From e6a3a763d6c8ac793bf6ecf0c52998c9e407c296 Mon Sep 17 00:00:00 2001
From: spicysharkco <321699413+spicysharkco@users.noreply.github.com>
Date: Fri, 16 Oct 2026 22:11:21 +0000
Subject: [PATCH 1/2] Disable interpolation when reading the connection service
 file

ConfigParser treated "%" in service file values as interpolation syntax,
so a password such as "pa%ss" raised InterpolationSyntaxError when the
service was selected. libpq reads the values literally.
---
 asyncpg/connect_utils.py | 2 +-
 tests/test_connect.py    | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/asyncpg/connect_utils.py b/asyncpg/connect_utils.py
index e215391b..092723a7 100644
--- a/asyncpg/connect_utils.py
+++ b/asyncpg/connect_utils.py
@@ -453,7 +453,7 @@ def _parse_connect_dsn_and_args(*, dsn, host, port, user,
                     server_settings = {**query, **server_settings}
 
         if connection_service_file is not None and service is not None:
-            pg_service = configparser.ConfigParser()
+            pg_service = configparser.ConfigParser(interpolation=None)
             pg_service.read(connection_service_file)
             if service in pg_service.sections():
                 service_params = pg_service[service]
diff --git a/tests/test_connect.py b/tests/test_connect.py
index 1c25d8d6..6aa34fb9 100644
--- a/tests/test_connect.py
+++ b/tests/test_connect.py
@@ -1286,7 +1286,7 @@ def test_connect_connection_service_file(self):
 host=somehost
 database=test_dbname
 user=admin
-password=test_password
+password=test%password
 target_session_attrs=primary
 krbsrvname=fakekrbsrvname
 gsslib=sspi
@@ -1322,7 +1322,7 @@ def test_connect_connection_service_file(self):
                     [('somehost', 5433)],
                     {
                         'user': 'admin',
-                        'password': 'test_password',
+                        'password': 'test%password',
                         'database': 'test_dbname',
                         'target_session_attrs': 'primary',
                         'krbsrvname': 'fakekrbsrvname',

From 6e90c5179891495f5ceb569e41cc5f1b89f3a833 Mon Sep 17 00:00:00 2001
From: spicysharkco <321699413+spicysharkco@users.noreply.github.com>
Date: Tue, 20 Oct 2026 05:51:41 +0000
Subject: [PATCH 2/2] Test that service file values are read literally

A new test_service_literal section puts %, %%, %(w)s, $ and ${x} in
host, dbname, user and password and checks each comes back unchanged.
The existing case only covered a lone % before a letter, which a
parser that still collapses %% would also pass.
---
 tests/test_connect.py | 23 +++++++++++++++++++++++
 1 file changed, 23 insertions(+)

diff --git a/tests/test_connect.py b/tests/test_connect.py
index 6aa34fb9..6af91c67 100644
--- a/tests/test_connect.py
+++ b/tests/test_connect.py
@@ -1290,6 +1290,12 @@ def test_connect_connection_service_file(self):
 target_session_attrs=primary
 krbsrvname=fakekrbsrvname
 gsslib=sspi
+
+[test_service_literal]
+host=some%host
+dbname=test%%dbname
+user=ad%min
+password=p%%ss%(w)s$rd${x}
         '''))
         connection_service_file.close()
         os.chmod(connection_service_file.name, stat.S_IWUSR | stat.S_IRUSR)
@@ -1330,6 +1336,23 @@ def test_connect_connection_service_file(self):
                     }
                 )
             })
+            # Test that values are used literally: no "%" or "$"
+            # interpolation, and "%%" is not collapsed
+            self.run_testcase({
+                'dsn': 'postgresql://?service=test_service_literal',
+                'env': {
+                    'PGSERVICEFILE': connection_service_file.name
+                },
+                'result': (
+                    [('some%host', 5432)],
+                    {
+                        'user': 'ad%min',
+                        'password': 'p%%ss%(w)s$rd${x}',
+                        'database': 'test%%dbname',
+                        'target_session_attrs': 'any',
+                    }
+                )
+            })
             # Test that envvars are overridden by service file
             self.run_testcase({
                 'dsn': 'postgresql://?service=test_service_dbname',