sshd_config配置文件详解

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原文链接：https://blog.csdn.net/u014721096/article/details/78559506

ssh是linux远程登录的安全协议，是 C/S 模式的架构，配置文件分为服务器端配置文件 [/etc/ssh/sshd_config] 与客户端配置文件默认配置文件[/etc/ssh/ssh_config] 用户配置文件[~/.ssh/config]

sshd_config 是服务端主配置文件。这个文件的宿主应当是root，权限最大可以是”644”

# $OpenBSD: sshd_config,v 1.100 2016/08/15 12:32:04 naddy Exp $

# This is the sshd server system-wide configuration file. See
# sshd_config(5) for more information.

# This sshd was compiled with PATH=/usr/local/bin:/usr/bin

# 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.

# If you want to change the port on a SELinux system, you have to tell
# SELinux about this change.
# semanage port -a -t ssh_port_t -p tcp #PORTNUMBER <==在开启selinux的系统上，修改ssh端口的要修改selinux规则，用此命令修改
#
#Port 22 <==默认ssh端口，生产环境中建议改成五位数的端口
#AddressFamily any <==地址家族，any表示同时监听ipv4和ipv6地址
#ListenAddress 0.0.0.0 <==监听本机所有ipv4地址
#ListenAddress :: <==监听本机所有ipv6地址
HostKey /etc/ssh/ssh_host_rsa_key <==ssh所使用的RSA私钥路径
#HostKey /etc/ssh/ssh_host_dsa_key
HostKey /etc/ssh/ssh_host_ecdsa_key <==ssh所使用的ECDSA私钥路径
HostKey /etc/ssh/ssh_host_ed25519_key <==ssh所使用的ED25519私钥路径

# Ciphers and keying
#RekeyLimit default none

# Logging
#SyslogFacility AUTH
SyslogFacility AUTHPRIV <==设定在记录来自sshd的消息的时候，是否给出“facility code”
#LogLevel INFO <==日志记录级别，默认为info

# Authentication:

#LoginGraceTime 2m <==限定用户认证时间为2min
#PermitRootLogin yes <==是否允许root账户ssh登录，生产环境中建议改成no，使用普通账户ssh登录
#StrictModes yes <==设置ssh在接收登录请求之前是否检查用户根目录和rhosts文件的权限和所有权，建议开启
#MaxAuthTries 6 <==指定每个连接最大允许的认证次数。默认值是 6
#MaxSessions 10 <==最大允许保持多少个连接。默认值是 10

#PubkeyAuthentication yes <==是否开启公钥验证

# The default is to check both .ssh/authorized_keys and .ssh/authorized_keys2
# but this is overridden so installations will only check .ssh/authorized_keys
AuthorizedKeysFile .ssh/authorized_keys <==公钥验证文件路径

#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 <==指定服务器在使用 ~/.shosts ~/.rhosts /etc/hosts.equiv 进行远程主机名匹配时，是否进行反向域名查询
#IgnoreUserKnownHosts no <==是否在 RhostsRSAAuthentication 或 HostbasedAuthentication 过程中忽略用户的 ~/.ssh/known_hosts 文件
# Don't read the user's ~/.rhosts and ~/.shosts files
#IgnoreRhosts yes <==是否在 RhostsRSAAuthentication 或 HostbasedAuthentication 过程中忽略 .rhosts 和 .shosts 文件

# To disable tunneled clear text passwords, change to no here!
#PasswordAuthentication yes
#PermitEmptyPasswords no <==是否允许空密码
PasswordAuthentication yes <==是否允许密码验证，生产环境中建议改成no，只用密钥登录

# Change to no to disable s/key passwords
#ChallengeResponseAuthentication yes
ChallengeResponseAuthentication no <==是否允许质疑-应答(challenge-response)认证

# Kerberos options
#KerberosAuthentication no <==是否使用Kerberos认证
#KerberosOrLocalPasswd yes <==如果 Kerberos 密码认证失败，那么该密码还将要通过其它的认证机制(比如 /etc/passwd)
#KerberosTicketCleanup yes <==是否在用户退出登录后自动销毁用户的 ticket
#KerberosGetAFSToken no <==如果使用了AFS并且该用户有一个 Kerberos 5 TGT，那么开启该指令后，将会在访问用户的家目录前尝试获取一个AFS token
#KerberosUseKuserok yes

# GSSAPI options
GSSAPIAuthentication yes <==是否允许基于GSSAPI的用户认证
GSSAPICleanupCredentials no <==是否在用户退出登录后自动销毁用户凭证缓存
#GSSAPIStrictAcceptorCheck yes
#GSSAPIKeyExchange no
#GSSAPIEnablek5users 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'.
# WARNING: 'UsePAM no' is not supported in Red Hat Enterprise Linux and may cause several
# problems.
UsePAM yes <==是否通过PAM验证

#AllowAgentForwarding yes
#AllowTcpForwarding yes
#GatewayPorts no <==是否允许远程主机连接本地的转发端口
X11Forwarding yes <==是否允许X11转发
#X11DisplayOffset 10 <==指定sshd（8）X11转发的第一个可用的显示区(display)数字。默认值是10
#X11UseLocalhost yes <==是否应当将X11转发服务器绑定到本地loopback地址
#PermitTTY yes
#PrintMotd yes <==指定sshd(8)是否在每一次交互式登录时打印 /etc/motd 文件的内容
#PrintLastLog yes <==指定sshd(8)是否在每一次交互式登录时打印最后一位用户的登录时间
#TCPKeepAlive yes <==指定系统是否向客户端发送 TCP keepalive 消息
#UseLogin no <==是否在交互式会话的登录过程中使用 login（1）
#UsePrivilegeSeparation sandbox <==是否让 sshd(8) 通过创建非特权子进程处理接入请求的方法来进行权限分离
#PermitUserEnvironment no <==指定是否允许sshd(8)处理~/.ssh/environment以及 ~/.ssh/authorized_keys中的 environment= 选项
#Compression delayed <==是否对通信数据进行加密，还是延迟到认证成功之后再对通信数据加密
#ClientAliveInterval 0 <==sshd(8)长时间没有收到客户端的任何数据，不发送"alive"消息
#ClientAliveCountMax 3 <==sshd(8)在未收到任何客户端回应前最多允许发送多个"alive"消息，默认值是 3
#ShowPatchLevel no
#UseDNS no <==是否使用dns反向解析
#PidFile /var/run/sshd.pid <==指定存放SSH守护进程的进程号的路径
#MaxStartups 10:30:100 <==最大允许保持多少个未认证的连接
#PermitTunnel no <==是否允许tun(4)设备转发
#ChrootDirectory none
#VersionAddendum none

# no default banner path
#Banner none <==将这个指令指定的文件中的内容在用户进行认证前显示给远程用户，默认什么内容也不显示，"none"表示禁用这个特性

# Accept locale-related environment variables
AcceptEnv LANG LC_CTYPE LC_NUMERIC LC_TIME LC_COLLATE LC_MONETARY LC_MESSAGES
AcceptEnv LC_PAPER LC_NAME LC_ADDRESS LC_TELEPHONE LC_MEASUREMENT
AcceptEnv LC_IDENTIFICATION LC_ALL LANGUAGE
AcceptEnv XMODIFIERS

# override default of no subsystems
Subsystem sftp /usr/libexec/openssh/sftp-server <==配置一个外部子系统sftp及其路径

# Example of overriding settings on a per-user basis
#Match User anoncvs <==引入一个条件块。块的结尾标志是另一个 Match 指令或者文件结尾
# X11Forwarding no
# AllowTcpForwarding no
# PermitTTY no
# ForceCommand cvs server