oatpp-authkit

Header-only C++ library distilled from 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.

Consume via 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:

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):

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

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.