☰

Aviso: falha no encaminhamento de porta remota para porta de escuta no Centos 6

tag-icon • tag-icon ssh centos-6 ssh-tunnel
Aviso: falha no encaminhamento de porta remota para porta de escuta no Centos 6

Estou com um problema com encaminhamento de porta no centos 6, quando faço:

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

Recebo este aviso:

Warning: remote port forwarding failed for listen port 19999

A sessão ssh é iniciada, mas não consigo usá-la como túnel, a saída completa é esta:

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

durante a conexão eu entro em /var/log/secure as mensagens:

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

Posso fazer o mesmo comando de outro pc com ubuntu e funciona perfeitamente, e tenho certeza que a porta 19999 é gratuita. O que posso fazer?

Responder1

Tente omitir a parte "root@" do -Rargumento:

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

Com a versão de quatro parâmetros do -R, os quatro parâmetros são o endereço e a porta para escutar conexões no host remoto e o endereço e a porta para encaminhamento do host local.

Você está fornecendo um valor de "root@hostname" como host/endereço de ligação remota. Este valor deve ser apenas um nome de host ou endereço IP; sshnão espera que esse valor inclua um nome de usuário. sshprovavelmente está tentando procurar a string inteira "root@hostname" como um nome de host e falhando.

Responder2

Eu estava lutando com esse mesmo problema no RHEL7, mas adicionalmente complicado porque o usuário ao qual eu estava me conectando era um SElinux confinado como "user_u". O audit.log estava registrando estes:

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

mas sempre demoro um pouco antes de descobrir que deveria procurar lá :-)

Para corrigir isso, tive que usar uma porta no intervalo ephemeral_port_t.

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

informação relacionada