sql: validate RLS policy exemptions for constraints

Unique and foreign key constraints on tables with row-level security
(RLS) enabled are exempt from RLS policies when enforcing constraints.
This exemption was implemented previously. This commit adds tests to
validate that RLS policies do not interfere with constraint enforcement.

Closes #136747

Epic: CRDB-45203
Release note: none

Author: spilchen

pkg/sql/logictest/testdata/logic_test/row_level_security

@@ -1457,6 +1457,241 @@ SET ROLE root
 statement ok
 DROP TABLE force_check CASCADE;
 
+# Test to make sure that the scan to enforce uniqueness is done without RLS policies.
+subtest uniq
+
+statement ok
+CREATE TABLE uniq (rls_col TEXT, uniq_col INT8 UNIQUE);
+
+statement ok
+CREATE USER uniq_user;
+
+statement ok
+GRANT ALL ON uniq TO uniq_user;
+
+statement ok
+ALTER TABLE uniq OWNER TO uniq_user;
+
+statement ok
+SET ROLE uniq_user;
+
+statement ok
+ALTER TABLE uniq NO FORCE ROW LEVEL SECURITY, ENABLE ROW LEVEL SECURITY;
+
+statement ok
+CREATE POLICY access ON uniq USING (rls_col = 'cat');
+
+statement ok
+INSERT INTO uniq VALUES ('cat', 1), ('cat', 2), ('dog', 3), ('cat', 4), ('hamster', 5);
+
+statement ok
+ALTER TABLE uniq FORCE ROW LEVEL SECURITY;
+
+statement error pq: duplicate key value violates unique constraint "uniq_uniq_col_key"\nDETAIL: Key \(uniq_col\)=\(3\) already exists.
+INSERT INTO uniq VALUES ('cat', 3);
+
+statement ok
+INSERT INTO uniq VALUES ('cat', 6);
+
+statement error pq: new row violates row-level security policy for table "uniq"
+INSERT INTO uniq VALUES ('dog', 6);
+
+statement error pq: duplicate key value violates unique constraint "uniq_uniq_col_key"\nDETAIL: Key \(uniq_col\)=\(5\) already exists.
+UPDATE uniq SET uniq_col = 5 WHERE uniq_col = 1;
+
+statement ok
+UPDATE uniq SET uniq_col = 7 WHERE uniq_col = 1;
+
+# Ensure that any attempts to update an invisible row will be a no-op
+query TI
+UPDATE uniq SET uniq_col = 8 WHERE uniq_col = 5 RETURNING rls_col, uniq_col;
+----
+
+statement ok
+ALTER TABLE uniq NO FORCE ROW LEVEL SECURITY;
+
+query TI
+select rls_col, uniq_col FROM uniq ORDER BY uniq_col;
+----
+cat      2
+dog      3
+cat      4
+hamster  5
+cat      6
+cat      7
+
+statement ok
+SET ROLE root;
+
+statement ok
+DROP TABLE uniq;
+
+statement ok
+DROP USER uniq_user;
+
+# Test to make sure that the scan to enforce foreign keys is exempt from RLS policies.
+subtest fk
+
+statement ok
+CREATE TABLE parent (key INT8 NOT NULL PRIMARY KEY);
+
+statement ok
+CREATE TABLE child (
+  rls_col TEXT,
+  key INT8 NOT NULL,
+  CONSTRAINT fk FOREIGN KEY (key) REFERENCES parent(key) ON DELETE CASCADE
+);
+
+statement ok
+CREATE USER fk_user;
+
+statement ok
+GRANT ALL ON parent TO fk_user;
+
+statement ok
+GRANT ALL ON child TO fk_user;
+
+statement ok
+ALTER TABLE parent OWNER TO fk_user;
+
+statement ok
+ALTER TABLE child OWNER TO fk_user;
+
+statement ok
+SET ROLE fk_user;
+
+statement ok
+INSERT INTO parent SELECT * FROM generate_series(1,6);
+
+statement ok
+INSERT INTO child VALUES ('bedroom', 1), ('office', 2)
+
+# Set RLS at the parent and ensure FK still enforced.
+statement ok
+ALTER TABLE parent ENABLE ROW LEVEL SECURITY, FORCE ROW LEVEL SECURITY;
+
+statement error pq: insert on table "child" violates foreign key constraint "fk"
+INSERT INTO child VALUES ('hall', 7);
+
+statement ok
+INSERT INTO child VALUES ('hall', 3);
+
+# mimic the FK lookup to show that the given RLS policies will hide the value
+query I
+SELECT 1 FROM parent WHERE key = 3;
+----
+
+query I
+SELECT key FROM child ORDER BY key;
+----
+1
+2
+3
+
+# Set RLS at the child and ensure FK still enforced
+statement ok
+ALTER TABLE child ENABLE ROW LEVEL SECURITY, FORCE ROW LEVEL SECURITY;
+
+statement ok
+CREATE POLICY ins1 ON child FOR INSERT WITH CHECK (rls_col = 'bedroom');
+
+statement error pq: insert on table "child" violates foreign key constraint "fk"
+INSERT INTO child VALUES ('bedroom', 7);
+
+statement error pq: new row violates row-level security policy for table "child"
+INSERT INTO child VALUES ('deck', 7);
+
+statement ok
+INSERT INTO child VALUES ('bedroom', 4);
+
+# Disable RLS at the parent so that we can do a delete and have it cascade down
+statement ok
+ALTER TABLE parent NO FORCE ROW LEVEL SECURITY;
+
+statement ok
+DELETE FROM parent WHERE key = 1;
+
+statement ok
+CREATE POLICY sel1 ON child FOR SELECT USING (true);
+
+query I
+SELECT key FROM child ORDER BY key;
+----
+2
+3
+4
+
+statement ok
+SET ROLE root
+
+statement ok
+DROP TABLE child;
+
+statement ok
+DROP TABLE parent;
+
+statement ok
+DROP USER fk_user;
+
+# Ensure CHECK constraints can work alongside RLS policies
+subtest check_constraint
+
+statement ok
+CREATE TABLE rgb_only (col text, check (col = 'red' or col = 'green' or col = 'blue'));
+
+statement ok
+CREATE USER rgb_only_user;
+
+statement ok
+ALTER TABLE rgb_only OWNER TO rgb_only_user;
+
+statement ok
+SET ROLE rgb_only_user;
+
+statement ok
+ALTER TABLE rgb_only ENABLE ROW LEVEL SECURITY, FORCE ROW LEVEL SECURITY;
+
+statement ok
+CREATE POLICY p_sel ON rgb_only FOR SELECT USING (true);
+
+statement ok
+CREATE POLICY p_subset ON rgb_only FOR INSERT WITH CHECK (col = 'red' or col = 'brown');
+
+statement ok
+INSERT INTO rgb_only VALUES ('red')
+
+# Allowed by policy, reject by CHECK constraint
+statement error pq: failed to satisfy CHECK constraint \(\(\(col = 'red':::STRING\) OR \(col = 'green':::STRING\)\) OR \(col = 'blue':::STRING\)\)
+INSERT INTO rgb_only VALUES ('brown')
+
+# Disallowed by policy, accepted by CHECK constraint
+statement error pq: new row violates row-level security policy for table "rgb_only"
+INSERT INTO rgb_only VALUES ('green')
+
+statement ok
+DROP POLICY p_subset ON rgb_only;
+
+statement ok
+CREATE POLICY p_disjoint ON rgb_only FOR INSERT WITH CHECK (col = 'black');
+
+# Disallowed by both.
+statement error pq: new row violates row-level security policy for table "rgb_only"
+INSERT INTO rgb_only VALUES ('blue')
+
+query T
+SELECT col FROM rgb_only ORDER BY col;
+----
+red
+
+statement ok
+SET ROLE root;
+
+statement ok
+DROP TABLE rgb_only;
+
+statement ok
+DROP USER rgb_only_user;
+
 subtest truncate
 
 statement ok