Description of problem:
The commit/patch at
was never picked up and merged, and now that WinSCP has recently released version 5.11(.x), this is causing problems when wanting to use this WinSCP version to connect to an ssh server running on Fedora 25, 26 and 27 that is configured to only accept diffie-hellman-group-exchange-sha256, using this setting in sshd_config:
Version-Release number of selected component (if applicable):
Steps to reproduce:
1. In sshd_config, configure: KexAlgorithms diffie-hellman-group-exchange-sha256
2. Connect with WinSCP version 5.11.1 to the ssh server
WinSCP cannot connect, and sshd logs the following message:
fatal: No supported key exchange algorithms found [preauth]
This should connect fine with the configured key-exchange algorithm.
With the above setting, the client cannot connect at all and when commenting it out, however, it then causes the ssh server to erroneously force a weaker key-exchange (diffie-hellman-group14-sha1) on the user.
This was reported to WinSCP itself: https://winscp.net/forum/viewtopic.php?t=25354
This was also reported to Debian (added as External Bug).
openssh-7.6p1-2.fc27 has been submitted as an update to Fedora 27. https://bodhi.fedoraproject.org/updates/FEDORA-2017-96d1995b70
openssh-7.6p1-2.fc27 has been pushed to the Fedora 27 testing repository. If problems still persist, please make note of it in this bug report.
See https://fedoraproject.org/wiki/QA:Updates_Testing for
instructions on how to install test updates.
You can provide feedback for this update here: https://bodhi.fedoraproject.org/updates/FEDORA-2017-96d1995b70
openssh-7.6p1-2.fc27 has been pushed to the Fedora 27 stable repository. If problems still persist, please make note of it in this bug report.