Ekklesia/core/src/identity/runtime.ts

import {
  ANONYMOUS_PRINCIPAL,
  createAuthenticatedPrincipal,
  type EkklesiaPrincipal,
} from "@ekklesia/contracts";
import { betterAuth, type BetterAuthOptions } from "better-auth";
import { drizzleAdapter } from "better-auth/adapters/drizzle";
import { getCookies } from "better-auth/cookies";
import { sql } from "drizzle-orm";
import type { IdentityConfig } from "./config.js";
import type { IdentityDrizzleDatabase } from "./database.js";
import { ekklesiaCoreSession, identityAdapterSchema } from "./schema.js";

export type IdentityRuntimeErrorCode =
  | "AUTH_REQUEST_FAILED"
  | "IDENTITY_CONSTRUCTION_FAILED"
  | "PRINCIPAL_RESOLUTION_FAILED";

const runtimeErrorMessages: Readonly<Record<IdentityRuntimeErrorCode, string>> = Object.freeze({
  AUTH_REQUEST_FAILED: "The identity authentication request could not be handled.",
  IDENTITY_CONSTRUCTION_FAILED: "The identity runtime could not be constructed.",
  PRINCIPAL_RESOLUTION_FAILED: "The request principal could not be resolved.",
});

const identityDatabaseProbeTimeoutMs = 3_000;

/**
 * The one header name Better Auth's own client-address resolution (`advanced.ipAddress.
 * ipAddressHeaders`) is configured to trust — never `X-Forwarded-For`, `Forwarded`,
 * `CF-Connecting-IP`, `X-Real-IP`, or any other caller-reachable header. Core never reinterprets an
 * untrusted proxy header itself: `apps/api`'s transport boundary (`apps/api/src/client-address.ts`)
 * is the only writer, resolving the real socket peer (direct mode) or a chain walked against an
 * explicitly configured trusted-proxy set (proxy mode) before overwriting any externally supplied
 * copy of this exact header with its own server-derived result. Better Auth is configured to trust
 * only this one synthesized value, never a second, competing header name.
 */
export const TRUSTED_CLIENT_ADDRESS_HEADER = "x-ekklesia-client-address";

/**
 * A fixed, generic replacement for whatever Better Auth actually logged. Better Auth's own log
 * call sites are not a stable contract Core can audit line by line, and several of them pass a
 * raw internal exception or interpolate user-controlled input directly into the message (for
 * example the origin-check middleware logs `Invalid origin: ${originHeader}`). Rather than trying
 * to sanitize Better Auth's message/argument payload case by case, the payload is dropped
 * entirely and only this fixed string is ever written.
 */
const sanitizedBetterAuthLogMessage = "[identity] Better Auth reported an error.";

/**
 * Explicitly replaces Better Auth's default logger so its own message text and arguments — which
 * may include a raw exception, SQL, a connection string, a host/port, a filesystem path, a
 * session token, a password, or a user-controlled origin/referer header — are never written
 * anywhere. Only the fixed, generic message above is ever emitted, and only for error-level
 * events; this is deliberately not just "quiet under NODE_ENV=test": the same replacement applies
 * in every environment, so production logging is exactly as sanitized as test logging.
 */
function sanitizedBetterAuthLogger(level: string): void {
  if (level === "error") {
    console.error(sanitizedBetterAuthLogMessage);
  }
}

/** Never carries the underlying Better Auth error, database error, cause, stack, secret, or URL. */
export class IdentityRuntimeError extends Error {
  readonly code: IdentityRuntimeErrorCode;

  constructor(code: IdentityRuntimeErrorCode) {
    super(runtimeErrorMessages[code]);
    this.name = "IdentityRuntimeError";
    this.code = code;
    this.stack = `${this.name}: ${this.message}`;
    Object.freeze(this);
  }
}

export interface IdentityRateLimitOverride {
  readonly max?: number;
  readonly window?: number;
}

export interface CreateIdentityRuntimeOptions {
  readonly config: IdentityConfig;
  readonly db: IdentityDrizzleDatabase;
  /**
   * A narrow, explicit override for the sign-in/sign-up rate-limit window used only by test
   * composition that issues many such requests quickly. Rate limiting itself is always enabled;
   * production composition must leave this unset so Better Auth's own strict built-in default
   * (3 requests / 10 seconds on sign-in and sign-up) applies unmodified.
   */
  readonly rateLimitOverride?: IdentityRateLimitOverride;
}

/**
 * Deliberately narrow: exposes exactly two Fetch-standard capabilities and nothing else. It never
 * returns the Better Auth instance, `auth.api`, inferred user/session types, the Drizzle adapter,
 * the database, a session token, cookie contents, a password hash, or Better Auth configuration.
 */
export interface EkklesiaIdentityRuntime {
  /** Delegates directly to Better Auth's Fetch handler. Normal Better Auth HTTP responses
   * (including its own 4xx error responses) pass through unmodified; only a genuinely unexpected
   * failure is converted to a sanitized `IdentityRuntimeError`. */
  handleAuthRequest(request: Request): Promise<Response>;
  /** Resolves the caller's Ekklesia principal from request headers. Returns the anonymous
   * principal for a missing, expired, revoked, or malformed session — never for an infrastructure
   * failure, which instead throws a sanitized `IdentityRuntimeError`. */
  resolvePrincipal(headers: Headers): Promise<EkklesiaPrincipal>;
}

async function withTimeout<T>(operation: Promise<T>, timeoutMs: number): Promise<T> {
  let timer: ReturnType<typeof setTimeout> | undefined;
  try {
    return await Promise.race([
      operation,
      new Promise<never>((_resolve, reject) => {
        timer = setTimeout(() => reject(new Error("timed out")), timeoutMs);
      }),
    ]);
  } finally {
    clearTimeout(timer);
  }
}

/**
 * Whether the caller actually presented *the* configured Better Auth session cookie — not merely
 * some cookie. An arbitrary anonymous cookie (`Cookie: x=y`) is not evidence that Better Auth ever
 * attempted to resolve an Ekklesia session, so it must never trigger session-store work.
 *
 * Parsing deliberately mirrors RFC 6265's `cookie-string` grammar the same way Better Auth's own
 * parser does: split on `;`, take each pair's name as the text before its first `=`, and trim
 * surrounding whitespace. Matching is an exact, whole-name string comparison — never `includes`, a
 * substring test, or an unanchored regular expression — so `better-auth.session_token_x`,
 * `x_better-auth.session_token`, a differently-cased spelling, and a percent-encoded lookalike are
 * all correctly *not* the session cookie (cookie names are case-sensitive per RFC 6265 §4.1.1, and
 * cookie names are never percent-decoded).
 *
 * Ambiguity fails safe *towards* checking rather than away from it: a duplicated session-cookie
 * name still reports `true`, because reporting `false` is what would let a genuinely broken
 * session store be reported as an anonymous request. Returning `true` never grants access on its
 * own — it only means the readiness check runs and Better Auth's own result still governs.
 */
export function hasConfiguredSessionCookie(headers: Headers, cookieName: string): boolean {
  const cookieHeader = headers.get("cookie");
  if (cookieHeader === null) {
    return false;
  }
  for (const pair of cookieHeader.split(";")) {
    const separatorIndex = pair.indexOf("=");
    const name = (separatorIndex === -1 ? pair : pair.slice(0, separatorIndex)).trim();
    if (name === cookieName) {
      return true;
    }
  }
  return false;
}

/**
 * Whether the actual Better Auth session store is usable — not merely whether PostgreSQL can
 * execute a trivial statement.
 *
 * The previous `select 1` probe proved only that *a* connection could run *a* query, so a missing
 * session relation, a drifted/absent column, or a revoked `SELECT` privilege all still looked
 * "reachable", and Better Auth's ambiguous `null` was then reported as a genuinely anonymous
 * request. This instead plans a real read of the exact session relation and the exact columns the
 * adapter depends on, under a `where false` predicate: PostgreSQL still resolves the relation,
 * every named column, and the caller's `SELECT` privilege at plan time, while guaranteeing zero
 * rows are matched, read, or returned — so no session row, token, or user id can ever be
 * enumerated, logged, or exposed by the check itself.
 *
 * Uses the injected Identity Drizzle view (the API's one shared pool); it never constructs another
 * pool, client, connection string, or Drizzle instance. The bounded `withTimeout` guarantees the
 * public response is never blocked by a hung query, and `clearTimeout` in its `finally` leaves no
 * timer behind.
 */
async function probeSessionStore(db: IdentityDrizzleDatabase): Promise<boolean> {
  try {
    await withTimeout(
      db
        .select({
          expiresAt: ekklesiaCoreSession.expiresAt,
          id: ekklesiaCoreSession.id,
          token: ekklesiaCoreSession.token,
          userId: ekklesiaCoreSession.userId,
        })
        .from(ekklesiaCoreSession)
        .where(sql`false`),
      identityDatabaseProbeTimeoutMs,
    );
    return true;
  } catch {
    // Deliberately swallowed: the caught value may carry raw SQL, a relation/column name, a
    // driver detail, a host/port, or a stack. The caller converts `false` into the fixed,
    // sanitized `PRINCIPAL_RESOLUTION_FAILED` contract instead.
    return false;
  }
}

function constructBetterAuth<T>(build: () => T): T {
  try {
    return build();
  } catch {
    throw new IdentityRuntimeError("IDENTITY_CONSTRUCTION_FAILED");
  }
}

/**
 * Core's Better Auth composition boundary and Fetch-compatible identity transport. Constructs
 * Better Auth explicitly from injected, already-validated configuration and an injected Drizzle
 * database — it never reads environment variables and enables no provider or plugin beyond the
 * four core models and email/password sign-up/sign-in required for this slice.
 */
export function createIdentityRuntime(
  options: CreateIdentityRuntimeOptions,
): EkklesiaIdentityRuntime {
  const rateLimitOverride = options.rateLimitOverride;

  // One options object feeds both `betterAuth()` and `getCookies()` below, so the session-cookie
  // name this runtime detects is derived from the exact same configuration Better Auth itself
  // uses. That makes drift structurally impossible rather than merely tested: there is no second
  // hard-coded copy of the cookie name (or of the `__Secure-` prefix rule the configured HTTPS
  // `baseURL` implies) anywhere in this repository.
  const betterAuthOptions = {
    advanced: {
      // Better Auth's own default is environment-sensitive: `skipOriginCheck` falls back to
      // `true` whenever `isTest()` is true (NODE_ENV=test, which Vitest sets, or TEST=1) unless
      // `disableOriginCheck` is explicitly set — and origin skip in turn also silently skips
      // CSRF validation as long as `disableCSRFCheck` is left unset (Better Auth's documented
      // backward-compatibility coupling). Left implicit, this means origin/CSRF protection is
      // silently *off* under the test runner and *on* in production: the exact same code path
      // behaves differently in the two places it matters most to verify. Setting both flags to
      // `false` explicitly removes the `isTest()` branch entirely, so the identical protection
      // is enforced in every environment, including under Vitest.
      disableCSRFCheck: false,
      disableOriginCheck: false,
      // The pinned release's own client-address resolution (`getIp`, `@better-auth/core/utils/
      // ip`) only ever reads request headers — it has no way to see the actual TCP socket peer.
      // Restricting `ipAddressHeaders` to exactly one platform-owned header name, rather than
      // leaving it on Better Auth's own default (`x-forwarded-for`, trusted directly with no
      // proxy policy), is what stops a caller from choosing its own rate-limit bucket: the named
      // header is populated only by `apps/api`'s transport boundary, after it has already
      // resolved and verified the caller's address against the actual socket peer (and, in
      // explicit proxy mode, a configured trusted-proxy chain) — see
      // `apps/api/src/client-address.ts`. `trustedProxies` is deliberately left unset here: that
      // option only inspects header *content* for proxy-shaped addresses and can never verify who
      // actually sent the request, so the equivalent trust decision is made once, correctly, at
      // the transport boundary instead of asked of Better Auth a second time.
      ipAddress: {
        ipAddressHeaders: [TRUSTED_CLIENT_ADDRESS_HEADER],
      },
    },
    baseURL: options.config.baseUrl,
    database: drizzleAdapter(options.db, {
      provider: "pg",
      schema: identityAdapterSchema,
    }),
    emailAndPassword: {
      autoSignIn: false,
      // Public registration is disabled unless explicitly enabled (`IdentityConfig.
      // publicSignupEnabled`, `core/src/identity/config.ts`) — never a side effect of an absent,
      // misspelled, or loosely parsed configuration value. Better Auth's own `disableSignUp` gate
      // rejects every `/sign-up/email` call with a fixed `400 EMAIL_PASSWORD_SIGN_UP_DISABLED`
      // before ever looking up the email, so a disabled deployment never reveals whether an
      // address is already registered; sign-in and existing sessions are entirely unaffected.
      disableSignUp: !options.config.publicSignupEnabled,
      enabled: true,
      // Pinned explicitly rather than left on Better Auth's fallback default (`|| 8` / `|| 128`
      // in the pinned release): an implicit default can change silently on a future Better Auth
      // upgrade, and Ekklesia's own tests assert this exact 8–128 boundary.
      maxPasswordLength: 128,
      minPasswordLength: 8,
    },
    logger: {
      disabled: false,
      level: "error",
      log: (level) => sanitizedBetterAuthLogger(level),
    },
    // A second, independent layer alongside `logger` above: the pinned release's own transport
    // dependency (`better-call`'s router) has an unconditional `console.error("# SERVER_ERROR:
    // ", error)` fallback for any thrown value it does not recognize as one of Better Auth's own
    // `APIError`s — this fires *before* Better Auth's `logger` option is ever consulted, so no
    // logger configuration can reach it. `onAPIError.throw: true` closes that gap: Better Auth's
    // own `APIError`s (wrong password, invalid origin, disabled sign-up, ...) still resolve to
    // their normal HTTP response completely unaffected, but a genuinely unexpected failure (for
    // example a database outage) now propagates out of `auth.handler()` instead of being caught
    // and printed raw internally, so it reaches `handleAuthRequest`'s own try/catch below and
    // becomes a sanitized `IdentityRuntimeError` like any other unexpected failure.
    onAPIError: {
      throw: true,
    },
    rateLimit: {
      enabled: true,
      max: 100,
      window: 10,
      ...(rateLimitOverride
        ? {
            customRules: {
              "/sign-in/email": {
                max: rateLimitOverride.max ?? 100,
                window: rateLimitOverride.window ?? 10,
              },
              "/sign-up/email": {
                max: rateLimitOverride.max ?? 100,
                window: rateLimitOverride.window ?? 10,
              },
            },
          }
        : {}),
    },
    secret: options.config.secret,
    trustedOrigins: [...options.config.trustedOrigins],
  } satisfies BetterAuthOptions;

  const auth = constructBetterAuth(() => betterAuth(betterAuthOptions));
  // `getCookies` is Better Auth's own supported, exported helper (`better-auth/cookies`) for
  // resolving the configured cookie names from an options object — not a dependency internal. It
  // is given the identical object above, so the returned `sessionToken.name` is exactly the name
  // the constructed runtime will read, including the `__Secure-` prefix an https `baseURL` implies.
  const sessionCookieName = constructBetterAuth(
    () => getCookies(betterAuthOptions).sessionToken.name,
  );

  return Object.freeze({
    handleAuthRequest: async (request: Request): Promise<Response> => {
      try {
        return await auth.handler(request);
      } catch {
        throw new IdentityRuntimeError("AUTH_REQUEST_FAILED");
      }
    },
    resolvePrincipal: async (headers: Headers): Promise<EkklesiaPrincipal> => {
      let session: Awaited<ReturnType<typeof auth.api.getSession>>;
      try {
        session = await auth.api.getSession({ headers });
      } catch {
        // Defense in depth: the pinned Better Auth release already catches internal failures and
        // resolves to null instead of throwing here, but a future release is not guaranteed to.
        throw new IdentityRuntimeError("PRINCIPAL_RESOLUTION_FAILED");
      }

      const userId = session?.user?.id;
      if (typeof userId === "string") {
        return createAuthenticatedPrincipal(userId);
      }

      // Better Auth's getSession swallows infrastructure failures internally and returns null for
      // them exactly like a genuinely missing, expired, revoked, or malformed session — it never
      // throws. Only a request that actually presented *the configured session cookie* is
      // ambiguous enough to be worth disambiguating: with no cookie at all, or with only unrelated
      // cookies, Better Auth never resolved an Ekklesia session in the first place, so `null` is
      // unambiguous and no session-store work is performed. This is what keeps an arbitrary
      // anonymous cookie from causing identity database work on every request.
      if (hasConfiguredSessionCookie(headers, sessionCookieName)) {
        const sessionStoreUsable = await probeSessionStore(options.db);
        if (!sessionStoreUsable) {
          throw new IdentityRuntimeError("PRINCIPAL_RESOLUTION_FAILED");
        }
      }
      return ANONYMOUS_PRINCIPAL;
    },
  });
}