Support PIN-required auth servers

include/auth/pin_auth.hpp

@@ -0,0 +1,28 @@
+#pragma once
+
+#include <array>
+#include <cstdint>
+#include <string>
+
+namespace wowee {
+namespace auth {
+
+struct PinProof {
+    std::array<uint8_t, 16> clientSalt{};
+    std::array<uint8_t, 20> hash{};
+};
+
+// Implements the "PIN" security extension used in the WoW auth protocol (securityFlags & 0x01).
+// Algorithm based on documented client behavior:
+// - Remap digits using pinGridSeed (a permutation of 0..9)
+// - Convert user-entered PIN digits into randomized indices in that permutation
+// - Compute: pin_hash = SHA1(client_salt || SHA1(server_salt || randomized_pin_ascii))
+//
+// PIN must be 4-10 ASCII digits.
+PinProof computePinProof(const std::string& pinDigits,
+                         uint32_t pinGridSeed,
+                         const std::array<uint8_t, 16>& serverSalt);
+
+} // namespace auth
+} // namespace wowee
+