddled with it
         self.cluster.trust_local_connections()
 
-        methods = [
-            'trust',
-            'reject',
-            'scram-sha-256',
-            'md5',
-            'password',
-        ]
-
         drop_script = []
-        for method in methods:
+        for username, method, _ in self.USERS:
             if method == 'scram-sha-256' and self.server_version.major < 10:
                 continue
 
-            username = method.replace('-', '_')
-
-            drop_script.append('DROP ROLE {}_user;'.format(username))
+            drop_script.append('DROP ROLE "{}";'.format(username))
 
         drop_script = '\n'.join(drop_script)
         self.loop.run_until_complete(self.con.execute(drop_script))
 
         super().tearDown()
 
+
+class TestAuthentication(BaseTestAuthentication):
+    USERS = [
+        ('trust_user', 'trust', None),
+        ('reject_user', 'reject', None),
+        ('scram_sha_256_user', 'scram-sha-256', CORRECT_PASSWORD),
+        ('md5_user', 'md5', CORRECT_PASSWORD),
+        ('password_user', 'password', CORRECT_PASSWORD),
+    ]
+
     async def _try_connect(self, **kwargs):
         # On Windows the server sometimes just closes
         # the connection sooner than we receive the
@@ -388,6 +380,62 @@ async def test_auth_md5_unsupported(self, _):
             await self.connect(user='md5_user', password=CORRECT_PASSWORD)
 
 
+class TestGssAuthentication(BaseTestAuthentication):
+    @classmethod
+    def setUpClass(cls):
+        try:
+            from k5test.realm import K5Realm
+        except ModuleNotFoundError:
+            raise unittest.SkipTest('k5test not installed')
+
+        cls.realm = K5Realm()
+        cls.addClassCleanup(cls.realm.stop)
+        # Setup environment before starting the cluster.
+        cm = unittest.mock.patch.dict(os.environ, cls.realm.env)
+        cm.__enter__()
+        cls.addClassCleanup(cm.__exit__, None, None, None)
+        # Add credentials.
+        cls.realm.addprinc('postgres/localhost')
+        cls.realm.extract_keytab('postgres/localhost', cls.realm.keytab)
+
+        cls.USERS = [(cls.realm.user_princ, 'gss', None)]
+        super().setUpClass()
+
+        cls.cluster.override_connection_spec(host='localhost')
+
+    @classmethod
+    def get_server_settings(cls):
+        settings = super().get_server_settings()
+        settings['krb_server_keyfile'] = f'FILE:{cls.realm.keytab}'
+        return settings
+
+    @classmethod
+    def setup_cluster(cls):
+        cls.cluster = cls.new_cluster(pg_cluster.TempCluster)
+        cls.start_cluster(
+            cls.cluster, server_settings=cls.get_server_settings())
+
+    async def test_auth_gssapi(self):
+        conn = await self.connect(user=self.realm.user_princ)
+        await conn.close()
+
+        # Service name mismatch.
+        with self.assertRaisesRegex(
+            exceptions.InternalClientError,
+            'Server .* not found'
+        ):
+            await self.connect(user=self.realm.user_princ, krbsrvname='wrong')
+
+        # Credentials mismatch.
+        self.realm.addprinc('wrong_user', 'password')
+        self.realm.kinit('wrong_user', 'password')
+        with self.assertRaisesRegex(
+            exceptions.InvalidAuthorizationSpecificationError,
+            'GSSAPI authentication failed for user'
+        ):
+            await self.connect(user=self.realm.user_princ)
+
+
 class TestConnectParams(tb.TestCase):
 
     TESTS = [