Add telemetry event (#702)

* test sending new event from sshd after kex exchange

* rename telemetry event for clarity

* add comments

* remove else since if block has fatal call

* rename method for additional clarity

contrib/win32/openssh/sshTelemetry.c

@@ -119,6 +119,19 @@ void send_encryption_telemetry(const char* direction,
     TraceLoggingUnregister(g_hProvider1);
 }
 
+void send_kex_exch_exit_code_telemetry(const int exit_code)
+{
+    TraceLoggingRegister(g_hProvider1);
+    TraceLoggingWrite(
+        g_hProvider1,
+        "KexExchExitCodeSSHD",
+        TelemetryPrivacyDataTag(PDT_ProductAndServiceUsage),
+        TraceLoggingKeyword(MICROSOFT_KEYWORD_MEASURES),
+        TraceLoggingInt16(exit_code, "KexExchExitCodeSSHD")
+    );
+    TraceLoggingUnregister(g_hProvider1);
+}
+
 void send_pubkey_telemetry(const char* pubKeyStatus)
 {
     TraceLoggingRegister(g_hProvider1);
@@ -205,4 +218,3 @@ void send_ssh_version_telemetry(const char* ssh_version,
     );
     TraceLoggingUnregister(g_hProvider1);
 }
-

contrib/win32/openssh/sshTelemetry.h

@@ -12,6 +12,9 @@ void send_encryption_telemetry(const char* direction,
 	const char* comp, const char* host_key, 
 	const char** cproposal, const char** sproposal);
 
+// sends exit code of kex_exchange_identification(), utilized only in sshd
+void send_kex_exch_exit_code_telemetry(const int exit_code);
+
 // sends status if using key-based auth
 void send_pubkey_telemetry(const char* pubKeyStatus);
 

sshd.c

@@ -2723,8 +2723,16 @@ done_loading_hostkeys:
 		alarm(options.login_grace_time);
 
 	if ((r = kex_exchange_identification(ssh, -1,
-	    options.version_addendum)) != 0)
+		options.version_addendum)) != 0)
+#ifdef WINDOWS
+	{
+		send_kex_exch_exit_code_telemetry(r);
+#endif /* WINDOWS */
 		sshpkt_fatal(ssh, r, "banner exchange");
+#ifdef WINDOWS
+	}
+	send_kex_exch_exit_code_telemetry(0);
+#endif /* WINDOWS */
 idexch_done:
 	ssh_packet_set_nonblocking(ssh);