refactor: Finalize App-Layer Auth Pivot & Deprecate Legacy DDL

[KinshukSS2]

refactor: Finalize App-Layer Auth Pivot & Deprecate Legacy DDL

What Problem Does This Fix?

PRs 1–4 progressively pivoted from PostgreSQL LOGIN roles to Application-Layer Credentials (passlib/bcrypt in sensorthings."User"). Users no longer have individual PostgreSQL login roles - they are pure application-layer entities.

This branch finalizes the transition to Application-Layer Credentials. It safely deprecates the legacy PostgreSQL DDL commands from the prior architecture, ensuring that all database interactions are perfectly aligned with the new, stateless application-layer identity model.

This branch fixes all of it.

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Changes

1. functions.py::set_role() — Rewritten

Before: SET ROLE "alice" — targets a non-existent per-user PG role.
After: SET LOCAL ROLE "user" — maps the application role to its PostgreSQL group role using DB_ROLE_BY_RBAC_ROLE from rbac_roles.py.

Role mapping:

App Role	PG Group Role
viewer	user
editor	user
obs_manager	sensor
sensor	sensor
custom	user
administrator	administrator

SET LOCAL ROLE is transaction-scoped: it automatically reverts on COMMIT or ROLLBACK, including implicit rollback from async generator cancellation. This eliminates the entire class of pool-leak bugs from the old RESET ROLE pattern.

2. RESET ROLE — Deleted (72 instances, 41 files)

All 72 await connection.execute("RESET ROLE;") calls have been deleted across every endpoint file. With SET LOCAL ROLE, they are not just redundant — they were actively dangerous: in the streaming read path, RESET ROLE could be skipped if the client disconnected mid-stream, returning a connection with an elevated group role to the pool.

Files affected: all create/, delete/, update/, read/ endpoint files.

3. password_crud.py — DDL Removed

Before:

1. asyncpg.connect(user=username, password=current_password) — connects as the user to verify
2. ALTER USER {username} WITH ENCRYPTED PASSWORD '...' — DDL requiring CREATEROLE

After:

1. pwd_context.verify(current_password, stored_hash) — bcrypt verify against User.password (using the existing passlib dependency established in PR 3; no new hashing libraries introduced)
2. UPDATE sensorthings."User" SET password = $1 WHERE id = $2 — parameterised DML
3. Legacy fallback: if User.password IS NULL (pre-migration), falls back to get_auth_connection() for pg_authid verification, then writes the bcrypt hash (completing JIT migration)

4. role_crud.py — REVOKE/GRANT Removed

Before: After updating User.role, the code issued REVOKE {old_pg_role} FROM {username} and GRANT {new_pg_role} TO {username}.
After: Role reassignment is a pure UPDATE sensorthings."User" SET role = $1. set_role() maps the role to its PG group role dynamically at request time — no DDL membership changes needed.

5. update/user.py — REVOKE/GRANT Removed (found during post-audit)

update/user.py lines 119–135 contained a live REVOKE/GRANT block that was missed by the initial cleanup pass (it was in the general PATCH /Users endpoint, not in db/role_crud.py). Fixed in the follow-up commit. Unused get_db_role_for_rbac and pg_quote_ident imports also removed.

6. create/policy.py, update/policy.py — Dead try/finally Removed

The RESET ROLE deletion left dangling if role_switched: pass blocks inside finally: clauses, causing IndentationError. Cleaned up by removing the entire role_switched / try/finally pattern.

7. Test Suite Aligned (5 files)

File	Change
test_set_role_sql_safety.py	Asserts SET LOCAL ROLE "user" for viewer, group mapping for all roles
test_rbac_set_role_safety.py	Parametrised: 5 app roles → correct PG group roles
test_password_update.py	test_success_executes_update_with_hash replaces test_success_executes_alter_user
test_role_reassignment.py	test_different_pg_group_still_no_ddl replaces test_different_pg_role_triggers_revoke_grant
test_policy_role_switch.py	Asserts SET LOCAL ROLE "administrator", asserts zero RESET ROLE

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Test Results

63 passed, 7 warnings in 0.61s

Pre-existing failures (not introduced by this PR):
test_oauth_connection_leak.py — 12 tests use pytest.mark.asyncio but pytest-asyncio is not installed. These tests document a real concern (authenticate_user() still uses a raw asyncpg.connect() for the login flow) that should be addressed separately.

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Files Changed

50 files changed, 303 insertions(+), 461 deletions(-)

• api/app/v1/endpoints/functions.py — set_role() rewrite
• api/app/db/password_crud.py — DDL eradication
• api/app/db/role_crud.py — DDL eradication
• api/app/v1/endpoints/update/user.py — missed REVOKE/GRANT fix
• api/app/v1/endpoints/create/policy.py — dead try/finally cleanup
• api/app/v1/endpoints/update/policy.py — dead try/finally cleanup
• api/app/v1/endpoints/{create,delete,update,read}/*.py (44 files) — RESET ROLE deletion
• api/tests/test_*.py (5 files) — test alignment

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Security Posture After This PR

• Zero DDL privileges required by the ISTSOS_ADMIN service account for any user-management operation
• Zero session-scoped role state can leak between requests via the connection pool
• Zero individual PostgreSQL login roles are referenced anywhere in application code
• The codebase is now architecturally ready for Week 3: adding set_config('app.user_id', ...) to set_role() for per-row RLS enforcement is a 2-line addition with zero structural changes required