## TASK-020 — `log_target` accepts arbitrary paths — root file write via fail2ban (CRITICAL)

**Severity:** Critical

### Where found
`backend/app/models/config.py` — `GlobalConfigUpdate.log_target: str | None`. `backend/app/services/config_service.py` — `update_global_config()` forwards the value to fail2ban without validation.

### Why this is needed
fail2ban runs as root. When `log_target` is set to a path, fail2ban opens (and if necessary creates) that file for writing. An authenticated user can send `PUT /api/config/global` with `{"log_target": "/etc/cron.d/bangui-pwned"}`, causing fail2ban to create that file as root. With crafted content appended via fail2ban's own logging, this escalates to a root write primitive and potentially to Remote Code Execution.

### Goal
Block all `log_target` values that are not `"STDOUT"`, `"STDERR"`, `"SYSLOG"`, or a path under the configured allowed log directories.

### What to do
1. **Immediate:** Add a strict `@field_validator("log_target")` to `GlobalConfigUpdate` that enforces the allowlist (see TASK-015 — this task and TASK-015 share the same fix).
2. **Defense in depth:** Before sending the command to fail2ban in `update_global_config()`, validate again at the service layer (not just the model layer).
3. Add a regression test: `POST /api/config/global` with `log_target="/etc/passwd"` must return 422.

### Possible traps and issues
- This must be fixed before TASK-015 since it is the more severe variant. The fixes are identical — implement them together.
- Pydantic model validators run before the service receives the value, but an integration test confirming the full request path is essential.

### Docs changes needed
- `Features.md` — document valid log_target values.
- `Backend-Development.md` — critical input validation requirement for config endpoints.

### Doc references
- [Features.md](Features.md) — fail2ban global configuration
- [Backend-Development.md](Backend-Development.md) — input validation

---

## TASK-021 — `set_jail_config_enabled` and `write_jail_config_file` not atomic

**Severity:** Medium

### Where found
`backend/app/services/raw_config_io_service.py` lines ~268 (`set_jail_config_enabled`) and ~344 (`write_jail_config_file`) — both use `path.write_text(updated)` directly.

### Why this is needed
Same root cause as TASK-018. A process kill mid-write leaves the jail config file corrupted, disabling that jail on next fail2ban reload.

### Goal
Atomic writes for `set_jail_config_enabled` and `write_jail_config_file`.

### What to do
Same as TASK-018: replace `path.write_text(content)` with the `NamedTemporaryFile` + `os.replace()` pattern in both functions. This is most efficiently done as part of TASK-018 by extracting a shared `atomic_write(path, content)` helper in `config_file_helpers.py`.

### Possible traps and issues
- Same as TASK-018.
- Extracting the helper makes TASK-018 and TASK-021 a single coordinated change.

### Docs changes needed
- `Backend-Development.md` — atomic write helper documentation.

### Doc references
- [Backend-Development.md](Backend-Development.md) — file I/O conventions

---

## TASK-022 — Session tokens stored in plaintext in SQLite

**Severity:** High

### Where found
`backend/app/db.py` — `sessions` table schema: `token TEXT NOT NULL UNIQUE`. `backend/app/repositories/session_repo.py` — `INSERT INTO sessions (token, ...)` and `SELECT ... WHERE token = ?` both use the raw token value.

### Why this is needed
If the BanGUI SQLite database file is exposed (volume mount misconfiguration, backup leak, path traversal via another vulnerability), all active session tokens are immediately usable — no cracking required. The attacker can directly use the token in the `bangui_session` cookie or `Authorization: Bearer` header.

### Goal
Store a one-way hash of the session token in the database so that the DB file alone is not sufficient to hijack a session.

### What to do
1. In `session_repo.create_session()`, store `hashlib.sha256(token.encode()).hexdigest()` instead of `token` in the `token` column.
2. In `session_repo.get_session()` and `delete_session()`, hash the supplied token before the SQL lookup.
3. The `Session` model's `token` field returned to the service layer still contains the raw token (for use in signing and response) — only the DB column changes.
4. Add a migration (`_MIGRATIONS[2]`) that renames the existing `sessions` table to `sessions_old`, creates a new one, and drops `sessions_old` (or simply truncates all sessions on upgrade, since they are all compromised anyway once the DB was readable in plaintext).

### Possible traps and issues
- Coordinate with TASK-025 (HMAC bypass) — both fixes invalidate all existing sessions. Do them in the same release.
- The migration must be atomic (see TASK-023).
- The `Session.token` field name is slightly misleading once it stores a hash — consider renaming the DB column to `token_hash`.

### Docs changes needed
- `Architekture.md` — update session data model description.
- `Backend-Development.md` — document the session token hashing pattern.

### Doc references
- [Architekture.md](Architekture.md) — authentication and session model
- [Backend-Development.md](Backend-Development.md) — security patterns

---

## TASK-023 — Database migration is non-atomic

**Severity:** Medium

### Where found
`backend/app/db.py` — `_apply_migration()`: calls `db.executescript(migration_script)` (which auto-commits per SQLite Python driver behavior) and then separately `db.execute("INSERT INTO schema_migrations ...")` + `db.commit()`.

### Why this is needed
`executescript()` issues an implicit `COMMIT` before executing the script, so the schema change and the migration record insertion are in two separate transactions. A process crash between them leaves the database in a migrated-but-unrecorded state. On next startup, the migration is re-applied. For a migration that is not idempotent (e.g., `INSERT` without `OR IGNORE`, `ALTER TABLE ADD COLUMN` without `IF NOT EXISTS`), this causes a runtime error or data duplication.

### Goal
Wrap each migration's DDL and its `schema_migrations` record in a single atomic transaction.

### What to do
1. Replace `db.executescript(migration_script)` with individual `await db.execute(stmt)` calls for each DDL statement in the migration (split on `;`).
2. Wrap the entire migration (all DDL statements + the `INSERT INTO schema_migrations`) in an explicit `BEGIN IMMEDIATE` ... `COMMIT` transaction.
3. Test: verify that a simulated crash mid-migration (mocked `execute` that raises on the second statement) leaves the DB at its prior version.

### Possible traps and issues
- SQLite DDL in WAL mode: `CREATE TABLE IF NOT EXISTS` and `CREATE INDEX IF NOT EXISTS` are safe to re-run. `ALTER TABLE ADD COLUMN` is not — it must be guarded with a `PRAGMA table_info` check if used in future migrations.
- Splitting a migration script on `;` must handle semicolons inside string literals and comments. Consider storing each migration as a `list[str]` of individual statements instead of a single script string.

### Docs changes needed
- `Backend-Development.md` — migration authoring guidelines.

### Doc references
- [Backend-Development.md](Backend-Development.md) — database schema and migrations

---

## TASK-024 — No CSRF protection on state-mutating endpoints

**Severity:** High

### Where found
All `POST`, `PUT`, `DELETE` routes in `backend/app/routers/`. Only `SameSite=Lax` on the session cookie provides any CSRF protection.

### Why this is needed
`SameSite=Lax` blocks cross-site `<form>` POST requests but does **not** block `fetch(..., {credentials: "include"})` initiated by JavaScript on a subdomain or a same-origin XSS injection. Without a CSRF token or `Origin` header check, a compromised subdomain can issue authenticated requests on behalf of the logged-in user.

### Goal
Add explicit CSRF protection for all cookie-authenticated state-mutating endpoints.

### What to do
**Option A (recommended — custom header check):**
1. Add a middleware that, for all `POST`/`PUT`/`DELETE`/`PATCH` requests authenticated via cookie (not `Authorization: Bearer`), requires the presence of a custom header: `X-BanGUI-Request: 1`.
2. The frontend API client (`frontend/src/api/client.ts`) already uses a shared `request()` function — add `"X-BanGUI-Request": "1"` to the default headers there.
3. Cross-site `fetch()` calls cannot set custom headers without CORS preflight, which the backend rejects (CORS is only configured for allowed origins).

**Option B — Origin header validation:**
Add middleware that checks `Origin` or `Referer` matches the configured allowed origin for all mutating requests.

### Possible traps and issues
- The Bearer-token path (`Authorization: Bearer`) does not use cookies and is therefore not CSRF-vulnerable — do not apply the check to those requests.
- Detecting cookie-vs-bearer authentication in middleware requires reading request headers before the auth dependency runs — check for `Cookie: bangui_session=` presence.
- Do not apply CSRF checks to `GET`, `HEAD`, `OPTIONS` requests.

### Docs changes needed
- `Architekture.md` — document the CSRF protection mechanism.
- `Backend-Development.md` — CSRF middleware.
- `Web-Development.md` — document the `X-BanGUI-Request` header requirement.

### Doc references
- [Architekture.md](Architekture.md) — security architecture
- [Backend-Development.md](Backend-Development.md) — security patterns
- [Web-Development.md](Web-Development.md) — API client conventions

---

## TASK-025 — `unwrap_session_token` legacy fallback bypasses HMAC check entirely

**Severity:** High

### Where found
`backend/app/services/auth_service.py` — `unwrap_session_token()` lines 44–49:
```python
if SESSION_TOKEN_SIGNATURE_SEPARATOR not in token:
    return token  # HMAC check skipped entirely
```

### Why this is needed
Any token that does not contain the separator character is returned unchanged as a "valid" token — the HMAC signature is never verified. Combined with TASK-022 (plaintext DB), an attacker who reads the database can take a raw token (no separator) and use it directly, bypassing the HMAC layer entirely. The signing mechanism provides zero additional security once the DB is readable.

### Goal
Remove the HMAC bypass. All tokens must carry a valid signature.

### What to do
1. Remove the early-return branch: `if SESSION_TOKEN_SIGNATURE_SEPARATOR not in token: return token`.
2. If the separator is absent, raise `ValueError("Invalid session token.")`.
3. This invalidates all sessions created before HMAC signing was introduced — coordinate with TASK-022 (all sessions should be invalidated during that migration anyway).
4. Update all tests that use raw unsigned tokens.

### Possible traps and issues
- Any test that constructs a raw token without a signature will start failing — this is intentional, update the tests.
- The `unwrap_session_token` docstring mentions "backward compatibility with existing raw session tokens stored in the DB" — remove this rationale once TASK-022 hashes the DB column (raw tokens will no longer be in the DB).

### Docs changes needed
- `Backend-Development.md` — document the session token format (signed only).

### Doc references
- [Backend-Development.md](Backend-Development.md) — authentication internals

---

## TASK-026 — OpenAPI docs (`/docs`, `/redoc`) exposed without authentication in production

**Severity:** Medium

### Where found
`backend/app/main.py` — `FastAPI(title="BanGUI", ...)` with no `docs_url`, `redoc_url`, or `openapi_url` override.

### Why this is needed
FastAPI serves interactive API documentation at `/docs` (Swagger UI) and `/redoc` by default, accessible to any unauthenticated user. These pages expose every endpoint URL, all request and response schemas, and allow direct API invocation from the browser. An attacker can enumerate all available routes, understand input/output models, and attempt attacks without any prior knowledge of the API.

### Goal
Disable API docs in production, or protect them behind authentication.

### What to do
1. Add a `BANGUI_ENABLE_DOCS: bool = Field(default=False, ...)` setting to `Settings`.
2. In `create_app()`:
   ```python
   docs_url = "/api/docs" if resolved_settings.enable_docs else None
   redoc_url = "/api/redoc" if resolved_settings.enable_docs else None
   openapi_url = "/api/openapi.json" if resolved_settings.enable_docs else None
   app = FastAPI(..., docs_url=docs_url, redoc_url=redoc_url, openapi_url=openapi_url)
   ```
3. In `compose.debug.yml`, set `BANGUI_ENABLE_DOCS: "true"`.
4. Production (`compose.prod.yml`) leaves `BANGUI_ENABLE_DOCS` unset (defaults to `false`).

### Possible traps and issues
- The `SetupRedirectMiddleware` must allow `/api/docs` and `/api/openapi.json` in `_ALWAYS_ALLOWED` (or behind auth — a protected docs endpoint requires a custom Starlette route with `require_auth`).
- If you want protected docs (only accessible when logged in), use a custom route that returns the Swagger HTML after `require_auth`.

### Docs changes needed
- `Backend-Development.md` — document the `BANGUI_ENABLE_DOCS` flag.

### Doc references
- [Backend-Development.md](Backend-Development.md) — configuration options

---

## TASK-027 — Debug compose hardcodes a publicly known weak session secret

**Severity:** Medium

### Where found
`Docker/compose.debug.yml` line ~63:
```yaml
BANGUI_SESSION_SECRET: "${BANGUI_SESSION_SECRET:-dev-secret-do-not-use-in-production}"
```

### Why this is needed
The fallback value `dev-secret-do-not-use-in-production` is now publicly visible in the repository. If `compose.debug.yml` is used in any environment where `BANGUI_SESSION_SECRET` is not set (e.g., a CI environment or a staging server that uses the debug compose file), all session tokens can be forged by anyone who has seen this repository.

### Goal
Remove the insecure default. Require the secret to be set explicitly before the container starts.

### What to do
1. Change to `BANGUI_SESSION_SECRET: "${BANGUI_SESSION_SECRET:?BANGUI_SESSION_SECRET must be set — generate with: python -c 'import secrets; print(secrets.token_hex(32))'}"`.
2. Create a `.env.example` file at the project root with placeholder values and generation instructions.
3. Add `.env` to `.gitignore` (verify it is already there).

### Possible traps and issues
- This will break `docker compose -f Docker/compose.debug.yml up` without a `.env` file. Add a clear error message and setup instructions to the README or `Instructions.md`.
- `docker-compose.yml` (the legacy file) already uses the `:?` pattern — follow the same approach.

### Docs changes needed
- `Instructions.md` — add first-run setup instructions for the `.env` file.

### Doc references
- [Instructions.md](Instructions.md) — developer setup

---

## TASK-028 — Fire-and-forget `asyncio.create_task()` silently discards exceptions

**Severity:** Low

### Where found
`backend/app/services/ban_service.py` line ~614:
```python
asyncio.create_task(  # noqa: RUF006
    geo_cache.lookup_batch(uncached, http_session, db=app_db),
    name="geo_bans_by_country",
)
```

### Why this is needed
The task reference is immediately discarded. Any exception raised inside `geo_cache.lookup_batch()` — network errors, aiohttp timeouts, DB write failures — becomes an unhandled task exception. In Python 3.11+ this emits a `RuntimeWarning` to stderr but is otherwise silently swallowed. Errors in background geo resolution are invisible in structured logs.

### Goal
Ensure exceptions in fire-and-forget tasks are always logged.

### What to do
1. Wrap the task body in a logging wrapper:
   ```python
   async def _logged_task(coro: Coroutine[Any, Any, Any], name: str) -> None:
       try:
           await coro
       except Exception:
           log.exception("background_task_failed", task_name=name)
   
   asyncio.create_task(_logged_task(geo_cache.lookup_batch(...), "geo_bans_by_country"))
   ```
2. Extract `_logged_task` into `backend/app/utils/async_utils.py` as a reusable helper so the same pattern is used for all fire-and-forget tasks.

### Possible traps and issues
- The done callback must not re-raise the exception — only log it.
- `log.exception()` inside a callback/task captures the traceback automatically with structlog.

### Docs changes needed
- `Backend-Development.md` — fire-and-forget task conventions.

### Doc references
- [Backend-Development.md](Backend-Development.md) — async patterns

---

## TASK-029 — `Fail2BanConnectionError` leaks socket path in HTTP error responses

**Severity:** Medium

### Where found
`backend/app/exceptions.py` — `Fail2BanConnectionError.__init__()` formats the message as `f"{message} (socket: {socket_path})"`. `backend/app/main.py` — `_fail2ban_connection_handler()` returns `{"detail": f"Cannot reach fail2ban: {exc}"}` verbatim.

### Why this is needed
Every 502 response caused by fail2ban being unreachable includes the full socket path (e.g., `Cannot reach fail2ban: [Errno 2] No such file or directory (socket: /var/run/fail2ban/fail2ban.sock)`) in the JSON error body. This discloses internal infrastructure details to unauthenticated users who can trigger the error. Similarly, `_fail2ban_protocol_handler` includes raw exception details that may expose internal parsing logic.

### Goal
Return generic, user-friendly error messages in HTTP responses. Log full details server-side only.

### What to do
1. In `_fail2ban_connection_handler()`, replace:
   ```python
   content={"detail": f"Cannot reach fail2ban: {exc}"}
   ```
   with:
   ```python
   content={"detail": "Cannot reach the fail2ban service. Check the server status page."}
   ```
2. In `_fail2ban_protocol_handler()`, similarly return a generic message.
3. Both handlers already log `error=str(exc)` server-side — this is correct and should remain.

### Possible traps and issues
- Update any tests that assert the exact `detail` string in 502 responses.
- If the frontend displays this error message directly to the user, ensure it still makes sense after genericizing.

### Docs changes needed
- `Backend-Development.md` — error message hygiene (no internal paths/details in responses).

### Doc references
- [Backend-Development.md](Backend-Development.md) — error handling

---

## TASK-030 — ip-api.com geo lookups use plain HTTP — IP addresses sent unencrypted

**Severity:** Medium

### Where found
`backend/app/services/geo_cache.py` lines ~41–46:
```python
_API_URL = "http://ip-api.com/json/{ip}?fields=..."
_BATCH_API_URL = "http://ip-api.com/batch?fields=..."
```

### Why this is needed
All banned and monitored IP addresses are transmitted to ip-api.com in cleartext over HTTP. These are potentially sensitive data (PII under GDPR/CCPA — IP addresses identify users). Any network path between the BanGUI server and ip-api.com's servers can observe or modify the traffic. Forged responses would corrupt the geo database silently.

### Goal
Use encrypted transport for all geo API calls, or switch to a local resolver.

### What to do
ip-api.com's free tier does not support HTTPS. The recommended approach:
1. Promote the existing `geoip_db_path` setting (MaxMind GeoLite2-Country MMDB) to the **primary** resolver.
2. Use ip-api.com as a secondary fallback only when the MMDB is unavailable or returns no result.
3. Add documentation and compose file examples for downloading and mounting the GeoLite2 MMDB.
4. If ip-api.com HTTP is retained as a fallback, add a config flag `BANGUI_GEOIP_ALLOW_HTTP_FALLBACK` (default `false`) and warn clearly at startup when enabled.

### Possible traps and issues
- The MaxMind GeoLite2 database requires a free account and a license key to download — document the setup process.
- The GeoLite2-Country MMDB does not include ASN or organisation data — these fields will be `null` when using the local resolver. The `GeoInfo` model must handle nullable `asn` and `org`.

### Docs changes needed
- `Features.md` — document the geo resolution mechanism and MMDB setup.
- `Architekture.md` — update the external API dependency section.
- `Backend-Development.md` — configuration for `geoip_db_path`.

### Doc references
- [Features.md](Features.md) — geolocation
- [Architekture.md](Architekture.md) — external API dependencies

---

## TASK-031 — bcrypt 72-byte truncation not enforced — long passwords silently equivalent to their prefix

**Severity:** Medium

### Where found
`backend/app/models/auth.py` — `LoginRequest.password: str = Field(...)` (no `max_length`). `backend/app/models/setup.py` — `SetupRequest.master_password` has `min_length=8` but no `max_length`.

### Why this is needed
bcrypt silently truncates all input at 72 bytes before hashing. A user who sets a 100-character password can be authenticated by supplying only the first 72 characters. The extra characters provide no additional security. An attacker who has reduced the search space to 72 characters can brute-force the password more efficiently than the user intended.

### Goal
Enforce a maximum password length of 72 bytes, or pre-hash before bcrypt to remove the limit entirely.

### What to do
**Option A (simple):**
1. Add `max_length=72` to `SetupRequest.master_password` and `LoginRequest.password`.
2. Update the setup wizard UI to reflect the 72-character maximum.

**Option B (removes the 72-byte limit entirely):**
1. Pre-hash the password with HMAC-SHA256 using the `session_secret` as the key before passing to bcrypt:
   ```python
   pre_hashed = hmac.new(secret.encode(), password.encode(), hashlib.sha256).digest()
   bcrypt.hashpw(pre_hashed, bcrypt.gensalt())
   ```
2. Apply consistently in both `run_setup()` and `_check_password()`.

Option A is recommended as the simpler, lower-risk fix. Option B is architecturally cleaner but requires a stored hash migration.

### Possible traps and issues
- Option A: Users who already have passwords longer than 72 characters will need to reset. For a single-admin app this is acceptable.
- Option B: If the `session_secret` changes, all stored password hashes become invalid (since the pre-hash key changes). This is a hidden coupling — document it explicitly.

### Docs changes needed
- `Features.md` — document the password length constraint.
- `Backend-Development.md` — bcrypt usage notes.

### Doc references
- [Features.md](Features.md) — authentication and setup
- [Backend-Development.md](Backend-Development.md) — password hashing

---

## TASK-032 — `geo_cache` table grows unboundedly — no eviction or purge

**Severity:** Medium

### Where found
`backend/app/repositories/geo_cache_repo.py` — has `upsert_entry`, `bulk_upsert_entries`, `upsert_neg_entry` — but **no DELETE functions**. `backend/app/db.py` — `geo_cache` table has no `last_seen` or `created_at` column.

### Why this is needed
Every unique IP address ever seen by fail2ban gets a row in `geo_cache`. The table is never trimmed. A BanGUI instance monitoring a busy server can accumulate millions of rows over months, increasing the DB file size and degrading query performance on every geo lookup.

### Goal
Implement a retention policy that prunes geo cache entries not referenced recently.

### What to do
1. Add a migration (`_MIGRATIONS[2]`) that adds a `last_seen TEXT NOT NULL DEFAULT CURRENT_TIMESTAMP` column to `geo_cache`.
2. Update `upsert_entry` and `bulk_upsert_entries` to set `last_seen = CURRENT_TIMESTAMP` on every upsert.
3. Add `delete_stale_entries(db: aiosqlite.Connection, cutoff_iso: str) -> int` to `geo_cache_repo.py`.
4. Create `backend/app/tasks/geo_cache_cleanup.py` — a nightly task that calls `delete_stale_entries` with a 90-day cutoff.
5. Register the task in `startup_shared_resources`.

### Possible traps and issues
- Adding a column requires a migration. Coordinate with TASK-023 (migration atomicity) and TASK-022 (session hash migration) — all three migrations must be sequenced correctly as `_MIGRATIONS[2]`, `[3]`, etc.
- IPs that have not been seen in 90 days will lose their geo data — on their next appearance they will be re-resolved from ip-api.com or the MMDB. This is acceptable.

### Docs changes needed
- `Architekture.md` — update the `geo_cache` table description and add the cleanup task.
- `Backend-Development.md` — document the geo cache retention policy.

### Doc references
- [Architekture.md](Architekture.md) — application database schema
- [Backend-Development.md](Backend-Development.md) — background tasks

---

## TASK-033 — Session token returned in JSON body alongside HttpOnly cookie

**Severity:** Medium

### Where found
`backend/app/routers/auth.py` — `login()` returns `LoginResponse(token=signed_token, expires_at=expires_at)` in the JSON body **and** sets the HttpOnly cookie. `backend/app/models/auth.py` — `LoginResponse.token` field.

### Why this is needed
The `LoginResponse` JSON body contains the full signed session token. JavaScript running on the page (including third-party analytics scripts or a future XSS injection) can read the response body from a `fetch()` call and store the token in `localStorage` or a non-HttpOnly cookie. The Bearer-header authentication path (`Authorization: Bearer <token>`) then allows using that extracted token, completely bypassing the protections provided by the HttpOnly cookie.

### Goal
Prevent the session token from being accessible to JavaScript when using cookie-based authentication.

### What to do
1. For browser SPA consumers: Remove the `token` field from `LoginResponse`. The HttpOnly cookie is the only token the browser needs.
2. If an API-first (non-browser) token flow is required, create a separate endpoint `POST /api/auth/token` that returns a token in the body and does **not** set a cookie. Document this endpoint as "for programmatic API clients only, not for browser use".
3. Update the frontend — verify that `AuthProvider` does not use `response.token` (confirmed: it currently does not).

### Possible traps and issues
- Any existing API client that relies on the token in the `LoginResponse` body will break. Check tests.
- The `expires_at` field in `LoginResponse` is useful for the frontend to know when to prompt for re-login — this can remain.
- The Bearer-token path in `require_auth` (`Authorization: Bearer`) remains functional for programmatic clients using the dedicated token endpoint.

### Docs changes needed
- `Features.md` — document the authentication flow (cookie for browser, token endpoint for API clients).
- `Backend-Development.md` — authentication endpoint design.
- `Web-Development.md` — document that the frontend uses only the HttpOnly cookie.

### Doc references
- [Features.md](Features.md) — authentication
- [Backend-Development.md](Backend-Development.md) — auth router design
- [Web-Development.md](Web-Development.md) — AuthProvider