正确配置SSHD配置文件？

Question

我在我的linux上使用ssh，我希望尽可能地保护它的安全，只允许通过ed25519椭圆曲线加密sigs来实现ssh。

我以为我的设置正确，禁用密码，没有PAM，等等。

它似乎正常工作，但是今天我注意到我没有指定一个authorised_keys文件，并且PubkeyAuthentication被注释掉了。

当密码auth设置为no时，这些内容是否隐式地设置为yes？

这个装置还好吗？

#       $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.

#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 no
#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

Answer 1

我不确定，是否排除了所有的公钥算法，除了ed25519没有过分热心，它是一个很好的安全策略。安全堆栈交换当然可以告诉你更多关于这个问题的信息。

SSH默认值列在sshd_配置手册中，但最好在您的系统上读取该默认值:例如，Debian更改了一些上游默认值。PubkeyAuthentication's违约为是，而AuthorizedKeysFile's违约为~/.ssh/authorized_keys (美式拼写)。

假设您想要:禁用所有基于密码的身份验证，并且只使用ed25519公钥加密，同时考虑到上游默认设置，您只需要：

ChallengeResponseAuthentication no
#GSSAPIAuthentication no by default
#HostbasedAuthentication no by default
#KbdInteractiveAuthentication defaults to ChallengeResponseAuthentication
#KerberosAuthentication no by default
PasswordAuthentication no
#PubkeyAuthentication yes by default
PubkeyAcceptedKeyTypes ssh-ed25519
UsePAM yes

禁用 PAM 作为一个整体禁用帐户和会话PAM模块的使用，这些模块为用户提供了一个更好的环境。无论如何，都不会使用auth PAM模块，因为密码和质询响应身份验证都是禁用的。