KexAlgorithms - no matching key exchange method found (ssh-ed25519 missing)

[clidawg]

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Prerequisites

• [X] Write a descriptive title.
• [X] Make sure you are able to repro it on the latest version
• [X] Search the existing issues.

Steps to reproduce

.ssh/config (Client, Windows 11 Pro, OpenSSH_for_Windows_8.9p1, LibreSSL 3.4.3)

[...]
  KexAlgorithms [email protected]

sshd_config (Server, Ubuntu 22.04, OpenSSH_8.9p1 Ubuntu-3, OpenSSL 3.0.2 15 Mar 2022)

[...]
KexAlgorithms [email protected]
[...]

Connection Error (Client):

[email protected]: Permission denied (publickey).

Connection Error (Server):

Sep  8 14:18:34 srv-a sshd[9910]: Connection reset by authenticating user myuser 234.234.234.243 port 55442 [preauth]
Sep  8 14:18:40 srv-a sshd[9912]: Unable to negotiate with 123.123.123.123 port 53881: no matching key exchange method found. Their offer: ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1 [preauth]

Same procedure tested with two Ubuntu 22.04 servers with OpenSSH_8.9p1 Ubuntu-3, OpenSSL 3.0.2 15 Mar 2022 - one of them as client and one of them as server. Its working as expected.

Expected behavior

successfull ssh connection with KexAlgorithms

Actual behavior

Ouput of ssh -v [email protected]

OpenSSH_for_Windows_8.1p1, LibreSSL 3.0.2
debug1: Reading configuration data C:\\Users\\USERNAME/.ssh/config
debug1: Connecting to 123.123.123.123 [123.123.123.123] port 22.
debug1: Connection established.
debug1: identity file C:\\Users\\USERNAME/.ssh/id_rsa type -1
debug1: identity file C:\\Users\\USERNAME/.ssh/id_rsa-cert type -1
debug1: identity file C:\\Users\\USERNAME/.ssh/id_dsa type -1
debug1: identity file C:\\Users\\USERNAME/.ssh/id_dsa-cert type -1
debug1: identity file C:\\Users\\USERNAME/.ssh/id_ecdsa type -1
debug1: identity file C:\\Users\\USERNAME/.ssh/id_ecdsa-cert type -1
debug1: identity file C:\\Users\\USERNAME/.ssh/id_ed25519 type 3
debug1: identity file C:\\Users\\USERNAME/.ssh/id_ed25519-cert type -1
debug1: identity file C:\\Users\\USERNAME/.ssh/id_xmss type -1
debug1: identity file C:\\Users\\USERNAME/.ssh/id_xmss-cert type -1
debug1: Local version string SSH-2.0-OpenSSH_for_Windows_8.1
debug1: Remote protocol version 2.0, remote software version OpenSSH_8.9p1 Ubuntu-3
debug1: match: OpenSSH_8.9p1 Ubuntu-3 pat OpenSSH* compat 0x04000000
debug1: Authenticating to 123.123.123.123:22 as 'myuser'
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: algorithm: [email protected]
debug1: kex: host key algorithm: ssh-ed25519
debug1: kex: server->client cipher: [email protected] MAC: <implicit> compression: none
debug1: kex: client->server cipher: [email protected] MAC: <implicit> compression: none
debug1: expecting SSH2_MSG_KEX_ECDH_REPLY
debug1: Server host key: ssh-ed25519 SHA256:fyUNV5mnKlVcyLxS9Srm4swjoDXtwDvaW+repD5rdLE
debug1: Host '123.123.123.123' is known and matches the ED25519 host key.
debug1: Found key in C:\\Users\\USERNAME/.ssh/known_hosts:2
debug1: rekey out after 134217728 blocks
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: rekey in after 134217728 blocks
debug1: Will attempt key: C:\\Users\\USERNAME/.ssh/id_ed25519 ED25519 SHA256:gJ0T9dMQotRD8jVpqgts1zudEvg90x7zOrnzTet4lro agent
debug1: Will attempt key: [email protected] ED25519 SHA256:VC7neW9st1ACZvIkdydBMLqCD3Pm4mJ2Zf7TzUiAvmQ agent
debug1: Will attempt key: C:\\Users\\USERNAME/.ssh/id_rsa
debug1: Will attempt key: C:\\Users\\USERNAME/.ssh/id_dsa
debug1: Will attempt key: C:\\Users\\USERNAME/.ssh/id_ecdsa
debug1: Will attempt key: C:\\Users\\USERNAME/.ssh/id_xmss
debug1: SSH2_MSG_EXT_INFO received
debug1: kex_input_ext_info: server-sig-algs=<ssh-ed25519,[email protected],ssh-rsa,rsa-sha2-256,rsa-sha2-512,ssh-dss,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,[email protected],[email protected]>
debug1: kex_input_ext_info: [email protected] (unrecognised)
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey
debug1: Next authentication method: publickey
debug1: Offering public key: C:\\Users\\USERNAME/.ssh/id_ed25519 ED25519 SHA256:gJ0T9dMQotRD8jVpqgts1zudEvg90x7zOrnzTet4lro agent
debug1: Authentications that can continue: publickey
debug1: Offering public key: [email protected] ED25519 SHA256:VC7neW9st1ACZvIkdydBMLqCD3Pm4mJ2Zf7TzUiAvmQ agent
debug1: Authentications that can continue: publickey
debug1: Trying private key: C:\\Users\\USERNAME/.ssh/id_rsa
debug1: Trying private key: C:\\Users\\USERNAME/.ssh/id_dsa
debug1: Trying private key: C:\\Users\\USERNAME/.ssh/id_ecdsa
debug1: Trying private key: C:\\Users\\USERNAME/.ssh/id_xmss
debug1: No more authentication methods to try.
[email protected]: Permission denied (publickey).

Error details

From my understanding, the latest version does not support ssh-ed25519 kex algorithm

Environment data

Name                           Value
----                           -----
PSVersion                      5.1.22000.832
PSEdition                      Desktop
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0...}
BuildVersion                   10.0.22000.832
CLRVersion                     4.0.30319.42000
WSManStackVersion              3.0
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1

Version

OpenSSH_for_Windows_8.9p1, LibreSSL 3.4.3

Visuals

No response