Ubuntu 20.x.x 버전에 구버전 secureCRT로 SSH 접속하는 방법

터미널 소프트웨어인 secureCRT 6.5.4를 사용하여
Ubuntu 20.04.1 LTS 버전에 ssh 접속을 시도 시
아래와 같이 에러가 발생합니다.
 

최신 Ubuntu의 ssh의 key를 제공하지 않아 접속이 되지 않습니다.
Key exchange failed. No compatible key exchange method.
The server supports these methods: curve25519-sha256,curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group14-sha256

위의 말 그대로 구버전의 secureCRT에서
최신 버전 Ubuntu의 ssh key를 제공하지
않아서 접속에 실패하게 되는데요.

해결 방법으로는 secureCRT의 버전을 업데이트!
하거나 구버전의 secureCRT에서 지원하는
SSH key를 추가해주시면 됩니다.

아래와 같은 방법으로 추가가 가능합니다.
root@pa-virtual-machine:/# vi /etc/ssh/sshd_config <-- sshd conf 수정
아래의 두줄을 맨 아래에 추가해줍니다.
KexAlgorithms +diffie-hellman-group1-sha1
Ciphers +aes128-cbc

---

root@pa-virtual-machine:/home/pa# systemctl status ssh
● ssh.service - OpenBSD Secure Shell server
Loaded: loaded (/lib/systemd/system/ssh.service; enabled; vendor preset: enabled)
Active: active (running) since Wed 2022-09-21 14:59:28 KST; 3 months 27 days ago
Docs: man:sshd(8)
man:sshd_config(5)
Main PID: 853 (sshd)
Tasks: 1 (limit: 9454)
Memory: 4.3M
CGroup: /system.slice/ssh.service
└─853 sshd: /usr/sbin/sshd -D [listener] 0 of 10-100 startups

9월 21 14:59:26 pa-virtual-machine systemd[1]: Starting OpenBSD Secure Shell server...
9월 21 14:59:28 pa-virtual-machine sshd[853]: Server listening on 0.0.0.0 port 22.
9월 21 14:59:28 pa-virtual-machine sshd[853]: Server listening on :: port 22.
9월 21 14:59:28 pa-virtual-machine systemd[1]: Started OpenBSD Secure Shell server.
9월 21 15:03:07 pa-virtual-machine sshd[2020]: Accepted password for pa from 192.168.208.56 port 11511 ssh2
9월 21 15:03:07 pa-virtual-machine sshd[2020]: pam_unix(sshd:session): session opened for user pa by (uid=0)
1월 18 13:56:10 pa-virtual-machine sshd[455386]: Accepted password for pa from 192.168.208.56 port 6602 ssh2
1월 18 13:56:10 pa-virtual-machine sshd[455386]: pam_unix(sshd:session): session opened for user pa by (uid=0)
root@pa-virtual-machine:/home/pa#
root@pa-virtual-machine:/home/pa#
root@pa-virtual-machine:/home/pa#
root@pa-virtual-machine:/home/pa# cat /etc/ssh/sshd_config
# $OpenBSD: sshd_config,v 1.103 2018/04/09 20:41:22 tj Exp $

# This is the sshd server system-wide configuration file. See
# sshd_config(5) for more information. # This sshd was compiled with PATH=/usr/bin:/bin:/usr/sbin:/sbin

# The strategy used for options in the default sshd_config shipped with
# OpenSSH is to specify options with their default value where
# possible, but leave them commented. Uncommented options override the
# default value. Include /etc/ssh/sshd_config.d/*.conf #Port 22
#AddressFamily any
#ListenAddress 0.0.0.0
#ListenAddress ::

#HostKey /etc/ssh/ssh_host_rsa_key
#HostKey /etc/ssh/ssh_host_ecdsa_key
#HostKey /etc/ssh/ssh_host_ed25519_key # Ciphers and keying
#RekeyLimit default none # Logging
#SyslogFacility AUTH
#LogLevel INFO

# Authentication:

#LoginGraceTime 2m
#PermitRootLogin prohibit-password
#StrictModes yes
#MaxAuthTries 6
#MaxSessions 10

#PubkeyAuthentication yes

# Expect .ssh/authorized_keys2 to be disregarded by default in future.
#AuthorizedKeysFile .ssh/authorized_keys .ssh/authorized_keys2

#AuthorizedPrincipalsFile none #AuthorizedKeysCommand none
#AuthorizedKeysCommandUser nobody

# For this to work you will also need host keys in /etc/ssh/ssh_known_hosts
#HostbasedAuthentication no
# Change to yes if you don't trust ~/.ssh/known_hosts for
# HostbasedAuthentication
#IgnoreUserKnownHosts no
# Don't read the user's ~/.rhosts and ~/.shosts files
#IgnoreRhosts yes # To disable tunneled clear text passwords, change to no here!
#PasswordAuthentication yes
#PermitEmptyPasswords no # Change to yes to enable challenge-response passwords (beware issues with
# some PAM modules and threads)
ChallengeResponseAuthentication no # Kerberos options
#KerberosAuthentication no
#KerberosOrLocalPasswd yes
#KerberosTicketCleanup yes
#KerberosGetAFSToken no # GSSAPI options
#GSSAPIAuthentication no
#GSSAPICleanupCredentials yes
#GSSAPIStrictAcceptorCheck yes
#GSSAPIKeyExchange no # Set this to 'yes' to enable PAM authentication, account processing,
# and session processing. If this is enabled, PAM authentication will
# be allowed through the ChallengeResponseAuthentication and
# PasswordAuthentication. Depending on your PAM configuration,
# PAM authentication via ChallengeResponseAuthentication may bypass
# the setting of "PermitRootLogin without-password".
# If you just want the PAM account and session checks to run without
# PAM authentication, then enable this but set PasswordAuthentication
# and ChallengeResponseAuthentication to 'no'.
UsePAM yes #AllowAgentForwarding yes
#AllowTcpForwarding yes
#GatewayPorts no
X11Forwarding yes
#X11DisplayOffset 10
#X11UseLocalhost yes
#PermitTTY yes
PrintMotd no
#PrintLastLog yes
#TCPKeepAlive yes
#PermitUserEnvironment no
#Compression delayed
#ClientAliveInterval 0
#ClientAliveCountMax 3
#UseDNS no
#PidFile /var/run/sshd.pid
#MaxStartups 10:30:100
#PermitTunnel no
#ChrootDirectory none
#VersionAddendum none # no default banner path
#Banner none # Allow client to pass locale environment variables
AcceptEnv LANG LC_* # override default of no subsystems
Subsystem sftp /usr/lib/openssh/sftp-server # Example of overriding settings on a per-user basis
#Match User anoncvs
# X11Forwarding no
# AllowTcpForwarding no
# PermitTTY no
# ForceCommand cvs server

<추가된 부분>
KexAlgorithms +diffie-hellman-group1-sha1
Ciphers +aes128-cbc

root@pa-virtual-machine:/home/pa#
root@pa-virtual-machine:/home/pa#