SQLVerifier admits a tautology hidden in a MySQL executable comment, and queries on tables outside the declared schema

Impact

SQLVerifier.verify_sql admits two kinds of query that its own checks would reject in plain form. This affects every caller that gates on admission_decision, including POST /verify/sql.

1. MySQL executable comments. With dialect="mysql", a tautology inside /*!NNNNN ... */ is not seen, and the query comes back VERIFIED, is_valid: true, ADMIT, with no issues. The same query without the comment is caught as injection_tautology. MySQL and MariaDB execute the contents of executable comments, so the query returns every row. This is the same class of bug as GHSA-q8r4-6gpp-5fx2 in qwed-finance's QueryGuard.
2. Tables outside the schema. When schema_ddl declares the allowed tables, a query on another table is recorded as schema_table_missing, but is_valid stays true and admission is ADMIT. The same applies to a UNION that reads an undeclared table. The schema check reports the violation without affecting the decision.

Reproduction (qwed 7.2.2, main 3e91f12)

from qwed_new.core.sql_verifier import SQLVerifier
from qwed_new.core.diagnostics import admission_decision

ddl = "CREATE TABLE users (id INT, name TEXT, role TEXT)"
cases = [
    ("SELECT * FROM users WHERE id = 1 /*!50000 OR 1=1 */", "mysql"),           # VERIFIED True ADMIT, issues []
    ("SELECT * FROM users WHERE id = 1 OR 1=1", "mysql"),                       # VERIFIED False BLOCKED, injection_tautology
    ("SELECT id FROM secrets", "postgres"),                                     # VERIFIED True ADMIT, schema_table_missing
    ("SELECT id FROM users WHERE id = 1 UNION SELECT id FROM secrets", "postgres"),  # VERIFIED True ADMIT
]
for query, dialect in cases:
    r = SQLVerifier().verify_sql(query, ddl, dialect)
    print(r.status.value, r.developer_fields["is_valid"], admission_decision(r).value)

Patches

Fixed in 7.2.3:

• MySQL and MariaDB executable comments (/*! ... */, /*!NNNNN ... */, /*M! ... */) are expanded before analysis, whatever the declared dialect, so SQL inside them is checked. developer_fields.executable_comments_expanded records when this happened.
• With schema_ddl, a table outside the declared schema is an admission failure: is_valid: false, constraint sql_verifier.schema_violation. Names defined by the query itself (CTEs) are not treated as tables; without schema_ddl, tables are not checked.

Workarounds

Until you upgrade:

• Reject queries that contain /*! before calling verify_sql.
• Treat schema_table_missing in developer_fields.issues as a reason not to run the query.

Credit

Found by the soundness eval (#439) while writing its SQL cases.