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警告：Centos 6 上的监听端口远程端口转发失败

tag-icon • tag-icon ssh centos-6 ssh-tunnel
警告：Centos 6 上的监听端口远程端口转发失败

我在 centos 6 中使用端口转发时遇到问题，当我执行以下操作时：

ssh -v -R root@hostname:19999:localhost:22 root@hotname

我收到此警告：

Warning: remote port forwarding failed for listen port 19999

ssh 会话启动了，但我无法将其用作隧道，完整的输出如下：

OpenSSH_5.3p1, OpenSSL 1.0.1e-fips 11 Feb 2013
debug1: Reading configuration data /etc/ssh/ssh_config
debug1: Applying options for *
debug1: Connecting to hostname [ip.ip.ip.ip] port 22.
debug1: Connection established.
debug1: permanently_set_uid: 0/0
debug1: identity file /root/.ssh/identity type -1
debug1: identity file /root/.ssh/identity-cert type -1
debug1: identity file /root/.ssh/id_rsa type -1
debug1: identity file /root/.ssh/id_rsa-cert type -1
debug1: identity file /root/.ssh/id_dsa type -1
debug1: identity file /root/.ssh/id_dsa-cert type -1
debug1: Remote protocol version 2.0, remote software version OpenSSH_5.3
debug1: match: OpenSSH_5.3 pat OpenSSH*
debug1: Enabling compatibility mode for protocol 2.0
debug1: Local version string SSH-2.0-OpenSSH_5.3
debug1: SSH2_MSG_KEXINIT sent
debug1: SSH2_MSG_KEXINIT received
debug1: kex: server->client aes128-ctr hmac-md5 none
debug1: kex: client->server aes128-ctr hmac-md5 none
debug1: SSH2_MSG_KEX_DH_GEX_REQUEST(1024<1024<8192) sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_GROUP
debug1: SSH2_MSG_KEX_DH_GEX_INIT sent
debug1: expecting SSH2_MSG_KEX_DH_GEX_REPLY
debug1: Host 'hostname' is known and matches the RSA host key.
debug1: Found key in /root/.ssh/known_hosts:2
debug1: ssh_rsa_verify: signature correct
debug1: SSH2_MSG_NEWKEYS sent
debug1: expecting SSH2_MSG_NEWKEYS
debug1: SSH2_MSG_NEWKEYS received
debug1: SSH2_MSG_SERVICE_REQUEST sent
debug1: SSH2_MSG_SERVICE_ACCEPT received
debug1: Authentications that can continue: publickey,gssapi-keyex,gssapi-with-mic,password
debug1: Next authentication method: gssapi-keyex
debug1: No valid Key exchange context
debug1: Next authentication method: gssapi-with-mic
debug1: Unspecified GSS failure.  Minor code may provide more information
Credentials cache file '/tmp/krb5cc_0' not found

debug1: Unspecified GSS failure.  Minor code may provide more information
Credentials cache file '/tmp/krb5cc_0' not found

debug1: Unspecified GSS failure.  Minor code may provide more information


debug1: Unspecified GSS failure.  Minor code may provide more information
Credentials cache file '/tmp/krb5cc_0' not found

debug1: Next authentication method: publickey
debug1: Trying private key: /root/.ssh/identity
debug1: Trying private key: /root/.ssh/id_rsa
debug1: Trying private key: /root/.ssh/id_dsa
debug1: Next authentication method: password
hostname's password: 
debug1: Authentication succeeded (password).
debug1: Remote connections from root@hostname:19999 forwarded to local address localhost:22
debug1: channel 0: new [client-session]
debug1: Requesting [email protected]

debug1: Entering interactive session.
debug1: remote forward failure for: listen 19999, connect localhost:22
Warning: remote port forwarding failed for listen port 19999
debug1: All remote forwarding requests processed
debug1: Sending environment.
debug1: Sending env LANG = en_US.UTF-8
Last login: Sun Jul 21 17:24:54 2013 from 172.16.63.56

在连接期间我收到 /var/log/secure 消息：

Jul 21 18:30:09 localhost sshd[11816]: Accepted password for root from 172.16.63.56 port 52035 ssh2
Jul 21 18:30:09 localhost sshd[11816]: pam_unix(sshd:session): session opened for user root by (uid=0)
Jul 21 18:30:09 localhost sshd[11816]: error: channel_setup_fwd_listener: getaddrinfo(root@hostname): Name or service not known

我可以从另一台装有 ubuntu 的电脑上执行相同的命令，并且运行正常，而且我确信端口 19999 是空闲的。我该怎么办？

答案1

尝试去掉参数中的“root@”部分-R：

ssh -v -R hostname:19999:localhost:22 root@hostname

使用四参数版本的-R，四个参数分别是在远程主机上监听连接的地址和端口，以及从本地主机转发到的地址和端口。

您指定“root@hostname”作为远程绑定主机/地址。此值应仅为主机名或 IP 地址；ssh不期望此值包含用户名。ssh可能正在尝试查找整个字符串“root@hostname”作为主机名，但失败了。

答案2

我在 RHEL7 上也遇到了同样的问题，但更复杂的是，我连接的用户是 SElinux，被限制为“user_u”。audit.log 记录了以下内容：

23. 12/09/2015 12:24:40 sshd user_u:user_r:user_t:s0 49 tcp_socket name_bind system_u:object_r:unreserved_port_t:s0 denied 8595602
24. 12/09/2015 12:24:40 sshd user_u:user_r:user_t:s0 49 tcp_socket name_bind system_u:object_r:unreserved_port_t:s0 denied 8595603

但我总是要花一段时间才能弄清楚我应该去那里看:-)

为了解决这个问题，我必须使用 ephemeral_port_t 范围内的端口。

SELinux Port Type              Proto    Port Number
ephemeral_port_t               tcp      32768-61000
ephemeral_port_t               udp      32768-61000

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