https://bugs.kde.org/show_bug.cgi?id=521891
Bug ID: 521891
Summary: KRDP Cascading issues
Classification: I don't know
Product: kde
Version First unspecified
Reported In:
Platform: Arch Linux
OS: Other
Status: REPORTED
Severity: normal
Priority: NOR
Component: general
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
KDE KRDP Bug Report
Title: KRDP 6.7.0 fails to connect due to PAM privileges, FreeRDP VAAPI crashes
on unsupported GPUs, and KPipeWire fallback failures
Component: krdp / kpipewire Version: Plasma 6.7.0, FreeRDP 3.27.1 OS: Arch
Linux (Wayland)
Summary
A recent system update to Plasma 6.7.0 and FreeRDP 3.27.1 completely breaks
KRDP on older hardware (Intel Sandy Bridge / No H.264 hardware encoding). This
is a multi-layered failure spanning PAM authentication, FreeRDP hardware
encoding crashes, and KPipeWire software fallback failures.
Issue 1: PAM Authentication Failure (NoNewPrivileges)
KRDP runs as a systemd user service. When connecting using System User
Authentication, pam_unix attempts to read /etc/shadow but fails to drop
privileges with: pam_unix(login:account): setuid failed: Operation not
permitted pam_authenticate failure: Authentication service cannot retrieve
authentication info Workaround: Injecting NoNewPrivileges=false into
app-org.kde.krdpserver.service.d/override.conf resolves the PAM error.
Issue 2: FreeRDP VAAPI Hard Crash
After bypassing the auth bug, FreeRDP (built with WITH_VAAPI=ON) attempts to
initialize a hardware H.264 encoder on a Sandy Bridge GPU that only supports
decoding. Instead of gracefully falling back to software encoding, it
hard-crashes the socket connection: VAAPI: Failed to initialize display VAAPI:
current session render node "/dev/dri/renderD128" does not support H264
encoding BIO_should_retry returned an error: error:80000020:system
library::Broken pipe Workaround: Downgrading freerdp to 3.22.0-2 prevents the
hard crash and allows the connection to stay open.
Issue 3: KPipeWire Software Encoder Fallback Failure
Even with a stable FreeRDP version, the stream returns a black screen (0 FPS).
The KPipeWire fallback fails to automatically provide frames. Workaround:
Manually injecting Environment=KPIPEWIRE_FORCE_ENCODER=libx264 into the systemd
service forces the software encoder to work correctly and stream the desktop.
Issue 4: xdg-desktop-portal-kde Locale Bug
The screen-sharing portal service fails D-Bus registration if started by
systemd in a non-UTF-8 environment: Detected locale "C" with character encoding
"ANSI_X3.4-1968", which is not UTF-8. Failed to register with host portal
QDBusError("org.freedesktop.portal.Error.Failed", "Could not register app ID:
Connection already associated with an application ID") Workaround: Injecting
LANG=en_US.UTF-8 into the systemd environment fixes the portal negotiation.
Expected Behavior
The KRDP systemd service should have the correct privileges configured to allow
pam_unix to authenticate system users.
FreeRDP/KRDP should gracefully fall back to software encoding when the VAAPI
driver reports does not support H264 encoding, without dropping the TCP
connection.
KPipeWire should automatically select a functional software encoder (like
libx264) if hardware acceleration is physically unavailable or fails to
initialize.
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