add virtual api key validation in verifySession

server/lib/aiGatewayTrust.ts

@@ -0,0 +1,38 @@
+import { createHash } from "crypto";
+import config from "@server/lib/config";
+
+export const AI_GATEWAY_TRUST_HEADER = "X-Pangolin-Ai-Gateway-Auth";
+
+/**
+ * Derive a Traefik-injected trust token from the server secret.
+ * Traefik overwrites this header on inference routes so the AI gateway can
+ * trust Badger-injected Remote-* identity without re-validating credentials.
+ */
+export function deriveAiGatewayTrustToken(secret: string): string {
+    return createHash("sha256")
+        .update(`ai-gateway-trust:${secret}`)
+        .digest("hex");
+}
+
+export function getAiGatewayTrustToken(): string {
+    const secret = config.getRawConfig().server.secret;
+    if (!secret) {
+        throw new Error("Server secret is required for AI gateway trust token");
+    }
+    return deriveAiGatewayTrustToken(secret);
+}
+
+export function isAiGatewayTrustHeaderValid(
+    headers: Record<string, string | string[] | undefined> | undefined,
+    expectedToken?: string
+): boolean {
+    if (!headers) {
+        return false;
+    }
+    const expected = expectedToken ?? getAiGatewayTrustToken();
+    const raw =
+        headers[AI_GATEWAY_TRUST_HEADER] ??
+        headers[AI_GATEWAY_TRUST_HEADER.toLowerCase()];
+    const value = Array.isArray(raw) ? raw[0] : raw;
+    return typeof value === "string" && value === expected;
+}