自 OpenSSH 5.4 以来，有一个名为 natcat 模式的新功能，它允许您将本地 SSH 客户端绑定STDIN到STDOUT可通过远程 SSH 服务器访问的 TCP 端口。只需调用即可启用此模式ssh -W [HOST]:[PORT]
理论上，这应该非常适合在每个主机 SSH 配置中使用ProxyCommand，以前经常与nc(netcat) 命令一起使用。ProxyCommand允许您将一台机器配置为本地机器和目标 SSH 服务器之间的代理，例如，如果目标 SSH 服务器隐藏在防火墙后面。
现在的问题是，它不但不能正常工作，反而向我抛出了一条神秘的错误信息：
Bad packet length 1397966893.
Disconnecting: Packet corrupt
以下是我的摘录~/.ssh/config：
Host *
Protocol 2
ControlMaster auto
ControlPath ~/.ssh/cm_socket/%r@%h:%p
ControlPersist 4h
Host proxy-host proxy-host.my-domain.tld
HostName proxy-host.my-domain.tld
ForwardAgent yes
Host target-server target-server.my-domain.tld
HostName target-server.my-domain.tld
ProxyCommand ssh -W %h:%p proxy-host
ForwardAgent yes
正如您在此处看到的，我正在使用 ControlMaster 功能，因此我不必在每个主机上打开多个 SSH 连接。
我用来测试的客户端机器是 Ubuntu 11.10 (x86_64)，代理主机和目标服务器都是 Debian Wheezy Beta 3 (x86_64) 机器。
当我调用时会发生错误ssh target-server。当我使用标志调用它时-vvv，我还会得到以下结果：
OpenSSH_5.8p1 Debian-7ubuntu1, OpenSSL 1.0.0e 6 Sep 2011
debug1: Reading configuration data /home/aef/.ssh/config
debug1: Applying options for *
debug1: Applying options for target-server.my-domain.tld
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug1: Applying options for target-server.my-domain.tld
debug1: auto-mux: Trying existing master
debug1: Control socket "/home/aef/.ssh/cm_socket/[email protected]:22" does not exist
debug2: ssh_connect: needpriv 0
debug1: Executing proxy command: exec ssh -W 192.0.2.195:22 gateway-host.my-domain.tld
debug1: identity file /home/aef/.ssh/id_rsa type -1
debug1: identity file /home/aef/.ssh/id_rsa-cert type -1
debug1: identity file /home/aef/.ssh/id_dsa type -1
debug1: identity file /home/aef/.ssh/id_dsa-cert type -1
debug1: identity file /home/aef/.ssh/id_ecdsa type -1
debug1: identity file /home/aef/.ssh/id_ecdsa-cert type -1
debug1: permanently_drop_suid: 1000
Host key fingerprint is 1a:2b:3c:4d:5e:6f:7a:8b:9c:ad:be:cf:de:ed:fe:ef
+--[ECDSA 521]---+
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+-----------------+
debug1: Remote protocol version 2.0, remote software version OpenSSH_6.0p1 Debian-3
debug1: match: OpenSSH_6.0p1 Debian-3 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.8p1 Debian-7ubuntu1
debug2: fd 5 setting O_NONBLOCK
debug2: fd 4 setting O_NONBLOCK
debug3: load_hostkeys: loading entries for host "192.0.2.195" from file "/home/aef/.ssh/known_hosts"
debug3: load_hostkeys: loaded 0 keys
debug3: load_hostkeys: loading entries for host "192.0.2.195" from file "/etc/ssh/ssh_known_hosts"
debug3: load_hostkeys: found key type ECDSA in file /etc/ssh/ssh_known_hosts:49
debug3: load_hostkeys: found key type RSA in file /etc/ssh/ssh_known_hosts:50
debug3: load_hostkeys: loaded 2 keys
debug3: order_hostkeyalgs: prefer hostkeyalgs: [email protected],[email protected],[email protected],[email protected],[email protected],ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,ssh-rsa
debug1: SSH2_MSG_KEXINIT sent
Bad packet length 1397966893.
Disconnecting: Packet corrupt
更新：现在-vvv不只是-v输出。
答案1
我终于知道这是怎么回事了。这似乎是 OpenSSH 中的一个错误，当和 都ControlMaster启用时。不过至少有以下两种解决方法：proxy-hosttarget-server
proxy-host在尝试连接到 之前，请确保已经有一个正在运行的连接target-server。这将使错误消失，一切按预期运行。您可以通过手动连接到 来做到这一点proxy-host。禁用
ControlMaster类似ProxyCommand的ProxyCommand ssh -o "ControlMaster no" -W %h:%p proxy-host。这也会解决问题，但它会proxy-host为每个使用完全相同 的连接创建一个新的连接ProxyCommand。