The empty layer called 1: a generic GIS schema moved SQL injection into the view builder

The generic schema did not create the injection surface. It relocated it. A table per layer puts DDL behind every "new layer" click and produces a migration story that never ends ^[22]; three tables with a `layer_id` and a JSON attribute column give one schema, one set of indexes, and layers that are only rows in a metadata table ^[1]. For roughly 2.7 million features that is the right trade ^[3]. But the tile server still wants physical objects. Martin discovers spatial tables and views in a schema and publishes each as an MVT endpoint ^[5], and in this deployment it was told to publish views and not tables ^[6]. So something has to turn a metadata row into a view at runtime, on save. Here that something is a Django `post_save` signal on the `Layer` model ^[7], and the string it interpolated into `CREATE OR REPLACE VIEW` was the layer's display name, taken straight from a `CharField` with no validation on it ^[10][11].

The exploit matters less than the empty layer. A layer named `1` cannot be created as an unquoted identifier, Postgres refused, the exception was caught, logged and swallowed, and that layer sat for months serving no tiles while nobody noticed ^[13][14]. The author's own summary of it is exact: a user-supplied string that breaks SQL syntax is the same string that could complete it ^[15]. Look at the detection path, though. Nothing alerted. The tell was an absence, and it was found by accident ^[13]. When a code path manufactures database objects out of user input, the clumsy failure and the hostile success arrive through the same line, so the failure needs to be loud.

The counts are 1,820,288 points, 697,009 lines and 171,830 polygons ^[2], which is 2,689,127 rows across the three tables ^[4], published today through 106 views ^[8]. The number that costs money is 23: the layers whose names contain capital letters ^[17], about 22 percent of the published views ^[21]. Every existing view was created unquoted, so the catalog holds them folded to lower case ^[17]. Start quoting identifiers correctly and `T53_Traffic_Cameras` becomes a second object beside `t53_traffic_cameras`, the old one keeps existing, and Martin keeps publishing both ^[18]. The safe API is not a drop-in. The naming function now has to reproduce what Postgres was doing implicitly, folding only ASCII A through Z, because four layers have Cyrillic names and `str.lower()` would push them away from the names already in the catalog ^[19][20].

That is the bill for pushing per-tenant structure into metadata rows. The view name is derived state that no column owns: computed once from an editable field at creation, re-derived at every lookup, and its correctness defined by 106 rows already written into the system catalog rather than by anything in the model. `psycopg2.sql` closes the injection ^[16]. It does not give the name a home.