oatpp-authkit/README.md

# oatpp-authkit

Header-only C++ library distilled from [fewo-webapp](https://git.uwe-schuster.info/uwe.admin/fewo-webapp)'s
hardened auth / security stack. Header-only, oatpp 1.3+, C++17.

## What's in v0.1 (the clean-lift set)

| Header | Purpose |
|--------|---------|
| `interceptor/SecurityHeadersInterceptor.hpp` | CSP, X-Frame-Options, X-Content-Type-Options, Referrer-Policy, Permissions-Policy. Strict defaults. |
| `interceptor/BodySizeLimitInterceptor.hpp` | Reject request bodies above a configurable limit with 413 before they hit your handlers. |
| `handler/JsonErrorHandler.hpp` | Normalises thrown exceptions into `{status, message}` JSON so controllers never leak raw HTML error pages. |
| `util/RateLimiter.hpp` | In-memory token-bucket keyed on an arbitrary string (typically the client IP from `clientIpTrusted`). |
| `util/TokenExtract.hpp` | `extractToken` (Cookie/Bearer), `isValidIp` (IPv4/IPv6 via `inet_pton`), `clientIpTrusted` (loopback-gated XFF). |
| `startup/RequireEncryptionKey.hpp` | `requireEncryptionKey(envVarName, encryptionEnabled, allowPlaintext)` — refuse startup without a symmetric key unless a dev flag overrides. |
| `repo/Repository.hpp` + `IHistoryRepository.hpp` + `TemporalFieldTraits.hpp` + `TemporalAt.hpp` + `ActorContext.hpp` | Pure-abstract `Repository<TDto>` interface set distilled from fewo-webapp's per-entity `*Db` clients. Mixed UUID allocation on `save`, separate `IHistoryRepository<T>` for temporal versions, `TemporalFieldTraits<T>` to map canonical (entity_id, valid_from, valid_until) onto whatever a DTO actually calls them, `ActorContext` placeholder for the scope-guard decorator. |
| `repo/TemporalRepository.hpp` | Decorator that wraps any `Repository<TDto>` and turns it into a temporally-versioned one. `save` closes the prior live version and inserts a new one; `findByEntityIdAt(id, at)` returns the version live at a point in time; implements `IHistoryRepository<T>`. Inner adapter is expected to expose all rows (live + historical) and treat `save` as upsert keyed by `(entity_id, valid_from)`. DTOs register their three temporal columns via `OATPP_AUTHKIT_REGISTER_TEMPORAL`. |
| `repo/ScopeGuardRepository.hpp` | Generic resource-scope decorator. Takes a `bool(ActorContext, TDto)` predicate at construction; gates every method on it. Throws `ScopeDeniedException` on deny (catchers translate to 403). Knows nothing about consumer-specific concepts like "property" or "tenant" — the predicate decides. |
| `repo/IQueryable.hpp` | Optional capability for repos that resolve a typed query AST. `field<&Dto::col>().eq(...)` style DSL composes via `&&` / `||` / `!`; `Query<TDto>::toSql()` emits parameterised SQL plus a bind bag. Bounded surface — equality, range, IN, LIKE, NULL, ORDER BY, LIMIT/OFFSET. No joins, subqueries, or aggregates. Concrete repos opt in by deriving `IQueryable<TDto>`. |
| `repo/IAuditSink.hpp` + `repo/AuditLogRepository.hpp` | Cross-cutting audit-trail decorator. Emits an `AuditEvent` (actor, entity type/id, op, timestamp) per mutation through a consumer-supplied `IAuditSink`. Ops are `Create` / `Update` / `Delete` / `Read`; pre-write `findByEntityId` lookup distinguishes Create from Update. Configurable enabled-op set (default `{Create,Update,Delete}` — `Read` is opt-in, `list()` never audited). Sink failures are caught and swallowed unless a `bool(const std::exception&)` handler asks to rethrow. Stacks with `TemporalRepository` and `ScopeGuardRepository`. |
| `repo/Prereq.hpp` | Per-decorator migration kit. Each decorator that touches schema bundles its prereq SQL alongside its code: `DecoratorPrereq` for additive (`CREATE TABLE IF NOT EXISTS …`) and `ReshapeStep` for non-idempotent reshape with a `detectSql` probe. `applyDecoratorMigrations<Decorators...>(table, probe, exec, recorder)` walks the listed decorators at startup, runs every PREREQ, runs every reshape step whose probe returns false, optionally records applied steps via `oatpp_authkit_schema_migrations`. Database-agnostic — consumer wires `probe`/`exec` to whatever DbClient they use. |

## Decorator migrations

| Decorator | `PREREQ` | `RESHAPE_STEPS` |
|-----------|----------|------------------|
| `TemporalRepository<T>` | (none) | `add_valid_from`, `add_valid_until`, `drop_unique_entity_id` (consumer-overridable noop), `composite_unique` — composite `UNIQUE(entity_id, valid_until)` so close-then-insert can run inside a deferred-FK transaction. |
| `AuditLogRepository<T>` | `CREATE TABLE IF NOT EXISTS audit_log (…)` — fixed shape, no `{table}` placeholder. | (none) |
| `ScopeGuardRepository<T>` | (none) | (none) |

Wiring it up:

```cpp
#include "oatpp-authkit/repo/Prereq.hpp"

// probe: returns true iff the SQL yields ≥1 row
auto probe = [&](const std::string& sql) { /* run SELECT, return bool */ };
auto exec  = [&](const std::string& sql) { /* run DDL */ };

oatpp_authkit::repo::applyDecoratorMigrations<
    oatpp_authkit::repo::TemporalRepository<PersonDto>,
    oatpp_authkit::repo::AuditLogRepository<PersonDto>>(
    "persons", probe, exec);
```

Re-running on every startup is safe by construction.

## Consume via CMake

```cmake
# FetchContent (pin to a tag):
include(FetchContent)
FetchContent_Declare(oatpp-authkit
    GIT_REPOSITORY https://git.uwe-schuster.info/uwe.admin/oatpp-authkit.git
    GIT_TAG v0.1.0)
FetchContent_MakeAvailable(oatpp-authkit)

target_link_libraries(app PRIVATE oatpp::authkit)
```

Or after `cmake --install`:

```cmake
find_package(oatpp-authkit 0.1 REQUIRED)
target_link_libraries(app PRIVATE oatpp::authkit)
```

## Browser-friendly 401/403

By default `AuthInterceptor` returns `application/json` for every rejection,
which is correct for `/api/*` callers but breaks browser navigation: a user
following a stale link or an expired password-reset URL sees a raw
`{"status":"Unauthorized"}` instead of a real page.

Override `IAuthPolicy::unauthenticatedRedirect(path)` to redirect browser
navigations to a login or landing page while keeping JSON responses for
`fetch`/`axios` callers (detected via path prefix `/api/`,
`X-Requested-With: XMLHttpRequest`, or an `Accept` header that prefers
`application/json`):

```cpp
class AppAuthPolicy : public oatpp_authkit::IAuthPolicy {
public:
    std::optional<std::string>
    unauthenticatedRedirect(const std::string& path) override {
        return "/?next=" + oatpp_authkit::AuthInterceptor::urlEncode(path);
    }
};
```

Returning `std::nullopt` (the default) preserves the legacy JSON behaviour
for all responses.

## Tests

```bash
cmake -B build -DOATPP_AUTHKIT_BUILD_TESTS=ON
cmake --build build
ctest --test-dir build --output-on-failure
```

Tests are off by default so consumers pulling the library in via
`FetchContent` don't pay the cost.

## Roadmap

- **v0.2** — `AuthInterceptor` + `requireAdmin` ported onto three seams
  (`IAuthBackend`, `IAuthPolicy`, `IRuntimeConfig`) so consumers plug in their
  own user store, public-path list, and admin role set without forking the
  interceptor.
- **Later** — session cookie helpers, API-key rotation, re-encryption migration.

See `docs/security-baseline.md` for language-neutral CSP / rate-limit / body-size
constants that non-C++ consumers can re-implement directly.