Forbid certain system functions over SQL adapter (#7829)

PostgreSQL supports certain SQL functions that allow [access to the
filesystem](https://www.postgresql.org/docs/16/functions-admin.html#FUNCTIONS-ADMIN-GENFILE),
managing backups, WAL and other administration functions of the
database.

This is not intended behavior of EdgeDB and goes against security model
of EdgeDB. To our knowledge, this feature is also not widely used by
users of PostgreSQL. Because of that, we are forbidding a range of
PostgreSQL system administration functions.

This change only affects access to EdgeDB via SQL adapter. Connections
directly to underlying PostgreSQL instance are not affected.

edb/pgsql/resolver/static.py

@@ -139,6 +139,88 @@ def eval_TypeCast(
     'pg_has_role': 2,
 }
 
+# Allowed functions from pg_catalog that start with `pg_`.
+# By default, all such functions are forbidden by default.
+# To see the list of forbidden functions, use `edb ls-forbidden-functions`.
+ALLOWED_ADMIN_FUNCTIONS = frozenset(
+    {
+        'pg_is_in_recovery',
+        'pg_is_wal_replay_paused',
+        'pg_get_wal_replay_pause_state',
+        'pg_column_size',
+        'pg_column_compression',
+        'pg_database_size',
+        'pg_indexes_size',
+        'pg_relation_size',
+        'pg_size_bytes',
+        'pg_size_pretty',
+        'pg_table_size',
+        'pg_tablespace_size',
+        'pg_total_relation_size',
+        'pg_relation_filenode',
+        'pg_relation_filepath',
+        'pg_filenode_relation',
+        'pg_char_to_encoding',
+        'pg_column_is_updatable',
+        'pg_conf_load_time',
+        'pg_current_xact_id',
+        'pg_current_xact_id_if_assigned',
+        'pg_describe_object',
+        'pg_encoding_max_length',
+        'pg_encoding_to_char',
+        'pg_get_constraintdef',
+        'pg_get_expr',
+        'pg_get_function_arg_default',
+        'pg_get_function_arguments',
+        'pg_get_function_identity_arguments',
+        'pg_get_function_result',
+        'pg_get_functiondef',
+        'pg_get_indexdef',
+        'pg_get_keywords',
+        'pg_get_multixact_members',
+        'pg_get_object_address',
+        'pg_get_partition_constraintdef',
+        'pg_get_partkeydef',
+        'pg_get_publication_tables',
+        'pg_get_replica_identity_index',
+        'pg_get_replication_slots',
+        'pg_get_ruledef',
+        'pg_get_serial_sequence',
+        'pg_get_shmem_allocations',
+        'pg_get_statisticsobjdef',
+        'pg_get_triggerdef',
+        'pg_get_userbyid',
+        'pg_get_viewdef',
+        'pg_options_to_table',
+        'pg_has_role',
+        'pg_function_is_visible',
+        'pg_opclass_is_visible',
+        'pg_operator_is_visible',
+        'pg_opfamily_is_visible',
+        'pg_statistics_obj_is_visible',
+        'pg_table_is_visible',
+        'pg_ts_config_is_visible',
+        'pg_ts_dict_is_visible',
+        'pg_ts_parser_is_visible',
+        'pg_ts_template_is_visible',
+        'pg_type_is_visible',
+        'pg_index_column_has_property',
+        'pg_index_has_property',
+        'pg_is_in_backup',
+        'pg_is_other_temp_schema',
+        'pg_jit_available',
+        'pg_relation_is_updatable',
+        'pg_sequence_last_value',
+        'pg_sequence_parameters',
+        'pg_timezone_abbrevs',
+        'pg_timezone_names',
+        'pg_typeof',
+        'pg_visible_in_snapshot',
+        'pg_xact_commit_timestamp',
+        'pg_xact_status',
+    }
+)
+
 
 @eval.register
 def eval_FuncCall(
@@ -153,6 +235,13 @@ def eval_FuncCall(
     if not fn_name:
         return None
 
+    if fn_name.startswith('pg_') and fn_name not in ALLOWED_ADMIN_FUNCTIONS:
+        raise errors.QueryError(
+            "forbidden function",
+            span=expr.span,
+            pgext_code=pgerror.ERROR_INSUFFICIENT_PRIVILEGE,
+        )
+
     if fn_name == 'current_schemas':
         return eval_current_schemas(expr, ctx=ctx)
 

edb/tools/edb.py

@@ -85,5 +85,6 @@ def load_ext(args: tuple[str, ...]):
 from . import gen_rust_ast  # noqa
 from . import ast_inheritance_graph  # noqa
 from . import parser_demo  # noqa
+from . import ls_forbidden_functions  # noqa
 from .profiling import cli as prof_cli  # noqa
 from .experimental_interpreter import edb_entry # noqa

edb/tools/ls_forbidden_functions.py

@@ -0,0 +1,66 @@
+#
+# This source file is part of the EdgeDB open source project.
+#
+# Copyright 2020-present MagicStack Inc. and the EdgeDB authors.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+from __future__ import annotations
+
+import asyncio
+
+from edb.tools.edb import edbcommands
+
+
+async def run():
+    import asyncpg
+
+    # import os
+    # localdev = os.path.expanduser('~/.local/share/edgedb/_localdev')
+    # c = await asyncpg.connect(
+    #     host=localdev, database='postgres', user='postgres'
+    # )
+
+    # docker run -it -p 5433:5432 --rm -e POSTGRES_PASSWORD=pass postgres:13
+    c = await asyncpg.connect(
+        host='localhost',
+        database='postgres',
+        user='postgres',
+        password='pass',
+        port='5433',
+    )
+
+    res = await c.fetch(
+        r'''
+        SELECT DISTINCT proname
+        FROM pg_proc p
+        INNER JOIN pg_namespace n ON pronamespace = n.oid
+        WHERE n.nspname = 'pg_catalog' AND proname like 'pg_%'
+        ORDER BY proname;
+        '''
+    )
+
+    import edb.pgsql.resolver.static as pg_r_static
+
+    print('Forbidden pg_* functions:')
+    for row in res:
+        [func_name] = row
+        if func_name in pg_r_static.ALLOWED_ADMIN_FUNCTIONS:
+            continue
+        print('  ', func_name)
+
+
+@edbcommands.command("ls-forbidden-functions")
+def main():
+    asyncio.run(run())

tests/test_sql_query.py

@@ -1408,6 +1408,19 @@ async def test_sql_query_error_12(self):
         res = await self.squery_values("SELECT 1")
         self.assertEqual(res, [[1]])
 
+    async def test_sql_query_error_13(self):
+        # forbidden functions
+
+        with self.assertRaisesRegex(
+            asyncpg.InsufficientPrivilegeError,
+            'forbidden function',
+            position="8",
+        ):
+            await self.scon.fetch("""SELECT pg_ls_dir('/')""")
+
+        res = await self.squery_values("""SELECT pg_is_in_recovery()""")
+        self.assertEqual(res, [[False]])
+
     @unittest.skip("this test flakes: #5783")
     async def test_sql_query_prepare_01(self):
         await self.scon.execute(