iOS 0.5.6 fails TLS handshake with UnsupportedCertVersion
Description
KDE Connect for COSMIC can discover an iPhone via mDNS and establish a TCP connection, but the iPhone never becomes available for pairing/connection in the COSMIC KDE Connect application.
The connection reaches the KDE Connect service successfully, but the TLS handshake fails with:
[handshake] TLS accept failed: invalid peer certificate: Other(OtherError(UnsupportedCertVersion))
Environment
- OS: Fedora Linux
- Desktop: COSMIC
- KDE Connect for COSMIC Flatpak:
io.github.hepp3n.kdeconnect
- COSMIC KDE Connect version:
0.10.0
- Flatpak branch:
master
- Runtime:
org.freedesktop.Platform/x86_64/25.08
- iOS KDE Connect version:
0.5.6(1)
- Device: iPhone
- KDE Connect protocol advertised by iOS device:
8
Reproduction
- Start KDE Connect for COSMIC.
- Open KDE Connect on the iPhone.
- Both devices are connected to the same local network.
- The iPhone is successfully discovered through mDNS.
- The KDE Connect service detects the iPhone and attempts a TCP connection.
- The TLS handshake fails with
UnsupportedCertVersion.
- The iPhone does not appear as an available device in the COSMIC KDE Connect UI.
Diagnostics
mDNS
Avahi successfully discovers the iPhone as a KDE Connect device:
_kdeconnect._udp
port = 1716
type = phone
protocol = 8
Flatpak
The Flatpak has network access:
[Context]
shared=ipc;network;
KDE Connect service
The service successfully listens on TCP/UDP port 1716 and detects the iPhone:
INFO kdeconnect_core::transport:
Device supports TCP
peer=<local-address>:1716
device_id=DeviceId("<device-id>")
device_name="<device-name>"
TCP connectivity
A direct TCP connection to the iPhone on port 1716 succeeds.
A packet capture confirms bidirectional TCP communication between the devices. Data is exchanged in both directions before the connection is closed.
TLS error
The KDE Connect service then reports:
WARN kdeconnect_core::transport:
[handshake] TLS accept failed:
invalid peer certificate:
Other(OtherError(UnsupportedCertVersion))
peer=<local-address>:1716
The error occurs consistently on subsequent connection attempts.
Expected behaviour
The iPhone should appear as an available KDE Connect device and allow pairing after successful discovery.
Actual behaviour
The iPhone is successfully discovered and a TCP connection is established, but the TLS handshake fails with:
The device consequently does not become available for pairing in the COSMIC KDE Connect UI.
Additional information
The network configuration has been independently verified. There are no apparent connectivity, routing, firewall, mDNS, or Flatpak network-permission issues.
The failure appears to occur specifically during TLS certificate validation after successful device discovery and TCP connection establishment.
Could this be related to certificate version handling in the Rust TLS implementation used by kdeconnect-core, or compatibility with the certificate generated/used by iOS KDE Connect 0.5.6(1)?
I would be happy to provide additional debug logs or packet captures if required.
iOS 0.5.6 fails TLS handshake with
UnsupportedCertVersionDescription
KDE Connect for COSMIC can discover an iPhone via mDNS and establish a TCP connection, but the iPhone never becomes available for pairing/connection in the COSMIC KDE Connect application.
The connection reaches the KDE Connect service successfully, but the TLS handshake fails with:
Environment
io.github.hepp3n.kdeconnect0.10.0masterorg.freedesktop.Platform/x86_64/25.080.5.6(1)8Reproduction
UnsupportedCertVersion.Diagnostics
mDNS
Avahi successfully discovers the iPhone as a KDE Connect device:
Flatpak
The Flatpak has network access:
KDE Connect service
The service successfully listens on TCP/UDP port 1716 and detects the iPhone:
TCP connectivity
A direct TCP connection to the iPhone on port 1716 succeeds.
A packet capture confirms bidirectional TCP communication between the devices. Data is exchanged in both directions before the connection is closed.
TLS error
The KDE Connect service then reports:
The error occurs consistently on subsequent connection attempts.
Expected behaviour
The iPhone should appear as an available KDE Connect device and allow pairing after successful discovery.
Actual behaviour
The iPhone is successfully discovered and a TCP connection is established, but the TLS handshake fails with:
The device consequently does not become available for pairing in the COSMIC KDE Connect UI.
Additional information
The network configuration has been independently verified. There are no apparent connectivity, routing, firewall, mDNS, or Flatpak network-permission issues.
The failure appears to occur specifically during TLS certificate validation after successful device discovery and TCP connection establishment.
Could this be related to certificate version handling in the Rust TLS implementation used by
kdeconnect-core, or compatibility with the certificate generated/used by iOS KDE Connect0.5.6(1)?I would be happy to provide additional debug logs or packet captures if required.