[2.2.x] Fixed CVE-2022-28347 -- Protected QuerySet.explain(**options) against SQL injection on PostgreSQL.

Backport of 6723a26e59b0b5429a0c5873941e01a2e1bdbb81 from main.

5 files changed, 70 insertions, 8 deletions

diff --git a/django/db/backends/postgresql/features.py b/django/db/backends/postgresql/features.py
index 5c8701c396..9f63ca6b0c 100644
--- a/django/db/backends/postgresql/features.py
+++ b/django/db/backends/postgresql/features.py
@@ -53,7 +53,6 @@ class DatabaseFeatures(BaseDatabaseFeatures):
     supports_over_clause = True
     supports_aggregate_filter_clause = True
     supported_explain_formats = {'JSON', 'TEXT', 'XML', 'YAML'}
-    validates_explain_options = False  # A query will error on invalid options.
 
     @cached_property
     def is_postgresql_9_5(self):
diff --git a/django/db/backends/postgresql/operations.py b/django/db/backends/postgresql/operations.py
index 66e5482be6..66ac2d5d10 100644
--- a/django/db/backends/postgresql/operations.py
+++ b/django/db/backends/postgresql/operations.py
@@ -8,6 +8,18 @@ from django.db.backends.base.operations import BaseDatabaseOperations
 class DatabaseOperations(BaseDatabaseOperations):
     cast_char_field_without_max_length = 'varchar'
     explain_prefix = 'EXPLAIN'
+    explain_options = frozenset(
+        [
+            "ANALYZE",
+            "BUFFERS",
+            "COSTS",
+            "SETTINGS",
+            "SUMMARY",
+            "TIMING",
+            "VERBOSE",
+            "WAL",
+        ]
+    )
     cast_data_types = {
         'AutoField': 'integer',
         'BigAutoField': 'bigint',
@@ -267,15 +279,20 @@ class DatabaseOperations(BaseDatabaseOperations):
         return start_, end_
 
     def explain_query_prefix(self, format=None, **options):
-        prefix = super().explain_query_prefix(format)
         extra = {}
-        if format:
-            extra['FORMAT'] = format
+        # Normalize options.
         if options:
-            extra.update({
+            options = {
                 name.upper(): 'true' if value else 'false'
                 for name, value in options.items()
-            })
+            }
+            for valid_option in self.explain_options:
+                value = options.pop(valid_option, None)
+                if value is not None:
+                    extra[valid_option.upper()] = value
+        prefix = super().explain_query_prefix(format, **options)
+        if format:
+            extra['FORMAT'] = format
         if extra:
             prefix += ' (%s)' % ', '.join('%s %s' % i for i in extra.items())
         return prefix
diff --git a/django/db/models/sql/query.py b/django/db/models/sql/query.py
index 412e817f10..1e823cfe74 100644
--- a/django/db/models/sql/query.py
+++ b/django/db/models/sql/query.py
@@ -45,6 +45,10 @@ __all__ = ['Query', 'RawQuery']
 # SQL comments are forbidden in column aliases.
 FORBIDDEN_ALIAS_PATTERN = re.compile(r"['`\"\]\[;\s]|--|/\*|\*/")
 
+# Inspired from
+# https://www.postgresql.org/docs/current/sql-syntax-lexical.html#SQL-SYNTAX-IDENTIFIERS
+EXPLAIN_OPTIONS_PATTERN = re.compile(r"[\w\-]+")
+
 
 def get_field_names_from_opts(opts):
     return set(chain.from_iterable(
@@ -528,6 +532,12 @@ class Query:
 
     def explain(self, using, format=None, **options):
         q = self.clone()
+        for option_name in options:
+            if (
+                not EXPLAIN_OPTIONS_PATTERN.fullmatch(option_name) or
+                "--" in option_name
+            ):
+                raise ValueError("Invalid option name: '%s'." % option_name)
         q.explain_query = True
         q.explain_format = format
         q.explain_options = options
diff --git a/docs/releases/2.2.28.txt b/docs/releases/2.2.28.txt
index a894bddb3c..43270fc5c0 100644
--- a/docs/releases/2.2.28.txt
+++ b/docs/releases/2.2.28.txt
@@ -13,3 +13,10 @@ CVE-2022-28346: Potential SQL injection in ``QuerySet.annotate()``, ``aggregate(
 :meth:`~.QuerySet.extra` methods were subject to SQL injection in column
 aliases, using a suitably crafted dictionary, with dictionary expansion, as the
 ``**kwargs`` passed to these methods.
+
+CVE-2022-28347: Potential SQL injection via ``QuerySet.explain(**options)`` on PostgreSQL
+=========================================================================================
+
+:meth:`.QuerySet.explain` method was subject to SQL injection in option names,
+using a suitably crafted dictionary, with dictionary expansion, as the
+``**options`` argument.
diff --git a/tests/queries/test_explain.py b/tests/queries/test_explain.py
index 9428bd88e9..209c192307 100644
--- a/tests/queries/test_explain.py
+++ b/tests/queries/test_explain.py
@@ -41,8 +41,8 @@ class ExplainTests(TestCase):
 
     @skipUnlessDBFeature('validates_explain_options')
     def test_unknown_options(self):
-        with self.assertRaisesMessage(ValueError, 'Unknown options: test, test2'):
-            Tag.objects.all().explain(test=1, test2=1)
+        with self.assertRaisesMessage(ValueError, "Unknown options: TEST, TEST2"):
+            Tag.objects.all().explain(**{"TEST": 1, "TEST2": 1})
 
     def test_unknown_format(self):
         msg = 'DOES NOT EXIST is not a recognized format.'
@@ -71,6 +71,35 @@ class ExplainTests(TestCase):
                     option = '{} {}'.format(name.upper(), 'true' if value else 'false')
                     self.assertIn(option, captured_queries[0]['sql'])
 
+    def test_option_sql_injection(self):
+        qs = Tag.objects.filter(name="test")
+        options = {"SUMMARY true) SELECT 1; --": True}
+        msg = "Invalid option name: 'SUMMARY true) SELECT 1; --'"
+        with self.assertRaisesMessage(ValueError, msg):
+            qs.explain(**options)
+
+    def test_invalid_option_names(self):
+        qs = Tag.objects.filter(name="test")
+        tests = [
+            'opt"ion',
+            "o'ption",
+            "op`tion",
+            "opti on",
+            "option--",
+            "optio\tn",
+            "o\nption",
+            "option;",
+            "你 好",
+            # [] are used by MSSQL.
+            "option[",
+            "option]",
+        ]
+        for invalid_option in tests:
+            with self.subTest(invalid_option):
+                msg = "Invalid option name: '%s'" % invalid_option
+                with self.assertRaisesMessage(ValueError, msg):
+                    qs.explain(**{invalid_option: True})
+
     @unittest.skipUnless(connection.vendor == 'mysql', 'MySQL specific')
     def test_mysql_text_to_traditional(self):
         # Initialize the cached property, if needed, to prevent a query for