From 5291a82cd9b9d8d7cd6b8338a5224c94c6f23eb7 Mon Sep 17 00:00:00 2001
From: Alexander Bantyev <balsoft@balsoft.ru>
Date: Thu, 9 Mar 2023 18:16:29 +0400
Subject: [PATCH] SSHMaster: pause logger to show password prompt

Pause logger before starting SSH connections, and resume it after the
connection is established, so that SSH password prompts are not erased
by the logger's updates.
---
 src/libstore/ssh.cc | 30 +++++++++++++++++++++++++-----
 1 file changed, 25 insertions(+), 5 deletions(-)

diff --git a/src/libstore/ssh.cc b/src/libstore/ssh.cc
index 69bfe3418..6f6deda51 100644
--- a/src/libstore/ssh.cc
+++ b/src/libstore/ssh.cc
@@ -1,4 +1,5 @@
 #include "ssh.hh"
+#include "finally.hh"
 
 namespace nix {
 
@@ -35,6 +36,9 @@ void SSHMaster::addCommonSSHOpts(Strings & args)
     }
     if (compress)
         args.push_back("-C");
+
+    args.push_back("-oPermitLocalCommand=yes");
+    args.push_back("-oLocalCommand=echo started");
 }
 
 std::unique_ptr<SSHMaster::Connection> SSHMaster::startCommand(const std::string & command)
@@ -49,6 +53,11 @@ std::unique_ptr<SSHMaster::Connection> SSHMaster::startCommand(const std::string
     ProcessOptions options;
     options.dieWithParent = false;
 
+    if (!fakeSSH && !useMaster) {
+        logger->pause();
+    }
+    Finally cleanup = [&]() { logger->resume(); };
+
     conn->sshPid = startProcess([&]() {
         restoreProcessContext();
 
@@ -86,6 +95,18 @@ std::unique_ptr<SSHMaster::Connection> SSHMaster::startCommand(const std::string
     in.readSide = -1;
     out.writeSide = -1;
 
+    // Wait for the SSH connection to be established,
+    // So that we don't overwrite the password prompt with our progress bar.
+    if (!fakeSSH && !useMaster) {
+        std::string reply;
+        try {
+            reply = readLine(out.readSide.get());
+        } catch (EndOfFile & e) { }
+
+        if (reply != "started")
+            throw Error("failed to start SSH connection to '%s'", host);
+    }
+
     conn->out = std::move(out.readSide);
     conn->in = std::move(in.writeSide);
 
@@ -109,6 +130,9 @@ Path SSHMaster::startMaster()
     ProcessOptions options;
     options.dieWithParent = false;
 
+    logger->pause();
+    Finally cleanup = [&]() { logger->resume(); };
+
     state->sshMaster = startProcess([&]() {
         restoreProcessContext();
 
@@ -117,11 +141,7 @@ Path SSHMaster::startMaster()
         if (dup2(out.writeSide.get(), STDOUT_FILENO) == -1)
             throw SysError("duping over stdout");
 
-        Strings args =
-            { "ssh", host.c_str(), "-M", "-N", "-S", state->socketPath
-            , "-o", "LocalCommand=echo started"
-            , "-o", "PermitLocalCommand=yes"
-            };
+        Strings args = { "ssh", host.c_str(), "-M", "-N", "-S", state->socketPath };
         if (verbosity >= lvlChatty)
             args.push_back("-v");
         addCommonSSHOpts(args);