When I use dropbear client, it causes a duplicate public key check on the openssh server. Is there any way of preventing this separate [preauth] check from happening? For my application it is very useful to have the authentication attempted just once.
A StackExchange comment (dave_thompson_085 on https://superuser.com/q/1116927 ) to a different SSH question notes that > The [preauth] on those log lines and the Postponed result (both) mean > the client sent authreq with method=publickey and boolean=FALSE to "query" > whether the pubkey "would be acceptable" (see rfc4252 section 7). This matches what I see in the OpenSSH logs below. I checked and do not see this [preauth] when I do the same connection from an OpenSSH client. Mike I am connecting from my router using dropbear. The command I use is ssh -i .ssh/id_rsa fast@cat On the OpenSSH server I see: Feb 19 15:41:09 cat sshd[17906]: Accepted key RSA SHA256:iJN19jufdHFey0pwLK70PqgV3rgT99iQaWVmY7M8qZ0 found at /home/fast/.ssh/authorized_keys:16 Feb 19 15:41:09 cat sshd[17906]: Postponed publickey for fast from 45.78.113.202 port 48930 ssh2 [preauth] Feb 19 15:41:09 cat sshd[17906]: Accepted key RSA SHA256:iJN19jufdHFey0pwLK70PqgV3rgT99iQaWVmY7M8qZ0 found at /home/fast/.ssh/authorized_keys:16 Feb 19 15:41:09 cat sshd[17906]: Accepted publickey for fast from 45.78.113.202 port 48930 ssh2: RSA SHA256:iJN19jufdHFey0pwLK70PqgV3rgT99iQaWVmY7M8qZ0 Feb 19 15:41:09 cat sshd[17906]: pam_unix(sshd:session): session opened for user fast by (uid=0)