1.) Linux Debian based configuration files are used. (OpenSSH_5.5p1 Debian-6+squeeze5)
SSH Server :
1.) Update the /etc/init.d/ssh file to include debug option.
#diff /etc/init.d/ssh
/etc/init.d/ssh.orig
30d29
< SSHD_OPTS="$SSHD_OPTS
-ddd"
#
2.) Start the ssh services in the server.
# service ssh --full-restart
Stopping OpenBSD
Secure Shell server: sshd.
Starting OpenBSD
Secure Shell server: sshddebug1: sshd version OpenSSH_5.5p1 Debian-6+squeeze5
debug1: read PEM
private key done: type RSA
debug1: Checking
blacklist file /usr/share/ssh/blacklist.RSA-2048
debug1: Checking
blacklist file /etc/ssh/blacklist.RSA-2048
debug1: private host
key: #0 type 1 RSA
debug1: read PEM
private key done: type DSA
debug1: Checking
blacklist file /usr/share/ssh/blacklist.DSA-1024
debug1: Checking
blacklist file /etc/ssh/blacklist.DSA-1024
debug1: private host
key: #1 type 2 DSA
debug1:
rexec_argv[0]='/usr/sbin/sshd'
debug1:
rexec_argv[1]='-d'
.....
.....
2.) Start the ssh client with verbose options enabled.
$ ssh -vvv USERNAME@SERVER_IP_ADDRESS
OpenSSH_5.5p1
Debian-6+squeeze5, OpenSSL 0.9.8zc 15 Oct 2014
debug1: Reading
configuration data /etc/ssh/ssh_config
debug1: Applying
options for *
debug2: ssh_connect:
needpriv 0
debug1: Connecting
to SERVER_IP_ADDRESS port 22.
debug1: Connection
established.
debug1: identity
file /h/palsarav/.ssh/id_rsa type -1
debug1: identity
file /h/palsarav/.ssh/id_rsa-cert type -1
debug1: identity
file /h/palsarav/.ssh/id_dsa type -1
debug1: identity
file /h/palsarav/.ssh/id_dsa-cert type -1
debug1: Remote
protocol version 2.0, remote software version OpenSSH_5.5p1 Debian-6+squeeze5
debug1: match:
OpenSSH_5.5p1 Debian-6+squeeze5 pat OpenSSH*
debug1: Enabling
compatibility mode for protocol 2.0
debug1: Local
version string SSH-2.0-OpenSSH_5.5p1 Debian-6+squeeze5
debug2: fd 3 setting
O_NONBLOCK
debug1:
SSH2_MSG_KEXINIT sent
debug1:
SSH2_MSG_KEXINIT received
debug2:
kex_parse_kexinit:
diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
debug2:
kex_parse_kexinit:
ssh-rsa-cert-v00@openssh.com,ssh-dss-cert-v00@openssh.com,ssh-rsa,ssh-dss
Reference :
1.)
sshd(8) - Linux man page
Synopsis
sshd [-46DdeiqTt]
[-b bits]
[-C connection_spec]
[-f config_file]
[-g login_grace_time]
[-h host_key_file]
[-k key_gen_time]
[-o option]
[-p port]
[-u len]
sshd (OpenSSH Daemon) is the daemon program for
ssh(1).
Together these programs replace rlogin(1) and rsh(1),
and provide secure encrypted communications between two untrusted hosts over an
insecure network.
sshd listens for connections from clients. It is normally started at boot from /etc/rc. It
forks a new daemon for each incoming connection. The forked daemons handle key exchange, encryption,
authentication, command execution, and data exchange.
-d'
|
Debug mode. The server sends verbose debug
output to the system log, and does not put itself in the background. The
server also will not fork and will only process one connection. This option
is only intended for debugging for the server. Multiple -d options increase the debugging level.
Maximum is 3.
|
2.)
SSH(1) BSD General Commands Manual SSH(1)
NAME
ssh â OpenSSH SSH client (remote login program)
SYNOPSIS
ssh [-1246AaCfgKkMNnqsTtVvXxYy] [-b bind_address] [-c cipher_spec] [-D [bind_address:]port] [-e escape_char] [-F configfile] [-I pkcs11]
[-i identity_file] [-L [bind_address:]port:host:hostport] [-l login_name] [-m mac_spec] [-O ctl_cmd] [-o option] [-p port] [-R
[bind_address:]port:host:hostport] [-S ctl_path] [-W host:port] [-w local_tun[:remote_tun]] [user@]hostname [command]
-v Verbose mode. Causes ssh to print debugging messages about its progress. This is helpful in debugging connection, authentication, and configuraâ
tion problems. Multiple -v options increase the verbosity. The maximum is 3.
NAME
ssh â OpenSSH SSH client (remote login program)
SYNOPSIS
ssh [-1246AaCfgKkMNnqsTtVvXxYy] [-b bind_address] [-c cipher_spec] [-D [bind_address:]port] [-e escape_char] [-F configfile] [-I pkcs11]
[-i identity_file] [-L [bind_address:]port:host:hostport] [-l login_name] [-m mac_spec] [-O ctl_cmd] [-o option] [-p port] [-R
[bind_address:]port:host:hostport] [-S ctl_path] [-W host:port] [-w local_tun[:remote_tun]] [user@]hostname [command]
-v Verbose mode. Causes ssh to print debugging messages about its progress. This is helpful in debugging connection, authentication, and configuraâ
tion problems. Multiple -v options increase the verbosity. The maximum is 3.
