Ubuntu ssh配置

參考

Ubuntu16.04 搭建ssh
Ubuntu配置SSH服務器
SSH Client連接Ubuntu Server失敗解法
ssh安全優化

方法

使用命令sudo apt install openssh-server只安裝服務器時，報錯Package ssh-server is a virtual package provided by...，提示讓你確認選擇安裝哪一個包，使用命令sudo apt install ssh就成功安裝了，且同時把服務器和客戶端都安裝了，記住版本號1:7.2p2-4ubuntu2.8，下次可以僅安裝服務端。

qe@ubuntu:~$ sudo apt install ssh
Reading package lists... Done
Building dependency tree       
Reading state information... Done
ssh is already the newest version (1:7.2p2-4ubuntu2.8).
0 upgraded, 0 newly installed, 0 to remove and 320 not upgraded.
qe@ubuntu:~$ 
qe@ubuntu:~$ 
qe@ubuntu:~$ sudo apt install openssh-server
Reading package lists... Done
Building dependency tree       
Reading state information... Done
openssh-server is already the newest version (1:7.2p2-4ubuntu2.8).
openssh-server set to manually installed.
0 upgraded, 0 newly installed, 0 to remove and 320 not upgraded.

安裝完啓動，

$ sudo service ssh start  #啓動ssh
$ sudo service ssh stop   #關閉ssh
$ sudo service ssh restart  #重啓ssh

ssh配置文件/etc/ssh/sshd_config，允許root登錄，把PermitRootLogin prohibit-password換成PermitRootLogin yes

qe@ubuntu:~$ cat /etc/ssh/sshd_config
# Package generated configuration file
# See the sshd_config(5) manpage for details

# What ports, IPs and protocols we listen for
Port 22
# Use these options to restrict which interfaces/protocols sshd will bind to
#ListenAddress ::
#ListenAddress 0.0.0.0
Protocol 2
# HostKeys for protocol version 2
HostKey /etc/ssh/ssh_host_rsa_key
HostKey /etc/ssh/ssh_host_dsa_key
HostKey /etc/ssh/ssh_host_ecdsa_key
HostKey /etc/ssh/ssh_host_ed25519_key
#Privilege Separation is turned on for security
UsePrivilegeSeparation yes

# Lifetime and size of ephemeral version 1 server key
KeyRegenerationInterval 3600
ServerKeyBits 1024

# Logging
SyslogFacility AUTH
LogLevel INFO

# Authentication:
LoginGraceTime 120
PermitRootLogin prohibit-password
StrictModes yes

RSAAuthentication yes
PubkeyAuthentication yes
#AuthorizedKeysFile	%h/.ssh/authorized_keys

# Don't read the user's ~/.rhosts and ~/.shosts files
IgnoreRhosts yes
# For this to work you will also need host keys in /etc/ssh_known_hosts
RhostsRSAAuthentication no
# similar for protocol version 2
HostbasedAuthentication no
# Uncomment if you don't trust ~/.ssh/known_hosts for RhostsRSAAuthentication
#IgnoreUserKnownHosts yes

# To enable empty passwords, change to yes (NOT RECOMMENDED)
PermitEmptyPasswords no

# Change to yes to enable challenge-response passwords (beware issues with
# some PAM modules and threads)
ChallengeResponseAuthentication no

# Change to no to disable tunnelled clear text passwords
#PasswordAuthentication yes

# Kerberos options
#KerberosAuthentication no
#KerberosGetAFSToken no
#KerberosOrLocalPasswd yes
#KerberosTicketCleanup yes

# GSSAPI options
#GSSAPIAuthentication no
#GSSAPICleanupCredentials yes

X11Forwarding yes
X11DisplayOffset 10
PrintMotd no
PrintLastLog yes
TCPKeepAlive yes
#UseLogin no

#MaxStartups 10:30:60
#Banner /etc/issue.net

# Allow client to pass locale environment variables
AcceptEnv LANG LC_*

Subsystem sftp /usr/lib/openssh/sftp-server

# 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

在最後方添加Ciphers配置，兼容所有ssh客戶端，避免Algorithm negotiation failed，比如我的老版本SecureCRT就無法ssh登錄板卡，

Ciphers aes128-cbc,aes192-cbc,aes256-cbc,aes128-ctr,aes192-ctr,aes256-ctr,3des-cbc,arcfour128,arcfour256,arcfour,blowfish-cbc,cast128-cbc
MACs hmac-md5,hmac-sha1,[email protected],hmac-ripemd160,hmac-sha1-96,hmac-md5-96
KexAlgorithms diffie-hellman-group1-sha1,diffie-hellman-group14-sha1,diffie-hellman-group-exchange-sha1,diffie-hellman-group-exchange-sha256,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group1-sha1,[email protected]

Ciphers
指定SSH-2允許使用的加密算法。多個算法之間使用逗號分隔。可以使用的算法如下：
“aes128-cbc”, “aes192-cbc”, “aes256-cbc”, “aes128-ctr”, “aes192-ctr”, “aes256-ctr”,
“3des-cbc”, “arcfour128”, “arcfour256”, “arcfour”, “blowfish-cbc”, “cast128-cbc”
默認值是可以使用上述所有算法。

Ciphers 默認使用這些
aes128-ctr,aes192-ctr,aes256-ctr,arcfour256,arcfour128,aes128-cbc,3des-cbc
漏洞提示arcfour,arcfour128,arcfour256都是不安全的,那就刪掉
變成這樣aes128-ctr,aes192-ctr,aes256-ctr,aes128-cbc,3des-cbc