SSH / SFTP key related problem since 23.10.0

[Louis2]

I updated to cobra a few days ago, and since than my SFTP backup tool can not access the NAS any more.

After trying to understand the problem I found in /var/log/auth.log there is the following message:
userauth_pubkey: signature algorithm ssh-rsa not in PubkeyAcceptedAlgorithms [preauth]
Oct 30 20:22:47 lion sshd[2607145]: Connection closed by authenticating user <me> <source-address> port 63945 [preauth]

And strange things here are:
- that the public key is ssh-rsa and that public key is in the related user field, and it does to a certain extend work (see below)
- using another ssh-client (BitVise) using the same key pair, with the same ssh-rsa key defined in the NAS, is simply working
- replacing the pubkey in the nas field with was in openssh-format by the same key in ssh2-format does not solve the problem
- replacing the backup-tool (SyncBackProV10) with the brand new SyncBackProV11 did not solve the problem

Of course I will also contact the SyncBackPro firm, but the NAS behavoir is strange and the error message as well
(the problem message seems not to match the problem !?)

So if someone understands the problem, that would help to overcome or to fix the problem

 

[Louis2]

I did some further testing and I did also contact 2BrightSparks the manufacturer of SyncBackPro.

The actual results of my testing are:
- Actual SyncBackProV10 release does have an issue in combination with the TrueNas Cobra release
- The Actual SyncBackProV11 release has the same issue when using ^WeOnlyDo^ ftp-engine
- However the other provided ftp-engine options can connect to TrueNas Cobra
- However for unknown reason the transfer speed and error rates are surely not optimal.

I did report about this to 2BrightSparks.

Let me end saying that in general, I like SyncBackPro very much

 

[somethingweird]

Most likely your using an outdated algorithm - you could either update your ssh client or add "PubkeyAcceptedAlgorithms +ssh-rsa" to the ssh server.