Added skipping of fragment length to EAP-TLS protocol and other improvements

- Fragment length field is now skipped if present in other messages
than in first message with more fragments flag set.
- For EAP-TLS start message on supplicant side: stops processing to
flags field and ignores fields after it.
- For TLS initialization errors (e.g. due to no-memory) on supplicant
side, no longer sends empty EAP-TLS message, instead terminates the
EAP-TLS and TLS sessions silently.

Author: Mika Leppänen

source/Security/protocols/eap_tls_sec_prot/eap_tls_sec_prot_lib.c

@@ -119,7 +119,16 @@ int8_t eap_tls_sec_prot_lib_message_handle(uint8_t *data, uint16_t length, bool
             data += 4;
         }
         result = EAP_TLS_MSG_MORE_FRAG;
-    } else if (data[0] == 0) {
+    } else if (data[0] == 0 || data[0] == EAP_TLS_FRAGMENT_LENGTH) {
+        // Skip fragment length if present
+        if (data[0] & EAP_TLS_FRAGMENT_LENGTH) {
+            if (length < 5) {
+                tr_error("EAP-TLS: decode error");
+                return EAP_TLS_MSG_DECODE_ERROR;
+            }
+            length -= 4;
+            data += 4;
+        }
         // Last (or only) fragment or fragment acknowledge. If sending data
         // updates acknowledged fragments.
         if (new_seq_id && eap_tls_sec_prot_lib_ack_update(tls_send)) {
@@ -132,10 +141,15 @@ int8_t eap_tls_sec_prot_lib_message_handle(uint8_t *data, uint16_t length, bool
     length -= 1;  // EAP-TLS flags
     data += 1;
 
+    // No further processing for EAP-TLS start
+    if (result == EAP_TLS_MSG_START) {
+        return EAP_TLS_MSG_START;
+    }
+
     // TLS data not included
     if (length == 0) {
         if (new_seq_id && result == EAP_TLS_MSG_CONTINUE) {
-            // If received only EAP-TLS header fails, and is not start,
+            // If received only EAP-TLS header fails, and is not
             // fragment acknowledge or last frame
             result = EAP_TLS_MSG_FAIL;
         }

source/Security/protocols/eap_tls_sec_prot/supp_eap_tls_sec_prot.c

@@ -466,6 +466,9 @@ static void supp_eap_tls_sec_prot_state_machine(sec_prot_t *prot)
             // Initialize TLS protocol
             if (supp_eap_tls_sec_prot_init_tls(prot) < 0) {
                 tr_error("TLS init failed");
+                // If fatal error terminates EAP-TLS
+                sec_prot_result_set(&data->common, SEC_RESULT_ERROR);
+                sec_prot_state_set(prot, &data->common, EAP_TLS_STATE_FINISH);
                 return;
             }
             // Request TLS to start (send client hello)
@@ -508,7 +511,12 @@ static void supp_eap_tls_sec_prot_state_machine(sec_prot_t *prot)
                 }
             } else {
                 data->wait_tls = false;
-                if (!data->tls_send.data || data->tls_result == EAP_TLS_RESULT_HANDSHAKE_FATAL_ERROR) {
+                if (data->tls_result == EAP_TLS_RESULT_HANDSHAKE_FATAL_ERROR) {
+                    // If fatal error terminates EAP-TLS (TLS init has failed)
+                    sec_prot_result_set(&data->common, SEC_RESULT_ERROR);
+                    sec_prot_state_set(prot, &data->common, EAP_TLS_STATE_FINISH);
+                    return;
+                } else if (!data->tls_send.data) {
                     // If no more data send response, TLS EAP (empty)
                     eap_tls_sec_prot_lib_message_allocate(&data->tls_send, TLS_HEAD_LEN, 0);
                 }