refactor(config): enforce runtime auth secret policy

apps/web/src/server/runtime-env.ts

@@ -0,0 +1,68 @@
+const DISALLOWED_PRODUCTION_SECRETS = new Set([
+  "dev-secret-change-in-production",
+  "changeme",
+  "change-me",
+  "default",
+  "secret",
+]);
+
+type RuntimeEnv = Partial<Record<string, string | undefined>>;
+
+function readEnvValue(env: RuntimeEnv, ...names: string[]): string | null {
+  for (const name of names) {
+    const value = env[name]?.trim();
+    if (value) {
+      return value;
+    }
+  }
+
+  return null;
+}
+
+function isProductionLike(env: RuntimeEnv): boolean {
+  return (env.NODE_ENV ?? "").trim() === "production";
+}
+
+function isLocalhost(hostname: string): boolean {
+  return hostname === "localhost" || hostname === "127.0.0.1" || hostname === "::1";
+}
+
+export function getRuntimeEnvViolations(env: RuntimeEnv = process.env): string[] {
+  if (!isProductionLike(env)) {
+    return [];
+  }
+
+  const violations: string[] = [];
+  const authSecret = readEnvValue(env, "AUTH_SECRET", "NEXTAUTH_SECRET");
+  const authUrl = readEnvValue(env, "AUTH_URL", "NEXTAUTH_URL");
+
+  if (!authSecret) {
+    violations.push("AUTH_SECRET or NEXTAUTH_SECRET must be set in production.");
+  } else if (DISALLOWED_PRODUCTION_SECRETS.has(authSecret)) {
+    violations.push("AUTH_SECRET or NEXTAUTH_SECRET must not use a known development placeholder in production.");
+  }
+
+  if (!authUrl) {
+    violations.push("AUTH_URL or NEXTAUTH_URL must be set in production.");
+  } else {
+    try {
+      const parsed = new URL(authUrl);
+      if (parsed.protocol !== "https:" && !isLocalhost(parsed.hostname)) {
+        violations.push("AUTH_URL or NEXTAUTH_URL must use https in production.");
+      }
+    } catch {
+      violations.push("AUTH_URL or NEXTAUTH_URL must be a valid URL in production.");
+    }
+  }
+
+  return violations;
+}
+
+export function assertSecureRuntimeEnv(env: RuntimeEnv = process.env): void {
+  const violations = getRuntimeEnvViolations(env);
+  if (violations.length === 0) {
+    return;
+  }
+
+  throw new Error(`Invalid production runtime configuration: ${violations.join(" ")}`);
+}