【初期設定】sshdを設定する

セキュリティの基本的なことですがメモがてら記載

設定内容

最低限下記の設定はしておく

• rootでのログインを禁止する
• パスワード認証を禁止する
• パスワードなし認証を禁止する

sshd_config

# cat /etc/ssh/sshd_config

-------------------
	$OpenBSD: sshd_config,v 1.93 2014/01/10 05:59:19 djm 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
#
# Port 22　　　⬅コメントアウト解除、ポートを20022に変更
# AddressFamily any
# ListenAddress 0.0.0.0
# ListenAddress ::

# The default requires explicit activation of protocol 1
# Protocol 2 　⬅コメントアウト解除

# HostKey for protocol version 1
# HostKey /etc/ssh/ssh_host_key
# 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

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

# Ciphers and keying
# RekeyLimit default none

# Logging
# obsoletes QuietMode and FascistLogging
# SyslogFacility AUTH
SyslogFacility AUTHPRIV
# LogLevel INFO

# Authentication:

# LoginGraceTime 2m　⬅コメントアウト解除、制限時間20秒（2m → 20）に変更
# PermitRootLogin yes　⬅コメントアウト解除、noに変更
# StrictModes yes　⬅コメントアウト解除
# MaxAuthTries 6　⬅コメントアウト解除、6 → 1に変更 
# MaxSessions 10　⬅コメントアウト解除

# RSAAuthentication yes　⬅コメントアウト解除
# PubkeyAuthentication yes　⬅コメントアウト解除

# 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

# AuthorizedPrincipalsFile none

# AuthorizedKeysCommand none
# AuthorizedKeysCommandUser nobody

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

# To disable tunneled clear text passwords, change to no here!
# PasswordAuthentication yes ⬅コメントアウト解除,noに変更
# PermitEmptyPasswords no ⬅コメントアウト解除
PasswordAuthentication yes

# Change to no to disable s/key passwords
# ChallengeResponseAuthentication yes
ChallengeResponseAuthentication no

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

# GSSAPI options
GSSAPIAuthentication yes
GSSAPICleanupCredentials no
# 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

# AllowAgentForwarding yes
# AllowTcpForwarding yes
# GatewayPorts no
X11Forwarding yes
# X11DisplayOffset 10
# X11UseLocalhost yes
# PermitTTY yes
# PrintMotd yes
# PrintLastLog yes
# TCPKeepAlive yes
# UseLogin no
UsePrivilegeSeparation sandbox		# Default for new installations.
# PermitUserEnvironment no
# Compression delayed
# ClientAliveInterval 0
# ClientAliveCountMax 3
# ShowPatchLevel no
# UseDNS yes
# PidFile /var/run/sshd.pid
# MaxStartups 10:30:100
# PermitTunnel no
# ChrootDirectory none
# VersionAddendum none

# no default banner path
# Banner none

# 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

# Example of overriding settings on a per-user basis
# Match User anoncvs
#	X11Forwarding no
#	AllowTcpForwarding no
#	PermitTTY no
#	ForceCommand cvs server