From 9b4245d92193249e39358b8415a6c05ce005108f Mon Sep 17 00:00:00 2001
From: Guido Casati <hello@guidocasati.com>
Date: Tue, 15 Apr 2025 15:39:28 +0200
Subject: [PATCH] Add generation function and handler for NAS Authentication
 Failure

---
 openair3/NAS/NR_UE/5GS/NR_NAS_defs.h |  2 ++
 openair3/NAS/NR_UE/5GS/fgs_nas_lib.c |  5 +++++
 openair3/NAS/NR_UE/nr_nas_msg.c      | 18 ++++++++++++++++++
 3 files changed, 25 insertions(+)

diff --git a/openair3/NAS/NR_UE/5GS/NR_NAS_defs.h b/openair3/NAS/NR_UE/5GS/NR_NAS_defs.h
index 94e7f38a57..ab94925f09 100644
--- a/openair3/NAS/NR_UE/5GS/NR_NAS_defs.h
+++ b/openair3/NAS/NR_UE/5GS/NR_NAS_defs.h
@@ -35,6 +35,7 @@
 #include "RegistrationComplete.h"
 #include "RegistrationRequest.h"
 #include "fgs_service_request.h"
+#include "fgmm_authentication_failure.h"
 
 /* Message types defintions for:
    (a) 5GS Mobility Management (5GMM) (IDs 0x41 - 0x68)
@@ -222,6 +223,7 @@ typedef struct {
     fgs_service_request_msg_t service_request;
     fgmm_identity_response_msg fgs_identity_response;
     fgs_authentication_response_msg fgs_auth_response;
+    fgmm_auth_failure_t fgmm_auth_failure;
     fgs_deregistration_request_ue_originating_msg fgs_deregistration_request_ue_originating;
     fgs_security_mode_complete_msg fgs_security_mode_complete;
     registration_complete_msg registration_complete;
diff --git a/openair3/NAS/NR_UE/5GS/fgs_nas_lib.c b/openair3/NAS/NR_UE/5GS/fgs_nas_lib.c
index 16d84f3ad8..ca40131af6 100644
--- a/openair3/NAS/NR_UE/5GS/fgs_nas_lib.c
+++ b/openair3/NAS/NR_UE/5GS/fgs_nas_lib.c
@@ -73,6 +73,11 @@ int mm_msg_encode(const fgmm_nas_message_plain_t *p, uint8_t *buffer, uint32_t l
     case FGS_AUTHENTICATION_RESPONSE:
       enc_msg = encode_fgs_authentication_response(&p->mm_msg.fgs_auth_response, buffer, len);
       break;
+    case FGS_AUTHENTICATION_FAILURE: {
+      byte_array_t ba = {.buf = buffer, .len = len};
+      enc_msg = encode_fgmm_auth_failure(&ba, &p->mm_msg.fgmm_auth_failure);
+      break;
+    }
     case FGS_SECURITY_MODE_COMPLETE:
       enc_msg = encode_fgs_security_mode_complete(&p->mm_msg.fgs_security_mode_complete, buffer, len);
       break;
diff --git a/openair3/NAS/NR_UE/nr_nas_msg.c b/openair3/NAS/NR_UE/nr_nas_msg.c
index 941e0d7cdc..3640c40aaa 100644
--- a/openair3/NAS/NR_UE/nr_nas_msg.c
+++ b/openair3/NAS/NR_UE/nr_nas_msg.c
@@ -838,6 +838,24 @@ static void generateAuthenticationResp(nr_ue_nas_t *nas, as_nas_info_t *initialN
   free(res.value);
 }
 
+/** @brief Send Authentication Failure message from the UE to the AMF to
+ * indicate that authentication of the network has failed */
+static void generateAuthenticationFailure(nr_ue_nas_t *nas, as_nas_info_t *initialNasMsg, cause_id_t cause)
+{
+  int size = sizeof(fgmm_msg_header_t);
+  fgmm_nas_message_plain_t plain = {0};
+
+  // Plain 5GMM header
+  plain.header = set_mm_header(FGS_AUTHENTICATION_FAILURE, PLAIN_5GS_MSG);
+  size += sizeof(plain.header);
+  // 5GMM Cause (Mandatory)
+  fgmm_auth_failure_t *mm_msg = &plain.mm_msg.fgmm_auth_failure;
+  mm_msg->cause = cause;
+  size += 1;
+  initialNasMsg->nas_data = malloc_or_fail(size * sizeof(*initialNasMsg->nas_data));
+  initialNasMsg->length = mm_msg_encode(&plain, initialNasMsg->nas_data, size);
+}
+
 int nas_itti_kgnb_refresh_req(instance_t instance, const uint8_t kgnb[32])
 {
   MessageDef *message_p;