UE authentication procedure improvements

src/ue/nas/keys.cpp

@@ -147,4 +147,11 @@ OctetString DeriveAmfPrimeInMobility(bool isUplink, const NasCount &count, const
     return crypto::CalculateKdfKey(kAmf, 0x72, params, 2);
 }
 
+OctetString CalculateAuts(const OctetString &sqn, const OctetString &ak, const OctetString &macS)
+{
+    OctetString auts = OctetString::Xor(sqn, ak);
+    auts.append(macS);
+    return auts;
+}
+
 } // namespace nr::ue::keys
\ No newline at end of file

src/ue/nas/keys.hpp

@@ -71,4 +71,9 @@ OctetString CalculateKAusfForEapAkaPrime(const OctetString &mk);
 OctetString CalculateResStar(const OctetString &key, const std::string &snn, const OctetString &rand,
                              const OctetString &res);
 
-} // namespace nr::ue::keys
\ No newline at end of file
+/*
+ * Calculates AUTS according to the given parameters
+ */
+OctetString CalculateAuts(const OctetString &sqn, const OctetString &ak, const OctetString &macS);
+
+} // namespace nr::ue::keys

src/ue/nas/mm/auth.cpp

@@ -304,6 +304,7 @@ void NasMm::receiveAuthenticationRequest5gAka(const nas::AuthenticationRequest &
     auto ckIk = OctetString::Concat(ck, ik);
     auto &milenageAk = milenage.ak;
     auto &milenageMac = milenage.mac_a;
+    auto &milenageMacS = milenage.mac_s;
     auto sqnXorAk = OctetString::Xor(m_usim->m_sqn, milenageAk);
     auto snn = keys::ConstructServingNetworkName(*m_usim->m_currentPlmn);
 
@@ -337,7 +338,7 @@ void NasMm::receiveAuthenticationRequest5gAka(const nas::AuthenticationRequest &
     }
     else if (autnCheck == EAutnValidationRes::SYNCHRONISATION_FAILURE)
     {
-        sendFailure(nas::EMmCause::SYNCH_FAILURE);
+        sendFailure(nas::EMmCause::SYNCH_FAILURE, keys::CalculateAuts(m_usim->m_sqn, milenageAk, milenageMacS));
     }
     else
     {