Windows app hang when trying to paste from clipboard when xrdp connected Ubuntu lock its screen

[Mingun]

xrdp version

0.9.24

Detailed xrdp version, build options

$ xrdp --version
xrdp 0.9.24
  A Remote Desktop Protocol Server.
  Copyright (C) 2004-2020 Jay Sorg, Neutrino Labs, and all contributors.
  See https://github.com/neutrinolabs/xrdp for more information.

  Configure options:
      --enable-ipv6
      --enable-jpeg
      --enable-fuse
      --enable-rfxcodec
      --enable-opus
      --enable-painter
      --enable-vsock
      --build=x86_64-linux-gnu
      --prefix=/usr
      --includedir=${prefix}/include
      --mandir=${prefix}/share/man
      --infodir=${prefix}/share/info
      --sysconfdir=/etc
      --localstatedir=/var
      --disable-silent-rules
      --libdir=${prefix}/lib/x86_64-linux-gnu
      --libexecdir=${prefix}/lib/x86_64-linux-gnu
      --disable-maintainer-mode
      --disable-dependency-tracking
      --with-socketdir=/run/xrdp/sockdir
      build_alias=x86_64-linux-gnu
      CFLAGS=-g -O2 -fno-omit-frame-pointer -mno-omit-leaf-frame-pointer -ffile-prefix-map=/build/xrdp-Fn5kxo/xrdp-0.9.24=. -flto=auto -ffat-lto-objects -fstack-protector-strong -fstack-clash-protection -Wformat -Werror=format-security -fcf-protection -fdebug-prefix-map=/build/xrdp-Fn5kxo/xrdp-0.9.24=/usr/src/xrdp-0.9.24-4 
      LDFLAGS=-Wl,-Bsymbolic-functions -flto=auto -ffat-lto-objects -Wl,-z,relro -Wl,-z,now -Wl,--as-needed
      CPPFLAGS=-Wdate-time -D_FORTIFY_SOURCE=3 
      PKG_CONFIG_PATH=/build/xrdp-Fn5kxo/xrdp-0.9.24/pkgconfig

  Compiled with OpenSSL 3.0.13 30 Jan 2024

Operating system & version

Ubuntu 24.04.2 LTS

Installation method

dnf / apt / zypper / pkg / etc

Which backend do you use?

xorg

What desktop environment do you use?

GNOME

Environment xrdp running on

Physical machine, don't know how to check card

What's your client?

mstsc.exe from Windows 10, 19044.6093

Area(s) with issue?

Clipboard

Steps to reproduce

1. On remote side (Ubuntu via xrdp for me) copy something into the clipboard (text or file in Nautilus)
2. Wait when screen on remote machine will automatically locked due to inactivity
3. Try to paste text into any text field (Firefox, VS Code, etc.) or file in Explorer

✔️ Expected Behavior

You are able to paste things despite the state of the remote side.

❌ Actual Behavior

When you try to paste, Windows application hang until you disconnected from remote machine. After disconnect you clipboard is cleared. Although this is understandable for files that can be quite large, for text it is still expected that it can be inserted.

Anything else?

Windows version:

Выпуск	Windows 10 IoT Корпоративная LTSC
Версия	21H2
Дата установки	‎02.‎01.‎2025
Сборка ОС	19044.6093
Взаимодействие	Windows Feature Experience Pack 1000.19062.1000.0

I don't know is this is an xrdp bug or mstsc.exe bug, because I cannot test with remote connection to the Windows machine. But it is very annoying. Due to other bug in xrdp, each disconnection from the remote host resets configured layouts so I have to manually execute

setxkbmap -layout 'us,ru'

each time a reconnected. Putting this line into /etc/xrdp/reconnectwm.sh does not work (#3579)...

[matt335672]

The behaviour you're expecting isn't actually what happens with GNOME when the screen is locked.

I've just done the following on Ubuntu 24.04.2 LTS (no xrdp):-

1. Log in to GNOME (Xorg) on the console
2. Install xclip with sudo apt install xclip.
3. Make a note of the DISPLAY and XAUTHORITY environment variables
4. From a separate machine, ssh into the first machine as the same user.
5. in the ssh session, set DISPLAY and XAUTHORITY to be the values noted in step 2.
6. Copy some text in the GNOME session. I copied the contents of the terminal window I'd used to get the value of the environment variables, and selected 'copy' on the right-click menu.
7. In the ssh session, display the text with xclip -o -selection clipboard -t TEXT. I get:-

$ xclip -o -selection clipboard -t TEXT
testuser2@xrdp-test:~$ echo $DISPLAY
:0
testuser2@xrdp-test:~$ echo $XAUTHORITY
/run/user/1004/gdm/Xauthority

7. Lock the GNOME session
8. In the ssh session repeat the xclip command. I get:-

$ xclip -o -selection clipboard -t TEXT
Error: target TEXT not available

So you can't extract text from a locked session. Here's the original GNOME PR for this:

https://gitlab.gnome.org/GNOME/gnome-shell/-/commit/41ae93dba05995a491a229acba027c07a0680b95

[Mingun]

Ok, but why Window app hangs on trying to paste text? xrdp tries to get text from locked screen and waits it to unlock (but even when I unlock screen, the Window app still hanging, the only way to unhang it it is to disconnect)? Or this is the wrong mstsc.exe reaction to the some error that xrdp returns when it cannot get clipboard content?

[Mingun]

Forgot to mention, the situation even more worse. The Windows app to which I try to paste the text hangs when I copy text on Windows side. If at this moment xrdp connected machine already locked, then the application freezes until I close mstsc.exe. Moreover after that the Windows clipboard is cleared. That happens not always, I suspect only in the following sequence:

• I copy text on Windows side
• the remote Ubuntu locks its screen
• I try to paste copied text to Windows app
• Windows app freezes

[matt335672]

I've got some good news and some bad news.

The good news is I can reproduce this (or something like it) on v0.10.x of xrdp. I'll have a closer look after the weekend and report back on what is happening.

The bad news is that the version of xrdp you're using won't be getting an update. We no longer provide anything other than security fixes for v0.9.x. Ubuntu have moved to version v0.10.x of xrdp with plucky (25.04), but they don't generally backport Universe packages to the last LTS version.

[matt335672]

Another option might be a different desktop. I've just tried XFCE and xscreensaver on 24.04 LTS. XFCE doesn't clear the clipboard in the way that GNOME does.

It's a disruptive change though, and XFCE isn't to everyone's taste. I'd only try it if this functionality is more important to you than the actual desktop itself. There's also the possibility that XFCE or xscreensaver will implement the same functionality in the future.

[matt335672]

I've found the root cause of this, and I'm fixing it in devel and v0.10.x.

The reason is we're not expecting an X client to return an empty string to us when we ask for a text format!

It's one of those things which is obvious after the event. I can only think we've not seen this before as it's hard to select an empty amount of text in a GUI.