migrations: Escape more pedantically in pgroonga.0001_enable.

The psycopg2.SQL API unfortunately doesn’t work with
django.db.migrations.RunSQL, so we need to take a detour into
PL/pgSQL for EXECUTE and format.

Signed-off-by: Anders Kaseorg <anders@zulip.com>

pgroonga/migrations/0001_enable.py

@@ -11,8 +11,9 @@ class Migration(migrations.Migration):
     database_setting = settings.DATABASES["default"]
     if "postgres" in database_setting["ENGINE"]:
         operations = [
-            migrations.RunSQL("""
+            migrations.RunSQL([("""
-ALTER ROLE %(USER)s SET search_path TO %(SCHEMA)s,public,pgroonga,pg_catalog;
+DO $$BEGIN
+EXECUTE format('ALTER ROLE %%I SET search_path TO %%L,public,pgroonga,pg_catalog', %(USER)s, %(SCHEMA)s);
 
 SET search_path = %(SCHEMA)s,public,pgroonga,pg_catalog;
 
@@ -23,8 +24,10 @@ ALTER TABLE zerver_message ADD COLUMN search_pgroonga text;
 -- Django 1.10 may solve the problem.
 CREATE INDEX zerver_message_search_pgroonga ON zerver_message
   USING pgroonga(search_pgroonga pgroonga.text_full_text_search_ops);
-""" % database_setting,
+END$$
-                              """
+""", database_setting)],
+                              [("""
+DO $$BEGIN
 SET search_path = %(SCHEMA)s,public,pgroonga,pg_catalog;
 
 DROP INDEX zerver_message_search_pgroonga;
@@ -32,8 +35,9 @@ ALTER TABLE zerver_message DROP COLUMN search_pgroonga;
 
 SET search_path = %(SCHEMA)s,public;
 
-ALTER ROLE %(USER)s SET search_path TO %(SCHEMA)s,public;
+EXECUTE format('ALTER ROLE %%I SET search_path TO %%L,public', %(USER)s, %(SCHEMA)s);
-""" % database_setting),
+END$$
+""", database_setting)]),
         ]
     else:
         operations = []

tools/semgrep.yml

@@ -72,6 +72,8 @@ rules:
       - pattern: ... .execute("...".format(...))
       - pattern: psycopg2.sql.SQL(... % ...)
       - pattern: psycopg2.sql.SQL(... .format(...))
+      - pattern: django.db.migrations.RunSQL(..., ... % ..., ...)
+      - pattern: django.db.migrations.RunSQL(..., "..." .format(...), ...)
     severity: ERROR
     message: "Do not write a SQL injection vulnerability please"