2011-09-26

在 ubuntu server 安裝與設定 SSH

SSHSecure SHell Protocol
  1. 安裝的指令:apt-get install ssh
    在執行上述指令時,以下套件(package),也會一並安裝:libwrap0, openssh-server, ssh-import-id, tcpd...
  2. 調整設定: vi /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    #預設的port,可以修改調整
    # 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
    #Privilege Separation is turned on for security
    UsePrivilegeSeparation yes

    # Lifetime and size of ephemeral version 1 server key
    KeyRegenerationInterval 3600
    ServerKeyBits 768

    # Logging
    SyslogFacility AUTH
    LogLevel INFO

    # Authentication:
    LoginGraceTime 120
    PermitRootLogin yes    #允許root直接登入,風險太高了,把yes改為no
    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

    #再增加AllowUsers 限制可以SSH登入的使用者
    AllowUsers useraccount
  3. 重新啟動SSHD
    /etc/init.d/ssh restart
  4. 除了上述限制root登入,指定可登入的使用者外,還可以使用TCP wrapper的機制,透過/etc/hosts.allow 或 /etc/hosts.deny的設定檔,來指定可以用sshd服務的來源IP,或限制哪些IP不允許使用sshd服務。

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