From 612b293c1e29c62ced3a1884fad57e98fb560642 Mon Sep 17 00:00:00 2001
From: Simon Tatham <anakin@pobox.com>
Date: Tue, 14 Sep 2021 08:20:42 +0100
Subject: [PATCH] rlogin: defer username prompt until connection is made.

This gives more sensible handling of failed network connections: if
the connection _doesn't_ get made, it's pointless to ask the user for
a login username anyway, and worse still, you'd probably end up giving
the connection-failure error message while the user was in the middle
of answering the username prompt.

But more importantly, when proxy systems start being able to present
their own interactive prompts, it's vital that no backend should
already be presenting a prompt while in the process of setting up a
network connection.
---
 otherbackends/rlogin.c | 66 +++++++++++++++++++++++-------------------
 1 file changed, 37 insertions(+), 29 deletions(-)

diff --git a/otherbackends/rlogin.c b/otherbackends/rlogin.c
index ecdb2c36..871a4f19 100644
--- a/otherbackends/rlogin.c
+++ b/otherbackends/rlogin.c
@@ -32,6 +32,8 @@ struct Rlogin {
     Backend backend;
 };
 
+static void rlogin_startup(Rlogin *rlogin, const char *ruser);
+
 static void c_write(Rlogin *rlogin, const void *buf, size_t len)
 {
     size_t backlog = seat_stdout(rlogin->seat, buf, len);
@@ -53,6 +55,41 @@ static void rlogin_log(Plug *plug, PlugLogType type, SockAddr *addr, int port,
             rlogin->seat = tempseat_get_real(ts);
             tempseat_free(ts);
         }
+
+        char *ruser = get_remote_username(rlogin->conf);
+        if (ruser) {
+            /*
+             * If we already know the remote username, call
+             * rlogin_startup, which will send the initial protocol
+             * greeting including local username, remote username,
+             * terminal type and terminal speed.
+             */
+            /* Next terminal output will come from server */
+            seat_set_trust_status(rlogin->seat, false);
+            rlogin_startup(rlogin, ruser);
+            sfree(ruser);
+        } else {
+            /*
+             * Otherwise, set up a prompts_t asking for the local
+             * username. If it completes synchronously, call
+             * rlogin_startup as above; otherwise, wait until it does.
+             */
+            rlogin->prompt = new_prompts();
+            rlogin->prompt->to_server = true;
+            rlogin->prompt->from_server = false;
+            rlogin->prompt->name = dupstr("Rlogin login name");
+            add_prompt(rlogin->prompt, dupstr("rlogin username: "), true);
+
+            int ret = seat_get_userpass_input(rlogin->seat, rlogin->prompt,
+                                              NULL);
+            if (ret >= 0) {
+                /* Next terminal output will come from server */
+                seat_set_trust_status(rlogin->seat, false);
+                rlogin_startup(rlogin, prompt_get_result_ref(
+                                  rlogin->prompt->prompts[0]));
+            }
+        }
+
     }
 }
 
@@ -173,7 +210,6 @@ static char *rlogin_init(const BackendVtable *vt, Seat *seat,
     SockAddr *addr;
     const char *err;
     Rlogin *rlogin;
-    char *ruser;
     int addressfamily;
     char *loghost;
 
@@ -228,34 +264,6 @@ static char *rlogin_init(const BackendVtable *vt, Seat *seat,
             *colon++ = '\0';
     }
 
-    /*
-     * Send local username, remote username, terminal type and
-     * terminal speed - unless we don't have the remote username yet,
-     * in which case we prompt for it and may end up deferring doing
-     * anything else until the local prompt mechanism returns.
-     */
-    if ((ruser = get_remote_username(conf)) != NULL) {
-        /* Next terminal output will come from server */
-        seat_set_trust_status(rlogin->seat, false);
-        rlogin_startup(rlogin, ruser);
-        sfree(ruser);
-    } else {
-        int ret;
-
-        rlogin->prompt = new_prompts();
-        rlogin->prompt->to_server = true;
-        rlogin->prompt->from_server = false;
-        rlogin->prompt->name = dupstr("Rlogin login name");
-        add_prompt(rlogin->prompt, dupstr("rlogin username: "), true);
-        ret = seat_get_userpass_input(rlogin->seat, rlogin->prompt, NULL);
-        if (ret >= 0) {
-            /* Next terminal output will come from server */
-            seat_set_trust_status(rlogin->seat, false);
-            rlogin_startup(rlogin, prompt_get_result_ref(
-                               rlogin->prompt->prompts[0]));
-        }
-    }
-
     return NULL;
 }