From ef289eaa4a72cefad959232826e28d0c05f72d55 Mon Sep 17 00:00:00 2001
From: Nick Couchman <nick.couchman@yahoo.com>
Date: Sat, 9 Sep 2017 14:45:11 -0400
Subject: [PATCH] TELNET: Add ability to override detected echo setting.

---
 src/protocols/telnet/settings.c | 12 ++++++++++++
 src/protocols/telnet/settings.h |  5 +++++
 src/protocols/telnet/telnet.c   | 12 ++++++++++--
 3 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/src/protocols/telnet/settings.c b/src/protocols/telnet/settings.c
index df7b2958..5f83b269 100644
--- a/src/protocols/telnet/settings.c
+++ b/src/protocols/telnet/settings.c
@@ -39,6 +39,7 @@ const char* GUAC_TELNET_CLIENT_ARGS[] = {
     "password-regex",
     "font-name",
     "font-size",
+    "override-echo",
     "color-scheme",
     "typescript-path",
     "typescript-name",
@@ -94,6 +95,11 @@ enum TELNET_ARGS_IDX {
      */
     IDX_FONT_SIZE,
 
+    /**
+     * Whether or not to override the local telnet echo.
+     */
+    IDX_OVERRIDE_ECHO,
+
     /**
      * The name of the color scheme to use. Currently valid color schemes are:
      * "black-white", "white-black", "gray-black", and "green-black", each
@@ -239,6 +245,11 @@ guac_telnet_settings* guac_telnet_parse_args(guac_user* user,
         guac_user_parse_args_int(user, GUAC_TELNET_CLIENT_ARGS, argv,
                 IDX_FONT_SIZE, GUAC_TELNET_DEFAULT_FONT_SIZE);
 
+    /* Read echo override */
+    settings->override_echo =
+        guac_user_parse_args_string(user, GUAC_TELNET_CLIENT_ARGS, argv,
+                IDX_OVERRIDE_ECHO, NULL);
+
     /* Copy requested color scheme */
     settings->color_scheme =
         guac_user_parse_args_string(user, GUAC_TELNET_CLIENT_ARGS, argv,
@@ -314,6 +325,7 @@ void guac_telnet_settings_free(guac_telnet_settings* settings) {
     /* Free display preferences */
     free(settings->font_name);
     free(settings->color_scheme);
+    free(settings->override_echo);
 
     /* Free typescript settings */
     free(settings->typescript_name);
diff --git a/src/protocols/telnet/settings.h b/src/protocols/telnet/settings.h
index 434e5938..304e88b7 100644
--- a/src/protocols/telnet/settings.h
+++ b/src/protocols/telnet/settings.h
@@ -127,6 +127,11 @@ typedef struct guac_telnet_settings {
      */
     int font_size;
 
+    /**
+     * Override the local echo detection.
+     */
+    char* override_echo;
+
     /**
      * The name of the color scheme to use.
      */
diff --git a/src/protocols/telnet/telnet.c b/src/protocols/telnet/telnet.c
index 82f6dd4d..6df97e82 100644
--- a/src/protocols/telnet/telnet.c
+++ b/src/protocols/telnet/telnet.c
@@ -195,13 +195,21 @@ static void __guac_telnet_event_handler(telnet_t* telnet, telnet_event_t* event,
 
         /* Remote feature enabled */
         case TELNET_EV_WILL:
-            if (event->neg.telopt == TELNET_TELOPT_ECHO)
+            if (settings->override_echo != NULL && strcmp(settings->override_echo, "disabled") == 0)
+                telnet_client->echo_enabled = 0;
+            else if (settings->override_echo != NULL && strcmp(settings->override_echo, "enabled") == 0)
+                telnet_client->echo_enabled = 1;
+            else if (event->neg.telopt == TELNET_TELOPT_ECHO)
                 telnet_client->echo_enabled = 0; /* Disable local echo, as remote will echo */
             break;
 
         /* Remote feature disabled */
         case TELNET_EV_WONT:
-            if (event->neg.telopt == TELNET_TELOPT_ECHO)
+            if (settings->override_echo != NULL && strcmp(settings->override_echo, "enabled") == 0)
+                telnet_client->echo_enabled = 1;
+            else if (settings->override_echo != NULL && strcmp(settings->override_echo, "disabled") == 0)
+                telnet_client->echo_enabled = 0;
+            else if (event->neg.telopt == TELNET_TELOPT_ECHO)
                 telnet_client->echo_enabled = 1; /* Enable local echo, as remote won't echo */
             break;