SSH Error – Receive Packet Type 51 on Rocky Linux 8

If you are having SSH issues and if you turned on high verbosity and the following output is generated

# ssh -vvv XXX.XXX.XXX.XXX

.....
.....
debug1: Offering public key: debug3: send packet: type 50
debug2: we sent a publickey packet, wait for reply
debug3: receive packet: type 51
.....
.....
debug2: we did not send a packet, disable method
debug1: No more authentication methods to try.
user1@192.168.0.1: Permission denied (publickey,gssapi-with-mic,password)

According to SSH protocol (RFC 4252), these are the general authentication message codes

SSH_MSG_USERAUTH_REQUEST            50
SSH_MSG_USERAUTH_FAILURE            51
SSH_MSG_USERAUTH_SUCCESS            52
SSH_MSG_USERAUTH_BANNER             53

It means that the authentiation methods mentioned in the “Permission Denied” was not accepted. What are some of the common issues.

Type 1 (Most Common Mistake): Permission Errors on the .ssh Folder and files inside .ssh

• For more information, see Encountering SSH “Permission denied, please try again.”

Type 2: Incorrect Configuration Settings on the /etc/ssh/sshd_config
(Assuming you are using Password Authentication) Inside /etc/ssh/sshd_config, you should have something like

PermitRootLogin no
.....
PasswordAuthentication yes
.....
ChallengeResponseAuthentication no
.....
GSSAPIAuthentication yes
GSSAPICleanupCredentials no
.....
UsePAM yes

Type 2: Incorrect Configuration Settings on the /etc/ssh/ssh_config
In Rocky Linux 8, everything should be commented except the last line “Include /etc/ssh/ssh_config.d/*.conf”

References:

1. How to Fix SSH Failed Permission Denied (publickey,gssapi-keyex,gssapi-with-mic)
2. ssh receive packet: type 51